Monitor Audio B4 Blown Tweeters

[MrPotatoEd81]

Hello, This is my first post, any help would be appreciated.

I have recently dug out two pairs of Monitor Audio Bronze B4s that where condemend to the loft after the children turned the volume to full on the amp (sony STR-DB940) and I unkowingly turned them on blowing the tweeters. This happend to the first pair which I replaced with a second set of new speakers after discovering the cost of replacment parts from MA (not knowing at the time the extent of the damage) would be dearer then a new set of E-bay.

I recently decided to look at repairing them and got the multi-meter out and tested for continuity between terminals on each tweeter, mid and bass units. All except one tweeter had open circuits but the mid and bass all had closed circuits.

So assuming the only blown parts where the three tweeters, I checked the impeadence given on each 'good' unit with the meter and the readings where close (with in 0.8ohms) so concluded that all was well with these units and should proceed with buying the replacment tweeters at a cost of £37 each.

The question being, does any one know if the tests I have done are conclusive that theses parts are working. When used the bass sounds o.k but with out tweeters every thing else sounds muffled.

Any help would be usefull before I spend any ££££

 

[camcroft]

Give Monitor Audio a call and ask to speak to someone technical and then explain what happened and what do thy think.I rang tham about something and they were really helpful drop the + 44 in the telephone number and add a 0 before the number.Hope this helps.

http://www.monitoraudio.co.uk/support/contact-form/

 

[eggontoast]

I recently decided to look at repairing them and got the multi-meter out and tested for continuity between terminals on each tweeter, mid and bass units. All except one tweeter had open circuits but the mid and bass all had closed circuits.

I assume that you made the measurements with the drivers disconnected from the crossover ?

The question being, does any one know if the tests I have done are conclusive that theses parts are working. When used the bass sounds o.k but with out tweeters every thing else sounds muffled.

Not conclusive no as the coils on the bass and mid range drivers are unlikely to vaporise like the tweeter coils. What can happen is that the varnish on the coils can heat up and become rough, it then rubs on the magnet. But this usually takes a while for this to happen though, I assume it was only a short burst of music while you messed your pants and frantically reached for the volume knob. Anyway you can check this by gently pushing the driver in and out, you will be able to feel and hear any rubbing.

But if you have one working tweeter what I would do is fit it in turn into each speaker and run some music through it at a reasonable volume and listen for any erroneous noises from the bass and mid drivers. This would be the best test. It would also be advisable to buy a full set of four tweeters.

 

[MrPotatoEd81]

Cheers for your replies, It was some what stupid not to think of swapping the tweeter between speakers and shall try and see.

eggontoast, I did test each unit disconected from the cross overs, and the amp was on for a matter of seconds. I didn't mention that this happend to both pairs of speakers at different times.

So all though there is a circuit in the bass and mid range drivers they may still be damaged. I suppose only the ear will be able to tell?

 

[eggontoast]

I would be very surprised if they had been damaged in such a short space of abuse.

Like I said just stick the good tweeter in each speaker (because as you have already discovered, speakers sound terrible without a tweeter) and run them fairly loud, blown bass drivers make 'farty' noises and a blown midrange will just sound schite and unclear. I would imagine they will be fine.