DIY bit to cut waveguides

[JonP]

Very cool idea, and I like the development...

Much better than my aborted attempts to do stuff with a roundover and layers of 45 deg chamfer bit cut MDF... a total pain to accurately dimension layers correctly. And, only flat profile guides possible...

I agree that using some better grade of steel would be an improvement, if only at the cutting edge, but won't even mild steel (is it?) like the angle iron alloy temper a bit? Might be worth heating it up to red, then dunking it in a bucket.. to see if that extends your edge life on your current one... (edit.. read the last post a bit closer, ah well)

I'll ask a mech type at my work about current accurate cutting tech out there, plasma, laser, high pressure water, EDM, etc... Might be a way to go, (if cheap enough) to find shops where you could give them a profile CAD file and a saw blade or piece of good sheet steel, and they'd hand you back your finished cutting edge piece.

Another innovation that looks necessary, would be some kind of dust collection box or tent around the drill press... especially for MDF! 8O That's got to be a prodigious amount of powder being created, making the guide!

[JonP]

Very cool idea, and I like the development... True DIY innovation!

Much better than my aborted attempts to do stuff with a roundover and layers of 45 deg chamfer bit cut MDF... a total pain to accurately dimension layers correctly. And, only flat profile guides possible...

I agree that using some better grade of steel would be an improvement, if only at the cutting edge, but won't even mild steel (is it?) like the angle iron alloy temper a bit? Might be worth heating it up to red, then dunking it in a bucket.. to see if that extends your edge life on your current one... (edit.. read the last post a bit closer, guess not. Ah well)

I'll ask a mech type at my work about current accurate cutting tech out there, plasma, laser, high pressure water, EDM, etc... Might be a way to go, (if cheap enough) to find shops where you could give them a profile CAD file and a saw blade or piece of good sheet steel, and they'd hand you back your finished cutting edge piece.

Another innovation that looks necessary, would be some kind of dust collection box or tent around the drill press... especially for MDF! 8O That's got to be a prodigious amount of powder being created, making the guide!
Maybe something out of cardboard, or foam core board as an extended funnel or 3sided cube, for the shop vac...

[penngray]

Concave vs. convex curves, for a start.

Yes, but I was asking more about how it impacts the sound wave.


Although the above picture seems very close to what my 1 1/4" round over bit looks like.

[frascati]

(duplicate post)

[frascati]

(duplicate post)

[BobEllis]

A caution - often a drill press chuck is mounted on a Morse taper. This means that side loads on the chuck could cause the chuck to release from the drill press quill and you'd have a missile hazard. :takecover:

Use extreme caution with cutters like this if your chuck is not held in place with a screw in the center.

[Ray Collins]

Ok...:z

[frascati]

The bit guide is inserted in the work and the work is clamped to the table before the bit is even spun. There's no other logical way to use the bit in fact so you'd have to be trying pretty hard to hurt yourself. As I mentioned in response to a concern that the bolt might come loose, if it did while cutting, or in fact if the morse taper were to come unseated as you suggest (possible, but extremely unlikely) during the use of this bit, nothing at all would happen except that the bit, the chuck, and the morse shank would stop turning in the work and the drill press spindle would continue spinning. There is absolutely no way that this could pose any hazard to anyone. There is some addtional radial load with this bit, but in combination with the 1/2 inch guide ahead of it in the wood it is not even considerable. I agree that straight radial loads like side milling would be a no no on a drill press and some guys do try this with a milling slide. Not a good idea as you point out.

[BobEllis]

OK, I see that the guide provides restraint of the bit. I hope that anyone using it will recognize that the bit must remain guided by a backer and cannot punch through the panel being shaped unsupported. I didn't pick that up the first time through.

[BigguyZ]

Ok, forgive my ignorance, but that's the reason for the post.

What benefit does a waveguide have, say over the standard housing and the tweeter being flush mounted?

Also, does adding a waveguide benefit ALL tweeters, and does the design of the speaker need to incorporate the use of the guide?

