School project, small driver but "big" enclosure

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Something like this:
10F_8422-03Urussie.jpg


The purpose of this is to have something to write about, relating to the physics and math subjects in school. The idea is to use a small driver, like 3-4" and use a big enclosure to amplify the sound and extend the bass.

I don't want to build a 300l cabinet that requires extreme woodworking skills. I'm more looking for something in the picture above. Does not require extreme skills yet it could provide me with lots of things to write about (like pipe resonances and such) and also achieving a good sound.

The budget is maximum 500SEK per driver, that equals ~$75/~€60/~£47

The finished product is not important as the work and writing, so therefore I'm looking at pretty cheap small drivers.
 
Something like this:
10F_8422-03Urussie.jpg


The purpose of this is to have something to write about, relating to the physics and math subjects in school. The idea is to use a small driver, like 3-4" and use a big enclosure to amplify the sound and extend the bass.

I don't want to build a 300l cabinet that requires extreme woodworking skills. I'm more looking for something in the picture above. Does not require extreme skills yet it could provide me with lots of things to write about (like pipe resonances and such) and also achieving a good sound.

The budget is maximum 500SEK per driver, that equals ~$75/~€60/~£47

The finished product is not important as the work and writing, so therefore I'm looking at pretty cheap small drivers.


Fostex FF85WK? - might not necessarily work in the pictured style, but maybe something like the Woden Vampyr?
 
Seems like a simple transmission line project with a cheap speaker if you are just trying to demonstrate the principles here. Would be a fun project in school and some easily cut wood from the wood shop and some glue. Another easy thing is to use round plastic pipe and one 180 degree bend or two 90's and some pipe glue with a flange to mount the driver to the tube.

A second idea, just about as simple is to install the speaker in the middle, actually offset so you have two different length and you have a twin tuned transmission line a la a boss wave radio design. Each length is set to a different frequency and you have two frequencies instead of one emanating from the tube ends.
simple to calculate the tuning frequencies and so it also becomes a math problem for the students to solve.
 
Last edited:
Seems like a simple transmission line project with a cheap speaker if you are just trying to demonstrate the principles here. Would be a fun project in school and some easily cut wood from the wood shop and some glue. Another easy thing is to use round plastic pipe and one 180 degree bend or two 90's and some pipe glue with a flange to mount the driver to the tube.

You've got it!

The idea with pipes seem interesting, and would require less woodworking but still provide a good sound, I guess? Is there any limit to how long the pipe can be? I mean, I have no problems making it several meters long but with many bends. I was thinking of setting maximum height to ~180cm just to reduce handling problems :)
 
Well, it's a school project and since I'm studying nature science the main focus of the project is not the actual construction process. What matters is documentation and researching about what I've done.


Good opportunity then to document your study of, and use of formulas and math related to Quarter Wave behaviour*

You could do far worse than to immerse yourself in the work of Martin King, to name only one

*fortunately I "have guys" for that, otherwise the math would get embarrassingly mangled - I'll just stick to slapping together boxes made from other folks' designs
 
Good opportunity then to document your study of, and use of formulas and math related to Quarter Wave behaviour*

You could do far worse than to immerse yourself in the work of Martin King, to name only one

*fortunately I "have guys" for that, otherwise the math would get embarrassingly mangled - I'll just stick to slapping together boxes made from other folks' designs

Yes. I just started with wave studies in physics class talking a bit about standing waves, pipe resonances and such and that's the area I want to "dig deeper in" and construct something using the principles of it.
 
What level of the Physics and mathematics?

How deep into wave mechanics and math are you?

If you have some calculus, the math is not difficult. Look at the Helmholtz resonator and it's equation. It all starts here.

Perhaps the simplest is what I made: a37" straight pipe using a good (but) cheap co-axial. With a proper cross-over, quite capable. TLs, BRs, horns, etc all rely on the Helmholtz equation at some point. These things are ridiculously easy to build, and rely on the same math.

So your efforts will be spent in the documentation aspects of the project and the correspondence of the end result to theoretical performance, just remember that the output will be into "4-pi" space, not "8-pi" space. So the length of the TL should be halved.

MJ King's work (while helpful and of great use to folks concentrating on completed projects and perhaps less theory), would not help you demonstrate your understanding of wave theory. Your time would be better spent developing the math from first principles, and why you might limit the solution to "4-pi" space. This requires that you differentiate between the Physics (where boundary conditions help you limit the solution(s) to those conditions) and Mathematics . Remember that Physics is NOT Mathematics .
 
Last edited:
A good suggestion...

...zobsky.

BIB works with a number of different drivers. If as most students Rullknufs is cash poor, I'm sure there are cheap (as in inexpensive and respectable sounding) available to him (or her), or if Dave was stating that Ruffknufs has some EL70 drivers then use those.

I don't know the work of Scott personally, but whatever Dave suggests is worthy (Dave and Scott collaborate on many if not all designs and if he thinks a lake series project is worthy, give it a try). Dave has never steered me wrong.

To help keep costs down, perhaps suitable off-cuts can be had cheaply. Then the money could go to decent binding posts and internal wiring.

Dave et al: As an aside, sorry guys for not phoning the Van Isle DIY 'fest on the weekend. Had I been able to attend, I wouldn't have due to a recent death in the family. I hope all had fun.
 
Perhaps? Metronome?

GM: Okay, definitely. Use off-cuts

Bigun: Metronome?
So many designs, only so much time...

Rullknufs: I'd suggest the simplest project possible (least amount of time choosing a project) and the most time correlating between the theory and the results.
 
My vote goes to pvc transmission lines. For mathmatical principles(over sound aesthetics etc) you could easily demonstrate changes in pipe resonance etc by leaving one or more joints un-glued and having different lengths of pipe available to swap. You could then easily show pipe resonance at different frequencies, and you could also learn for yourself the effects of length in transmission lines. You could use reducers to change pipe diameter, disassemble and stuff with dacron etc(to demonstrate resonance absorbtion) and after all this you may find yourself a favourite configuration and glue it up.

You could easily demonstrate different effects of pipe resonance/standing waves having the driver at one end and measuring, and having the driver part-way along the pipe using a 'tee' instead of an elbow. If you have a mic/usb setup, you could measure changes in frequency response due to the various lengths yo could make and back that up with calculations etc(easy points here). When measuring with the driver at part way along the pipe, get a cap for the pipe and put it on one end, swap it or leave it off altogether.

I like an idea using several elbows at the bottom to make a 3/4 to full circle which will act as its own stand ;)

Goodle "laying pipe with audio lego" to see some other experiments wth pvc :)
 
Last edited:
As Dave suggested earlier - Lake Series Windermere - essentially the same format of twin pipe resonant air coupler as in the original post. Designed for the EL70 that you already have, and Scott has already run all the numbers, so all that's left to do is build.
 
Lunchietey,
My vote goes with this idea. It is the simplest idea and will teach some real basic science about resonance and tuning. Just copying a design from someone else because it is designed to sound good doesn't seem like it was the intended purpose of this project. Learn by doing, it is so cheap to do this with plastic pipe and what can you hurt. Limit the input power and you can try every permutation you can think of. The Tee pipe idea is a brilliant extension of what I first proposed. Just make a simple flange to connect to it and mount the driver. From there you could do anything including adding a second tee just to see what happens with three pipes or more. This is a project that you could use over and over and teach some simple math and physics. Just don't call it a Bose pipe....
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.