Aaron Clinton

Source: http://jalopnik.com/2015-subaru-impreza-wrx-sti-this-is-it-1496968833

They are back, check them out here: http://store.soundso...-acoustics.html

Figured you would enjoy it.

A few years late, but we are finally getting a very nice tweeter going that is worthy of being a part of the SSA line. The pictures below show the prototypes, they are really attractive in person and will, in production form, bare the SSA logo. See the attached files for the 4 and 8 ohm versions. They are quite smooth to my ear (aka not super bright like some metal dome tweets can be) and blend well with the Evil6.5's (vital to the design). These are not a PA style, 'screamy' tweet, these are meant for sound quality first and foremost. Possible future home audio plans. Pricing is not set just yet. These will be sold as a pair. Some quick points of info: 28mm Silk Dome, Large Roll Surround Aluminum Faceplace and Housing Sound Transparent Grill Low Fs. for flexibility in both Home & Car Neo Motor with Shallow non-Resonant Chamber 61.9mm (2.44") dia. flange, 21.5mm (.85") depth 65 watts rms

We have been keeping it pretty active with some of the day to day type of things. It is also a great way to find out any little news. Link: SSA Facebook

Ok, so these are a 2" copper coil, shorting ring, solid pole, phase plug, underhung design. In final testing, they are a very very clean, warm sound. They were right at home in an IB rig that Neal helped out on big time, so dropping into an average car door is excellent. The Evil6.5's have push terminals that are good for 10 gauge wire. Nomex spiders, so they will able take the same long term abuse that the SSA subs are known for. Also, the glass fiber cones that were available, performed a little better than the poly cones in testing. I will probably be setting these at 120-150rms. Specs are below, on the bottom right. Follow the green slope for the production model. I had put together a slightly different model to see what combination of aspects were the best performing for our goals, so ignore the purple slope and specs on the left.

