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KP 480


mvdrums

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I have 8 kp 480's, and 4 kp 302's in a live band situation. Some of the 480's are bottoming out before others. Power is 6 each crown mt 2400's x-over at 120hz, house eq- anything below 40hz is at minus 12 db. Upon visual inspection the 18" drivers are not damaged, and pretty tight. The passives however, are a different story. some seem quite floppy, and others seem "tighter". The boxes are coming up on ten years old. Is there any way to tighten up these passives? I have no reference point to tell how tight they are supposed to be. The response of these boxes seems to be deteriorating. HELP!!!!!! 14.gif7.gif

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  • 4 weeks later...

you might wanna check and see if some of the cabinets have airleaks in them...at higher SPLs, feel around (or listen if it's not too loud) for air blowing out of the corners or anything like that.

The passive radiators extend the low frequency response by creating a state of resonation a little below where the active driver starts to roll off. This resonation would get screwed up if there was any kind of leak.

btw, how different is the bottoming out between the cabinets? You may just be better off cutting out anything below say 50Hz instead or even just turning the amps down a notch. I know this sounds like a bad idea when you're trying to get more punch out of a system, but there are other ways to accomplish that. For starters, try throwing some short reverb on the kick and toms, or perhaps throw in a compressor between the crossover and the LF amps. You may also want to crossover at a lower frequency and give those subs even less to think about...your mains should be able to handle down to 80Hz no problem.

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On 10/17/2004 10:23:40 PM DrWho wrote:

you might wanna check and see if some of the cabinets have airleaks in them...at higher SPLs, feel around (or listen if it's not too loud) for air blowing out of the corners or anything like that.

The passive radiators extend the low frequency response by creating a state of resonation a little below where the active driver starts to roll off. This resonation would get screwed up if there was any kind of leak.

btw, how different is the bottoming out between the cabinets? You may just be better off cutting out anything below say 50Hz instead or even just turning the amps down a notch. I know this sounds like a bad idea when you're trying to get more punch out of a system, but there are other ways to accomplish that. For starters, try throwing some short reverb on the kick and toms, or perhaps throw in a compressor between the crossover and the LF amps. You may also want to crossover at a lower frequency and give those subs even less to think about...your mains should be able to handle down to 80Hz no problem.

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Hey, Thanks for the reply! I think the surrounds on the passives are just getting old. I pulled a couple out, and one had the spider ripped completely out. It is really difficult to find a "starting point" since these boxes are 5 to 10 years old, and have had many recone jobs done. I have purchased a couple of new passives, and installed them. It helped a little. The boxes just don't perform like they used to. The house EQ is at minus 6 db at 50 hz, and everything below that is dumped at minus 12 db. 60 hz is at plus 3 db, and flat all the way up to 4k. This is a country/rock band. We don't play THAT loud. Yes I did check phasing. Again, I am running EIGHT of those subs. The room holds about 350. They should be able to fill the room no problem. I need to find a reference point, so I know where these boxes are supposed to be! No air leaks, except where the jacks go in. Even with the passive that had the spider ripped out, no air leaks. I realize the passive wasn't doing it's job, and probably damaged the driver as well. It seems to me, there are too many variables in this box to run multiples of different stages of repair/recone. Thanks, any Ideas? Matt

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I wonder if the problem might not be in your amps or the power supply or something like that.

One thing you might try involves a simple wiring change...for each amplifier, reverse the phase on one of the inputs. Then take the output from that same input and reverse it's phase (which returns the signal back to the original phase). This will give you about a 15% increase in power capability because the powersupplies in your amp will now be drawing power from the wall opposite of each other.

To prove whether or not the amps are at fault, you might want to run a test and "move the subs around" (just switch cables around at the amplifier end). While you're at it, you might as well play each sub by itself through every amplifier and pick out the cabinets or amps that aren't behaving well and look for any similarities. 5 to 10 years old is rather young for a speaker so they shouldn't be falling apart yet unless they're getting the crap beat out of them.

And for what it's worth, how do you have the subs positioned in relation to the room and all that? It's possible that there is destructive interference happening somewhere. Probably unlikely, but it doesn't hurt to ask.

Have you ever heard the system sounding good before? If so, what's changed since then? (and then change it back). Why do they keep needing to be reconed? Perhaps there's some electrical damage that occured in the past.

Sorry I'm not being of much help. You may want to swing over to www.prosoundweb.com and poke around and see if you find any solutions. There is also an amazing forum over there where you'll be sure to get many more responses.

One other thought just popped in my head...are the subs bottoming out or is the metal grill on the front vibrating? I had a speaker once where the grill would vibrate like crazy and I swore it was the driver...Simply tightening a screw fixed the problem!

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