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Magnepan MG IIB speaker rebuild

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Old 06-24-05, 11:11 PM Thread Starter   #1
Ryan T
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Magnepan MG IIB speaker rebuild


Hello everyone,


I recently got a hold of a pair of Magnepan MG-IIB planar speakers. They were in pretty good shape other than the "tweeters" being blown. In case your wonder what planar speakers I'll try to explain it to the best of my knowledge in a minute. Since the speakers are needing some work I'm planning to rebuild them. I need to replace the tweeter wire and do some touch up cosmetic work. I'm going to be working on them over the next month or so. Anyway I thought some of you guys might appreciate the speakers so I thought I would post some pictures. I'll try to get some of the rebuild process but It really shouldnt be to eventful. If I do take some pictures I'll be sure to post them!


So you may be asking what are Planar speakers? Well they are a very different type of speaker than the standard "cone" speakers you see these days. Instead of woofers and tweeters they use a VERY thin sheet of mylar to make the sound. The mylar sheet is stretched across a frame and glue in place around the edges. Then they run coated wire up and down the mylar to act as the "voice coil". Next there is a strip of magnets placed on one side of the mylar which will attract or repel the wires which are attached to the mylar sheet. Planar speakers still use magnets and a voice coil wire like normal cone speakers but instead of the actual cone (paper or plastic or metal etc) it uses the mylar sheet.

Magnepan is a company that has been making full range planar speakers for quite some time. They are a very interesting type of speaker in that they are dipole. Most speakers have one or two types of drivers in them (or more in some cases). One driver will handle the high frequency sounds (tweeters) and the other the low frequency sounds (woofer) In some cases you have midranges or midwoofers etc. The drivers are what radiate the sound. The cone moves back and fourth which generates the sound. In most cases with cone speakers the backwave (The sound which is generated by the rear of the speaker cone) is isolated so the person only hears the sound from the front of the cone. With most planar speakers the back wave is not isolated. It is called a dipole configuration. What that achieves is a much more open airy sound. The backwave from the mylar sheet will bounce off the walls behind the speaker and create a more open sound.


So now that you know a bit about the speakers heres some pictures .


Heres both Magnepan speakers next to my line arrays for size reference.



Heres the side of the Magnepan speaker.



Heres the rear. You can see the lines (wire) that run up and down the surface of the mylar. I know they dont look pretty but since these speakers were made in the 80's they have gotten pretty dirty over time.



And heres the crossover.


So I ordered a magenpan repair kit which contained a spool of 31 Ga coated aluminum wire (which is what the tweeter wire is) and some glue and other various bits. I will have to strip all the old broken tweeter wire of then use acitone to remove the old glue. Then I need to spray the sheet with spray adhesive and glue the new wires down. There is also a sock that goes over the "inner" baffle to hide the mylar sheet. The stock one is an off white but I'm going to buy the black replacment socks.

Heres a link to a site with a bunch of specs on a lot of magnepan speakers (mine are the MG-IIB's). There is also some pictures of what they look like with the stock sock on there.



Ryan

Last edited by Ryan T; 06-25-05 at 01:06 AM.
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Old 07-08-05, 01:04 AM   #2
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Pretty nice. I look forward to your listening results once they're fixed.

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Old 07-08-05, 09:20 AM   #3
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Magnepans sound great, but you need a sub that compliments them. Something that's extremely tight, otherwise it sounds weird. My friend has Magnepans coupled with a 12 inch ported sub, and the bottom end is very disjointed, and it's not the crossover either. Of course you know, he can't hear it because he bought it all =).

Good luck with the rebuild.
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Old 07-08-05, 12:16 PM Thread Starter   #4
Ryan T
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I do have my Tempest which can be sealed or ported. But these maggies arent really any slouches on the bass department. They are 45 to 16 Khz +/- 4 dB. The bass section worked fine when I hooked them up and I was really pretty impressed by the amount of bass output they had. Sure it's no subwoofer but they did sound plenty strong. I still havnt been able to start work o nthem yet :/. But next weekend I should havt the time to get them finshed if all goes well.


Ryan
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Old 07-08-05, 12:40 PM   #5
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no, I wasn't saying that, I just meant it's easy to overpower the low end with a lofty sub. That's just from what I heard though, it may have been the amp he was using etc..
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Old 07-08-05, 07:16 PM Thread Starter   #6
Ryan T
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Yeah i know what your saying though. Its very very hard to get a sub that is "fast" enough to match with the speakers. Its the same problem that Martin Logan has. They use electrostatic speakers matched with cone woofers. I never really felt they sounded very smooth. From what I've heard magnepans are just as hard to match a sub with. But from my testing so far the bass seems very good so I probably wont bother with a sub.


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Old 07-08-05, 08:26 PM   #7
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How about dipole subs? I think they might be able to match them decently, assuming you have enough displacement. Either that or a low Q sealed setup.

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Old 09-02-05, 08:39 PM Thread Starter   #8
Ryan T
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Ok, thought I'd dig this thread up . Since I had some extra free time today and tomorrow I decided to quite slacking and rebuild these magnepans! I already had the Magnepan rebuild kit which has everything needed except 3M spray adhesive and acetone. So I headed over to walmart to pick that stuff up and got some latex gloves as well. I didnt want glue and other crap to get all over my hands while doing this.

Heres a brief recap of what I did to rebuild them.