Check it out here: https://store.soundsolutionsaudio.com/holiday-sale/

Another great read that I felt was worth having here also: Anatomy of the Power Amplifier Dissecting the Modern Audio Power Amplifier and Power Supply By Robert Zeff With the Proliferation of Different Amp Types, Which is the One for You? In the past we had essentially two types of amplifiers to choose from: Class "AB" and class "A". Today we have AB, A, D, G, H, & T, in addition to some that do not have a class name. New technology brought down the size and price while improving performance and efficiency. We'll review the various topologies of the modern amplifier, spending extra time on the aspect of efficiency (as the quest for smaller, more efficient designs have spawned the class D, G, H, & T designs). We'll also try to dispel some of the misconceptions and folklore that seem to surround amp design. Amplifiers require circuitry for short and thermal protection, fan control, turn on delay, and over voltage protection. In the past we littered the designs with dozens of components to handle these events. Today we can use a single microprocessor to handle all of this in addition to having many more features without additional cost. The microprocessor can monitor the battery voltage, internal voltages, temperature, control volume and crossovers, and drive external displays. These embedded computer chips also allow features like compression and power limiting with little added cost. Of course, what is an amplifier without a power supply? First we'll visit the power supply designs, as every amplifier needs one. The Power Supply The purpose of the supply is to convert the auto's battery voltage to a higher voltage. For example, if an amplifier is to produce 100 watts into a 4 ohm speaker, we need 20 volts RMS. This implies that we need about +/-28 volts. (20 volts R.M.S. = 28.28 volts peak). We call that the "rail" voltage. Since the amplifier's output transistors cannot pull all the way up to this rail, we actually need a slightly higher voltage. The process is to convert the 12 volts DC into AC, feed it to a transformer and convert it back to DC again. Converting the 12 volt battery voltage to AC is simple, a PWM (pulse width modulator) IC feeds a bank of MOSFETS (MOSFETs are switching transistors perfectly suited for this task). The 12 volt power is switched at a very high frequency, somewhere between 40 and 150 kHz. Slower switching speeds require a larger transformer, but high speeds have more switching loss. Advanced transformer core materials, faster rectifiers, and clever winding methods have enabled us to utilize very high frequencies. Some of today's better amplifiers have very small power supplies that produce enormous amounts of power. Regulated Power Supplies Most early audio amplifiers contained unregulated power supplies. Regulated supplies require very high quality filter capacitors (called "low ESR" capacitors), output chokes, and an optically isolated voltage feedback circuit. Regulation occurs by controlling the switching pulse width from 0 - 100% to compensate for changes in the battery and rail voltage. The same action occurs when the audio level increases. As the amplifier draws more power from the supply, the rail voltage drops. Again, the regulator circuitry senses this drop and responds with an increased pulse width. The high frequency PWM waveform is rectified (converted to DC) and applied to the output filter choke and capacitors. This output of this circuit is the + and - DC rails that feed the power amplifier. Unregulated Power Supplies Unregulated power supplies are less expensive than regulated supplies. They do not require an output choke, voltage sense or isolation circuitry. Because the duty cycle is nearly 100%, capacitor ripple current is much lower in unregulated supplies. Lower ripple current requires less expensive capacitors throughout. Often we hear that unregulated designs have more "headroom". That means that the amplifier will produce extra power during transients. Most home audio amplifiers employ unregulated power supplies. The power supplies in these amplifiers run at 60 Hz, thus the filter capacitors must be 200-500 times larger than those used in high frequency switchers. The extra capacitance in home audio amplifiers results in extra headroom. Headroom for anything other than very short transients simply doesn't exist in the unregulated designs. The following is an example of specifications for an unregulated vs. regulated amplifiers. Unregulated designs have a higher supply voltage at low power, causing higher voltage on the output transistors. This reduces the amplifier's efficiency. Small amplifiers (less than 100 watts) cannot justify the extra cost of the regulation circuitry, so we often see unregulated supplies in these amplifiers. Pros and Cons of Regulated / Unregulated SuppliesSome designers try to keep their supplies regulated down to battery voltages as low as 9.5 volts. The supply compensates by increasing the current. The following table shows voltage and currents for a 500 watt over-regulated amplifier operating at full power. The current increases dramatically at the lower voltages. Because of higher currents at the lower voltages, the supply efficiency drops further, requiring even more current. At higher voltages, the pulse width reduces, causing increased ripple current. This high current creates heat in the filter capacitors and can destroy the capacitor's electrolyte. Some manufacturers do not use capacitors of sufficient quality for this range of regulation. These amplifiers may not perform up to specification just one year after installation. Also, the extra current at low voltages is extra hard on a battery that is already suffering! So, we recommend that amplifiers stay in regulation down to about 11 - 11.5 volts. Any properly working charging system can easily keep the battery voltage well above this. The Amplifier Section, Class AB and AClass AB and A amplifiers are similar, so we'll discuss both here. Class AB amplifiers have transistors that pull up to the positive rail and transistors that pull down to the negative rail. This corresponds to the action of pushing the speaker cone out and in. Class AB means that the output transistors do not always have current on them. For example, when the upper transistors are pulling up towards the positive rail (pushing the speaker out), there is no current in the lower transistors. When the output signal swings through zero, towards the negative rail, the output transistor must go through a transition from zero current to a non-zero current. The best analogy that I can think of is driving an old car with too much slop in the steering. As you go from one side of the road's crown to the other, the steering crosses a "dead" zone, and you tend to over-steer. Special temperature compensated bias circuitry reduces this dead zone, known as notch distortion. The figure below shows the output of a class AB amplifier with too little bias and the resulting distortion. Notch distortion increases at higher frequencies and low volume levels. Some modern designs have reduced this type of distortion to very low levels. Class A means that every transistor is always conducting current. They are very similar to class AB amplifiers, but the bias circuitry is set so that there are very high currents in the output transistors. Because these amplifiers do not have this "dead zone', less feedback is required to achieve low distortion. A 100 watt amplifier may dissipate nearly 100 watts internally even when there is no audio output. This type of design is impractical in the harsh auto environment. Many class A amplifiers pedaled for the automotive market are not really class A. They are huge power wasters in the home as well. Input and Driver Stages The amplifier works this way: A small audio signal is presented to the amplifier's input. Transistors are not linear, which means that the input signal will distort somewhat as it passes through the various amplifier stages. To correct this distortion, a portion of the output is compared with the input. The difference creates a correction signal reducing this distortion. The input stage is a special type, called "differential". It has a + and a - input because it must accept both the audio input and the input from the feedback circuitry. Excess feedback can lower distortion dramatically, but cause instability. Careful design rules must be followed to avoid this instability. The output of the input stage feeds into the driver stage. The driver stage may use one, two, or three devices. Often this circuitry is referred to "Darlington", or "Triple Darlington". The driver circuit feeds the output stage, which may have two, four, six, or more transistors. The more output transistors, the better. Multiple output devices reduce distortion (requiring less negative feedback) and improve reliability. Bipolar or MOSFET? We have seen both MOSFET (Metal Oxide Silicon Field Effect Transistor) and Bipolar transistors used in audio amplifiers. Claims have been made that each is superior. I have seen claims that MOSFETs have a tube ("Valve" for the Brits) sound. This is more folklore. The musicians and their instruments are supposed to have "the sound", not audio equipment! MOSFETs are tougher than Bipolars, and can pull closer to the supply rail. It takes more Bipolar transistors to achieve the same power as a MOSFET, therefore Bipolar amps tend to be more expensive. But, MOSFETs are very non-linear, compared to Bipolars and require much more feedback to achieve reasonable distortion numbers. They are a great choice for bass amps, as low frequency audio is not difficult for a MOSFET. The most expensive car and home amplifiers almost always use Bipolar transistors. Efficiency What makes an amplifier get hot? Both the power supply and the power amplifier generate heat. The maximum efficiency of the power supply is nearly 100%. Good power supply designs, with the highest quality components approach 85%. The class AB amplifier efficiency at full power can approach 75%. The total efficiency, including the power supply, can be about 65%. But, efficiency drops at lower power and can typically be under 20%. A class AB amplifier actually runs cooler at full power than it does at half power. Run this amplifier into clipping and it might run even cooler! Where is all this power going? The output transistor is basically a large variable resistor. If the instantaneous output voltage should be 40 volts and the power supply is 100 volts, then 60 volts must be "wasted" in the output transistors. Driving a reactive load (like a speaker) causes the efficiency to drop ever further. This brings us to the other audio classes designed to improve efficiency. Class D First, let's dispel another myth: Class D does not stand for digital. The input is converted to a two-state (binary) representation of the audio waveform. That's where the similarity ends. This distinction is important because class D doesn't provide the benefits normally associated with digital components. That being said, class D designs dramatically improve efficiency. Instead of wasting power in the output transistor, the output is switched at a very high frequency between the positive and negative supply rails. If the output is to be zero, then the waveform is at a 50% duty cycle. If the output is to be a positive voltage, then the duty cycle would be greater than 50%. Because the output devices are either completely turned on (no wasted voltage) or completely turned off, theoretically efficiency is 100%. So the audio input must be converted to a pulse width modulated waveform (PWM). The yellow trace below is the output of the amplifier; the blue trace is the PWM waveform. The blue waveform is fed to an output filter, which results in the yellow output waveform. Notice that the output looks somewhat distorted. All of the switching noise and distortion cannot be removed and the result can be seen here. Because of this process of converting the input signal to PWM and converting back to analog, a good deal of distortion is introduced. Conventional feedback like that used in class AB designs is used in these amplifiers to reduce distortion. MOSFETs are the only choice for class D designs. Most class D designs are useful only for bass amps as they can not switch fast enough to reproduce high frequencies. Some high quality, full range class D designs exist for pro audio, but they are complex with multi-phased outputs. Class T Class T (Tripath) is similar to class D with these exceptions: This class does not use analog feed back like its class D cousin. The feedback is digital and is taken ahead of the output filter, avoiding the phase shift of this filter. Because class D or T amplifier distortion arises from timing errors, the class T amplifier feeds back timing information. The other distinction is that this amplifier uses a digital signal processor to convert the analog input to a PWM signal and process the feedback information. The processor looks at the feedback information and makes timing adjustments. Because the feedback loop does not include the output filter, the class T amplifier is inherently more stable and can operate over the full audio band. Most listeners can not hear the difference between class T and good class AB designs. Both class D and T designs share one problem: they consume extra power at idle. Because the high frequency waveform is present at all times, even when there is no audio present, the amplifiers generate some residual heat. Some of these amplifiers actually turn off in the absence of music, and can be annoying if there is too much delay turning back on. Class G Class G improves efficiency in another way: an ordinary class AB amplifier is driven by a multi-rail power supply. A 500 watt amplifier might have three positive rails and three negative rails. The rail voltages might be 70 volts, 50 volts, and 25 volts. As the output of the amplifier moves close to 25 volts, the supply is switched the 50 volt rail. As the output moves close to the 50 volt rail, the supply is switched to the 70 volt rail. These designs are sometimes called "Rail Switchers". This design improves efficiency by reducing the "wasted" voltage on the output transistors. This voltage is the difference between the positive (red) supply and the audio output (blue). Class G can be as efficient as class D or T. While a class G design is more complex, it is based on a class AB amplifier and can have the same clean characteristics as well. Class H Class H is similar to class G, except the rail voltage is modulated by the input signal. The power supply rail is always just a bit higher than the output signal, keeping the voltage across the transistors small and the output transistors cool. The modulating power supply rail voltage is created by similar circuitry that you would find in a class D amplifier. In terms of complexity, this type of amplifier could be thought of as a class D amplifier driving a class AB amplifier and is therefore fairly complex. How to Choose? Regulated or unregulated? Class AB, D, or T?If you're really into a lot of bass, the class D or T may be for you as these amplifiers will produce the highest SPL with the smallest size. If you just want to wake the neighbors, blur your vision, or make a big splash in SPL contests, maybe you just need one of the inexpensive, powerful, & dirty class D designs. Want the cleanest high frequencies? Maybe a good class AB amp would be your selection. Whatever you choose, I hope this information helps you achieve the sound you're looking for! >> Click here for images and diagrams too <<

Just thought I would open this up to the regulars and get some open discussion going. Does anyone feel we need to add some sections or that the forum is lacking something in the layout? I can easily add sections to the site and move things around to best suit the likes of our member base.

