Supply is the mother of invention, tl pvc

[brucegseidner]

It is not that I am fixated on PVC or that there is some priapic preoccupation potentiating these proposals (say that 5x's in a row). I just happen to have a bunch left over from an outdoor project gone awry.

When I look at unfolded TL cabinets, or designs like the Zigmahornets or the Vampyr I can easily see building these inside a PVC tube. With vey little trouble I could whip up the endcaps and the minimal internals of these designs.

Clearly, length and placement of the driver, and the size of the vents are critical. But what of the shape. From my lay perspective there are going to be advantages and disadvantages to a rectangle versus a round pipe - all issues of mechanical resonance, zero'd out, what is the difference between the two designs.

If the Vampyr is essentially a 5.5x6.5 inch rectangle tube, what would the difference be in a 6" PVC tube?

If there were something critical about a rectangular versus a cylinder I would respect this and build the rectangular tube. I just don't know enough to think through this in an informed manner.

[planet10]

The volume of the main chamber (in Vampyr) is not an issue, but getting the ports correctly shaped is something i can't see reconciled with a cylinder.

dave

[picowallspeaker]

They work fine! At the end of the design ,listening to it , you will hear a different kind of resonance , the one (s) produced at low frequencies ,depending on the thickness of the plastic , so it is better to damp and bitumen cover all the internals.
But I like the "light" distortions of it , after all the finished speakers will weight a lot less as if they're of MDF , or you can mix the two materials , linear vs. circular shape.
The challenge is to use sections of the tubes to build horn speakers.

[picowallspeaker]

A picture is better (hope it ' ll appear! )
It is a very very short 1/4 wave , as you see , air flows like water ...as electrons flow like ants ... It needs a tweeter on the top,the only limitation is that they like to lay on the floor , and in the corners...

[Henkjan]

how about this:

http://zelfbouwaudio.nl/forum/viewtopic.php?t=8649

[picowallspeaker]

Nice , Henkjan
But I like mine better!!!
Looking at all the speakers produced ,and experiencing too , it is good to have them narrow , but the speaker mounted extruded it's too much.
It needs to have at least a mechanical and acoustical flat plane to start with.

[brucegseidner]

Lyrics by David Byrne, Talking Heads.

You guys have very forbearing spouses/significant others. I feel like I am back in the 7th grade science club.

I was thinking it would be possible to cut wood baffles and place them in the cylindrical PVC cabinet. The only change would be that instead of the long outside rectangular walls of the Vampyr I would use the pvc. Everything else would remain the same. I would calculate the volume of the main cabinet and see the difference in length using a cylindrical pipe instead of a rectangular pipe. With the baffles cut it would be a simple matter to privilege equivalent length, or volume, and a third where I split the difference. I would have 3 cylindrical cabinets to plug the internal baffles/speaker into and see what happens. Because I am mathematically "incontinent" I have to do things concretely. Is there some elegant virtual way to run these differences in a model and predict ahead of my sawing and gluing what this would do?

[gychang]

Originally posted by Henkjan
how about this:

http://zelfbouwaudio.nl/forum/viewtopic.php?t=8649

comments on the sound?

gychang

[picowallspeaker]

For me it was just bric-a-brac or recycling materials.I made my cabinets more than 10 years ago , and the project was simply expanding the area of the horn , from the narrow point where it begins till the end.
More projects are still on the paper , since I had to do the step of acquiring the knowledge to play with 3D autocad ,just to know the exact cut-off of the panels.
I'm talking about CNC routers etc.etc. something beyond 7th grade etc etc.
This to avoid the simmetrical volumes inside the cabinets.Get it? Instead of placing
a rectangular flat panel inside the tube , try to place a trapezoidal plane in it.

[brucegseidner]

To your knowledge what is the behavior of the sound waves inside a right angled tube and a cylindrical tube.

(Oh, and I do not know if you are aware that the reference to 7th grade science club characterizes us as more interested in science and less interested in social appropriateness. It is American self deprecating humor and not a criticism or some reference to lack of sophistication.) I think the two cabinets shared are very clever and I respect the originality of design. That said, they would not win the Home Beautiful award or be showcased in a wood paneled Edwardian library den with Italian Grayhounds sleeping at the base of them.