Mission 770S - rubbish or repairable?

Hi All,
My first post so please be kind.

Have wanted a pair of Mission 770 for a long time I picked up a pair of 770S's for the sum on £33. I was aware that the woodwork will need some TLC but I'm a liitle concerned regarding wiring and speakers fitted. It does seem that the orginal drivers were replaced long ago. Each speaker is fitted with Vifa M21WJ-09-08 and I beleive that the tweeters are SEAS(?) 25in H377. I cant certain but I have a feeling that the crossover circuitry (can anyone help here as i dont have a circuit diagram for this) has been rewired(?).

I've attached some pictures. Are these rubbish or repairable?? I intend to drive these with an old A&R A60 Cambridge (an early one) which I am going to recap very soon.



It's kind of odd that you bought speakers you wanted but with different drivers. :) What's the point? :D

So how do they sound to you?

If you want to investigate what you have, at the very least, try getting some measurements. You could use the Dayton smart-phone mic with Room EQ Wizard. That will be the best place to start.


I read that you bought them with different drives. That I understood completely. What I wasn't so sure of is WHY you would do that if you were looking to buy a pair of Mission 770s, but that's kind of irrelevant.

It's impossible to tell you how they are with pictures, but the tweeters don't look original, however the crossover kind of does. It has that air of cheap construction only original manufacturers can add. :D Of course you could part them out, selling the drivers on e-bay.

If you want to know how much work it would take to make them sound better, that would take measurements and at least a quality assessment from you.


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Well step one is listen to them and see how they are 'out the box'

Step 2 is to measure them. If you are up for it I can lend you a UMIK-1 and plenty of people here who can lead you through the testing. Once you know the response curve we can look at tweaks.

If you can find out the cabinet dimensions (internal volume) and port size the T-S parameter are available for the vifa M21-WJ so we can also calculate a few things for pointers.
That Vifa driver is rather a good replacement for the original polycone IMO.

What you'd hope is it now works a bit like this. Sort of speaker I like doing.


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    Mission 770.PNG
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  • Mission 770 Trial Circuit.PNG
    Mission 770 Trial Circuit.PNG
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Well, the voice coil diameter of the Vifa M21WJ-09-08 actually is 32 mm and has nothing to do with bass output. The Thiele-Small parameters of the Vifa P21WO-20-08 are almost identical and so is the bass output. I know you are disappointed because of the replacement drivers, but they are fine and there's absolutely no need to buy something new unless they do not work properly anymore.