Source: http://jalopnik.com/#!5779391 Why The Evo Must Die Mike Spinelli — Mitsubishi's shifting its focus away from cars with good dynamics, cheap prices and fervent motorsports-bred street cred toward an electric vehicle future. Rather than make the next Evo an electric appliance, it really should just commit Seppuku. What was the greatest moment in Mitsubishi motorsports history? Take your pick. Was it in 1996 when Tommi Mäkinen braved freak African downpours, and the mud bogs they produced, to take the Safari Rally by more than 14 minutes? Or was it later that year when the Finn won his first WRC driver's championship in the intrepid Lancer Evo III? Maybe it was in 1998 when Mäkinen and the late Richard Burns brought home the WRC manufacturers' championship, or perhaps earlier, in 1976, when a Lancer 1600 GSR swept every single one of the Safari Rally's podium places in an event only 20 percent of entrants even finished. And let's not even get started on Dakar. (Some say its greatest moment was the all-wheel-drive Mitsubishi Starion its engineers developed for Group B, only to have the class disbanded before the car could rip a Starion-sized hole in the ozone layer. That some would include me, but I'm a nerd.) Either way, Mitsubishi's greatest motorsport moment certainly wasn't in 2009, when it pulled out of WRC, or in 2010 when Ralliart, the company's motorsports-development arm, pared down its duties to practically nil. Likewise, it wasn't last week, when global product director, Gayu Eusegi, told Autocar that Mitsubishi "must stop" producing the Evo — despite continued demand — to focus on its next big bet: EV technology. You might not like it, but he's right. It was fun while it lasted, kids, but it's time to end it. Whatever you think about electric cars, or how many Evo snaps you once taped into your locker, Mitsubishi is correct to bow out of motorsports and ostensibly phase out its mo-sport halo car. Not because racing is anathema to today's car business, but because racing and building series-production cars spawned from motorsports development isn't for dabblers. These days, and in the post-carpocalyptic days to come, building fast cars with good dynamics and a price tag in the lower five-digit range is harder than ever; it demands the focus of a Jedi, Croesus's bank statement and a commitment to the practice of racing that transcends quick profits. That market, like Bette Davis once said about old age, ain't no place for sissies. As much as we'd hate to bear witness to the swan song of the Evo, a car that once — and thankfully only once — caused me to vomit with joy, I congratulate the sentiment. Mothballing a sports sedan that still enjoys unmet demand in the US market? That's balls right there, buddy. That's leadership. That's focus. It's not the kind of leadership or focus many of us would prefer, but at least Mitsubishi is signaling that it has the corporate walnuts to live entirely by a new set of convictions (and that it's part of a conglomerate that includes a huge electronics concern). Will it work? Maybe, maybe not. But who cares? When was the last time you heard an automaker channel a defiant David Glasgow Farragut and take a damn-the-torpedoes stand? It was fun while it lasted, kids, but now it's time to end it. The company's plans are as aggressive as its talk. Mitsubishi has said it will launch six new electric or plug-in hybrid vehicles and enough conventional hybrids to put Berkeley, California into a figure-four leglock by 2015. How's that for aggressive? So that's it? What of the Evo's legacy? Yes, we've watched as the top Lancer matured over ten blessed incarnations from a rough beast into a tourer with benefits. The Evo X is indeed a grown-ass car. It's 300 pounds heavier than the previous Evo IX, owing to forced parity with the newer, more demanding safety regulations. It's got eleventy side curtain air bags at the front and rear and an exploding down comforter protecting the driver's kneecaps. It has steel side girders that meet impact-safety standards for charging rhinoceroses, and enough NVH dampening to silence a Charlie Sheen podcast. By comparison, the maniac Evo IX rattled and fussed, and at top gallop sounded like a dumpster full of table saws, set upon by a gorilla in steel-toed Doc Martens. But we loved it. And if we're splitting hairs, the IX was more livable than the VIII, which was more livable than the VI, and etc. And still, the more refined X can carry even more sinister amounts of speed through a corner than its predecessor, owing to its trick yaw-control hardware, and the X's brakes can stand up to a very late stomp ahead of a corner. Plus, as dual-clutch transmissions go, I'll take the Evo X's SST over just about any other. It's as if the X is capable despite its demeanor, whereas the older Evos telegraphed their immense capability in requisite teeth-chattering ride, frantic steering and better-look-ahead quickness. While we'll miss the Evo, we'll miss parlor-gaming Evos more, contrasting the late-model's 4B11 T/C engine with the vaunted, old 4G63, bestowing on the older Evos the title of "driver's car" and complaining that the X lacks a certain soul, even while it's out on the skidpad pulling lateral Gs that would shame an Audi R8. Like it or not, and as much as we bitch about it, refinement is the price we pay for safer cars, just as arguments are the price we pay for being car nerds. The Subaru STI, Evo's staunchest rival, and just about every other performance car from the BMW M3 to the Porsche 911 has undergone a similar, well, evolution — becoming heavier, more techie and less dynamic except at the very limit. The difference between them and the Evo is this: all of those companies, despite the compromises they've had to make, continue to support racing at some level, infusing not only the technology but also the attitude of motorsports into their cars. They also sell lots of cars and make boatloads of money, something Mitsubishi's been struggling with — particularly in the US — for years. Racing intelligence is as much a part of building great performance cars as is R&D lab work. What was Mäkinen's secret back in 1996? His Ralliart Europe team, knowing the Safari Rally eats running gear alive, figured out that it could swap out all four of the car's suspension corners at every service stop — in under the FIA's specified 20-minute limit. With fresh gear on every stage, Mäkinen again and again set the fastest times. Don't underestimate how that spirit can find its way into a company's high-performance production cars. Ultimately, the Evo X is impressive, and Evos I-IX are cars no one can stop talking about. If you can't build cars like that, you might as well quit and build appliances. People need those too. Maybe one day, when we're watching electric cars on TV as they plummet through rally stages, just like their internal-combusting forebears once did, we may look outside and see an electric Evo parked in the driveway. Until then, sayonara old friend.

