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EQ / Equal Loudness / Turbosound

vicvic Posts: 10
edited September 2006 in PA General Discussion
Hi fellow druggies
Vic here, long time reader, first time poster
Bit of an all encompassing subject, but please feel free to point me to any archives that I would appear to have missed. I have been there and downloaded quite a lot (including the test CD)
First off my set-up, feel free to point out set-up errors
Allen & Heath GL2200 432 (which has pink and 1k sine generators)
Turbo TXD252 (2 x 15 + horn) + Turbo TXD215 (2 x 15)
The 252's are used full range (at present, bi-amp is in the pipeline)
The 215's have had the internal x-over bypassed, not as easy as Turbo would suggest
Main amps, pair QSC PLX2402 bridged
Sub amp, Yamaha PC9501N parallel / stereo
I will use the 252's on their own for smaller rooms and therefore have a couple set-ups in the DRPA
My main work is the in metal / punk scene, from extreme hardcore death metal thru to pop punk. I also work for a jazz promoter and a number of local councils covering most styles
With me so far?
At the moment I have a dbx 1231 graphic ahead of the DRPA as I feel than some tour engineers may prefer the hands on sliders approach.
I aim to use the graphic in the DRPA when I engineer gigs and push the 1231 into the monitor chain. At present I use the DRPA as a x-over and limiter. Right on to the questions
System EQ - I have read many pieces about the science, and there seems to be many opinions on the subject, from using the graphic to push the system up to feedback point at all frequencies, to notching room nodes and creating an equal loudness pattern (is it Robinson-Dadson or Fletcher-Munsell curves). I tend to favour the equal loudness curves and as such have the lows 63 - 80 at 0, then a gentle curve down to -12 at 500, rising slightly, -6, at 1k - 2k, then down again, a slight peak around 4k - 5k (where a lot of metal acts like the click of the kick drum) and then tailing off in the highs. This seems to give me a reasonable balance at most venues, indoors and outdoors. The upper mids are still a little harsh, but I believe that is because in full-range mode the horns are heavily padded and therefore always recieve the maximum power and the cabs have to be driven quite hard to flatten the response. (Please correct me if I'm wrong). Yes I use my ears, and most crowds and bands like the sound I achieve, so should I worry that some of the cuts are quite extreme. Opinions please
I do have the dbx RTA mic and plan to pink out the occasional venue. I have read up on the indoors procedures but would like advice on outdoors work. My amps deliver more power than is required and I therefore engage the limiters, so I am worried about pushing the pink noise too high and damaging my drivers so any advice on the level of pink noise would be helpful alongside general set-up procedures.
And finally
In the back of the DRPA manual there is a section on maximising gain structure. I would like some opinions on the dbx method. Firstly I have been told that amps should not be run without a speaker connected as is required in this procedure, is this the case? It also mentions getting the amps up to clip level, but I need to ensure that the amps dont deliver their full power as I could damage my drivers. I have calculated the maximum voltage the cabs can handle and can always measure this at the speaker input. They also recommend running the desk very 'hot' and the amps 'cold', where as I though that the amps should always be full on and the levels controlled from the desk, again some input would be helpful. The last few paragraphs also seem to contradict themselves. You are asked to set the limiters on eash band, then run the Wizard which will set the limiters according to your amps (even custom?) and then you have to reset the limiters.....is it just me?
Well I best stop here because I have waffled on for a while here
Feel free to help/abuse/ridicule in equal measures


  • GadgetGadget Posts: 4,915
    Gadget here... Um I guess I provided a lot of what you have read.. the thing about what you are doing is not taking into consideration the fact that the speakers to deliver equal energy would require a FLAT response curve. You are using a method that was popularized back in the day when these marvelous tools were not available at any cost. I achieve the same effect, your gently sloping curve, by setting a flat response and \"seasoning to taste\"
    If outdoors, away from all reflective surfaces, use the Auto Eq to set up a flat response curve, store it and use it for comparrisons, and hard rooms, where any unnecessary energy will be destructive in nature.one stack with the mic in the nearfield and on axsis will give the best results... Indoor Auto Eq requires a totally different approach, use the indoor method I posted for the tops and do the low end EQ manually.

