Please help…what inherent issues are there with this design?

[CPTX]

…and any suggestions to minimize problems/improve the design/or scrap it all together are welcome.

The essential thoughts include mounting an 8” driver flush to a hemisphere open at the front and rear (basically a large wood bowl with the rear cut off.)

Then mounting the bowl in a sealed 1ft or so cubed box.

Am I creating a mini bandpass problem or mini transmission line problem with the 7.8” circumference narrowing down to 5” circumference where it joins the rectangular box?

Picture below. Thank you all for your advice and suggestions.

If it’s not a horrible idea….I’m leaning toward doing it just for fun….but if it’s a silly idea that will be cursed with major problems, I’d rather not waste a lot of time.

 

[sergeauckland]

In addition to the transmission-line effect of the cavity behind the driver, there's the issue of diffraction round the sharp transition between the driver cone and the bowl. I would be surprised if it worked well, something you can only work out by measurements.
By all means do this for fun, but I wouldn't spend much time and effort on this.

 

[DVDdoug]

You are restricting "air flow" and it will have some (probably detrimental) effect.

 

[Petrushka]

I would refer you to some KEF designs, like the 105/3, that have a restricted port.

I have one, and I think the bass output is very smooth, but it’s a fussy design with some Rube Goldberg details.

 

[CPTX]

Maybe this instead…fewer variables and challenges. Flipping a larger wood open bowl and cutting off an 8 inch diameter off the bottom and mounting the bowl with the larger opening facing the sealed rectangle.

 

[Grotti]

Maybe this instead…fewer variables and challenges. Flipping a larger wood open bowl and cutting off an 8 inch diameter off the bottom and mounting the bowl with the larger opening facing the sealed rectangle.

View attachment 380922

+1

This would work and avoid the unwanted effects of the "original" design. And you wouldn't have to deal with corner defraction as there are none

 

[CPTX]

Thank you. Mojo restored and off to the wood bowl store.

 

[Rick Sykora]

Wood bowl could have ugly resonances. Maybe an 8” cardboard or PVC tube and cut a circular adapter out of MDF for the woofer. Seems like I just saw a build with protruding woofer but cannot locate. @ppataki has used wood bowls in one of his designs.

 

[CPTX]

Thank you, very helpful

 

[Kal Rubinson]

…and any suggestions to minimize problems/improve the design/or scrap it all together are welcome.

The essential thoughts include mounting an 8” driver flush to a hemisphere open at the front and rear (basically a large wood bowl with the rear cut off.)

Then mounting the bowl in a sealed 1ft or so cubed box.

Am I creating a mini bandpass problem or mini transmission line problem with the 7.8” circumference narrowing down to 5” circumference where it joins the rectangular box?

Picture below. Thank you all for your advice and suggestions.

If it’s not a horrible idea….I’m leaning toward doing it just for fun….but if it’s a silly idea that will be cursed with major problems, I’d rather not waste a lot of time.

View attachment 380909

 

[CPTX]

The beginning.
Also painting the inside of the bowls with a thick layer of silicone to minimize resonance.

Looks like Terry Cain (RIP) built quite a few in this style. Might try an open baffle also.

 

[CPTX]

Silicone dampening/resonance limiter for the inner hemisphere.

 

[CPTX]

Progress

 

[JSmith]

View attachment 380945

Hmm... thought you didn't like gif/image postings?


JSmith

 

[CPTX]

I am now at port size and placement crossroads.
This driver really begs for a port, so I’ve eliminated the sealed option.

WinISD has suggested a 4 inch port with a 1 inch length…..or a three inch port with 1/4 inch length. The thickness of the wood is 3/4”

The inner dimensions of the cabinet (without adding sand or closed cell foam) are 24 inches x 16 inches by 5.5 inches.

My instinct is to just drill a 4 inch hole either on the side of the cabinet or the rear of the cabinet and see how it sounds.

With this design, I actually have the most room for a port directly behind the driver.

Port placement has been studied (mostly for large woofers)….and this is a 6.5 inch midrange….but side placement seems to produce the lowest distortion….but, in my case, this would be where the port will be closest to the front and rear walls (tall/wide/shallow cabinet)

 

[CPTX]

 

[CPTX]

 

[CPTX]

The Yes Ma’am

The other one is in the final stages

 

[CPTX]

 

[CPTX]