Highest frequency that cannot be "localized" by the ear?

[edlchiang62]

Sorry to ask a basic question, but what is the generally accepted highest frequency that humans can hear and still appear to be "omni-directional" to humans?

[kexodusc]

This is open to much debate. I've read anywhere from 70 to 120 Hz. My own experience is that it is closer to 110 Hz. But there's a catch. Often, the localizing cues we perceive when a subwoofer or speaker plays these notes isn't the frequency itself, but the harmonics, vibrations, interactions with room, etc. Your senses are pretty clever, and will hear the impacts of the released energy near the subwoofer, and hence direct your attention to that area. Play a 20 Hz tone sometime through your sub (or lowest it's safely capable of)...often your senses will direct you to the source...not just hearing, but everything.

With an A/V receiver, or subwoofer plate amp, look for crossovers or LFE cutoffs with steep acoustic slopes. 24 dB/octave. Many are still 12 dB/octave. No good IMO. Even 24 dB/octave still plays a lot of information above the so called "cutoff" frequency. Sometimes we're hearing these higher frequencies and mistaking it as 90 Hz being directional.

Often overlooked is the simple factor of the size of the room, your postion in the room and your position relative the subwoofer. If you're sitting near a mode or node, response will be affected quite a bit when moving even a few inches. The thing about non-directional frequencies is the size of the wavelengths. 90 Hz is 12 feet. If you're +/- 6 feet of axis, you can expect some major discrepencies between what you hear in your left and right ears. 80 Hz is almost 14 feet. 70 Hz almost 16 feet.

I guess my point here after all this rambling is that what's non-directional in your setup, might be easily localized in another room. Experiment.

[Richard Greene]

Assuming almost all the bass above 80Hz. is coming from the satellite speakers, and the subwoofer is located in the vicinity of one or both main speakers (not alone in a far corner someone):

I recommend output at 160Hz. down at least 24dB versus bass output under 80Hz, (I personally prefer even less subwoofer output above 80Hz.)

We hear the location of the subwoofer from the output in the 80-160Hz. octave (which can be significant if low-pass filters are not at least 24dB/octave slope, with a turnover frequency no higher than 80Hz.).

With all other speakers turned off you can feel the sound pressure from a subwoofer and at least identify the side of the room it's located on AT ANY FREQUENCY.

You can feel a subwoofer behind you.

That's why for the best integration with the main speakers, subwoofers should be located near one main speaker, or between two main speakers.

[RGA]

Perhaps this is the explanation from Richard Greene. The only time a subwoofer was remotely convincing - even ones set up by professionals was when the sub was directly between the two speakers (which then makes it totally impractical. The toher was when one sub was behind each speaker.

Never ever ever have I been convinced by a system using one subwoofer not in the dead center between the two main speakers -- one sub on the left is heard from the left ALWAYS. Still I like them when something explodes in a movie.

[ruadmaa]

Perhaps this is the explanation from Richard Greene. The only time a subwoofer was remotely convincing - even ones set up by professionals was when the sub was directly between the two speakers (which then makes it totally impractical. The toher was when one sub was behind each speaker.

Never ever ever have I been convinced by a system using one subwoofer not in the dead center between the two main speakers -- one sub on the left is heard from the left ALWAYS. Still I like them when something explodes in a movie.

Sorry RGA, I strongly disagree with you. I use a 12 inch M&K powered subwoofer located on the far right front side of my room beside a sofa, and to date not one person has ever even known that a powered subwoofer was being used (in addition to the the two front 12 inch 4 way towers) that I use. The subwoofer is desquised as a lamp stand and draws no attention to itself. I suggest that mostly the eyes and mind are telling you where the subwoofer is. Frequencies of 80HZ or less are not locatable by hearing.

[RGA]

Sorry RGA, I strongly disagree with you. I use a 12 inch M&K powered subwoofer located on the far right front side of my room beside a sofa, and to date not one person has ever even known that a powered subwoofer was being used (in addition to the the two front 12 inch 4 way towers) that I use. The subwoofer is desquised as a lamp stand and draws no attention to itself. I suggest that mostly the eyes and mind are telling you where the subwoofer is. Frequencies of 80HZ or less are not locatable by hearing.

Run a test tone disc - have your eyes closed let someone set up the romk and run a 30hz tone through -- You will know where the sub is.

