[JohnR]

In his previous post: http://www.audiocircle.com/index.php?topic=78649.msg931756#msg931756

[Quiet Earth]

The Geddes multi-sub approach runs the mains full-range.  So one way to do it is to "tee" the preamp outputs and go straight into the L and R power amp inputs with one side of the tee on each of the preamp output channels.  The other side of the tee on each of the L and R preamp outputs goes into the Behringer, which sums them to mono, then provides individually-adjustable low-pass filters (and parametric EQ if desired) for up to six subwoofer channels.

So you end up with low-pass filters on the subs, but no high-pass on the mains, thus avoiding going through the Behringer on the mains side.  Getting a purist amplification path for the subs is not strictly necessary, so this is a clean solution.

Thank you Andy, Doug, and everyone else. I get it. (I think.)

Unfortunately this only makes me wonder even more. (Oh no, not again..... somebody stop that guy!)  If the super low bass energy is really so crucial to the existence of the music,,,  and if that part of the sound is so important that you would go to such efforts to measure and obtain perfect in room response,,,   how could you not hear a Behringer 2496 or a plate amplifier leave its footprint in the sound? Never mind that your mains are running full range, I understand that part. You are still mixing in the sound of a cheap digital xover or a nasty plate amp (or whatever) to get the sub to woof. You are still adding cables and stuff to the system and changing it from simple to not so simple.

You say you can get away with it because it's only super low bass, but yet it is so very important that you can hear the improvement . . . . . am I the only one that sees a flaw in this logic?


 


I will stop making comments on this subject for now because I obviously have a lot of homework to do. I need to fart around with some of this stuff to get a better understanding of what you guys are achieving. I actually believe you guys and your enthusiasm and I enjoy the discussion. That's what we're here for right?

I'm just trying to wrap my head around it for now. Maybe when I hear it I'll just go .
 

[Quiet Earth]

I think that you might misunderstand that I don't really have a "vested" interest in using multiple subs.  Subs are an insignificant part of my business.  Thats why I don't publish much on it.

My apologies Dr. Geddes,  I was not trying to single you out.  I was hoping that Duke or Kevin might be up for it,  Or anyone that might want to use multiple subs to sell other products.

My curiosity is genuine. 

[gedlee]

Gedlee,

Thanks for popping up here. You may have covered this elsewhere, but I am curious why your designs run the main drivers without a filter to take some of the low end load off of them?

Two reasons - first, there really is no downside to doing this in my bigger speakers as they can easily handle the LFs with no problem.  For home audio they are way over capacity, but I don't use them for there power handling or excursion capability, which they have an excess of, but I use them because they are very directional and they are well behaved at the high frequency extremes that my designs go to.

The second reason is that they act as aother sources at LFs and the more sources that there are the smoother the "expected" response will be.

There could be situations where one might want to use a gradual HP on them, but nothing steep, nothing greater than 6 dB/Oct I wouldn't want all that phase shift.  But that gets problematic when one uses a receiver since none of them that I know of do that.  The standard Dolby style surround processors filter way too high and too sharp.

So it might be as much a practical thing as it is anything else.

The bottom line is what does the room response look like when all is said and done.  If that works then it works for me.

[srb]

You say you can get away with it because it's only super low bass, but yet it is so very important that you can hear the improvement . . . . . am I the only one that sees a flaw in this logic?

The low bass is an important component, but it's probably more important that all of the bass frequencies are reproduced in a linear fashion and equally distributed throughout the listening area with no peaks or valleys.
 
Once all the bass frequencies are produced evenly, I think it's more the fact that minor signal distortions and phase errors just aren't as noticable to the human ear in the lower bass region as they are in the midbass, midrange and high frequencies.
 
Could a system be improved with higher quality and more expensive subwoofers and crossovers?  Most likely, but probably not in direct proportion to the additional money spent.
 
Steve

[gedlee]

If the super low bass energy is really so crucial to the existence of the music,,,  and if that part of the sound is so important that you would go to such efforts to measure and obtain perfect in room response,,,   how could you not hear a Behringer 2496 or a plate amplifier leave its footprint in the sound?
 

According to Toole the LF sound accounts for about 20% of the perceived sound quality.  That seems right to me as well.  Its not critical but it is still very important.

But the bottom line here to me is the assumption that "electronics" is all that audible in the first place.  From all that I know that is simply not the case.  So take a "debatable" audibility on a 20% part of the problem and I just don't see why using a Behringer is such an issue.

Plate amps - I gave up on those because they were terrible in reliability.  I mean put any piece of electronics into a box which is constantly pounded by a woofer and you can expect it to fail prematurely.  I only use rack amps anymore - cheaper, cooler and more reliable.  Whats not to like.

The point about an amp being less critical when its used only over a small bandwidth is also true.

[poseidonsvoice]

The low bass is an important component, but it's probably more important that all of the bass frequencies are reproduced in a linear fashion and equally distributed throughout the listening area with no peaks or valleys.
 
