[Jim Smith]

May I respectfully disagree?

Using programs like this is not a panacea for doing actual work.

They may be a good starting point, but I've NEVER heard one set-up that I couldn't improve upon in a fundamentally powerful and musical way.  I've come to believe that an acoustician/mathematician/programmer sitting in a room hundreds of miles yours cannot possibly know what will sound best in your room. He can provide some exceptionally important guidelines, but in no way is any program I've heard likely to approach the very best result.

No problem with using it to get a great idea as to where to start, just don't think those pretty curves are the best sound you can get because they certainly are not.

Maybe I misunderstood your post, - I'm just saying that an organanically tuned final sound will be more pleasing than a mechanically tuned sound.

[vin69]

Wondering if I can do 3 sub asymmetrical arrangement with smaller 10" subs in my room to minimize room modes & also to get decent performance down to 20hz. My room is approx 22x13x9ft. The spacing between the mains & sidewall in only 16" therefore won't be able to accomodate bigger subs. I am planning to level match & then EQ using Velodyne SMS1. I have 3 subs that I can use, all sealed; one dual opposed sub with 2 10.4"drivers,one sealed with one 10.4" driver, one sealed sub with 10" driver/10" passive radiator. I am planning to place the dual opposed sub between lt main & center, sealed sub in rt front corner & the sub with PR on the back midwall off the floor on a 1.5" thisk sheet of wood. Do I need to run the mains fullrange? My mains have 2 8" woofers for low end. Thanks for any input.

[AUDFILE74]

Personally i run 2 subs. i find they balance out my room modes quite well. i have a nasty mode from 60-80 hertz. i had to take advantage of the xovers forced on me. my source is a ht in a box blu-ray player/ reciever. i only use the front channels. they are  oem hipassed at 80 hz. the lowpass is 80 hz so i cant change it. however the subs have a crappy built in xover that i set to cut off at 50 hz. in both cases the cutoffs are shallow so i used this to my advantage and moved the sub out of the freq of the broad room mode . my apartment's living room is 10w x 16l x 8h. surprising ly i got it to work. now if i can affor my upgrade plan then life will be awesome. i am planning to do a few changies over time so time will tell if my new plan will work.

[*Scotty*]

Here is the technical explanation of the principles underlying the use of multiple sub-woofers and how to best implement them in a system. See link below.
http://www.audiocircle.com/index.php?topic=106838.0
I have been using a simplistic version of this method for the last three years in my system. If you read the information you will notice that optimal results were achieved in symmetrical rooms with symmetrical sub-woofer placement.
 In my case I have an asymmetrical room and asymmetrical placement of the subs. The main speakers are equivalent in cone area to having two 15in subs at the front of the room with the advantage of having half the bass output located midway between the floor and the ceiling. The speaker is an WMTMW design. The bass is still very even in the room but I do have a transverse standing wave zone next the wall to my extreme left.
The room is L shaped with the main speakers at the bottom of the L  ________________
  Big Xs are the loudspeakers the little x is the listening position       l     X        X             l
  small s is sub-woofer locations, small h is hallways,                       l                              l
 big F is foyer.   Big P denotes location of standing wave.                  lP         x                  l
                                                                                                    l                   ___    sl
                                                                                                    l       L          l
                                                                                                    l                   l
                                                                                                    l                   l    K
                                                                                              ___l          s____l     
                                                                                             h___          _h___
                                                                                                    l         l
                                                                                                    l__F__l
Note,"Drawing" not to scale!
The Front wall is 21ft. across and the distance from the front wall to the rear sub is about 20ft., the foyer extends back another 7ft.
I am very happy with the results I achieved and large subs were not required to do this. The sub in the rear is a 10in and the right side sub near the entrance to the kitchen is an 8in..
Scotty

[WGH]

Scotty - are you running the rear and side subs out of phase with a time delay?