Music can take a fair bit longer because few music has any real bass - systems with a sub don;t integrate properly and sooner or later the ear drifts to where the sub is. In a short term listening test maybe not, but then the $20.00 computer speakers on the table with the sub on the floor fooled me for a few minutes too in that gee it sounded klike it was coming from the speaker -- and this is way way about 80hz.

And it's funny you mention M&K because THAT was the set-up with the sub in the middle that I was referring to. The dealer, who's father invented the sand filling speaker for Wharfedale, had Lucas as a client. The problem was that the sub in the center created a weight always int he center and the dealer rarely wanted to play anything other than a drum solo -- this music sounded great but heavier voices and a lack of left to right depth. Ultimately it was a bit of a boom and sizzle experience. Other sub set-ups in the corners namely with B&W N801 sounded dead - one note bass. If I have a complaint, aside from not meshing with the speakers is the kind of bass -- I either get fake added ambiance to everything (which i admit can sound pleasing enough) or I get an obvious tranfer.to one side of the room or a heavier weighted balance to one side of the room -- someone mentioned drums in the left corner if the sub is in the left corner -- umm that ain;t great when the drums are supposed to be on the other side.

My main experience with subs was with a Boston Acoustics SW 10 long throw powered sub. I can forgive many problems but it's problem is that it could not outdo the Wharfedale's bass depth. It could be run passive or with its power and powered it "alleviated" the Wharfedales from the task of providing the bass - The sound was terrible in this mode - boom and sizzle -- I could hear more "air" in the Wharfedale more midrange and treble but umm that's about it along with the subwoofer.

Good speakers don't need to be alleviated from their job -letting the receiver run everything sounded much better but then I ran into the problem that the sub didn't add any bass so I basically gave up on the thing.

Heard many new supposedly better subwoofer designs - but I am not going to BUY one until a dealer can prove to me that they will add musical value to the bottom end rather than one note bass or "slam" which isn't at all music but a throbbing impress your friends "wow that's cool" pyrotechnic. (like I say great for movies) not been convinced for music though I will agree that subs often help out a lot of unnaceptably aneamic speakers.

[theaudiohobby]

Run a test tone disc - have your eyes closed let someone set up the romk and run a 30hz tone through -- You will know where the sub is.

It is a '30Hz test tone! i.e. a single fundamental with no harmonics,it will be primarily audible through the subwoofer! Talk about stating the obvious ! At this point, your J's are several db down or not producing any sound at all, so sure you will locate the sub, try the same test with a music program, the outcome will be very different, if the crossover to the sub is sufficiently low.

[ruadmaa]

Run a test tone disc - have your eyes closed let someone set up the romk and run a 30hz tone through -- You will know where the sub is.

Music can take a fair bit longer because few music has any real bass - systems with a sub don;t integrate properly and sooner or later the ear drifts to where the sub is. In a short term listening test maybe not, but then the $20.00 computer speakers on the table with the sub on the floor fooled me for a few minutes too in that gee it sounded klike it was coming from the speaker -- and this is way way about 80hz.

And it's funny you mention M&K because THAT was the set-up with the sub in the middle that I was referring to. The dealer, who's father invented the sand filling speaker for Wharfedale, had Lucas as a client. The problem was that the sub in the center created a weight always int he center and the dealer rarely wanted to play anything other than a drum solo -- this music sounded great but heavier voices and a lack of left to right depth. Ultimately it was a bit of a boom and sizzle experience. Other sub set-ups in the corners namely with B&W N801 sounded dead - one note bass. If I have a complaint, aside from not meshing with the speakers is the kind of bass -- I either get fake added ambiance to everything (which i admit can sound pleasing enough) or I get an obvious tranfer.to one side of the room or a heavier weighted balance to one side of the room -- someone mentioned drums in the left corner if the sub is in the left corner -- umm that ain;t great when the drums are supposed to be on the other side.

My main experience with subs was with a Boston Acoustics SW 10 long throw powered sub. I can forgive many problems but it's problem is that it could not outdo the Wharfedale's bass depth. It could be run passive or with its power and powered it "alleviated" the Wharfedales from the task of providing the bass - The sound was terrible in this mode - boom and sizzle -- I could hear more "air" in the Wharfedale more midrange and treble but umm that's about it along with the subwoofer.

Good speakers don't need to be alleviated from their job -letting the receiver run everything sounded much better but then I ran into the problem that the sub didn't add any bass so I basically gave up on the thing.