As we already have a few HyPer Lights customers here and Mike is a regular of the forum so it is a nice addition to our site. Hopefully Mike will post up some company info/photos/spec etc. soon.

I restructured the review section for member written or submitted reviews. Post up anything you have that relates to audio or automotive, or post up ones others have written that are very good (but make sure you site where it came from and who wrote it).

Hey CA-F crew. Wanted to see what changes anyone feels needs to be made to help get some traffic going on here again?

Thiele-Small Parameters In the early seventies, several technical papers were presented to the AES (Audio Engineering Society) that resulted in the development of what we know today as 'Thiele-Small Parameters'. These papers were authored by A.N.Thiele and Richard H. Small. Thiele was the senior engineer of design and development for the Australian Broadcasting Commission and was responsible at the time for the Federal Engineering Laboratory, as well as for analyzing the design of equipment and systems for sound and vision broadcasting. Small was, at the time, a Commonwealth Post-graduate Research Student in the School of Electrical Engineering at the University of Sydney. Thiele and Small devoted considerable effort to show how the following parameters define the relationship between a speaker and a particular enclosure. However, they can be invaluable in making choices because they tell you far more about the transducer's real performance than the basic benchmarks of size, maximum power rating or average sensitivity. Fs This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well. Re This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load. Le This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs. Q Parameters Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same. As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance. Vas/Cms Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature — a precisely controlled lab environment is essential. Cms is measured in meters per Newton. Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It’s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others. Vd This parameter is the Peak Diaphragm Displacement Volume — in other words the volume of air the cone will move. It is calculated by multipying Xmax (Voice Coil Overhang of the driver) by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer. BL Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority! Mms This parameter is the combination of the weight of the cone assembly plus the ‘driver radiation mass load’. The weight of the cone assembly is easy: it’s just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push. EBP This measurement is calculated by dividing Fs by Qes. The EBP figure is used in many enclosure design formulas to determine if a speaker is more suitable for a closed or vented design. An EBP close to 100 usually indicates a speaker that is best suited for a vented enclosure. On the contrary, an EBP closer to 50 usually indicates a speaker best suited for a closed box design. This is merely a starting point. Many well-designed systems have violated this rule of thumb! Qts should also be considered. Xmax/Xlim Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). The Xmax figures on this website are expressed as the greater of the result of the formula above or the excursion point of the woofer where THD reahes 10%. This method results in a more real world expression of the usable excursion limit for the transducer. Xlim is expressed by Eminence as the lowest of four potential failure condition measurements: spider crashing on top plate;vVoice coil bottoming on back plate;vVoice coil coming out of gap above core; or the physical limitation of cone. A transducer exceeding the Xlim is certain to fail from one of these conditions. High pass filters, limiters, and enclosure modeling software programs are valuable tools in protecting your woofers from mechanical failure. Sd This is the actual surface area of the cone, normally given in square cm. Usable frequency range This is the frequency range for which Eminence feels the transducer will prove useful. Manufacturers use different techniques for determining ‘Usable Frequency Range’. Most methods are recognized as acceptable in the industry, but can arrive at different results. Technically, many loudspeakers are used to produce frequencies in ranges where they would theoretically be of little use. As frequencies increase, the off-axis coverage of a transducer decreases relative to its diameter. At a certain point, the coverage becomes ‘beamy’ or narrow like the beam of a flashlight. Following is a chart that demonstrates at what frequency this phenomenon occurs relative to the size of the transducer. If you’ve ever stood in front of a guitar amplifier or speaker cabinet, then moved slightly to one side or the other and noticed a different sound, you have experienced this phenomenon and are now aware of why it occurs. Clearly, most two-way enclosures ignore the theory and still perform quite well. The same is true for many guitar amplifiers, but it is useful to know at what point you can expect a compromise in coverage. Power handling This specification is very important to transducer selection. Obviously, you need to choose a loudspeaker that is capable of handling the input power you are going to provide. By the same token, you can destroy a loudspeaker by using too little power. The ideal situation is to choose a loudspeaker that has the capability of handling more power than you can provide lending some headroom and insurance against thermal failure. To use an automobile as an analogy; you would not buy a car that could only go 55mph if that were the speed you always intended to drive. Generally speaking, the number one contributor to a transducer’s power rating is its ability to release thermal energy. This is affected by several design choices, but most notably voice coil size, magnet size, venting, and the adhesives used in voice coil construction. Larger coil and magnet sizes provide more area for heat to dissipate, while venting allows thermal energy to escape and cooler air to enter the motor structure. Equally important is the ability of the voice coil to handle thermal energy. Eminence is renowned for its use of proprietary adhesives and components that maximize the voice coil’s ability to handle extreme temperatures. Mechanical factors must also be considered when determining power handling. A transducer might be able to handle 1,000W from a thermal perspective, but would fail long before that level was reached from a mechanical issue such as the coil hitting the back plate, the coil coming out of the gap, the cone buckling from too much outward movement, or the spider bottoming on the top plate. The most common cause of such a failure would be asking the speaker to produce more low frequencies than it could mechanically produce at the rated power. Be sure to consider the suggested usable frequency range and the Xlim parameter in conjunction with the power rating to avoid such failures. The Eminence power rating is derived using an EIA 426A noise source and test standard. All tests are conducted for eight hours in a free-air, non-temperature controlled environment. Eminence tests samples from each of three different production runs and each sample must pass a test exceeding the rated power by 50 to 100W. The Eminence music program is double that of our standard Watts rating. Sensitivity This data represents one of the most useful specifications published for any transducer. It is a representation of the efficiency and volume you can expect from a device relative to the input power. Loudspeaker manufacturers follow different rules when obtaining this information — there is not an exact standard accepted by the industry. As a result, it is often the case that loudspeaker buyers are unable to compare 'apples to apples' when looking at the sensitivities of different manufacturers’ products. Eminence sensitivities are expressed as the average output across the usable frequency when applying 1W/1M into the nominal impedance. ie: 2.83V/8 ohms, 4V/16 ohms.

