sub issues

2001 BMw 325ci

stock radio, Keenwood  7201 amp, fos cap,

Here is my issue, the BMW has a stock woofer behind the rear seat, I disconnected and removed the woofer, used the wireing for the lines in on the amp. (1) bridged the amp to 460 rms @ 4ohms, gain set @ 1, wired into a 2.00cu. ported box, port length @10.25 @ 35 hz, kicker 12L7 2ohm DVC wired in series for a 4 ohm load, my sub is now toast. double checked wireing and was to specs. previous I had a memphis that is also toast, and a JL, My question is could the stock wireing cause these subs to smoke up? Help.

elimitate you gain setting by putting it to minimal, as well as your crossover. Upgrade all wiring to 4 guage, for both power and ground. Your ground should be less than 3 feet. After this is all taken care of, install new woofer and adjust crossover and gain according to you ear, but be careful no to exceed their specs.

uthinkuknoaudio wrote:

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elimitate you gain setting by putting it to minimal, as well as your crossover. Upgrade all wiring to 4 guage, for both power and ground. Your ground should be less than 3 feet. After this is all taken care of, install new woofer and adjust crossover and gain according to you ear, but be careful no to exceed their specs.

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Uh,"adjust crossover and gain according to ear"?  This is not the best advice without explaining further.  Start HERE to learn how to set gain.  I highly recomend reading all that the Basic Car Audio site has to offer.

When you say your sub is toast, what exactly do you mean?  What is the make/model of your amp?

And how did you determine that "gain set at 1" is proper?  I bet this is the problem: your gain is incorrect and the amp is clipping like crazy.  I suggest you turn that bass boost off and set your gain properly, especially since you are using a high-level input to the amp driven by the factory sub amp (if I understand your setup correctly.)  Do you need instructions on how to do this?

Also, does your amp have a sub-sonic filter?  Where's it set?  You have a ported enclosure tuned to 35Hz; you will need to high-pass that at about 30-35Hz to protect the woofer from over-excursion.  This might also be part of the problem.

thanks that would be of great help. I have tried to locate a sub-sonic filter and they looked at me crossed eyed. I am only using the crossover built into the amp. How do I identify "clipping".

That amp does not have a subsonic filter, and you need one for your Solobaric.  Even though you are running at less than max power, at about 26Hz in your vented system the loudspeaker will be completely unloaded and can be driven to its mechanical limits.  This makes it easy to "fry."  I recomend installaing a stand-alone subsonic filter.  Harrison Labs makes one I've used in the past and set to 30Hz will protect your woofer.

Clipping is what happens when an amplifier is driven too hard and involves compressing the peaks of the output sine wave (it shows up as a near-square wave on an ascilloscope, and is called clipping since it appears that the sine waves have been clipped off.)  It can be detected by ear as a "shrillness" or "distortion" of a pure tone. 

Here's what I suggest for your setup.  You will need 1) hearing protection, and 2) a CD with a test tone on it at about 60 Hz.  Also, I suggest setting the low-pass crossover on your amp up to about 80 Hz.

First, turn the bass boost off (and leave it off) and turn the gain on your amp all the way down (counter clockwise.)  Next, set your head unit volume down and play the test tone.  Wearing your hearing protection, slowly turn the head unit volume up and listen to your sub output until you can detect that the tone seems to have changed (it should seem to get a little "sharp" or shift upward in frequency.)  This is being caused by clipping in your head unit or your factory sub amp.  Turn the volume down until the tone returns to normal.  NOTE THIS SETTING.  This is the HIGHEST you can ever turn your head unit volume without introducing clipping.  Next, leaving the head unit playing the tone at the just-below-clipping point, slowly increase the gain on your sub amp until you again hear the tone change, then back it off.  Leave the gain set here.  You have just matched the input sensitivity of your amp to the maximum non-clipped signal from your system.  Turn the volume down and remove the test CD (and your ear plugs) and you shuld be good to go.  But get that subsonic-filter if you want to keep that woofer for a while.

g8trhtr wrote:

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the amp is bridged to 460 @ 4ohms, gain set @ 1, the 12db boost is on, the sub is a single kicker 12l7 dvc, wireing is in series,

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Most people don't realize the significant power that a bass boost requires.  I have seen many people do the same thing as you, and have the same consequences.  Their Sub(s) ended up blown.