Wayne

[*Scotty*]

Lets start with some basic physics first. The speed of sound is about 1100ft/sec or roughly one foot per millisecond. If you have the capability to delay the output you can place the sub-woofers where ever you want to relative to the listening position or precisely control where the point of cancellation occurs in the room. For example if your listening seat is 9ft. away from your front speakers and your rear wall is 6ft. behind you, the rear subs output will need to be delayed by 4 milliseconds. This allows the front bass wave to propagate past your position by about one foot and then be canceled out. If you do not have the capability to delay the output of the sub-woofers by the correct amount then you have to go to plan B.
 Plan B consists of placing the sub-woofers further away from the listening position than the main speakers. This places the location of the initial cancellation of bass frequencies behind the listening position thus allowing you the time to hear the bass wave-front. The sub-woofers only have to be one foot or more further away from you than the main speakers are for this trick to work.
 I pretty much have the bass planer wave-front emanating from the front of the room handled. The shape of the listening room makes propagating an anti-phase planer wave from the back much more problematic and I have had to settle for what I could get.
Scotty
Edited for increased clarity.

[medium jim]

May I respectfully disagree?

Using programs like this is not a panacea for doing actual work.

They may be a good starting point, but I've NEVER heard one set-up that I couldn't improve upon in a fundamentally powerful and musical way.  I've come to believe that an acoustician/mathematician/programmer sitting in a room hundreds of miles yours cannot possibly know what will sound best in your room. He can provide some exceptionally important guidelines, but in no way is any program I've heard likely to approach the very best result.

No problem with using it to get a great idea as to where to start, just don't think those pretty curves are the best sound you can get because they certainly are not.

Maybe I misunderstood your post, - I'm just saying that an organanically tuned final sound will be more pleasing than a mechanically tuned sound.

I agree that organic is better.  Mechanically room corrected sounds wrong to my ears as it doesn't let the real music through, example, Jaco Pastorious was considered the best bassist ever, but was a feel player and it would be a shame for much of it to be lost in translation by a computer device. For that matter, any musician or instrument.  Not to mention the natural note rise, decay, overtones, semi-tones, etc., that are often pitch corrected by said room correction devices.

Jim

[James Romeyn]

Moderator, please accept my apology and delete this if found to violate the marketing rule.

I prefer four subs.  Setup may seem daunting but it's not really.  Subs are only 1cf and site a few inches from walls. 

1. Temporarily remove the main listening seat and site a sub on the floor at that location.  Play bass through the sub while listening at every location near the wall where one sub could fit.  Find the location producing the smoothest bass.  Bob Carver first suggested a variation of this advice, a mirror image of listening at the main seat while moving the sub around to different locations.  Measure the distance to the nearest corner and site one sub at this point.   

2. Use Golden Ratio to site the three remaining subs to maximize bass mode flattening effect. 

3. Further maximize mode flattening effect by inverting one sub polarity (inverting two subs cancels energy below 30 Hz).

Results consistently exceed that of any other system I've auditioned regardless of cost or complexity.  Though I admit that Vandersteen's 5A Carbon got close at 2012 CES (less deep, less powerful, less enveloping, still more boundary effects, but extremely natural and acoustic quality to double bass).   

My setup advice (details: http://jamesromeyn.com/home-audio-gear/dsa-1-0-distributed-subwoofer-array-5-pieces-4k-usd/) is only a variation of all the good prior work by Duke LeJeune, Dr. Earl Geddes, Dr. Floyd Toole, and Todd Welti.   
   

[medium jim]

James, no need to apologize as I see no broken rules.


Jim

[*Scotty*]