Simply: http://store.soundsolutionsaudio.com/categories/amps/shop-by-brand/synergy-audio.html

Here is a great bit of info from Neil: Power compression is a topic that is rarely discussed, but always important. When you hear someone call various theile/small parameters a

Just a few slight improvements, check out the new pictures: ][/size]

Relaying thanks to Mike (95Honda) and bromo, care of Audiopulse. # 1 Subwoofers have an RMS rating Speakers actually have a very complex thermal compression relationship and certainly can not be quantified by just one or two numbers typically called RMS and Program or Peak. Because voice coils in traditional drivers are inherently resistors, any amount of voltage generates some amount of heat which then adversely changes the resistance and properties of the speaker. This is the principle of thermal compression: As the voice coil heats up, the resistance changes and the efficiency and performance of the driver decrease until the point of maximum thermal compression. There are some unique types of materials that have a close to zero temperature coefficient and of course there is also superconducting metals that operate at subzero temperatures with no indications of any sort of resistance. In theory, only these types of materials would have no thermal compression, but they are not employed or very practical yet. Copper and Aluminum are still the two most widely used materials for voice coils. Both copper and aluminum heat up considerably and the resistance changes as a function temperature, and there lies the problem, therefore a discrete RMS scalar value is entirely inappropriate. Under heavy use, the TSP parameters can shift as much as 35% and in a generally un-favored direction. (higher Qts, lower sensitivity). The common ultra high RMS ratings we see of large and expensive subwoofers are at best marketing ploys to make the driver seem far more worthy than it is, or in fact they are really intended to give the customer an idea of what type of amplifier to buy. The fact is, even the highest “RMS” rated subwoofers in the world in excess of 5 digit figures will begin to compress with far less power than you would ever image, try only a few hundred watts! (no joke!). Now this doesn’t mean you still don’t need lots of power to reach the maximum potential of the driver. As a rule of thumb, the amplifier should be much more capable than what the driver needs on average. For example, quick short bursts will produce huge SPL’s and the voice coil will not have time to heat up as much, but longer term high power use will result in considerable performance regression if not failure from glues giving way due to heat or differences in the thermal expansion of materials around the glues. Under heavy use thermal compression limits begin to play a large part in SPL but most people are oblivious to this concept. It is true that woofers can be used well into their thermal compression state, and typically that is what occurs. As the power increases linearity, the SPL does not increase linearly. This is some form of compression, usually thermally related unless the woofer is beyond or close to xmax. In an ideal non-compression circumstance of either power, BL or otherwise, you can expect a 3dB increase every time the power is doubled. Rarely does this ever occur, in extremely compressed and dangerous states it can be less than 1dB! As a woofers reaches its very limits, unless failure occurs there will become a point where the resistance of the voice coil is rising faster than the power going into the subwoofer. When the resistance doubles as the power doubles then absolute thermal compression has set in. In practice you can’t actually increase the power from the amplifier because most amplifiers start to produce less power as the resistance increases because almost every car, home and pro audio amplifier is a constant voltage source rather than a constant current source. So in a way this phenomenon is a self limited occurrence that accidentally works to protect the driver. However, running the driver at or near the maximum thermal compression limit will likely result in rapid failure. Ultimately, thermal compression is a very large but unavoidable shortcoming of mass controlled transducers. Likely, compliance controlled transducers, or rather subsonic transducers are not limited by their thermal properties as much, but rather their compliance or linear limits (xmax). It is believed by a few experts in the field that thermal compression plays a much greater role in linearity and distortion than we know of, but it’s rarely discussed. # 2 More xmax means more SPL Subwoofer drivers really can be broken down in two categories: “Mass” controlled drivers and “compliance” controlled drivers. Mass controlled drivers tend to have low xmax and high sensitivity. These tend to be punchy and very loud and mostly used in live concerts for sound reinforcement or even car SPL competitions. Compliance controlled subwoofers which tend to be the majority of car audio subwoofers have high xmax, more weight, lower sensitivity, but more SPL in the lower frequency spectrum. Then there are of course hybrid drivers which are basically mixes of the two. Any driver in these categories can sound good or bad, but more important is being able to use the woofer where it performs the best. Using a low xmax woofer for subsonic content is probably not wise, likewise using a high xmax low sensitivity driver for sound reinforcement is not going to be very effective. In truth, there is no best driver and most drivers can overlap these zones with good results. We are not really used to the idea of a two way subwoofer, but as we demand more and more SPL and deeper bass, we may some day find that two different types of subwoofers used together are required to get the full reference SPL effect we all hunger for! So yes, more specified xmax does mean more SPL but only for lower frequencies. Generally speaking, during lower frequencies, the driver tends to run out of usable throw (beyond xmax) before high thermal compression states occur and mechanical failure is a greater risk. 0-40Hz is primarily mechanical, 40-60 is in between) 60 and up is going to be more thermally limited. 0-20Hz is the subsonic content and in fact there are more efficient methods of producing bass in this spectrum rather than a regular piston based transducer. Surprisingly, even the largest drivers with high xmax and big voice coils can be bottomed out or run past a safe mechanical state with only a few hundred watts if the frequencies are low enough. Without a high pass (subsonic) filter, or in a low tuned system, bottoming out or breaking a driver could be a very real possibility without careful modeling and testing. The difference in displacement from 40Hz to 20Hz or rather half the frequency, or one octave, is quadruple! In the simple large sealed box example, that means if your woofer displacement is 1” peak to peak at 40Hz, you’ll bottom out just about anything in existence by the time you dip below 20Hz without protection. Often times when people want more SPL, they really need higher sensitivity in the form of higher BL product or less moving mass, rather than more xmax because 50-60Hz is really what they are after. This is a very sensual frequency range for humans and much of the bass in music content exists in that frequency domain. # 3 Subwoofers are fast / slow More appropriately labeled Damping or Ringing, these concepts are really reciprocals of one another have nothing to do with speed, tightness, “boomieness” or any other misused and inappropriate term for subwoofers. Subwoofers, or rather bass drivers, all move at the same frequency when instructed to via an input single. The difference is really about the Q alignment of the system. There are many famous Q alignments which produce various frequency responses, but beyond the complex mathematics is a fundamental principal of force and acceleration and the driver will respond to a sinusoidal wave at various accelerations depending on the moving mass and force that the voice coil and motor generate on the cone. Therefore any driver can be faster or slower depending simply on the voltage! It makes little sense to call any driver faster or slower. Damping or Ringing is really what we’re after and the amount of either is really a function of system volume along with the electro-mechanical damping factor of the driver. For example, in a sealed box system, as the volume of the cabinet becomes small, the internal pressures increase when the driver pushes in and out. This pressure is a force which, not nearly as strong as the electromotive damping force, works in the opposite direction. Contrary to intuition, higher internal pressure (which we tend to associate with tightness or stiffness) decreases damping and promotes ringing at one particular frequency (Fc in the case of a sealed box). The pressure from the air inside the box works against the driver’s natural damping factor of 1/(Qts). When the pressure becomes large relative to the motor’s damping factor, the driver will ring more and cause a peak in SPL at the given resonate frequency (Fc). This tends to be somewhere around 40-60Hz in a given sealed box, but could be outside that range under abnormal circumstances. This peak is ill desired and is accountable to the proclaimed “boomy” sounding subwoofers which tend to lack clarity, good transit response and dynamics. However some people prefer some ringing because it provides a natural boost in a very audible frequency band. Likewise, in a larger box, the Q will decrease and the ringing and SPL around that frequency will too, but the low end will open up and you’ll have more deep bass. This tends to sound better and more controlled. On the flip side, over dampened drivers tend to have poor low frequency response and require equalization to boost the low frequencies. They tend to work better in vented boxes where their larger motor force