Another pair of Pioneer/TAD to modify

Another pair of these TZ-9LTD came about for cheap and I have them here. The original mids are trash, but they can be repaired in Japan for ¥30,000 per (in Magnesium).

I have a pair of Be TAD drivers here, all similar parameters as the original, only with the Be goodness. But they don’t mount the same. So mod time!

To mount them using the back mounting system the originals had means drilling the backplate and thread tapping the holes. It’s nerve wracking because there’s a chance for a lot to go wrong.

I bought the necessary tools and measured the depth of the holes on the originals. Got the drill stopper and put it on the bit. Made my midrange driver jig up so the screen and dome don’t contact anything.

Today I did the first hole. The bit type is a wedge head, it bites slowly do things don’t bind or worse crack. It took FOR EV ERRRR to drill, but I got there. Then the three taps and special tapping wrench sloooowly to create the threads.

Success! This will work. However I am buying a tabletop drill press for the remaining 11 holes. I get seven turns of threads to the bottom of the threads so it’s a good bite.

In the cabinet, there is a cutout where the original driver was countersunk. This one will not do that. So I measured and found square cut o-rings and dang if they don’t fit like a glove. I will put two rings of Mortite behind the ring to lift it above the baffle so the flange of the mid never contacts the finished surface, and so it’s sealed and doesn’t buzz. Shown is one in the groove and then one for size.

The idea is for all of this to be reversible without a trace.

Some pics from beginning to now.
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S0und Dragon

Moderator and Circus Hand.
Staff member
I think not many folks are familiar with the speaker in question, Much less the significance of the modifications you are in the process of doing. Some light reading for those who are interested or simply curious.

These speakers are pretty rare and quite desirable. The Beryllium Mids should really elevate these speakers bud. Looking forward to the progress.
You’re welcome to come up and use the mill. Makes life a lot easier.
Yes it sure does. I appreciate the offer! I will not be hand drilling the rest of the holes.

I do think that I want a 10-12” bench top drill press. It would not be a one use item here.
It’s looking good. I have the Mortite in double thickness behind the o-ring and I’ve cut half moons out of the ring 180° from each other to allow for cable pass through. The Mortite will not fully compress, one does not need to crank the six mount screws to hell for a good seating. This will keep the small distance from the high gloss baffle as mentioned before. Interesting that Pioneer cut the MDF when the original mids hooked from the back. It’s like they were considering a few things when in the creation stage.
On the plastic housing is a thin sheet of gasket, which I will add to for making up the difference the Mortite will add in. I want the backplaflte firmly against something so it isn’t being pulled on without support. It’s how they solved the issue on the originals. For cosmetics, I may source another pair of large but much thinner rings for the gap if it is bothersome. Maybe just 1/2” too small vs. the flange so it rolls over it and snugly into the gap. Will look more finished. A nice rubber polish and done.
Mortite under ring pic.
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Just Call Me Junior
I recently read about the TAD compression driver design in "High-Quality Horn Loudspeaker Systems" (Kolbrek/Dunker), the legacy of compression drivers is amazing. Very cool!
The six holes are drilled and with little fanfare using my new press. I also used a carbide tipped cutting head bit, it is gentle and accurate. No binding and no shaking. The magnetic shavings were dealt with by using a stronger Neo magnet ring to pull them away. Ready to tap now. DD0F4CF2-AF87-483C-A270-FB33984EB002.jpeg6A55A589-797F-432D-BDD6-7B0F0A32D096.jpegD8CA0243-7BCD-4D58-AA50-A83FC76070F2.jpeg8A00CF59-9BBE-4EC8-97D9-5D1CE891A6A9.jpeg14222D6D-BB6A-45F7-B7AC-A4C0140819EA.jpeg2A339F7B-286D-48F0-8D95-2CB18E0C8DA9.jpegB7B7E779-5FFD-45EB-ADDA-61EBC7BCA388.jpeg
First one tapped. Good enough, I made a mod to the jig to combat the slight tilt when pressed upon. Bottom line is that in this install this will be perfect. 30F66228-285C-4DA6-896E-ACE8722F9B51.jpegEAA5BC6D-392F-4922-96B9-2B0E5DA3ED4B.jpegF372F09D-B423-41FF-8E90-F65B407D05F3.jpeg