Opinion needed on my SVS Ultra speaker and possible changes for the surrounds

Glenn S

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Preamp, Processor or Receiver
av processor: Onkyo TX-SR706
Main Amp
main amp: ATI AT1506
Front Speakers
front L/R speakers: Chane A5rx-c
Center Channel Speaker
front center speaker: Chane A2.4
Surround Speakers
surround speakers side/rear: Pioneer in-wall
Subwoofers
subs (3): (1) DIY 15" sealed & (2) DIY 18" Fi IB
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tv: Panasonic TC-P55VT50 plasma
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remote: Harmony 700
MJP,
Yes, I agree with your point.
I was letting Talley know that a speaker having great bass output is a separate issue from bass management between multiple drivers.
 

Glenn S

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Joined
Jan 6, 2018
Messages
25
Location
Beckely WV
More  
Preamp, Processor or Receiver
av processor: Onkyo TX-SR706
Main Amp
main amp: ATI AT1506
Front Speakers
front L/R speakers: Chane A5rx-c
Center Channel Speaker
front center speaker: Chane A2.4
Surround Speakers
surround speakers side/rear: Pioneer in-wall
Subwoofers
subs (3): (1) DIY 15" sealed & (2) DIY 18" Fi IB
Video Display Device
tv: Panasonic TC-P55VT50 plasma
Remote Control
remote: Harmony 700
And to Talley's last point about sending all bass to the front two main speakers...
that is much better than having five full range speakers each with discrete bass. Although the best placement for the front main speakers is not usually the best placement for the sub drivers. That is why most systems use separate subs, they can be placed nearer to their ideal location.
 
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Matthew J Poes

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Ok and why wouldn't the xmc-1 with dirac be able to handle this? You set the front 2 speakers to full... set the back to small... bass is routed from the backs to the front. LFE is then sent to front two mains. The only trick would be to use something like minidsp to send to the front 3

but using dirac/xmc-1 you still have bass management... the JTR speakers alone are more capable of low end then most subwoofers including the PB-16 ultra. and you have two...

Ok so going back to the notion of a complete set of full range speakers for mains and all effects speakers, I am saying that you would ideally want to make use of their full range capabilities in a system. below 100hz, certainly by 80hz the bass is omnidirectional and in the room, fully steady state. This means two things, 1) the bass will have hit all the barriers in the room long before it ever reaches your ears, and 2) the physics of human hearing will prevent us from locating LF sources. What that means is that we don't need to worry about the directional cues of low frequencies, there aren't any. Instead, we need to worry about the sound quality of LF's which are almost entirely a function of the interaction with the room. Because the best way to address LF smoothness is with lots of LF sources, having full range surround speakers could be a good thing. It's like having subs on your walls. The problem is, the way in which you would send surround signals and the way in which you would send bass signals is not going to be the same. There are two proper ways to setup the LF sources, neither of which is possible with any current bass management built into any processor.

Method 1) The Geddes and Harman approach, in which the bass is summed from all channels into its own LF channel and combined with the LFE channel. This is then sent discretely to each LF source, which is individually aligned, but globally EQed. Related to method 1 are some methods that rely on eqing individual subs, but none the less, the overall approach integrates the bass signal by maximally exciting all modes in the room and eqing flat. Delay isn't critical necessarily for achieving this but plays a role. The right delay for a LF source does not match its physical distance. This is the crux of the problem for any of the current bass management systems. The bass that is being redirected to the speakers can't have the delay modified for the bass signal separate from the surround signal before being mixed and sent to the surrounds. The delay is done on the final channel, not in the input matrix (where it would need to be addressed). As such, it's generally better to redirect the bass away from the surrounds to your separate subwoofers (though running the mains as full range is still a good idea of they can handle it. The delay is a non-issue for them given their placement and the ability to adjust the LF+LFE channel).

Method 2) The Bass Array approach. Since the surround speakers are now mounted on the walls and are full range sources (If they aren't mounted on the wall they need to be for this to work), you can delay the bass signal going to the rear surround speakers to cancel the length mode. This is not possible for the same reason as above (though the delay is different in this approach, much longer). This is the approach I'm most interested in testing myself. It's advantage is that the bass can be made to be even smoother, the negative is that you have free space bass. You are canceling all modes, its like canceling all reflections, so the bass sounds like it is outside, rather than in a room. I've discussed this idea with Dr. Geddes and a few other experts who feel that its an approach worth studying, but that people might find the sound objectionable. I've done some really basic proof's of concept on this idea, but my next step is the 10" surrounds I'm working with.

While your emotive is among the more flexible systems, it unfortunately doesn't have the kind of DSP capabilities needed to do it as I'm discussing above. It still was designed around the assumption that the sub or subs would handle the bass or that if the main channels are run full range, they get the bass discretely.

