A7 825 Cabinet Fixes?

[FriendlyVolcano]

I posted this question several days ago, but for some reason it's gone into the ether (maybe it was attachments), so I'll try it again. If you see query this pop up again, please disregard.

I've got some flat black A7/825 cabinets that have the usual screw holes, corner chows and gouges. Overall, they're in pretty good shape, but I want to make them get back to factory gray niceness. (There's some gray paint poking out on the back as well as on the horn support rail).

It occurred to me that I could skin the top, bottom and sides with 1/4" or 1/2" nice ply (glued and nailed) and use that has a refinish surface. It would save me the trouble of stripping/sanding/filling very carefully.

Apart from taking the cabinet profiles slightly away from stock, is there a definite positive effect by stiffening the box? Can anyone think of a reason not to do this?

And can anyone point me to photos where the bass horn has been reinforced from the inside? And any other reinforcement that make sense?

Lastly, assuming these were factory cabinets, is there anywhere in the interior where a date code/stamp might exist? I know that there were a lot of DIY, but just curious is there's an official stamp anywhere.

[gdmoore28]

Hi FV,

Skinning the outside of the cabinet on the A5/A7s has been done over and over again, and it's a good idea. If you intend to paint them, you can get a nicer finish (with lack of grain print-thru) by using 1/2" or 3/4" MDF. It really stiffens and adds mass to the cabinets. Even if you intend to veneer them, the MDF makes it an easier project. The only way I would go with plywood is if I had concerns with either weight or exposure to moisture.

As to re-enforcing the bass horn, there are lots and lots of threads here, on Lansing Forum, and Audio Karma discussing the process. Others with direct experience should be chipping in with their experiences and recommendations.

Would love to see pics of what you have, along with pics of the guts, too, if you have them. Never get tired of looking at them.

How do you intend to use yours? In home hifi? If that's the case, be sure to check out the many, many crossover mods you have at hand. Massaging the crossover and properly re-sizing the vent, along with re-enforcement, seem to be the most popular mods for making these sing in hifi applications.

GeeDeeEmm

[FriendlyVolcano]

Hi FV,



Would love to see pics of what you have, along with pics of the guts, too, if you have them. Never get tired of looking at them.

How do you intend to use yours? In home hifi? If that's the case, be sure to check out the many, many crossover mods you have at hand. Massaging the crossover and properly re-sizing the vent, along with re-enforcement, seem to be the most popular mods for making these sing in hifi applications.

GeeDeeEmm

Hi GDM, per your request, I've enclosed some snaps of the exterior/interior to give you a sense of what I'm working with. I'm not using the generic X-over I got with them and instead I'm running them with an Ashly XR1001 electronic crossover which gives me a lot of control of how the response and crossover points work. (It makes it really easy to mute stuff to test individual drivers.) I just updated the Emilar EA175 with NOS diaphragms so they match pretty well now. I'm not using them at home, but in my studio office, which is 25'x50'x14' with lots of glass, wood, & brick. Luckily, I can crank things as much as I please because we're surrounded by a parking garage!

I will definitely consider using MDF instead of ply. I think I want to avoid screwing stuff into the cabinets when they're redone, so I'm wondering if there's any downside to putting the horn supports (front and rear) on their own piece of plywood and just resting it on top. I'm using a subwoofer right now, but I'd like to retune the bass opening. Right now, there are 2 pieces, but I'll fabricate a new one out of one piece. Is the fabric usually just tacked to the back side or is there another arrangement?


altecA7_cab_before-1.jpg altecA7_cab_before-2.jpg altecA7_cab_before-3.jpg altecA7_cab_before-4.jpg

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I wanted to upload a few more pictures, but Hostboard has a 1mb photo limit. I don't know if there's a better way to post photos here, but Hostboard ain't cutting it for me. I've made my photos as small as possible, but perhaps I'm doing it wrong. Any suggestions?

[Elitopus1]

I like the white horns! Not too often you see 511b's painted that color. Very EV'ish.

You can make a horn sled that the horn mounts to. I am making them for my 805's right now. Basically just a piece of plywood that sits on top of the 825 cab. The horn mounts to the plywood with brackets or a front mount. It makes it easy to adjust the horn from front to back.

If I were you, I would brace the cabinets internally, and then just bondo the exterior imperfections. After that you could put a fresh coat of paint on.

There is a long thread on this forum about modding the 825/828 cabs. I found it useful when I first got my 828 cabs. It includes the reduced port size (usually 75 cu").

I replaced the two piece port section with a single piece of plywood, like you mentioned. Yes the cloth can be stapled to the back

IMG_6919.jpg

[FriendlyVolcano]

Is there a way to tell if the cabinets are factory or DIY? Any kind of stamps or markings to look for?

[GM]

I know that early on, Altec rubber stamped some with a 391xxx date code, but between [multiple] re-coatings and an increasing lack of QA in later years, about the only ~consistent way is panel junction bracing as they used pieces of horn flare off cuts [triangular] in every cab I've seen known to be 'factory'.

Note though that sometimes cabs were requisitioned locally by distributors, ditto Altec, so while all are technically 'factory', they don't necessarily match the drawings in detail.

In short, I'd worry more about its quality of construction than who made it, especially since any perceived prosound cab construction quality pretty much disappeared by the early '60s and why I built my own in '64 out of 3/4" marine grade plywood with hardwood bracing, so price wise, nowhere near sufficient enough to otherwise warrant the effort.

GM