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Sound System cutting out

mwrutlandmwrutland Posts: 10
edited September 18 in PA General Discussion
I have just recently started using the driverack pa and since i have started using it i have had issues with the pa cutting out mid performance. I know that the db meter on the driverack isnt peaking but at unity my amps are peaking and the failsafes are cutting the amps off for about 20 secs. i just remembered today of the db attenuator on the xlr inputs and that may be the problem but could it also be the way i am pinking the rooom. When i am pinking the room to performance level the gain is usually well above 0db. i did not think about it untill today that the db level of the pink noise could coincide with the main levels. so maybe i am overdriving the amps from the driverack but my input from the console is not peaking. could that be my problem as well. at that point is the output gain of the drive rack greater than what the input reads. the quick fix for the past three shows has been the sound man pulling the master down around 15-20 db to keep the amps from peaking but at that point i have lost gain structure. i have never been a fan of main mix compression but maybe thats the answer as well. i am going to check out the db attenuator tomm but if anyone has any advice please send it my way.


  • GadgetGadget Posts: 4,915
    Since the Auto EQ is simply a db based per frequency volume process, if your not aiming for flat frequency response (predicated on LOUD ... concert volume sound) then yes, that could be a problem, IF, however, you are set flat and using the Auto EQ to set a concert volume speaker equalization, then I would have to say you have not set the gain structure with the system set to concert volume. Hmmm does that make sense...? If ... you have gone through a system set up.... (done a proper wizard setup, selected the proper parameters, then loaded the program...set up the crossover properly, set up the amp/speaker sensitivity using the amp input controls.. and or the Driverack xover gain controls...

    I.E. if we have the same exact amps for ALL speaker components, and we have a 3 way system that has a horn that is 107 db efficient (@ 1 meter and with 1 watt input power) and a mid range that is 98db efficient (same as above) and a sub that is 94 db efficient... we would somehow have to account for the difference in efficiency ... correct? we have two things at our disposal ... the amp sensitivity control, and the crossover gain control... I know this isn't intuitive...but we can use one or BOTH to accomplish this task, here we concentrate on simplicity as to not be too confusing, and as such we would suggest that the horn, being 107 db efficient will be 13 db MORE efficient than the sub, and 9db more efficient than the mid range... we either need to turn DOWN the horn amp then 13 db with respect to the sub, or use the xover gain control ... or both... real world situations have us using a LESS powerful amp for the horns simply as a matter of cost...SO, if the HORN amp is less powerful than sub amp...then we need to take that into consideration as well...

    Now, that said... you haven't provided enough information for us to be able to discern what is really happening here... did you read the \"Read me first before posting\" section? Because if you had... you would know we require ALL SYSTEM COMPONENT information to even give you a response... which you have not provided... NOT trying to be a hardass here... BUT look at it from our perspective... you are obviously not a total beginner... but you haven;'t given us much to go on now have you?

  • absolutly agreed. I am running a Two way stereo system. Tops consisting of 1 PAS TOC Dual 15\" and coax horn Line array top per side and 1 !8\" Peavey low rider sub in a long throw EAW style enclosure. tops are 4 ohms cabs with a power rating of 600 WATTS EACH. subs are 8 ohms each with a power rating of 1600 watts each. tops are pushed by a qc plx2402 amp in stereo mode which delivers 700 watts @ 4 ohms. subs are pushed by a peavey pv2600 in bridged mono mode pushing 2600 watts to both cabs (1300 each give or take) This rig is used in my touring cover band. the tops are amazingly clear and the long throw subs enable us to fill a room without having to have a large PA. the tops freq response are 40hz to 16khz. subs are 25hz to 500hz. to keep from having overpowering low end i have crossed the highs out from 125hz up. and the lows from 250hz down to 30hz. with a hp bw at 30 hz. speaker tuning calls for min of 25 hz but i have set the subs to not go that low. my crossover is a lil unorthodox but it allows the kick drum have defined low end in the sub and still have attack through the tops. because subs have a peak rating of 3200 watts each i keep the sub amp at full gain. i keeps the high amps around 7/8 power. i have not had any distortion or bad sound at all just the cutting out. i do know the clip protection is on and i did read after the first post that u recomend not douvle layering clip protection. we usually do a 3-4 song sound check and we have no problem but 3-4 songs into the set we experience this problem. lately i am used to my line array rig but we do not try to acheive concert level loudness. And i do know the difference. i opoerate and engineer my own production company doing 3-4 national acts a month. because we play mostly in 200-500 seat clubs we dont need a giant or loud rig. we have a very clean tight sound. it just wants to cut out on us. once again i must check the db attenuator because if im adding and additional 14db from unity then that would explain why i have to bring mains down 15-20 db to keep from cutting out. i appologize for not reading first. but could u do me a favor and send me a link for the read first part, im having trouble finding it.
  • DraDra Posts: 3,777
    On the main index page...
    http://www.dbxpro.com/forum/index.php?s ... ca1e10270e
    Open the START HERE thread.

  • GadgetGadget Posts: 4,915
    Well, I figure its a couple things... First your under powered... pure and simple, and then you exacerbate that with a double limiter setup..

