OA-12 crossover (filter)

[Adam Kimberley]

Until I have time to renovate my OA-5s, I am using a pair of OA-12s (at present with Monacor SPH-165 bass/mid units, which seem to have very similar Thiele-Small numbers to the correct Peerless unit - but that's another story!).
The treble seems quite harsh on the OA-12s, even with the 'treble cut' using the link on the baffle. I find that, on the crossover, the low-pass section is just an inductor, no capacitor (the coil looks large enough to be the 1,8mH shown on the filter schematic published on this forum) but the high-pass is the (expected) 0,5mH & capacitor, which would suggest a high-pass 2nd-order at about 2,700Hz.
My 'speakers seem to have a treble 'spike' at about 14,000hz. Are there any recommended alterations to the crossover/filter which would improve the sound until the new tweeter becomes available? (I still have the old MT20s, which are in good condition).
Thanks for any help - apologies for writing in English.
Adam Kimberley.

[Martin Dellstig]

Hi
The OA-12 was produced with two different filters, at first a filter like the one you described later on a symetrical filter with an inductor and a capacitor for both HP and LP.

Don't know if this is of interest to you but the filters commented here are mostly the symetrical one.
The asymetrical filter was rather shortlived.

One reason for "harsh sound" can be that the glue of the surrounds of the tweeters is dried out a bit.
That tends to give an "Ssssssound" to the tweeter.

Best regrads

Martin