A7 built

[fabrice baucher]

i'm looking for plans to built A7 bass cabinets ... and advice if some did the same... and what speakers could fit with ?

fabrice

[[email protected]]

http://www.lansingheritage.org/images/altec/plans/1960's-lf-design/page14.jpg

[Charles Chance]

I built mine many years ago. 5/8" ply, Elmer's wood glue, many slot-head screws (would use Phillips head if I had it to do over). You will be doing some puttying. I tried several products and settled on Durham's Rock Hard putty. It's a beige powder, mixes with water, quite sandable in 2-3 hours, and dirt-cheap. The horn flares will be the most challenging of the entire project. I didn't know it at the time, but Altec scored the back of the ply used to make the flares, which makes it much easier to bend. I didn't, and WOW, what a challenge that was. Heed the old adage, measure twice, cut once.

As to the speakers - stick to the original available from several on-line auctions.

[Charles Chance]

Also, I forgot - patience, patience, patience.

[pizzazz]

ok.... a few pointers.....

Use 3/4 furniture grade plywood (9 layers at
least).

spline-miter the joints and also reinforce
the inside corners behind the miters.

Transfer the radius of the curved flares
to the lower flare and inside-top of the
cabinet, and route a groove so the curved
flares can slide in.

For the curved flares, make sure the grain
pattern of the 1/4 plywood (luan or birch)
flows vertically.

Make sure you cut all the cabinet tops
and sides FIRST (including mitering and
making the groove for the spline) and route
the grooves BEFORE you assemble the carcass
(tops and sides).

For the backs, do a two-panel implementation
like the original A7's to help in making
the cabinet sturdy.

Mike

[rghinton]

Do all of the smaller enclosures use 1/4" stock for the curved parts of the horn? I am talking about the A7 the 817 the 816. I don't think that I have ever seen that dimension on a drawing. I was under the assumption that the A7, at least, used 3/8" stock. Please, someone set me straight on this issue. Thanks.

[[email protected]]

The horn flare material thickness is rarely explicitly designated in the plans I have. I have one plan for an 825 (two-piece back) cabinet that shows the flare to be 3/8" plywood. The drawing is appended to AN-12, though I don't think it is part of the original document. I have a 210 cabinet drawing that does not give the flare material thickness, but indicates that it is to be kerf-bent. It scales to 3/8" thick, but I'm not sure that's worth much.

FWIW, I've used 3/8" bending Meranti for several Altec-style 31" radius horn flares. It's worked well for me, and seems to fit into the general dimensional allowances in the original drawings.

[pizzazz]

Hi!

OK my mistake.... yes, the flare material it
3/8, but getting it to bend, you will need
to cut kerfs in it to make it flexible.

So, why not use 1/4 material and force it in
the groove?

groovy!!

Mike

[rghinton]

To whoever cares: I have owned 210 cabinets and the curved horn pieces are 3/4" plywood with saw kerfs 2" apart. I have very detailed plans for the 210 and it also specifies 3/4" plywood with saw kerfs 2" apart. I do not remember how deep the kerfs were and the detailed plans do not specify.

[pizzazz]

Hi

The A7 restoration is underway.

www.pizzazzimages.com

under 'mikes photos' there is a link
to A7 restoration.

I will post progress as I go along.

I have 4 cabinest to restore.


Mike