factor (BL^2/Re) is put to good use with a resonator which then makes the low end much more efficient with its increased displacement. Likewise, drivers with high Qts will work better in sealed boxes and should be exempt from being used in a ported system without careful consideration. When high Q drivers are used in a vented system they will ring at the tuning frequency of the box (Fb in this case) and the “boomy” problem is considerably worse. # 4 Ported boxes don’t sound as good as sealed In most cases this is strictly a result of linear response vs non-linear response and it could go both ways. 4th order systems or “vented” boxes tend to be far more particular to volume, port size and length and the driver TPS’s rather than sealed systems. Misalignments are therefore amplified and greatly affect the frequency response. Often times in car audio, ported boxes are not tuned low enough, or the volume is too large and there is a large peak in the frequency response from literately too much sensitivity or SPL at a very narrow frequency band. The other issue is if the driver does not have enough BL or has too high of a Qts and becomes under damped at resonance. This again leads to drastic peaks at the resonating frequency; however in this case, the driver will be peaky there regardless of content and it will sound ultimately less dynamic and very bottom heavy. However, a well designed vented box may have considerably lower distortion and higher dynamics than a sealed box because of the added SPL gained from the port without increasing the active driver displacement requirements. Sealed systems evoke the most non-linear driver behavior to reach any given SPL, so in fact, they could be the worst sounding system if your SPL demands are considerable. It is important to model a ported design or ask the manufacture for a recommendation. It is also critical to include a high pass filter on the active driver in a ported box for protection. # 5 Subwoofers care what they play Your subwoofer driver does not have a conscience, and it does not perform better with one type of music over another. It’s just a driver. Good subwoofer systems will play all types of music or movie material very well. A bad subwoofer system may have a null or peak in the frequency response that may benefit some material over others but essentially this non-linear behavior is not ideal. It is true that movies have lower frequency content and perhaps more dynamic bass than music, especially with the recent compressed CD’s of the last 10 or so years, but a good system can be used for movies and music alike if it is indeed a “good” system. It is also true that it tends to be more important to emphasize subsonic frequencies in the home theater environment versus the music environment where there is simply less emphasis on subsonic inaudible material. As a tradeoff, you can align a system to be more efficient above 30Hz or so. This trade off reduces the bandwidth but increases the SPL. Careful consideration should be taken to insure linear response is still maintained. It is very easy to have peaky bass with low Q drivers in high tuned ported systems. This is approaching the concept of basic SPL vehicles which use low Q, highly sensitive drivers tuned very high for very narrow but ferociously peaky response. Such systems are not very ideal for listing to music material of any kind. If you want your system louder, then it is better to add a second driver, more volume and more amplification, rather than tuning higher. It is important to understand that getting more SPL without compromise is never very cheap! # 6 Sealed box can take more power than ported There is some truth to this, and some myth, but as far as the thermal limits of the driver are concerned, it can’t take more power one way or another. However, in a sealed box the driver will require more power to reach the same SPL as the frequency range lowers. A ported system is simply more efficient so it wont need as much power to reach the same SPL. Based on the mechanical limits of a driver, different frequencies can take different power loads. At higher frequencies, driver can be pushed hard and won’t necessarily be in a mechanical-risk state. However the driver tends to be in a higher thermal compression state and could be thermally at risk. This is true for both ported and sealed boxes. However, for lower frequencies, the sealed box also acts as a filter in a way because the internal air pressure prevents the driver from over excursion. In a sealed box, the compliance of the suspension system almost always forgoes that of the air spring system unless the box is very large. In a vented box, there is no pressure to protect the driver and furthermore, when the system unloads below resonance, the active driver’s excursion increases exponentially and a high pass (subsonic) filter is critical to prevent mechanical failure. # 7 Sensitivity does not matter for subwoofers Sensitivity is indeed very important for subwoofers. Not all frequencies are limited by xmax. In fact, most of the bass frequencies for music are really limited by sensitivity or more accurately BL product and moving mass, but not by maximum driver displacement. Higher sensitivity means more SPL and ultimately better performance especially for upper bass punch or kick such as a “kick drum” which resonates at 63Hz. In fact, all good SPL competition drivers need to have high sensitivity not xmax! There are several standards for sensitivity. SPL at 2.83 volts or SPL at one watt. The SPL at one watt is the more accurate number as 2.83 volts could correlate to more than 1 watt which would not be relatively appropriate to go by. Also sensitivity is a function of, in part, the driver’s cone area which is never quite explicit and could be exaggerated slightly. Ultimately as engineers, we do strive for high sensitivity because not all bass resides in subsonic domain and many good sounding subwoofers are in fact good because they have great sensitivity and not necessarily high xmax. # 8 Smaller drivers sound better than bigger drivers One of the biggest myths about woofers is that 8’s and 10’s are “tighter” and “cleaner” than 15’s or 18’s. Nothing is further from the truth. What tends to happen is that the smaller drivers have lower Q’s because manufactures tend to put large cones on smaller motors to increase SPL and sensitivity but not BL product. Well unless the motor can compensate for the extra mass it has to push, then the Qts will not be the same as the smaller drivers and ultimately the driver may not be suited for the same kinds of alignments and could ring too much and compromise the perceived sound quality. Having said that, high Qts drivers are not any less “tight” or “musical” than well dampened drivers, it’s just they require larger boxes and less internal pressure to prevent ringing. Ultimately there becomes a point where a driver really should be used in an infinite baffle where its actual Qts and Fs becomes the system Qtc and Fc. As enclosure volume decreases, Qtc increases and it will take a driver with a low Qts to make for an average Q system. So in conclusion, the only reason to use a smaller bass driver is for space, weight and potentially power considerations, but likewise, it is inappropriate to try and fit a larger driver into a space smaller than it is ideal for. # 9 I can compare two drivers using the same box What you will find is primarily how different TSP’s work in different boxes. And the differences usually observed are of course differences in TPS’s with a given system, rather than performance. The best way to compare two drivers is to make two different systems based on the driver itself and ensure that the frequency responses are linear to the range you desire, and then compare those two systems in terms of dynamic headroom, SPL and distortion. Simply saying one system is “louder” or “deeper” in the same box is inappropriate. In one case it could be a something as simple as an under dampened driver ringing a lot more than an over dampened one at resonance causing a larger peak in low frequencies throughout. It does not mean it’s louder or deeper or better outright, it is simply non-linear, and all bets are off. Proper enclosure deigns and/or EQ should be used for any system. #10 cone material affects the sound For low frequencies, the cone on a driver makes no difference in the sound whatsoever. The only possible affect it could have is in the case of a metal cone or very stiff composite cone that resonates at a high frequencies and buzzes. However this frequency would be up around 1000 to 2000Hz: Well beyond a bass driver’s usable limits. Various cone materials are used for various purposes. Some cones, such as composite core with fiberglass or carbon fiber skins are extremely light and very stiff, especially when pressed with epoxy. Other cones such as aluminum provide excellent thermal cooling to decrease voice coil operating temperatures when the heat is conducted though the (if possible) conductive former. The cones job is to push air, not break, and ideally not be too heavy (easier said that done). But they don’t change the tone, pitch or timbre of a subwoofer system whatsoever. Anyone who tells you otherwise is probably hearing differences in the motor distortion, likely related to BL, compliance or other non-linear distortions not relating to the cone. #11 bigger magnet means more magnetic force The motor is essentially the steel and magnets on the bottom of the driver. Its job to create a magnetic circuit that has an air gap where flux lines cross in one direction so that a coil can rest in this field and carry current which then produces a force up and down and moves the piston to create SPL. The force that this motor creates is dependent on the amount of power or rather current inside the conductor F = B*L*I. So we need a more intuitive understanding of how a motor affects a driver’s performance without considering how much current it