Heard many new supposedly better subwoofer designs - but I am not going to BUY one until a dealer can prove to me that they will add musical value to the bottom end rather than one note bass or "slam" which isn't at all music but a throbbing impress your friends "wow that's cool" pyrotechnic. (like I say great for movies) not been convinced for music though I will agree that subs often help out a lot of unnaceptably aneamic speakers.

Sorry again RGA, I don't run test tones on my system other than for system setup, I run both music and movies . No one has ever been able to spot the subwoofer. Quite frankly, you wouldn't be able to locate it either, even if you were listening for it. I have listened to my system quite critically many times, there is no clue that a sub is being used.

[edlchiang62]

So am I corrrect to assume then for the best two channel system in which I cannot place the subwoofer inbetween the speakers (becasue of a tv), it is best two have a pair of subwoofers in which they are located near each monitor speaker. In other words I should not have a singe subwoofer in the corner of a room?

[kexodusc]

Corner loading a subwoofer can introduce some uneven response patterns throughout the room. I guess, depending on your room, adding a second sub in the opposite corner might compensate for that.
I'm convinced there's at least some benefit to running two subwoofers, even if there is no "stereo" effect. Problem is on a pounding bass drum, you might sense two separate sources of the drum, 1 in each corner, which isn't what a drum is doing. Your sense of "feel" for the bass won't create a virtual image in the same manner your ears interpret sound.

Don't discount room size and your proximity to the sub either. In my smaller studio, my sub easily gives itself away, and like RGA said, there were some challenges trying to add more bass into my 2-channel system. For some music, particularly acoustic music, it worked rather well. For rock, it didn't work as well. I ended up abandonning it for space saving reasons. My towers play down to 28 Hz or so anyway and though my sub is a bit more "musical", it took up too much space.

In my 20 X 24 room, I have the sub on the inside of one of my front main speakers. I listen to 2 channel stereo a lot in this room too. I'm about 11.5 feet from the subwoofer, near the center of my room. I honestly can't determine it's location until the walls in the surrounding area rattle and give it away. As I move closer, I can feel the energy it gives off.

I think for most, 1 subwoofer is fine, if you can do 2 subs, go for it. But just accept that the extra subwoofer's cost is only going to improve things a bit. For the cost of 2 subs in a stereo system, especially with space requirements, you might be better off to evaluate doing a speaker upgrade?

[Sir Terrence the Terrible]

So am I corrrect to assume then for the best two channel system in which I cannot place the subwoofer inbetween the speakers (becasue of a tv), it is best two have a pair of subwoofers in which they are located near each monitor speaker. In other words I should not have a singe subwoofer in the corner of a room?

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best. A subwoofer sitting between two main speakers is not likely to excite any of the rooms modes efficiently which will cause some some suckouts in the frequency response at the listening position. According to his testing, a subwoofer SHOULD excite all of the rooms modals to measure and sound good. While placing a sub between the mains may assist in better integrations with the mains, it will likely cause the frequency response of the sub to be uneven.

[kexodusc]

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best. A subwoofer sitting between two main speakers is not likely to excite any of the rooms modes efficiently which will cause some some suckouts in the frequency response at the listening position. According to his testing, a subwoofer SHOULD excite all of the rooms modals to measure and sound good. While placing a sub between the mains may assist in better integrations with the mains, it will likely cause the frequency response of the sub to be uneven.

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

[3db]

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

Although my sub is located in a corner, its at the opposite end of the room to where my mains are located. That postion was found by putting the sub where my seating psotion was and crawlign around like an angry dog until I found the spot where the bass seemed the loudest. This room is 12'x16' with a 7ft drop ceiling, and burber carpet.

Now in my other house, the best bass response I achieved was smack dam in the middle of the short wall againsgt the wall. My speakers flanked the sub on either side. This room (family room) was open to the kitchen however. I can't help but think that room shape and size plays a huge roll into where the sub should go.

