Problem with sub I think

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Oct 22, 2003 | 03:52 AM

kazino21

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Problem with sub I think

I have a Polk momo sub hooked up to a JL 500/1, it was meant to be a JL W7 but there was a scam on ebay and luckily i got my money back. But anyway this is temporary. The problem is that the sub keeps on rattling when being played a little loud, i am running a symphony head unit with blaupunkt adaptor and a phoenix gold line driver to the JL. I have to put all the setting on the jl to really low i.e the middle range frequency, the crossover slope is on 24db and 25 hz. I don't know what is wrong with the sub, I had bought it second hand so don't know how much abuse it had taken before. It's only a 10 incher and I have put it in a sealed custom made fiberglass enclosure that I tried to make. I thought maybe the enclosure was a little large so put lots of sponge and stuff in to make it smaller and it in fact made it worse, the sound sounded much softer. I tried to mount the sub inside out to a poor effect it just distorted all the easier. I don't know what's going on it's meant to be rated at 400W RMS and the amp is 500W rms, so I should be able to get something out of it.

Oct 22, 2003 | 05:57 AM

01blackS4

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sounds like the box is not sealed

Oct 22, 2003 | 06:51 AM

kazino21

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I have felt around the box and can't feel any air coming out of it

I felt around top and bottom of the box and it doesn't seem to be letting any air out.

Oct 22, 2003 | 06:59 AM

John P. (TT 225)

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Sub could be blown (fried voice coils). Was it new?

Oct 22, 2003 | 09:26 AM

Ne0h

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First off...

If you're not running the infrasonic filter on the 500/1, TURN IT ON!!! It will help to prevent the sub from bottoming out. Personally I set mine at 40hz and the crossover at around 95hz lbp. A crossover point of 25hz lbp will not get barely anything other than extreme excursion, which in this case is not a good thing for your sub. The slope should be fine. You should set the crossover way higher to around 80hz. If you haven't managed to fry the voice coils by running the sub that hard at that low a frequency, you should definitely hear results.

Also, if you're feeling ambitious, pull the sub out of the enclosure and measure it. Get the specs for the sub for airspace, and get some styrofoam peanuts and a measuring cup and measure it! The volume should be as close to spec as possible, and remember to exclude the space occupied by bracing or the driver.

Another thing that can cause a sub to rattle like that is having it in too small an enclosure...

My gut tells me your enclosure is probably fine and your amp settings are just off...

Hope that helps..