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Bah, Humbug, almost no such thing.  There are a few very old recording and a scatter here and there but, 99% of music does not use stereo bass.  Stereo bass would make the stylus jump off the record.  If the speakers are accompanied by a nice sub, you will have all the stereo imaging, sound stage and depth needed for an excellent 2 ch system.

Edited by derrickdj1
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Unless you are crossing your subwoofer over at a higher than normal frequency i call bullshit on the whole stereo subwoofer myth.

So my center channel amp is a QSC  GX3 with a  built in  100 Hz, 3rd order LP (sub),  2nd order HP (top).

 

I get the center channel source from the PWK "bud box" from the 70's.

 

 

If you are referring to a 3 channel system with a center mono channel using the center output is fine to use for subwoofer input.

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I say 4.  I'm running Config 10 in the attached.  I also have never heard a localization effect in stereo below ~100 Hz, so I doubt it occurs.

 

Great PDF! From what I have looked into, configuration 10 and 11 are the best. I am running my sub at 180 deg. phase in the null in the middle of the room and it sounds good to me. It is important to realize too that while below 100hz is not able to be localized, the subwoofer's distortion is easy to localize and people should solve that issue first. 

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Most decent modern subs are not plagued by high distortion.  Localization with good subs is a problem of setup: some can be over come and others you may have to live with.  Close wall proximity can lead to localization due to harmonics.  Two to three ft from a wall is ideal but, not very practical.

Edited by derrickdj1
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Localization of bass seems just about impossible to me. Our receiving antennas are only about one foot apart.

In one Klipsch paper there is a transcript of a discussion by experts who thought that localization stops at about 400 Hz.

OTOH, there will be nodes created by one speaker working in a room. Recall is dim but I tried one speaker driven with a 200 Hz sine wave (maybe). Walking around the room at some location it seemed that the amp / speaker had stopped working. You will not believe this until you try it.

ome fellow here long ago also complained that he played some sine freq through is speakers and walked around the room with an RS meter to measure the level, and found it varied wildly.

So it is very possible that with a single sub, there will be comb filtering of frequencies (meaning that there are evenly spaced peaks and valleys) at the listening position.

The solution is to use two subs in different locations. As I recall, the best evening-out is the two in front corners. Just where PWK puts his corner horns.

After that there is the possibility of three subs and at least one of these go against a wall. But I guess that would lead to really wacko localization, should it exist.

The bottom line is that a single sub can't give you even response at a listening position in a room.

- - - -

Please remember that LFE is mono to begin with, not stereo.

LPs have an interesting issue of bass. IIRC, in stereo LPs, bass is mixed mono before the disk is cut for a reason.

IIRC, we know that the stereo signal in the groove is because the sensors in the pickup so that they are 90 degrees apart. The left wall of the groove (say left signal) moves diagonally to the center and the right wall of the groove moves diagonally to the center. This way we get two signals in one groove. The movement of one wall does is not picked up by the opposite sensor coil.

But this means that the mono bass will cause both walls to move diagonally up (and down) in unison. This will cause the stylus to bounce out of the groove, unless something is done. (I.e. in a mono signal, both walls diagonally up and down in phase.)

The solution is that the respective audio channels are put in reverse polarity before the disk is cut. This way the mono bass causes the stylus to move from side to side rather than up and down. Consider: Left channel groove goes diagonally up to the center and the right channel groove moves down away from the center. The result is side to side modulation of the stylus. Then with stuff has to be corrected in the wiring.

At least that is my understanding. Dave Mallet knows all this stuff and can clarify.

Added by edit: I should not have made this sound like just a bass thing. I believe the answer is that all LPs are cut with lateral cutting as opposed to up and down (hill and dale). In an Edison cylinder for example, the recording stylus pushes into the groove. But in LPs (and I think 78's) the recording and play back stylus moves left and right.

Therefore all mono signals in an LP causes left and right modulation.

So I think I was correct to say that the two coils of a stereo pick up must be wired in reverse polarity to respond to a mono recording correctly.

WMcD

Edited by WMcD
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Romy the cat doesn't tell us enough. If he has two subs, and he is either powering them mono or stereo, it is possible he is doubling the actual input when he has the stereo setup engaged. Or worded a different way, halving the input of the two subs when in mono. Yes, that would make a difference! As far as flipping from left to right, I don't know how a person could be objective because that would take some time. I have trouble with simple A/B switching comparisons, let alone an entire rewire then re-listen. 

 

The guy believes what he is saying, but science and facts don't lie.

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Seriously... I'll try this myself.  Have someone blindfold you and turn around enough times so you don't know which way you are facing.  With only the sub running can you tell where it is sitting?  I'm betting that you can.  Even crossed at 60.    Hmmm... kids are doing homework in the family room right now.  Maybe this weekend...

 

Doesn't really matter anyway though.  Whatever sounds better.  With the peaks and nulls in my room I find it hard to believe that I could be happy with a single sub.  I know that I never could get it right and sold it.  My list of future projects  still has two horn loaded subs on there... maybe someday.  sigh!

 

If I'm listening to a bass playing on the left then the lowest notes should be coming from the left as well.  I'm just talking about music and 2 channel.   

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If we are just talking about music and two channel, the only reasons you even need a sub are either your mains are not full range, or you listen to pipe organ recordings.  For example, an electric bass guitar bottoms out at around 40hz or so.  I can't remember the exact frequency, but I have a chart saved on my old computer which barely works lol.

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I browsed the article quickly and assumed these tests were done in a controlled environment.

 

Most of our rooms are not great places to run these type of tests.

 

Any respectable subwoofer will cause things to rattle and shake, meaning it may not be the sub itself you hear but objects or even the room itself causing distortion making it easier to identify where the low frequencies are coming from.

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If we are just talking about music and two channel, the only reasons you even need a sub are either your mains are not full range, or you listen to pipe organ recordings.  For example, an electric bass guitar bottoms out at around 40hz or so.  I can't remember the exact frequency, but I have a chart saved on my old computer which barely works lol.

About 41 for a 4 string and 31 for a 5. I thought it was 29 but maybe not. Most of what you hear that seems to be bass are resonances and harmonics in the 100 something hz range though. Most people would be surprised to find out that popular bass guitar cabs don't even reproduce the lowest fundamentals from a bass guitar all that well. They usually don't need to. For example the famous Ampeg SVT-810E, it is 3 db down at 58 hz.

Edited by MetropolisLakeOutfitters
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I browsed the article quickly and assumed these tests were done in a controlled environment.

 

Most of our rooms are not great places to run these type of tests.

You talking about the Harman article? Their conclusions are just how it is at this point, all the top room designers are following these principles. Nobody's just putting one sub in one position in a room and calling it good on nicer builds. REW has a room simulator, you can punch in your room dimensions, seating position, sub position(s), and see the effect that multiple subs can have in smoothing out response between different seating positions. Read up on Floyd E. Toole's latest rants on the subject.

 

Any respectable subwoofer will cause things to rattle and shake, meaning it may not be the sub itself you hear but objects or even the room itself causing distortion making it easier to identify where the low frequencies are coming from.

I don't see how objects rattling in a room would lead to subs being able to be localized. If anything, in a normal room with a small number of normal subs up front, it is your back wall that is the loudest and would vibrate stuff the most. How would objects rattling behind you lead to you being able to localize the subs that are sitting up front? I've got this going on at my place, have a rear sconce light that rattles, and if they really get going, part of my rack in the back rattles.

Edited by MetropolisLakeOutfitters
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