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In Reply to: RE: Maybe a solution posted by neolith on January 21, 2016 at 11:23:41
I can't find that link would you please repost it?
I wonder if those wire were swapped it would cause amps to shutdown?
Thanks!
Follow Ups:
Here is the official diagram from Magnepan:
Note that speaker 1 (Left) is wired differently than speaker 2 (right) but it would be quite easy to switch the blue and white connections. This would send the signal through the woofer without a LP filter and leave the tweeterunconnectedwith a very sharp bandpass @ 1000 hz.
As far as causing the amps to fart, I am not sure. The woofer is almost purely resistive so the impedance would be constant and independent of the frequency. The operative word is "almost" and it is possible that at some frequencies the impedance does drop causing an issue for some amps, especially integrated amps which are notorious for not being stable at low impedance. Normally the series inductor would raise the impedance at high frequencies and counter-act the drop. Another explanation might be that the DCR of the inductor (about 0.4 ohms) is just enough to keep some amps from crapping out and its loss is sorely missed.
Edits: 01/21/16 01/21/16
That make perfect sense except, if I'm looking at this right, with the blue and white wires swapped, the woofer would have the fuse in the circuit. If I pull the fuse the woofer still plays.
I did get the tweeter to make noise with an old analog ohm meter so it seems good.
I have a miniDSP 10x10 Hd, tomorrow I'll set up a 2500hz high pass filter and send some audio through the tweeter and make sure it's ok, if it is I'll pull the grill cloth and see what the heck is going on... bye bye warranty.
Thank!
You are right about pulling the fuse (or the attenuator jumper). Back to the drawing board : <. You may be able to see enough with just opening up the back panel without removing the socks. Good luck and let me know if you get a solution.
There are several freeware function generators that you can use to play a specific sine (square, triangle, etc) wave to test the speakers. Click here to download a very basic app from Phil Marchand . I recently found a program from Daqarta that does all sorts of things for audio testing. If my theory had been correct the tweeter would play ok around 1000 hz but would drop off significantly at higher and lower frequencies.
Wow, fried inductor! The wiring doesn't quite match that old drawing, guess they made changes since 1999.And it has a 12uF in parallel with a 100uF cap which at first glance that looks like a first order crossover at 350Hz for the tweeter. I'll have to sort out the wiring and see what's going on.
Tweeter is good, that's a relief.
I have an Outlaw Audio 5 channel amp I think I'm just going to bi-amp these.
Edits: 01/22/16
WTF! It is nearly impossible to fry a speaker inductor with an audio amplifier. Also as Davey says, that 100 uF cap does not belong there. Also at first glance it makes no sense that you can get sound out of the woofer if the inductor is open. First thing, check the other speaker to see if it is was modified as well. Since the speakers are new, I would call Magnepan on Monday and ask to talk to Wendell. He does visit this forum on rare occasions so he can take a look at the picture. Give him the serial numbers so he can trace the sales history on these speakrs. It's very weird because while Magnepan takes the MMG back on their 30 day program, they should have tested it before re-sale. They still may make good on the warranty and even pay for shipping or at least send you a new inductor if you are up for DIY. Finally if you do go DIY think about by-passing the fuse - it really serves no purpose and as you can tell your tweeter is able to take a lot of abuse as it is being driven as low 350 hz without damage.
The other MMG has that 100uF cap in it too. I've found two other people that had that 100uF cap. I almost suspect Magnepan is adding these caps.
The staples on the bottom look perfect, undisturbed, if these speakers were modded either Magnepan re-socked them or the guy that modded them hit every staple in the same hole.
They didn't offer free shipping back and I forgot to ask, the 4-6 weeks turnaround time plus almost 2 weeks total shipping time got me in a tizzy. These are my only speakers. And, if they deem this as my fault the repair costs are outrageous.
I've talked to Wendell a couple of times and he's been no help at all. He made it clear that he was marketing not technical and connected me to the returns dept.
The inductor is not open it's just half melted down which no doubt drastically changed it's value.
I'm just going to bi-amp them with a miniDSP 10x10 and an Outlaw 5 channel amp.
I'm hoping to upgrade later this year but I doubt it'll include Magnepans.
Well, if this is a Magnepan modification to the MMG's I'd like to understand it or at least have them acknowledge it.
The evolution of your particular pair of speakers is puzzling, to say the least. :)
Converting the MMG's to a generic electrical crossover has been done previously....but not in this way....to my knowledge.
Cheers,
Dave.
The blue wire should have been going to where the brown wire is, not to the inductor, and the brown wire should have gone to the capacitor. The tweeter and woofer are wired in inverse polarity and the person who modded that crossover probably tried to put them in the same polarity (which would have been correct with the tweeter set at 350 hz).
To correct things - lose the 100 uF cap, replace the inductor, connect the blue wire to the input post (where the red wire connects) and move the brown wire to the bottom of the 12 uF cap.
Somebody has modified those speakers. :)
That large a capacitor pushes the electrical HP way lower than it would have been stock. I don't understand the thinking of that modification.
Dave.
Here's another guy that found a 100uF cap in his MMGs, note the year, 2014, I bought mine in Sept. 2015.
http://www.audiocircle.com/index.php?topic=125012.0As crossovers go it makes more sense than a 12uf except that it's way too low of a crossover for the tweeter.
2.2mh @ 4ohms is around 300hz low pass
12uf @ 4ohms is around a 3300Hz high pass
What about the frequencies between 300hz and 3300hz? Maybe the bass panel has a rise in SPL above 300hz?
Edits: 01/22/16
The 300Hz/3300Hz spread between the electrical filters is correct. The acoustic response of the drivers fills that "void" and yields a nice overall response.
It appears that somebody decided the Magnepan network was incorrect because it deviated considerably from a "textbook" design and they decided to lower HP filter to "correct" it.It seems you've identified one issue, but other problems look likely.
With the schematic at hand and continuity checks of the individual transducers you should able to deduce the other issues.I forgot about that thread on AudioCircle. :)
Dave.
Edits: 01/23/16
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