I just made some repairs an a set of vintage 2167F Magnepan speakers whom tweeters had oxidized away. After taking the cloth off I found the mylar was pretty rough with cat scratches, but the bass coils were well attached. I patched the worst offenders with info from the MUG forum and let the rest go. I decided to go with a DIY fix (read inexpensive) and used 35 gauge copper wire I found on a old solenoid instead of the original 31 gauge aluminum from Magnepan. 33 gauge copper would have been a near perfect resistance match but I had 35 gauge...
Now my tweeter has a resistance of 9 ohms instead of the 5 ohms it had originally (same as the bass circuit). It sounds much, much better than with no tweeters but I have to turn up the treble all the way on the preamp to apparently compensate for the greater coil resistance (and change to the crossover frequency)? The stock first order butterworth looked - according to the formulas I found - to benefit with cutting out half of the 20uf caps to get the X-over frequency back close to original - in practice I heard very little change. However in my experimentation I found the most helpfull treble adjustment by bypassing the unknown value of the inductor in the bass circuitry (I suspect I am letting more treble into the bass panel and who knows what else). The speaker overall has nice tone and deeper bass than my SMGA's but I am trolling for any suggestions on how to finish off the project. Anyone have experience in this matter.
PS The 2167F may be an early MGI of MGII
Regards to all
Now my tweeter has a resistance of 9 ohms instead of the 5 ohms it had originally (same as the bass circuit). It sounds much, much better than with no tweeters but I have to turn up the treble all the way on the preamp to apparently compensate for the greater coil resistance (and change to the crossover frequency)? The stock first order butterworth looked - according to the formulas I found - to benefit with cutting out half of the 20uf caps to get the X-over frequency back close to original - in practice I heard very little change. However in my experimentation I found the most helpfull treble adjustment by bypassing the unknown value of the inductor in the bass circuitry (I suspect I am letting more treble into the bass panel and who knows what else). The speaker overall has nice tone and deeper bass than my SMGA's but I am trolling for any suggestions on how to finish off the project. Anyone have experience in this matter.
PS The 2167F may be an early MGI of MGII
Regards to all