Why the high watt spec in subwoofer amplifiers?

Ron Resnick

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Some subwoofer towers in four tower, "statement" speaker systems use high-watt class D amplifiers (e.g., Evolution Acoustics MM7, Genesis 1.2) and many standalone subwoofers use high-watt class D amplifiers as well (e.g., JL Audio, MartinLogan, Seaton, Velodyne).

We know the obvious reasons manufacturers use class D amps: they are small, they are inexpensive per watt and they run cool (i.e., they are efficient).

But what is the reason for the high wattage?

Is it because high wattage increases the damping factor of the amplifier and thus keeps the cone driver under tighter control?

Is it just marketing since class D watts are so cheap that companies can design for a high watt number for low marginal cost and try to impress consumers?

Is there any reason why 2,000 class D watts are the better sounding amplification for a subwoofer than 500 class AB watts?
 

Robh3606

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Some subwoofer towers in four tower, "statement" speaker systems use high-watt class D amplifiers (e.g., Evolution Acoustics MM7, Genesis 1.2) and many standalone subwoofers use high-watt class D amplifiers as well (e.g., JL Audio, MartinLogan, Seaton, Velodyne).

We know the obvious reasons manufacturers use class D amps: they are small, they are inexpensive per watt and they run cool (i.e., they are efficient).

But what is the reason for the high wattage?

Is it because high wattage increases the damping factor of the amplifier and thus keeps the cone driver under tighter control?

Is it just marketing since class D watts are so cheap that companies can design for a high watt number for low marginal cost and try to impress consumers?

Is there any reason why 2,000 class D watts are the better sounding amplification for a subwoofer than 500 class AB watts?

Hello Ron

Most subwoofers if not all have a tailored response curve and rely on some boost to linearize the last octave response. 6 db of boost doesn't sound like much but that requires 4X the amp power. So that 800 watt amp really works out to 200 available watts where the peak in the boost curve is.

Rob:)
 

LL21

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hey ron,

in fact, if you read the review of the Paradigm Sub2...they specifically state that if you dont have a 240V supply, it sort of chokes the amps inside which were designed to the max in order to keep control of the 6 x 10" drivers. apparently, it tooks 2-3 years to design the amp...and still, if you dont provide it with sufficient juice, you dont get the full effect of the sub as it was originally designed...
 

Ron Resnick

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Yes, I saw that. In case I have in the future subwoofers thirsty enough for 240VAC I am making sure I have two 240VAC outlets next to the 120VAC outlets fed from the Torus.

But my question still remains . . . what about the high wattage allows the amplifier to "keep control" of the drivers? Does high wattage = high damping factor?
 
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Fitzcaraldo215

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Ron - the "new" subwoofer idea some time ago was one with a very small, sealed box. It was Bob Carver who introduced the idea. Since then, many variations and extensions of this theme by other makers have emerged. But, this whole concept requires really huge amplifier power, and that is where I think you see the big wattage numbers in subs. The emergence of Class D amplification has been an enabler of the spread of this design concept. Other design paradigms do not require this amount of power, especially in larger, unsealed boxes of various types, but they might have other tradeoffs in terms of delivering all that a sub should - bass extension, low distortion, etc.

I have had a JL Audio f113 in my system for a number of years. It has peak amp output of 2,500 watts, more or less following the Carver philosophy, though on steroids. I have been pleased as punch with the results. That sub might be the very best component in my system in terms of what it adds sonically, and I am delighted with it. If properly set up (w. DSP Room EQ), it just disappears on music. But, if you take it away, it subtracts a really large amount of sonic realism. Incidentally, my main speakers are ML Prodigys, like you, although I listen almost exclusively in hi rez multichannel with a mix of other MLs.
 

Jinjuku

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Ron - the "new" subwoofer idea some time ago was one with a very small, sealed box. It was Bob Carver who introduced the idea. Since then, many variations and extensions of this theme by other makers have emerged. But, this whole concept requires really huge amplifier power, and that is where I think you see the big wattage numbers in subs. The emergence of Class D amplification has been an enabler of the spread of this design concept. Other design paradigms do not require this amount of power, especially in larger, unsealed boxes of various types, but they might have other tradeoffs in terms of delivering all that a sub should - bass extension, low distortion, etc.

I have had a JL Audio f113 in my system for a number of years. It has peak amp output of 2,500 watts, more or less following the Carver philosophy, though on steroids. I have been pleased as punch with the results. That sub might be the very best component in my system in terms of what it adds sonically, and I am delighted with it. If properly set up (w. DSP Room EQ), it just disappears on music. But, if you take it away, it subtracts a really large amount of sonic realism. Incidentally, my main speakers are ML Prodigys, like you, although I listen almost exclusively in hi rez multichannel with a mix of other MLs.