receives. This is the simple concept of “force factor”. Larger motors will ideally have higher force factors, but this number not only affected by the motor, its affected by the voice coil size, length, distance to the motor (gap) and conductive martial used too. The end result is in fact the BL squared divided by Re (resistance of the vc). This is literally Newtons squared per watt and is called the force factor. The higher the number, the more efficient the motor voice coil combination is and the more performance you get out of the motor. BL, one of the many TS parameters you are probably somewhat familiar with. It is literally the magnetic field “B” crossed with the conductor length “L.” L does not in fact depend on the number of turns on the voice coil, but rather the actual cross section area of the coil itself which is inside the gap. While force factor is entirely important for any high performance driver, one should also consider the moving mass. A 600 horse power engine in a semi truck is pretty typical, but in a sports car it’s certainly something to gloat about. Together, the force factor, moving mass and the piston area account for sensitivity. This number is very important even for subwoofers, especially for frequencies above ~60Hz. #12 Double bass kick, only good sounding drivers can do it We have all heard that only good “SQ” drivers can do double bass kick because they have good transient response or something to that extent. This is really nothing more than linear frequency response and lack of ring. If high Q subwoofers are in small boxes or if low Q subwoofers are in large ported boxes, the frequency response of the system will likely be greatly non-linear. This non-linear response compromises relative SPL and can drown out certain sounds and frequencies. Room acoustics can also do the same thing. The same subwoofer may sound completely different in another room simply because there could be poor coupling and non-linear frequency response as a result of standing waves and peaks in the response curve. A peak at 80Hz may make for a rather anemic 60Hz response, and while 60Hz appears to be the problem, it’s actually from the nonlinear response else where! The bottom line is “double bass kicks” are usually not a function of the driver or driver’s performance but rather the system design, linear frequency and room equalization. Often times people associate double bass as something to do with speed and only good drivers are fast. Believe it or not, even the largest and heaviest drivers, have no problem producing low frequencies, even 300Hz is a relatively slow long wavelength with a slow impulse time. Subwoofers are in fact MUCH faster than you would expect. Bottom line is, the lack of double bass, within the working limits of a driver, is not a problem with the driver so much as it is probably a problem with the system design, room and/or EQ settings. #13 Transient response is better with sealed boxes The fact is “transient response” is truly misleading and probably entirely unimportant at least for low frequency response. What people hear is really a function of the linear frequency response and distortion. It is often accepted that transient is a function of timing, but our ability to hear differences of a few milliseconds of low frequencies is quite negligible which is why the low frequency group delay of a 4th order system is quite unimportant next to the sensitivity advantages provided. Transient does not exclusively depend on sealed or ported designs, high Q, low Q, in fact, even drivers with high inductance don’t outright suffer from “transient response” insofar as we can physically distinguish certain sporadic behaviors because within their working range, they may be very efficient and dynamic. The fact is, what makes bass indeed bass, are long wavelengths that take considerable time to pass our ears. The perception of transient is really a function of perceived sound quality and there is really not appropriate example for good “transient response”. We as humans hear two things, distortion and SPL, and in the end that’s really want matters. What does improve “transient” response or perceived quality is usually more headroom, more drivers (usually larger boxes depending on the Qts of the driver), better efficiency and ultra low distortion within the prescribed limits of the system or drivers within the system. Sealed systems in fact don’t offer better transient response no more than ported even with their lower group delay tendencies, at least to human ears! #14 It’s a bigger driver, then I need a bigger amp Often times larger drivers require less amplification, that’s sort of the idea. The concept of bigger woofers need more power is not always true and plays right into the ever progressing misconception of car audio. What you should consider is the efficiency of the subwoofer. Efficiency will literally tell you how much acoustic output you will get given an amount of power (assuming linear limits of course). If the driver is bigger, has a larger motor and has a higher sensitivity, there is no mystery about it, you are going to get more SPL with the same amplifier provided the impedance is similar and the amplifier can produce high voltage at impedance peaks when the driver naturally draws very little current for a narrow range. If a driver is more efficient and has a larger voice coil, well you just got your cake and you can now eat it. Not only will it be louder, but it will have less thermal compression and ultimately more sound provided all else is equal (but such is not usually not the case). It’s often difficult to make voice coils larger and increase sensitivity too. This usually requires very large motors and expense. Sensitivity is most easily achieved by weight reduction usually from the cone surround and voice coil. Sensitivity is often a trade off of xmax and thermal compression limits. However there are many larger drivers that don’t have ultra high sensitivity. A good pro audio subwoofer may have 6 to 10dB higher sensitivity over an average high excursion car audio subwoofer. That advantage makes them very capable with quite a bit less power at least for their frequency range which is usually above 40Hz. Likewise, SPL drivers ironically enough don’t need much power either! Let me repeat. True SPL drivers ironically enough don’t need much power! That’s because they are used in the higher frequency domain not limited by displacement and generally have great sensitivity numbers. They need this in order to get the excursion and ultimately SPL they need to win contests. High sensitivity and lots of power means lots of SPL provided the driver is still reasonably linear and does not physically break of course. Note: Strictly for SPL contest, drivers are normally burped at Fc (system resonance) which is the point of maximum current draw and minimum active driver displacement which is why excessive power must be used. Do not confuse that requirement with the much lower power requirements for sound reproduction outside that single SPL frequency. It’s important you know the TSP’s of the driver you buy, otherwise it could be the wrong driver for you! Who buys a car without knowing the horsepower? Just because a driver big and the manufacture claims pie in the sky RMS numbers doesn’t mean a thing! #15 Neodymium will lose its strength with heat Of course it will, and so will ceramic motors too, but the fact is, under even extreme operating conditions, it’s not likely the motor will ever reach these temperatures. There is just too much steel to absorb the heat from the voice coil in almost any practical case. In practice, gradual demagnetization due to use simply does not occur. We have been making high power neodymium based drivers for many years now and we have never once measured a discernible number from heat. While Neodymium is nearly 10 times as strong as a similar sized ceramic magnets, it can cost up to 50 times too which is almost exclusively why it is not used often. Also, traditional overhung motors, which account for more than 95% of all car audio designs, can get everything they need out of a ceramic magnet assembly and stronger neodymium would be perhaps unnecessary. If we could use neo more, we would, but because it’s a patented martial, it’s just not economically practical for most designs. Furthermore, in order the magnetize neodymium, A magnetizer with over twice as much power and energy needs to be used. Many manufactures lack the capabilities of even magnetizing neodymium, so it becomes impractical to not only use it, but to manufacture. #16 Its all about maximum displacement<a name="16"> A DIY’er favorite statistic, displacement / dollars. If you’re considering any bass above 40Hz then throw it out the door right now. Often times people assume that simply because one or more drivers have more maximum displacement over another type of woofer, than they will ultimately be the better performer(s). In many cases this is true, but it’s not true in general. Displacement alone does not guarantee SPL. In fact, SPL depends on not only displacement, but frequency range, sensitivity, box size, and BL product too. This is simply a matter of converting energy into acoustic sound pressure level and different devices work more efficiently than others for different frequency ranges. For subwoofers, it is generally accepted that BL product is the dominate factor that accounts for much of the performance or rather system efficiency, especially in a bass reflex or more complex system where there is a lot of air mass to displace. But keep in mind, depending on the type of system, size, frequency range, power and thermal limits, there may be even more critical and dependent variables that determine the overall performance of a system. None the less, high displacement is usually a good indicator that the subwoofer can excel in deep bass SPL. Of course there are other factors to consider depending on the system of system.

