Found a 602D

[hmole]

The t3000 are all pretty much the same, they had a bracket for mounting them in cabinets, or they just screw into 3 holes tapped into the pole piece on the bass unit for the duplexes, the 601 is a very nice driver, I think the inferiority to the "Big Gun" 604 is not sound quality but maximum output. The t3000 is very nice. I have disassembled one and failed to improve the nonworking status. MicroMike is the sole provider of support for those, he quoted me around $120 to repair one, but I never followed up on it.
I think he has a special jig for inserting the diaphragm, not a DIY job from what I understand.
Harry

[Audio_by_Goodwill]

Originally posted by hmole:
The t3000 are all pretty much the same, they had a bracket for mounting them in cabinets, or they just screw into 3 holes......

<font size="2" face="Verdana, Helvetica, sans-serif">Thank you for confirming that.

.... the 602 is a very nice driver, I think the inferiority to the "Big Gun" 604 is not sound quality but maximum output........

<font size="2" face="Verdana, Helvetica, sans-serif">I don't recall where I read it, maybe here, maybe Audio Karma, but it's my understanding that the 602 (or was it the 601?) has a hole in the middle of the frequency response. The 3000 doesn't go low enough and the woofer can't go high enough.

The t3000 is very nice. I have disassembled one and failed to improve the nonworking status. MicroMike is the sole provider of support for those, he quoted me around $120 to repair one, but I never followed up on it.
I think he has a special jig for inserting the diaphragm, not a DIY job from what I understand.

<font size="2" face="Verdana, Helvetica, sans-serif">I've read that he will supply the parts. I was tempted to pull things apart and take a look at things to see if I felt if I could replace the diaphragm, since that would be cheaper..... and I like the idea of doing things myself. However, I decided I'd be further ahead to sell it and bank the money for later.

I'm trying to get away from getting into so many projects. I have the tendency to temporarily get enamored and involved with everything that pops up. Then when something comes along that I am REALLY interested in, I don't have the time/space/money/etc to take it on.

<font color="#FFFFFF" size="1">[ November 17, 2008 12:14 AM: Message edited by: Audio_by_Goodwill ]</font>

[bfish]

Having the parts is of no use without the assembly fixture needed to put them together. The extremely fine coil is glued to the extremely delicate mylar 'fram, which is in turn glued to the magnet assy. The tolerances are far too tight and the parts too small and fragile to be assembled by hand.

The design and assembly process originated as a microphone in Bell labs. In the Bell patent for the fixture and assembly process, one can see how it's done. Figure 1 shows the exact assembly layout, and figure 7 is the exact replica of the final assembly once everything's glued together.

"Aha!" says the cunning reverse engineer/DIYer, "I'll just borrow the complete assembly from an old Altec (model unnamed for obvious reasons) microphone!" That would work if you can live with a 50 ohm tweeter...

Having reached these conclusions the hard way I can say assuredly, MicroMike is the only answer.

Added;
Here's what they look like inside (patent image far left);



<font color="#FFFFFF" size="1">[ November 17, 2008 10:15 PM: Message edited by: bfish ]</font>

[Audio_by_Goodwill]

Originally posted by bfish:
The design and assembly process originated as a microphone in Bell labs. In the Bell patent for the fixture and assembly process, one can see how it's done.

<font size="2" face="Verdana, Helvetica, sans-serif">Oooo, thank you.... I never thought about a patent.

<font size="2" face="Verdana, Helvetica, sans-serif">On the far right, is that a field coil? I assume this is a disassembled microphone, and not the tweeter.

[bfish]

You're welcome. Yeah, what Google did for patent searches might be considered as important as some of Bell Labs own contributions.

Not a field coil, as the aux. winding you see is around the pole of a permanent magnet. The mic application was a dual impedance model, and the coil provided the high impedance range when configured in series with the voice coil (via a 3-terminal arrangement).

The pictured pair is straight out of a pair of H3000s though (albeit the older, green, 'glass exponentials), and exactly what are inside yours, plus a gasket, tensioning spring, and retaining plate not pictured. The snipped off aux coil is further proof the sub-assemblies were borrowed straight from the mic parts bin.

The 'frams dome and VC are 3/4", but the horn throat is 1/2", so the fram is actually compression loaded. I presume the HF range could have been even further extended had they employed a phase plug, but the Mylar probably couldn't stand the extra loading.

The tiny VC was glued directly to the feather-light Mylar 'fram sans coil former. The whole moving mass (what little there is) hinges directly on the axially-opposed coil leads (and the tangential suspension). Herein lies a weakness, as the coil leads are only held in pressure contact with the opposed terminal contacts (seen in picture) by the 'frams glued perimeter. I suspect this is actually the cause of many H3000 failures rather than a burned VC, as on the pictured example, the VC was intact and continuous once extracted, even though it measured open circuit before dissassembly. Still no way to fix it without dissassembly though, and once apart, you're screwed without the assembly jig.

It's interesting to note the 'fram was held in the assembly jig with suction (see patent figure 1).

<font color="#FFFFFF" size="1">[ November 17, 2008 09:56 PM: Message edited by: bfish ]</font>