I'll also add that if I was designing a system's bass management to be completely ideal, I would allow overlapping bass sources to operate up into the transition zone at and above fs, but I would allow stereo bass operation down to 80hz. Below 80hz I would have complete summation. I don't feel I have a full grasp of how our hearing transitions it's directional capabilities below 700hz. I know that by this point it uses phase cues only and not intensity differences. I also know that as it gets closer to 100hz we become increasingly incapable of detecting the phase differences until we simply can't at all. That is true outside. In a room the bass is also hitting all the barriers so what we hear as a source isn't the sub but the room. That further muddles our ability to detect the location of the LF source. My guess based on what I've read is that it would be detectable down to maybe 200hz easily and become increasingly difficult, but that the exact frequency at which we couldn't hear at all would depend on our hearing, our system setup, and our room's size and acoustics. I can localize my rear subs if I set the low pass filter above 80hz, pretty easily, so I feel like it makes sense to allow stereo bass above that point. My guess is that you won't be able to detect in front or behind, but you might detect to the left or to the right. The DBA approach sets the rear sub's at a reduced level, which should also help keep the bass sounding more in front of us at these upper bass frequencies between 80hz and say 150hz.
 

Matthew J Poes

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MJP,
Yes, I agree with your point.
I was letting Talley know that a speaker having great bass output is a separate issue from bass management between multiple drivers.
Sorry about that Glen, I misunderstood what you said.

Yes for most people using any of the readily available theater processors, best to just redirect bass. I've been talking with some folks about the idea that I think bass management is fundamentally flawed in all current theaters because of certain assumptions being made which are incorrect. I had thought about writing about this, but it was pointed out to me that this preferred approach of mine, while technically superior, is far beyond what the average person can do. That if we look at the design of a processor as meeting the needs of 80 or 90% of all users and not having design capabilities that could make performance worse for them, the current approach is best. Basically its a best possible approach knowing that most people are going to setup their rooms a particular way.

It is my sincere hope that companies like Dirac can, in the future, develop a DSP correction scheme that can handle LF's the way I have discussed. However, going along with this is a need for more full range high output speakers for all channels (or at least the mains and surrounds. You could then use surround speakers to do more than just reproduce effects. They can also serve as LF sources that improve the LF smoothness in the room. In fact, you could incorporate the same techniques that one of Harman's companies is using to create active room acoustics. I believe it could be done without the addition of live microphones in the room, but I know the current approach they use relies on microphones at the first reflection points. It uses measurements of this to feed a special delayed and inverted signal to a set of effect speakers to change the RT60 of the room to whatever you want it to be. Now imagine active bass traps, no reason why a surround or sub in a corner can't do the same thing in the same way. All of this can be incorporated into DSP built into a processor, the problem is you must know the speakers dynamic capabilities to do this and not overload the speakers at low frequencies.
 

Talley

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Excellent post... thanks for taking the time. Let me also add my main concern over localizing bass.... vibration. My room is in the second story of my house. My house is build on a 2x6 tongue and groove subfloor and are on 2x12's on 12" centers. Vibration in itself creates frequencies of not just the bass note. This is the main reason people think they can localize the source.

I completely agree with you... the bass in your room is mostly your room response. It's like living in a ported sub box (ported for most rooms because most are never "100% sealed"). Downstairs... my room is the same size as the theater room... I can play a 16hz note... a note that I cannot even hear... but the vibration of the source is at the most intensity... I can tell what side of the room the subs are on from my downstairs. By running all my speakers in small mode and the two subs in dual mono then this is the summed frequencies of all channels bass and LFE into one.

Now... obviously I "could" run those JTR full range and as subs... they certainly could handle it but the biggest advantage of subs is the ability to locate them in a better position than what the best location of the speaker is. I know talk and discuss alot... but to me it's all about learning and theory building/testing and such. I'm very analytical.

I have about 90% faith in the fact having subs for the LFE would be the only way to go.... even if you had full range speakers with subwoofer frequency response capability. That would be like using bookshelfs for the front and full range for rear and sending the bass to the rear... seems stupid. There is a dedicated LFE channel... it requires it's own speaker.
 

Talley

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Sorry about that Glen, I misunderstood what you said.

Yes for most people using any of the readily available theater processors, best to just redirect bass. I've been talking with some folks about the idea that I think bass management is fundamentally flawed in all current theaters because of certain assumptions being made which are incorrect. I had thought about writing about this, but it was pointed out to me that this preferred approach of mine, while technically superior, is far beyond what the average person can do. That if we look at the design of a processor as meeting the needs of 80 or 90% of all users and not having design capabilities that could make performance worse for them, the current approach is best. Basically its a best possible approach knowing that most people are going to setup their rooms a particular way.

