Q: 2 subs versus 1 ... and proper setup if 2

[Tahoe Gator]

That second sub out on my NAD T773 has always begged me to wonder about the merits of having 2 subs versus one. For example, are there benefits to having 2 equal distance from the listening/viewing location (symmetrical), rather than one to one side (assymetrical)? Of course, cost is an issues, but perhaps 2 lower cost subs can surpass 1 expensive sub? Maybe subs are not "additive" and a second does not add much; or maybe 2 would be awesome? And then I can only wonder if there are issues with cancelation, etc., such that positioning is really critical? Anyhow, thought it would be fun to pose the 1 versus 2 question to the audience.

[musicman1999]

Bass is not directional,so being symmetrical is really not an issue.Depending on the room,dual subs(or more),can help to overcome problem nodes in the room and can really smooth out the response.Largely room dependent.

bill

[westcott]

That second sub out on my NAD T773 has always begged me to wonder about the merits of having 2 subs versus one. For example, are there benefits to having 2 equal distance from the listening/viewing location (symmetrical), rather than one to one side (assymetrical)? Of course, cost is an issues, but perhaps 2 lower cost subs can surpass 1 expensive sub? Maybe subs are not "additive" and a second does not add much; or maybe 2 would be awesome? And then I can only wonder if there are issues with cancelation, etc., such that positioning is really critical? Anyhow, thought it would be fun to pose the 1 versus 2 question to the audience.

Most people agree that all speakers are room dependant but if you have a fairly rectangular room, two or four subs can really help provide the power and the balance to provide a wider sweet spot in the room. This is especially true of home theater setups.

The white papers I have read recommend symetrical placement in the center of the front and back wall or the center of the two side walls as a starting point for two subs. Corner placement was only suggested as a starting point if you had four subs. I think Dr. Toole's papers have been moved to the Infinity website if you would like to read what he has to say. Some of the documents can still be found on the Harman Kardon site, as well.

He also suggests distances from the walls, based on crossover setting. Very accurate data, IMO when I exhaustively tested these placement suggestions myself. He is not a big fan of equalization and makes good arguements for avoiding there use whenever possible. More subs can accomplish this.

In short, two can be better than one but you have to be the final judge as to what you can afford and does that last bit of "better" sound is worth the above average money investment.

I guess I would have to say that placement is more important than quanity but done right, it can be impressive.

Hope this helps!

[kexodusc]

As mentioned, the benefits of 2 subs are an increase in output (+3 dB, which isn't much), and a smoothing out of the frequency response. Depending on the output levels you are hoping to obtain, having the second sub can really cut down on excursion requirements, distortion, and thereby improve sound quality. Moreso at higher volumes than at lower volume though.

Adding a second subwoofer can be a good thing. However, before someone spends $400 - $1000 on a second sub, they owe it to themselves to spend at least the same on acoustic room treatment. I think most would advocate using bass traps/room treatments to alleviate mode effects rather than adding subwoofers. I suspect in many homes, optimal sub placement for 2 subs is impractical, and just adding a 2nd sub along the front wall won't make much difference in frequency response. But adding even a few bass traps will.

Proper room treatment will do better at smoothing out bass response, not to mention tame reflections, flutter and echo...you'll get a better sound at all frequencies, not just the bass. I'm guessing for most people, it's a much more cost-effective alternative.

Toole's work is an excellent starting point. There are some practical limitations of course. If you're room isn't very big, and you don't frequently accomodate more than 2 or 3 people sitting close to the sweet spot (or you just don't care what other people hear) you can achieve great results with only 1 sub and some equalization if necessary. The more seating positions, and the further away from the sweet spot you move, the more variance you'll get though.

Before adding a 2nd sub, I'd make sure you know what the objective is, and be sure it's the most effective and cost-effective way of meeting that objective.

I've finally ordered the components for my 2nd subwoofer. Could be months before I have time to build the way things are going but it'll be my 2nd attempt at running 2 subs in my system.

[Sir Terrence the Terrible]

Most people agree that all speakers are room dependant but if you have a fairly rectangular room, two or four subs can really help provide the power and the balance to provide a wider sweet spot in the room. This is especially true of home theater setups.

The wavelengths in bass frequencies are so large that sweet spots do not enter the equation.

I would not recommend using 4 subs placed all over the room. Each subwoofer would couple with the rooms modes and nodes very differently from different locations producing different frequency responses from each. Overall this would create a very rough in room measurement.



