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Blown Speakers?


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#1 drumrider

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Posted 23 January 2012 - 07:41 PM

I bought a used complete pa system, includes Peavey rq2326 mixer, 2 2-18 PAS subs, 2 2-15/2" high horn tops, 2 xls802s, 1 Carvin dcm 2500, 1 peavey pv-4c , a dbx driverack pa processor. The system is set up with one 802 running each sub, the speakers are 8 0hm so it's running at 4ohm, speakers were a combination of EV and older PAS speakers that came with the cabinets, these cabinets must be 15 or more years old. Still look good, sound good except for the noise I am hearing at a pretty good level. We have had three of the 18s start making a braaaapppp sound under load with lets say a good kick drum and bass guitar lick at the same time. Not all at the same time, but one speaker during one show, another at another show, etc. My questions are how much power is the 802 delivering at 4 ohms, I have read on this forum its not recommended, but thats how it is, I will deal with changing it later. What do you think is causing the speakers to make this noise, they still sound fine at lower volumes, you can crank a cd or ipod to intollerable levels and still clean. Start running a band mix through it, and the kick and bass will cause it. I have replaced the speakers that were making the noise, thinking they were bad, they still test 8 ohms, with B52 18s rated at 1000w. Do I have enough power, did lack of power kill these speakers, or is running the amps at 4 ohms killing the speaker.

I have asked for help from dbx, no answer, another board, no answer. A little help would be GREAT!

Thanks in advance for anyone who knows anything about this



#2 dakos

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Posted 24 January 2012 - 12:44 AM

Hello there and welcome,
Let's start with the simple questions first, the power at 2 ohms is 1050W per channel and at 4 ohm bridged it's 2100W, BUT... You need to read this first.

Now for the noise, I'm not sure but I think you are putting too much power into the subs at frequencies too low for them to operate in, thus causing the end of the voice coil to hit the backplate of the magnet making this terrible sound... You need to fix this or something will break sooner rather then later. You need to find out the lower -3dB point of the subs for the cabinet they are installed in, so which model are they? Can you post a link to their manual?
After you find out that spec, you need to enter it as 24dB/octave L/R high pass filter for the subs, this will help protect your speakers. You might also want to set the limiters on the DRPA to help further protect your speakers.