HPF and LPF in LR and Monitor outs

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This topic contains 26 replies, has 18 voices, and was last updated by Profile photo of nottooloud nottooloud 3 years, 7 months ago.

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  • #58985
    Profile photo of GaryW

    Hi there,
    New to the forum having recently gone from an X32-Core + SB16 set up to the Qu-SB.

    I can use the GEQ to do a cut at say 31hz, but as I understand it that’s a narrow Q notch filter, not a steep High-Pass-Filter.

    To protect Subs and monitors from potentially damaging (ultra) low frequencies, could I request genuine HPF (and for consistency, LPF’s as well) on all Output channels? (Set on a per channel basis of course).


    Profile photo of mervaka

    The remit of speaker protection really should be with the PA. A good powered PA system will protect itself within the design of the amp modules. Likewise a well set up amp rack will contain protection for any speakers it powers, be that within the speaker manager or amplifier itself.

    Profile photo of Giga

    I use the PEQ to do that. That way you still have all your GEQ bands available for other things.


    Profile photo of GaryW

    Hi Giga,
    Unless I’ve missed something, the PEQ on the output channels gives me a variable width notch filter, or a rather broad shelving filter (by moving the ‘width’ slider extreme left).

    I could combine a low cut shelf with a moderate Q boost to in effect shape the cut to give it a steeper slope… but it’s not as effective as the option to add say a Butterworth 6, 12, 18dB/octave or a LR 24 dB/octave cut.

    Profile photo of GaryW

    Thanks Mervaka,
    Yes, I agree it should be, but with closed box active speakers it’s hard to know what has been allowed for and what hasn’t.

    From my own speaker design days, I know that a vented speaker rolls off at 24dB/octave because the output of the vent is 180 degrees out of phase with the driver, thus cancelling any in-cabinet air ‘suspension’ for the driver and therefore rendering it largely undamped below the -3dB point.

    As a safety when using an active vented design I always opted to add in a low cut just below the lower of the two impedance peaks to protect the driver from going into dangerously large excursion territory. While the amp would be fine, the cone could shred itself if driven hard.

    My personal preference is to protect my subs just-in-case the manufacturer cost-cut that option out. If I could do that at the LR or Monitor output it means that I can bypass the need to add in a speaker management processor.

    Profile photo of Giga

    GaryW: oopsie, I meant it just the other way around. My bad 😳


    Profile photo of Drummer Tom
    Drummer Tom


    You are SO right! As an “always active” box user these days, I want to protect my nice little powered 12″ 2-way speaker from getting slammed with some 20hz rumble or other “bad” influences. I called about this shortly after I got my QU-PAC and was told by tech support that while there was no true HPF, I could achieve the exact same results by setting a PEQ and adjusting the 31hz control on the graphic. Ummm, no way! Not sure where their EE degrees came from, but when I was studying for mine I learned why this would not be true. Do the math fellas! (Especially given that, according to the users guide, the GEQ’s are constant Q)

    I sure would love to see this feature added!

    Profile photo of Peter

    I agree that a good speaker management system is all that’s required for speaker protection but sometimes we all find ourselves working with less than ideal systems and on those occasions I too would find a HPF on the mix outputs a valuable tool.

    Profile photo of Peter Temple Studio
    Peter Temple Studio

    A HPF and LPF on the mixes and LR would be great to have on the QU-Pad. I Like to us a mix send as a sub send, and that way I can dial in a crossover point for the LR to the subsend anywhere in the room. I have that feature on a QSC Touch Mix and love it. Seems like a pretty simple software thing to implement to add that great flexibility. Cheers!

    Profile photo of Franksound

    I totally agree: Using a dedicated controller is what the “book says”. I would like to have this option in my console 🙂 (just in case, there is no dedicated controller around)

    Profile photo of BRS

    This would suit me very well too for a number of applications. I’m currently using a mashup and the GEQ to HPF and LPF – not ideal but just about works. A dedicated HPF and LPF on all outs would be perfect!

    Profile photo of BobA

    Couldn’t agree more. This feature seems to be missing on all their consoles (even their dLive consoles). How hard would it really be to add an HPF/LPF to the mains/monitors? It’s all software. Just write some code. Yes, in an ideal world everything would be taken care of at the proper place, but having been a sound engineer for a long time, I can tell you that the real world is anything but ideal. As GaryW mentioned, there are times when that protection is in place, but there are times when it is not so it would be greatly beneficial to have redundancies.

    Profile photo of Valentyn L
    Valentyn L

    LPF +
    HPF +

    Profile photo of GCumbee

    This has probably been one of the most requested items. I can’t understand why AH has declined adding it. And to that fact no one from AH has ever responded to this request to give any reason why it has not being implemented. I have wanted to hear an explanation.

    Profile photo of perri meracelli
    perri meracelli

    Hi, can anyone tell me h9ow I diable the Main L/R, so I can onlysiten in headphone, while I record do DAW, so I dont ahve to plug out the cables everytime .

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