This is a reply to post no. 70 by cheap-jack in the "When do you need to go below 40hz" thread. http://www.audiocircle.com/index.php?topic=107243.msg1102140;topicseen#new
 It can appear that all is well when you measure your system's bass response only at your listening position and it looks like you have achieved flat response. This single measurement done at only one point in the room fails to reveal the existence of a complex pattern of standing waves that are in the room between the listening position and the loudspeakers.
 The the standing waves are a function of the rooms dimensions and are inescapable. If the cavity resonance aspect of the room is not addressed in some fashion, either actively via a CABS approach or passively via absorption, the room's resonant behavior in the bass frequencies will muddy the sound of bass instruments and the alternating zones of high and low pressure between the listening position and the loudspeaker will significantly degrade the imaging qualities of the system.
 In a basement it can be more difficult to realize that the quality of the bass reproduction is suffering due to room resonance problems. The basement's concrete floor and walls do not vibrate in sympathy with the bass frequencies as they can in an above ground room with two by four wood walls and a suspended floor. The vibration of the above ground structure, particularly when excited by standing waves, will sound much worse in the bass region by comparison.
 The imaging degradation remains a constant whether the room is above or below grade. This is a case of not realizing something is broken until it's fixed. When the standing waves in the room are reduced or eliminated,the bass becomes better and the the stereo image, which heretofore has been two dimensional musical wallpaper, albeit unrecognized, suddenly becomes three dimensional, immersive  and room filling.
 If the CABS approach is used to damp the rooms bass resonance behavior a particularly dramatic A- B demonstration can be done. By simply by turning off the rear sub-woofers, the three dimensional immersive sound-stage which has filled the room will abruptly collapse against the front wall.
This dramatic effect is partially dependent on the innate imaging qualities that the system has, a crappy receiver with inherently poor sound-staging will not show as dramatic a before and after difference, being more or less two dimensional in its imaging anyway.
Scotty

[cheap-Jack]

Hi.

This is a reply to post no. 70 by cheap-jack in the "When do you need to go below 40hz" thread. http://www.audiocircle.com/index.php?topic=107243.msg1102140;topicseen#new
(1) It can appear that all is well when you measure your system's bass response only at your listening position and it looks like you have achieved flat response.

(2) This single measurement done at only one point in the room fails to reveal the existence of a complex pattern of standing waves that are in the room between the listening position and the loudspeakers.

(3) The the standing waves are a function of the rooms dimensions and are inescapable. If the cavity resonance aspect of the room is not addressed in some fashion, either actively via a CABS approach or passively via absorption, the room's resonant behavior in the bass frequencies will muddy the sound of bass instruments and the alternating zones of high and low pressure between the listening position and the loudspeaker will significantly degrade the imaging qualities of the system.

(4) In a basement it can be more difficult to realize that the quality of the bass reproduction is suffering due to room resonance problems.

(5) The basement's concrete floor and walls do not vibrate in sympathy with the bass frequencies as they can in an above ground room with two by four wood walls and a suspended floor. The vibration of the above ground structure, particularly when excited by standing waves, will sound much worse in the bass region by comparison.

(6) When the standing waves in the room are reduced or eliminated,the bass becomes better and the the stereo image..

(7) If the CABS approach is used to damp the rooms bass resonance behavior a particularly dramatic A- B demonstration can be done. By simply by turning off the rear sub-woofers, the three dimensional immersive sound-stage which has filled the room will abruptly collapse ....

Sorry, what you posted above, quoting whatever white papers or texts regardless, do NOT apply to my sustem in my basement audo den. OK?

(1) Yes, if it is not measured at my sweet spot, please tell me where else should I measure which is acoustically more revelant ? Do YOU change yr listening spot all the time???

(2) Why shoud YOU worry about "complex pattern of standwaves" any where inside the SAME room  when the soundwaves arrivng the ears at the sweet spot sound OK & measured OK???

(3) No, WITHOUT switching on my sub, the imaing & sounstaging of my music here is sharp, proportional & precise. So can I safely assume there is NO bass resoance problems to worry ahout?

(4) & (5) Basement is far more better place for audio, with zero vibration from the concrete floor vs vibrative suspended floors, much more quiet being 10ft or so subgrade. More music focussing. LESS disturbing to other people in the same house. This is a win win situation. These are the main reasons why I've chosen to have my audio world down the basement.

Home sweet home upstairs. Music sweet music down the basement.

WithOUT any elaborated acoustical treatments ever installed, basic finishing, e.g. wooden wall panels on studs with glasswool felt filling the voids behind, wall to wall carpet with thick rubber underlay, & standard drop ceiling with 2x4 glasswool ceiling tiles - providing floor- ceiling clearance only 7 feet !!!!

(6)& (7) IF yr CABS theory is valid, please explain why my 7-ft clearance audio den can get ZERO bass resonance problem as heard & measured with 20Hz or so pipe organ notes on via one single 10" sub & the overall imaging & soundstaging is still so transparent & precise.

