Thanks to a friend, I had a pair of Fostex T90A’s on loan.

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The T90A ranks in the middle of the Fostex super tweeter line.

• T500Amkii (very expensive)

• T900A

• T925A

• T90A

• FT96H

• FT17H (very affordable)

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I had heard the T900A and T925A in separate HiFi show and owned a pair of the FT17H many years ago.

According to a good friend that used a few big ones, they all share most of the same sonic characteristics, with more refinement as you move up higher in the echelon. I’d tend to agree, but never had them for a side by side comparison. 

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Below is a measurement done at ~3" from the tweeter.

I have no idea if the dip at 10 kHz is the tweeter’s true response, or a measurement anomaly. It sure isn’t on the datasheet.

I only measured them once, before returning them to the owner. I’ll need to investigate this "dip" at a later date, as it showed very good measured specs above 7 kHz.