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Thread: any info on Music Man 412-GS cab appreciated

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    Supporting Member eschertron's Avatar
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    any info on Music Man 412-GS cab appreciated

    Who has used or worked on this model? The one I picked up has been really 'worked over' and is no-where near clean condition.

    I found a deal on a 4x12 cabinet in the local Music-Go-Round today, less than U$100 for a closed-back cab with a Fender tag screwed onto the grille. Needs quite a bit of restoration, but since I want to build some cabinets (see this related thread) I thought I could start by re-tolexing an existing cab. I also have a quad of cheap speakers that need a home, so worst-case, an empty wooden box for 100 bucks to my door, why not? That's still the plan for the box, but I'm curious what others may know about the actual model, now that I've narrowed it down. The box looks to be all 7-ply except for the back panel (MDF?), and appears solid. I'll know more when I peel the tolex (already peeling) and inspect the joinery.

    After a bit of research - and only by following the speaker codes - I find the cab is a MM 412-GS from late 79 or 80. The speakers are all Eminence A12-GS (AlNiCo, with the big square magnets), and they Ohm out between 5 and 6 Ohms by my meter. I'm expecting 8 Ohm drivers from the documentation I've read. Is this typical of these speakers? So actually thinking of using the drivers...

    I don't want to abuse these things - there are repaired rips on one or two of the cones already - but would like to hear their character. I haven't put signal though the drivers yet; I am looking forward to trying these out, perhaps in an open-back 2x12. Seems more characteristic of that vintage of speaker, yes?

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    Don't forget the joker g1's Avatar
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    That is a typical DC resistance reading for an 8 ohm speaker.
    Not sure if those are the stock speakers? The cab is designed for their 130W head.
    Open back is not necessarily more characteristic of the era, most Marshall were closed.

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    Old Timer J M Fahey's Avatar
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    The big square yoke Alnico magnets were a MM staple, and are good (were good enough for MM and that means something ) but I would not make a 2 x 12" out of them, unless the head is 50/60W tops, they must stand not more than 35/40W each (maybe 50W each nominal, which is about the same).

    I would use the cabinet as is, with an upto 100W head.

    I bet sound will be loud and somewhat middy, I donīt expect any sparkle there, those speakers were literally heavier (larger coils, thicker wire, probably aluminum formers) than same era, say, Jensen/Oxford/Rola/Utah , the classic "Twin speakers".
    Do they have the oversized aluminum caps/domes?

    But you have them, so try them and report
    We might be surprised.

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    Supporting Member eschertron's Avatar
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    I've found no specific data on the speakers, only that their identification led me to ID the cabinet. One reason I suggested an open-back 2x12 is because I have one to try them in
    Having learned that they are not (or may not be) entirely similar to speakers loaded into open-back Fender enclosures of the time, I will brace myself to be underwhelmed. I was hoping for sparkle, though!

    Here's a quick picture of the amp with the grillecloth removed, and a close-up of a repaired cone. You can see a bit of rust on the rim of the speaker in the second shot. No other damage to the frame, though.
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    Question: the former is not visible without removing the dome? So i'd not be able to tell about the former's construction. But 'largish' paper domes.

    Here's a picture of the back of the driver. Note, for shits and giggles, the collection of mouse turds in the corner of the cabinet.
    Click image for larger version. 

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    Last edited by eschertron; 12-17-2017 at 11:02 PM.
    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    I guess I'm curious how the mouse got in and out, to leave you the presents.

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    Supporting Member eschertron's Avatar
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    Quote Originally Posted by Bill Moore View Post
    I guess I'm curious how the mouse got in and out, to leave you the presents.
    You and me both. I don't see a mouse-sized hole anywhere in the cabinet. I will find some time next week to clean up and strip the box, maybe find a defect I don't see yet.

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    If it still won't get loud enough, it's probably broken. - Steve Conner
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    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    Supporting Member loudthud's Avatar
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    I've got a pair of those cabinets. Could the model name be 412-65 ?

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    Supporting Member eschertron's Avatar
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    Quote Originally Posted by loudthud View Post
    I've got a pair of those cabinets. Could the model name be 412-65 ?
    Do you mean 'with mouse turds'?

