[Nuance]

Right - I know it can flatten response, but I wasn't positive it could reduce ringing.  That's pretty cool. 

So now I am confused: I thought Earl was one of the proponents of phase not being of importance.  Perhaps I am confusing him with someone else? 

[James Romeyn]

IMHO, the state of the audio art, contrary to traditional belief, is defined by a system with multiple subs, multiple meaning three or more (I use four).  In other words, a so-called "fullrange" speaker system, one in which subs are not employed, is at least one clear step down in performance vs. one with a multiple sub setup.

The only known exception to the above rule is a fullrange system with a pair of sub towers with many multiple drivers in each tower running almost continuously from the floor up to the ceiling or close thereto.  Such a system cancels the worse mode, being the floor-ceiling bounce, and takes up so much physical real estate/volume in the room that it tends to further break up other modes beyond the floor-ceiling bounce.

 I know the above is diametrically opposed to all audiophile tradition.  My current room's modes were so awful that Earl Geddes' and Duke LeJeune's teachings on the subject were the only viable option for low bass reproduction. 

Till you try it you will not believe it possible to set a sub XO at such a high frequency (above 100 Hz) with no directionality effects.  Duke's SWARM is easily the best current sub extant unless one is willing to locate a pair of gargantuan and far more costly towers in one's room. 

A professional acoustics designer prescribed the more classic OC703 mode cures for my last room, comprising the retail equivalent of about $7k worth of ASC acoustic soffit and other mods.  Earl's/Duke's theories are immeasurably better at flattening modes, require no room mods, and offer another exclusive benefit: the acoustic quality of bass reproduced in a commercial (large) space. 

I also have experience with electronic digital EQ to flatten modes; with no offense to believers in that technology, it causes as many problems as it cures unless one is completely happy with more or less flat bass response in one very small location in one's room.

In my current room one can walk into every accessible floor space area with very little to no audible change in bass response.

Lastly, the truly awful thing about using a lot of OC703 (last room had several hundred dollars value wholesale prices), even when treated to maintain reflectivity of higher frequencies as did my OC703, is that it just gets way too dry sounding in the bass, loosing the wonderful "elastic" sound bass has in commercial spaces (pay close attention the next movie house you visit).

My 2 cayics. 

     

 

     

[TONEPUB]

Why is it "blasphemy" to use a subwoofer?

Love my Gotham, wouldn't part with it.

[James Romeyn]

I completely understand everything that is being said- but cannot get over the thought that a mono sub system is oversimplified, even with multiple placements. I think it must improve many things and sacrifice others.

I listen to allot of bluegrass. There are times when bass is stronger out of one or the other channel. (AKA: Stereo separation) I don't want a sub smearing it all over the place. If it's supposed to be in the left channel, shouldn't we keep it there? I don't want it all over the place. Same goes for the other recording I mentioned earlier on.

The best advice would be to sample the multi mono sub system.  I don't hear the downside you theorize exists in any way shape or form.  The subs are non-directional even with the LPXO pole above 100Hz (at least, as Duke states, when the mains are running).  My mains are active HPX'd at 80 Hz; sorry I don't know the slope.  There's only one octave below 80 Hz down to 41 Hz, being the open low E on the bass guitar or acoustic/double bass (though these instruments may produce sub-harmonics, plus some bass players employ octave effects that synthesize output below the instrument's true fundamental).

I play bluegrass and saw Doc Watson in his prime many times; even the last time about six years ago the audience gasps were still there.   

[turkey]

I don't "cross over" to subs. I run my main speakers full-range, and then I have 3 subs with varying LP crossover points.

[ctviggen]

I suspect you are hearing things higher than 150 Hz. It is generally agreed that that is the lower limit for localization (as long as there are no harmonics and nothing is rattling).

In my experience, with one sub and crossing over at 80Hz, it's extremely easy to locate that sub.  Whether that's because of harmonics or not, I don't know.

Personally, I'm going to try two subs, one in a corner and one along a wall.  I'm going to leave my main speakers full range.  I'll then add in a third sub later. 

[rollo]

 A major improvement in bass came when I tried the ASC recco of raising the Sub off the floor to 22% of the room height. Before that a big improvement was wrought by just turning the floor firing sub over. The driver facing the clg. Now located at 22% of room height the bass has never been better intergrated in my system. You only hear bass when its present. Check it out. It is worth the experiment. Have fun. BTw a Berhinger EQ works wonders on the bass as well, when used STRICTLY for the bass.


charles

[JimJ]

News to me that it's blasphemy...

