Let’s talk subwoofers...

[VanJerry]

1. Sound

2. Depth

3. Output

4. Size

5. Finish

What attracts me to Ascend is accuracy and the integrity to make things sound as they really are.

For me a great deal that informs that perception of reality is depth. So I'm particularly looking forward to Dave's achievement in something like recreating the presence of wind in the trees. In this I'd trust to Dave how low such a sub would need to be able to go but I don't imagine it would require loads of sound pressure. So if it's about trade-offs I'd say output would be my big one.

[EDIT: Yikes on the following! Explained in my next post.]

And a microphone enabled sub - absolutely, if it helps to achieve the high standard at a lessor cost in the end. Whatever a receiver or a computerized bass management system could do is "after the fact" requiring the sub to have an expensive "head room" of extra output across the board for something else to subtract. Dave controlling this allows him the fullest latitude to leverage innovation over expenditure. Because whatever happens has to happen under a certain price.

[davef]

Hi Dallas,

I'd love to hear your take on the extra technology companies like SVS throw into their amps.

By no means is this a knock against SvS, but I would like to know precisely what you mean with regard to the "extra technology companies like SvS throw into their amps", and how you have arrived at this perception?

Thanks in advance!

[davef]

Another feature that might be worth consideration would be a built in microphone with auto EQ. Otherwise known as automated room optimization.

Not a fan of this feature being integrated into the subwoofer. It is the wrong place to put these components.

For Auto EQ to function properly, it must absolutely be done in the digital domain. This means that the subwoofer must convert the analog signal to digital, process the digital signal, convert the digital signal back to analog and then amplify it and send it to the woofer. Anytime you convert an analog signal to digital (and then back again -- even with the very best converters), you disrupt signal integrity and sound quality takes a hit. This is precisely why so many of our customers prefer to run their "digital" AVRs in pure direct mode because, in most circumstances, this bypasses all digital processing -- keeping the source purely analog.

Many AVRs and pre-processors now have highly functional Auto EQ features, and this is where this type of processing should be handled.

An example of Auto EQ being handled by the receiver or processor:

Scenario 1: Digital source to a digital input on the receiver: Digital signal comes in, various processing occurs such as bass management and auto room EQ. Digital signal is then converted to analog and sent to the amp and subwoofer.

This offers only 1 digital conversion and offers the best possible sound quality for a digital source.

Scenario 2: Analog source to an analog input on the receiver: Analog signal comes in, it is converted to a digital signal, various processing occurs such as bass management and auto room EQ. Digital signal is then converted to analog and sent to the amp and subwoofer.

This offers 2 digital conversions and the integrity of the original analog source has been somewhat compromised, but with the benefit of many additional functions that can improve the listening experience (various listening modes, bass management, auto room EQ)

Scenario 3: In pure direct mode, the analog signal comes in and the same signal is then sent out to the amp and sub. No digital conversions / processing take place thus keeping the analog signal fully intact.

If we were to then add auto room EQ to the subwoofer, the analog signal coming from the receiver would once again be converted to the digital domain, processed, and then converted back to analog. Too many transforms for my tastes, and while built in auto EQ at the subwoofer is a nice feature and a major selling point for many consumers, I am after audio purity and accuracy.

The proper way to implement this is at the receiver or processor and we are now starting to see this feature in a major way.

In an ideal world, the subwoofer would receive the original digital signal from a digital source, process room EQ, convert to analog and "woof woof" etc. Best of both worlds here -- problem is that long optical/digital cable runs are very problematic and the major advantage of using subwoofer, ideal room placement, would be lost.

One minor detail about what we are doing -- every component of the subwoofer is being custom designed by us, including both the amplifier and pre-amplifier sections of the plate amp. This is no ready built subwoofer plate-amp whereby a subwoofer manufacturer simply tweaks a few caps and resistors on the preamp section to adjust EQ and then calls the amp their own custom design (such as BASH amps and many others out there). We are designing all of the various filters and functionality in-house (and having fun with it too -- been a few years for me but feels good to get back to my roots although my version of SPICE is a bit out-dated these days

[davef]

And a microphone enabled sub - absolutely, if it helps to achieve the high standard at a lessor cost in the end. Whatever a receiver or a computerized bass management system could do is "after the fact" requiring the sub to have an expensive "head room" of extra output across the board for something else to subtract.

