Foam Core Board Speaker Enclosures?

[xrk971]

It is a lot of fun. Best part is instant gratification as these projects can be built in several hours. They sound very good too.

[cochleus]

Originally Posted by xrk971

Which way does your driver point? Is this foamcore board?

The driver sits at the top of the enclosure and fires down into the horn. The material is foam-core board. The path length is 62 inches.

[xrk971]

OK, so the horn output is perpendicular to the output direction of the front of the driver? What driver are you using? I like how you did smooth curves, that improves efficiency but let's high frequency stuff come through. Will you use stuffing anywhere?

[xrk971]

I am thinking about the next horn project. There is a cool flat panel wall hanging horn speaker called the Cornu spiral. ( 6moons audioreviews: Cornu Compact Spiral ) This would be an easy build in foamcore, or a Fibonacci sequence Spiral where the expansion ratio goes as 1:1:2:3:5:8:13 and so on. Practically it is tough to reach 13. Is there any advantage to using the magical natural expansion ratio such as used by the nautilus seashell?

[xrk971]

A quick estimate of the Cornu spiral design shown here (seb:diy:audio: Cornu Spiral Copy Horn ), re-scaled for the Vifa TC9FD will be a 20 x 20 in square (perfect for 20x30 in foamcore board stock) will result in an effective expansion ratio of about 24:1! The pathlengths (2 separate spiral lengths) will be around 1.0 and 1.36 meters for two tuning frequencies of 85 Hz and 63 Hz. The expansion ratio is huge so the bass amplification should be significant. I am thinking of modifying the design by using curves near the mouth for aesthetics and efficiency but square corners internally to act as low-pass filters.

[cochleus]

Originally Posted by xrk971

OK, so the horn output is perpendicular to the output direction of the front of the driver? What driver are you using? I like how you did smooth curves, that improves efficiency but let's high frequency stuff come through. Will you use stuffing anywhere?

The design was intended to be a low-loss back loaded horn with the driver reversed (concave side facing into horn throat). Stuffing was only placed near the throat area to absorb higher freq. standing waves. The test speakers I used were Tang Band W4-1320 SJ. I gave up on the design but think it may have uses if crossed low enough.

[xrk971]

Why did you give up on the design? The bookshelf back loaded horn design I described earlier finally got tested with the Viva TC9FD drivers, they work well and have very good bass. You don't need BSC given how Much bass it produces from the front facing port. The putty damped front baffle actually works - there was almost no vibration coming through whereas the undamped panels you can feel the vibrations from the music.

[xrk971]

Originally Posted by xrk971

A quick estimate of the Cornu spiral design shown here (seb:diy:audio: Cornu Spiral Copy Horn ), re-scaled for the Vifa TC9FD will be a 20 x 20 in square (perfect for 20x30 in foamcore board stock) will result in an effective expansion ratio of about 24:1! The pathlengths (2 separate spiral lengths) will be around 1.0 and 1.36 meters for two tuning frequencies of 85 Hz and 63 Hz. The expansion ratio is huge so the bass amplification should be significant. I am thinking of modifying the design by using curves near the mouth for aesthetics and efficiency but square corners internally to act as low-pass filters.

I have already drawn out the full scale template for the 20 x 20 in Cornu spiral horn. I used a string to measure the lowest mode and it is 61 Hz. Need to get some more foam core board stock before starting. It's like how many different speakers can one make with a TC9FD? We know it works great in the Manzanita OB.

[cochleus]

Originally Posted by xrk971

Why did you give up on the design?

For a couple of years I was trying some kind of different idea/prototype about every two weeks or so. I still have a closet stacked full of experimental speaker enclosures collecting dust. It was great fun and I learned something. Now I like the sound of open baffle until I find something even better.

[VaNarn]

An interesting material called XBOARD PLUS PANELS ,has appeared recently and in its' thickest form offers a very high stiffness with a very low transmission of sound through the material.In Melbourne it is being tested in a a 650 litre vented enclosure matched to a modified Altec Lansing 15'' woofer with an ESS HEIL AMT in a two way system.The supplier of the panels is SHARP PLYWOOD in Queensland, for those who might wish to have more information.