speaker problems post bm54 upgrade by offyoutoddle

I've recently fitted a bm54 off ebay. I thought things were ok, but today I added in a new adaptor to fit a bt ulf module, and after that I found my speakers were behaving oddly.

I think my rear speakers are not working. using the fader to bias totally to the rear, there is hardly any sound unless I turn it up very high, and it is muffled and distorted on one side.

I also noticed the front left channel dropped in and out a few times whilst driving today.

I have a bm54 flat to 17 pin adaptor fitted, and I've experimented with the 10-12pin adaptor to make sure I have it the right way round. There appears to be only 2 ways to fit it, and one way I get no cd sound, so I have it set now as it should be i think.

I've put it all back as it was , and it is the same, so i think it is me noticing something for the first time.

bm54's are notorious for channel faults I know, but how do i find out if I have a problem with my plugs, a problem with speakers or a problem with my bm54? can anyone suggest an approach?

thanks in advance

Posted 15 Sep 2015, 22:10 #1 

User avatar
You could try refitting your old radio to test if its speakers but I think this is unlikely
If you don't have a telephone connected, for the front left channel make sure that you don't have anything fitted to the telephone mute pin Pin 4 on the old connector Pin 10 on the new connector.
I don't know how to check the BM54 other than swapping it with a known working unit or swapping over the front and rear speaker connections at the connector pins and see if the issue moves to the front speakers

Posted 16 Sep 2015, 13:08 #2 

thanks for the suggestions. You are right, fitting the old radio back in to test is a non starter sadly , firstly because I don't have it, but also because I can't get the damn round pin to flat pin adaptor free!

I have the bluetooth ulf module in so I'm not sure what pin 4 will be set up as with the loom adaptor wiring I now have.I have read . Front left channel seems to behave a bit better at the moment - no issues today at all for example. I believe i've found a method I will check out tomorrow - The speakers can be verified by measuring the resistance across the speaker + and - pins for each channel in the flat pin adaptor. Should be 4 ohms so I will try that.

Posted 16 Sep 2015, 20:34 #3 

well here is a turn up - it was both.

the bm54 had a blown rear channel , and Baris' stage 2 upgrade fixed that. The rear left side works, but only the tweeter - the woofer is blown. Ah well. temporary fix is a 2nd hand speaker off ebay. long term is thinking about speaker upgrades all round - the stage 2 is wasted on these speakers i guess.

Posted 18 Sep 2015, 19:26 #4 

User avatar
Do you have the Harmon Kardon system and speakers?
If not the speakers are a straightforward upgrade others non oem speakers will mean making mounting brackets etc
You can retrofit the full HK system including the boot mounted subwoofer and amp but this will mean even more wiring mods

Posted 19 Sep 2015, 09:31 #5 

no i don't have HK setup - never really considered it as realistic for me tbh, as it is a real job and finding all the bits complete is not easy - rarely seen a full setup with the loom and everything. Not even sure what they are worth so I'm sure i'd get ripped off, and I'd need them fitted as I wouldn't be up to the job. For now once the 2nd hand speaker is in, which will be a straight swap - they will have to do for a little while, as I have a longer to do list than starting on the hk system.

Posted 19 Sep 2015, 19:56 #6