Frugel Horn panel dimensions

[Bob W7ETA]

The are the dimensions I've come up with for level three build--I need someone to check them.

Frugel Horn Panel dimensions
Internal width of 140mm = 5 1/2 inches
Top panel 11 9/32
Bottom panel 15 1/8
A 4 /38
B 16 3/4
C 1 /38
D 20 3/4
E 4 1/8
F 11
G 12 1/8

Triangle 21 3/8 x 10 1/4 plus a top hat of 10 1/4 x 9 1/2

Wedgie
5 17/32 x 5 1/2
12 5/32 x 18 1/4
1 7/32 x 18 1/4

Side panels 15 1/8 x 20 7/16
Front panel 30 15/16 x 5 x 12

Partitions made from .625 inch plywood
sides made from .7 inch plywood

I'll be using 1/2 plywood for the partitions and 3/4 inch for the sides and front, or since I'll be getting 3/4 plywood, 3/4 for all.

Thanks for the help
Bob

 

[chrisb]

Since no-one else has replied yet, a couple of notes:

If you haven't already bought / ordered the material, I'd suggest 3/4" for the side panels (gables) and front baffle - 1/2" for the internals would be fine, although I've personally upgraded to 5/8" (15mm) baltic birch ply on my recent builds for all but the driver baffles.

If you elect for a thicker material for the internal panels, you'll need to redraw to allow for reduction in the CSA - the difference from 1/2 to 3/4" (or 12mm to 18mm in the case of metric BB) could compound significantly enough to effect performance in a design with as many folds and corners as this.



If you've taken the dimensions from the PDF plans on the Frugel-Horn site, you should be fine, but remember that some of the length dimensions would depend on your joinery choices - butt, rabbeted, etc.

 

[Bob W7ETA]

Hi Chris
Thanks for the info.
I rented a van today to drive to Sears to pick up the table saw I bought. I wound up spending 2.5 hours there getting a complete one--they will ship it to me on the 31st.

I stopped by Lowes on the way home, felt so bad, that I walked out and came back home. Time for some food and COFFEE.

I'll check out the price diff between 1'2 and 3/4. I was looking at the oak, more expensive, but the Birch is from China, and I'm guessing, ioak might be stiffer.

Best
Bob

 

[chrisb]

Hi Chris


I'll check out the price diff between 1'2 and 3/4. I was looking at the oak, more expensive, but the Birch is from China, and I'm guessing, ioak might be stiffer.

Best
Bob

First of all, congrats on the new saw, and for undertaking this project.

You may already know this, but oak face veneered plywood can vary rather substantially in terms of numbers & composition of cross banded core plies. There's no guarantee that just because the very thin face veneer is of a species that is very stiff as a solid, that the underlying substrate cores will be also. Often this type of product is described as "furniture" or "cabinet" grade - really that means that with decent joinery, edge treatment and finishing techniques, it can be made to look very attractive - but for a high performance loudspeaker enclosure, it may be lacking.

OTOH, some (many) of the "oriental" multi-ply birch goods we've been offered over the years are even worse - fine for substrate for plastic laminate, carcass work, or shipping crates, but highly susceptible to internal voids and even delamination.

I guess it's just my personal bias, but I wouldn't recommend using any type of plywood for loudspeakers other than Baltic, Finnish, Russian etc birch - depending on your geographical location, any of the above generic names may be used, and in some cases the product is available in non-standard sheet sizes ( i.e. 5x5ft 4x10 ft etc.,)

The downside to the utility grades of these material is that the face veneers are not necessarily pretty for finishing, may include patches, pin-hole knots, mineral staining, etc., and exposed edge-grain may include discoloration of solid knots, and overlaid repairs to voids. Of course, that could be considered part of its appeal?

A decent quality carbide tipped saw blade for cutting plywood on your new saw should cost more than the difference in price between the types of sheet goods in question (indeed, probably more than the total cost of a couple of sheets)