New fold for Volvotreter's 38 Hz TH - diyAudio
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Old 19th February 2009, 05:23 PM   #1
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Default New fold for Volvotreter's 38 Hz TH

Volvotreter has documented three Tapped Horn designs. I liked his 38 Hz version using the 6.5 inch Tang Band, but I prefer a
different fold. Here is a scale drawing of my fold. It's 8.75 x 17.25 x 25 inches using 16mm wood.

http://www.volvotreter.de/
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File Type: gif volvo.gif (7.8 KB, 1658 views)
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Old 19th February 2009, 08:26 PM   #2
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could you refold that 38Hz TH for me using 0.5" material?
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Old 19th February 2009, 09:35 PM   #3
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Volvotreter's version used 19mm MDF and bracing. I thought I might regret using 16mm (5/8ths). The good 1/2 in ply is really 12mm (0.472) and is not rigid enough.

I am a little anal about accuracy in folding, but even I must admit that changing the thickness from 16mm to 12mm wouldn't make a measureable difference (except
for the shaking and buzzing that the thinner material would display).
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Old 20th February 2009, 09:03 AM   #4
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Recently I added a double folded version of the 38Hz TH which is similar to Don's version (which I like ).

I suggest to use 19mm MDF with braces. Even then you can feel slight vibrations when pushing hard. 1/2" will definetly be too weak.

A removable side panel would be sexy in order to check the influence of damping material attached to the walls on the response >100Hz.

Regards.

Erik


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Old 20th February 2009, 10:47 AM   #5
JLH is offline JLH  United States
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Quote:
Originally posted by Volvotreter
Recently I added a double folded version of the 38Hz TH which is similar to Don's version (which I like ).

I suggest to use 19mm MDF with braces. Even then you can feel slight vibrations when pushing hard. 1/2" will definetly be too weak.

A removable side panel would be sexy in order to check the influence of damping material attached to the walls on the response >100Hz.

Regards.

Erik


Click the image to open in full size.

Nice work Erik! What audible difference did you hear once you installed the 4.7mH coils? Have you been turning any more tractrix horns? I hope is well for you.

Rgs, JLH
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Old 20th February 2009, 07:18 PM   #6
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Erik, you do good work!

I took a quick look at your website, but didn't page down enough to see the new double fold. Did it sound identical to the single
fold? Where did you place the inductor? I have built two large cabinets, one for the 3015LF and one for the Lab12. I think it's
about time I built a smaller one.
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Old 23rd February 2009, 04:23 PM   #7
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I'm using a pair of Erik's single fold Tangbangs with the inductor. I love these speakers. Very small footprint and they blend extremely well with my JLH designed mid bass horns. I tried with and without the inductor and I hear what sounds like a better damped, controlled bottom end with the iron in series. They are driven with an older Van Alstine ss amp at 100 w/chan and active crossover. For the price of the wood and drivers, this was a cheap, fun project and a huge success. I can't believe the ouput I'm getting from these puny drivers!

I also have a 12" Eminence driver ready for a larger TH project but it has to wait until after baseball season.

Thanks Erik and JLH!

Jim D.
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Old 23rd February 2009, 05:47 PM   #8
JLH is offline JLH  United States
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Quote:
Originally posted by Jimmy D.
I'm using a pair of Erik's single fold Tangbangs with the inductor. I love these speakers. Very small footprint and they blend extremely well with my JLH designed mid bass horns. I tried with and without the inductor and I hear what sounds like a better damped, controlled bottom end with the iron in series. They are driven with an older Van Alstine ss amp at 100 w/chan and active crossover. For the price of the wood and drivers, this was a cheap, fun project and a huge success. I can't believe the ouput I'm getting from these puny drivers!

I also have a 12" Eminence driver ready for a larger TH project but it has to wait until after baseball season.

Thanks Erik and JLH!

Jim D.

Hi Jim,

If Erik hears the same thing that you reported with the inductor in place, then that makes three of us. I too hear the same things as you. As long as the inductor is low DCR, kept away from the woofer magnet, and is good quality it works very well. Good to hear from you again.

Rgs, JLH
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Old 23rd February 2009, 09:29 PM   #9
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Default How about 50-150Hz

I really like Volvotreater's designs... they look like something I can actually do with my carpentry skills.

Are there TH's designs that perform best in the 50-150Hz range?

I have a four part problem:
1) 4x18" IB that sounds great
2) 7.1 hometheater system that is great for HT, so-so for music
3) two kids getting ready for college, and not much $$
4) a love of building speakers and learning something while I'm doing it.

A TH that goes from 40-150Hz would be perfect (on axis with mains). I have an active xo. However, non-TH's typically require way more carpentry skills than I have. However, most TH's seem to drop off steeply/erratic performance above 100Hz... is this an inherent limitation to TH's, or just that most people are not trying to fill the same void as I am?

Thanks,
Steve
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Old 23rd February 2009, 10:20 PM   #10
GM is offline GM  United States
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So, which is it, 40 or 50 Hz? How big can it be?

Regardless, the HF 'hash' isn't nearly as bad as predicted and it can be further flattened with damping same as any other vented alignment as long as it's not the twin peaks that require band stop filters and of course the XO's effect on it.

Anyway, here's the popular MCM 55-2521 (John-Pat? measured) in ~36.5 L net/240 W/2pi space, exceeds Xmax around 26 Hz, though being a very high compression ratio (CR) alignment it may be suffer some thermal power compression if there's a sustained note down low at high SPL...........

GM
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File Type: gif mcm 55-2421 (measured 2) 38 hz conic th.gif (20.7 KB, 1333 views)
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