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PA question:Bass and speakers breaking up

dmraco

Master Member
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I am getting my PA an upgrade.  I have a QSC QX5, 1000W (500 Each Side).  I am using the build in cross-over, one channel with the lows powering my 1x18 Peavey Sub (400W continuous ).  The other side (highs) powering two Carvin 1x12 with a horn, each rated at 300 W continuous .

When playing my iPOD even at SUPER high volume, everything sounds great.  NO breakup.  Even jamming SIR MIX ALOT and SEAL, both Bass heavy songs.  However when I run a bass guitar direct or even with a mic, I get break up.  Even a SUPER LOW volume.  The 1x12 speakers have a crackle.  What gives??  IS it a power issue?  Not enough?  I know it cannot be too much. It is not a gain issue.  These speakers just do not like the signal.  I think my cross over cuts things at 20-100Hz for the sub.  100hz to 20kHz goes to the 1x12.

Thanks
 
Anything you hear coming from your I anything or any other commercial recording has had the bejesus compressed out of it. Your bass contains all aorta of raw unfiltered naked transients, even DV stuff (try hitting the pickup while muting).
 
What kind of board, and what is the EQ doing, and is the bass active?  I usually set the (external) crossover at 120 to 150 Hz.  A tip I picked up from several sound men is to leave the bass (guitar) flat or even cut it a hair below 60 Hz.  It's not really audible at frequency and can be a waste of power to reproduce the bass (guitar) at that frequency, especially if the kick drum is also mic'd. 

Your Carvin 112s should be full range speakers, a 12" sub and horn, so even without using the crossover and sub, they shouldn't break up or distort at a reasonable volume.  The sub and crossover design just allows for a more efficient delegating of specialization. 

Like several boards with a built in crossover, the sub out portion is usually the only crossed over portion. Your main outs are usually still full range, so the below 100 Hz portion is being doubley produced.  Also, many stereo poweramps with independent channels, even though the manual may say otherwise, the 2 sides really don't like different impedances with different signals.
 
I have used the low cut and it does not help.

It is an Alesis mixer with a QSC power amp.  The cross over is in the amp not the board. 

The sound is not so much the speakers breaking up, but the sound being distorted.  Like there is a small amount of fuzz.  The system sounds great with every other instrument including keyboards.  Should I run the bass signal thru the compressor??

Here is what my amp looks like on back
20140817_132201_zpsj9atxlvh.jpg
 
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