Single sheet TH challenge

and so is the frequency response, so what's your point!

An accurate impedance plot is very easy to obtain with something like a WT3(which you should use anyway to confirm driver parameters before building something as complicated as a TH) and will show immediately how close you got to the sim with your build. It can even show you if there are problems with the build (e.g. leaks near the driver will show up in the plot as a raised Fc, and leaks elsewhere will result in the impedance dips in the passband being significantly higher in level than predicted. The effect of panel resonances that need to be attended to will also show up in the impedance plot.

Getting an ACCURATE frequency response plot is a bit more difficult to obtain than the impedance plot.
 
The 'iron law' still applies to a TH enclosure.

I don't think 40hz and 100dB are possible from a 2' cube.

50hz, yes, 40hz, no.

#9 is a good example of that at 90dB at 40hz.

"in reality it goes lower"

With room gain, I might buy that. In 2Pi or 4Pi, no way.


HornResp predicts 92.5dB/1W/1M for the cheap Dayton PA310 in a 4.3 cu.ft. TH. This could be built using one 4x8 piece of ply, and actually have a sizeable piece left over :). I suspect you can get a bit more with a larger enclosure.

Jbell, how are you measuring the efficiency of your TH? Or are you measuring sensitivity then converting? I was assuming an 8 ohm load for my HornResp designs, then decided to use Re instead of a nominal 8 ohm load to set the "1W" voltage. That dropped the voltage and as a consequence the calculated efficiency a bit...
 
I'm on a Mac without way to run hornresp - but that makes sense

I ran a sim using your figures and the adjusted drive voltage - results suggest 93.2dB @ 40 Hz with 1W input. I re-ran the sim for my 4.3 cu.ft. TH and it suggests 93dB @ 40 Hz with 1W - not bad for a cabinet almost half the volume. Of course the peak SPL capability of your system will be a lot greater than what this 12" TH is capable of.
 
I think I got it....

Don would you run your cad on this... I think its a winner. And this one is definitely solid to 40hz, AND a better shape than a cube.

The scraps at the end are for braces/angles as I need them. Won't know exactly till it's built.
 
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This should have the 'big box sound' in a 50lb package, instead of a 150lb package. It's giving up a couple db in sensitivity to the big box, and it's giving up about 100 watt power capacity to stay under xmax to the cube. (bigbox is good to 50v, this 56v, cube 63v).

I'd like to move the upper part up an inch, so the flare would start about 4" tall, and end at 10.5" tall. It'd have a better response, but I haven't figured out how to get the back part of the cabinet right, so the flare is continually expanding.
 

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This should have the 'big box sound' in a 50lb package, instead of a 150lb package. It's giving up a couple db in sensitivity to the big box, and it's giving up about 100 watt power capacity to stay under xmax to the cube. (bigbox is good to 50v, this 56v, cube 63v).

I'd like to move the upper part up an inch, so the flare would start about 4" tall, and end at 10.5" tall. It'd have a better response, but I haven't figured out how to get the back part of the cabinet right, so the flare is continually expanding.

It's a bass bin, so you don't have to have a continuously expanding flare. You can "step" the sections. I built a TH with the stepped cross-section below just recently, and the measured response within its passband seems a pretty decent match for the HornResp predictions. It also allows me to top-mount the speaker (I've left the top panel removable).
 

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yea, the hard part was figuring out the overall dimension and cut sheet -- once that is done, all kinds of options open up.

Here's another thought I'm running with. More top end (like oliver's posting awhile back) and still reasonable 40hz...
 

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I recognize that folding type, I'we done something simillar in this design suitable for the 15TBX100 or eighteensound 15LW1401 :
THAM15-02.jpg

I wonder if design is possible to complete from a single sheet, I'll do the math and get back to you, it does seem small enough, if it does meet the challenge criteria this would be my entry.