PeachParts Mercedes-Benz Forum - View Single Post - Engine whine from rear speakers....HELP!!

G-Benz · #5 10-15-2001, 05:27 PM

Newer cars bring about interesting challenges with regards to electronics...one of them is the electromagnetic radiation emitted by all of the vehicle components.

You've already determined that the amp is the source of the "whine"...are you sure? Disconnect the head unit from the amp and see if the noise is still there...if it goes away, the problem is the head unit and not the amp.

I read that your amp is mounted in the trunk. Are there any MB electrical modules in close proximity? You may need to "shield" the unit, so that the radiated emissions are blocked. Keep all power cable runs away from large factory wiring harnesses.

Short ground wires is a good tip. The best method however, is to have all audio components share the same ground point to prevent "ground loops", a very common noise source.

I assume that your power lead harnesses from the amps are not laying parallel with speaker cables throughout the length of the cable runs. If they must meet at some point, right angles are best. By the same token, keep the speaker cables AWAY from any of the factory harnesses as well, running them at right angles as well.

Noise suppressors are fine, but should only be a last resort (kinda like aux fan switch bypass circuits when you can't figure out how to keep your engine temps down).

As far as your load problem, you are correct in determining that the ohm load is putting your amp in "protection mode". The other possible problem is that the power lead to the amp is not large enough. If too small, the amp cannot draw sufficient current, so it shuts down. In extreme conditions, a fire could result!

If your power leads are fairly warm after the amps shut down, then you need to bump up to thicker wire, which dissipates heat more effectively. For a 400-watt amp, I wouldn't get anything less than 4-gauge wiring...thick and hard to bend, but safe.

The ground wire should be about as robust (6 or 8-gauge). It's no secret that sound-off competitors use zero-gauge wiring for all of their power supplies (zero-gauge is what arc welding equipment comes with)!

I am also assuming that your power lead is fused?

The OEM "deluxe" system does indeed have power amps, and you should be running line level, not speaker level signals...that is probably why your amps are shutting down...if the full output was capable, your speakers would be laying smoldering on your lap.

You should bypass the internal (speaker) amps and connect the speaker leads directly to the speaker terminals. That way, the amp sees a "balanced" load, and isn't trying to send 4-ohms to one set, and some undetermined load to another.

Hope this helps...