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Author Topic: Aux Fed Subs  (Read 19230 times)

Gary Weller

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Re: Aux Fed Subs
« Reply #30 on: April 13, 2011, 01:26:12 PM »

My question was more about the situation of a room where there may be a "spike" in response at let's say 60Hz and my DSP is in my amp rack and not acessable from FOH . I agree that PEQ is better but for quick & dirty bar gigs you mostly don't have the luxury of an extensive soundcheck, I thought maybe an additional GEQ might be ok.
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Bennett Prescott

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Re: Aux Fed Subs
« Reply #31 on: April 13, 2011, 01:50:13 PM »

Gary,

There's no reason not to, but remember that if the 60Hz spike is because of a room mode then it won't exist everywhere. Cutting where it is too much will also cut where it was OK, and cut more where there was too little. There's no 3D GEQ.
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Tim McCulloch

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Re: Aux Fed Subs
« Reply #32 on: April 13, 2011, 02:49:11 PM »

Gary,

There's no reason not to, but remember that if the 60Hz spike is because of a room mode then it won't exist everywhere. Cutting where it is too much will also cut where it was OK, and cut more where there was too little. There's no 3D GEQ.

This is true, plus moving a speaker a couple of feet in any direction will change its physical relationship to boundary surfaces that will create comb filters due to the reflections.

If it's a genuine room mode/standing wave thing, one's perception of it depends on where one in is the room, as Bennett says, and EQ will "fix" the problem in a small number of small areas while leaving the rest of the audience coverage with a big spectral hole in it.
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Greg_Cameron

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Re: Aux Fed Subs
« Reply #33 on: April 13, 2011, 03:47:54 PM »

My question was more about the situation of a room where there may be a "spike" in response at let's say 60Hz and my DSP is in my amp rack and not acessable from FOH . I agree that PEQ is better but for quick & dirty bar gigs you mostly don't have the luxury of an extensive soundcheck, I thought maybe an additional GEQ might be ok.

Dump the graphic and get a PEQ to insert on the sub output at FOH. I run a single channel Ashly PQX571 5-band on my subs. That said, I only need a 3-4dB cut at 50Hz, very tight Q, to get them sounding their best. But there's no way to do that with a graphic. You can get the Ashly or a Rane PE17 used for ~$150.

Greg
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Brad Harris

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Re: Aux Fed Subs
« Reply #34 on: April 14, 2011, 07:34:54 AM »

The only issues that I encounter when walking up to a buss driven rig (aux/group/mono out) is that the rig isn't aligned and level adjusted properly(slightly moreso than a fullrange setup) as I guess the thought is: the subs aren't used by everything so they don't need to be in time all the time, and/or the main PA doesn't need a highpass as the subs are for a little extra umph!

If you send a nominal level to the main PA and the subs, it should arrive at you at the same level and time (pending on how contoured you/system tech makes the rig non-linear)

I do alot of corporate (straigh up podium/wireless to multiact A list on a corporate event), and playback/artists are fullrange, where lavs don't need to be in the subs at all. A buss driven sub send is very handy as you can't always mute the subs exactly when the CEO is talking and playback is going on where if it's not being sent there, the work is done for you.

If the rig is setup properly (alignment and crossovers) then there should be no difference between a full range and aux driven PA (given sending everything to all appropriate drive busses)

BRad
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Art Hays

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Re: Aux Fed Subs
« Reply #35 on: April 14, 2011, 08:16:09 AM »

The only issues that I encounter when walking up to a buss driven rig (aux/group/mono out) is that the rig isn't aligned and level adjusted properly(slightly moreso than a fullrange setup) as I guess the thought is: the subs aren't used by everything so they don't need to be in time all the time, and/or the main PA doesn't need a highpass as the subs are for a little extra umph!

If you send a nominal level to the main PA and the subs, it should arrive at you at the same level and time (pending on how contoured you/system tech makes the rig non-linear)

BRad

Just for my own education, how do you do the time alignment?  Do the speaker processors provide capability to do this?  Do you have to use something like SMAART?  You can email me if this is too rudimentary to take up space here.  Thanks.
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Andrew Makinson

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Re: Aux Fed Subs
« Reply #36 on: April 14, 2011, 09:27:23 AM »

Just for my own education, how do you do the time alignment?  Do the speaker processors provide capability to do this?  Do you have to use something like SMAART?  You can email me if this is too rudimentary to take up space here.  Thanks.

The time alignment of the subs would be done the same way if they are bus fed or not.

The speaker processor should provide the ability to add the needed delay. 

Charlie Hughes has some excellent papers here http://www.excelsior-audio.com/Publications.html.  They do assume that you are using some type of measurement software (like SMAART), but can show you the theory regardless of measurements. 
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Re: Aux Fed Subs
« Reply #36 on: April 14, 2011, 09:27:23 AM »


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