    1. The amps are limited down from their rated power when you engage the limiter on the amps.. that is to say with an amp of 2400 watts you actually limit the output to about 1800 watts...

    2. In the normal mode...the amps duty cycle is expected to run well under 30%... the is to say if the amp can put out 100 volts continuous it would only normally average 30 watts... when you engage the limiters, the duty cycle will start to spiral up... once the duty cycle reaches 50% the amp starts to heat up, and I believe you are experiencing thermalling...

    3. What Dra was pointing out was that you haven't set up your gain structure... If you had, you would know when your amps are near clipping...because the mixer would already BE clipping...there is a method to this madness...

    4. You are overlapping the crossover and that is also contributing to your woes... did you realize that with that large an overlap that you are suffering cancellations that you are having to push harder to recover from? when two speakers in near proximity reproduce the same frequencies and the electrical signals arrive out of phase ...cancellations occur... Why do you suppose speaker manufacturers that have 2, 15 woofers together in the same cabinet... cross one of the 15's @ about 300hz? It's a quasi~3 way design that limits the interaction in the lo mids...They also use a BW 24 filter design to limit the interactions in those regions...

    I would
    a. dump the limiters
    b. set the crossovers @ 45hz BW18 HPF, 120 hz BW24 LPF subs
    HPF BW24 @ 112 hz tops
    c. do a proper system setup and gain structure as per the \"Start here thread\"

    You know, those TOC speakers can REALLY CRANK :shock: when Bi-amped, and powered properly.. I know we have 6 in our extended network... Those will keep up nicely with 6 LABsubs which outdoors can be FELT... nearly a mile away!

  • agreed. and i do understand about sound cancellation. TRUST ME. i have a meyer sound line array as well as a samller dnyacord line array in which i spend 50% of the set up time angling my cabs in a new room. i do agree with you on the xover theroy, but at the same time i know that in my recent mixes i have had to increase low end range to 200 hz to acheive the full range sound in the back of some rooms. i dont know if your aware but the toc tops have a dual 15 but the top 15 which is the mid driver has the horn through it. the bottom 15 is the mid-low driver and in a long room situation it tends to fall off at the 180hz-250hz range. granted this is my ear and im not saying its right but it does acheive a more full sound in the whole room. BUT as i do not know everything what is it gonna hurt to try it your way. granted i have done the homework on all my cabs and set my parameters to their specs. I will say this, Prior to use of the driverack we had no problems with amps cutting out and we did have a \"LOUD\" system. BUT it has never been so clear and easy to use as it is with the DRPA. it also helps that instead of having 12-16 rackspaces of assorted gear 1 rack DRPA does it all. And when you are a touring cover band traveling with full pa (foh, monitorworld) Martin intelligent rig, and full backline, not to mention 4 musicians and 3 crew, SIZE IS EVERYTHING. I do greatly appriciate the help and you are absolutly right about the TOC cabs. they rock. crystal clear and blistering powerful. For the sake of adding another power amp to our already cruise ship anchor amp rack case we dont bi-amp the tops. they have some of the best xover networks in them and work wonderfully. it also allows us to use 4 core wire with NL4's and run the sub and tops on the same wire. reducing cable cost and amount of time spent running them. Once again i appriciate your time helping me to configure this new toy. while it is similar in the approach to the processors used on the line array rigs it is a lil more all around application (which is awesome) and i just gotta figure out all the details. thanks again. Wes
  • GadgetGadget Posts: 4,915
    Why not insert a PEQ where the dip is.. say a Q of about 1 and put it at 210 hz and then play with the gain and the Q and see if you can't get that to help?
  • i will try that as well. luckily we have the week off and i can set the rig up in the warehouse and tinker around before the next show.
  • DennisDennis Posts: 801
    The PAS Specs do not indicate there is one 15\" for mids and the other for low mids. They list only one xo point of 1.2kHz. Biamping, as Gadget suggested, should give you more control in your lower mid-range problem area.

  • im not sure which speaker spec you looked up. but the ones i have are the RS 1WR which un like its big brother the RS 2.2 that is intended to be bi-amped, mine have a passive dividing network built in which doesnt allow for bi amping. well it could if cab was rewired but would defeat the point of the xover's design. i could be wrong. and they are designed for the second woofer to have lower extended freq. it is a great rig. and without biamping it is a clear powerful rig.
  • GadgetGadget Posts: 4,915
    Yes, we have the RS1.2 with the xovers, but we simply bypassed them and now they ARE the 2.2's and now they REALLY rock :shock: :shock: :shock: And no I don't think P.A.S uses the ~ 3 way, but Peavey, JBL, Yorkville, do for sure...

    Man, that's what those PEQ's are for....just remember, rather than surgical narrow bell curves try an broader Q like around 1.o to start with... If you find some harshness in the upper mids try a Peq there as well...but use a slight cut... move it around and see what happens, play with the gain as well to get it dialed in right!
  • well im sure you can understand why we choose the KISS method for our applications. you would not believe how i cam across these cabs. someone traded them in to a local guitar store that had no idea what they were (i think they might have been stolen from somewhere) but before the manager could do any research i offered him 600 nucks for the set and he took it. not bad considering they are 1700 bucks each.
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