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MGIII rebuild

76.167.189.8
Posted on January 6, 2011 at 20:08:21
IEaudiodude
Audiophile

Posts: 2814
Location: So Cal
Joined: February 11, 2010
 By chance has anyone one here used foil rather than wire to rewire the Midrange section on their MGIII's or any other maggies that had wire sections ? I got a sample from Magnepan and it looks like it wouldn't be to hard to lay it out straight and make decent corners, would it could it work in place of aluminum wire ? Just curious and thinking out loud again !
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RE: MGIII rebuild, posted on January 7, 2011 at 01:59:38
Roger Gustavsson


 
A round or flat section piece of wire is not important, they still seems to have a similar crossectional area and are still in about the same magnetic field. Perhaps, a flat one could better be glued to the Mylar? That is important!

 

Foil has 3db less output, posted on January 7, 2011 at 05:08:43
tyu


 
I have worket with the Magnepan Foil, Dont do it, All the Foil has 3db LESS output than wire,it eze to work with i have done Tweeters on SMGa an MG1.
The wire is eze lot of room to work with.The 1.7 Suck Power an sound Flat an lifeless, to me,Goodluck on the 3.7 that well kill the Magnepan for me!

 

RE: MGIII rebuild, posted on January 7, 2011 at 07:21:34
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 If You are going to make the foil transition You have to make REALLY certain that You don't use too much glue.
The more glue You put on the less will the exact sound reproduction be.
It ads weight!

The aluminum has to be as close to the plastic it can possible be!

I know it's hard to do that when the polyester is already there and stretched. It's hard for Magnepan too as You can see on pictures.

Good luck!

PS. High output level is not a self written answer to good sound quality!
There is a damn good reason for using foil instead of wire. hehe
The one who succeeded was the one who didn't know it was impossible.

 

RE: MGIII rebuild, posted on January 7, 2011 at 08:08:02
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Make sure you use the appropriate thickness of foil. The cross-sectional area of the foil has to be the same as the cross-sectional area of the wire that was there to maintain the right resistance. If you do that, you'll also maintain the original mass if the original wire was aluminum. If the original wire was copper, you may have to add mass to keep the resonance frequency from shifting.

 

Say what you well the Foil is 3db diff than the wire!, posted on January 7, 2011 at 13:57:23
tyu


 
The only foil or wire that have came from Magnepan ,The way that magnepan got into the Foil was was to put the polepeace in back,your not doing that are you? If you have the foil from Magnepan it not like the true ribbon foil it tuff it allmost as tuff as the tweeter wire,an for puting the foil as close as you can to the mylar,you can get it close a neff Not to drop 3db. Even if you could turn the mid around an you cant well you can turn the speakers around,but then your crossover well put the foil mid off,it well work an it eze the foil was $7.50 for a nuf for the pr of tweeters go for it or you well never no!

PS.An as far as the Sound of the 1.7 sucking this is just one mans o-pine

 

RE: Say what you well the Foil is 3db diff than the wire!, posted on January 7, 2011 at 14:36:43
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I'm not the person rebuilding the speakers. Not sure why the output would drop 3 dB, though, *if* you choose foil with the same resistivity! If you don't make sure that it has the same cross-sectional area as the wire, yeah, the level could easily drop. It also has to have the same mass, but that will happen automatically if you replace aluminum with aluminum.

 

what the inquiring idiot wants to know, posted on January 7, 2011 at 19:26:41
wazoo
Audiophile

Posts: 4062
Location: Middle GA
Joined: December 6, 2006
 The question burning in my head is: Why didn't Magnepan make the transition to foil years ago if it were as simple as is being implied?

Something about this doesn't compute (in my small mind anyway). The QR tweeter has been around for a while, so either Magnepan questioned the benefit of extending that technology to the mid/bass driver(s), or there was some impediment which had to be dispatched. If the former, what changed their minds? If the latter, what was the hurdle and why did it take them so long to clear it? As we are not privy to the actual reason, we can only hazzard guesses.

I don't raise this question from the perspective of the physics involved, so please humor me if it's a stupid one. It seems logical to wonder about it, given the intervening years between the introduction of the QR tweeter and the .7 series. In this case, logic is the only tool at my disposal. Think about it. They have all of the raw materials, engineering and manufacturing expertise, and, I would imagine, curiosity to have been experimenting with an all QR speaker for years, yet it took a dozen years for the 1.6 to give way to the 1.7. Why?

---

My other question is: If the change to a QR driver doesn't carry the advantage of lower mass, how is it an improvement?

 

RE: what the inquiring idiot wants to know, posted on January 7, 2011 at 19:47:55
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 The second question's easier, because I know at least part of the answer -- the foil covers more of the mylar's surface, so it does a better job at controlling the diaphram motion. Also, based on some experimental tapping, the quasi ribbon seems to mechanically damp mylar resonances more effectively than the wire. But this may not be fair since I was comparing the MMG tweeter to the woofer, with its much wider conductor/magnet spacing, rather than quasi ribbon and planar magnetic tweeters.

