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Need Help Setting Up, Using DBX AFS 224 Feedback Eliminators

lamdiglamdig Posts: 13
edited January 2014 in PA Configuration Wizard
This is kind of a new topic (for me anyways) but a quick check of the forum showed the problems one guy was having with K12s, etc. I bought a pair of AFS 224's quite some time ago and have been procrastinating in implementing them into my PA & monitor rig mostly due to inexperience.

I have a pair of Yorkville LS2104 subs, and the Yorkie U215 tops. I power these with CROWN XTi 4000's (mono bridged for each sub) + a single XTi6000 for stereo mid-highs. I also have an Allen & Heath GL2800-824 series console, using an ASHLY GQC 3102 for the two mid-highs, an an old RANE SP15 parametric for aux-fed subs. My monitor rig, where I think my inexperience is getting the better of me, consists of four QSC K12's that I am running with another ASHLY GQX 3102 for the 2 main singers (lead & main harmony/singer guy) and a DBX 231 for my other 2 mixes. I use a Sennheiser e965 condenser mic set to Cardioid, and a trio of SHURE Beta 87As which are Supercardiod. I try to follow the suggested monitor placement (direct in front for cardiod, off-axis 120-130 degrees for SHURE's. I have been plagued by feddback problems for the past 2 gigs and so finally gave in to trying the AFS 224s here in the house.

I hooked up the 4 channels of the AFS 224's to each of the 4 mixes. That is, FOH mixer to monitor send-through snake-monitor channel - AFS 224 - powered QSC K12.

I did my best to ring one QSC out with a GOLD LINE FD23 feedback eliminator (really "finder") - and yes, I know this is an aquired skill but I cannot afford to screw up at audio gigs while I drag myself over the learning curve of "hearing" frequencies. I went through the suggested protocol of increasing the volume until something (painfully) rings and then notching out the offending frequencies (so the Gold Line says anyways) and of course the vocals sounded a bit, but not a lot, wonky. Then I set the AFS 224 for the main channel to what I thought was LIVE, all 24 filters. It seemed to cut down on the feedback but I am wondering if I am doing things correctly.

The Quick Startup Guide was a bit confusing for me. I think I set up the one necessary channel (for one QSC K12) to 24 live filters, 1 minute live filter lift, music medium (even though I was only running the vocals through it), and beleive I DID NOT bypass the unit.

I understand I still have to "ring out" the K12s but am I using the AFS 224 correctly? Of course, the best of all worlds would be to minimally change the graphic (whether out of necessity or my inexperience in ringing the system out), and let the AFS 224 do all the work by finding offending frequencies and hacking them out for a short period of time.

Am I asking too much of the unit without providing my end of the equation adequately?

Is running the DBX's on monitor sends correct? FOH tends not to be problem, and monitors consistently are.

Are there other techniques, or ways to set the DBX's up that work better? Thx


  • DraDra Posts: 3,777
    What precision are you using?

  • GadgetGadget Posts: 4,915
    My goodness man you have a very workable toolset at your disposal... you would seem to be the weak link here... Sorry dude but in the hands of a professional the PEQ's available on the amps, and other tools you would only need the GEQ's as a "grab a fader and suppress a squeal/feedback" issue.

    The thing here is that if you had a Driverack you could tune the system and set up all the other components... but with ONLY the GEQ's and the FBX unit you can "ring" out the system...but then you would need to "season the system to taste", in order to avoid the "sterile"...boxy sound, or dull sound.

    That is the procedure where you continue to have all the mics open and at show volume, and raise the system volume till something feeds... the FBX catches the sonic signature and you read the frequency off the unit and place a PEQ there...further volume increases will expose other weaknesses in the system, use the PEQ's on the amps and you will be able to put 4-5 filters on the sound... If you can hear the differences you can do some of it by ear...but again, knowledge of the frequencies involved is critical if you want to tune the system by ear. (hint... use broader PEQ filters rather than narrow ones...)

    That's why the driverack is so popular...you can get the most out of your system without knowing much about sound...The "Pro's" will tell you they could do "better" and that might be the case...but with NO experience, the driverack narrows the gap considerably...

  • lamdiglamdig Posts: 13
    Thx Gadget, Sorry but I did not receive any notification that there had been replies to my post. Regarding your weak link comment..........yup -right on the nose! I have what I have at this point. How do I set live vs fixed filters and how do i know what ones? Thx
  • DraDra Posts: 3,777
    I got your Pm this morning, and replied but the server crashed, so all was lost.

    In a nut shell... I will set up the 24 total filters and 18 fixed (whether you fill them is another story). There will be a point that the monitors won't sound right and that is to far. Start with fixed on. I usually start with speech and let 2 - 4 filters latch on, switch to Music-low and let a few latch, change to Music-Med, etc , etc. The reason is the first freqs to howl are likely to be wider in nature and the later ones to be more narrow. When the mic is hotter than you need stop grabbing filters and change to live. I like speech with a 5 sec lift for live because they grab faster. If you get consistant howls after this you can go back to fixed and grab a few more. Remember, more is not necessarily better.

  • lamdiglamdig Posts: 13
    Just in from a late night at the office. Your response suggests settling on one setting, seeing what happens and then changing it to another setting, etc. Might be late and s jello brain is rampant but I did not deduce from the DBX "how-to's" that this was an iterative process. I thought you set it and threw the dice. Can you provide more detail on the steps involved?
  • I just bought a dbx 224 AFS i'm so confused :?: i'm not a soundMan,but i do want to understand my rig and how to use it.I play in a Metalband,but most of my stuff is dj equipment.i've been getting a decent sound out of it ,but alot of feedback in the monitor system,that's why i bought the AFS 224.ok i have 2 18"pyle pro subs run by a gtd power amp,250 watts per side,peak on the subs is 1000, both togethr,250 watts rms,per side,i have some gemini 15's 2 of them 1400 watts peak so i'm using a samson sx 2800,to run those 700 watts per side, i have 6 seismic 10"monitors 2 for drumer 4 for the front line 125 rms run by a pyramid power amp750 watts rms pers sidecan you explain to me the easiest way to set the 224 up to get little or no feedback?thank you!!!
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