    As for this amp issue.. I think you are being missled. Too much power is going to do 2 things. present a tighter, more defined sound, especially the low end...and prevent damage to the speakers from exhausted power supplies(unless you bottom the voice coils against the mechanical stops which makes a horrible racket as opposed to the relativley quite death of clip related failure). Crown suggests 2 to 4 times the speakers rated power...Trust me too much power is never enough! if your seeing clipping on the amps and the speakers aren't distorting noticably you have RUN OUT OF POWER!

    If you look at my GEQ you will notice a pretty much totally flat response... I do end up pulling some 200 and 4-500 some times when running indoors as my volume gets really loud,and room resonances build. I use my PEQ's for system tuning, so I don't have the extra bands necessary for these cuts, so the GEQ is called in to do the job.

    As for the gain structure issue, the idea is to get everything so that it clips at the same point, and all the equipment is then running in its optomum gain area. the amps want to be below that point if at all possible.. that way when the board is near clip, you know the whole system is at the same point, except the amps.. they should still have a little headroom. The modern amps have no problem with no load situations... Crown Mac and some other amps use unconventional clip systems, and traditional gain structures are not possible with them.

    Suffice it to say the the goal of the gain struscture is to get each system piece into its most linear range. just like the mixer where the faders have a \"0\" point, which is the design canter that provides the maximiun gain and the least noise.. so it should be with the rest of the system..

  • vicvic Posts: 10
    Thanks for the reply Mr Gadget
    Informative as always
    I was hoping you'd tip up
    There is a guy on the Mackie forum who always has the answers, it's nice to know there are a few people who enjoy imparting their wisdom

    EQ shape - Thanks. As I have said, I read enormous amounts of tech stuff, from the web and in books, and the equal loudness shape was down to a book I read . \"Audio Engineering for sound reinforcement\" by John Eargle and Chris Foreman, a JBL supported book. I have also put in my rig for tour engineers, and they have used this sort of 'smiley face' with some node tuning. A difference of at least 12dB from the 80Hz area to the 400 - 630Hz region. I'll try a few different curves. As always tho, the ears have it.

    Outdoors EQ. Yep, gonna try that this Saturday. Now you say to only use one stack, now is that with the DRPA in stereo mode with one stack turned down or the DRPA in uncoupled mode and terminate the EQ after the one side is done. I take it it is ok to run with the sub too.
    I also plan to do a full stereo check with both stacks running as a comparison.

    Amp Power - Yep I'm fully aware of the amp power formulation (0.8 to 1.25 x programme rating) - Which is why I bought the amps I did - I have an issue with Turbosound which is why I will be going JBL - if you want to make any observations on the problem I had, feel free to mail me - vic at vwpsounds.com
    My worry is, if I haven't set the limiters, and then pink the system the amps could clip and destroy the drivers. This is why I want to use the correct order of things

    I have read a lot on gain structure and found a great piece in the dbx archives which gave me a couple of ideas. I pretty much do everything that is recommended apart for the amp settings. Some camps have the amps flat out and run levels from the desk others use all the headroom at the desk. With my amps, QSC PLX and Yamaha PC9501N, will I be cool to use the procedure in the back of the manual. I'm going to burn that test CD down, but I do have pink and 1k sine in the desk

    Should I used the limters in the amps - or turn them off and rely on the DRPA?

    Thanks for taking the time to help out
    Vic - www.vwpsounds.com
  • vicvic Posts: 10
    and another...
    is it worth rolling off the low end?
    i used to use a 12dB/oct L/R and swept it upwards until any nasty rumbles disappeared - i aslo had my graphic pulled down at 20 and 31.h
    i hate those big wallowy bass sounds
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