AI guided Room Optimization.

[AJ Soundfield]

When you add subwoofers to a system you become a speaker designer. You then get to design a crossover and find the speaker placement that properly integrates your components.

If you are doing this without the ability to measure individual speaker impulse response and adjust timing, determine crossover slopes and amplitudes then you are shooting in the dark.

This is where the “constantly adjusting never satisfied” syndrome takes over because it’s just never right.

This also creates interesting discussions about fast and slow subwoofers. Properly integrated subwoofers are fast, poorly integrated ones are slow.

Agreed. I would add the biggest issue beyond that is the room and the resonances. Below 50-60hz so called "traps" are complete nonsense, as far as nearly 60 foot long waves are concerned. That's where EQ is mandatory. And if you are a non audiophile 100% scientific approach to electroacoustic reproduction like me, then for the last 20yrs you did this https://www.ioa.org.uk/system/files...le_low_frequency_cardioids_in_small_rooms.pdf
Or you listened to your MoFi records with horrid in room response, because you know, DSP baaad

 

[crwilli]

When you add subwoofers to a system you become a speaker designer. You then get to design a crossover and find the speaker placement that properly integrates your components.

If you are doing this without the ability to measure individual speaker impulse response and adjust timing, determine crossover slopes and amplitudes then you are shooting in the dark.

This is where the “constantly adjusting never satisfied” syndrome takes over because it’s just never right.

This also creates interesting discussions about fast and slow subwoofers. Properly integrated subwoofers are fast, poorly integrated ones are slow.

Well said. I never thought about sub integration that way.

To the point of this thread, using REW and an AI engine to analyze the measurements, you can improve the integration in a very short period of time - without becoming an expert!

 

[a.wayne]

Completely oblivious to the DSP imbedded in your system via recordings and of course there will never be any measurements of your inferior analog conversions showing where "bandaids" would fix. IOW, the typical audiophile system like the 100s, maybe 1000 including shows, I've heard. Don't worry Mr Wayne, no one will ever hear your "No DSP" system, you're safe.

Chelsea > Arsenal , stay tuned …

 

[W9TR]

Agreed. I would add the biggest issue beyond that is the room and the resonances. Below 50-60hz so called "traps" are complete nonsense, as far as nearly 60 foot long waves are concerned. That's where EQ is mandatory. And if you are a non audiophile 100% scientific approach to electroacoustic reproduction like me, then for the last 20yrs you did this https://www.ioa.org.uk/system/files...le_low_frequency_cardioids_in_small_rooms.pdf
Or you listened to your MoFi records with horrid in room response, because you know, DSP baaad

Thanks! You beat me to it. Good paper. I wish he would have included monopole subs as well.

There is a wealth of information out there:
The Welti paper on multiple subs.
Toole's work for Harman.
"Subjective Preference of Modal Control Methods in Listening Rooms" Bruno Fadenza, et all is another good one.
CTA RP-22 is a good resource. Very well written.
SSS (Symmetrical Subwoofer Setup) and CABS.

I am putting 4 high excursion subs in my new theater, placed so they excite the minimum number of modes and also don't become a trip hazard. There are always compromises.

​

 

[Kingrex]

Thanks AJ and W9TR. Good resources on how to set up a "swarm" of subs. I have been sold on them since Atmasphere has been talking about them. It makes complete sense. JR of Wallytools is a good friend who also has me convinced multiple subs is the way to go. I will use a swarm of some sort when my room is done. I am not going to try and damp my way with room treatments, or DSP my way out of issues. I fully understand why that wont work. Don't get me wrong. The subs will most definitely be powered by something like a Dayton plate amp with DSP. But the intent is to position the subs around the room properly where they do the majority of work smoothing out peaks and dips. I may use simple 10" or 12" dayton drivers in flat pack sealed enclosures. Again, Dayton. They make it pretty easy and inexpensive to put a system together. Atmasphere did say that Audio Kinesis has a better driver than the Dayton. I am open to drivers.

 

[AJ Soundfield]

Thanks! You beat me to it. Good paper. I wish he would have included monopole subs as well.

There is a wealth of information out there:
The Welti paper on multiple subs.
Toole's work for Harman.
"Subjective Preference of Modal Control Methods in Listening Rooms" Bruno Fadenza, et all is another good one.
CTA RP-22 is a good resource. Very well written.
SSS (Symmetrical Subwoofer Setup) and CABS.

