SMGa Crossover Schematic and Drawing - diyAudio
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Old 20th February 2016, 10:24 PM   #1
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Default SMGa Crossover Schematic and Drawing

I'm looking for a schematic and a drawing showing the way the original crossover connects to the separate tweet/woofer connectons on the SMGa. I rewired for active XVER and didnt take pic. Do the tweeter and woofer go to the same solder blobs or are they different on the R/L.
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Old 21st February 2016, 07:11 AM   #2
andyr is offline andyr  Australia
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Quote:
Originally Posted by Freecrowder View Post
I'm looking for a schematic and a drawing showing the way the original crossover connects to the separate tweet/woofer connectons on the SMGa. I rewired for active XVER and didnt take pic. Do the tweeter and woofer go to the same solder blobs or are they different on the R/L.
Many Maggie schematics are here:

MUG Tweaks


Andy
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Old 23rd February 2016, 01:19 AM   #3
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so can anyone tell me which components are for the tweeter and which for the woofer. Is the capacitor in the woofer circuit and the inductor in the tweeter circuit?
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Old 23rd February 2016, 01:32 AM   #4
andyr is offline andyr  Australia
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Quote:
Originally Posted by Freecrowder View Post
so can anyone tell me which components are for the tweeter and which for the woofer. Is the capacitor in the woofer circuit and the inductor in the tweeter circuit?
The SMG schematic is under the heading "Reference Schematics". It is a 1st order series XO instead of the parallel XOs used on most other earlier Maggie models. So both the cap & the inductor are in the same circuit - and connected together - but:
* the inductor rolls off the HFs of the bass driver, and
* the cap rolls off the LFs of the tweeter.


Andy
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Old 23rd February 2016, 01:55 PM   #5
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OK thank you. I removed tweeter wiring a year ago and didn't note what wires went where. Used with active Xover and biamped and now ready to make it stock again. Looking at the schematic seems a little confusing. I think because it is a series xover.
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Old 8th April 2016, 06:18 AM   #6
bwaslo is offline bwaslo  United States
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I just got a pair of SMGa's off craigslist for cheap, fully expecting them to need rewiring. But, surprise, all the wires are intact, no sign of pitting or pulling away! No sign it was ever redone either (or if it was, they kept the wires dead straight). I did have one tweeter silent and intermittent contact on the other speaker, happeing inside the solder blob terminal connections that connect the aluminum wires to the copper wiring and crossover stuff. Evidently it oxidized itself into insulating, or got embedded in a flux blob? Anyway, pulling the aluminum wires out using a wide tip 750F soldering iron, cleaning the wires gently with 600 grit sandpaper and pushing it back into the melted soldering blob was all it took, they play as good as new. They even measure reasonably flat, with the signature dying high end above 12kHz. The panels are like 30 years old, I'm shocked! They need new socks, though, so I have a set on order.

The schematic for mine is a little different (though functionally the same) from the one linked above. (or maybe the left and right channels are wired differently? If that's it, then this is for the Left channel):

Click the image to open in full size.
The 100m Ohm resistor is a fuse.

Here's a measurement (quick, there's stuff behind it and it's not more than a few feet from a wall):
Click the image to open in full size.
Never realized it, but these things are roughly linear phase!?!

I've since peaked up the HF using a MiniDSP, improves the sound tremendously.
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Last edited by bwaslo; 8th April 2016 at 06:24 AM.
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Old 8th April 2016, 09:07 AM   #7
tyu is offline tyu  United States
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If the Panels glue is tacky .....take a can of spray pant....put a lite coat on the mylar.....over the wires.....the dryers in the spray pant...well dry the tackiness up ... an hold the wire tight to the mylar....an it also helps seals the wire from air...good for 30 more years.....
I re-worket minny maggy panels.....I use white spray paint...but it your call........I use the $1 spray pant...it the dryer in the paint were after here....this is a trick Peter Gun came up with......work great.....over at Magnestand....he allso has a crossover change....for the Smgas
e-mail him...hes vary helpful....
Magnestand - Where Maggies Live And Breathe
As for your SMGa........I had 5 pr at lest....only better pr...well to me .....
are the MG1c...but the panels 10" tallers.....I think these type sound so good after owning over 15 pr of maggys...is these are the only ones that use just one button ...that hold the mylar down...All others use 2-4 buttons....more buttens changes the sound......good luck

Last edited by tyu; 8th April 2016 at 09:17 AM.
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Old 8th April 2016, 03:49 PM   #8
Davey is offline Davey  United States
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Bill,

The first-order series crossover in this model is pretty much "textbook" both electrically and acoustically, so a nearly flat phase response would be expected.
Is R4 in your schematic 100 milli-ohms? I don't understand the reason for R3 if so.

edit:
Sorry, just realized R4 is the fuse. Ha!

Dave.

Last edited by Davey; 8th April 2016 at 04:03 PM.
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Old 8th April 2016, 09:36 PM   #9
bwaslo is offline bwaslo  United States
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Davey,

Yes, but if you do a straight first order crossover (series or parallel) with most drivers, say a cone woofer and a dome tweeter, you won't get flat phase response (or usually flat magnitude either) because the drivers are narrow band and their voice coils won't be aligned. The electrical network might be first order, but with driver rolloffs and delays the effective acoustical network will usually be far from it.

I hadn't realized the Maggie panels had such wide bandwidth that their rolloffs don't interract with the crossover, a rare occurrance.
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