Thanks,
Travis

[cyberdiamond]

Click me here is a link that explains the waveguide principles.

[penngray]

Ok, forgive my ignorance, but that's the reason for the post.

What benefit does a waveguide have, say over the standard housing and the tweeter being flush mounted?

Also, does adding a waveguide benefit ALL tweeters, and does the design of the speaker need to incorporate the use of the guide?

Thanks,
Travis

Increased sensitivity and better constant directivity are two main features of using a waveguide. Im not sure the draw backs, maybe pushing the AC back into the baffle is an issue but maybe not.

[Bear]

maybe pushing the AC back into the baffle is an issue but maybe not.

Better aligning the acoustic center of the tweeter with the woofers is another advantage of using a waveguide in many of these designs (shallower slopes to the XO and better phase transitions).

[penngray]

Better aligning the acoustic center of the tweeter with the woofers is another advantage of using a waveguide in many of these designs (shallower slopes to the XO and better phase transitions).

Yeah, I did say maybe not because a shallow waveguide can have that advantage but deep waveguides (IE...QSC waveguides push the AC back further then the woofer).


I didnt know AC differences allowed for shallow XO slopes, I will have to figure that one out. Thanks!

[cjd]

It should be possible to balance this as well.

[frascati]

I'm among the least qualified to comment on the theoretical, or even demonstrable, value of a waveguide. There are a few people, whose opinions I put much stock in, who have found them deserving of the time and effort to implement with stock dome tweeters, particularly John Krutke whose TMM design first got my attention.

But I'll admit that I like them as much for art's sake. The waveguides in these designs just seem to intuitively satisfying me - if that makes any sense at all. Like, "hmmm, now that's what a speaker is supposed to look like". To me it's kind of a form following function exercise that ends up really working aesthetically because the pure function ends up exhibiting beauty on its own. (i know that's just a paraphrasing of 'form following function' but i wanted to emphasize it).

I've got a BMW motorcycle out in the garage that is like this. With perhaps the exception of one stamped seam in the gas tank that appears to have been included simply to satisfy the designer's own eye, there is not a single thing about the bike that was likewise just tossed in for "beauty's" sake. It's all function that works. And the bike is so gorgeous that in a field of two hundred over-chromed, rainbow hued, leathered, tasseled, machined aluminum billet adorned others it never fails to attract attention for its looks.





Image not available

Image not available

[Ray Collins]

How about a picture of your scooter?

Ray

[frascati]

Images not available


Nothing especially wrong with adornment, but sometimes it distracts from what is more important. I went to the Guggenheim museum in NYC one evening with a date. I felt a bit like I was being dragged there. I'm as appreciative as the next guy, but I've never really gone out of my way for museums when travelling. She ogled and fawned over the greatest names, Picasso, et al, and when we got to a particular exhibit that was showing that month she lost me to it. It was a collection of some of the most iconic and, well, just beautiful, examples of household appliances from about the fifties onward. Toasters, blenders, vacuum cleaners, washing machines. I was in awe, and just had to entirely give up on trying to impress my date at that point.

With few exceptions the examples chosen to stand in the Guggenheim as art displayed that intuitive beauty that emerges from good design to begin with. It's not just that they were mostly simple and unadorned - the Mies van der Rohe blocky austerity-for-art's-sake is as simple as it gets and seems mostly disfunctional, but just beautifully engineered, and beautiful for it, like the Golden Gate bridge. For some inexplicable reason, visual beauty just seems to flow from good design. It might be an instinctive reaction to the things we produce with our own hands, a sensual affirmation that we're on the right track.

[penngray]

Very cool pictures!!

The NYC public library always amazes me when I visit NYC...serious, I love the architecture!

[Ray Collins]

Great Bike! Only the tag fails to contribute to performance. I am a fan of air-cooled, horizontally-opposed engines; I guess that is why I have owned so many early Porsches and airplanes...
My favorite is a Mies van der Rohe design in Chicago; an elegant black glass and steel "Less Is More" he did for IBM. Sits between the Sun Times and the "Twin Corn Cobs". Skin and Bones architecture works for me; also like the Barcelona chair...

