# Audiocontrol modules...



## Candisa (Sep 15, 2007)

Hi,

As you can see in my project, I own an AudioControl EQX and 4XS. Those will be used to build a 3-ways + sub setup, but I have a question about them...

Both crossovers work with modules and both have a 'PFM' (AudioControls name for subsonic) module in them. Standard this is set to 30 or 33Hz and off course I want my system to play as low as my subwoofers allow. 

Now the problem: the signal going to the subwoofer amplifier passes trough both crossovers, so trough both subsonic filters. Off course I'll use one of them to protect my subwoofer, but a second one would only lower the bottom-end output even more, even if I pick the same frequency or a slightly lower one. 

I have 2 possibility's: 
- find out on what frequency I have to set both subsonic filters, to become the same effect as 1 subsonic filter at the desired frequency
- disabling one subsonic filter
I prefer disabling 1 subsonic filter, otherwise I'd have to change both modules if I want to change the subsonic frequency. The only way to disable the built in subsonic filter (since there is no other way to disable it) is to set it to a very very low frequency. 0Hz is the lowest 'frequency' I can imagine...

AudioControl crossovers use higher value resistors for lower frequencies and lower value resistors for higher frequencies, so to set the lowest frequency possible, I'd have to use the highest value resistor available...
The highest value resistor I know here on earth is... air, meaning I should just leave the frequency module bank of 1 of the subsonic filters open. (easy  )

But... Can I do this? Aren't there any limitations to the lowest frequency I can set the subsonic filter at/highest value resistors I can use? 

If you use the 4XS as a 2-channel 3-ways filter, there is 1 module inside that isn't used, but the manual says there has to be a module in that bank, but they don't say anything about the PFM... 

greetz,
Isabelle


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## 60ndown (Feb 8, 2007)

id call em.

http://www.mobileaudiocontrol.com/contact.asp


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## Candisa (Sep 15, 2007)

I live in Belgium, that would be an expensive phone call, and my spoken english is terrible.

But I just read the manuals of both devices again and apparently the 4XS has a 'PFM Defeat' function. I guess that means I can disable the 'PFM' (subsonic filter), but still use it as a 3-ways crossover (it would be a bit ridiculous to let it act as an expensive line signal splitter, wouldn't it?), so only the subsonic filter of the EQX is enabled (like it should be).

greetz,
Isabelle


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## Biowaste (Apr 25, 2008)

This won't answer your question, but I am in the same boat with the 4XS.

The instructions aren't very clear for me either. I love AudioControl, but their units aren't user-friendly or very flexible (at least, on the fly) at all and I definately don't consider myself a novice either.

Anyhow, I had a question about another product of theirs and just emailed them. They responded very quickly and answered my question.

Hope this helps,
-Bio


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## cheesehead (Mar 20, 2007)

Biowaste said:


> This won't answer your question, but I am in the same boat with the 4XS.
> 
> The instructions aren't very clear for me either. I love AudioControl, but their units aren't user-friendly or very flexible (at least, on the fly) at all and I definately don't consider myself a novice either.
> 
> ...


I have also contacted AC via e-mail with good luck.


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## SQfreak (Feb 13, 2007)

As far as the 4SX, all 5 modules have to be installed or you could short the board. If you want full pass on the PFM then put in a lower module, like a 19htz cut off. You cant hear it anyway but it will still keep the woofer from trying to reproduce it (save those VC's!) Anyway if you drop a matching module in both units then you will simply increase the DB slope of said cut off ( e.g. 19htz) But without all 5 board resistors installed the 
4XS will short.


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## 89grand (Nov 23, 2006)

Yeah, I've used some AC gear over the years (24XS, Epicenter and 4.1) and didn't care that much for the PFM filter not being defeatable either. I never noticed any low information missing, but just knowing it was there bugged me. 

I think using a different value resistor network is the only option, but I don't know what the value would be.


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## PaulD (Nov 16, 2006)

I still have the 4XS and EQT's I used to use a long time ago. I made a module that had a cut-off of like 19-20 Hz for the PFM. It's not that hard, just follow the formula .... if you don't have the formula for figuring the resistor value let me know - I still have the info around here somewhere in a folder.


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## Candisa (Sep 15, 2007)

Thanks for all the information folks, I have the formula and I discovered the 4XS actually has a defeatable PFM, so my problem isn't solved, it just wasn't there 

greetz,
Isabelle


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## GlasSman (Nov 14, 2006)

Candisa said:


> Thanks for all the information folks, I have the formula and I discovered the 4XS actually has a defeatable PFM, so my problem isn't solved, it just wasn't there
> 
> greetz,
> Isabelle


Yep from what I remembered the 4XS had a defeatable PFM.

The analog Audiocontrol units are much too limited when experimentation and tuning options are a priority.

Not my cup of tea at all.

When you compare a 4XS to a PXA-H700/701.... it really is laughable at how limited you are with the 4XS.


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## Biowaste (Apr 25, 2008)

I feel stupid here, but can someone explain a little more what the PFM does exactly?

Thanks :blush:
-Bio


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## capnxtreme (Feb 5, 2008)

PFM is just AudioControl's term for an infrasonic ("subsonic") filter, which is just a HPF to keep the sub from overexcurding.


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## Biowaste (Apr 25, 2008)

Ah-ha! 

Now it makes sense.

Thanks,
-Bio


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## file audio (Mar 12, 2013)

so.... I have the great eqx,, it has a inside switch in the pfm it has to be defeated? or activated? what does it ffects? it only affects only the sub channel or the low pass filter channel? 
this is a funny thing I have this eqx installed on my truck with premier prs880 and focal krx3 and I always love how it sounds with the eq in button pressed down (not bypassed) but one day by mistake it was depressed and I realise it sounds more powerfull and clean then I let it play so,,, it need to be pressed down and re equalized again? to achieve that same sound and better ? maybe was my bad eq,s setings and I was cutting too many frecuquencies before?? any advises? im missing something with this eqx bypassed? excuse my english spanish is my native tonge


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## KillerBox (Jan 7, 2011)

I hate to bring up an old thread but, since my DSP (MS-8) has a subsonic filter controllable from the driver's seat. 

I wanted to know if I took the chip completely out and left the socket open, would it totally bypass AudioControl's subsonic filter. Or am I stuck with some type of Subsonic filter from AudioControl. 

In case it matters, my AudioControl MVCs use the 18dB - 14 Pin modules and they currently have the factory default 33hz chips installed.


Thank you for the help!


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## cmusic (Nov 16, 2006)

I would not remove the PFM filter chip and turn your AC MVC on. However you can buy replacement PFM chips straight from AC from this web page: Crossover PFM Modules - AudioControl

On this past Monday I ordered a 15Hz, 18 dB/Octave PFM chip from AC for $10 plus $6.95 shipping to replace the 33 Hz PFM chip in my Epicenter.


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