    The only identifying marks (other than the "Fender" logo somebody attached to the grille) are the handle on top, the two unlabeled 1/4" jacks on the back, and the serial number plate under the grille. The serial number is S12422 if that means anything to anybody. I couldn't get a hit on it. It was the speaker make/model that led me to a MM user site, and the visual cues that allowed me to tentatively ID the cabinet. That's all I know.

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    If it still won't get loud enough, it's probably broken. - Steve Conner
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    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    Don't forget the joker g1's Avatar
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    Quote Originally Posted by loudthud View Post
    Could the model name be 412-65 ?
    They've included it with the re-issue stuff as 412-GS

    Click image for larger version. 

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    Supporting Member loudthud's Avatar
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    It was 412-GS. I dug up an old Music Man catalog from 1980. There was also a 412-B for bass. Different speakers and 3.5 inches deeper. Rated at 150 Wrms at 8 Ohms. In a couple of places they say these cabs had AlNiCo magnets, but those sure look like ceramic to me. Mine has the same speakers as shown in post 4 above. A12-GS was the Music Man speaker "type" according to a 1980 price list I have.

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  11. #11
    Old Timer J M Fahey's Avatar
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    Just enlarged the stamp sized picture on post #4 and those definitely are NOT Alnico but typical late 70's Eminence square ceramics.
    This is your picture , cropped and enhanced (click to enlarge) :
    Click image for larger version. 

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    This is exact same speaker,in an Ampeg V4 cabinet(click to enlarge):
    Click image for larger version. 

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    Same inside an Acoustic cabinet:


    inside an unidentified late 70's tube amp,


    those square ceramic magnets were a great idea, itīs way easier and more efficient to shear cut square pieces out of 5/16" steel in any size needed and with no scrap than having special round punch die sets for *every* size and the matching huge hydraulic press.

    Manufacturing a square magnet is same effort as making a round one.

    Somehow they stopped making them, date stamps shown go from 79 to 82 .

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  12. #12
    Supporting Member eschertron's Avatar
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    Quote Originally Posted by J M Fahey View Post
    Just enlarged the stamp sized picture on post #4 and those definitely are NOT Alnico but typical late 70's Eminence square ceramics.
    Somehow they stopped making them, date stamps shown go from 79 to 82 .
    Ok, I blame the internet for having me believe the "A" in A12-GS stood for AlNiCo
    It's good to have you weigh in, Juan, because you are a credible source. Ceramic it is. The date stamp is 7922 so 1979 is right where you put it on the timeline.

    I will do some A/B testing in a 2x12 open-back between these and the Celestion 70/80s that live there now. Will report back. So I can expect a more mid-forward 'British' sound than what I expect from a typical Fender offering?

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    If it still won't get loud enough, it's probably broken. - Steve Conner
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    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    Old Timer J M Fahey's Avatar
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    I think they will be darker/creamier than Celestions, but only testing can confirm.

    We might be surprised though.

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    Supporting Member eschertron's Avatar
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    So I swapped the speakers today. That cab is a 2x12 from a Crate V50 Palamino, "Palamino" labeled speakers that the collective mind of the internet says are Celestion 70/80s. What I found is that the Eminence A12-GS speakers have a lot less 'lower midrange' - in the range where you hear palm-muted strums as a "thump" - and seem to have a little more brightness on the top end, at least relative to the lack of lower frequency energy.
    I did some recording in order to AB side-by-side the sounds, the difference is fairly clear. I'm a keepin' the Emis in the 2x12 for now, and may put 2+2 in the MM cab to hear what that sounds like.

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    If it still won't get loud enough, it's probably broken. - Steve Conner
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    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    Supporting Member eschertron's Avatar
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    Some more pictures of the refurb. I took off the tolex today and inspected the cab. 7-ply baffle (mentioned before), and pine sides, top and bottom, but MDF back. I suspect the cab had sat in water (a few inches, maybe) at some as the MDF is soft along the edge where it attaches to the bottom panel. What should I use to stiffen up the MDF here? Superglue? Some kind of wood treatment?
    I'm going to have to get all the glue, etc., off the wood. 60 grit sandpaper? Or dare I use some chemical agent? Haven't noted too much info on the web about cleaning it up, mostly on how to tolex new wood. Anyway, proceeding slowly as it will be a while before windows can be opened for ventilation here in Ohio.