The white papers I have read recommend symetrical placement in the center of the front and back wall or the center of the two side walls as a starting point for two subs. Corner placement was only suggested as a starting point if you had four subs. I think Dr. Toole's papers have been moved to the Infinity website if you would like to read what he has to say. Some of the documents can still be found on the Harman Kardon site, as well.

Placing subwoofers in the center of two sidewalls (no matter what Russ Hershenson says) is a very bad idea for a few reasons. First, you will experience a low bass penalty because there is no support in the deep bass from room surfaces. You will make the sub have to work harder to acheive X level, which will increase distortion as the volume is turned up to compensate for low frequency losses. A sub centered between two will not measure as well as a sub in a corner as well. Having four subs center between two opposing wall (side to side and front to back) will cancel modes wall to wall modes as the subwoofer on opposing walls would be out of phase with each other. However you will still have to deal with the low bass penalty of early roll off.


He also suggests distances from the walls, based on crossover setting. Very accurate data, IMO when I exhaustively tested these placement suggestions myself. He is not a big fan of equalization and makes good arguements for avoiding there use whenever possible. More subs can accomplish this.

The farther you move a sub from the wall, the more low bass penalty you pay. From what I understand in Dr. Tooles papers he actually advocates corner placement over all other placements. He also DOES support EQ in subs, but not on MAIN speakers. More subs do not equally no EQ, it actually means MORE EQ because the subs are engaging the rooms modes and nodes from different places, which means they will each have slightly different frequency responses,


In short, two can be better than one but you have to be the final judge as to what you can afford and does that last bit of "better" sound is worth the above average money investment.

I guess I would have to say that placement is more important than quanity but done right, it can be impressive.

Hope this helps!

Based on Dr. Tooles work placment is much more important that quantity. His work has determined that one sub in a corner measures better than four center between two opposing walls in the null position. Two spaced subs in opposite corners can be better than one when you have single row of seats, as this will provide a more even frequency response of those seats. Two subs in the same corner will provide +6db boost to the overall output without increasing the volume at the sub itself. This also lowers distortion at high levels because you can lower the volume of each individual sub which decreases the amount of woofer travel to acheive X level.

[westcott]

I will not address all your comments because I really am not that interested in the topic but you have to remember, with todays subs, power is usually not the limiting factor and so, bass reinforcement is not really an issue. What you are looking for is a cleaner bass, not more bass, to have a good overall sounding system. Using the walls of a room for reinforcement only introduces room modes that are hard to predict and control. The ideal situation is not to have any interaction with the room walls at all for cleaner bass.

As far as saying that a sweet spot does not enter into the equation is incorrect. All you have to do is walk around your room to know that not every seat in the house has ideal frequency response and it varies greatly based on your seating position, especially in the LF range.

[E-Stat]

That second sub out on my NAD T773 has always begged me to wonder about the merits of having 2 subs versus one. For example, are there benefits to having 2 equal distance from the listening/viewing location (symmetrical), rather than one to one side (assymetrical)?
One simple factor to consider is the practical low frequency capability of your mains. I, too, use a NAD receiver (T763) and Polk mains (RTi28s). After exhaustive testing using the Stereophile test CD and my trusty Radio Shack sound pressure meter, I found that the smoothest overall response I got with my system was to set the LFE crossover to 120 hz. Afterwards, I used a Behringer third octave EQ (on the subs only) to fill a 100 hz gap and slightly boost the bottom octave to achieve a flat response to 20 hz. Another poster said bass is non-directional. That is true when you are referring to frequencies below about 80 hz or so. Bass is directional at the optimum crossover frequency for my subs. That is why I use a pair of them.

As an aside, my neighbor has a killer 18" powered subwoofer in his HT system. He can shake the walls very well indeed. The problem is that his in-wall main speakers can barely reach 150 hz with any linearity. The result is either a huge frequency gap, or a decidedly directional solution when the sub is asked to fill in those upper bass frequencies.

rw

[robert393]

I'm not the "techy" person to be asking this question to, but I do have lots of experience with sound (own & car stereo shop). First let me tell you I have a total of 4 subs in my HT, and it sounds better than it ever did with only one. The overall sound is much improved and linear. Staging is very good. I have 3 subs located in the C/R/L speakers (powered). The speakers are set to run "full-range" with internal crossover point of 80Hz, and one of the subs run "LFE". I have 1 sub each at the 3-main speakers (C/R/L). These are internal (powered) subs in the mains (2-18" 1000w & 1-10" 150w on center).