Once all the bass frequencies are produced evenly, I think it's more the fact that minor signal distortions and phase errors just aren't as noticable to the human ear in the lower bass region as they are in the midbass, midrange and high frequencies.
 
...
 
Steve

Bingo  . Well said. This has been proved, time and time, and time again.

FWIW, I've also used a discrete crossover in the past, with nary an opamp, etc...for the bass frequencies. Result? More of a headache than anything else. You need to have flexibility and options, which the Behringer allows, as you cannot predict the LF response in a room reliably without measurements - at least for me.

Anand.

[gedlee]

Bingo  . Well said. This has been proved, time and time, and time again.

Well maybe one too many "time agains"s - lets not forget that the use of multiple subs is generally a pretty new concept.

FWIW, I've also used a discrete crossover in the past, with nary an opamp, etc...for the bass frequencies. Result? More of a headache than anything else. You need to have flexibility and options, which the Behringer allows, as you cannot predict the LF response in a room reliably without measurements - at least for me.

Anand.

Also well said.  Without measurements its just a guess and every room is different so guessing just doesn't work.  And minimizing headaches always works for me.

[jtwrace]

Well maybe one too many "time agains"s - lets not forget that the use of multiple subs is generally a pretty new concept.

Maybe not!  I make up for one of the "time again's".   

[tesseract]

Thank you Andy, Doug, and everyone else. I get it. (I think.)

Unfortunately this only makes me wonder even more. (Oh no, not again..... somebody stop that guy!)  If the super low bass energy is really so crucial to the existence of the music,,,  and if that part of the sound is so important that you would go to such efforts to measure and obtain perfect in room response,,,   how could you not hear a Behringer 2496 or a plate amplifier leave its footprint in the sound? Never mind that your mains are running full range, I understand that part. You are still mixing in the sound of a cheap digital xover or a nasty plate amp (or whatever) to get the sub to woof. You are still adding cables and stuff to the system and changing it from simple to not so simple.

You say you can get away with it because it's only super low bass, but yet it is so very important that you can hear the improvement . . . . . am I the only one that sees a flaw in this logic?

This was a concern for me as well, I do not want to run my mains signal through a black box or split it off with a Y-adapter if I don't have to.

I have an integrated amp with pre outs, I simply run these to a Dayton SA1000 hooked to dual 18" sealed subs. I hope to add another SA1000 and dual 18's soon, not for more bass, but to smooth the room further. Point is, my bass system is separate from my mains. While this is not completely necessary to realize the gains of multi subs, it does address this concern of yours and mine. But even if you do have to split the signal via cables, the benefits greatly outweigh the "costs".

The Dayton amp does have a low level high pass filter for my mains, I chose not to use it. My current mains are capable and my next ones will be more so.

I get the feeling that you picture subs as adding bombast and discord. Done properly, multi subs are subtle and don't call attention to themselves, they ADD to the experience and compliment your mains. They simply play nicer with the room.

I have had many different systems, floorstanders, stand mount, and have settled on stand mount with multi subs. Soon I will being trying out constant directivity mains in a further effort to play nice with my room.

I really like your room, BTW, Quiet Earth.

[jtwrace]

Soon I will being trying out constant directivity mains in a further effort to play nice with my room.

Which model?

[tesseract]

My budget allows for the Chase Home Theater PRO or SHO-10's, or Pi Speakers 3 or 4 kit.

I also have the N2X audition pair on the way, so nothing is set in stone yet, I could find myself with N3's. I will give the waveguides a try.

[service_guy]

I do...............................
For the most part, most of us can not afford fullrange speakers that are TRUE fullrange, so we look to other options to fill in the bottom, say from 45hz and down.
I was in the audio business (home and competion car audio) a number of years ago, and we sold some pretty good stuff, so I am pretty good at setting up a room and getting a sub to blend in (disappear) just like the main speakers should.
My solution was to build my own.
Two 3.9 cuft boixes tuned to 21hz with one Rockford Fosgate RFD 1212 in each box.
I know, turn your nose up at the Fosgates, but these are not the cheap big box store subs.
12 inch, cast basket, three inch voice coil, 102oz magnet, fs of 26hz, real stiff treated paper cone, 18mm of xmax, 500w rms, dual voice coils wired in series for 8 ohms and then parallel for 4 ohms to 500 watt sub plate amp, with the crossover at 45hz
In room extension to -3db 19hz at any level you happen to want.................
Ie: want to try some organ music to settle your intestines, go for it
Don't get me wrong, these are not boomy, just the opposite.
Just solid, tight and tuneful bass.
System:
Linn Axis
Cambridge Audio CD6
B&K Pro 10MC pre-amp
PS Audio HCA 2 power amp
Paradigm Studio 60v2
Tara Labs RSC Reference Gen2 cables and Transparent Audio power cords
Just my 2 cents