OEM ALTEC Diaphragms #34627 PT.1

DT667 has been using "aftermarket" aluminum diaphragms on his Altec 808-8A compression drivers since acquiring them in 2014.  The replacement diaphragms were sourced from Simply Speakers (part #  D-808-8) and sounded subjectively good.

DT667 has now installed OEM Altec replacement aluminum diaphragms ( part # 34627 -  8 ohms - 6.2 ohms measured on DMM) from Midwest Speaker Repair and the "conversion kit" for Altec OEM 800 series replacement diaphragms from The Speaker Exchange.

DT667 offers some advice for those planning on installing OEM Altec replacement diaphragms.

A) The aftermarket diaphragms from Simply Speakers had a hole pattern on the diaphragm surround that would allow for installation of the loading cap - critical for  using the 808-8A in higher power PA applications with original Symbiotic diaphragms or for just protecting the diaphragm from damage during installation.

B) The OEM Altec diaphragms didn't have a hole pattern in the surround that would allow for installation of the loading cap properly.  

From what DT667 has researched, many Altec diaphragms were installed without the loading caps in domestic use environments.

C) The "conversion kit" for Altec 800 series replacement diaphragms purchased from The Speaker Exchange has some issues.  

On first inspection, none of the connectors on the kits were soldered in place.  This required DT667 to add some solder to secure the connections in a proper manner. 

The push on connectors were apparently too tall to allow closing the rear cap on the compression driver securely.  DT667 had to cut those off and solder wires directly to the tabs on the compression drivers.  Another inconvenience but probably a better way to secure wires than push on connectors.

D) The cost of (2) conversion kits was $12 each and required modifications rather than being a "plug and play" operation.  At least the wires were of better quality than the original wires that Altec used on the 808-8A , at least the wires on DT667's units.

DT667 advises to build your own connectors with high quality wire and ring connectors or whatever you see fit for the application.

A frequency sweep from 1K- 20KHz with a audio signal generator confirmed that the diaphragms were installed properly in the compression drivers.

Subjectively, the OEM Altec # 34627 diaphragms sound absolutely fine. 

There seems to be a bit more "air and 3 dimensionality" to the sound vs. aftermarket diaphragms.

That could be due to the removal of loading caps but the net effect is good so far.

Note : DT667 uses Altec 808-8B horns with the 808-8A compression drivers.

DT 667   July 4, 2021

There are basically 3 options for wire termination to an Altec Compression Driver like DT667's 808-8A alnico units.

a) use the OEM Altec spring terminals - made of budget grade nickel plated metal.

b) use an aftermarket binding post - many options to choose from here.

c) solder high quality wire directly to diaphragm push-on connector tabs and route wires through the compression driver cover.

DT667 opted for option "c" and added rubber grommets to insulate the cover holes and further protect diaphragm wires.  There was no strain relief added inside the driver cover to secure the wires.  If a problem arises with soldered wires coming loose from the tabs,  binding posts will probably be the next step to replace OEM Altec spring terminals.

DT667 uses a "military grade" 16 AWG silver coated stranded wire recommended by MLP design team member / legendary DIY SE tube amp builder Jeffery D. Medwin aka DrLowMu for Altec compression driver wiring duties.

Now for some subjective listening to hear if things have changed or improved with the latest Altec compression driver modifications.

DT 667   7/11/2021