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Running Subs in Parallel

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Doley50

Sep 4, 2005
166
9
#1
I was reading somewhere how it was better to run your subs in parallel, because it would reduce the risk of the subs being out of phase.
While this makes sense to me I wish I could remember where I read it.
We have been running a pair of Yorkville x720 subs with QSC K12's using the output of each K12 to feed into each sub, basically we are running both speakers in stereo.
I would like to try running the subs in parallel, in hopes to get a more defined, and tight bass sound, but before I do this, are there any draw backs, precautions or anything else I should be aware of?
If I find were I got that information from ill post it.
Thanks
John
 
#2
Are you running the QSC's in stereo or dual mono (preferred)?

Edit: there may be other issues but I need to check the specs on both the mains & subs. Frankly, the best investment you can make would be an inexpensive rackmount crossover. Pass-thru's and HPFs / LPFs are great but do have some limitations.

Riis
 
#3
We are running the QSC's in stereo, dual mono? I have to look into that.
I have through about purchasing a crossover, but both the monitors and sub's (self powered) have built in crossovers, how will an external crossover behave with the internal crossovers ? ( hope that question makes sense ) also, "if" the subs are out of phase, will a crossover cure that? ( I don't see how? )
Just learning and asking questions based on what "I think I know. "
Thanks
 
#4
Doley50 said:
We have been running a pair of Yorkville x720 subs with QSC K12's using the output of each K12 to feed into each sub,
Click to expand...

Sounds like you have your sub's split? One under each main? Positioning subs that way will cause cancelation in may area's, and a power ally up the middle of the audience. Better to have the subs next to each other.

Invalid Link Removed
 
#7
mtsens1 said:
Sounds like you have your sub's split? One under each main? Positioning subs that way will cause cancelation in may area's, and a power ally up the middle of the audience. Better to have the subs next to each other.

Invalid Link Removed
Click to expand...

If his subs are out of phase it would be more noticeable if they were next to each other. While power alley problems do exist I think it isn't quite as critical for bands playing in small bars.
 
#8
I heard about placing the sub's next to each, however we play mostly small bars, and we use poles in the subs to mount the K12's on top of, maybe I could just not turn one of them on and see if that makes any difference. Do we really need two 720 watt subs woofers in a small club? I am going to try in tonight.
 
#9
I think what your looking for is an external crossover. I just picked up an open box dbx driverack px off ebay and once I threw the manual away and went to the forum and read up on how to use it (hint, don't use the wizards, except for the feedback suppression.)

Just checked, your tops and subs are both listed in the setup wizard, in that case it comes pre set-up for your miss-matched speakers.

The difference... well is phenomenal. I took my top and sub outside and did a flat auto eq and balance. That is the preset I load anywhere I go. I don't run it again at the venue though. I still do that by ear, using the 5 band PEQ w/variable q to tune the room to music. Too hard to use an RTA in small places, empty before, packed after...

I do run the AFS set to medium sensitivity with 6 fixed and 6 live filters. No feedback, even in my practice space!!! Most importantly playing bass and running sound is hard, but using this and setting my system up for proper unity gain from mic to speaker!...
I never dive for faders anymore. I recorded a bunch of songs last night, and they sound exactly like they did playing them last night. I had to do no eq or compression, balance...

Single greatest item I've purchased for my PA.

Here's the one I bought. Pro Audio Star Ebay Driverack Got it in 2 days for $200.
 
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#10
If you need another, I have one listed in the GFS... I'm moving over to the BSS MiniDrive. My PX is new, in the box... I read the manual and put it away.

Ideal theorhetical placement for subs is center stage which often means ahead the mains and that means you may need a bit of delay on them. Another plus for the drive rack.


I've mixed with subs centered and split and grouped to one side. I've heard split subs sound nasty but I've also heard them sound great. More often than not, it was great... The big hole in the middle i believe has a lot to do with the shape and content of the room and the size of the hole, how far out from the stage the hole projects I believe is also a function of volume. It may be that in small and medium sized clubs that are deeper than they are wide, split subs work just fine. I think this topic gets a lot of play from the theorists and less from the practitioners... No question that it happens, the questions for me are

how does the room play into it?
how does that change when there is a crowded dance floor?
At what volume level does it really begin to matter?

I think it is not as cut and dried a topic as the papers would have us believe.

I'm also moving to AUX fed subs. If ya want to read religious wars, there is a topic to google... I think it gets me closer to a big, ballsy mix at lower volumes while reducing low end rumble. I can see in major systems where there are flown subs and subs on the ground the phase could be an issue. Pretty sure that will never be an issue for me :D
 
#11
Heres your classic power alley article, best I've found

Invalid Link Removed

Now... the effects in a medium sized club thats packed with subs about 20' apart? Not sure, maybe more theoretical issue than an observed one... I'm not sure.
 
#12
Actively directing specific channels to the left or right speakers is stereo. You are trying to locate specific instruments in space. If all the pans on your board are centered and sending all channels equally to left and right speakers then you are effectively running dual mono.
With your subs acting as speaker stands then you will have phase issues as you move from one side to the other. Example: If your are standing 5 ft from sub L and 15 ft from sub R you should hear some cancellation in the sub area. (at about 80hz if you want to nail it down). Move so you are 10 ft from each sub and instead of cancelling, they reinforce each other (here's your power alley up the center). All of this is affected by the shape and size of the room (reflections), how many people are there (sound absorbers), volume, etc. Subs together in the center will not only give you the benefit of phase coherency, assuming all cables are good and you're feeding the same signal into both, but will give you a small energy boost. Parking them on the floor in a corner will give you an extra boost as well. Because the walls and floors are within a small fraction of a wavelength, the reflections are in phase with the original signal. Free bass boost.

The downside of the sub cluster is that you now lose some bass on the outside edges. This is not all bad. Put the volume on the dance floor where people want to be shaking and a little less out on the fringes so that the waitress' can hear the orders more easily. Always keep the Bar happy.
I am, personally, a prophet for aux fed subs. Yes it is close to a religious war and the results are easily abused by those in power which can give the process a bad name. Much like religion. OTOH they work for me.
 

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