I am putting 4 high excursion subs in my new theater, placed so they excite the minimum number of modes and also don't become a trip hazard. There are always compromises.

He specifically did not do monopoles because those had already been tested...and found to have too high decay times for reproducing lateralization spatial effects. Here is a paper that is an overview of 40+ papers, that show that decay times are critical. Note, this is primarily for music, not HT. Acoustic music can have spatial effects down to the lowest frequencies. The Welti and all other multisub approaches are based on monophonic signal. ALL spatial effects are lost <80 Hz +/-. That approach for smooth amplitude over a wide listening area is perfect for HT and music listeners who primarily listen to pop/rock etc (like Dr Geddes). For folks like me who listen to classical/jazz etc, it's a complete no go. Thankfully there were folks like Dr Griesinger, JJohnston and more recently Genelecs perceptual scientist Thomas Lund
I absolutely do not recommend monophonic, monopolar subs for acoustic music.

 

[AJ Soundfield]

Thanks AJ and W9TR. Good resources on how to set up a "swarm" of subs. I have been sold on them since Atmasphere has been talking about them. It makes complete sense. JR of Wallytools is a good friend who also has me convinced multiple subs is the way to go. I will use a swarm of some sort when my room is done. I am not going to try and damp my way with room treatments, or DSP my way out of issues. I fully understand why that wont work. Don't get me wrong. The subs will most definitely be powered by something like a Dayton plate amp with DSP. But the intent is to position the subs around the room properly where they do the majority of work smoothing out peaks and dips. I may use simple 10" or 12" dayton drivers in flat pack sealed enclosures. Again, Dayton. They make it pretty easy and inexpensive to put a system together. Atmasphere did say that Audio Kinesis has a better driver than the Dayton. I am open to drivers.

See above

 

[Kingrex]

See above

Deep reading. Not too hard to follow, but takes a lot of time to read through. I have only gotten a couple pages in. Hopefully the articles will help the consumer to set up low frequency speakers.

I did find it interesting in the introduction that it notes the goal is not even bass response. Its designed for spatial response. I have always heard bass below 80 hertz is too long a wave in a small room to detect the location of the bass in the room. This in my mind is different than hearing where the bass instrument is perceived in the soundstage. Put another way, a subwoofer behind you should not be heard behind you. But a subwoofer behind you, can shift where you think you hear the bass player in the performance on the stage. Lots of people have noted there subs shift where they perceive this. I doubt few understand why this is happening. My initial take is these links are going to explain why this is happening and how to optimize this affect in playback.

http://www.davidgriesinger.com/asa05.pdf

 

[AJ Soundfield]

I did find it interesting in the introduction that it notes the goal is not even bass response.

Not quite. The goal is response in the listening area free of peaks. This is not the same as "flat" which you will amusingly see on most forums, where someone has boosted nulls and posted a ruler flat slope to ooohs and aaahhs.
From that paper:

One of the common fallacies in this field is that the perceived sound quality depends only
on the sound pressure at the listening position. A corollary of this assumption is that
optimum bass in a room occurs when the pressure at low frequencies is maximally
uniform both with frequency and listener position. In other words, sound is best when a
listener hears all low frequencies equally loudly regardless of where he or she happens to
be.
In practice, bass does sound better when it is free of gross frequency response anomalies.
However the assumption that sound quality depends only on sound pressure is clearly
untrue.

Its designed for spatial response. I have always heard bass below 80 hertz is too long a wave in a small room to detect the location of the bass in the room.

That is correct and how 100% of audiophile will respond. This isn't about localization, i.e, the ability to detect the location as you note. It's called lateralization, the ability to detect the difference between monophonic and non-monophonic bass <80Hz, more like a "narrow" vs "wide" sensation. Lund now refers to it as Auditory Envelopment.

This in my mind is different than hearing where the bass instrument is perceived in the soundstage. Put another way, a subwoofer behind you should not be heard behind you. But a subwoofer behind you, can shift where you think you hear the bass player in the performance on the stage. Lots of people have noted there subs shift where they perceive this. I doubt few understand why this is happening. My initial take is these links are going to explain why this is happening and how to optimize this affect in playback.

http://www.davidgriesinger.com/asa05.pdf

You have (dipole) speakers ideal for hearing this effect. Combined with monopole subs, you could create a cardioid pattern in the bass. I do just that with my designs. Unfortunately for optimum results you would need EQ. DSP is the superior way to do this. Biamp, use your SETs for the horns, SS/DSP for the woofers. They could use it.
https://audioxpress.com/files/attachment/2695
Btw, monophonic/monopoles are fine below 40Hz ish. That's the lower practical limit for lateralization. Use as many as needed.

