Help needed with noisy tweeters

[millo777]

I've been trying to cure a problem my W124 has with annoyingly noisy tweeters.

It's a kind of hissing/crackling sound that is constantly there. Imagine listening to a badly tuned radio and thats the noise I get, but only from the tweeters. Not a sibilance issue, as it's present at all times.

The system in the car consists of a Blaupunkt Travel Pilot E2 head unit connected to 2 blaupunkt amps in the cargo area. One amp drives the speakers int he rear doors and a sub mounted in the spare wheel.

The second amp has two outputs, each connected to a 3 way crossover which are then connected to a sub in the front door, a co-ax speaker in the dash and a tweeter on the mirror trim panel.

There are no problems with the co-ax speakers and subs powered from the same amp.

I ordered a new set of Clarion SRE211H tweeters as I assumed the existing ones had blown. This didn't make any difference at all, even using the supplied clarion crossover in-line.

I then connected one of the new tweeters, using the supplied crossovers directly to the amp, same result....hissing and crackle.

Connected the tweeter directly to the other amp, with exactly the same results.

Now I'm confused. The amps drive other speakers with no issues, so doesn't appear to be problem, and the tweeters are brand new.

In case it makes any difference, there is very faint alternator noise picked up by the system but only noticeable when the system is muted. all the earths check out o.k.

What could the problem be?

 

[steveskeggy]

Have you tried wiring the tweeters directly to the head unit without the amps (using the crossover supplied) they should have an impedance of 8 ohms, just check that in the specs, if they are then running the head with just those connected should be OK.
If the noise is still there then you can rule out the amps.
Then try the tweeters on another system to rule those out, if they work OK then is a head fault, if not then the tweeters are blown and you should consider trying to find a pair that will handle higher power.
If its gone, then put it all back together again, then try running a wire from the chassis of the head unit to the chassis of both of the amps at the same time and each at a time.
If its still the same, then try disconnecting all of the negative wires between the head and the amps (dont do this with the system on).
If neither of these work, but the tweeters were OK when connected directly to the head, then re-connect them to the head, and reconnect the amps to the head, so you have the tweeters running off the head unit and the rest of the system running through the amps.
You may find that this sounds OK as it is, if you are happy with the sound then build it all back up.

 

[millo777]

Thanks Steve, that was my next plan. I'll buy an iso socket and some pins tomorrow and try hooking them up to the speaker outs on the head unit and see how I get on.

I had intended to try them on my W140 but the Bose system in that runs 2ohm speakers I believe which may give a strange result, and the door cards are a major pita to remove anyway. I'll assume they're o.k for now as they're brand new and concentrate on the head unit and amps.