Mission 767 Tweeters Help

[Nacra6]

Hi,

I am new so thank you for having me and I hope I am not making a mistake, apologies in advance.

I own a pair of Mission 767 with the mandatory LFAU. The tweeters make a sound but its fuzzy at certain frequencies so I need a replacement or repair.

The Part number for the tweeters is R76/78-HFU-D26 "Prod code 910". I cant get these from Mission or Vifa. A few questions:

1. Does anyone know what is the significance of the "Prod code 910" designation? I saw a tweeter with the identical part number but the product code is 901 - are these the same? I f I get mu hands on one should I use it as replacement?

2. The tweeter from a brother Mission 764 is part number R767-HFU-D25, Prod Code 909. I think that the D25 means 25mm diameter which is smaller than the 767's D26 - is this right?

3. If I have no choice can I use the tweeter from 764 in the 767? Will this require crossover modification? Would I notice a sound difference?

4. Is there any recommendation who might be able to repair/restore the original tweeters?

5. Any ideas what replacement I can use? Or build?

I appreciate any input.

Thanks in advance.

 

[cherik]

Hi
Did you ever find a solution? I own a pair of 765i that uses the same model tweeter. Sorry in advance for the hijack btw!

One tweeter was very weak and I determined that the filter was fine. I measured both tweeters and don't remember the exact difference but one measured a couple of hundred milli-ohms less than the other. Something like 4.5 vs 4.7 Ohms, the latter being the one with the problem. So, it wasn't burned but I noticed that the diaphragm didn't seem to move when gently touched. With nothing to lose I took it apart..

Somehow the coil was distorted and oval and part of the coil assembly was touching the inner part of the magnet, causing the diaphragm to get stuck. I carefully tried to shape it again while using vernier calipers to make sure it was as round as possible. It was moving freely after this, without any scratching sound.
It was, I assume, oil filled and maybe somewhat gunked up and/or some had leaked a bit. I left that as it was.

A quick check after reassembly confirmed that it is at least somewhat working now - maybe as good as the other tweeter - but I'll have to wait till tomorrow to really check them. SWMBO would undoubtedly object violently to me thoroughly checking them now..

I assume that both must be replaced, if it turns out that this 'repair' isn't enough, which would destroy the working one in the process. And what about the oil? This is more or less my first speaker repair.

Would something like this from fleabay work okay/be worth it? I think they would fit physically. Too cheap and/or rubbish? How would it sound?

The other drivers are in excellent condition and the cabinet is a 9+ on a scale of 1-10 so I would like give them new life, and perhaps sell them at some point.

 

[larryldspkr]

I've used these as replacements for that tweeter, bolts right up to the aluminum wave guide. Or you can buy the Scan Speak version for $30 more, same tweeter.

Vifa D27TG35-06, 1" Dome Tweeter

Larry

 

[cherik]

Thanks Larry, I'll seriously consider those. Still not much money but a bit more pricey than I'd hoped.

I've now performed a test at considerable volume levels and I must say that I'm pleasantly surprised. Still only with the speakers side by side but they do sound quite nice. My 'repair' appears to have worked but I'll have to listen to them under better conditions to determine if it really was a success.

I may hear a small difference in volume levels from left to right while turning the balance from side to side but fear that I'm biased. Is a difference of about 200 mOhm from tweeter to tweeter audible?

Any idea how the coil assembly was distorted like that, someone poking a finger in it perhaps?