Help with old Mission 770

Hi everybody

I have a chance to get a pair of old Mission 770.
I'm not sure about a few things and would appreciate any help.
I haven't heard that particular set yet and have not seen them in person.
I want to check first if it makes sense to drive 3 hours to check them out in person. :)

1.) There seem to be scratches or discoloring on the bass. See the first picture. Is that an issue? Or signs that it got hit or something?

2.) The owner does not know what version and from when exactly they are. But the handwritten serial number looks like it is from a really early stage.

3.) Does Mission 770 of that age need any major overhaul after all that time? Crossover, Caps, ...?

4.) What would a pair of those be worth right now? Because the price seems a tiny tiny bit higher than what I see others go in the US for.

5.) Can I drive those with an Elekit TU-820R or is that a bit on the lower side?

Thanks a lot and Happy weekend.



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1) The surface of the polypropylene cone may simply be dirty or the material may be discoloured with age.


3) The tan coloured capacitor shown in the following crossover board image is a film type which does not deteriorate with age.


4) They are worth what someone is willing to pay for them. Perhaps around £80 for a pair in good working and cosmetic condition.
I think SET amps are usually better with closed box, being poor on damping, but you could always stuff a pair of socks in the reflex tube...

Aside from listening to them and seeing if the tweeters work, and you can put your hand over the tweeters to do this, I would gently push the bass cones in with three fingers and listen for voice-coil rubbing.

Which can sometimes be cured by rotating the bass driver 90 degrees.

These old SEAS 104mm tweeters often have dried up and solidified ferrofluid, which is easily replaced.

I guess it's a SEAS P21RE 8 ohm polycone bass, which quite resembles the newer paper CA22RNY in response:

SEAS P21 RE 90dB 1.1mH Polycone.JPG

The bashed in dustcap is easily pulled out with a bent pin and a bit of glue over the resulting hole. Vacuum cleaners can do the job too, apparently.

It's a poor man's Spendor BC1 in concept, and the cabinet is a classic BBC thin wall. Damping pads are affixed to the side walls and top and bottom in the full take on thin wall construction.

Using staples and glue. Polycones were acknowledged to have a dull and undetailed sound, but some call that smooth.

The crossover resembles this third order 3kHz approach with a 1.5A SB fuse in front of the tweeter filter.:

Monitor Audio R300-MD Original.PNG

If the drivers are completely broken, you likely could rebuild it as a SEAS Aphel:

I would want to know the bass cutout measurement and the bass rebate measurement to know how easy that might be to do. 220mm and 186mm for modern SEAS basses.

The modern Mission 770 goes for £2500, so it would be a good investment.

Best, Steve.
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If you have to drive 3 hours the price must be quite low. I don't think the sound will impress you, even less with an 8 Watt amp.

it is a classic vintage cabinet design, with a moden speaker kit it may be a nice restomod. Selling the original speaker and crossover on ebay may be a good idea.
See here for some words regarding the original driver, apparently it was a Chartwell, then missions own version of it once Chartwell had ceased trading.

So if the original has a lot of wear maybe pass, especially if you have to drive for three hours . Ideally you want to try them with your valve amp to see how they behave. Maybe wait for a pristine pair if its mission you are after.

There is a suggestion for a mark audio 10p design. If woodworking and a bit of soldering appeals maybe one of these could be sensible especially as some of the designs consider output impedance of valve amp output stages in their design.
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Hi everybody
Thanks, first of all, for your input. Very much appreciated.
I decided to pass for now. The owner told me the Missions are from 95 and suddenly wanted above 600 Euros for them.
Not worth it.

I have the Mission 762i at the moment, and they are decent. That's why I was looking for the Missions 770 or 700.

I'll look into the Mark Audio 10p design, but might need help again.

Happy weekend.

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600€ is twice the price new... ridiculous. Anything higher than 100€ for a pair is robbery.

You should look at eBay Kleinanzeigen, with some patience you can find very rational priced stuff there. OK, some lunatics too, but usually moderate priced offers, cheaper than ebay etc.
Expand your number of options, don't just look for a single model.
Anyway, as audiophile speakers were very rare in Germany (and still somehow are), there are more Heco, Canton, WHD, Braun/ADS and even worse brands on sale.
Also, I don't know of many 8 Watt tube amp capable speakers of that time, except some very exclusive rarity's.
Thanks, Turbowatch.
I was also looking for JBL L100, but they seemed to be a bit clunky, as many say.
Wharfedale Linton, KLH 5, ...
I just love the Mission 770 design. :)

I'm running the 8W Tube here with Mission 762i. They ask for 25 Watts as well and they sound actually really decent. The volume is not even at 50%, and they are loud enough for my listening taste.

I keep searching.


As some here explained, it is not the Watt that is the problem, but the reactive load of the speaker that tortures the poor 8 valve Watt.
Maybe buy a cabinet you like and simply install a nice full range speaker inside (just for looks the tweeter can stay).
This may be the best option for you. Just from paper no one can tell you how some vintage or new speaker will sound with your amp.
If you can effort it, get a good, low priced D-amp for comparison. The Aiyima A07 or A07max are perfect for this, at less than 60€ from Aliex to your home, all in.
When the D-amp sounds better, your valve has a problem with the speaker load. Only risk: You may loose your faith in valve amps. So better don't do that. As a hint on the side line, there are nice valve preamps that give D-power that warm glow...
I looked into the Mission 762i and it looks a goodish polycone 8" plus metal 1":

Mission  762i.jpg

Crossover is OK, being 1-2mH coil plus (10uF?) capacitor and a damping resistor in shunt, to overcome the bass voice-coil inductance. Tweeter is typical 5.6-6.8uF Capacitor and resistor (2.2R?) series, and small (0.2mH?) coil in shunt. Probably positive polarity BW3, but I don't know.

Mission 762i Crossover.jpg

The enthusiast here has been upgrading to MKP capacitors...

I think you could line the cabinet with glued or stapled carpet in some way. Looks nice.
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Hi system7

Thanks for that info about the 762i. They are decent good speakers for their age (31 years old). Especially for the price I paid back when I bought them new from my confirmation money. :ROFLMAO:

I'll have to decide whether to get a bigger amp and then a new speaker or else. I will try my 8W tubes at a friend's place over the weekend with his Wharfdale Linton 85 to see how well that'll work.

But maybe I'll check my 762i and keep them for a while longer. What do you mean with the carpet? Putting carpet on the inside walls?
Do you have a link to the MKP capacitors or to the page of this guy?


system7's image of the reworked 762i crossover is contained in the link below.

The member simply says that good quality film capacitors have replaced the old electrolytics.

P.S. I've attached an image of an original 762i crossover which shows the two bipolar electrolytic capacitors that you may wish to upgrade. Dayton Audio polypropylene capacitors would be affordable substitutions:*MTcxMzE4NTIwNy4xLjEuMTcxMzE4NTI4MS4wLjAuMA..

P.P.S. With a claimed sensitivity of 93 dB, the 762i will go loud with just a few watts.


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