Oblate Spheroid Waveguide - Consolidated Construction Thread

[gedlee]

I looked into this some months ago for all these same reasons. It is very limited in its cutting ability - more of a toy. Its not ready for any heavy material, but the idea is very cool.

[Patrick Bateman]

Originally Posted by bwaslo

Patrick/John-- how thick of material can this thing cut? Could it do layers of wood veneer?

Bill,

I think cardstock is as good as it's going to get. At my audiopsychosis forum I posted some info on how to do complex shapes with the paper cutter.

Like this:



Basically you would:

1 - make a model
2 - print it
3 - assemble it
4 - fiberglass it

Loudspeakers would be ideal for this, because you could glass the *inside* of the cabinet, so the outside would be nice and smooth. (Since the paper cutter is capable of doing complex shapes that are way beyond what we could do by hand.)

Best of all it's repeatable. So if I make a waveguide model, I can crank 'em out as many as I'd like.

[makingmoney]

Originally Posted by _Wim_

I also did something like this a while ago when I bought a pair of geddes 12" waveguides and was building the speakers attached in this picture. I have attached the document as a zip file. I copied information from several threads, and made sort of a FAQ-document. I hope the original posters do not have a problem with this document. I tried to add their name as much as possible, but sometimes I forgot.

Have fun reading (it is still 34 pages long).

Thanks for the 34 pages. I had saved many of those as bookmarks before reading your doc.

Here's my 10" OSWG attempt:


B&C 10PS26
B&C 250-8
DDS CFD ENG 1-90 Pro OS Waveguide

I don't know if the exit angle of the B&C 250 matches the throat angle of the DDS OSWG.

I finished (for now) the xover, so my next project will to redo the box so it's all enclosed similar to the Nathan. Xover will be outside the box mounted on the back outside with the amp (bi-amped) with ClassDaudio amps mounted on the back, low heat and no fan noise.

My xover story:

I started by figuring one out my self but it sucked.
So I went to econwave sites and tried a Zilch type xover. Sounded better.
Got a Dayton EMM 6 mic and a xenyx 502 pre and used HolmImpuse free software and measured what I was getting and played around with many versions.

This was basically one of the best I saved (Holm crashed a few times and took out many "saved" FR graphs).
It was taken about 2M from the speaker at my listening position against a wall.
Lots of reflections going on. Below 100hz is the lumpy sub/room FR.
Zilch type filters sounded very good.
1/6 octave shown:



I also tried backward engineering a Nathan xover from photos of them on various sites. The xover changed in every photo I could find. A work in progress. Also got a couple of schematics, all different. Especially the 3 zobel type filters used. Tried a few using parts on hand for the zobels, some worked better than others. I don't think any are the latest versions, most info used was 1-3 years old. Some filters were cap first next one resistor next one inductor first. Final version I decided to follow Zilch's idea of using all three zobels in the same order, it improved the sound a lot!

But...I couldn't measure any significant FR difference. Kind of like adding a couple of teflon caps and Mills resistors. Improved clarity, less grainy sound but no meaningful diff with a simple FR.
Moving my mic 3" left or right to imitate my ear positions had bigger differences. Also added 1-1/2" 30 PPI reticulated foam in the throat up against the phase plug which rolled off the highs a bit and cleaned up some sound.
Shown left, center, right at 1/6oct:


Here's my attempt to compare my lumpy 1/6 oct FR (with sub) to Nathan FR (trying to keep scaling the same):


My taped up cardboard baffle improved the sound but no measurements yet. Hearing this version I decided to go the roundover baffle route out of MDF.

[DJNUBZ]

Does anyone have an .stl or .dxf file of an OS waveguide they could post up?