popping speakers

[e30mad]

hiya guys, first of all ive just joined the site so a big hello to all

i have been looking for a forum to discuss car audio and found this one..
i have a problem with my setup in my bmw, i have been running 3 amps for a few years now, 1 for subs, 1 for front components and 1 for the rear speakers and its been great until now.. i have just fitted a new headunit (alpine) and now i get a pop from all of the speakers when i power up! and also between traks when its quiet i can hear thudding from the subs. now im sure its not any speaker or amp as it worked fine before i fitted the headunit, it can rely let off a crack as i power up i have however fitted a switch to the amps so if i power the amps up after the headunit turns on its fine. (apart from the thdding..) but id rely like to get this sorted. i did have a read on the topics that came up as i went to post this but they are not quite the same as my problem. i have not yet earthed the chassis of the headunit, (doing that tomorro) but is there anything else i could learn about this issue?

thanks in advance guys.

dave.

[AKHeathen]

well, it's likely in the head unit delay. i would go through with the grounding, not only the head unit, but the whole system. did the old head have a problem/failure? what amps are you running? it is possible that you have a grounding problem, which could have damaged the rcas, as well, or even the factory head ground. while the amps are on and not playing, use a meter to to measure the dc voltage at the power terminals. place the black probe on the ground terminal and see what the voltage is with the red probe at the power (+) and remote. they should be the same. also, put the red on bare metal on the car chassis. you should not see any voltage. then compare the voltages to the battery terminal voltage.

[Perry Babin]

Unplug all but one amp at a time to see if one amp is causing it.

Also check the speaker wires to see if any are shorted to ground. Check this with a multimeter. Unplug the RCAs from the amp when you do it. If you find any that appear to be shorted to ground, disconnect them from the amp and check them again.

[e30mad]

the old headunit was in perfect running condition, the only reson i replaced it was due to the fact that it was a 8 year old sony, m600r i think it was, was a great headunit to look at but i wanted a newer one for more power and that freah/crisp sound, plus sub control etc etc. the alpine has deliverd all that i wish for. if i plug the sony back in its fine. the sony was never chassis earthed either, the amps are also quite old but reliable. ive always used a switchable live on the car itself to turn the amps on with the key/ignition, im not sure if the alpine has a delay live, if so that will cure the popping, ill have to take a look at the wireing while i earth the chassis.

[TheBaronGroog]

The thudding is normally a bad earth or issue with the RCA, double check the bass amp's earth and RCAs-will probably cure the trun on thump too.

[AKHeathen]

oh yah, i would wire the amps remote wire to the head unit remote turn-on output (blue wire) that is likely the cause of the turn-on thump.

[Mote]

Offtopic:
From your user name I assume that it is an e30 bmw? 325?

[e30mad]

yh mote is a e30 2.7i build, cabby.
just had a dig about with the wires, the diagrams show a blue/white wire as the remote turn on, but the wire wasnt there, insted i found a pink wire that did the same..
hooked it up and bingo! no more popping
i also earthed the case for good measure

thanks for the info guys

[Mote]

Just out of curiosity, what front speakers do you use and where? Seems to me that original location is not very good. I own a 1988 320i in which I someday would like to install a decent soundsystem.
You 325/327 owners are lucky, battery in the trunk, no need to run 5 meters of power cable.