[Sir Terrence the Terrible]

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

Tom Nousiane papers are VERY difficult to find on the internet. Most of them are articles in audio magazine, or sound and vision back in the 90's. However as a memeber of AES, I am able to aquire quite a few of his papers through it, and CEDIA and THX use his work on subs to a great degree.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

Most experiments with room acoustics and standing waves have been on rectangular rooms only. I think the reason why it is important to locate subs in corners has more to do with maximum volume, low frequency extension, and most even measurements. Also consider that it is easier to cut a room mode(which corners stimulate all boundary related modes evenly) than it is to fill in a node which cannot be done without extreme penalties on amplifier headroom and overall output

[Pat D]

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

Some years ago, Stereo Review published an article on subwoofer placement by Mr. Nousaine. Unlike so many critics, he actually did the measurements and his work is widely accepted by the likes of Dr. Hsu, Tom Vodhanel, and others. Unfortunately I am not at home. If you want the reference, ask me next year.

Corner placement works best in most rectangular rooms giving the flattest and deepest response. Also, since the horn loads the sub, it requires less gain and can provide greater output levels.

There is a more general method. Place the sub in your listening position, preferably at your sitting level, and play some bass heavy music. Now, crawl around on your hands and knees to find those points in the room where the bass is loudest (probably close to the corners!). Next, place the sub in one of those places. Alan Lofft, who now answers questions on the Axiom site, describes this method in an article there. I'd link it except this silly computer I'm using makes it difficult to use multiple browsers.

[Sir Terrence the Terrible]

Some years ago, Stereo Review published an article on subwoofer placement by Mr. Nousaine. Unlike so many critics, he actually did the measurements and his work is widely accepted by the likes of Dr. Hsu, Tom Vodhanel, and others. Unfortunately I am not at home. If you want the reference, ask me next year.

Corner placement works best in most rectangular rooms giving the flattest and deepest response. Also, since the horn loads the sub, it requires less gain and can provide greater output levels.

There is a more general method. Place the sub in your listening position, preferably at your sitting level, and play some bass heavy music. Now, crawl around on your hands and knees to find those points in the room where the bass is loudest (probably close to the corners!). Next, place the sub in one of those places. Alan Lofft, who now answers questions on the Axiom site, describes this method in an article there. I'd link it except this silly computer I'm using makes it difficult to use multiple browsers.

I have that issue. He actually measure a sub in a L shaped room, and room with a loft, a regular rectangular room, a box shaped room, and a room with walls that jut in and out into the room. He stated that no sub should be located closer than 5ft to an opening. Corner loading provides 18db of boundary reinforcement at low frequencies.

[E-Stat]

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best.

Perhaps with all the qualifications RG stated, that would be the case. I suspect the modest 12" powered subs I use in my HT system do not utilize such a steep slope. Even when I set the sub's crossover to 70 hz sourced from the LFE output, I find two blend better than one.

Returning to the original question, I believe than unless you have largely full range speakers to begin with, buy a serious sub with an unusually steep crossover slope, you would be better off with a pair.

BTW, TtT - I notice you use a pair of 15 inchers.

rw

[Sir Terrence the Terrible]

Perhaps with all the qualifications RG stated, that would be the case. I suspect the modest 12" powered subs I use in my HT system do not utilize such a steep slope. Even when I set the sub's crossover to 70 hz sourced from the LFE output, I find two blend better than one.

If you have read the writings of both Richard Greene(who comes here sometimes now) and Tom, according to both of them the ideal crossover point for subwoofer invisibility would be around 60-80hz with a VERY steep 24dbpo crossover. This is the parimeter that Tom Nousiane followed during his measurement of those many rooms.

Returning to the original question, I believe than unless you have largely full range speakers to begin with, buy a serious sub with an unusually steep crossover slope, you would be better off with a pair.

BTW, TtT - I notice you use a pair of 15 inchers.

rw

If you place full range speakers where the bass response is augmented(closer to the walls) then imaging suffers because of the added and early arrival of nearfield reflections. If you place full range speakers to acheive maximum imaging, it is likely to roll off early, and create peaks and valley in its freqeuncy responses do to late arriving reflections combining with early arriving reflections. That is why subs are so important no matter which kind of speaker you use.

You are right, I do use a pair of 15". Not for any reason other than to fullfill my audio requirements that the LFE speakers have 6db headroom over the loudest peak within that channel. A single of my subs could easily reach the loudest potential of the LFE channel(115db peak acousticall). Two subs located in each of the front corners on the floor reaches my goal of 6db. I otherwise would have used a single sub in my room if I didn't have these requirements. I require that all speakers in my system be able to handle at least 6db of headroom over the highest peak in that channel. Consequently I use VERY big speakers all of the way around, although I wouldn't consider my surrounds full range as they only go down to 50hz. Considering that there is not always alot of deep bass in the surrounds, that is low enough IMO to run full range. Only in the rarest of occasions have I seen bass at very high levels below 50hz in the surrounds. In the dubbing stage the surrounds are band limited at 80hz anyway, except if its being mixed at Skywalker sound which have surrounds that go down to 50hz or so.

