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-   -   New horn in PVC (http://www.diyaudio.com/forums/full-range/78030-new-horn-pvc.html)

loninappleton 19th April 2006 09:50 PM

New horn in PVC
 
If I did the link right, the link should show a new
(by me anyways) design using PVC to make a
single driver horn.


Can we have some discussion on the merits?

The concept looks like it would work well for subs or
single driver setups. I have no idea how to model it.



Other link at Full Range Driver Forum is here (in case
I messed up the other one:

http://fullrangedriver.com/gallery/d...?album=4&pos=3

GM 19th April 2006 11:19 PM

Greets!

It looks like a coiled up Alpha TL, so easy enough to model and due to the relatively small CSA won't perform at its optimum.

GM

holdent 20th April 2006 02:25 AM

GM:
Quote:

relatively small CSA
CSA = mouth area?

According to the web site the tube structure is 14 ft long (=168")?! This is exceptionally long and implies an unrealistically low cut-off frequency for the driver used. You'd probably have much better performance by making it half the length - it certainly would be easier and cheaper to build.

It looks there's a compression chamber (CC) mated to a succession of smaller to larger diameter 90o PVC adapters make up the horn. If so you could model it as a BLH using King's excellent MathCad models (www.quarter-wave.com). The CC looks to be PVC pipe that's just larger than the outside diameter of the FE108EZ's frame (roughly 5") that immediately narrows down.

Assuming the throat is 0.5 Sd then you'll be looking for the first width to be close to 1.36" (diameter). You'll probably have to go to the plumbing store or home centre and see what sizes of PVC adapters they have and measure the length along the center. Then enter that info into the model and see how it will work. Note that the mouth area in the photos looks to be too small relative to the driver for good performance (I think that is what GM is referring to). To get a mouth area of at least 10 Sd or greater you'll need the PVC pipe to be more than roughly 14" in diameter.


Incidently the design is not like the B&W Nautilis mentioned. I believe that design is a TL with one end the size of the driver tapering down to a closed end.

No matter what it's an interesting looking design that may *just* work.

mod_evil 20th April 2006 02:49 AM

OH MY GOD!

I think it's look great, but... It seems a Transmission Line... ( http://www.t-linespeakers.org/projec...uke/index.html )

Have you some graphs about the frequency response?

It's a beautiful work!

Tehrasha 20th April 2006 03:50 AM

Re: New horn in PVC
 
Quote:

The concept looks like it would work well for subs or
single driver setups. I have no idea how to model it.
A sub would be interesting... know where I can find some 8", 10", 12" and 15" PVC?

GM 20th April 2006 09:32 PM

Greets!

CSA = cross sectional area, so it can be the mouth, or in my case I glanced at the pic and apparently 'saw what I wanted to see', a constant taper TL. Bottom line though is that even if it is a horn, the mouth is much too small to perform well by my definition, especially with such a long pathlength.

WRT large plastic pipe/fittings, it won't be cheap: http://www.contech-cpi.com/assets/Drainage.pdf

GM

loninappleton 22nd April 2006 05:01 AM

Holy Schnykies.


That's more tube than I'd ever want to deal with.


Yes there is some difference in the pipe widths
but is that necessary to calculate the line?


Can one diameter be used as in a straight TL?

And would extra length then go from quarter wave
as in the MJK calculations to half and beyond?


I'd be interested in making just one with the PVC
I have laying around from the last build.

GM 22nd April 2006 06:35 AM

Greets!

Yes, if you're going to replicate it.

Yes, see my first post.

The fundamental will be 1/4 WL no matter how long it is.

Then do so. Fp will be ~13560"/4/line length in inches.

GM


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