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Author Topic: bottoming out sub? need help!  (Read 699 times)


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bottoming out sub? need help!
« on: July 19, 2019, 08:02:08 pm »

Now I need some serious help, I feel like I have tried everything and I cant figure out the problem.

The story:

I have a 12v portable PA system. I use a 200ah lifepo4 batterybank, a pioneer mono gmd9601(500w@4ohm) with 2 diy tham15 (15ps100) for subs and a gmd8604(300w@4ohm x2 bridge) for tops. I blew two drivers last summer bcs someone turned on the bass boost (50hz). They never recovered from that. I played around with amplifier gain on the mono amp afterwards, and toasted them. Kind of an experiment as much as an accident.

I bought two recone kits and a new driver and built a new box. The first reconed sub sounds nice in the new cab, but the second reconed sounds like its bottoming out. Not like a rub, more like a solid clank when I turn the volume a little bit up. I took it out of the cab, the clank is getting more pronounced, sound like a metallic rattle. I think for my self, maybe it could be the dust cap is off centre. So Im cutting of the dust cap, recentering it, rattle is still on board.

Here comes the weird part. I open the new 15ps100 . It says on driver it is tested before shipping. Mount it inside tham 15, and rattling/clank is here as well. I take it out of the box and try it open air, it rattles even more like a snake. I try my other amplifier, same sound. I put the brand new 15ps100 in the other cab, same sound. I go back to my first reconed sub, testing both amplifiers, and works like a charm.

Made a filter setting on minidsp, cut off at 38 and 110 hz. No improvement. Now I'm frustrated and getting creative. I go back to the driver with recentered dustcap, and try to find out if it is a misaligned voicecoil after reconing. I put on a clamp, and add force on frame until I hear rubbing sound, and release, and rubbing sound goes away. Try this again for 3 new angles, and I conclude it is not a rub problem, more like a bottoming out sound.

Now I'm out of ideas. The driver is rated for 700w rms and amp 500w, and the sound was there right at the beginning. I cannot remember this sound from before I blew them, but who knows. Maybe I wasn't so critical as I am now. But there is definetely something fishy going on.

Do drivers bottom out in free air always? Is this normal when pushed maybe 100 or 200 watts on music program? I have inspected amps with multimeter, no DC from amp terminal. Resistance on speaker terminals is perfect, so not blown driver.

I have an event coming up in a couple of days, and I did not expect so much hassle. I am getting quite anxious to say the least. Very new to diy pa, and feel like I have put on too big of a challenge. Now I am asking for help.



Mac Kerr

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« Reply #1 on: July 19, 2019, 09:02:43 pm »

Now I need some serious help, I feel like I have tried everything and I cant figure out the problem.

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« Reply #1 on: July 19, 2019, 09:02:43 pm »

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