MR902-HF

[David Deratany]

To Jim D.

Got them today; no horns attached, but horns weren't part of the deal. While I have never seen 90x's in the flesh, these must certainly be they.

You were right, no mounting studs, but I can pick up what I need at the local hardware store. Are there any special requirements, i.e. non magnetic?

Additionally, they have loading caps, which I imagine I will want to lose, and so I will need shorter screws - must they be non magnetic; and some felt for the inside of the cover. Any special stuff?

I'm quite happy with these; they are real clean. Have already put in new GPA aluminum diaphragms. Can't wait to swap out my 802D's and see what I think. And yes, they do have tangerine phase plugs.

I noticed no locating pins. Are they all like this?


Boy am I glad I didn't win the auction the previous day for almost twice as much.

[Jim D]

What you have are basically 902s. The only way to tell which mark is to remove the diaphragm and then push a piece of bar copper #22 wire down the gap and see when it bottoms. If it only goes in about 1/4 inch, these are B's. If it goes in 1/2-1" they are A's. Felt and screws can be obtained from GPA or locally. The felt fits snugly inside the cap and is about 3/8" thick. Get it from a fabric store. The screws can be cut-off with a cutting tool like that on some wire strippers or get phillips head stainless 6/32 screws the right length. No, there are no pins in the 902s, you center them the best you can, I always use an oscilator on ours. The mounting studs are steel and are 12/24 on the driver side and 1/4/20 on the horn end. GPA might be the only place to get these. You could use 12/24 all-thread with 1/4 sleeves in a pinch. Good listening, Jim

[David Deratany]

Thanks Jim; They are "A's".

[Richard C.]

Hi all,
I have 4 of these 902 drivers W/tangerine phase plugs. I talked with Bill H. of GPA about a year ago. He told me to remove the diaphragm and put a piece of paper in the gap to see what I had. I notice that "all" of them appear to have the centering ring right under the gap (about 1/4") deep and if you simply put something narrow into the gap, it will hit. What I found is, a piece of paper (or small wire) can be "worked back and forth" in the gap and will go to the outside of this initial obstruction and than go deeper (about 1") down into the cavity. This discussion made be wonder, so I rechecked all 4 of mine and found that 3 would let the paper thru (tight fit at a slight angle) and 1 was absolutely solid - and I really tried! Now I am not sure if I have a combination of 902-8A & B, a real B, or T. All 4 have loading caps. I am not sure which one is newer (A or B, T) - open to the cavity or blocked.
Richard C.