[G Georgopoulos]

Here am again,wanting your opinions on this,which do you prefer and why (how it works),tell us if there is a difference there,I like the bass of speakers because i think there is some directivity there that stereo imaging reproduces,am i wrong?

kind regards to all.

[JoshK]

Since this is the lab, I say the discussion shouldn't shy away from the science and the facts.   Bass in a small room* has been well studied but largely ignored by the audiophile community (see Toole, Geddes, Blauert, etc).   The whole problem involves the modal region between the first mode and the schroeder frequency.   The problem really lies in the fact that the Schroeder frequency (fs) is typically well above the point at which you crossover to subs (say ~200hz +/- 50hz).   

I think for small rooms, multiple subs and well thought placement is undisputably the king, and there is mucho evidence to prove this.  However, typically you are going to cross these subs around 80hz to avoid localizability.  This leaves the region from 80hz to fs the main problem to tackle with room acoustics.   It's my humble opinion that it's this area, not the true bass below 80hz that leads many audiophiles to believe that main speaker bass is better than subs.   Because integration is a bit trickier when there are modes and valleys in the area you are trying to cross, and the human ear tends to associated higher harmonics with the fundamental in bass frequencies. Fortunately traps can typically help here.

Take for example, you are using two subs crossed at 80hz with a LR 24db/oct slope.  But you have a major room mode at 160hz that spikes 20db.  Suddenly your subs become localizable even though they are crossed at 80hz, but not because of the bass below 80hz but the mode an octave above. 

Further, I think if you are not taking real measurements of your room and are coming to conclusions based on listening only you are highly misguided.   I wouldn't trust myself let alone some "authority" on the internet espousing their experience without the measurements to back it up. [you here is general you, not you in particular GG, just an FYI, this isn't a pot shot against anyone in particular]

* What I mean by "small room" is in the definition used in acoustics, meaning a living room rather than a large concert hall.

edit: there are lots of good discussions about the science of room acoustics freely available on the internet in addition to the books by Toole, Geddes, etc.   http://www.linkwitzlab.com/rooms.htm  is one.

[jtwrace]

Josh I agree that multiple subs are absolutely the best.  There is no doubt in my mind whatsoever.  I'd also add that they will work just as well for large rooms as there are issues there too and multiple subs solve those issues the same way.  The only difference is that you might need one or two high powered large subs but the result is stunning and nobody realizes what they're missing until they hear it done properly. Further, room treatments over any dsp is the only way to go IME. 
 
EDIT:  I use/setup multiple subs ala Geddes..

[JoshK]

I'm sorry, I should clarify.   What I mean by "small room" is in the definition used in acoustics, meaning a living room rather than a large concert hall. 

[JoshK]

Let me just add that I have a hypothesis, but no real proof, that using mains (preferably sealed enclosure) with a -3db in the 40-70hz area is only going to help in the spatial averaging of the system as a whole and likely to help above the 80hz range.   That is the approach I am taking in my system, also used by Geddes the last I checked. 

[Rusty Jefferson]

..,I like the bass of speakers because i think there is some directivity there that stereo imaging reproduces,am i wrong?

I wouldn't say wrong, but not my experience. The position (location) of a musician (low frequency generating instument) in the soundstage is uneffected.

Are you using an active crossover and experimenting with the crossover point of the full range woofers/subs?  I could see losing image coherence if you raised the sub crossover point too high, but that would introduce other issues as well.

[G Georgopoulos]

Since this is the lab, I say the discussion shouldn't shy away from the science and the facts.   Bass in a small room* has been well studied but largely ignored by the audiophile community (see Toole, Geddes, Blauert, etc).   The whole problem involves the modal region between the first mode and the schroeder frequency.   The problem really lies in the fact that the Schroeder frequency (fs) is typically well above the point at which you crossover to subs (say ~200hz +/- 50hz).   

I think for small rooms, multiple subs and well thought placement is undisputably the king, and there is mucho evidence to prove this.  However, typically you are going to cross these subs around 80hz to avoid localizability.  This leaves the region from 80hz to fs the main problem to tackle with room acoustics.   It's my humble opinion that it's this area, not the true bass below 80hz that leads many audiophiles to believe that main speaker bass is better than subs.   Because integration is a bit trickier when there are modes and valleys in the area you are trying to cross, and the human ear tends to associated higher harmonics with the fundamental in bass frequencies. Fortunately traps can typically help here.

Take for example, you are using two subs crossed at 80hz with a LR 24db/oct slope.  But you have a major room mode at 160hz that spikes 20db.  Suddenly your subs become localizable even though they are crossed at 80hz, but not because of the bass below 80hz but the mode an octave above. 

Further, I think if you are not taking real measurements of your room and are coming to conclusions based on listening only you are highly misguided.   I wouldn't trust myself let alone some "authority" on the internet espousing their experience without the measurements to back it up. [you here is general you, not you in particular GG, just an FYI, this isn't a pot shot against anyone in particular]

* What I mean by "small room" is in the definition used in acoustics, meaning a living room rather than a large concert hall.

edit: there are lots of good discussions about the science of room acoustics freely available on the internet in addition to the books by Toole, Geddes, etc.   http://www.linkwitzlab.com/rooms.htm  is one.

 

[werd]

This has been my experience runnng a sub in my system. Assuming its properly set up. I was using a Bryston 14Bsst2 into a variety of different full range speakers. Also a PARADIGM servo 15 sub for low. The problem is the Bryston 14B was in a different quality class then  the amp in the sub had..  There was no tonal match. The sub amp and volume control were boh high gain. I was using low gain or passive preamps. It was a sloppy fit. The quality of amplification in subs tend to be no where near the kind of amplification peope mate them with. So you have this excellent amp driving mains with grip and finesse into the woofers and then you got this high gain class D amp flopping around in the sub. Is there any wonder why its hard to get these things to match and sound good?