DIY VOTT A7 Info/Advice

[camusmuse]

Hello all....

I'm relatively new here, but have been lurking for a while. I fell in love with Altec's at a young age listening to my uncles A7's powered by some SS McIntosh. I've been chasing that sound ever since. I had an english teacher with some khorns, sounded alright, but nothing like the Altecs. I've been building custom speakers since I was a teenager, and have always wanted to make my own A7's. But never could find the plans or someone willing to let me take apart their speakers. Needless to say I found the plans here, and I am VERY grateful.

So here's what I'm planning on doing.... Until I can get all the "correct" drivers, I have some that I think will work for the time being. For the horns, I have some NOS University ID-30's(I think, been a while since I've seen them in storage). For the lenses I am going to make some "smith" type wood horns. Is this combo a bad idea? It is just going to be temporary, but not sure for how long. For the woofers, I have some Altec 421 16h's(rubbing vc's) that I am going to have reconed to 8 ohms. I picked up some N800F crossovers on FleaBay, but will eventually like to move to an active crossover with dedicated amplifiers.

The enclosure's will be pretty close to the specs, with a little more cross bracing and corner bracing. One thing I am considering is using MDF instead of plywood. Or even plywood sides(for the oak veneer) and the rest MDF. On the surface, I would think that the different densities would be a bad thing, but I'm willing to try. For the curved pieces I was thinking of using 1/4 inch Louon, or other similar plywood. Also, what do you all think about using spray-on undercoating for sound deadening on the backs of the curved pieces or even the whole enclosure? Cost is a big consideration. I figure that a trip to the local "home center" for everything I need will be somewhere around $100.

Now I do have my heart set on at least one pair of A7's, but I am very open to suggestions for better sounding speakers, using the same or similar drivers.

Thanks again for the great site......

Nate

[garyl]

I have built a few pairs of enclosures but I am certainly no expert in the technical issues you might face.
Two things come to mind here that you might consider.

If what you are searching for is the sound of the Altec A-7, I would suggest you stick with the components of that very famous speaker and cabinets built as near to the specs of it.

When useing any form of OAK wood in speaker building it is not a good idea to place oak on the interior because of Tannic Acid which interacts poorly with the components.

For you curved parts I would be thinking along the lines of either kerf cutting a 3/4" panel for the bend or if you insist on the luan then bend and glue three thicknesses to the shape of the bend. I would then apply a veneer over the exposed surface as luan is not usually a quality product.

You will likely not be happy if you proceed along the path you are on, you can't get the sound of Altec A-7s by changing the cabinet materials, driver components and structural build. Your ideas and component selections might result in a nice sounding speaker however I seriously doubt it will be even close to that of the A-7 sound you want.

JMO.

Gary

[CONVERGENCE]

Hi,

If my memory serves me correct : you can have your 421 transformed into 416. GPA could inform you on this possibility.

Here is their site. Just click on the line below.

http://www.greatplainsaudio.com/

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[camusmuse]

convergence....

Thanks, I have an email out to them concering that very question, but have yet to hear back. I guess I just have give them a call on monday. I have a local "authorized" reconer that I like alot, but I realize who and what Great Plains is.

Garyl....

Thanks also, but I plan on sealing the inside of the cabinet. I dont that the oak veneer's acid will leech though.

As for the louon I was planning on doing two layers, as the spec sheet calls for 3/8" plywood on the bends. Actually the finish that we get here(not sure if it is different where you are) isnt bad at all, and I plan on priming and painting the outside(of the woofer horn and front) as well as the inside. The entire front will then be coverd will a removable grille/grille cloth. The oak veneer will only be on the sides.

I realize that "my" a7's will not sound exactly like the originals, but I will also have less than $450 total in the entire project. Most of that being in the reconed 421's, which could hardly be considered a bad investment. Someday I do hope to get all original drivers, but the current market is getting kinda ridiculous...IMO. It will probably only get worse, but for now I'm on a very tight budget, and have to work with what I have.

I also believe that the "sound" of the a7 is much akin to the "sound" of a tube amp. Not quite so accurate, but with complimentary colorations(even more so with a tube amp...wish i still had my dynacos). Even if they dont sound perfectly accurate and precise, they still sound very "good". Maybe my attempts to improve upon the a7's are fools' quests, but this stuff really is theraputic for me. Even if they end up sounding like poop....ill still like em....:)

[garyl]

I would not hold my breath waiting for an email response from GPA. Best to catch Bill on the phone but I do think Convergence is correct and your baskets can be made to suit your needs.

Luan is what we use here as underlayment on floors. It is justy cheap grade ply that at times looks pretty nice. You can also buy 1/4" real oak veneer plywood which I think would be much better material for your project. I have experimented with bending Luan and the top veneer tends to lift if stressed too far. It is still a good idea to make some shallow kerf cuts to help in the bending process.

Just some thoughts and info to help but not at all the final word on your project. Like I said before, you could be pleasantly surprised at the great sound you achieve and then again they could sound like POOP but as you correctly point out, they will be your Poop and you might still be able to work out the fine tunning.
I am very much like you in that this is theraputic for me so I have to agree with the DIY. My Model 19 clones came out great but don't sound much like 19s at all. I know of two people who really like them and that is me and the wife. Go for it and have a blast.

Gary

[camusmuse]

Yeah, luan or louon(whatever it is...lol), is what we use for underlayment as well. In fact thats why I'm gonna use it, I have enough scraps to get the job done. This really is gonna be an El Cheapo build. The bend on the A7's horn isnt that dramatic, so I'm gonna try it as it is. If kerfs are needed then so be it.

Has anyone swapped out the "stock" metal horns on the A7's in favor of wood horns? If so, what were your results?

[Cyclotronguy]

You can buy curved plywood as 1/4 rounds, 30 inch radius 5/8 inch thick which makes the curved portion pretty easy to fabricate and stout as can be. Not cheap, but a real time saver.

Cyclotronguy

[camusmuse]

Well that would just be cheating....lol, not to mention that I'm workin on the cheap. But I'll definitely keep that in mind as I just love to build stuff on the radius. Thanks!!!