[E-Stat]

... the ideal crossover point for subwoofer invisibility would be around 60-80hz with a VERY steep 24dbpo crossover. This is the parimeter that Tom Nousiane followed during his measurement of those many rooms.

I think we're on the same page. Unfortunately, I would venture to say most reasonably priced subs intended for HT use do not have that steep a slope.

You are right, I do use a pair of 15". Not for any reason other than to fullfill my audio requirements that the LFE speakers have 6db headroom over the loudest peak within that channel.

That's also why Harry Pearson uses five in his Magneplanar based HT system! The waves crashing in the movie Blue Crush were quite convincing.

rw

[gonefishin]

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best. A subwoofer sitting between two main speakers is not likely to excite any of the rooms modes efficiently which will cause some some suckouts in the frequency response at the listening position. According to his testing, a subwoofer SHOULD excite all of the rooms modals to measure and sound good. While placing a sub between the mains may assist in better integrations with the mains, it will likely cause the frequency response of the sub to be uneven.

I wish I knew where the articles I had read were. I can't remember the specifics...but I thought that in one test (regarding placement of single and double subs of different types) he had concluded that there was better response not only just in the corner...but also concluded that two perform better near a corner than near each main speaker. Again...I'm going from memory...but I thought that was what he had said. I'll see if I could find it.

dan

[Sir Terrence the Terrible]

I wish I knew where the articles I had read were. I can't remember the specifics...but I thought that in one test (regarding placement of single and double subs of different types) he had concluded that there was better response not only just in the corner...but also concluded that two perform better near a corner than near each main speaker. Again...I'm going from memory...but I thought that was what he had said. I'll see if I could find it.

dan

This is true, and I cannot disagree with this. This follows along with a single sub in a corner. I believe he found that two subs stacked in the same corner provided 6db more output, and a smoother overall response from the combination than what you get my locating subs at each of the 5 speakers.. However if even bass coverage(at more than one seat) is what you desire, two spaced subs in opposite corners do this best.

[gonefishin]

This is true, and I cannot disagree with this. This follows along with a single sub in a corner. I believe he found that two subs stacked in the same corner provided 6db more output, and a smoother overall response from the combination than what you get my locating subs at each of the 5 speakers.. However if even bass coverage(at more than one seat) is what you desire, two spaced subs in opposite corners do this best.

Like I said...I was just trying to recall from memory what the article had said. Many of us...don't have the luxury of placement all the time...or we are limited in how flexible we can be with placement. But it's still nice to read what we may want to achieve in a similar shaped or sized room.

Pat (or others) if you've got any links...I'd like to read them...whenever you find them is fine...even if it's next year

I decided i will swim with the stream of fish since that is the only way to get accepted. I'll stick with my non-box anywhere in the systems policy

Oh...I would hardly say that I'm accepted.

I'm sorry for the rude comment I made (stats are fast comment)...I did know what you were trying to say. You would do very well by sticking exactly with what you have...but you know that

dan

[Resident Loser]

Sorry to ask a basic question, but what is the generally accepted highest frequency that humans can hear and still appear to be "omni-directional" to humans?

...between "omni-directional" and "non-directional"...subs should be considered the latter...anywho, around 150Hz may be the number...

Addressing other points of this thread:

FWIW, I tend to agree with Mssrs. Greene and RGA, with regard to placement of a sub...Since the sub's output is a mono summing of the lo-freqs, placement somewhere within the radiation field of the L&R speakers makes the most sense...preferably smack dab in the middle using one OR preferably two subs, one for each channel.

My rationale is: why would one want to perceive the lowest fundamentals from somewhere in the distance and the directional cues of their upper-harmonics from the appropriate loudspeaker?...I think it tends to obscure definition.

