Car Audio - Help me diagnose this problem...

[Ticky]

Hi all,

I need some help diagnosing a problem with my car's audio system.

Equipments at Issue

I have a MMats P2.5 10" subwoofer installed in my car's trunk (projecting through the rear seat's armrest). The subwoofer is powered solely by a Prism EX-1000.2 power amp.

This subwoofer system was recently installed (~1 month ago) to augment the rest of my car audio system. The rest of my system may be referred to below.

The problem

As of last week, I sometimes hear cracking noises from my subwoofer. This happens even at low volume and regardless of the source (i.e., CD, FM, I-pod).

However, the cracking noise does not manifest all the time. It only happens momentarily. Sometimes, it will occur upon starting the car and turning on the stereo. At other times, it occurs while I'm driving and listening to my stereo.

The cracking noise is akin to the sound that you might hear from a woofer that has been driven beyond its capacity. A kind of breaking sound when the bass note hits.

I don't listen to my speakers very loud. I like a balanced sound and have my sytem on "tone defeat." (so, no rumbling bass shaking stuff.) So, I doubt that I've damaged the subwoofer through user abuse.

I brought the car to the audio shop that installed my stereo. However - as this things always happens - they could not find any faults because the subwoofer behaved fine that day. (Still, kudos to the sales person who believed my story and told me to go back to store if the problem becomes more severe or is reoccuring.)

The cause?

The folks at the car audio store informed me that it might be possible that my battery may not be fully charged up when I start my car in the morning, that that could lead to the cracking noise when I turn on the stereo first thing after starting my car.

However, since then I've experienced these symptoms even while driving - in the middle of the day after starting my car a few times - I'm not sure if their hypothesis is correct.

I am guessing some damage to the voice coil or perhaps a fuse problem.

Any comments? I'll greatly appreciate them.

Thanks in advance.


Equipments:

Front: Alpine CDA9887 (Single disc CD, receiver and I-pod connector)

Amps: Cerwin Vega XL300.4 (front & rear speakers), Prism Ex-1000.2 (subwoofer)

Speakers: MMats Pro 5.0 (2-way front), MMats Pro65 (coax. rear)

Sub: Prism Bass box 8" (self powered), MMats P2.5 10"

Cables: Phoenix Gold (speakers), Digital Research (battery), Digital Research & Phoenix Gold (IC)

Fuse: EFX fuse box and fuse (Prism amp), Phoenix Gold 80A (Cerwin amp).

Filter: Top - X Filter.

Vehicle: BMW E46 Series 3.

[stevenkelby]

Sounds like a loose connection somewhere, check all the terminals are tight , right from both battery terminals, earth straps, RCAs, speaker terminals etc.

Otherwise, maybe some component is damaged, try a different amp, sub, cables etc one at a time.

Could be a cable chaffing somewhere it rubs the body, through the firewall etc.

[krc2]

i'd second the loose connection.
I dont think its a problem with your gear at all
btw nice choice on Mmats I used to love those

[Ticky]

Thanks for the comments.

Just a few for pointers in case this might help with the diagnostics:

- Whenever the cracking sounds occurs, if I turn off the stereo immediately, the subwoofer emits a popping sound. This happens even if I turn the volume down to zero.

I might have to take the car back to the shop and have them run through the connectors.... Hopefully, that doesn't require dissembling the interiors like the time the install the system.

I sort of shuddered when I saw them nearly reduced the interior to its skeletal hull during installation. You kinda wonder if they can ever put everything back together correctly....

[stevenkelby]

I'm no expert and it was a while ago, but I used to install competition car audio for a living. In your case I would have started replacing things one at a time. By this I mean, for example, running another RCA cable between components through the car, over the seats and carpet, with as little work as possible, just to to try a different cable. Not removing the old one or installing a new one, just plugging a new one in and trying to replicate the problem.

Earth straps - battery to chassis and amp to chassis

Power feed from battery (straight out the bonnet, in through the window).

RCA's

Sub (swap for another one in a box, just sit it in the boot.)

Amp (easy for a shop, they will have something they can sit there and hook up to test if the noise goes away.

Source

Etc, etc.

I hate to guess without seeing and hearing something but I suspect a strand of wire shorting the signal intermittently, or a dud "component" somewhere.

These things can be a right btcih to diagnose. Or they can be very simple.Good luck!

[infinitesymphony]

Originally Posted by Ticky

- Whenever the cracking sounds occurs, if I turn off the stereo immediately, the subwoofer emits a popping sound. This happens even if I turn the volume down to zero.

I don't know anything about car audio or much about subwoofers, but if there is a pop when the audio stops, there could be a DC offset problem somewhere in the chain. Possibly a power problem, or a problem with DC offset protection circuitry in one of the devices, especially since the pop still occurs when the volume has already been turned down.

That's my guess, anyway...

[Ticky]

Every bit of info is a great help.

Thanks guys.