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Discussion Starter · #1 · (Edited)
I have 2 sub's and an amp...I need to make sure that I don't blow something up. How in the hell do I hook them up? (Series, Parallel or whatever)

SUBS
JL - 12W0 DVC
Nominal Impedance - 8ohms
Power Handling (Continuous) - 125W

AMP
MTX4250D
125x1 into a 4ohm load
250x1 into a 2ohm load
 

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Rogue may have a different answer (and if he does, I'd defer to him), but it seems to me you have the wrong amp and subs. Running these in series will give you an effective 16 ohm load - and wired in parallel they will assume a 4 ohm load. Either way, your amp is unable to fully drive these configurations and you will likely send them a clipped signal (especially in the low end of the spectrum) - and that is NOT a good thing.
I like the subs. I'd look to get an amp (you choose) that can provide a "real" 500W stable at 4 ohms (I'd go with a mono-block or "bridged" amp configuration).
 

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jhelmuth said:
Rogue may have a different answer (and if he does, I'd defer to him), but it seems to me you have the wrong amp and subs. Running these in series will give you an effective 16 ohm load - and wired in parallel they will assume a 4 ohm load. Either way, your amp is unable to fully drive these configurations and you will likely send them a clipped signal (especially in the low end of the spectrum) - and that is NOT a good thing.
I like the subs. I'd look to get an amp (you choose) that can provide a "real" 500W stable at 4 ohms (I'd go with a mono-block or "bridged" amp configuration).
The only problem I have with your advice is that the subs only hold 125 rms and you are suggesting 500 watts rms.
I think 250-300 rms would be sufficient as these subs aren't very strong and don't stay linear under duress.
 

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wesexcellence said:
The only problem I have with your advice is that the subs only hold 125 rms and you are suggesting 500 watts rms.
I think 250-300 rms would be sufficient as these subs aren't very strong and don't stay linear under duress.

OK. But I'll give you my reasoning and agree that you might get away with a true 250-300w rms amp (depending on your listening levels and the driver efficency).

If we wire a pair of drivers in parallel the nominal power required doubles while the load is halved. I this example that will give us 2 12" JL subs as a 4 ohm load and a continuous 250W capability.
The 250w can either be met as a clipped or unclipped signal. My rule-of-thumb is to 2x the rated amp power to provide a significant overhead that will allow clean power (even at peaks) without the distortion that clipping brings - along with the damage clipping can do to them. It may be overkill in most peoples minds, but I think most reasonable people will not abuse that power, where they will tax an underpowered amp by "cranking it all the way" without realizing the damage they are doing.

Just my opinion...

PS - It sounds like you have intimate knowledge with these JL subs. And so I do want to defer to your experience... 250-300w might make sense. I didn't understand what you meant by "these subs...don't stay linear under duress". If you wouldn't mind elaborating on that a bit more, I'd like to understand what that means.
 

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jhelmuth said:
.

I didn't understand what you meant by "these subs...don't stay linear under duress". If you wouldn't mind elaborating on that a bit more, I'd like to understand what that means.
The voice-coil is attached to the spider and obviously the cone. The voice coil moves back and forth around the pole. As the speaker comes under load the frame needs to hold the voice coil "linear" as the cone moves. Since this particular sub uses a stamped-basket instead of a cast, it tends to flex at reasonably high volume. As the frame flexes the voice-coil begins to have difficulty staying in the center of the travel. Hence, a burnt coil which becomes "burnt" as it rubs the center pole.
The better subs use a larger coil and a cast basket to insure greater lineararity under higher demands.
 

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wesexcellence said:
The voice-coil is attached to the spider and obviously the cone. The voice coil moves back and forth around the pole. As the speaker comes under load the frame needs to hold the voice coil "linear" as the cone moves. Since this particular sub uses a stamped-basket instead of a cast, it tends to flex at reasonably high volume. As the frame flexes the voice-coil begins to have difficulty staying in the center of the travel. Hence, a burnt coil which becomes "burnt" as it rubs the center pole.
The better subs use a larger coil and a cast basket to insure greater lineararity under higher demands.
Thanks wes for the explaination. I've had pretty high regard for JL products and am surprised that they make a sub with a stamped basket (would never have guess that they'd go cheap on their products). I do agree with your comments now. Of course... this would happen regardless of the power amp size (250w vs 500w) assuming that either way the volume is cranked up to the same high level.
 

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Discussion Starter · #7 ·
Thank you all for your input. I think I will be replacing the amp and the subs. They are pretty old, I might go with a stealth box for the Grand Cherokee.
 
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