mission 780se

[Bizzie]

The drive unit's that I bought off ebay were the new type replacements and are still working well on the end of a WAD KEL84.

[Slartibartfast]

Hi Cobblers,
Just to say that the replacements from Mission looked very similar to the old Keraform ones - just didn't look as mottled. Apparently they are aerogel instead. Just glad to have them up and running again to be honest - and glad my wife hadn't binned them for being broken!

[Cobblers]

That's fine, the drivers are the same, it's just the cones that are totally different to the failed Keraform. HD Aerogel like the previous speakers (which were a lot better anyway).

[pre65]

The same,but different.

[Cobblers]

Originally Posted by pre65

The same,but different.

I conceed not exactly the same, I expect (well hope) they were designed to work perfectly with the existing simple crossover.

Same motor system with same phase plug, plastic basket, magnets, etc, nigh on identical cone weight (if engineered properly) with same profile shouldn't upset the balance.

More to a driver than simply the cone.

[daveybm]

Just a line to say thanks to the members of this forum, I too have a pair of Mission 780se speakers that exibited exactly the same problems as reported here, thanks to a quick google I ended up here and found the answer before the speakers got binned. I ordered the driver units from Mission for £56 inc vat & delivery on the Tuesday and recieved them on the Thursday (Brilliant considering the Christmas post) fitted them up and hey presto we're back on the musical spectrum. Once again thanks to all.

Dave

[Grog]

as the fault's slightly intermittent, it's probably the flexible braid wire on the drive unit, which links the terminals to the voice coil, this has fabric and copper strands in it. usually the copper fractures (eventually) making an intermittant fault.
thats repairable by someone with a bit of experience.
i could take a look for you if you're not too far away?

[Robin128]

Originally Posted by Bizzie

I have a pair of Mission 780se that I let my daughter use with her Denon udm31 mini system and they have been ok for the last two years.
Suddenly they lost all the bass and all that can be heard is the treble with the base cutting in occasionaly then going off agian, at first I thought that the amp was to blame but it works ok with other speakers and the Missions are the same in my system.

I have had a look inside thinking that there was probably a wire come adrift somewhere but cannot find anything obvious.

I now don't know what to look for and I'm not sure if the problem is in the cross overs or the bass driver, how can I test the driver without causing anymore damage.

I think its really odd that both speakers are affected as I would expect a component failure to happen only to one speaker.

780's were built using adhesive that dissolved copper...your voice coils are melted.
I have 3 pairs of 780's used as surround speakers in DTS's.
Just replaced the woofers with monacor sph 100AL using clear unibond silicone sealant...screws will not fit. Connections are push fit and different sizes to avoid phasing issues.
I bought the woofers from musichaus thomann in Germany...good firm...currently got 4 more on back order.
Easy job.
Tweeters will sound scratchy when driven without woofers to play the mid range and bass.

Replacement woofers are cheap.