[Hebrew Hammer]

harmonics past the fundamental xover point caused this.. lower the xover point or try a steeper slope

i'm w/niteshade on this point.  i have been able to localize a mono sub, even when crossed over as low as 80hz.  the only time i have heard a mono sub not degrade soundstaging is when it is centered directly between the mains, preferably in the nearfield.  but, stereo subs, imo, improve soundstaging, instead of not simply degrading it.  i have never heard mono multiple subs done per gedlee; maybe my opinion would change.  but, i'd still be more apt to run multiple subs in stereo.

doug s.

[James Romeyn]

I completely understand everything that is being said- but cannot get over the thought that a mono sub system is oversimplified, even with multiple placements. I think it must improve many things and sacrifice others.

I listen to allot of bluegrass. There are times when bass is stronger out of one or the other channel. (AKA: Stereo separation) I don't want a sub smearing it all over the place. If it's supposed to be in the left channel, shouldn't we keep it there? I don't want it all over the place. Same goes for the other recording I mentioned earlier on.

Sorry for exceeding the usual limit of one reply to a post...no intent to pile on.  The perceived stereo separation of stringed bass instruments, especially for notes with fundamental tones below 100-150 Hz, is from the overtone structure and not the fundamental tone. 

Plucked/bowed/picked string instruments reproduce the entire overtone structure, meaning even a 41 Hz low E (in normal tuning the lowest note of a 4-string bass) has overtones well beyond 100 Hz; without looking it up I'd guesstimate audible overtones over 1k Hz (the instruments' distinct "attack" would also extend up to much higher frequencies).  Almost up to the instruments' 2nd octave fundamental, any localization is from the attack and harmonics and not the fundamental.  This may be a fairly important point to get.   

[ctviggen]

harmonics past the fundamental xover point caused this.. lower the xover point or try a steeper slope

And how do you know this? 

[ctviggen]

I ask because regardless of the sub I used, I can locate a single sub. 

[turkey]

And how do you know this?

Note that it's also possible for the sub itself to be producing the content at higher frequencies, so tweaking the crossover would not work. You'd just have to get a better sub, or a better amp to drive it with, depending on where the distortion is coming from.

Barring a defective sub, and given a proper crossover that keeps higher frequencies out of the sub, you can't hear where the sub is in a normal home listening room.

[Wayner]

I ask because regardless of the sub I used, I can locate a single sub.

Find one that fires downward.

W

[Wayner]

Here is a link to a typical subwoofer's specifications on frequency response: http://www.madisound.com/catalog/product_info.php?cPath=45_338_381&products_id=8434

Download the PDF and you'll find that most subs go out to 1.5K-2K. They are then duplicating what your mains are creating. Xover at 80-whatever, will not stop the dual reproduction, and blurring the lowest frequencys of the music. Your using the "wall of sound" theory in your systems and because it kind of sounds full, does not mean it's accurate. It's 180 degrees the other way of the simple speaker systems.

Wayner

[turkey]

Yes, changing the phase of one or more subs can flatten the overall response and reduce ringing at the major modes. In my experience the effect was relatively small, but this is certainly one of the recommended tools for optimizing the overall system response.  Perhaps Earl can add some more detail.

I don't see that this will do much at low frequencies. As Earl said in the other thread, "For a typical listening room below about 100 Hz and all locaization is lost because there are so many reflections within a single period of a sound wave that the sound is, for all oractical purposes, coming at you from everywhere."

[turkey]

Here is a link to a typical subwoofer's specifications on frequency response: http://www.madisound.com/catalog/product_info.php?cPath=45_338_381&products_id=8434

Download the PDF and you'll find that most subs go out to 1.5K-2K. They are then duplicating what your mains are creating. Xover at 80-whatever, will not stop the dual reproduction, and blurring the lowest frequencys of the music. Your using the "wall of sound" theory in your systems and because it kind of sounds full, does not mean it's accurate. It's 180 degrees the other way of the simple speaker systems.

Wayner

I'm not sure what you're saying here. Are you saying that using multiple subs causes loss of accuracy?

[Wayner]

No. If the left main speaker is producing a tone at 1.5K, then the subwoofer is also creating a tone at 1.5k, and doubling the output from cross over to fade out of the woofer, creating a hump in freq. in that zone. it's also getting close to that all important low band midrange that IMHO, is the heart of the music. Now add a sub that is out of phase and OMG, we just have a barrage of stuff heading towards the listener.

Wayner

[Wayner]

Then you will need another cross-over (to nowhere up about an octave) to kill everything above useful subwoofer stuff. Like kill everything above 320hz.

Wayner

[Duke]

If the left main speaker is producing a tone at 1.5K, then the subwoofer is also creating a tone at 1.5k...

If the sub has a 24 dB per octave crossover at 100 Hz, its output will be down by about 100 dB at 1.5 kHz.

Now add a sub that is out of phase and OMG, we just have a barrage of stuff heading towards the listener.

The ear does not process sound like I think you are envisioning; much of it is counter-intuitive.  De-correlation at low frequencies is desirable in most situations.