Perspex Speakers

[Mandi74]

Hi

I just wondered whether anyone could offer some advice. I would like to make one speaker out of perspex, as a sculpture playing a sound piece.
I have little experience in this department, but I have been researching and have come across a design on a website, which uses 2 full range drivers in a Quarter wave resonator enclosure
BD-Pipes Speaker with Radio Shack 40-1197 (FE-103)

The material these enclosures are made out of (usually MDF or chip board) is very thick (around 2cm) and would be prohibitive to make in acrylic. Would the sound be affected very much, if I were to use something thinner say 8mm or 10mm thick?

The reason for the transparency is to contain a quantity of artificial fibre (synthetic hair clippings). I have a large qty of these clippings and wonder whether this material would adequately insulate the sound? As the material is loose, is it possible to fill part of the box as opposed to lining it?

I'm looking for a speaker design as simple as possible - because its to be exhibited, I also require it to be of reasonable size for aesthetic reasons, as well as the sound. So a smaller unit around 50cm tall could also suffice, do you know of any smaller designs using full range units?

The Novice Mandi

[Greg B]

8 or 10mm acrylic should be sufficient. The spans of that design are fairly narrow, and some cross bracing could always be added.

Perhaps Dave will chime in. He designed it I believe.

I've often pondered building a clear 'perspex' (you must be from the UK ) speaker. It presents some interesting problems, mostly having to do with the damping materials. The usual polyfill would be hideous. What exactly is this artificial hair? I'd imagine some brightly colored cotton candy looking little clouds floating inside might make for an interesting effect. For lining the walls, perhaps simple bubble wrap would work, or some sort of clear textured bath mat etc might be re-purposed.

Another idea I had, which would be a lot of work, was to make a whole bunch of little sea anemone type things from silicone sealant. Could be an interesting effect if stuck to the inside of the cabinet walls.

RE your technical questions: It is very common to stuff TQWT of this type with polyfill from the pointy end to just past the drivers, or just before, depending. I see no reason why your 'hair' would not work. Other times, it sounds better to line them and leave the airways open. It depends on the drivers used, the design of the cabinet, and other factors.

[chrisb]

where to start?


errata:

while “we” did build several pairs of them Dave did not design the enclosure named above, that was Bert Doppenberg


If you think the high quality plywood we like to recommend for speaker boxes is costly, try pricing acrylic plastic sheeting thick enough to have adequate machining capabilities for the mechanical fasteners required to attach at least the driver(s).

I'd suggest that at least 10-12mm would be required - based on pricing from our wholesale supplier/fabricator you could look forward to equivalent cost of $450 - 500 per 4x8ft sheet.

Cutting and fabricating plexi requires tooling somewhat more specialized than for plywood or MDF, and particularly some skills with the adhesives.

There have been a few examples of DIY projects here and elsewhere using acrylic as flat side panels to showcase elaborate internal paths of horns, TL's etc – they’ve been attached to wooden internal structure mostly via conventional woodscrews, and gasketed with foam tape etc.

Aside from some back loaded horns, most speaker enclosure designs I’ve encountered / built have required some degree of internal damping / insulation (certainly the case for the BD Pipes) , which in addition to wiring, input terminals, crossover/filter networks as applicable would be visible. That’s fine if you’re going for the look.

[Greg B]

errata:

while “we” did build several pairs of them Dave did not design the enclosure named above, that was Bert Doppenberg

That's right, oops. It was "Bert D". Been a while now since those came out.

There are no shortage of smaller cabinet designs for FR drivers on the web.

Since I often have to deal with acrylic fabrication in my day job, here's some unsolicited advice:

Cutting and fabricating plexi is more difficult than wood, but not impossibly so. Plastic places often have scraps they sell for next to nothing. It's a good idea to practice on those. There are several kinds of glue. The basic solvent based cement (ie Weldon 16) is best for a beginner, but it will leave visible imperfections in the joints. For perfect invisible joints, two part adhesives should be used. These however are not practical for most DIYers.

[Mandi74]

Thanks guys for your comments and links are very useful. some of the enclosures are beautiful! Makes my mouth water thinking of them in Perspex, its no joke financially though. The plan is to get some expertise to construct the box itself, I've got to factor the labour in which might really burn me! so I need to look at a couple of options for costing.

I've also seen some really simple Bass Reflex enclosures? Could they work, with this idea? making smaller box might reduce the cost. If I were to make one around 50cm tall what full range driver would you recommend?

The hair isn't quite as fluffy and pretty as you think...

The novice in the UK

[Greg B]

I've also seen some really simple Bass Reflex enclosures?

Yes. Some of the Fostex drivers, and most or all of the Fountek, Mark Audio, Tangband, et al drivers are designed for Bass reflex. If you went with say Fostex drivers, they come with plans.


Here's an example:

[planet10]

Originally Posted by Greg B

If you went with say Fostex drivers, they come with plans.

Do not go into a build of the Fostex factory boxes without vetting them, some are OK, could be better, some ca only be called cruel jokes.

dave

[freddi]

mini K-coupler - not much room for damping material