It is my sincere hope that companies like Dirac can, in the future, develop a DSP correction scheme that can handle LF's the way I have discussed. However, going along with this is a need for more full range high output speakers for all channels (or at least the mains and surrounds. You could then use surround speakers to do more than just reproduce effects. They can also serve as LF sources that improve the LF smoothness in the room. In fact, you could incorporate the same techniques that one of Harman's companies is using to create active room acoustics. I believe it could be done without the addition of live microphones in the room, but I know the current approach they use relies on microphones at the first reflection points. It uses measurements of this to feed a special delayed and inverted signal to a set of effect speakers to change the RT60 of the room to whatever you want it to be. Now imagine active bass traps, no reason why a surround or sub in a corner can't do the same thing in the same way. All of this can be incorporated into DSP built into a processor, the problem is you must know the speakers dynamic capabilities to do this and not overload the speakers at low frequencies.

Yes... I agree. This would be the most ideal solution. Now it just takes someone like you... with some smart programmers to develop your own room correction software. One that fits the 10 percenters... like you and me.
 

Matthew J Poes

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Excellent post... thanks for taking the time. Let me also add my main concern over localizing bass.... vibration. My room is in the second story of my house. My house is build on a 2x6 tongue and groove subfloor and are on 2x12's on 12" centers. Vibration in itself creates frequencies of not just the bass note. This is the main reason people think they can localize the source.

I completely agree with you... the bass in your room is mostly your room response. It's like living in a ported sub box (ported for most rooms because most are never "100% sealed"). Downstairs... my room is the same size as the theater room... I can play a 16hz note... a note that I cannot even hear... but the vibration of the source is at the most intensity... I can tell what side of the room the subs are on from my downstairs. By running all my speakers in small mode and the two subs in dual mono then this is the summed frequencies of all channels bass and LFE into one.

Now... obviously I "could" run those JTR full range and as subs... they certainly could handle it but the biggest advantage of subs is the ability to locate them in a better position than what the best location of the speaker is. I know talk and discuss alot... but to me it's all about learning and theory building/testing and such. I'm very analytical.

I have about 90% faith in the fact having subs for the LFE would be the only way to go.... even if you had full range speakers with subwoofer frequency response capability. That would be like using bookshelfs for the front and full range for rear and sending the bass to the rear... seems stupid. There is a dedicated LFE channel... it requires it's own speaker.

Well then Talley, time to add a second layer of T&G to those floors!

In all seriousness, while vibrations, resonances, etc. are a common part of any room, I think they need to be addressed. It was largely my dream to built a dedicated sound proof theater and listening room because I wanted to build a room that was acoustically ideal. I don't want the room producing any non-linear distortions, resonating sympathetically, etc. Same with these vibrations, I want to control them. I built my riser so it wouldn't vibrate as easily to avoid any chance of detecting the sub that sits on it due to resonances or vibrations. As I mentioned, when I low pass it below 80hz its fine, you can't detect it.

I paid so much attention to unwanted resonances that I even bought wall sconces that use resin lenses that I then modified to have a tighter fit when locked in place (cork gasket). Everything mounted to the wall has rubber or felt bumpers to create tension with the wall and avoid bad noises.
 

Matthew J Poes

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Yes... I agree. This would be the most ideal solution. Now it just takes someone like you... with some smart programmers to develop your own room correction software. One that fits the 10 percenters... like you and me.

Well bass management is separate from room correction. Dirac doesn't do any form of bass management. They get convolved a lot because both are handled through DSP, but they aren't the same thing. Room correction is an algorithm for minimizing linear distortion. Bass management serves a similar purpose I suppose but it composed of filters designed to integrate and maximize all the speakers to maximize their capabilities. It involves taking a matrix of input channels, potentially as many as what like 32 channels now in some systems, then filtering each of those 32 channels to either strip away the bass and redirect it to a single channel or redirect it to all of the channels (as in the max bass or double bass options some have). The processor then needs to output 32+ channels which are each individually processed and this is where the room correction usually comes in. Applying a correction filter to each output channel after bass management.

As I understand it, with NAD, Arcam, and Emotiva, the bass management was developed by those respective firms (or a contractor working for them I suppose), and Dirac is applied after that. Dirac, the company, has nothing to do with their bass management approach.

Which means I need to convince a company like Emotiva to add some extra capabilities to their bass management. Full control over the matrix with filters in different locations of the signal chain.

I mean, turning your surrounds into a DBA is pretty weird for sure, I don't think anyone is going to do that for me. Once I know it works, I'll probably be chaining two DSP devices together to make it work.
 

Talley

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What I’ve seen popular is integrating minidsp products to do just as your saying. Bedtime now lol
 
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