Incorrect, regardless of where the EQ'ing occurs, be that at a receiver, processor or subwoofer, it is always going to be at a stage before signal amplification. The demands on the amplification section remain the same regardless; the same amount of headroom will be required regardless of where the processing takes place.

Whatever a receiver or a computerized bass management system could do is "after the fact"

Taking this even further, implementing this at the subwoofer itself is as far "after the fact" as you could get, since the processing occurs on the source material being sent to the sub, which is the last component in the chain.

An interesting system would be real-time room EQ processing, such that the subwoofer used an active microphone and constantly monitored the room response and then continually sent corrections to the subwoofer's power amp (a servo based active room EQ system). Something like this could be done and it would assure maximum performance at all times and at all volume levels. Theoretically, it could even turn itself down if it sensed specific high-frequency components such as rattles or resonance’s caused by the room. However, implementing something like this would be expensive and the reality is that it wouldn't really be needed -- since the response of your room and your subwoofer won't change unless you re-arrange the room or change the location of the subwoofer, in which case you would simply re-EQ at the receiver...

Fun to think about though and it would not surprise me at all if we see this in a high-end subwoofer a year or two from now. Maybe I should patent the idea

[buddhadas]

Thanks for the newest bone on the sub Dave! Also, your description of the digital to analog actually makes sense to me, no small accomplishment!

Thanks,

Jim

[GirgleMirt]

Hi Dave

Like everybody else SQ #1. Music is priority vs HT for me so SQ definitely more important than 10hz or crazy output.

finish would be last. As most Ascend products I think bang for the buck should be the first consideration, and since finish is purely aesthetic, it would be last.

extension: Not all that important. I mean, as long as it's decent, I'd probably be ok with it. It is a sub after all... Also question, isn't a cd response 20hz-20khz? Whereas there's no info below 20hz and above 20khz? How low does DVD go?

output: Again, relatively the same as extension.

size: Smaller would be nice, but again, if compromises must be made to performance, I'd rather it'd be a bit larger...

One aspect not mentioned, personal opinion, I don't like the look of say the HSU turbo. A box with two huge ports on top of a box with big pipes linking the two, with a big footprint... Really not my thing. So I guess what I'm asking is not to make a monstrous looking sub, bit of aesthetics is more important than type of finish for me In my case, I'd like smaller footprint and maybe higher, but that's not so important.

One thing I learned with my sealed sub, you want a flat FR... Sealed, that probably means EQ or servo, but I'll leave the designing to you

One note: one sub always seem to have issues in room. peaks. nulls. Two subs reduces these issues, and I remember reading a paper where someone experimented with multiple subs and found that going over 4 wasn't really worth it. Multiple subs also increases output. So could a multiple sub solution be envisaged? Maybe modular amp. 1 external amp powering 1 or 2 sub, allowing saving $ by having 1 amp in each sub. Which would allow to 'cheaply' buy 2 subs... Or maybe 1 'processor', + amps, + sub modules, allowing 4...

So instead of selling 1 sub for 800$... maybe make a solution of selling 2 for 800$ which would probably give better results in room in terms of peaks/nulls. A modular solution.

Can't wait to see what you come up with! Words like Servo or digital amps are floating in my mind... So many questions, can't wait to see what's cooking!

[VanJerry]

Hi Dave,

Ugh! I lamely tried to use quotes to get away with my lazy use of language but I would have been better off staying well clear of amateur engineer speak the way I did and you are quite right to correct how it came off. But this was indeed what I had in mind:

An interesting system would be real-time room EQ processing, such that the subwoofer used an active microphone and constantly monitored the room response and then continually sent corrections to the subwoofer's power amp (a servo based active room EQ system). Something like this could be done and it would assure maximum performance at all times and at all volume levels. Theoretically, it could even turn itself down if it sensed specific high-frequency components such as rattles or resonance’s caused by the room. However, implementing something like this would be expensive and the reality is that it wouldn't really be needed -- since the response of your room and your subwoofer won't change unless you re-arrange the room or change the location of the subwoofer, in which case you would simply re-EQ at the receiver...

