Designing the AtomHorn, a 25-30 Hz tapped horn from Germany - AVS Forum
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post #1 of 9 Old 12-27-2011, 02:35 AM - Thread Starter
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Hi,

so the AtomHorn is shaping up, thanks to some input from Lilmikes Anarchy Horn tread and it is time to open its own thread here.

A friend recently adviced me to look into tapped horns, when I was searching for ideas for two subs for my new home and soon I stumbled over Lilmike's greatly documented designs wich encouraged me to dare and design one of my own. So big thanks goes out to Lilmike for taking the effort of documenting his desings so well, giving others a really good starting point in designing such subwoofers.

My goal is a 25-30Hz tapped horn with a tangBand W8-760C driver, that fits under a desk. http://oaudio.de/media/products/9f11c282a848aa63a8e.pdf
This driver is available in Germany for 30 at this time, used to be sold for 60, and it looks really promising.

So after hours of modeling and some good advice over at the Anarchy Horn thread here's what I can come up with so far:













And finally the hornresp-file for all those interested: http://komeda-berlin.de/images/atomhorn/atom_wip.txt

So that's the best I am able to do right now, feel free to comment, critic and suggest...

Best regards,
Nico
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post #2 of 9 Old 12-27-2011, 12:45 PM
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your design looks fine.

however, you should always compare your design with a ported enclosure in order to see how much "horn effects" you are getting.

in your case, you are inputting 2.83v into 6.5 ohms, which is 1.23 watts.

1.23 watts into that driver in a ported cab is 1-2db lower in spl than your horn, so you are only getting 1-2db of horn effects.

in my opinion that is not worth the added complexity of building a horn.
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post #3 of 9 Old 12-27-2011, 01:10 PM - Thread Starter
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Well, one of the points about building a tapped hornfor me is figuring, how they actually compare to a ported enclosure. There are a lot of different opinions around. Mostly I am interested in how it actually sounds. A lot of people describe the sound extremely tight and precise, with lower distortion than ported boxes. Others write, there would ne no big difference, and so on. I figured, the only way of knowing it in the end is building one, wich is also fun and I learn something.
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post #4 of 9 Old 12-27-2011, 02:16 PM
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Quote:
Originally Posted by LTD02 View Post


1.23 watts into that driver in a ported cab is 1-2db lower in spl than your horn, so you are only getting 1-2db of horn effects.

in my opinion that is not worth the added complexity of building a horn.

+1. For the cab to have decent sensitivity the mouth area needs to be increased by a factor of six or more.

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A lot of people describe the sound extremely tight and precise, with lower distortion than ported boxes

That's the result of lowered excursion compared to a VB, and lowered excursion is the product of higher sensitivity.
http://www.readresearch.co.uk/loudsp..._article_1.pdf
http://www.readresearch.co.uk/loudsp..._article_2.pdf
http://www.readresearch.co.uk/loudsp..._article_3.pdf

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post #5 of 9 Old 12-27-2011, 03:53 PM - Thread Starter
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Well, thx for the hints. I went and simulated some ported enclosures and you're right. No real gain with the horn, just a lot more space. Even the displacement is not less with the horn, so where should the improvement come from? Surely not from a driver, that has a more relaxed job..

Well, I might have to think it over, maybe it will just have to be a bigger horn, if I really want to try one. Anyway, we are moving in two days and I will actually see where I could hide two beasts in that room and think again.

Didn't get to read those technical papers, yet, but thx. for the links, I will look into them as soon as I find the time.
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post #6 of 9 Old 12-27-2011, 04:38 PM
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a good way to think about horns is to look at some brass horns...trumpets, french horns, trombones, f-tubas, concert tubas. they have increases in efficiency of the low notes as they get larger.

there is a reason why bfm built his "tuba home theater" as large as he did.

to sum up the papers that he posted, in order to hit low notes with high efficiency, you need a big horn to couple the long waves of the high impedance (strength) device at the throat to the low impedance air at the mouth. for intuition it is like fanning the air with your bare hand vs. holding a magazine/paper. the latter couples to the air better and blows more wind.

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post #7 of 9 Old 12-28-2011, 03:39 AM - Thread Starter
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That is exactly the way I always saw horns and also the reason why I never got into them. I understood tapped horns to couple differently, but didn't get into fully understanding the principle (yet).
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post #8 of 9 Old 12-28-2011, 05:48 AM
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Quote:
Originally Posted by ((( atom ))) View Post

That is exactly the way I always saw horns and also the reason why I never got into them. I understood tapped horns to couple differently, but didn't get into fully understanding the principle (yet).

Most designers of tapped horns don't understand them, and get all excited when they get 3 or 4dB higher sensitivity than the same driver in a VB. IMO if you're not getting at least 6dB of gain from a horn it's not worth the bother. A dead giveaway that you're on the wrong track is if you see response peaks in the midbass 10dB or more higher than the low frequency response, just as is the case with your chart.

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My goal is a 25-30Hz tapped horn with a tangBand W8-760C driver, that fits under a desk

That goal is unattainable. Tapped or not horns that go low are large. If you want to go to 25-30Hz with a horn the smallest cab that's worth the effort will be about 300 liters total volume. If you must go smaller use a direct radiator or bandpass.

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post #9 of 9 Old 12-28-2011, 07:19 AM
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Quote:
Originally Posted by ((( atom ))) View Post

I figured, the only way of knowing it in the end is building one, wich is also fun and I learn something.

That's why I went ahead and built my dual Tang Band 8x12" design. I got a lot of criticism over that design because it barely had enough sensitivity to make sense. It's an undersized design, only putting real horn gain in down around the corner and top end, but not a lot in the middle. I wanted to learn, and I believe I learned a lot by going ahead and building that monster. I'm still learning, but I'm further along than I would otherwise be. All it cost me was $500... I spent more to learn less useful knowledge back in the 90's learning computer programming from a crooked technical college.

As for the design, I'd try and get more horn gain going on. As others have said, increase the mouth size a bit (and S3 as well)... that'll help. Of course, that will make it bigger - you'll have to decide how much space to trade off. Maybe move the corner up if you have to... even a couple of Hz can make a big size difference. Watch the phase graph... it's not quite lined up within 90 degrees yet in the passband.
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