Ray

[frascati]

My favorite is a Mies van der Rohe design in Chicago

Oops. I'm always offending someone in the room.

[Ray Collins]

Absolutely not offended!!! Simply different tastes with the prerogative to enjoy the preference...

Ray

[frascati]

for anyone following this i'm convinced enough now to replace that first template with the second version. I made one last night and it took half the time to cut the waveguide out of MDF and left a better surface to boot. Incredibly, the edge was still very sharp afterward.

I'll post pics in a bit and revise that instructional printout above.

What I'll probably do is rewrite that printout and mail it to cjd for hosting. Thank you cjd. I'll include the skp (sketchup) file if he's amenable. That way anyone at all can download google sketchup free version and have a look at it in rotatable 3d. Sketchup is a one minute download and install with a cable connectinon and it's really fun to play with. The print to scale problems still make me want to find the programmers and introduce them to the nazi dentist from Marathon Man, but with a little steady breathing, counting slowly to ten, and earnest kludging, you can eventually get it to print correctly. Hey, it's free.

[penngray]

for anyone following this i'm convinced enough now to replace that first template with the second version. I made one last night and it took half the time to cut the waveguide out of MDF and left a better surface to boot. Incredibly, the edge was still very sharp afterward.

I'll post pics in a bit and revise that instructional printout above.

Im still looking to buy one if someone can build it

[frascati]

A few shots of the last MDF practice board.

Tweeter recess (backside of baffle) was done with a trim router to a throat diameter to meet Zaph's spec of 39mm and faceplate diameter of 105mm to accept the SEAS 27TDFC (H1189).

2 X 3/4 board. The lamination line is visible because I didn't bother to glue this one up before cutting the guide.


Images not available




...just about ready to start my project.

[dmalphur]

Very nice! I like the seamless transition to the baffle that this provides. Thank you for sharing this idea.

-David

[---k---]

Looks good! :T

[Bear]

Definitely looking good. One of the upsides of this approach, beyond it being easier to do a waveguide, is that you leave a lot more material in the baffle, aiding rigidity/structural integrity.

[frascati]

Some excellent MDF links...

http://www.pbmdf.com/CPA30/files/ccLibraryFiles/Filename/000000000729/MDF%20Start%20to%20Finish.pdf

http://www.pbmdf.com/cpa30/files/ccLibraryFiles/Filename/000000001750/Buyers-Guide-2010-Part-2.pdf

The first one is a very good read for anyone interested in woodworking.

[frascati]

Here's an updated pdf template and instructions.
FINAL BIT INSTRUCTIONS PDF.pdf

And here's a 3d file in scale to play with if you want to rotate the image, take other measurements, or even play with the profile for a different waveguide using the same design. It's an skp file that opens in Google Sketchup freeware. It only takes a minute to download and install Sketchup on a cable connection.

http://www.mediafire.com/?21yzod3iq4h

Otherwise here's a dwg file

http://www.mediafire.com/?mvn3naygcwn

...and dxf

http://www.mediafire.com/?dum3gmwnzny

...and a jpg template and instructions

[---k---]

I'm glad to see you got it all figured out and it worked out for you. I'm anxious to see a few more people try this.

[DIYDUGG]

Almire all the posts here on the DIY wing cutters - very nice!!!

My first though is to send the pdf to a custom cutter shop - thanks!

I've had some custom router bits made for other projects, it wasn't expensive, however it took several weeks.

The question about stock cutters: these are 1-1/4" and 1-1/2" roundover bits, easy to do, e.g. drilled 1-3/4" and route - need a third temporary layer for the guide bearing. They remind me of the old Morel MDT-27 and larger DA-28's

This Roman Carbide was also interesting, size vs. $$ http://toolsandmore.us/roman-carbide...r-cutters.aspx

[tweeter is the notorious xt25 driver]