subwoofer / car stereo problem

[chaotick]

I had my subwoofer and amp wired up and working just fine for months then, just recently, took out the subs to lay my seats down and move some drums.

I have disconnected and taken my subs out before with no problem but this time I put them back in and it's just a constant *thump* *thump* *thump* that won't relent and does not follow whatever is on the stereo--just a constant bump.

Anyone know what is wrong with it based on that limited explanation?

If it helps here are the amp and sub:
Audiobahn A8002V Amp
MTX Jackhammer 212

I don't know a lot about car audio but I know that the guy that installed it wired it so that the ohmage matches.

Thanks in advance!

[hbarcat]

The thumping is a repeating power surge sent down the speaker wires. The most likely culprit is a wiring problem that presumably happened when you reinstalled the speakers.

Check the wiring against the known correct wiring diagram (if you have it) and see that they match up. Check for shorts, touching wires or bad contacts.

Some more information would be helpful. How do you usually remove the speakers? I assume this is a passive enclosure that has some kind of quick disconnect for the speaker leads. I can't tell for sure from the link because it doesn't include any details.

Also where is the power amp located? Check the power lead and the ground to the amp for bad connections.


If I'm reading your post correctly, the stereo is playing music fine through the main speakers but the thumping is ONLY coming from the subs?

[popinfresh]

Maybe they're 'fully sick'

(might be an Aussie joke)

[chaotick]

Originally Posted by hbarcat

The thumping is a repeating power surge sent down the speaker wires. The most likely culprit is a wiring problem that presumably happened when you reinstalled the speakers.

Check the wiring against the known correct wiring diagram (if you have it) and see that they match up. Check for shorts, touching wires or bad contacts.

Some more information would be helpful. How do you usually remove the speakers? I assume this is a passive enclosure that has some kind of quick disconnect for the speaker leads. I can't tell for sure from the link because it doesn't include any details.

Also where is the power amp located? Check the power lead and the ground to the amp for bad connections.


If I'm reading your post correctly, the stereo is playing music fine through the main speakers but the thumping is ONLY coming from the subs?

I made sure that I connected pos/neg right and same result. You are correct that it has a quick disconnect on the side of the sub box.

The amp is located on the seat directly behind the sub. I'll try to check the ground and power lead.

Yes, you are correct, the other speakers in the car are working as normal but no sound, ONLY the constant thumping, is coming from the subs.

[chaotick]

Here are some pictures if that helps.









I haven't had time to check the connections from the amp to the ground and battery--I'm not exactly sure how and I'm at work. Halp!

[hbarcat]

First make sure the settings on the amp are correct and you didn't accidentally turn the input trim up all the way or you have it set to some weird bridge mode or something. It's a long shot, but this only takes a second to check.

The symptom you describe is a bad connection about 80% of the time. Just disconnect the speaker leads at the box and inspect them and then reconnect them making sure to take your time and see they make good solid contact. Do the same with the power, ground, remote and signal leads into the amp and speaker leads out. Check the power and ground leads where they connect to your power source and chassis ground.

Power the unit on again and see if the problem is solved. If it isn't, you can try to isolate the problem. To check if the problem is a bad connection inside the speaker box, try to substitute another pair of speakers in their place (this assumes you have some to try, of course). Or you can remove the speakers themselves from the box and directly check the wiring inside the box to see if everything is making good contact.

If none of this solves the problem, you're very likely not going to be able to solve it over the internet and you will probably need to take it to someone with experience. It's very possible, that person could easily trace down the problem to something simple. Or not.

Let us know how it goes.

[hbarcat]

Looking again at your pictures, it seems that the amp is setup to run in bridged mode (left and right signal into the amp and mono sum out) Is this correct?

If so, find out if the amp is capable of supporting a 2 ohm load in bridged mode. If it isn't, this may be a clue to your problem, because your speaker box is 2 ohms.

*EDIT*
I just checked the specs for your amp.

Audiobahn A8002V Amp
* 2-channel car amplifier
* 200 watts RMS x 2 at 4 ohms (400 watts RMS x 2 at 2 ohms)
* 800 watts RMS x 1 bridged output at 4 ohms (4-ohm stable in bridged mode)
* Variable low- and high-pass filters (low-pass 50-120 Hz, high-pass 50-750 Hz, 18 dB/octave)
* Bass boost (18 dB at 45 Hz)
* Variable subsonic filter (20-50 Hz)
* Stereo or bridged mono output
* Cooling fan with air intake
* Built-in digital volt meter
* MOSFET power supply
* Tri-way capable (Tri-Way Crossover required)
* Preamp- and speaker-level inputs
* Preamp outputs
* Fuse rating: 30A x 2
* 11-1/8"W x 2-3/8"H x 13-3/8"D


Your amp is not designed to run at a load as low as 2 ohms. If the amp has circuit protection, it may very well be shutting down in order to protect itself. In which case it will power back up, sense a low load, power off, power back up. . . . continuously, thus generating the symptoms you describe.

This may or may not be the problem but it's a strong possibility.

[chaotick]

Thank you very much, hbarcat, I shall give your suggestions a try.

As for the 2 ohm problem, when I had it installed, the guy told me that he re-wired the box for 4 ohm so... i hope he did. lol

Like I mentioned, it had been working fine for several months and I've even taken them out and put them back in my car before with no ill effects.

Thanks for your help, I will certainly be checking all of this when I get a free day from work / band / etc.

[hbarcat]

Originally Posted by chaotick

As for the 2 ohm problem, when I had it installed, the guy told me that he re-wired the box for 4 ohm so...

The box says "2 ohms" on it but he said he rewired it for 4 ohms. . . . That's very interesting.


Make sure you post back here - I'm curious to find out what the problem is (once it's corrected, of course. )

[MJ5150]

In the second picture, that shows the mounting plate and the wires.

What is the mounting plate made of? Is that bare wire hanging out on the ends?

-Mike

[hbarcat]

Originally Posted by MJ5150

In the second picture, that shows the mounting plate and the wires.

What is the mounting plate made of? Is that bare wire hanging out on the ends?

-Mike

Hmmm. . . good eye.




chaotick, if that plate is made of metal you can probably solve your problem in about 3 seconds.

[hbarcat]

So, ever get this problem solved?