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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: Robert Lunceford on January 13, 2016, 03:42:45 pm

Title: Creating a HPF
Post by: Robert Lunceford on January 13, 2016, 03:42:45 pm
One of the biggest omissions on the Allen & Heath QU series mixers is the absence of high pass filters on the outputs.
There is a PEQ (with shelving filters) and GEQ available on all outputs.
Is there a way to approximate a HPF using either or both the PEQ and GEQ?
If so, do you have recommended settings to program into these EQs?

The real solution would be if A&H included this feature in a firmware upgrade.
Title: Re: Creating a HPF
Post by: Douglas R. Allen on January 13, 2016, 04:23:41 pm
I don't have the setting right with me but I know with an O1v96 and just 2 filters I was able to make 100hz high and low cut filters.
Do you know what the Low Cut and High Cut filters are as far as slope in the Sub Groups if they have a high pass on them? Is it listed in the Manual? If its 12 db then 2 set at 100hz would be a good starting point. That may be a work around.
I'll see if I can find my O1v96 settings tonight to give you an idea.

Douglas R. Allen

Title: Re: Creating a HPF
Post by: Keith Broughton on January 13, 2016, 05:26:13 pm
One of the biggest omissions on the Allen & Heath QU series mixers is the absence of high pass filters on the outputs.
There is a PEQ (with shelving filters) and GEQ available on all outputs.
Is there a way to approximate a HPF using either or both the PEQ and GEQ?
If so, do you have recommended settings to program into these EQs?

The real solution would be if A&H included this feature in a firmware upgrade.
On my QU16 I set the Q of the low filter to about the mid point , cut the gain all the way down and sweep the frequency to approximate a high pass.
Adjust Q to get the slope that works for your application.
Title: Re: Creating a HPF
Post by: David Sturzenbecher on January 13, 2016, 05:30:36 pm

I don't have the setting right with me but I know with an O1v96 and just 2 filters I was able to make 100hz high and low cut filters.
Do you know what the Low Cut and High Cut filters are as far as slope in the Sub Groups if they have a high pass on them? Is it listed in the Manual? If its 12 db then 2 set at 100hz would be a good starting point. That may be a work around.
I'll see if I can find my O1v96 settings tonight to give you an idea.

Douglas R. Allen

The 01V96 has HPFs and LPFs natively...


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Title: Re: Creating a HPF
Post by: Douglas R. Allen on January 13, 2016, 09:02:50 pm
The 01V96 has HPFs and LPFs natively...


Sent from my iPhone using Tapatalk

Yes. I measured them to be 12db per octave. I came up with 2 ways to get the slope I wanted. Assigned channels to stereo subgroups with a 100hz high cut then another 100hz cut in the stereo L/R outs.

The 2nd way was the 100hz in the stereo subgroups cut (or L/R) with a parametric filter on the L/R. If I remember right it was around 200 hz low cut with a peq to make the slope steeper.
I copied the phase/slope trace of 3, 24db L/R filters with smaart then modeled from there. I have the traces and settings and will post them if I can find the time in the morning. The setting traces came out the same as the L/R filters.

If a low cut is available in his subgroups then maybe he can try those settings and measure them to see if they will work. I've never tried parametric filters alone. Maybe with a shelving filter.
Send me a QU and I'll give it a try!  ;)

Doug
Title: Re: Creating a HPF
Post by: Douglas R. Allen on January 14, 2016, 05:12:40 am
Yes. I measured them to be 12db per octave. I came up with 2 ways to get the slope I wanted. Assigned channels to stereo subgroups with a 100hz high cut then another 100hz cut in the stereo L/R outs.

The 2nd way was the 100hz in the stereo subgroups cut (or L/R) with a parametric filter on the L/R. If I remember right it was around 200 hz low cut with a peq to make the slope steeper.
I copied the phase/slope trace of 3, 24db L/R filters with smaart then modeled from there. I have the traces and settings and will post them if I can find the time in the morning. The setting traces came out the same as the L/R filters.

If a low cut is available in his subgroups then maybe he can try those settings and measure them to see if they will work. I've never tried parametric filters alone. Maybe with a shelving filter.
Send me a QU and I'll give it a try!  ;)

Doug

Pictures.

1. O1v96 low cut filter set to 100hz. 12dbs down at 50hz, 24 dbs down at 25.
2. 2 100hz low cut filters set to 100hz. 24dbs down at 50hz, 48dbs down at 25.
3. Home brew filter compared to the dual 100hz filter. 

The home brew filter is darn close. If he had a low cut in a subgroup it could work. I'm digging up the numbers tonight.

Douglas R. Allen
Title: Re: Creating a HPF
Post by: Douglas R. Allen on January 14, 2016, 05:25:17 am
I downloaded the manual for the QU. Seems there is no High or Low cut filters in the sub groups either. If I get a chance this weekend I'll try using parametric and shelving filters on my O1v96 and see if its possible at least in it.

Douglas R. Allen
Title: Re: Creating a HPF
Post by: Jeff Hague on January 20, 2016, 01:35:30 pm
One of the biggest omissions on the Allen & Heath QU series mixers is the absence of high pass filters on the outputs.
There is a PEQ (with shelving filters) and GEQ available on all outputs.
Is there a way to approximate a HPF using either or both the PEQ and GEQ?
If so, do you have recommended settings to program into these EQs?

The real solution would be if A&H included this feature in a firmware upgrade.

A PEQ with a shelf mode should be able to simulate it pretty close.
Can I ask why you want a HPF on an output? Is there no processing between the console and the amps / speakers?
Title: Re: Creating a HPF
Post by: Keith Broughton on January 20, 2016, 04:19:38 pm
A PEQ with a shelf mode should be able to simulate it pretty close.
Can I ask why you want a HPF on an output? Is there no processing between the console and the amps / speakers?
I often would like a HP on the aux outs to powered monitors.
Also use them for aux outs to telephone or web feeds.
Title: Re: Creating a HPF
Post by: Mike Caldwell on January 20, 2016, 06:03:28 pm
I noticed that and feel the same way.

Not sure if using PEQ's will give you same per octave cut off that a true HPF will.


One of the biggest omissions on the Allen & Heath QU series mixers is the absence of high pass filters on the outputs.
There is a PEQ (with shelving filters) and GEQ available on all outputs.
Is there a way to approximate a HPF using either or both the PEQ and GEQ?
If so, do you have recommended settings to program into these EQs?

The real solution would be if A&H included this feature in a firmware upgrade.
Title: Re: Creating a HPF
Post by: Robert Lunceford on January 24, 2016, 01:53:10 am
A PEQ with a shelf mode should be able to simulate it pretty close.
Can I ask why you want a HPF on an output? Is there no processing between the console and the amps / speakers?

Correct. No processing between the mixer and the active monitors.