Fun to think about though and it would not surprise me at all if we see this in a high-end subwoofer a year or two from now. Maybe I should patent the idea

I should have just spelled it out but I was awkwardly - no... I think it was disastrously - trying to just hint at Rythmik's approach rather than specifically mentioning them in this thread. Basically, because I would expect something surprising from Ascend when it came to achieving the kind of signature affordable high standard result people have come to expect I was just speculating about one such way: going a few steps better than existing servo designs. Cutting out active circuits. Maybe including something like an on the fly mic-enhanced direct servo where the mic would act as a second voice coil at the remote listening position to modifying the corrections the coil on the subwoofer would be feeding back to the amplifier. I didn't know if this would be expensive. Looks like it is.

[dallas]

Hi Dallas,



By no means is this a knock against SvS, but I would like to know precisely what you mean with regard to the "extra technology companies like SvS throw into their amps", and how you have arrived at this perception?

Thanks in advance!

I don't mean it as a knock either, just in case anyone perceived my post that way.

What I am referring to is all the EQ'ing features. On the bottom end amps from HSU and SVS, axiom, etc, you are lucky to get a one dial each for gain and phase.

As you move up the product line to you start getting some features (and spending some bucks) By the time you hit the ultra with SVS for instance, you have no less than 8 dials and 3-4 toggle switches, plus extra input options with XLR. "Extra features" like PEQ, room correction, etc.

(FWIW, I have a PB13Ultra upstairs sitting in a box that i haven't got around to plugging in yet. This is my first sub. I am by no means an expert, so if my questions sound uneducated, there is good reason for that... :-) However, I did work in stage audio and lighting for a number of years, I learned to recognize quality sound when I hear it. Thus far, the only thing I can say ascend speakers take a back seat too is an orchestra in a hall with very good acoustics. Sorry dave, but nothing anyone can ship via UPS can produce the beautifull sound of a good symphony hall and a full orchestra. :-)

[dallas]

One aspect not mentioned, personal opinion, I don't like the look of say the HSU turbo. A box with two huge ports on top of a box with big pipes linking the two, with a big footprint... Really not my thing. So I guess what I'm asking is not to make a monstrous looking sub, bit of aesthetics is more important than type of finish for me In my case, I'd like smaller footprint and maybe higher, but that's not so important.

Uhg, I hear you man. That thing is possibly the ugliest contraption ever. I'm sure there's a subculture of people who love it, but to me it looks like one of these teeny-bopper rusty cars with a 2000 dollar rear spoiler bolted to it. I'm sure it works well, but it's just ugly. My wife would tell me to keep it in the garage with my other wet-dry vac!

Not to beat down HSU, I hear they make excellent subs, and I'm sure this one is no slacker. I'm talking purely about the looks of the pipes/turbocharger.

[drewface]

One minor detail about what we are doing -- every component of the subwoofer is being custom designed by us, including both the amplifier and pre-amplifier sections of the plate amp. This is no ready built subwoofer plate-amp whereby a subwoofer manufacturer simply tweaks a few caps and resistors on the preamp section to adjust EQ and then calls the amp their own custom design (such as BASH amps and many others out there). We are designing all of the various filters and functionality in-house (and having fun with it too -- been a few years for me but feels good to get back to my roots although my version of SPICE is a bit out-dated these days

was the digital amp you mentioned working with a few weeks ago (you were comparing to the ICEpower amps, i believe) related to this sub development?

also, when you decide on which of the three designs you're going to move forward with, will you be sharing any information on the differences in your 3 main prototypes with us? i think it would be very interesting to see what sort of things you had in mind, and what didn't make the cut in the final decision.