Let's look at it this way. Each of the 5 channels (or 6) in a 5.1 or 6.1 system IS A FULL RANGE channel. That is to say the frequency range is output from the source unit/souce material at close to 10Hz - 30kHz. Of course this is where cross-over points are inserted (ex. 80hz). So, what I have done is set the reciever to "pass-through" the signal to the speaker at "FULL-RANGE" and utilize the internal crossover on the main speakers (C/R/L) therefore recieving the entire range of frequence to the speaker and sending the
80hz and below frequences to the 3 subs across the front of the stage.

I still run LFE to the sunfire.

Anyway, hope that was not too confusing of an answer. Later I will want to add 2 additional subs. 1-each at the L/R surrounds locations.

Robert

[jocko_nc]

I have two subs and like what they do for me.

crossover at 85 Hz. Dual Dayton Reference Series 10.00's. They work great with music.

jocko

[Sir Terrence the Terrible]

I will not address all your comments because I really am not that interested in the topic but you have to remember, with todays subs, power is usually not the limiting factor and so, bass reinforcement is not really an issue.

You are sure about this? I don't think so. First, most commercial subwoofers made today are extremely inefficient. Most of the power of the amps are lost in heat dissipating from the woofer itself. Secondly according to Richard Hardesty's (formerly of Widescreen review) testing most commercial subs cannot reproduce signals below 30hz cleanly, and with low distortion at anywhere close to the maximum output requirement of the LFE channel (115db in room). They double, distort, and some cannot even reproduce any significant output at 25hz or below. One of the largest Velodyne subwoofer (The 18" ULD-18) they have ever made had a 1000 watt amp coupled to a 18" driver. Even when pushed into a corner this subwoofer could barely make 102db at 20hz without some rattling coming from the driver which is a sign it is in distress. Most people have subwoofers with no more than 200-400 watts coupled with a 10" or 12" driver which a much shorter linear stroke than the ULD-18. If the big velodyne couldn't make it with 1000watts, then how in the hell do you think a 200-400 amp with a 10 or 12" woofer could?

A little overall information for ya. Bass management places considerable strains on a subwoofer. Each channels bass output directed to the sub increases the electrical signal by 3db. Once you have sent all of your main speakers bass information to the sub, that is 15db of electrical signal PLUS the LFE output that is sent to the sub. The maximum output of the LFE channel if calculated to reference levels would be 115db. If you listen 5-10db lower than that it would be 105-110db PLUS the additional 15db from the mains. That would mean an overall output of 120-125db in room. How many subs do you know can do this down to 20hz? VERY few right? It is a good thing it is rare( but happening more often these days) that there is not high level bass in all channels simultaneously, for we would understand how frequently our subs compress the signal because it has reached its physical limits of driver travel.



What you are looking for is a cleaner bass, not more bass, to have a good overall sounding system. Using the walls of a room for reinforcement only introduces room modes that are hard to predict and control. The ideal situation is not to have any interaction with the room walls at all for cleaner bass.

If you are looking for cleaner bass, then the driver itself must not be operating at the top of its linear travel, and the amp cannot be pushed hard. How do you accomplish this? You place the woofer at a place where it benefits from acoustical gain without adding volume from subs own volume control. If you place your sub in a corner, each surface it "sees" it benefits from a 3db boost without pushing the amp. If it sits on the floor you will get an acoustical gain of 3db. If it sits on the floor next to the sidewall, it gets 6db acoustical gain. If it sits on the floor, against the side and front wall, it get's 9db of nearfield acoustical gain. That is 9db gain without even turn the volume knob at all. If the driver and amp had to make up this difference without the benefit of corner placement, it would likely overload the amp, and the woofer would be exceeding its linear travel by a long way. That will not produce clean bass ducky!
Trying to avoid the rooms resonances leads to frequency response irregularities from multiple reflections arriving at different times to the ear. That is not what I would call smooth even bass ole boy.

Based on subwoofer tests by Richard Hardesty, Dr. Toole, and Tom Nousane shows that the best measured, lowest distortion, and cleanest output from a sub comes from corner placement. Arthur Ludwig did a series of subwoofer tests using the best engineering calculations, and he found that based on these calculation the best place for the sub was right near his ears. However when he measured the response from that place (well away from walls and off the floor) and subsequent listening tests, the subwoofer in real room conditions didn't measure smoothly, and he was able to locate it presence VERY easily. The best place he found for measured response and unlocalizeable output was the corners of his room.