    Click image for larger version. 

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    note: The second picture shows the cab upside down, with the suspected water damage having dissolved the glue and allowed the tolex to peel. The third picture is a close up of the soft edge.

    edit: I did find a pretty detailed refurb at thegearpage.net

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    Last edited by eschertron; 01-20-2018 at 05:34 AM.
    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    Supporting Member eschertron's Avatar
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    So I tried acetone and a razor-blade scraper today, to get the few remaining pieces of tolex - rather, the fabric backing - removed from the cab. It worked kind of meh, I ended up with the micro-plane (actually some kind of cheese-grater-like rasp) to get the fibers off, leaving only a thin layer of glue. I'm hoping a jitterbug sander will get enough of all that's left to make the effort worthwhile.

    Click image for larger version. 

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    Still hoping someone will chime in on if CA glue is the right choice to stiffen the weak MDF corners.

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    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by eschertron View Post
    So I tried acetone and a razor-blade scraper today, to get the few remaining pieces of tolex - rather, the fabric backing - removed from the cab. It worked kind of meh, I ended up with the micro-plane (actually some kind of cheese-grater-like rasp) to get the fibers off, leaving only a thin layer of glue. I'm hoping a jitterbug sander will get enough of all that's left to make the effort worthwhile.

    Still hoping someone will chime in on if CA glue is the right choice to stiffen the weak MDF corners.
    On some Fenders in this state of detolexation, I've used a belt sander to get the glue remnants and other crud off, followed that with a "mouse" sander. You could use whichever type/brand of jitterbug/orbital sander you have available. 150 grit seems enough to get a surface that's both smooth and able to have tolex glue grip to it.

    On the cab corners, I'm not so sure cyanoacrylate (Krazy) glue would be the fix. I'd tend towards Franklin Titebond or its Borden "Elmers Glue" equivalent. You could add steel L brackets or 2x2 cleats on the inside to stiffen those corners.

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    Supporting Member eschertron's Avatar
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    Quote Originally Posted by Leo_Gnardo View Post
    On some Fenders in this state of detolexation, I've used a belt sander to get the glue remnants and other crud off, followed that with a "mouse" sander. You could use whichever type/brand of jitterbug/orbital sander you have available. 150 grit seems enough to get a surface that's both smooth and able to have tolex glue grip to it.

    On the cab corners, I'm not so sure cyanoacrylate (Krazy) glue would be the fix. I'd tend towards Franklin Titebond or its Borden "Elmers Glue" equivalent. You could add steel L brackets or 2x2 cleats on the inside to stiffen those corners.
    I don't think the cab is in such bad shape that it needs steel support. It's more of an issue where the (suspected) cabinet-water interaction has left the bottom edge of the MDF flaky and soft, not enough to radically compromise the structural integrity but enough to have let the surface 'let go' of the tolex adhesive and have the binder in the MDF start to leach out. Again, it's only along the bottom edge "corner" of the back panel.

    I'd like to try to reapply some of that binder, so letting some titebond soak in will be a good experiment. I thought I remembered something about edges and CA in a thread about routing corner beads on cabinets, but that could be old age talking

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  19. #19
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by eschertron View Post
    I don't think the cab is in such bad shape that it needs steel support. It's more of an issue where the (suspected) cabinet-water interaction has left the bottom edge of the MDF flaky and soft, not enough to radically compromise the structural integrity but enough to have let the surface 'let go' of the tolex adhesive and have the binder in the MDF start to leach out. Again, it's only along the bottom edge "corner" of the back panel.

    I'd like to try to reapply some of that binder, so letting some titebond soak in will be a good experiment. I thought I remembered something about edges and CA in a thread about routing corner beads on cabinets, but that could be old age talking
    In that case, regular wood glue will cost a fraction of CA glue. Good luck, I hope it works on your flakey MDF.

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    Supporting Member eschertron's Avatar
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    So after cutting some holes for proper 4x12 cabinet handles, I mixed up a batch of (approx) 1:1 titebond and water, and sponged it on along the edge in question. Hopefully it will hold the MDF from 'fuzzing' and 'flaking' long enough for me to sand and prep the cab for tolex.

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    If it still won't get loud enough, it's probably broken. - Steve Conner
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    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


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