Coupling Bass Bins

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Chuck The DJ

Chuck The DJ

I know people.
Sep 28, 2006
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Sebastopol, California
www.chuckthedj.com
I DJd a club on Friday night, and they were using some 18" bass bins and had them on the stage one left one right...

Now there was room in front of the stage to put these side by side in front of the DJ... I think they were Peavey Internationals, but old and powered by a CS800 amp..

So before I mouth off to the guy and tell them this or that, please tell me that by sitting them side by side "coupling" they gain 6b which is almost doubling the output....

I am not sure of my facts, so please tell me....
 
Chuck The DJ said:
I DJd a club on Friday night, and they were using some 18" bass bins and had them on the stage one left one right...

Now there was room in front of the stage to put these side by side in front of the DJ... I think they were Peavey Internationals, but old and powered by a CS800 amp..

So before I mouth off to the guy and tell them this or that, please tell me that by sitting them side by side "coupling" they gain 6b which is almost doubling the output....

I am not sure of my facts, so please tell me....
Click to expand...

I don't know about the gain. If you have enough Bass Power to cover the area then nothing else matters. However to answer your direct question as to the comparison of what would the DB level be coupled vs separate in that environment, I cannot speculate.
When I am using my Tri-Amped system, I HAVE to put two (Or one) on each side because I need the top of those cabinet(s) to support my Midrange and Tweeter Boxes stacked. 6 db more or less won't affect me as I can always adjust my settings to suit and get what I want.
 
I'm sure that someone will chime in with the math that I can't remember but I think it's +3db for coupling, another +3db for sidewall loading and yet another +3db for rear wall loading.

The penalty for not coupling is frequency cancellation. I think the rule is either have more than 50 foot separation or be coupled. Anything in between means cancellation at that frequency.

There are other cancellation problems that you need to watch out for also. Raising the subs off the floor creates a -3db loss and also creates aother cancellation. A raised stage is the most common issue here.

There is also the cancellation created by a rear wall if you are not corner loading.

All these cancellation problems and possibly lost gains, why not corner load & couple whenever possible?

Scott
 
scharris_99 said:
I'm sure that someone will chime in with the math that I can't remember but I think it's +3db for coupling, another +3db for sidewall loading and yet another +3db for rear wall loading.

The penalty for not coupling is frequency cancellation. I think the rule is either have more than 50 foot separation or be coupled. Anything in between means cancellation at that frequency.

There are other cancellation problems that you need to watch out for also. Raising the subs off the floor creates a -3db loss and also creates aother cancellation. A raised stage is the most common issue here.

There is also the cancellation created by a rear wall if you are not corner loading.

All these cancellation problems and possibly lost gains, why not corner load & couple whenever possible?

Scott
Click to expand...

Scott, I believe that's correct from what I've been reading over at Bill Fitz's forum. Is it 3db or 6db that is doubling the sound herd?
 
success was never companied with short cuts nor

will it allow for practical in many cases. (extra work many times provides the ultimate results. Not gaining these results short changes the effort for all.):sqcool:
Chuck The DJ said:
sometimes what is the "best" way may not be the most "practical" way.
Click to expand...
 
It can depend on the design of the bass bins as well. But for front radiating subs, one may experience wave cancellation by separating them stage left and right. :)
 
Is the room BIG enough to require the extra DB's?
if not, maybe it's better esthetically to keep em where they are?
(unless the frequency cancellation is an issue)
 
Brian said:
Scott, I believe that's correct from what I've been reading over at Bill Fitz's forum. Is it 3db or 6db that is doubling the sound herd?
Click to expand...

3db = doubling of power
10db = doubling the subjective volume (sounds 2X as loud)
 
I would also like to hear more about this. I also set my top speaker on my subs, also I use 8 conductor wire, I run 1 cable per side and jump up to the top speakers. If I need more SPL's I use more speakers and power. I also would have a hard time hearing requests if I put all the subs in front if my table. (8-18" = very loud).
 
Prodjay, your wish is my...

ProSoundWeb is an excellent source of information


Reference to the first article was originally posted by Houston some time ago and probably merits a revisit given the topics covered here. The others seem to be equally on topic and hopefully some of you will find them of interest.




The “Power Alley” - Discussion & Solutions to the Troubling Interactio of Subwoofer Stacks
http://www.prosoundweb.com/article/in_search_of_the_power_alley/


Proper Loudspeaker Placement: How to Avoid Lobes & Nulls
http://www.prosoundweb.com/article/lobes_and_nulls/


Subwoofer Arrays: Discussion & Analysis of a Variety of Bass Coverage Patterns
http://www.prosoundweb.com/article/subwoofer_arrays_a_look_at_bass_coverage_patterns/






Lastly, please find an Applet to simulate the interference pattern of two point sources. You can vary separation, frequency and scale among other things. While I can't vouch for the accuracy, it does seem to work as I'd expect these types of interaction to occur. The applet requires a Java plugin to be installed on your browser.


http://www.falstad.com/interference/


Have fun.
 
Generally coupling subs yields (in theory) 3db boost in spl, then another 3db everytime you double the system. So in theory, doubling from 1 sub to 2 subs would yield a 3db increase in spl, doubling from 2 to 4 subs would increase the spl another 3db, stacking the subs against a rear wall would increase the spl another 6db due to the boundary effect where with low frequencies beloew around 250hz being omni-directional, low frequencies travelling backwards can't go anywhere because of the rear wall, so they bounce back and radiate forward meaning that double the energy is coming forward. Stacking the subs in the corner yields another 6db increase, once again due to the boundary effect.
 
Thanks Balanced Line, that made for some good reading. I still do not know what I will try to do, as most of my shows will not allow me to stack all the subs in the middle and I never have the chance to to put them next to a wall. maybe I can come up with some kind of portable wall to bring with me. I also don't know what I will put the upper speakers on, as I would use the subs in the past.
 
A portable wall in my opinion will cause more problems than it'll solve because it'll probbaly just vibrate and you might be able to hear over the music. Solid walla do vibrate too, but you can't really hear them because they're generally made of thick slabs of breezeblock and brick. Its normally the joists and frames that vibrate loudly in a building I think.
 
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