I dragged the two speakers out into the garage and started by pulling all the old corroded tweeter wire off. It actually just fell off in most places heh. Once that was done I cleaned the surface with acetone and wiped it down. The next step was to spray the area with 3M super 77 spray adhesive. It starts to tack up pretty quick and this stuff is strong! Once the adhesive is down you have to run the wire up and down the lenght of the panel while keeping the wire in between the magnets. After that you connect the wires to the crossover and test it. Once that was completed all thats left is to apply two coats of milloxane (sp?). Once thats dry your home free . Overall it takes about an hour and a half to do one speaker.


So now onto the sound! I've only completed one speaker so far. And the only testing I did was outside so I'm sure it'll sound much different in room. But I gotta say these speakers are incredible! They are advertised as being able to cover 45hz-16Khz +/- 4 dB and I gotta say I didnt think they would be able to paly that low with any power but all I can say is wow. I've never heard a full range speaker with as much presence in the bass region and this was still outside! The high end is a little rolled off (which could be due to it being outside) but not bad at all. The transition from the woofer section to the tweeter section sounds really good. Overall my jaw dropped a bit when I fired this guy up

I cant do a serious review of thier sound quality untill I can get them in my room though. They are dipole speakers so the sound radiates out of phase from the back of the panel. That out of phase sound should reflect off of the walls behind the speakers and give them a very big sound. The inital impresion is very very good though. I'll have to do some major A/B/C testing between these and the AV 1's and Line arrays. I'm gonna be working on the second one tomorrow morning. So I should have both ready for an in room test mid afternoon on Sunday. I'll post some pictures and give a more in depth review of the sound once I get them both finished.


Ryan

Last edited by Ryan T; 09-02-05 at 09:20 PM.
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Old 09-03-05, 12:04 AM   #9
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missed this the first time around

i remember you talking about them though

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Old 09-03-05, 12:13 AM Thread Starter   #10
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Man, I cant wait to get these both running . I was just thinking about them though. Its hard to beleive that speakers from 1984 still sound good heh. I mean granted I did just replace the tweeter section, its still the same design just new wire. So this is likely preatty close to how they sounded in 84.



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Old 09-04-05, 05:15 PM Thread Starter   #11
Ryan T
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Ok, well the Magnepans are finished . The glue is all dry and they are ready to get new fabric socks (I'm gonna probably order new black ones next month). Heres two quick pictures.


As you can see the tweeter section had to be all cleaned up. The woofer area still looks pretty bad. If I ever get around to replacing the woofers I'll just clean the whole mylar sheet. But since it really doesnt seem to have any impact on the sound its purely cosmetic.

And heres both of the speakers in their current position.

Now onto the sound. They definately sound very open in my room. I think the room is a bit small for them though :/. Everything comes through crystal clear but when you have them up really loud with rock music it starts to get a little jumbled. They sound almost as detailed as the AV 1's. But they also have the same big sound as the line arrays. Its kind of a best of both worlds situation . I still think the AV 1's edge these out in terms of absolute clarity and detail but they arent far behind. The line arrays worked very well with live music and jazz. These also do well with that type of music but they handle rock much better than the line arrays. Were the line arrays started to sound muffled and jumbled up sooner (mostly due to the crossover and tweeters in the line arrays). The only real short coming I can hear is the highest treble range. With some recordings the cymbols sound a tad dull. You can listen to music and pick out each instrument easily. They also play VERY loud before starting to show signs of distortion. Unfortunately they arent very effeicent at around 84 dB 1/w/m so they are the hardest to drive.

So if I had to rate all three speakers on say four different aspects of their sound (1-10, 10=best) they would place like this


----------------AV1---Line Array---Magnepan

Dynamics-------5--------10------------8
Sound stage----7---------9-----------10
Imaging--------9---------5-------------7
Clarity---------10---------6------------8

The line arrays have a HUGE advantage in dynamics department. They are very easy to drive and can play incredibly loud without distortion. But they really need a new tweeter section and lower crossover point to keep up in the other departments.

The AV 1's as always have incredible clarity with just about any music. They dont have the ability to move nearly as much air as the other two but they make up for it with there awesome clarity. The sound stage is very good with these speakers but they cannot create the same big open sound as the line arrays or Magnepans.

The Magnepans are probably my new favorite speakers . They dont quite have the same clarity of the AV 1's but the sound stage is really something else. They have the broadest sound stage by FAR. I think the fact that they are diploe helps that a lot. The clarity isnt quite up to the AV 1's but very close.

So that concludes my highly subjective mini review . They seem to take the best aspects of the line arrays and the AV 1's and combine them into one really sweet package. I wish they had a tad bit more presence up in the higher treble ranges though. Most the newer magnepans dont use the same mylar sheet for the tweeter and woofers. they switched to a full length ribbon tweeter which I think fixed the high end response. But none the less, overall I'm very very impressed with the Magnepans.


Ryan
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Old 06-19-11, 01:11 PM   #12
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major bump, but i think i might be doing the same thing soon. and i think we have the same problem.
where did you order the repair kit? the manufacture? apparently this was a common problem with the speakers

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Old 06-19-11, 03:48 PM   #13
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You can get the rebuild kit right from Magnepan. Youre going to need a beefy amp for those...atleast 150wpc at 4 ohms. They sound excellent, but you may need a sub. They have a fast bass response like a horn enclosure...so dont expect earth-shaking bass.
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Old 06-19-11, 11:21 PM   #14
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Thanks Sir Barton, I'm highly looking forward to rebuilding these speakers as they are going to be given to me for free. the conditions were that we rebuild it, and give it a new home. I'll have to read up, but these are supposed to be positioned a certain way. I guess ill also have to also read up on some amplifiers when i have free time since you mention they require a lot of power.

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