Question for those with external subs

cjf

Member
Nov 19, 2012
323
1
18
#61
Hi there are many that have it

Here are some examples View attachment 38054
Hello,

Wont most if not all of these boxes result in additional layers of AD/DA conversion occurring after the PreAmp and before the Amps? Its seems most of the boxes I have found will result in Downsampling whatever came before them in the signal chain nulling out any subjective and possibly preferred "flavors" applied by a fancy DAC and Pre-Amp Upstream of them.

One thing I have gathered thus far is that I want all this DSP/X-Over stuff done before the DAC to maintain the sonic signature of the DAC and everything else after it. Without this possibility I will most certainly just roll without a Sub and live with 30hz bass forever :eek:
 

awsmone

Active Member
Apr 7, 2014
1,102
17
38
Canberra Australia
#62
If servo subs are the answer then I'm curious why the more popular Sub brands like JL,Magico, Wilson, SVS, B&W..etc are choosing to not use that technology? I found a handful of Servo based brands (Rythmik, Velodyne, Paradigm) and I'm sure there a others but for whatever reason its seems very few of the higher end music centric systems (just looking on this forum as an example) seem to not be using them. Why do you suppose that is and what are the negatives against Servo based Subs?

If delay, of any kind, isn't a serious problem then why does it seem like such a popular topic with lots dedicated text on how to address/combat it when blending Subs with Main towers? Why are these people not just buying Servo Subs and calling it a day?

I obviously don't know which is why I am asking the questions.
Good questions

Group delay isn’t just solved by servo subs

Early in the piece they were the answer/improvement to group delay with drivers around


Newer high end subs tend to have massive magnets an voice coils

It’s all about speed of reaction is not specific to a topology

As mentioned earlier it depends what sort of delay your talking about see posts above
 
Jul 25, 2012
2,554
0
36
NY
#64
To get the most out of the music, different slopes may be needed for some bass deficient or other bass heavy recordings.
 

awsmone

Active Member
Apr 7, 2014
1,102
17
38
Canberra Australia
#65
I use the JL Audio CR-1 crossover to blend in the mains really well. I use 2 different slopes.... one for the mains, one for the subs. It's very versatile!
I can understand this may well work but will give different phase shifts which may be what your system needs

As I recognise what often the rule books say doesn't work out in practice
 

Folsom

VIP/Donor
Oct 26, 2015
2,672
21
38
Eastern WA
#66
If servo subs are the answer then I'm curious why the more popular Sub brands like JL,Magico, Wilson, SVS, B&W..etc are choosing to not use that technology? I found a handful of Servo based brands (Rythmik, Velodyne, Paradigm) and I'm sure there a others but for whatever reason its seems very few of the higher end music centric systems (just looking on this forum as an example) seem to not be using them. Why do you suppose that is and what are the negatives against Servo based Subs?

If delay, of any kind, isn't a serious problem then why does it seem like such a popular topic with lots dedicated text on how to address/combat it when blending Subs with Main towers? Why are these people not just buying Servo Subs and calling it a day?

I obviously don't know which is why I am asking the questions.
Well, some amps are coming closer to servo control.

The tech in drivers has improved. They can be pretty darn good in convention subwoofers. But my point being if you're under the impression a few miliseconds is the end-all, then servos are there to aid you.

But the biggest function is the non-necessity due to frequency range. Magico speakers and many other big time ones already play a pretty full range. The subwoofers only kick in at the extreme of the spectrum, and simply put, could have almost any group delay you can imagine and make no difference to the experience. In some cases it might make some speakers look embarrassed. Mismatches could be a problem, since a servo is going to show you problems in your stereo where is the problems create a synergy with other components. Again, overall at the extreme it is really just about being able to move enough air to keep up with dynamics.

For example the Q subwoofer paired with the Q line is only expected to play the 15-24hz area, with the fullrange speakers. It's a beast that can play extremely loud and clean. But even if it had truly bad group delay, you wouldn't be hearing it. Hell, you don't even really "hear" that frequency range so much as feel it.

Where as if you're trying to integrate subwoofers in with bookshelves, or even to play up to a midrange, that's another story. In those cases articulation start becoming a big factor, because you're blending into the music. At this point if you want big displacement with musical ability, it's smart to look at servos.

I suspect many manufacturers prefer not to spend the time and money on servos, when they can sell you something else that costs them less overall. But some of them may use servo technology and utterly avoid trying to market it, since it's not a buzz word or super easy to explain.

Overall I don't think there is anything wrong at all with conventional subwoofers. It all really depends on use etc. BUT if you're trying to "solve" group delay and such, they're a ticket to getting much closer. Again, if it was such a massive problem then maybe you'd see more servo based subs.



I have yet to see anything in any of these texts that can suggest you do anything but sit on the subwoofer, or use a full DSP for all the signal. One of them sells equipment, the other won't happen. People post this stuff for the same reason they do everything else, they want to be heard, look smart, whatever... And the ideas are simplistic enough they can feel like they're reached some sorta unknown goal that they can understand. But how many people do you see practicing all of these "ideas"? (many of which are not plausible, as we found out) You don't hear about, you only read about it. Where are all of the testimonials?

