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mrevie 10th May 2009 03:26 AM

Tapped Horn or Transmission Line
 
Performance wise - is there much difference between a folded transmission line and a folded tapped horn?

Designing and building a folded TL is much easier than a folded tapped horn. I'm having real difficulty calculating accurately the length and flare of each folded section with a tapped horn.

Any suggestions

GM 10th May 2009 05:38 AM

Yes there's a considerable difference between a TH and tapped pipe (TL) since the TH is tuned somewhat below the driver's Fs to load it to Fs while the TP is normally tuned to a 1/4 WL of Fs. The upside is it's a lot smaller and easier to build for a given driver with the downside being that in theory it will take two TPs or at least two drivers in one big pipe plus 2x the amp power to match the TH.

Another downside if you want a wide BW 'sub' is that the TP will have a deep notch at the pipe's 3rd harmonic (its effective 1 WL length), so while a great place to put an XO, it defines the TP's lower cut-off too, i.e. for an 80 Hz XO, its lower cut-off is only ~20 Hz, etc..

GM

Patrick Bateman 16th May 2009 11:38 PM

Because a transmission line is generally tapered, the rear wave of the woofer doesn't contribute more than a decibel or two to the overall output. I've found that most good transmission lines sound a lot like a sealed box.

OTOH, in a tapped horn you can see gain on the order of 3-6db over the same woofer in a sealed box.

One thing I might recommend is taking an existing and proven tapped horn design, then putting YOUR driver in it. That can be a lot quicker than figuring out a good folding scheme.

I understand how time consuming it is to fold the line; in the last design I published it took almost eight hours to tweak the volume of the line until it fit in the box. I use a 2D program called Xara, as it allows me to adjust the volume at S2, S3, S4, etc... (Using horn response, of course.)

MaVo 17th May 2009 11:44 AM

Re: Tapped Horn or Transmission Line
 
Quote:

Originally posted by mrevie
I'm having real difficulty calculating accurately the length and flare of each folded section with a tapped horn.

Any suggestions

Designing a single fold TH is really easy. Just imagine the whole horn as a single trapezoid shape, cut it in half in the middle and put the two pieces next to each other, so that they form a rectangle. As for a double folded one, you can find a good explanation here: http://www.volvotreter.de/dl-section.htm I build my horn by this and it works just like it should.

Patrick Bateman 17th May 2009 07:38 PM

Re: Re: Tapped Horn or Transmission Line
 
Quote:

Originally posted by MaVo


Designing a single fold TH is really easy. Just imagine the whole horn as a single trapezoid shape, cut it in half in the middle and put the two pieces next to each other, so that they form a rectangle. As for a double folded one, you can find a good explanation here: http://www.volvotreter.de/dl-section.htm I build my horn by this and it works just like it should.

If you have the space for a very large box, and a low F3 is important to you, a conical tapped horn is easy to fold. But if you want to keep the box size small and flatten the response, then it gets trickier. Here's some food for thought here.


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