Otherwise, all I know is that Magnepan has always been slow to make changes, and that there was in addition an unusually long hiatus between upgrades. Perhaps it had something to do with the changing of the guard, as Jim Winey hands the company over to a new generation?

 

RE: what the inquiring idiot wants to know, posted on January 7, 2011 at 23:53:58
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 There is one thing that I do know.
That is that it's more or less impossible to make a fully foil bass panel with the manufacturing and design that Magnepan uses.
It is all backwards.

To make a wire bass membrane with the manufacturing and design of a foil bass design is also impossible.

So I am certain that difficulties lies in their manufacturing process to make a full foil membrane.

I have tested and tapped on my Tympanies and found a very distinct metallic ring to it. Maybe this is only on these models but it's not present in any way or form in a real foil bass panel.

(I have both Magnepan and Apogee speakers)
The one who succeeded was the one who didn't know it was impossible.

 

The Foil Has to be done By hand!, posted on January 8, 2011 at 04:48:54
tyu


 
The wire Could be set up on a Jig.The foil has to be done by hand,tooling up no,but it eze to see if you read MR Gunns thinking on the 1.7,the only speakers the SMGa Crossover Dose not give the 3-4 db more output than the stock setups.

The SMGa crossover {THANKS TO MR GUNN} is the ONLY thing that i came back to Magnepans for after 10years Hopeing that the Magnepans could be ran by 60-80watt Tube Amps.

I think that the foil has to much mass,but the wire is to brite if the polepeace is put in the back, i found that in the 80s thay had no where to go but foil, but then only one or two people well do all the hand panel foiling.

Get Some an see, $7.50 for nef. for a pr of speakers

But 1.7 sound bla,bla, to me, even after 500hr.I wood not trade my MG 2.5 for 5pr,BUT THAT ME,

I too have had Apogee,But ran them with older Krell KSA 250 an KSA150
an thay sound dark,best bass i have ever had.

 

RE: The Foil Has to be done By hand!, posted on January 8, 2011 at 05:03:53
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 Yes, threading the wire manually on a jig is easier than hand cutting foil.
But then again, today You would probably etch the foil. hehe

A wire that has (let's say) 4 Ohm does NOT have less mass then a foil that has 4 Ohm. That's a fact.

The thing that Magnepan wants to control better is the membrane motion itself.
Using wire You only control that specific area that the wire is adhered to. The rest between is passive and will have and uncontrollable motion and resonance, doing it's own motion that is not a part of the musical program.

Foil will control most of the panel apart from the tiny and narrow separation slits.


The one who succeeded was the one who didn't know it was impossible.

 

RE: MGIII rebuild, posted on January 8, 2011 at 07:48:18
IEaudiodude
Audiophile

Posts: 2814
Location: So Cal
Joined: February 11, 2010
 Well I decided to go ahead and buy the foil and give it a try, I figure it isn't much money invested and the worse that can happen is that I will use up more Acetone & time removing the foil to redo it with wire ! I experimented a bit with some scrap Mylar and the foil sample that Karen sent me. With one of my detail spray guns I was able to apply a very minimal amount of NF30 To the Mylar, Just enough to get the foil to stick securely.After it cured I sprayed on 2 light coats over the foil to laminate it to the Mylar. I was very surprised how thin I was able to apply the 1st coat,I then applied two coats over the foil to laminate everything the mil. thickness is minimal and should add very little mass to the speaker. As long as I can get the impedance correct I think it will work out well. I will take pics and detail my project for any other DIY inmates to reference if it works out !
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RE: MGIII rebuild, posted on January 8, 2011 at 07:58:27
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 Good job!

I will look forward to those pictures!

Cheers!
The one who succeeded was the one who didn't know it was impossible.

 

Good Job It well Work, posted on January 8, 2011 at 08:18:18
tyu


 
You say

Just enough to get the foil to stick securely. {This is what Magnepan Dose.}

After it cured I sprayed on 2 light coats over the foil to laminate it to the Mylar, {Not what Magnepan dose},Look at the pic of the 1.7 on the Fourm . The foil is eze,er than the wire to put on, Hay i did it you well have no prob.Put one cote down Play the speaker,Then put the two more on.

 

The Foil itself has output, posted on January 8, 2011 at 08:26:32
tyu


 
I found the foil itself put out sound thats why the SMGa that i did frist
i put cotes on Top of the Foil,less output the the other pr i just put the foil an it had more output,but you have to get foil ask karen,
Thanks

 

RE: Good Job It well Work, posted on January 8, 2011 at 08:34:47
IEaudiodude
Audiophile

Posts: 2814
Location: So Cal
Joined: February 11, 2010
 The two coats I applied were on a piece of scrap I was experimenting with just do get a feel for what it will work like when I start applying it on the speaker. After you glued the foil on you said you played the speaker then put on more? Why did you play the speaker before you finished applying the 30NF ? Did you have any problems keeping the impedance where it should be ?
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RE: MGIII rebuild, posted on January 9, 2011 at 11:25:16
tyu


 
Here Are the Runs i did, Just like 1.6.4 loops on the Tweeters

Mr GUNN
Instead of using the term segments people generally say loops which counts as the up and back down. So yes, the 1,7 ST has 1 loop, the mid tweeter 3 loops and the midbass 13. That is exactly how the 1.6 is except the tweeter is those last 4 alone and no, it did not appear to me that the magnets were any different.

