[kappa546]

I just got a pair of 2.5s and I want to try bypassing the fuse and attenuator from the circuit.

Looking at this picture, do I move the brown wire from the fuse holder to the bottom right plug? (Fuse bypass)

Do I connect the lead from the top side of resistors over to either of the plugs on the right? (Attenuator bypass)

Does that sound right or am I crazy?




What the heck is that 2uF cap there for?

[kappa546]

Also, the schematic shows a 1mH indicator parallel to the tweeter, is that the small coil on the bottom? Seems big for 1mH...

[kappa546]

OK well I tried what i described in the first post to one panel and things got really shouty, ribbon was overbearing and midrange seemed to drop even more (the crossover region is too recessed in stock form, some quick measurements confirmed this).

I moved the wire coming from the resistors back to the bottom left plug (attenuator), I have no speaker wire jumper across the plugs. Then I moved the brown wire to the resistors on top.

This rebalanced the sound. I guess I'll just wait until I get some feedback before I proceed further.

[Davey]

If you think the speaker is too "recessed" in the midrange you can't fix it by disabling the fuse and/or tweeter attenuator.  You're going to have to make an actual change to the crossover. 

I suggest to reduce the value of the 3.25mH coil in the bass circuit.  That will push the turnover frequency higher and "fill" the midrange somewhat more.

Dave.

[kappa546]

I understand bypassing the fuse/attenuator does nothing to the frequency response, sorry if my comments were unclear. I'm bypassing for the same reason others do, to clean up the treble.

As far as the crossover, I was planning on trying a 25uF cap (already have some on hand) for the tweeter instead of bringing the bass panel up. I've read that some 2.5R came that way from the factory, presumably a design tweak before the 2.6R redesign.

So far I think I've managed to bypass the fuse, am I correct? How can I bypass the attenuator?

[Davey]

The attenuator is already bypassed according to your photo.  (You have the jumper in.)

I was unaware that some 2.5 models shipped with a larger capacitor, but changing that tweeter capacitor to a larger value will certainly move turnover frequency down.    I don't know if that will solve your issue.
I suspect Magnepan changed this capacitor to 15uF for good reason.

You could probably do without the 2uF capacitor.  It shelves up the response, but mostly above the audio band.

Cheers,

Dave.

[krikor]

If I am looking at this correctly, and you just want to bypass the fuse, you can simply move the brown wire from the top tab of the holder in your picture to the bottom tab where the 2uf cap and resistor are tied together.

To bypass the tweeter attenuator jacks/jumper, you can simply put a wire between the two tabs of the bottom jacks. Things could be cleaned up and wiring simplified a bit more, but for testing that will essentially take the jacks/jumper out of the circuit.

[kappa546]

Well technically the wire from between the attenuator plugs is no different than just using a piece of wire on the outside... the signal still sees both steel plugs. Aren't the steel plugs exactly what people are trying to bypass?

I have bypassed the fuse on the right speaker only, both attenuators have a 1" piece of speaker wire. The ribbon with the bypassed fuse has about 3db more output!

[Davey]

Bad connection in the fuse holder circuit somewhere.
This is not uncommon......unfortunately.  The little lockwasher tabs are poorly riveted and/or the fuse holder clamps are not gripping the fuse well.

The steel jumpers for the attenuator are not an issue provided the set-screws are properly tightened.

Dave.