Spot on. I'm running two sealed, dual opposed Infinity Kappa 120.w9. So four 12" drivers and using a Behringer iNuke3000 DSP to tailor system response.

It's integrated so well you don't realize it's there. But when you turn the sub amp off it's really eye opening. I've heard other systems ,with mainly ported, subs and you know that there is a sub in the mix for all the wrong reasons.
 
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asiufy

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Ron,

IIRC, there was something related to class D designs having better control of the woofers (negative feedback? or just high damping factor?).
Empirically, I've found out that's exactly the case, as they are seemingly able to control woofers (of any size) better than similarly powered Class A/B amps.
I guess it also helps that with Class D designers can fit a lot of power into a smaller space, such as inside a subwoofer enclosure, and have it run reasonably cool.
 

garylkoh

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Ron,

Robh3606 is correct - in a small sealed box, most subwoofers use a tailored response curve. Google "Linkwitz Transform" to get the math and circuitry needed. The smaller the box, the higher the boost needed to get to lower frequencies. Up to 18dB or 16x the amplifier power is required to get to flat.

Genesis subwoofers use a different "brute force" approach, and that is the servo-system. We use a combination of high-powered amplifiers and low-impedance voice coils to defeat the laws of physics. The servo-circuitry negates inertia and momentum of the woofer.

High wattage does not equate to high damping factor, and higher wattage amplifiers per se do not equate to better woofer control.
 

microstrip

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(...) Genesis subwoofers use a different "brute force" approach, and that is the servo-system. We use a combination of high-powered amplifiers and low-impedance voice coils to defeat the laws of physics. The servo-circuitry negates inertia and momentum of the woofer.

High wattage does not equate to high damping factor, and higher wattage amplifiers per se do not equate to better woofer control.

Gary,

You do not defeat the laws of Physics, you just use more complex laws of Physics. Good bye Thiele/Small parameters ... ;)
 

Ron Resnick

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Thank you you Fitzcaraldo, asiufy and Gary!
 

LL21

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Ron,

Robh3606 is correct - in a small sealed box, most subwoofers use a tailored response curve. Google "Linkwitz Transform" to get the math and circuitry needed. The smaller the box, the higher the boost needed to get to lower frequencies. Up to 18dB or 16x the amplifier power is required to get to flat.

Genesis subwoofers use a different "brute force" approach, and that is the servo-system. We use a combination of high-powered amplifiers and low-impedance voice coils to defeat the laws of physics. The servo-circuitry negates inertia and momentum of the woofer.

High wattage does not equate to high damping factor, and higher wattage amplifiers per se do not equate to better woofer control.

Without going into anything proprietary...is the Genesis servo approach similar to Velodyne's? Feel free to keep it academic as i do meant to turn this into a Genesis v Velodyne question. Thanks, Gary! Happy Thanksgiving!
 

Aluminous Audio

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I have wondered about the "wattage race" myself. We are using a 175 watt class D amplifier on our Su13.01 Subwoofer by design. The available 175 watts of amplifier power is easily up to the task of delivering musical low frequencies. As with any amplifier, I think the wattage specification is more of a marketing tool than a measure of quality sound.
Some subwoofer towers in four tower, "statement" speaker systems use high-watt class D amplifiers (e.g., Evolution Acoustics MM7, Genesis 1.2) and many standalone subwoofers use high-watt class D amplifiers as well (e.g., JL Audio, MartinLogan, Seaton, Velodyne).

We know the obvious reasons manufacturers use class D amps: they are small, they are inexpensive per watt and they run cool (i.e., they are efficient).

But what is the reason for the high wattage?

Is it because high wattage increases the damping factor of the amplifier and thus keeps the cone driver under tighter control?

Is it just marketing since class D watts are so cheap that companies can design for a high watt number for low marginal cost and try to impress consumers?

Is there any reason why 2,000 class D watts are the better sounding amplification for a subwoofer than 500 class AB watts?
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
Sep 6, 2010
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www.genesisloudspeakers.com
Without going into anything proprietary...is the Genesis servo approach similar to Velodyne's? Feel free to keep it academic as i do meant to turn this into a Genesis v Velodyne question. Thanks, Gary! Happy Thanksgiving!

They are similar. Both use acceleration and a comparator circuit. Velodyne uses very high feedback. I think that there is an appropriate amount of feedback and use lower feedback.

Happy Thanksgiving, Lloyd
 

LL21

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They are similar. Both use acceleration and a comparator circuit. Velodyne uses very high feedback. I think that there is an appropriate amount of feedback and use lower feedback.

Happy Thanksgiving, Lloyd

Thank you. Same to you and yours, Gary. We have much to be grateful for, and i imagine much the same could be said for most on this great Forum.
 

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