With regard to near-automatic placement in a corner, there are those who disagree or take some exception to...such as this from Audioholics, written by Alan Lofft of Axiom Audio:

"Instructions on getting good bass from a subwoofer in any given room usually begin by suggesting corner placement of the subwoofer. And it's true: placing the subwoofer in a corner will equally energize all the room's resonances and maximize the subwoofer's output. However, one of the more bizarre aspects of how subwoofers couple with the specific dimensions of a room -- is that to hear all the bass energy from the subwoofer in the corner of your room, you would have to sit in the corner diagonally opposite the subwoofer!"

The full text and some other really informative info(if a bit "techie" with charts and graphs) on the whys and wherefors of sub placement is available at:

http://www.audioholics.com/techtips/...lacementP1.php

Also this excerpt from PSB audio:

"As you go outward from the corner along one wall or another, the general consensus (with which we tend to agree) is that while bass output diminishes somewhat, it also becomes more uniform throughout the room, with fewer of the "standing waves" that produce peaks and nulls at various points. The consensus on this does not include Tom Nousaine, an extremely knowledgeable audio writer who probably has done more listening to subwoofers from an end-user's perspective than anyone else, along with lots of measurement. He finds that corner placement provides the most uniform bass output as well as the strongest bass, but our own experience, while it doesn't directly contradict his, is that away-from-the-corner placement produces better balance in many situations. In any event, the level, crossover, and phase controls give you immediate adjustments for changes as you go outward."

It's full text is at:

http://www.psbspeakers.com/audioTopics.php?fpId=7

IMHO, single, summing subs and/or corner placement may be OK if one is on a diet of electronica or head-banging tunes...perhaps HT with it's laser-totin' mechanical lizards, assorted crashes and various other forms of sonic mayhem...however once you start to listen to program material that is a bit more refined and demanding(volume not necessarily being considered a demand) the shortcomings of both schemes should be readily apparent.

P.S. For anyone interested...simply Google Tom Nousaine and the appropriate subject such as "Tom Nousaine on subwoofers"...no secret handshakes are required.

jimHJJ(...hey Pat D. long time, no see...)

[theaudiohobby]

...between "omni-directional" and "non-directional"...subs should be considered the latter...anywho, around 150Hz may be the number...

Addressing other points of this thread:

FWIW, I tend to agree with Mssrs. Greene and RGA, with regard to placement of a sub...Since the sub's output is a mono summing of the lo-freqs, placement somewhere within the radiation field of the L&R speakers makes the most sense...preferably smack dab in the middle using one OR preferably two subs, one for each channel.

My rationale is: why would one want to perceive the lowest fundamentals from somewhere in the distance and the directional cues of their upper-harmonics from the appropriate loudspeaker?...I think it tends to obscure definition.

If I may chime in, implicit in the suggestion of placing subwoofers in the middle of two main speakers is that sub-80Hz frequencies may be directional. If As Tom Nousaine found, sub-80Hz are non-directional, placement of the sub for the smoothest bass response will not necessarily be between main speakers. I was much surprised when I first realised that the subwoofer integrated more seamlessly with the main speakers, when placed closer to to the right speaker, it is almost directly behind the right speaker, this location closer to the right corner of the room. And as mentioned elsewhere in this thread the crossover frequency for both the subwoofer and the main speakers 63Hz. This experience correlates more closely with Tom Nousaine's observations about subwoofer placement rather than generally accepted audiophile wisdom.

As for the multiple subwoofers approach, it probably accrues benefits not from even bass loading but from the extra clarity that may be available when the bass frequencies from discrete channels are routed to discrete devices instead of summation into a single device. Ofcourse this assumes that the subwoofers in question are seamlessly integrated with the main speakers.

[Resident Loser]

If I may chime in, implicit in the suggestion of placing subwoofers in the middle of two main speakers is that sub-80Hz frequencies may be directional.

...they certainly are "stereo"...there may be something lost "in the mix", as it were, that may have a certain "directionality"(for lack of better words) factor.

Frankly, I was much surprised when I realised that the subwoofer integrated more seamlessly with the main speakers, when it was closer to to the right speaker, it is almost directly behind the right speaker. than closer to the right corner of the room...

If you listen to orchestral/operatic recordings, the answer would seem simple: just about ALL lo-freq instruments(double-bass, tympany, etc.) are to the conductors/listeners right...Phase and time coherence would all seem to play a part...Directional? Perhaps not, but certainly a real-world concern IMO.

There are those who think 20Hz-20kHz bandwidth(and the commensurate CD/digital sampling rate compromise) is sufficient...

jimHJJ(...and others who don't...)