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Author Topic: Aux fed vs a lot of hi pass filters  (Read 2791 times)

Steve Hurt

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Aux fed vs a lot of hi pass filters
« on: March 12, 2011, 07:38:10 PM »

I use a LS-9 so I have lots of high pass filters

I hi-pass every channel I don't want in the subs at around 100 hz (sometimes higher if that's needed for other reasons)
The subs cross a bit below that.
How will an aux fed system sound different than what I'm doing?   

Just the master fader for the subs? 
(I can adjust the subs gain in Driverack crossover via my laptop now)
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Tom Young

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Re: Aux fed vs a lot of hi pass filters
« Reply #1 on: March 12, 2011, 08:40:01 PM »

I hi-pass every channel I don't want in the subs at around 100 hz (sometimes higher if that's needed for other reasons)
The subs cross a bit below that.
How will an aux fed system sound different than what I'm doing?   

Just the master fader for the subs? 
(I can adjust the subs gain in Driverack crossover via my laptop now)

Aux fed subs effectively behave as a brick-wall high-pass filter but without the inherent phase consequences this would entail. If you do not assign an input to them, there is nothing at all from that signal going into the subs. Nada.

Whereas a channel high-pass filter typically has a slope of 6-12dB per octave. Therefore; there is LF energy that does get into the subs. Depending on how many open mic's you have on stage and where they are relative to one another, at lower frequencies there is always going to be *some* degree of addition going on between them.

The audible difference (for me) has always been greater with larger productions with, for example, choir microphones. But one can also quite easily hear the difference between aux-fed and traditionally fed subwoofers with a bar band with the drum kit mic'd and several open vocal mic's. Until I began to play with this I thought "how could this possibly make much of a difference ?". It is often subtle but it *is* well worth doing.

If you do try it, try it on various typs of shows. And let us know what you think.
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Tom Young
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Brad Weber

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Re: Aux fed vs a lot of hi pass filters
« Reply #2 on: March 13, 2011, 11:12:08 AM »

Whereas a channel high-pass filter typically has a slope of 6-12dB per octave. Therefore; there is LF energy that does get into the subs.
I think that is a critical difference as people tend to overlook that many high pass/low cut filters result in content even an octave or two below the filter frequency being reduced in level but not eliminated.  How that is relevant will differ between situations, but it is a difference.
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Sheldon Harris

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Re: Aux fed vs a lot of hi pass filters
« Reply #3 on: March 13, 2011, 02:45:02 PM »

I use a LS-9 so I have lots of high pass filters

I hi-pass every channel I don't want in the subs at around 100 hz (sometimes higher if that's needed for other reasons)
The subs cross a bit below that.
How will an aux fed system sound different than what I'm doing?   

Just the master fader for the subs? 
(I can adjust the subs gain in Driverack crossover via my laptop now)

aux subs. all the way. high passing not the same.( before i started using aux subs a few years back, all ch. were always high-passed. switching to aux subs cleaned everything up to a larger degree. i say, try it, run the left subs aux and leave the right normal and compare. could be done quickly and seemlessly depending on your loudspeaker processor.
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ProSoundWeb Community

Re: Aux fed vs a lot of hi pass filters
« Reply #3 on: March 13, 2011, 02:45:02 PM »


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