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RE: MGIIIa tweeter question

Posted by Davy (A) on August 12, 2014 at 10:12:07

In Reply to: RE: MGIIIa tweeter question posted by Roger Gustavsson on August 12, 2014 at 08:11:52:

Well the channel in the newer tweeter is clearly narrower so I assume the magnets are probably closer too , - not checked for sure. I am pretty sure the width of the whole cage is narrower on the newer tweeter.

I had previously toyed with the idea of trying to install the newer narrow 3 ohm ribbon foil in an older type wide cage (previously used for a wide foil) but the problem with that is that the tweeter is usually glued to the side of the cage in various places to damp it and stop twisting and distortion, and you would not be able to do this. Also the magnet gap might be different too.

Wow that's a big rebuild job you are doing and sounds great. So your mids were originally shot? Sounds quite hard to use new mylar how do you know when the tension is correct? Using thinner mylar might indeed improve the mids, the only thing I might worry about is that there is then a even bigger speed difference between the mid and bass (the bass is already quite slow in relative comparison to the mid and tweeter)

Sorry I see what you mean now about the crossover, - you are actually intending to use a HP PLLXO on the external mid/highs crossover (i.e. a capacitor), not active.

Yes the post 3.3R 3 series speakers are rolled off a bit early in the mids and the tweeter has to go low. In the older MGIII and MGIIIa it's not as much for some reason. Its possible Magnepan wanted to take the midrange lower in the post 3.3R speakers to improve the lower midrange suckout that can occur in many rooms.

So it's a 18 6 12 12 crossover you intend to implement that is like a MG20 or MG20.1 crossover configuration. That can work quite well, - tried it before, but the 18 6 6 6 crossover sounds much better in my opinion due to the linear phase of the mid and tweeter and the whole things sound much more coherent and seamless. I strongly recommend to try it out. Once I heard it there was no going back. It's also cheaper as you are using less components. You can used a spaced 6dB crossover between the mid and tweeter if necessary to protect the tweeter and it still sounds v good as there is a good overlap between mid and tweeter due to the mild 6 dB slopes (I am using -3dB points of 3 Khz on the mid and 5.3 Khz on tweeter).

Edits: 08/12/14

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