Silly QSC 181 Question

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Albatross

DJ Extraordinaire
Sep 7, 2016
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#1
Before my Evox system, I used to run a QSC KW-181 all the time. And my signal route was always two XLRs into the right and left, and then chaining the through output up to my tops. So, I never had to worry about the question I'm getting ready to ask...

If you run a single side into the 181, instead of right and left together... are you still getting the full power of the sub?

I can't really imagine why they would have the amp truly split up like that. But for some reason I feel like I read somewhere that you needed to run both sides on that particular unit. Does anybody know for sure?

I can if I need to, of course, but if I can avoid the extra wiring, I will.
 
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djtaso

DJ Extraordinaire
Apr 4, 2017
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#2
Before my Evox system, I used to run a QSC KW-181 all the time. And my signal route was always two XLRs into the right and left, and then chaining the through output up to my tops. So, I never had to worry about the question I'm getting ready to ask...

If you run a single side into the 181, instead of right and left together... are you still getting the full power of the sub?

I can't really imagine why they would have the amp truly split up like that. But for some reason I feel like I read somewhere that you needed to run both sides on that particular unit. Does anybody know for sure?

I can if I need to, of course, but if I can avoid the extra wiring, I will.
You mean just plugging in the left or right? I mean that's how I always did it... but I had two subs, so the left and right signals were all going somewhere. If you're not running two subs and only using one side, I can't help but think that the sound of the other signal would be missing, and at points feel like somethings missing.
 
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Albatross

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Sep 7, 2016
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#3
You mean just plugging in the left or right? I mean that's how I always did it... but I had two subs, so the left and right signals were all going somewhere. If you're not running two subs and only using one side, I can't help but think that the sound of the other signal would be missing, and at points feel like somethings missing.
I was running a single sub at the time, so both left and right were going into a single box.

But on the 181, if you're not using both the left and right inputs, you're still getting the full sub output, correct?
 
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djtaso

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Apr 4, 2017
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#4
I was running a single sub at the time, so both left and right were going into a single box.

But on the 181, if you're not using both the left and right inputs, you're still getting the full sub output, correct?
I can't imagine it's output being affected by both inputs being utilized.
 

Proformance

DJ Extraordinaire
Nov 6, 2006
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#5
I was running a single sub at the time, so both left and right were going into a single box.

But on the 181, if you're not using both the left and right inputs, you're still getting the full sub output, correct?
Well, not really.

The pass thru connection remains unchanged - however, the branch feed to the woofer is designed to be stereo when only one input is used (two subs), and summed mono when both inputs are fed. If you are using a single sub with a stereo signal you should be running it in summed mono which means sending both channels to the sub.

If you are already running in mono - then you need only connect one of the inputs, and can run a separate line to one or both full range/tops.

Alternatively with two subs, you can run stereo tops and summed mono at the subs by running a stereo pair to the first sub, feeding the pair thru to the next sub, then feed thru to your left and right full range/tops.
 
Last edited:

rickryan.com

DJ Extraordinaire
Dec 9, 2009
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Hendersonville, TN
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#8
Before my Evox system, I used to run a QSC KW-181 all the time. And my signal route was always two XLRs into the right and left, and then chaining the through output up to my tops. So, I never had to worry about the question I'm getting ready to ask...

If you run a single side into the 181, instead of right and left together... are you still getting the full power of the sub?

I can't really imagine why they would have the amp truly split up like that. But for some reason I feel like I read somewhere that you needed to run both sides on that particular unit. Does anybody know for sure?

I can if I need to, of course, but if I can avoid the extra wiring, I will.
I do this same thing with my Altos. I've tried running both l/r in but normally only run one line into each sub. The output appears to be the same. I can't imagine that the QSC works any differently. Hope this helps. BTW, great sub.
 
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Handinon

DJ Extraordinaire
Oct 1, 2014
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#11
If you run a single side into the 181, instead of right and left together... are you still getting the full power of the sub?
Yes and No.

As previously stated, if you are running a mono system, no difference.

If you run stereo, there can be a difference depending on how the song was recorded and engineered. It was common for music that was recorded back when LP's were used for playback to use "summed bass". Both channels below a certain frequency had the same information. Skipping the technical, it was better for the cutting lathes as well as your turntables cartridge to do it that way. Therefore, no problem using a single sub.

Enter the CD. Music first created, recorded, and engineered after the CD came into wide spread use (say 1985) does not have this limitation. However, since bass is non-directional, a recording of live singers and instruments can have the same level of bass in each channel, but there can be significant phase differences depending upon microphone placement. Good recording engineers check for this by doing mono mix downs, but not always. We have all heard recordings like this. If your system has a mono/stereo switch, you've probably heard how some recordings sound much different when switching back and forth - and I'm not talking about just the stereo sound field.

Lastly, EDM - computer generated music. There is no technical reason whatsoever that the right channel and left channel mimic each other at any frequency. Lucky for us most recording engineers are sane people, and also know many of the big clubs run mono - but there can still be big differences in the bass between both channels, therefore running a single sub off just one stereo channel now becomes questionable.
 
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steve149

Urbane Legend
Sep 26, 2011
20,221
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Prospect, CT
#12
Yea .. as said, doesn't affect power, but DOES affect content. While most current crap has similar bass content right and left, there are cuts that you would lose some bass content if you didn't feed both left and right to the sub.
 

Albatross

DJ Extraordinaire
Sep 7, 2016
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#16
Imo, you should run stereo unless you don't have a centered 'zone' / dance floor to cater to.
I can if it will make a difference positively. I've never noticed mono being a problem. But the way I'm actually planning to route signal for this gig is:

DDJ SZ2 & Microphone > Yamaha MG 10 > Main Output to my tops, Aux to the subs.

I've had experience in the past where if the mic is in the sub, you can get a ton of feedback. So I'd rather send none or very little of the mic to my subs. By using the Aux out for the subs, I can have a lot better control of where the sound is going.
 
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ittigger

Hundred Acre Industry Icon
Feb 1, 2011
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Western Maryland
#17
I honestly don't think anyone would notice mono being a problem - especially in a world where most current music, you can't tell if it's stereo or not. Go back a few decades and you can easily hear it (as late as the 90's and as early as the 60's).

You can send mono straight from the SZ2 - and then using one output, daisy chain all speakers from there. For splitting the Mic as you're talking about, you'd still have to use some kind of external controls.
 

scgstuff

DJ Extraordinaire
Jun 30, 2017
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#18
I've had experience in the past where if the mic is in the sub, you can get a ton of feedback. So I'd rather send none or very little of the mic to my subs. By using the Aux out for the subs, I can have a lot better control of where the sound is going.
If you take the low end off the mic channel, wouldn't you eliminate some potential for feedback from subs? Or is your mic into the DDJ instead of a separate channel on the MG10?
 

scgstuff

DJ Extraordinaire
Jun 30, 2017
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#20
I think he's running the SZ2 and Mic separately into the MG10. From what I'm reading, he'll then attempt to send Mic/music to the tops and only music to the subs.
That's what I was reading also. Was just wondering if taking the low end off the mic channel would essentially have the same results. And, if pole mounting the tops over the subs, only 1 long run from MG10 to each sub and then the hi-pass filtered out up to the top (or passthrough). Not sure it would be the same result which is why I was asking.

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