Altec Lansing Diaphragm Identification

[Dmajor]

Hi all, greetings from Australia. I am a first time poster & long time lurker. Could more knowledgeable members assist me in identifying 2 x Altec diaphragms. This 2 came out of my Altec 291-16a compression drivers during a routine cleaning of the magnet assembly. To my surprise both look different & sounded different in individual output. I included pics of the drivers, front & back. Thank you all.

[Earl K]

Hi Dmajor,

Welcome!

Both appear to be valid/real Altec parts.

The 1st pic is of a 291-type ( Altec 21531 (https://www.worthpoint.com/worthopedia/altec-lansing-21531-diaphragm-voice-136831102) ) diaphragm while the 2nd pic is of a 288 type diaphragm.

They will sound different with the 288 going higher and sounding a bit more detailed & "sparkly" ( it's also more fragile, with lower power handling capabilities ).

:)

[Dmajor]

Thanks @Earl K, much appreciated.

Are after-market replacement diaphragms created equal in terms of built & sound quality ?

[Earl K]

Thanks @Earl K, much appreciated.

Are after-market replacement diaphragms created equal in terms of built & sound quality ?


I'm not aware of any that match real Altec diaphragms's ( in build and sound quality ).

I am aware that there are some asian-made replacements that use titanium for the diaphragm dome ( instead of the original aluminum ).
- I've never seen any évidence in my 20 years of watching that any aftermarket types match the originals in db output and response linearity ( presented in a graphical/readable form ) .

:)

[Riley Casey]

My experience with after market Chinese diaphragms is that you may have to buy quite a few to find a matched set.


Thanks @Earl K, much appreciated.

Are after-market replacement diaphragms created equal in terms of built & sound quality ?

[Mike Caldwell]

The diaphragm in the third picture from the top looks like someone has repaired the voice coil leads.
The lead on left looks to be soldered back together and the one on the right looks like a section
of the original lead has been replaced with a small piece of tinsel lead wire.

Years ago I did those same repairs on a few Altec diaphragms to keep them working for one more show.
It's takes micro fast soldering!

[Dmajor]

Bravo, gents Thank you all for the very helpful info.
Just a silly question.
is there a way to ascertain the correct Right / Left polarity of the driver ?
As there are no +/ — markings. Both drivers comes with green & brown connecting wires.
Please correct me, I am guessing Green (+) ? Brown (—)?

[Earl K]

Bravo, gents Thank you all for the very helpful info.
Just a silly question.
is there a way to ascertain the correct Right / Left polarity of the driver ?
As there are no +/ — markings. Both drivers comes with green & brown connecting wires.
Please correct me, I am guessing Green (+) ? Brown (—)?

You're really better off Googling "Altec 288C" to view pics of other peoples opened-up ( 288 ) drivers ( that's what I did since I'm never able to remember Altec's older polarity convention ).

You'll see in many pics that Green is connected to L1 ( "L1" ink stamped on most older diaphragms ).

:)