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Old 6th August 2010, 01:05 AM   #21
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and so is the frequency response, so what's your point!
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Old 6th August 2010, 01:16 AM   #22
freddi is offline freddi  United States
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here was my junk 1-sheet plywood pipe - maybe not competitive
YouTube - ‪7.4 cubic foot inverted tapped horn/transflex-type test pipe from 1 sheet of plywood‬‎

since U guyz are good with hornresp - come up with a Karlson kluge for it
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Old 6th August 2010, 01:21 AM   #23
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"and so is the frequency response, so what's your point! "

It's easier to measure the impedance peaks than the frequency response (most people don't own a spectrum analyler, but they could buy a $10 voltmeter).
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Old 6th August 2010, 01:29 AM   #24
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Originally Posted by Don Snyder View Post
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.
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Old 6th August 2010, 01:45 AM   #25
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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...
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Old 6th August 2010, 01:52 AM   #26
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my inverse taper pipe on HR calculates to 97dB/50Hz halfspace - Martin's 1844 isn't as punchy on the top as a discontinued 295070 - -Cubo looks cool
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Old 6th August 2010, 01:59 AM   #27
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my inverse taper pipe on HR calculates to 97dB/50Hz halfspace - Martin's 1844 isn't as punchy on the top as a discontinued 295070 - -Cubo looks cool
Set the drive voltage using Re instead of the default 8 ohms. The efficiency should drop a bit.
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Old 6th August 2010, 02:05 AM   #28
freddi is offline freddi  United States
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I'm on a Mac without way to run hornresp - but that makes sense
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Old 6th August 2010, 02:27 AM   #29
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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.
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Old 6th August 2010, 02:40 AM   #30
freddi is offline freddi  United States
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figures I'd come up with a loser - smaller can be better if spl can be met - which thread has your 4.3CF tapped horn?
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