Maybe it is the time for you to get out yr CABS nutshell to beath some fresh airs.

c-J

[*Scotty*]

Perhaps I have not explained the problem thoroughly enough yet. The standing waves exist in the room anytime the bass frequency range is reproduced, regardless of whether a sub-woofer is used or not. This is not my "theory", this is simple physics. The frequencies of the standing waves in the room are a function of the rooms dimensions which determines the Schroeder frequency. You can read more about the Schroeder frequency at this link.
http://www.linkwitzlab.com/rooms.htm
 You are exactly correct when you state that you are hearing your music after it has had the damage done to it by the standing waves present in the room. A simple frequency response measurement ignores the low frequency reverberation time of the room as I stated in an earlier post. It is your prerogative to be happy and satisfied with the sound you get of of your system, but the laws of physics are not suspended in your basement. The presence of standing waves in your listening room remains, degrading the quality of your bass as well as damaging the imaging potential of your system and
is not mitigated by denying their existence.
 In as much as you already own a sub-woofer and your speakers reproduce some bass already it wouldn't take much to do an experiment whereby you move your listening position closer to your loudspeakers and away from the rear wall. You could then place your sub-woofer behind your listening position and operate it out of phase thereby canceling out some or all of the standing waves in your room.
 If you are impressed with the improvement you could then purchase a Behringer DCX 2496 and delay the output of the rear woofer by the amount necessary to allow you to hear the bass wave front generated by the front speakers before the output from the sub-woofer starts to cancel it out.
 Hopefully my reply leads you to a better understanding of the physics principles governing the reproduction of bass frequencies in a domestic environment.
 Many of the effects that standing waves produce in your listening room can be illustrated by using a rectangular wave tank, aka 13in.by 19in. pyrex dish, that many may have first seen in high school physics classes.
Planer wave-fronts can be generated and if two oscillators are used standing waves can be canceled out and the validity of regarding the room as having a single series of resonant modes associated with its longest dimension can be demonstrated.
Scotty

[medium jim]

Scotty,

It sounds like Cheap Jack is happy with the way his system sounds and debating this further is not going to change his mind, so let's move ahead.

Jim

[cheap-Jack]

hI.

Perhaps I have not explained the problem thoroughly enough yet.
Scotty

What "problem" could it be other than 'cult' like bass obsession, IMO.

I am a free-lance acoustic/audio consultant & have auditioned many audio setups from homes to hi-end audio studios which never installed any active subs to kill bass standing waves.

They includes the most hi-end audio studio, a regional rep of Audio Note Japan audio equipment.  An Audio Note TT with tonearm/MC cartridge retailed for U130,000 & USD79,350.00  each Ongaku SE tube monoblock power amp.
Please don't tell me That Audio Note Japan rep does not know how to fix the subsonic resonance problem in its studio if any there.

c-J

[DaveC113]

My question about multiple subs is, why are they necessary given you have only one ideal listening position anyway? I can't argue with the science and reasoning behind multiple subs and why they offer an advantage, but the fact is we tune the placement of our main speakers to have the best soundstage at a particular listening position that remains static. Given a static listening position, I have always been able to move my single sub around so that it sounds good in the sweet spot. This is always behind and in between the main speakers, currently with the sub pointed toward the side, but back at a slight angle. I have it x'ed over at 50 Hz with a 24 dB/octave slope, and IMO a low x'over freq with a steep slope is the only way to make a sub audibly disappear. I have no experience with multiple subs but would like to try it sometime, just never appropriated the funds to a 2nd sub.

[JLM]

It has been demonstrated that the human ear/mind has a remarkable ability to acclaimate to the sound in different settings.  This explains why our experiences don't line up with the physics. 

Here's a simple solution, if you currently have a sub or not to address to issues raised by anand/scotty:

http://www.spatialcomputer.com/page9/page10/page10.html

For $1295 USD each this subs don't connect to your system.  The built in mike/computer produce out of phase real time correction when placed on the back wall with no setup/calibration needed.

