Audax Tweeter repair - some advice please

[coylum]

I have two late 1970's Heybrook HB2 speakers which use Audax HD 12x9D25 tweeters. One has gone open circuit - I can see the break in the fine wire going to the voice coil. The other appears to be working OK but in both cases the foam "dome" between the magnet pole piece and the fabric dome has disintegrated. It would seem that this foam was originally glued to the pole piece.

I can buy new coil assemblies from Falcon Acoustics in the UK (I plan to replace both) but I am not sure what to do about the foam. Is this foam really necessary for the sound quality or is it just there to protect the fabric dome from being inverted by inquisitive fingers?

http://www.falconacoustics.co.uk/dr...2-voice-coil-hd12x9d25-hd12x8d25-tweeter.html

If anyone has experience of replacing the voice coils in these tweeters I would appreciate any relevant advice. It looks straightforward - but that always concerns me!

Thanks

 

[jcamero]

Self centering. Just remove the 4 screws, take off the old, and replace with the new. Very easy. When you remove the old, you will see the short mounting "pegs", I doubt if it matters, but I made sure the + and - were on the same side as before I started. 10 minutes to replace both. Can't speak to the foam issue.

 

[turboyam]

The foam is probably there to attenuate back of dome resonances. Some manufacturers use a round piece of yellow acoustic fiberglass. Permanent, cheap
and easy solution.

 

[coylum]

Self centering. Just remove the 4 screws, take off the old, and replace with the new. Very easy. When you remove the old, you will see the short mounting "pegs", I doubt if it matters, but I made sure the + and - were on the same side as before I started. 10 minutes to replace both. Can't speak to the foam issue.

Thanks for the confirmation that it is relatively simple... now I just have to wait for the new voice coil assemblies to arrive from the UK

 

[coylum]

I think you are correct.

After further inspection the original appears to have been a piece of open soft foam, same diameter as pole piece, domed and glued to the pole piece. It is not clear whether the foam touched the inside of the fabric diaphragm but I think not.

I doubt that I can recreate the dome shape but assuming the function is to dampen the sound waves from the back of the diaphragm and not the diaphragm itself (?) then I think a small circular felt self adhesive protective pad attached to the pole piece may do the trick....

Thank you

 

[turboyam]

Yeah, it is not supposed to touch the diaphragm as an ''anti-curious finger thingy'' it,s really there to absorb back wave.
Not that an Anti Curious Finger Thingy is not needed!, i'll work on this and get rich! hahaaaahahaa!!!!

 

[coylum]

Yeah, it is not supposed to touch the diaphragm as an ''anti-curious finger thingy'' it,s really there to absorb back wave.
Not that an Anti Curious Finger Thingy is not needed!, i'll work on this and get rich! hahaaaahahaa!!!!

Thanks again.... and good luck with the ACFT

 

[canuckaudiog]

I think you are correct.

After further inspection the original appears to have been a piece of open soft foam, same diameter as pole piece, domed and glued to the pole piece. It is not clear whether the foam touched the inside of the fabric diaphragm but I think not.

I doubt that I can recreate the dome shape but assuming the function is to dampen the sound waves from the back of the diaphragm and not the diaphragm itself (?) then I think a small circular felt self adhesive protective pad attached to the pole piece may do the trick....

Thank you

I think the one other thing to consider is the weight. I imagine if you added something heavier than what was there originally it would change the response of the tweeter.

Just a thought. Good luck with the repair!

 

[coylum]

I think the one other thing to consider is the weight. I imagine if you added something heavier than what was there originally it would change the response of the tweeter.

Just a thought. Good luck with the repair!

Thanks for the good wishes....

I'm not sure that the weight will have much affect as it will be attached to the stationary magnetic pole piece - perhaps more importantly will be its ability to absorb the reflected sound. I will treat both tweeters identically and I have the facility to measure the finished frequency response so I should be able to detect any significant change in the high frequency response

 

[canuckaudiog]

Thanks for the good wishes....

I'm not sure that the weight will have much affect as it will be attached to the stationary magnetic pole piece - perhaps more importantly will be its ability to absorb the reflected sound. I will treat both tweeters identically and I have the facility to measure the finished frequency response so I should be able to detect any significant change in the high frequency response

Oh I see, I thought you were saying it went underside of the dome itself. Or at least that's what I've seen on other Audax tweeters. Ignore what I said then

 

[purple1]

I just did one of these on a set of Speakerlabs I got. Can't really help with the foam as mine was good, but I will say the replacement from Falcon is an easy and perfect drop in. Good luck.

 

[coylum]

I just did one of these on a set of Speakerlabs I got. Can't really help with the foam as mine was good, but I will say the replacement from Falcon is an easy and perfect drop in. Good luck.

Thanks for that - now just have to wait for the voice coils from Falcon