Building Helix-AG200 Angular Spirals and need some advice

[MonkeyOfAvon]

I recently built a pair of "Little Boy" TQWTs coupled by Fostex FE166En. I'm so happy with the result that I decided to build another set of speakers for the same drivers! The choice, quite randomly, fell on the Helix-AG200 Angular Spiral boxes - which are designed with FE166E in mind. As described here and in the following image below.



I decided on 16 mm MDF for the entire build (including fins) as that would be the cheapest and easiest option for me. (It's hard to get decent 15 mm plywood around here, not to mention getting it cut.) I'm building these on my balcony and in my one room apartment using electric hand drill, rasps, sandpaper and coping saw. So far I've cut holes for the drivers, vents and angled about half of the fins... which is taking quite a while because I have 2*2*8 = 32 angles to rasp by hand and plenty of other things to do. But I expect to be able to plug and glue the things together during the weekend.

Anyway, I would like to ask for advice regarding a few things:

• Stuffing. He mentions using Thermowool to stuff the (triangle?) area near the driver and covering the wall of the air chamber with felt. I'm not sure where to get Thermowool, so what would be a good replacement? I was considering buying one or two cheap pillows at IKEA and use the stuffing (100% polyester) instead. I still have some 2 cm thick polyester wadding from the previous build. Maybe a combination of both?
• I'm also wondering about the purpose of covering the inside with felt. What do I achieve by doing that?
• Rounding the fins. Is this worth the trouble? I've seen him do it to other in speaker designs "for a smooth sound passage", but I think those are generally more narrow in the spiral.
• D-C-fix. Perhaps not that important, but while I'm at it... When I'm finished, I thought I'd use some fake veneer style foil to cover the speakers. It's too late in the year to start painting and D-C-fix is cheap, fast to apply and easy to remove. After having looked around for a bit, I know some of you have tried it. What is your experience? Do I need to prepare the surface in some way for it to stick properly?

I've looked at related threads, but there is not much mention of this particular design, although there seems to be at least a couple who tried it out. I'd love to hear from you.



Thanks and happy building!

[Inductor]

MDF lacquered (by a professional) is astonishing. Try it.

[MonkeyOfAvon]

I was lucky enough to get sick last weekend, but now they are assembled - sans decoration.

There is not much bass and they sound a bit constipated. I probably packed the stuffing too hard so I'll try removing some (if not all to begin with).

[stewin]

Originally Posted by MonkeyOfAvon

I was lucky enough to get sick last weekend, but now they are assembled - sans decoration.

There is not much bass and they sound a bit constipated. I probably packed the stuffing too hard so I'll try removing some (if not all to begin with).

hi please post pictures of your results and build