Mid Bass Horn Design 80-800 Hz

[Steve Mac]

Starting a new thread and will post links to images instead of images to make loading the thread speedier.

Plywood
Rear Chamber pieces
Glue and screw the Rear Chamber 1
Glue and screw the Rear Chamber 2

[valhallax]

dont know where ol' jim's been lately, but having dial up , here in the boonies, sure made the last page load slow with mug all over it..lol
glad ya brought this one up..lookin forward to watchin your progress here. did i read anywhere which drivers you'll be using?

[Steve Mac]

Sketch out the speaker outlines on the rear chamber

[Steve Mac]

Originally posted by valhallax:
dont know where ol' jim's been lately, but having dial up , here in the boonies, sure made the last page load slow with mug all over it..lol
glad ya brought this one up..lookin forward to watchin your progress here. did i read anywhere which drivers you'll be using?

<font size="2" face="Verdana, Helvetica, sans-serif">That's pretty funny..
Pic of the 4 - GPA 515-16G horn woofers

[Steve Mac]

Westrex 501A

This is an old design, the oldest I could find which is similar to this design. Does anyone recognize this speaker or have any historical info to share? I couldn't glean measurements from this either. But it is very interesting...very nice...I notice a lot more of the speakers are exposed at the throat...driver size?

[GM]

Greets!

Not me, only seen pics.

Drivers are nominally 15" with HF horns being 13.5" dia., so you can 'ballpark' scale it: http://www.lansingheritage.org/html/jbl/plans/t550a.htm

GM

[Steve Mac]

The wedges in this design contain all the exponential information. This is half of the first wedge piece rough cut:

Making the template

Once this piece is smoothed out, I can use it as a template to rout the others except the other side of this wedge. For that I will use one of the others. Gotta pick up a router bit with a ball bearing to flush trim tomorrow.

If anyone has any ideas, I am still undecided as to the gasket material to use to seal the side panels, wedges and probably the rear chamber back panel. I'd like to find something unique...maybe a rubber type that hermetically seals and retains its elasticity.

[bfish]

There looks to be a sudden increase in flare rate about halfway down, is that to compensate the inner horn area, or just my weary, old eyes?

For gasket material for the removable rear panel, most home centers carry a thin, rubber weatherstrip meeting your description (has a 'P' cross-section). Unless you need to disassemble the horn in the future, I'd Gorilla-glue it (amazing stuff, just remember to wet the surfaces first). FWIW, "hermetic" implies the box would hold a vacuum, an ambitious pursuit for wood indeed.

If not too late, I'd also suggest leaving the rear compartment dividers movable, to allow tuning the Vb once everything's assembled. No need for fiberglass there, but a thick (~1/4") layer of felt covering the inner rear surface is a good idea.

[Steve Mac]

Originally posted by bfish:
There looks to be a sudden increase in flare rate about halfway down, is that to compensate the inner horn area, or just my weary, old eyes?

<font size="2" face="Verdana, Helvetica, sans-serif">For the inner horn area.

For gasket material for the removable rear panel, most home centers carry a thin, rubber weatherstrip meeting your description (has a 'P' cross-section).

<font size="2" face="Verdana, Helvetica, sans-serif">Okay, I'll check into that.

Unless you need to disassemble the horn in the future, I'd Gorilla-glue it (amazing stuff, just remember to wet the surfaces first). FWIW, "hermetic" implies the box would hold a vacuum, an ambitious pursuit for wood indeed.

<font size="2" face="Verdana, Helvetica, sans-serif">One of the requirements is to be able to disassemble. And yes, the goal is some type of rubber seal or gasket that does a helluva job. Hyperbole is my middle name.

If not too late, I'd also suggest leaving the rear compartment dividers movable, to allow tuning the Vb once everything's assembled. No need for fiberglass there, but a thick (~1/4") layer of felt covering the inner rear surface is a good idea.

<font size="2" face="Verdana, Helvetica, sans-serif">I remember Steve Schell suggesting this, but I was careful to oversize it by 10% over the computed design numbers cranked out by my very helpful friend, Mr.GM. There are enough seals to be made already so I wanted to limit the scope therein. If I weren't taking an old established design and not using GPA woofers, I would feel differently about this. If I'm wrong, I'm not too worried because I will only need to rebuild one of the horn's pieces...a calculated approach.

Thanks for the advice, really. I learn something every time I'm up on this forum. It's a good one for sure. The only thing this place is missing is Brazilian Supermodels. Then I wouldn't have to go anywhere else.

[bfish]

You're welcome.

I've played with lots of gasket solutions, but usually settle for compromises. Rubber seems best for repeated use, but leaves a minimally-compressable base thickness to deal with. Properly selected foam solutions have better compressability, but can become permanently compressed over time. For an app that may see infequent disassembly, I think I'd use Mortite rope putty, and just plan on replacing it upon reassembly. That's what Roger Russell used in similar Mac apps, so it's good enough for me (and cheap too!).

<font color="#FFFFFF" size="1">[ December 08, 2007 08:25 PM: Message edited by: bfish ]</font>