As far as saying that a sweet spot does not enter into the equation is incorrect. All you have to do is walk around your room to know that not every seat in the house has ideal frequency response and it varies greatly based on your seating position, especially in the LF range.

The sweet spot in audio terms is the place where several optimum listening characteristics ideally converge. Imaging, frequency response, and overall system balance are part of these characteristics. Since imaging comes from the main speakers, what it optimal comes from the speakers, and listening seat being well away from the walls, and the listening position placed equidistant from the speakers. This listening seat placement is not ideal for frequency response or power response of subwoofer because it places the ears in a low pressure zone. The sweet spot for low frequency energy would be in the corners, along with the listening seat. That is not ideal for imaging. So when you speak of sweet spot, it doesn't really apply to LF only because the corner is not ideal for imaging, or overall system balance.

It might serve you well to go back and refresh yourself on basic acoustics, and room interaction amoung speakers and subwoofers. Doing so will probably make you embarrassed that you even posted this for all to see.

[Woochifer]

I think that all things aside with deciding between one sub or two, a more appropriate intermediate step would entail optimizing a single subwoofer setup and balancing out any room-induced problems before venturing into a second sub. Kex already mentioned room treatments, and related to that I would recommend attaching a parametric equalizer to the subwoofer output. Bass traps and equalization together will help to smooth out the frequency response and specifically address the acoustical effects caused by the room boundaries that can make your bass alternately sound boomy at certain frequencies and anemic at others.

Best part is that both solutions can be very economical and cost less than a second subwoofer. Commercial bass traps such as the Auralex LENRD start around $80, while more effective products from Real Traps and ASC cost upwards of $200+. A parametric equalizer will start around $100 (that would be the Behringer Feedback Destroyer, which is a pro audio processor that happens to be the least expensive PEQ I've seen and works fine for subwoofer equalizing).

A two sub setup can help aleviate some of the acoustical issues, but you need to have flexibility in the placement. But, one thing at a time. If you already own a subwoofer, the logical next step is to measure your bass response and identify any issues that your room is currently creating. Once you correct any existing issues, THEN you can explore any potental benefits that a second sub would bring to your system.

[westcott]

It might serve you well to go back and refresh yourself on basic acoustics, and room interaction amoung speakers and subwoofers. Doing so will probably make you embarrassed that you even posted this for all to see.

You could have gone all day without saying that! Shame, Shame!

[Sir Terrence the Terrible]

You could have gone all day without saying that! Shame, Shame!

And Shame, Shame, Shame on you for posting that inaccurate response. LOL

[westcott]

And Shame, Shame, Shame on you for posting that inaccurate response. LOL

I was not inaccurate. You assume too much. The opposing corner is not the best sound from a subwoofer if your subwoofer is not placed in a corner! We are not talking about imaging, we are talking about getting the cleanest sound from your system using a subwoofer, not the loudest.

Here's a link for Dr. Toole himself showing multiple subwoofer placements and it sure does look like what I described.

http://www.audiovideointeriors.com/interiorideas/0106toole/index1.html

P.S. Where's the Spyder?

[superpanavision70mm]

What type of low frequency are you getting from your main speakers? My two cents on this thread would be to inquire about off-setting your main speakers with your subs. Ever since I bought my PSB Image 7PT's with built in powered subs I have really no need for my subwoofer anymore...I get loads of bass and it's refined and smooth. The sub merely makes use of the 5.1 setup.

[JoeE SP9]

I have 3 subs. I have a sub for each front speaker crossed over at 80Hz. I have the third sub connected and positioned with my rear speakers. It is crossed over at 80Hz. The two front subs are almost in the front corners. The rear sub is almost against the rear wall. Having "extra" subs has not given me more bass but better bass. The ability to move more air makes a difference.:cool:

[Sir Terrence the Terrible]

I was not inaccurate. You assume too much. The opposing corner is not the best sound from a subwoofer if your subwoofer is not placed in a corner! We are not talking about imaging, we are talking about getting the cleanest sound from your system using a subwoofer, not the loudest.

Here's a link for Dr. Toole himself showing multiple subwoofer placements and it sure does look like what I described.

http://www.audiovideointeriors.com/interiorideas/0106toole/index1.html

P.S. Where's the Spyder?

