Speaker Problem

[Hedgerley]

I have been running a pair of Mission 733s for around 15 years now. Despite numerous system upgrades and various surround sound set-ups etc. I have never felt the need to replace these excellent floor standers. I currently have an Arcam 280 surround processor/amp and have no plans to replace it.

Anyhow, a couple of weeks ago the sound from the speakers began to 'weaken' and then all of a sudden they sound like a badly tuned, very tinny radio playing in the next room. No matter what I do to the set-up and volume I have lost all stereo imaging, for both CD's and L/R Dolby 5.1 effects. The fact they have not packed up all together is a bit mystifying.

Having checked the amp and all connections it is definitely the speakers - this morning I hooked up my excellent B&W centre speaker to the left and then the right speaker cables and all was fine, reminding me just how good the amp is and how much I like the Arcam sound.

No-one in the household will admit to over driving them - I play my music very loud and they have never peaked or distorted in any way so I am pretty sure they can handle the amp even when its wound up very high. So I don't think they are 'blown' as such.

So, before I open up the speakers can anyone out there enlighten me?

[Frances The Mute]

Assuming all connections are solid, try the push test first.

Lightly push each drive unit in at opposing sides (e.g. 9 and 3 o'clock) to simulate movement. Repeat this on each drive unit.
They should move freely with light resistance from the rubber driver diaphragm. If you notice any noise (graunching) or note heavy resistance, then the drive units have been over driven and ned replacing.

Outside of that, it's likely that the internal crossovers are at fault.

[timbo999]

Almost certainly the cross overs have been blown - not just power can blow these - if someone used a crappy source (a dodgy mpg file on a player plugged into the amp for example) this can happen at quite low power levels. If you put them on and put them on and listen close to the units themselves you'll probably find just the HF units are working.

Good thing is that Mission (used to at least! - when I had some Missions a good few years ago!) have a great repair service.

[Crackie]

Frances The Mute said:

Assuming all connections are solid, try the push test first.

Lightly push each drive unit in at opposing sides (e.g. 9 and 3 o'clock) to simulate movement. Repeat this on each drive unit.
They should move freely with light resistance from the rubber driver diaphragm. If you notice any noise (graunching) or note heavy resistance, then the drive units have been over driven and ned replacing.

Outside of that, it's likely that the internal crossovers are at fault.

Checking for rubbing voicecoils by pushing makes sense but I would push very lightly in the centre of the bass/mid driver's dustap rather than 9 and 3 o'clock. The 73 series PP cones didn't have good resistance to UV and they are likely to be extremeley fragile by now and pushing directly on the cones could kill them; from the 'tinny' description of the sound the bass/mids may already have let go. If it does turn out to be the cones, the original cones aren't available anymore but you can get an equivalent here http://www.technosound.co.uk/eShop/ssMission.html

Hopefully it is the crossovers as said above, no 'special' components used in a 733.

Edited by Crackie on Sunday 16th December 19:23

[Hedgerley]

Thanks guys. Cones are fine, I'm pretty certain the crossovers have given up. I've had the 733s for over 15 years and they have been 'on' for probably 14 of them! They are obviously tired but as they continued to produce a sweet sound, even as I upgraded my system, I could never justify (to SWMBO) replacing them. Now I can so its probably a pair of B&Ws (which I've already auditioned several times with Arcam gear) to replace them in the New Year.

Thanks again.