Check it here: https://www.parts-express.com/dayton-audio-dsp-408-4x8-dsp-digital-signal-processor-for-home-and-car-audio--230-500

If you don't get it by now, sign up for it. It is free. Also Next Auto's is an online news site I check. To get the free magazine head on over to: http://www.windingroad.com/ The most recent edition has some sweet articles.

For our G+ people, and to help expand the reach and functionality of this site, we started a Google+ community. Check it out here: https://plus.google.com/u/0/communities/107117485132114724035 G+ seems to be the go to place now for people who are sick of FB.

Was thinking for the CA-F members, we could start a running work out topic. I am in the gym at least 3 evenings a week, but I know I will never be in the condition I was in when I was training, or personal training or during college. Since August I have stepped it up some. So is anyone else actively working out? I am doing about 25 mins of cardio and 35 mins of weights per work out.

I was screwing around a little with mine. Need to use better colors and smoother animation, but you get the idea.

Have you ever completed an enclosure that was a touch too small? Your low end sounds cramped but you don't want to or can't build a brand new enclosure. You throw in some polyfill and are blown away by the improvements. Then you go online to talk about it and everything gets confusing. You don't know why it works or what it really did, but you know that it sounds better. Maybe it's time you learned more about it! Firstly, there are a few primary types of fill that are used. This includes polyester fiberfill, fiberglass insulation, and long-fiber wool. Of these three, polyester fiberfill is perhaps the best option, and also the origination of the term "polyfill". These products can easily be found in several stores, including Wal-Mart, Home Depot, or a local crafts and fabrics store, and all are extremely affordable (typically less than $2/pound). It is also very easy to apply to the inside of your enclosure: simply staple or glue it to the inside of your enclosure. How does it work? Stuffing a box with polyfill makes it seem larger and it all relates to thermodynamics. When polyfill is added to an enclosure, it changes the behaviour of the airspring in the enclosure from "adiabatic" to "isothermal". The term "adiabatic" implies that there is no heat transfer occurring. An isothermal process occurs once the polyfill has been added. As the air passes through the polyfill, the fibers wiggle and cause some of the energy created by the airspring to be dissipated as heat. This heats the surrounding air molecules warmer, causing the air to become less dense. Being that sound passes easier through a denser medium, the speaker interacts with your enclosure as if it is larger than it actually is. The effective increase in enclosure size can be as much as 40%! This has some very obvious benefits that are inherent of a larger enclosure. Firstly, it becomes more efficient (a larger enclosure is always more efficient than a smaller one for any given driver). Second, the f3 (or the frequency at which SPL is down by 3dB) will be lower, providing a little bigger bottom end. While these are both great advantages, they decrease the effective damping of the speaker as well, meaning the speaker can be more likely to bottom out or over-excurt itself. Naturally, this is speaker, frequency, and power dependent. If used in a ported enclosure, you will also see the Fb (or the resonant frequency of your port) drop lower. There are some additional worthy considerations. Adding polyfill to an enclosure can be a great choice. However, too much polyfill can be a bad thing. At a certain point, the stuffing becomes too dense and the fibers no longer wiggle. At this point, not only have you taken away the size benefit of adding polyfill, you have actually decreased the effective volume as the polyfill is now taking up room inside your enclosure. It is also worth mentioning that polyfill is not as effective in a large enclosure. Let's combine these two thoughts into two simple rules: 1. If the enclosure is less than 2.5 - 3.0 cubic feet in size, you should use no more than one and a half pound of polyfill per cubic foot available in your enclosure. 2. If the enclosure is greater than 2.5 - 3.0 cubic feet in size, you should use no more than one pound of polyfill per cubic foot available in your enclosure. Specific examples of polyfill's effects on various enclosure sizes (with varying amounts of polyfill in each size) can be found in The Loudspeaker Cookbook by Vance Dickason or in an article written by Tom Nousaine for the March/April 1995 edition of "Car Stereo Review". There is one last point that you will hear from time to time regarding polyfill: that polyfill stops standing waves in an enclosure. When referencing an enclosure for a subwoofer playing a fundamental frequency that falls in the typical range, this is simply false. A standing wave in this range of frequencies would be several feet long and, thus, unlikely to occur. However, higher order harmonic distortion is possible, and can potentially colour music. Being that these higher order harmonics will be progressively shorter (in terms of wavelength), polyfill can be effective for this purpose. However, audibility, particularly at high SPL, can be quite minimal. Using polyfill in an effort to absorb standing waves or various distortion is most effective in large enclosures for your midrange and is not particularly effective for a subwoofer. Hopefully you now have a greater understanding of what polyfill does and doesn't do, while also enjoying the opportunity to absorb some scientific content as well. If you're still undecided, be wild and adventurous: put some polyfill in your enclosure right this minute!