 

[Kingrex]

Not quite. The goal is response in the listening area free of peaks. This is not the same as "flat" which you will amusingly see on most forums, where someone has boosted nulls and posted a ruler flat slope to ooohs and aaahhs.
From that paper:


That is correct and how 100% of audiophile will respond. This isn't about localization, i.e, the ability to detect the location as you note. It's called lateralization, the ability to detect the difference between monophonic and non-monophonic bass <80Hz, more like a "narrow" vs "wide" sensation. Lund now refers to it as Auditory Envelopment.

You have (dipole) speakers ideal for hearing this effect. Combined with monopole subs, you could create a cardioid pattern in the bass. I do just that with my designs. Unfortunately for optimum results you would need EQ. DSP is the superior way to do this. Biamp, use your SETs for the horns, SS/DSP for the woofers. They could use it.
https://audioxpress.com/files/attachment/2695
Btw, monophonic/monopoles are fine below 40Hz ish. That's the lower practical limit for lateralization. Use as many as needed.

Thank you. I will read later

 

[W9TR]

Thanks for the references AJ. Very interesting and helpful.
Since I am building a multipurpose room it has to work equally well for HT and 2 channel. 2 channel wins any arguments.
In my current system the 2 channel setup does not use subs. The speakers I have go pretty low in-room, so I never felt the need for subs. When the recording is good enough, my room's acoustic is replaced by the hall acoustic. The new room should be even better as the sidewalls are 11 ft from the listening position and the main L & R speakers are 5' from the sidewalls.

With the Trinnov and four separate subwoofer feeds that can be independently controlled, I'll be able to experiment quite a bit. While a 2 x 2 front/back subwoofer array is not ideal, I will implement a Double Bass Array and see how that works. This approach basically uses the rear subwoofers as active absorbers, whose output is delayed by the time it takes for a plane wave emitted at the front of the room to reach the rear, and then inverted in phase so as to cancel that plane wave. Trinnov calls this Waveshaping and has a number of white papers covering all the technologies they employ. Of course they use DSP, and they 're from France, so true Audiophiles will fart in their general direction.

 

[Kingrex]

. Of course they use DSP, and they 're from France, so true Audiophiles will fart in their general direction.

If the french would bathe, you wouldn't have to fart to cover their stink.

 

[AJ Soundfield]

Thanks for the references AJ. Very interesting and helpful.
While a 2 x 2 front/back subwoofer array is not ideal, I will implement a Double Bass Array and see how that works.

You're welcome Tom. Unfortunately DBA is also monophonic. Once again, fine for HT and/or music below 40hz.
If your mains go to 40hz without issue, then you're probably fine using 4 subs, that is usually enough to spatially average out, with EQ added, smooth aka free of peaks response, in a defined listening area. IMO, DBA is visually impressive to the impressible, but a poor use of space, especially for those focused primarily on SQ.
Btw your SF Amatis have pretty smooth native response. I would not use any EQ on them >500hz +/-, other than a smidgen "to taste", but wary that recordings can vary quite a bit!

 

[W9TR]

One of the nice things I’m looking forward to is the option, should I choose to use it, of augmenting the SF Amatis with stereo subs. I have never needed to eq them for stereo listening, and in my HT they are crossed over at 40 Hz.

Using my preamp as a pass through I get the best of both worlds. Simple signal path for Stereo, all the HT stuff powered off, then the full HT experience with subs, etc.

It really is two different worlds, which is really interesting to me.

The HT people are standards driven, CTA RP 22 and 23, for audio and video, respectively.

CEA 2034 aka ‘Spin-a-Rama’ for speakers.

I needed 12 new speakers for surround and heights for the HT. I looked at the SF stuff but it was lacking in dispersion and the response wasn’t so great either. I looked at SF, KEF, Perlisten, Focal, and Revel. All stand mounted monitors.

What I found after several hours of listening at my favorite B+M store was the speakers that had the best CEA 2034 performance also sounded the best to me. So I walked out with KEF speakers that sounded better than most of the speakers I’ve had in my system. I was really pleasantly surprised. The KEF Q Concerta meta made the cut for the surrounds, and were $999 a pair, about 1/2 the cost of other similar speakers.

These are the good old days in audio.