It is a long standing practice of mine to never assume anything. It is also a huge mistake to post a link to an article that is not complete, and doesn't provide context to the picture.

This article pulled images from a white paper by Tim Welti, not Dr Toole. Secondly the article did not provide any measurements associtated to any of the placement they list. Had they did, and compared these positions to corner placement (we are only talking about non corner placements) it would have resulted in quite a different read. So lets put the measurements attained from the white paper to the pictures, and compare them to a sub or subs placed in corners.

Going from left to right, the first image produces a relatively smooth frequency response above 40hz, but below that rolls off very rapidly with a variation of about 19.7db. When compared to a single sub in a corner the two subs produced a marginally smoother response above 40hz (it probably wouldn't be audible according to the paper), but the single sub in the corner measured MUCH better below 40hz, with strong output down to its box tuning point. In this case 20hz. The two subs placed midwall had a much higher distortion figure than the single sub below 40hz. They were also more localizeable than the single sub. This observation also applied to the second placement in your link.

The third picture also produced a very good 40-80hz measurement, were not as localizeableable as two or three subs located at mid position, but suffered the same LF penalty as the other midwall placement which also produce a roll off below 40hz. These four subs placed mid wall produce a slightly higher distortion figure below 40hz than a single sub in a corner.

The fourth picture measured the worst, but produce the deepest, loudest bass with the lowest distortion of all placements, including the single sub in the corner. This was totally expect as each sub was loading the room from different points in the room. Two subs in the front two corners measured MUCH better, but had less output below 40hz, but suffered no LF penalty like the midwall placed subs.

The last one also produced a relatively smooth output above 40hz, played a little louder that the mid wall position which also meant it had lower distortion figures than the mid wall placements, but also suffered from a LF penalty below 40hz, but not quite as bad as the midwall placed subs. I suspect that driver coupling helped this position to perform better than the more widely spaced mid wall placement.

When you summed the full white paper's conclusions, two subwoofer in the front two corner measured as well as four at mid points along the walls. They had lower distortion, and no LF penalty which wasn't the case for the 4 midwall placements. Higher distortion figures do not equal cleaner output. Each measurement shows that whether you used 1 or 4 midwall placement, they will always have a higher distortion figure than 1 or 2 corner placed subs. Neither Tim's, or Dr Toole's papers support your contention that a midwall placement produces cleaner output. Cleaner output only comes when a sub driver doesn't exceed its linear travel, and the amps are not clipping, or near clipping. It is well known that a sub that doesn't utilize any boundary reinforcement will push both the driver and the amp harder to attain X level than a sub in a corner. A sub pushed away from all walls will measure poorly compared to a sub in a corner.

All of these observations and test where done in a rectangular room. All bet's are off in non rectangular rooms, and room that are rectangular, but have a generally open floor plan. All test were ran with a single signal distributed to all subwoofers much like you would get in a LFE channel. Different bass signal at different frequencies distributed to multiple subs changes the equation quite a bit.

All of these placements are based on microphone measurements. There has been no actually listening test to confirm the value of the actual measurements. That is very important to remember. Also all of the measurements were based on the listening position of center of room, or center rear in the room. That makes this test not a practical reference for a great many people.

P.S. The spydar is in Oakland, I am in San Diego. We will be in the same place on Monday.

[westcott]

It is a long standing practice of mine to never assume anything. It is also a huge mistake to post a link to an article that is not complete, and doesn't provide context to the picture.

If you looked at the bottom of the page, you would find the complete article. But here it is if anyone wants to read it that did not see it attached.

http://www.audiovideointeriors.com/images/archivesart/0106toolemultsubs.pdf



This article pulled images from a white paper by Tim Welti, not Dr Toole. Secondly the article did not provide any measurements associtated to any of the placement they list. Had they did, and compared these positions to corner placement (we are only talking about non corner placements) it would have resulted in quite a different read. So lets put the measurements attained from the white paper to the pictures, and compare them to a sub or subs placed in corners.
If you look at page 3, it clearly states that the first goal is minimize low frequency response variation.

Your SECOND priority should be to maximize low frequency output of your subwoofers.




