Subwoofers with digital amps?

JackStraw · « **on:** 17 Dec 2003, 03:57 pm »

Much of the buzz in the latter half of this year has been focused on digital amp technology. Reviews of units like the Sony ES receivers and AVD all in one units and the Panasonic SA-XR45 seem to agree that bass control is fantastic with these cheap digital amps.

This gets me wondering... where are the digitally amped subwoofers? I recall audiojerry getting excited about a low cost Yamaha sub, and some folks in the post speculating that it might have a digital amp. See http://www.audiocircle.com/index.php?topic=1948&postdays=0&postorder=asc&highlight=yamaha&start=0

But, is anyone aware of larger driver higher end subs released or planned using the digital amp architecture?

csero · « **Reply #1 on:** 17 Dec 2003, 05:19 pm »

I'm using a 18" ELF sub with the Pana amp and digital crossover. Very good, works down to single digit Hz.

JackStraw · « **Reply #2 on:** 17 Dec 2003, 09:26 pm »

Quote from: csero

I'm using a 18" ELF sub with the Pana amp and digital crossover. Very good, works down to single digit Hz.

Do you mean that you're driving a passive sub with the Panasonic? This would definitely be an interesting use of the "Party Mode" that I've read about on that thread. Not exactly what I meant, but interesting nonetheless.

What I'm wondering is whether sub manufacturers such as Adire, HSU, SVS, ACI, etc. are designing powered subs that have digital amps built in instead of the standard SS plate amps.

rkapadia@ROOP · « **Reply #3 on:** 17 Dec 2003, 10:39 pm »

I don't think we'll be seeing digital amplified subs at least for another year -

Proven designs of class A/B amplifiers deliver highe efficiency and stability, not to mention lower manufacturing costs due to the length they've been available.

It's not yet determined the impact of vibration on durability of digital amplification designs, and also sensitivity to EMF/RMI is greater for dgital modulating amps versus solid state. It would be a huge pain for a manufacturer if they started shipping with digital amps only to find them non-functional due to all the cabinet vibration in a subwoofer. The shipping costs alone would be painful.

Regards,

rosconey · « **Reply #4 on:** 17 Dec 2003, 11:42 pm »

alot of cheap subs use class d digital amps-i had a dahlquest pdq1500 it had a digital amp(class d) a friend has a infinity top of the line sub its class d also

JohnR · « **Reply #5 on:** 17 Dec 2003, 11:50 pm »

Quote from: JackStraw

This gets me wondering... where are the digitally amped subwoofers?

Here's one:

http://www.diycable.com/main/product_info.php?products_id=478

Or make your own

http://www.diycable.com/main/product_info.php?products_id=485

Kevin P · « **Reply #6 on:** 18 Dec 2003, 01:40 am »

Yes... the new digital amplifiers are all PWM technology. Class D amps have been around for years with lower switching frequencies making them only usable for sub amps. The newer ones we are selling for full range have a faster modulator allowing them to correct the signal 500,000- 1,000,000 times per second.

One advantage in high power applications is PWM amp efficiency. Not as much heat to disipate means smaller heatsinks and possible use without noisy fans. In terms of their dampening factors... they are nothing outstanding but certainly sufficient. Most of what people are talking about subjectively with different amps and speaker combinations often has more to do with the harmonics way up in the mid-bass & above. The new digital amplifiers seem to have the advantage of having a different distortion spectrum than the more typical Class A or Class A/B amplifiers. From what I understand it is non-harmonic in nature and that might have more to do with the percieved bass than their dampening factors.

For a sub this would all be a non-issue. I'd concentrate on buying sufficient power with the control features you need rather than worrying about digital vs. analog. Our hearing is much more forgiving under 80HZ and the subtle differences you are going to hear up in the midrange are just not audible at these frequencies.

Val · « **Reply #7 on:** 18 Dec 2003, 05:01 pm »

More important, I believe, is what http://www.velodyne.com">Velodyne is doing in their Digital Drive series subwoofers, processing the subwoofer signal in the digital domain to provide room correction and several other goodies.

Val

Kevin P · « **Reply #8 on:** 18 Dec 2003, 05:28 pm »

Val,

I would agree.... DSP tools where you can do parametric EQ are a wonderful tool. Software based versions will have more flexibility than the analog ones and we are getting to the point where they are becoming more cost effective.

The term "Room Correction" is being use rather liberally though. Many companies with this technology are selling it as though the room doesn't matter. There is no physical way to correct for some room problems in the upstream signal. Also... I'm not that convinced that we have the necessary basic research done to understand what things to correct and what things not to correct.

The "auto correct" features are a double-edged sword. If you try to correct for a null with EQ you end up eating unnecessary power quick and I'm not sure how the computer knows which dips are from room nulls. Even with all the fancy features people are going to need to understand them in order to get the correct installation. This stuff is in its infancy though and it is exciting to see the possibilities.

Val · « **Reply #9 on:** 18 Dec 2003, 05:37 pm »

I agree, Kevin. Anyway, the possibility of at least reducing the peaks (the most obnoxious to me) and juggling with several variable parametric equalizers, phase and crossover frequencies and slopes is lots of icing on the cake!

csero · « **Reply #10 on:** 18 Dec 2003, 07:33 pm »

Quote from: JackStraw

Do you mean that you're driving a passive sub with the Panasonic? This would definitely be an interesting use of the "Party Mode" that I've read about on that thread. Not exactly what I meant, but interesting nonetheless.

Not exactly. I'm driving passive subs with a combo of a professional digital DSP and the amp board of the Panasonic. Digital pre/eq/crossover/dither power amp in one box. The digit amp is very good to drive the woofer.

Vic · « **Reply #11 on:** 24 Dec 2003, 02:49 am »

Quote from: csero

Quote from: JackStraw

Do you mean that you're driving a passive sub with the Panasonic? This would definitely be an interesting use of the "Party Mode" that I've read about on that thread. Not exactly what I meant, but interesting nonetheless.

Not exactly. I'm driving passive subs with a combo of a professional digital DSP and the amp board of the Panasonic. Digital pre/eq/crossover/dither power amp in one box. The digit amp is very good to drive the woofer.

Your not using Bag Ends ELF processor? I tride powering my S18E without the processor using an active crossover instead and the results were not at all satisfying. I'm currently powering with a Carver-Pro ZR1600 which replaced my more powerful QSC PLX2402.