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Old 5th March 2010, 01:35 PM   #1
johnr66 is offline johnr66  United States
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Default plexi tapped horn model

After reading this group, I have become interested in a tapped horn woofer design. I had some plastic scraps left over, so I built a small model of one. I was limited to 24" long and I took a 5" driver out of a small speaker to test with. Of course, the small size means a higher frequency range, but this is more of a curiosity to experiment with.

Using a small 9 volt battery powered chip amp and a function generator, I fed the thing some signal. Strongest output is around 115 Hz with good output down to 105Hz. Using the sliding piece to adjust mouth size, I reduced the opening to 1/3 the size. This had the effect of reducing the peak range, but giving a wider response that reached to lower frequencies.

At only 3/4 watt it made metal things in the room vibrate. I could feel the sound on my chest. I can now understand the interest in these things. Can't wait to see how the full size version performs!

The full sized horn will be made of plywood. It will be 6' long and use a 12" driver.

Click the image to open in full size.
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Old 5th March 2010, 04:01 PM   #2
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Neat little experiment John. Thanks for sharing.
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Old 7th March 2010, 10:58 PM   #3
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Looks amazing, wouldn't mind having a 6' version in my room.

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Old 8th March 2010, 12:30 AM   #4
johnr66 is offline johnr66  United States
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Default The beast is done!

Its 6 feet tall, it weighs a ton, but it is done! Until I can afford a better speaker, I am using an old Radio Shack 12" dual voicecoil woofer. I set it in the corner with the mouth facing the wall with 8" of space. Using the small 9 volt powered chip amp, I fed it a signal.

Using a function generator (and my ears), It is resonant in the 33 to 37 Hz range. With less than a watt of power, I could walk into different rooms of the house and find things rattling. The SPL near the thing incredible.

using an "aperture cover plate" and covering about half the mouth, I can reduce the frequency response by about 5Hz with usable output below 25Hz, but there is some loss in efficiency. I really need to hook this up to a stronger amp as the output coupling capacitor impedance reduces power to the speaker at these low frequencies.

Here's some construction photos:
Click the image to open in full size.
Click the image to open in full size.

To give credit, it is based of this design on William Cowan's site:
http://www.cowanaudio.com/images/30H...d%20Horn_2.gif
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Old 21st March 2010, 05:09 AM   #5
freddi is offline freddi  United States
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nice TH sub - if you had some plastic left over I'd ask you a price on building a little clear Karlson toy
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Old 21st March 2010, 07:15 AM   #6
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I just watched your video on youtube the other night.
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Old 21st March 2010, 02:55 PM   #7
johnr66 is offline johnr66  United States
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Quote:
Originally Posted by freddi View Post
nice TH sub - if you had some plastic left over I'd ask you a price on building a little clear Karlson toy
I was thinking of doing something with a 6-1/2" driver. Problem is that thick acrylic is expensive and so is fabrication. I wouldn't do it, but was thinking of the cost of making the 6 foot version of the horn I made in acrylic. It would weigh twice as much and cost a few thousand $$.


Quote:
Originally Posted by DigitalJunkie View Post
I just watched your video on youtube the other night.
That's me With some help here, I got a far better matched driver for the wooden beast and it sounds wonderful now. Smoother response and good extension into the 20Hz range.
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Old 21st March 2010, 08:14 PM   #8
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Cool to see it turn out well. Nice video too...you should do another now that everything is finalized.

Link to the video : YouTube - Tapped horn / Folded horn subwoofer box build
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Old 21st March 2010, 09:20 PM   #9
freddi is offline freddi  United States
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I had one sheet of flooring plywood and lower fs 15" woofers so went the other way on taper - it left a hole kinda like with BIB simulations. I didn't talk as reflux has taken out my teeth YouTube - 7.4 cubic foot inverted tapped horn/transflex-type test pipe from 1 sheet of plywood
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