[DaveC113]

It has been demonstrated that the human ear/mind has a remarkable ability to acclaimate to the sound in different settings.  This explains why our experiences don't line up with the physics. 

Here's a simple solution, if you currently have a sub or not to address to issues raised by anand/scotty:

http://www.spatialcomputer.com/page9/page10/page10.html

For $1295 USD each this subs don't connect to your system.  The built in mike/computer produce out of phase real time correction when placed on the back wall with no setup/calibration needed.

OK, but for $0 I can move my sub around so the bass response is just fine in the sweet spot. I can do this by ear pretty well too.

[*Scotty*]

I will try giving you an analogy that describes what is taking place in a room with uncontrolled resonances below the Schroeder frequency.
First imagine the imaging information projected by your loudspeakers as cargo containers full of very breakable blown glassware. These are on cargo ships traveling across the room to your ears. On the way to their destination they encounter high seas and very rough water, which are the complex pattern of standing waves that exist in your room.
 While no ships were lost on the way to the final port of call a whole lot of glassware was broken due to the rough water the ships had to pass through.
The cargo did not arrive intact. In the same way, critical damage was done
to the imaging information as it tried to pass through the zones of high and low pressure between the loudspeakers and your ears.
 When you position your speakers for best imaging you are trying to work around the damaged cargo problem and achieve something you can live with, while never realizing that the containers are full of broken glass.
If you control the standing wave problem you do two things simultaneously. The bass arrives in step with the rest of the frequency spectrum giving you better bass resolution and impact and the imaging information survives the trip intact.
 You are now listening to a coherent delivery of the entire musical waveform, which results your system reproducing a much more three dimensional sound-stage with very well defined bass. When you add a second sub-woofer and have things setup correctly,you can turn off the rear sub and watch the heretofore 3D sound-stage collapse against the front wall and turn into musical wall paper.
Scotty

[DaveC113]

I will try giving you an analogy that describes what is taking place in a room with uncontrolled resonances below the Schroeder frequency.
First imagine the imaging information projected by your loudspeakers as cargo containers full of very breakable blown glassware. These are on cargo ships traveling across the room to your ears. On the way to their destination they encounter high seas and very rough water, which are the complex pattern of standing waves that exist in your room.
 While no ships were lost on the way to the final port of call a whole lot of glassware was broken due to the rough water the ships had to pass through.
The cargo did not arrive intact. In the same way, critical damage was done
to the imaging information as it tried to pass through the zones of high and low pressure between the loudspeakers and your ears.
 When you position your speakers for best imaging you are trying to work around the damaged cargo problem and achieve something you can live with, while never realizing that the containers are full of broken glass.
If you control the standing wave problem you do two things simultaneously. The bass arrives in step with the rest of the frequency spectrum giving you better bass resolution and impact and the imaging information survives the trip intact.
 You are now listening to a coherent delivery of the entire musical waveform, which results your system reproducing a much more three dimensional sound-stage with very well defined bass. When you add a second sub-woofer and have things setup correctly,you can turn off the rear sub and watch the heretofore 3D sound-stage collapse against the front wall and turn into musical wall paper.
Scotty

Thanks Scotty, that makes sense. I have always thought the higher freqs sounded better with a good bass foundation, so I think I can understand what you're saying. This isn't the best news for my wallet though. 

[*Scotty*]

The job can be done by purchasing a sub with similar bass extension to your existing sub and a Behringer DCX 2496. This alternative should be doable for less than $1300.
The DCX 2496 has 6ch of delay possible and allows you to have a chance to hear the bass before it gets canceled out by the anti-phase wave from the rear sub. As long as you cancel the bass below 125Hz before it hits the rear wall you are good to go. The addition of delay allows you to sit anywhere you want and still hear good bass. Fixing the bass problem also allows you to position the main speakers where ever they need to be for best imaging without having the bass problems influence the location of the main speakers.
 Remember you only have to cancel out the bass energy in the room that remains after absorption and transmission losses have occurred. This means that if you have a 12in sub in front a 10in sub with the same extension will probably be capable of canceling out the remaining bass energy at the back of the room. Both subs should be placed flat against the center of the their respective walls.
Scotty