Going from left to right, the first image produces a relatively smooth frequency response above 40hz, but below that rolls off very rapidly with a variation of about 19.7db. When compared to a single sub in a corner the two subs produced a marginally smoother response above 40hz (it probably wouldn't be audible according to the paper), but the single sub in the corner measured MUCH better below 40hz, with strong output down to its box tuning point. In this case 20hz. The two subs placed midwall had a much higher distortion figure than the single sub below 40hz. They were also more localizeable than the single sub. This observation also applied to the second placement in your link.
.
]

All the conclusions drawn from this paper are summed up on page 24, 25, and 26 where testing was conducted with the seating positions weighted that were 2\3rds the way back in the room which has always been the recommended seating position in a rectangular room and the conclusion I stated that corner placement was not the best, was concluded as well.

As I stated from the beginning, I was not interested in this discussion because it is a very hard to convince people that what they know about subwoofer placement is not ideal and that their sub has compromises, just like almost ever speaker I have ever heard or seen. It is amazing to me that after submitting the material from a reliable source supporting my statements that one can not admite that I was NOT inaccurate and that everything I stated was accurate. You may not like what the studies have to say but that is something different and something I knew when this debacle first started.

This thread dealt specifically with multiple subs and the data I quoted and presented was accurate and supported by credible sources and your comments were out of line.


Panny,

If you were asking me if I tried placing the subwoofer opposing my front mains, I did. You are very astute if I understand your comments correctly because the placement you described did provide the best frequency response in my room. Unfortunately, my back wall is open to the kitchen so leaving the subwoofer there was not practical. In fact, the front and the right side of the room were the only real options and the right wall was used as a corridor so that was nixed. The RF7's are rate to 29HZ and my subwoofer crossover is set to 60Hz.

[Sir Terrence the Terrible]

If you looked at the bottom of the page, you would find the complete article. But here it is if anyone wants to read it that did not see it attached.

http://www.audiovideointeriors.com/images/archivesart/0106toolemultsubs.pdf

Okay, first the devil is in the detail. Read where it states that these simulation are in a 20x24x9' room. That means that only in that size room those results were acheived, and it is possible to acheive those results of all things were the same. How many people do you know who have a room with these exact deminisions that can use this specific information? In this virtual room, using this model achieves this result. Doesn't apply to real world rooms that are often more square than rectangular. It also doesn't apply to open architecture designs as well. As I have said before, it is misleading to present a document that only applies to a specific application, a application most folks cannot support.



If you look at page 3, it clearly states that the first goal is minimize low frequency response variation. That would imply that

Your SECOND priority should be to maximize low frequency output of your subwoofers.

Unfortunately in all of your examples the low frequency support is lacking, which leads to a response variation. Remember they are testing for averages, so the frequencies between 40-80hz could be extremely flat, with a roll off below that point, and still be considered optimal in this tests point of view. And a response that is less flat from 40-80hz and has better support below 40hz could be deemed inferior based on the parimeters of this testing methodology. The exact words of your example state "One woofer at each mid point is best in terms of std max-ave and max-min, but does not support LF particularly well". Excuse me, don't want LF support? If we want less cone excursion, and less strain on the amps, we sure in the hell do!


]


All the conclusions drawn from this paper are summed up on page 24, 25, and 26 where testing was conducted with the seating positions weighted that were 2\3rds the way back in the room which has always been the recommended seating position in a rectangular room and the conclusion I stated that corner placement was not the best, was concluded as well.

Just how many of audioreviews members have a perfectly rectangular room that is completely inclosed? I would surmise not very many. How many overall have the space to place their listening positions exactly at this virtual rooms position? It is very wise when recomending sub placement that you use recomendation that can be applied to many different kinds of rooms, not just one kind with one seating position distance. It is also wise to recomend a position that work on reducing the load to the driver and amp, along with acheiving both a satisfactory frequency response and strong LF support. Your example does not fulfill but one of these parimeters.




As I stated from the beginning, I was not interested in this discussion because it is a very hard to convince people that what they know about subwoofer placement is not ideal and that their sub has compromises, just like almost ever speaker I have ever heard or seen. It is amazing to me that after submitting the material from a reliable source supporting my statements that one can not admite that I was NOT inaccurate and that everything I stated was accurate. You may not like what the studies have to say but that is something different and something I knew when this debacle first started.