For home theater people all the DSP stuff makes life simple. They don't play around with moving speakers to sound just right, they design a room and DSP it to work with whatever they feel like should be working. (which does not provide the best results, the ability of a DSP is more limited than people will admit) They're the same group that thinks all DAC's sound the same. This crowd will take easy solutions over ultimate fidelity.
 

Bruce B

WBF Founding Member, Pro Audio Production Member
Apr 26, 2010
6,602
15
38
Seattle, WA
www.pugetsoundstudios.com
#67
I would argue you can never fix a recording no matter what you do. Tone controls are for pleasure, not for accuracy, and any attempt to fix anything is just an exercise in futility.
I can fix anything!!!



MP3.JPG
 
Nov 3, 2014
405
0
0
#68
If servo subs are the answer then I'm curious why the more popular Sub brands like JL,Magico, Wilson, SVS, B&W..etc are choosing to not use that technology? I found a handful of Servo based brands (Rythmik, Velodyne, Paradigm) and I'm sure there a others but for whatever reason its seems very few of the higher end music centric systems (just looking on this forum as an example) seem to not be using them. Why do you suppose that is and what are the negatives against Servo based Subs?

If delay, of any kind, isn't a serious problem then why does it seem like such a popular topic with lots dedicated text on how to address/combat it when blending Subs with Main towers? Why are these people not just buying Servo Subs and calling it a day?

I obviously don't know which is why I am asking the questions.
I don't think servo subs are necessarily the answer, and I agree with your skepticism. I do think getting proper timing and also phase alignment in the crossover region are important and helpful.

But, the really biggest issue by far is frequency response and ringing caused by room modes. Frequency response in typical listening rooms exhibits peaks and troughs of many dB due to room modes. I have measured narrow peaks/troughs as much as +-15-20 dB in some rooms down to +- 7 dB in others. Needless to say, this is quite audible. DSP EQ is outstandingly helpful in largely correcting this. The sound is dramatically improved.

Multiple subs properly deployed also can be quite effective, especially coupled with DSP EQ. Passive treatments are highly questionable, even if huge and ungainly, and often lack effectiveness in the bottom octaves. I deem passive treatments a waste of time, money and effort in the bass below 100Hz.

So, I think DSP EQ gives the biggest sonic payoff by far. Pragmatists like me might find that sufficient, and it is the easiest to do, relatively speaking, with the wide range of tools available, sometimes built into subs, like JL. I use Dirac Live EQ instead with my single JL f113, rather than JL's EQ. And, I am happy to leave it at that. But, I concede that results could be tweaked and further enhanced somewhat with multiple subs and phase alignment, requiring much effort and careful measurement via mic.
 
Nov 3, 2014
405
0
0
#70
My playback system in simple terms is a Win 7 PC feeding via USB an Exasound e28 DAC, then driving my amps and sub directly in 7.1. In the PC, JRiver is my library/player system together with the Dirac Live VST plugin(7.1). Bass management xovers are done by JRiver. Speaker distances and channel levels were calibrated by Dirac via mic along with Room EQ filters. There is also HDMI output to my HiDef monitor and a Cablecard tuner via Ethernet for cable TV.

There is no preamp or Mch processor in my system. JRiver/JRemote/Dirac handle all that quite well, including master volume control.

Playback sources are mainly Mch classical SACDs or BDs ripped to my 54TB NAS or from CD/DVD/BD optical drives in the PC.
I am quite happy with my sound and video. I have not tweaked it for years and I have no plans to do so.
 

Mark Seaton

WBF Technical Expert (Speaker & Acoustics)
May 21, 2010
319
2
18
42
Chicago, IL
www.seatonsound.net
#71
For example the Q subwoofer paired with the Q line is only expected to play the 15-24hz area, with the fullrange speakers. It's a beast that can play extremely loud and clean. But even if it had truly bad group delay, you wouldn't be hearing it. Hell, you don't even really "hear" that frequency range so much as feel it.

Where as if you're trying to integrate subwoofers in with bookshelves, or even to play up to a midrange, that's another story. In those cases articulation start becoming a big factor, because you're blending into the music. At this point if you want big displacement with musical ability, it's smart to look at servos.

I suspect many manufacturers prefer not to spend the time and money on servos, when they can sell you something else that costs them less overall. But some of them may use servo technology and utterly avoid trying to market it, since it's not a buzz word or super easy to explain.

Overall I don't think there is anything wrong at all with conventional subwoofers. It all really depends on use etc. BUT if you're trying to "solve" group delay and such, they're a ticket to getting much closer. Again, if it was such a massive problem then maybe you'd see more servo based subs.
Most don't realize that the analog filter in the subwoofer to limit response to below 30Hz automatically introduces huge amounts of group delay (more with higher order filters). At the same time, exceedingly few speakers have anything close to constant group delay. Different crossover frequencies, topology, and low frequency enclosure behavior all affect what the group delay of the speaker is by the time we get down to the subwoofer. There is no correct delay time for every speaker you will cross over to. Now add in the room's impact on the low frequency roll off of the main speaker, and you have even more of a moving target. As always, it's important to keep an issue in context. For feedback based systems, I don't recall any of these systems eliminating group delay. They *may* result in correcting the relative phase response (=making group delay constant), depending on the implementation and design target, but that is not the same as eliminating group delay.
 

