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Old 14th December 2006, 02:12 AM   #1
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Default need help with my 12' memphis mojo m3

So i was driving and i have a Memphis Mojo M3 12 inch subwoofer.I was driving the other day and hit a huge pot hole, and as soon as i hit it, my sub started to make this really low vibration sound. It wasnt just when the music was on either, i could turn the volume all the way down, and i could still here this vibration. I dont believe that it is the amp, because it is a brand new amp that is more than powerful enough for this sub, and is only about a week old. After a couple of days, the sub doesnt hit at all, and there is no more vibration noise.

Anyone know what this could be, or how i can fix this? Thanks
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Old 14th December 2006, 03:05 AM   #2
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it might be the RCA cable connection
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Old 14th December 2006, 06:46 AM   #3
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i heard that it might be the tinsel lead from the coils... what abotu that?
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Old 14th December 2006, 06:56 PM   #4
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Disconnect the speaker from the amp and measure the resistance across the speaker wires. What is the resistance? What is the rated impedance of the speaker's voice coil(s). If it's a DVC woofer, how are the coils wired (series/parallel)?

There is no bump that can compare to the stress that the tinsel leads see under normal operation. Also, if the leads break, the speaker quits or is intermittant. The noise you described sounds like an amp problem or possibly a signal problem (as was previously suggested).
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Old 21st December 2006, 12:41 PM   #5
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ok so i went out and bought new RCA's and i am still hearing nothing. i did notice that on my amp, the red light is lighting up instead of the green one. so i tested another amp, and it did the same... thanks for all your help guys, hopefully i can get this thing hitting pretty soon!!!
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Old 22nd December 2006, 01:17 AM   #6
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You need to check the DC resistance of the voice coil. Disconnect all wires from the speaker. Set the meter to ohms and touch the leads across the terminals. It should read the same as the rated impedance (15% give or take). If you read near zero ohms, the woofer has a shorted voice coil.

Although it's unlikely, the pothole could have caused the magnet to shift, shorting the coil. If this has happened, the woofer will have to be repaired/replaced.

Does the con still move freely when you push on it?

A shorted voice coil will cause an amp to go into protect mode.

If the amp goes into protect with no speaker wires connected (disconnect the wires from the speaker-terminals-of-the-amplifier), the amp is in need of repair.
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Old 25th December 2006, 08:54 AM   #7
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If you replaced the RCA's and the amp I would say take out the sub and look at the wires that go from the terminal (if you have one) to the sub. It sounds like the pot hole knocked one loose and it eventually came off and made contact with the other one ( negative wire to positive wire). That would cause the amps to go into protect mode. A pot hole should have done NO damage to your sub. If I could then the sound pressure from it playing would have killed it. I hope it helps.
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