You cannot convince me because your example is so specific to the testing objective and the room itself, not real rooms where real people sit and listen. You are attempting to compartimintalize the aspects of subwoofer positions without recongnizing their are other seating and placement options to be considered along with optimum subwoofer performance as well. Your example also states that more work needs to be done on these metrics (in other words they are not finished or optimized for real world rooms) nor does it take into consideration actual frequency response of each position, and a comparison to more corner options, nor does it take into consideration distortion levels in the driver and amps with each placement. This is VERY important if you are going to talk about CLEAN bass. There are also no listening test to quantify Tim conclusions. In the end, this counts the most. Measurements without corresponding listening test to quantify those measurements is only half the story being told. His test also doesn't identify equipment used. To use this as an example of optimum placement is misleading at its core, and I would not recommend everyone going for thiese exact placement without taking into consideration the context of your example. Lastly his placement tries to avoid the use of EQ which in the real world, with consumer equipment is virtually impossible to do. His test quantifies one parimeter (smooth response no LF support) from anoung several required to optimize sub performance.

Now if you want to directly read what Dr. Toole says on this issue (as opposed to other engineers at Harman with his input) read this link.

http://www.infinitysystems.com/homeaudio/technology/whitepapers/inf-rooms_3.pdf

Read very carefully to how he states you get good LF performance, and I quote "1)Maximize the output from the subwoofer (you do this by putting the sub in a high pressure zone or better stated the corners) 2) Acheive a uniform frequency response over the listening area, and 3) most importantly for most folks, EQUALIZE to acheive good performance. These are exactly what I state in my previous posts.

His paper is more appicable to a wide assortment of rooms, addresses real world condition, and lastly is much more pertanent for a wide assortment of listening preferences. These are things your example does not address.

Here is another by Dr. Toole which supports my assertions, and by the way is his own words, and not by another

http://www.infinitysystems.com/homeaudio/technology/whitepapers/acoustical_design.pdf

Here is another with actual measurements in a real room with different subwoofer locations. You will see clearly that the mid wall positions have noticeable depressionss between 40-80hz with a rising responsing thereafter. Notice the corner placements have a smooth rising response from the crossover point upwards. Different measurements, different room, different equipment=different results.

As you can see, my assertion are supported by Dr Toole, Alan Lofft, and if you get a chance, see if you can find Tom Nousiane white papers which takes a look at different room shapes and sizes and different sub placement within these rooms.. One loft, one L shape room, rectangle, square and a open floor plan. All of his test came to the conclusion that the corner was the best place for the sub in a wide variety of room designs and shapes. All of these do support my assertions that the corner is the BEST place OVERALL for sub performance, not just one parimeter as Tim Weil paper supports.

Thank you and good night!


This thread dealt specifically with multiple subs and the data I quoted and presented was accurate and supported by credible sources and your comments were out of line.

A credible source, not sources. Yes it was accurate for his test criteria, but not for OVERALL performance. And as you can see there are opposing positions, and one from a much more credible source than what you provide, Dr. Toole HIMSELF! So that makes my comments quite inline, and your assertion they weren't quite out of line!

I have quite a few more resources if you would like to continue this discourse.

[BRANDONH]

That second sub out on my NAD T773 has always begged me to wonder about the merits of having 2 subs versus one. For example, are there benefits to having 2 equal distance from the listening/viewing location (symmetrical), rather than one to one side (assymetrical)? Of course, cost is an issues, but perhaps 2 lower cost subs can surpass 1 expensive sub? Maybe subs are not "additive" and a second does not add much; or maybe 2 would be awesome? And then I can only wonder if there are issues with cancelation, etc., such that positioning is really critical? Anyhow, thought it would be fun to pose the 1 versus 2 question to the audience.

Yeah I decided to build two and place them in the corners.
All I can say it that there is a 100 percent improvement, talk about theater level bass wow!!
But mostly I did it for more dynamic impact for music, and it did the trick.
I also no longer use the LFE, split the left and right channel preout to the line left and right inputs using a Y at the plate amps and used their internal crossovers, reversed the polarity to fire backwards on the sub so not to interfere with the woofers firing frontwards on the main speakers and that worked very well, (of corce I tried it both ways)
I too have read and heard that adding a second sub would only add 3 db.
So without an SPL meter I can not say for sure that it yielded more than 3 db, but it sure sounds and feels like it is at least double the bass and loudness.
here is a pic:

http://img506.imageshack.us/img506/1120/spk28bn.th.jpg (http://img506.imageshack.us/my.php?image=spk28bn.jpg)

http://img515.imageshack.us/img515/2462/spk13mm.th.jpg (http://img515.imageshack.us/my.php?image=spk13mm.jpg)

below is a link my gallery to see how it is setup.
http://gallery.audioreview.com/showgallery.php?cat=500&ppuser=239881