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Help with MG-IIIa ext crossover

45.51.47.9

joepark@gmail.com

Hello,

I'm just getting into HiFi / vintage audio hobby and it's been very fun so far. My most recent purchase is MG-IIIa and I hope someone more knowledgeable can shed some light on this.

The seller said it was not working right and I got a good price for it. Inspecting them at home, I see that one of ribbon tweeter is ripped (which I ordered replacement of it), and sound is muffled and not right. However, when I connect the speakers directly from the amp, skipping external crossover, it sounds just fine. I presumed external crossover is broken, but when I opened it up, I see that wires does not make sense. The box has 2 sets of input and 2 sets of output (mr/twtr and bass). I thought 2 sets of input were identical to each other, just providing banana type and screw type for convenience. Looking at the internal, it looks like one input is for bass and one input is for mr/twtr? Has this crossover been modified? I attached pictures of it. The seller did not know much about the history of the speakers. Any insights are greatly appreciated.

On side note, I see that inside of the crossover box, these bare wires are touching each other at some point - that can't be right, is it? I tried to separate them out, but maybe whoever modified it (if it's modified), they did sloppy job?

Thanks!

Joe

Follow Ups:

RE: Help with MG-IIIa ext crossover - joepark@gmail.com 03:30:03 12/04/22 (2)
Bit of update - it looks like it was modified that 1 set of input goes to mr/twtr and other set of input goes to bass. I'm suspecting that it was modified to do horizontal biamping. For now, I just jumped both input, same source feeding both input - and it sounds correct (well, sounds really good actually to my ear). I'm just starting to put together system around this speakers, so it will have to do what what I have for now as I get more equipment. I'm thinking maybe active crossover, or original crossover if I can find them. I definitely need more powerful amps, which I'm actively searching for. Currently, a receiver is driving it (pioneer sx-737) cause that's better one of 2 that I have, other being harman kardon 330b. Even with this small receiver, the speakers sound like nothing I heard before, even with 1 missing tweeter. Hopefully I can find better amps soon so it can do justice for this speakers. Thanks for your insights!
- When you get a good amp, you'll be very pleased. Also, don't... - MWE 07:57:24 12/04/22 (1)
  forget that placement and amount of toe-in are critical. After about seven years, in three different rooms, never feeling like they were up to their potential, I finally JUST A FEW WEEKS AGO found the ideal spot for my 3.6Rs, where everything- focus, bass, and inner detail, just locked into place. So be relentless in experimenting with setup if you're not completely happy with initial results after getting a better amp.
  
  Mark in NC
  "The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon
  - RE: When you get a good amp, you'll be very pleased. Also, don't... - joepark@gmail.com 14:28:02 12/04/22 (0)
    Thanks, yup, I love tweaking and experimenting - I'll be having a lot fun with this speakers. I tried few orientations and just bit of movements make a big difference! Can't wait till I get a proper amp.
RE: Help with MG-IIIa ext crossover - neolith 09:23:49 12/03/22 (0)
There should only be one set (+ and -) of inputs and two sets of outputs (bass and mid/twt). Look at the schematic on the top of the box. If you have two inputs, the XO has been modified. I suspect if you look carefully you will be able to figure out which input is original and which is modified. I would disconnect the added input. Also take care to observe polarity of the connections from the box to the speakers.

"Our head is round in order to allow our thoughts to change direction." Francis Picabia
RE: Help with MG-IIIa ext crossover - Roger Gustavsson 00:33:57 12/03/22 (2)
To me, it seems there has been an extra pair (the red/black one) of inputs added. Maybe these bypass some part of the crossover?

I think the bare wires are from the coils and these are insultated by a varnish.

Replacing a ribbon is difficult, wish you good luck...
- For his sake, I hope he's replacing the whole tweeter assembly, not just the ribbon in the existing assembly! - MWE 07:56:31 12/03/22 (1)
  THAT process appears to be an incredible pain in the butt. Replacing the whole thing is easy.
  
  Mark in NC
  "The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon
  - RE: For his sake, I hope he's replacing the whole tweeter assembly, not just the ribbon in the existing assembly! - joepark@gmail.com 03:08:41 12/04/22 (0)
    Yup, ordered the whole tweeter assembly - $150 + $350 core charge deal that Magnepan has.

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