Folsom

VIP/Donor
Oct 26, 2015
2,672
21
38
Eastern WA
#72
There is no such thing as a brick wall in audio, Mark. So what is your point? You can reduce group delay, but it won't go away completely until the subwoofer can warp through time and space, so why discuss it as a binary function? And incase you missed it, this is about group delay from impulse response (as in what is important for a subwoofer).

Feedback can get help get closer to linear phase (it's actually linearly scaling phase shift). I think that is what you are saying. But feedback can also wrangle group delay to be shorter in impulse response. It really depends on the design.


Also not all amps use an analog filter (I'm not even sure which do). It makes more sense to use an active one, where you can exert more concern about drifting delay. And you might be surprised about GD with the order of filters. Linkwitz has shown it doesn't get wild, and isn't even particularly audible.
 
Last edited:

Mark Seaton

WBF Technical Expert (Speaker & Acoustics)
May 21, 2010
319
2
18
42
Chicago, IL
www.seatonsound.net
#73
There is no such thing as a brick wall in audio, Mark. So what is your point? You can reduce group delay, but it won't go away completely until the subwoofer can warp through time and space, so why discuss it as a binary function?

Also not all amps use an analog filter (I'm not even sure which do). It makes more sense to use an active one, where you can exert more concern about drifting delay. And you might be surprised about GD with the order of filters. Linkwitz has shown it doesn't get wild, and isn't even particularly audible.
Most who have attempted to study it have found group delay to be well behind other more important sonic qualities, if audible at all when less than 1 period. I wasn't suggesting that we need zero group delay, I'm pointing out that speakers have their own group delay from top to bottom of the frequency range, and likely more than most realize. Most efforts that correct phase response do so by delaying the rest of the range to match the latest sound produced. This results in a latency which affects the ideal matching through crossover such that the time of arrival is more than the physical distance would suggest. Any analog or non-FIR filter outside of 1st order and heavily overlapped 2nd order filters add group delay. Analog doesn't have to be speaker level, any preamp level active crossover like the Pass, Bryston, or Marchand units all have inherent group delay introduced.

In use we really just need a useful phase match and to keep group delay offsets reasonable with respect to period/frequency. Even an ideal L-R crossover will result in increased group delay on the woofer, but that relative phase response allows proper summing. The problem to solve in integration of speakers and subwoofers is that we have multiple other factors such as physical offsets, woofer inductance, any latency in the subwoofer amp, and then the speaker's group delay around the crossover. In most cases this requires acoustic measurement in-room to really get it right, else it's more a matter of luck and trial and error.
 

awsmone

Active Member
Apr 7, 2014
1,102
17
38
Canberra Australia
#74
I tend to agree with Mark

We seem to have got side tracked onto group delay, rather than delay, or phase delay

I also agree that phase matching as much as is possible, is of much greater benefit

Finally

The issues of the room and room modes is several orders of magnitude bigger problem, than groups delay audibly
Equalisation can clearly help here, though multiple subwoofers are better in general. But even then the dimensions of the room will still dictate room modes.
 

Folsom

VIP/Donor
Oct 26, 2015
2,672
21
38
Eastern WA
#75
Well I think that makes you (awsmone), Mark, and I in agreement.

I've been talking about group delay, but not promoting caring about it. (if you do buy a servo sub)

There simply is no substitute for moving the subwoofer around and twisting the phase knob. Even DSP's have massive limitations, what measures well can sound awful. You're better off get very close then using one to improve some of what you couldn't get perfect. The people who just put a subwoofer wherever and try to DSP it into working, don't care about SQ.

(Mark, I don't think crossover discussions are going to help the thread much, but different designs do trade off phase vs. distortion etc, you can do a lot)
 

awsmone

Active Member
Apr 7, 2014
1,102
17
38
Canberra Australia
#76
+1

Couldn’t agree more, massive Eqing is a gift wrapped pig.

Optimising as much as you can first before eq is best, multiple subs fill in a lot of the bumps and pits

My suggestion for Music is to centre eqing on pitch not the room

And totally agree what looks good on the equalised measurements doesn’t often seem to be the best for SQ, which I find totally frustrating
 
Nov 3, 2014
405
0
0
#77
+1

Couldn’t agree more, massive Eqing is a gift wrapped pig.

Optimising as much as you can first before eq is best, multiple subs fill in a lot of the bumps and pits

My suggestion for Music is to centre eqing on pitch not the room

And totally agree what looks good on the equalised measurements doesn’t often seem to be the best for SQ, which I find totally frustrating
My sympathies. I have used DSP EQ for over a decade now. Various EQ tools, but usually always with the default target curve, so no tweaks and delivering measurably smooth response. Friends have also tried it on my recommendation or on listening to my system. Our bottom line is we would never, ever be without it. One of the greatest breakthroughs in audio history.
 

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