Foam Core Board Speaker Enclosures?

[Carlp]

Hey Badman, can you describe the sound of the mids and above? I'm no engineer and only understand pretty limited concepts re: speakers, so these are beyond my paygrade to make sense of. Still, it seems very different from most approaches to speakers that I'm familiar with, so it's interesting to me.

[bcmbob]

Carl, I was a bit confused also till badman repeated these are surrounds. If you have been to a movie theater lately you will see maybe 10 or 12 speakers along each side wall. They are there in an attempt to replicate the enormous amount of reflected sound in real life.

In the average home that is impractical, so forcing the sound to reflect in at least two opposing directions along those side walls has become an acceptable compromise. You are correct, as badman stated, surround speaker design is almost the opposite of standard 2 ch approaches. Note my sides are not only bi-directional, but also have vertical offsets to enhance diffusion. Using the wall (and in my case the ceiling front surrounds) also allows the ambient information to be heard realistically at more locations in the room.

Mostly mid and some HF information is EQed into the 5.1 and 7.1 mix so smaller and less sophisticated drivers are sufficient - though a system with two way surrounds can benefit from having the same tweeter as the main front L/R speakers. That just provides a tonal match and as badman says, lessens the surround's potential to draw the listeners attention.

Nice work and clever idea on the roundover Mr. B Sounds like you have taken great advantage of the ability to experiment with FC.

[badman]

I was able to cut foam freehand, based upon a tracing pretty easily- made 3 14mm wide x 12" round rings, +/- 1mm tolerance or so. coat the edges with some pva and you've got some nice gaskets.

[badman]

Easy constrained layers with the plastic faced foamcore:


Basic medium compression weatherstripping, with a foamcore layer fastened around the perimeter with screws/bonded washers into a wooden sub-assembly. So long as you are careful, the compression at the screws is not too bad. I'm not sure how this would work with the paper-faced- the elmer's seems to be stronger, but might be worth shellacking the surfaces to make it stiffer. With my plastic-faced stuff (it has paper under the plastic too) it makes a panel that's not only got good damping, it's also somewhat pre-tensioned, and very well damped indeed.

[bcmbob]

Now you've got me confused again. Where does the port/guide terminate? I was looking for something like this (top view). Roundover to radiate at multiple angles - no?

[xrk971]

I think the wall is on the other side so the sound ducts are next to wall.

[badman]

Originally Posted by bcmbob

Now you've got me confused again. Where does the port/guide terminate? I was looking for something like this (top view). Roundover to radiate at multiple angles - no?

I hope these views clarify- the slot that's built into the driver

Panasonic EAB12147E 3" x 5" Full Range LCD TV Shielded Speak | 299-682

terminates into the gap between the wall and the roundover. The rectangular open end of the "Waveguide" slot is perpendicular to the ground.wg dipole 2.jpgwg dipole.jpg

[bcmbob]

Got it - thanks! Would still like to see a photo of the actual driver mounting - if/when you get a chance.

[badman]

Originally Posted by bcmbob

Got it - thanks! Would still like to see a photo of the actual driver mounting - if/when you get a chance.

Foam Core Board Speaker Enclosures?

You can see here how the drivers are arranged- the slot "termination" is far from perfect, the devices are too wide to make an uninterrupted slot source. The mounting is actually done with hot melt glue- it grabs very aggressively to both the wood and the polyethylene waveguides.

[bknabe]

X
I made my first FCB speakers! Small scaled down versions of the Lance. I used some small 2" BMRs I had hanging around. Took about 2 hours total. Good first attempt to learn some of the techniques for FCB. They sound pretty good! I have a pair of the Fountek FE 85s what do you recommend?
Bob