I was Saying to you, Put just the QR foil on top of the Mylare,no top cotes. I got less output but.............. it your game cool ,the QR foil is eze,the wire can move on you,the QR Foil stays were you put it!

 

"Foil will control *most* of the panel, apart from the narrow separation slits" - IE. ..., posted on January 9, 2011 at 18:42:50
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 very little of the mylar will be free to, as you say, "do its own motion" instead of playing the music. :-)) (Unlike the round-wire drivers, where there is lots of "free" mylar.)

But I suspect the magnets strips have different spacing with the QR foil than they have with the round-wire? (So you can't optimally retrofit QR foil to a round-wire driver.)

Someone who has both 1.6s and 1.7s needs to examine them and report back for us. :-))

Regards,

Andy

 

RE: "Foil will control *most* of the panel, apart from the narrow separation slits" - IE. ..., posted on January 9, 2011 at 20:53:02
IEaudiodude
Audiophile

Posts: 2814
Location: So Cal
Joined: February 11, 2010
 That's a very good question Andy , All I have done so far is take some 1/8" automotive Pinstriping tape and lay it out over the Mylar to see how the clearances look just as a mock up . So if anyone out there can tell me the measurements between the magnets on a pair of 1.7's or 3.6's I could definitely use the information before I get to the actual gluing stage. Also is the Midrange foil on either of those laid out in one long run or are they like my MGIII's and laid out as 2 parallel runs of wire. Gotta keep that impedance happy ! Damn Andy ! You didn't warn me that the MGIII's were going to draw me in and turn them into a major rebuilding project !
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"Is the midrange foil laid out in one long run or ...?" ..., posted on January 9, 2011 at 21:02:52
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 That is indeed the key question. :-)) With the 31g round-wire used for the IIIa mids, the resistance of however many feet you need to lay half the width, is 6.4 ohms. So having 2 in parallel gives you a "reasonable" 3.2 ohms ... whereas if they had just laid it as 1 big loop, it would've come out at nearly 13 ohms! :-((

So the issue with the foil is ... is it the same cross-sectional area as the 31g round wire? If it is ... then you would need 2 loops, just the same as the round-wire. But if it works out to have more cross-sectional area, its per-foot resistance will be less and so they might've made it 1 long loop!

Regards,

Andy

 

RE: "Is the midrange foil laid out in one long run or ...?" ..., posted on January 10, 2011 at 04:24:05
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 It's of course very important to get the right foil thickness and get the foil width right for a specific resistance.

The placing is ALWAYS between the magnets.
The one who succeeded was the one who didn't know it was impossible.

 

Magnets are the same, posted on January 10, 2011 at 04:26:20
tyu


 
one more from MR Gunn

I have a few SMGa's with bad tweeters I "one day" plan to refurb with QR foil instead if I ever have free time. One DIY'er emailed me about it a year or so ago and he then did it and reported it worked out fine. I wish half the people that write and tell me stuff would post it here, but they don't. The magnet lay on the 1.7 looks to be exactly the same as the 1.6.

 

RE: "Is the midrange foil laid out in one long run or ...?" ..., posted on January 10, 2011 at 10:05:30
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Also, you want to keep the mass the same so the resonance comes out right and the efficiency stays the same. That means that if the wire uses two loops, the foil will have to as well.

 

RE: "Is the midrange foil laid out in one long run or ...?" ..., posted on January 10, 2011 at 11:43:13
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 Not so, Josh. A single 50' length of foil resulting from 6 loops will weigh the same as a pair of 3-loops ... as each of the latter will need 25'.

Regards,

Andy

 

RE: "Is the midrange foil laid out in one long run or ...?" ..., posted on January 10, 2011 at 13:27:34
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 But you're overlooking your own argument! The impedance changes when you parallel them. To maintain the 3.2 ohm impedance with a single length, or two half lengths in series, you'd have to increase the cross sectional area, increasing the mass. So you're locked in -- you have to use the same topology and the same cross sectional area they did, because once they'd picked a target impedance, a target mass, and a wire material, and determined the total length of the conductors, the series/parallel decision was made for them.

 

Yes - correct :-)) nt, posted on January 10, 2011 at 14:26:47
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 .

 

RE: MGIII rebuild, posted on April 3, 2014 at 01:35:07
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 Are there any Pictures of this rebuild?

I was talking to Sheila about using foil for my Tympani IVa mids. She asked some technicians about what gauge would be needed but they had no answer. I ordered the same foil as used for the mids of the 3.7. I have not got it yet but I hope they send me the right one.

 

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