Problem with Mission 753 speaker

[Dunk_Smith]

Help,

I've had the 753's since new when they first were manufactured(late 80's) and love there sound. However one of them has developed a problem. 2 out of the 4 Low frequency(LF) speakers in one of the speakers are not producing any sound. I have dismantled and tested both LF speakers with a 9V battery to see if they still 'fire' and they do. I have swapped the whole speaker from left to right to make sure they was no problem with the speaker cable, there insn't. I've got my multi-meter out and tested for a circuit across all components on the speaker crossover unit and compared to the working speaker and everything matches. I've checked there is a circuit from the crossover to the LF speakers, all ok.

I've run out of ideas/thoughts. Any input/ideas as to what to try next would be greatly appreciated.

 

[Gazzip]

Have you tried swapping the drive units that don't fire with the two that do fire?

 

[Gazzip]

Also if you don't biwire then check the bi wire jumper plates on the terminal inputs are in place and making a connection.

 

[Dunk_Smith]

Gazzip,

Didn't see any point in swapping them due to the fact that when I plugged in the other 753 speaker all drivers were being driven(proves nothing wrong with speaker cable IMHO) and that the test of each of the individual 'not working' speakers with the 9V battery proved that they were fine(i.e. the driver cone flexed and was pushed out).

I was hoping someone would say, "oh it's probably the XXXXX component of the crossover, do this, check this, if it does or doesn't do this means it's faulty, change it". But then again i'm frustrated not being able to narrow down what's going on.

Thanks for your thoughts though.

 

[Dunk_Smith]

They are bi-wired.

 

[Gazzip]

Gazzip,

Didn't see any point in swapping them due to the fact that when I plugged in the other 753 speaker all drivers were being driven(proves nothing wrong with speaker cable IMHO) and that the test of each of the individual 'not working' speakers with the 9V battery proved that they were fine(i.e. the driver cone flexed and was pushed out).

I was hoping someone would say, "oh it's probably the XXXXX component of the crossover, do this, check this, if it does or doesn't do this means it's faulty, change it". But then again i'm frustrated not being able to narrow down what's going on.

Thanks for your thoughts though.

Yes but if you do physically swap the drivers over then you can catagorically narrow it down to the crossover. Your battery test doesn't really prove anything definitive other than current + magnet + coil = movement.

Not withstanding the above two drivers at the same time probably is a crossover issue so why not just replace the whole crossover? There is a reconditioned unit for sale on fleabay at the moment at £39.

 

[TrevC]

It could be a dry joint on the crossover or a dodgy crimp connection maybe. A cheap moving coil test meter used on the low ohms range will be a worthwhile investment.