3D printed waveguides

[TN Allen]

I hope you won't mind a few questions? I'm curious about the cross section, was it an arc tangent to the baffle surface, ending at the throat, and did you remove the stock face plate? Do you recall if it was milled in a terrace pattern, using a step down, for example .01", or was the milling done stepping over? Did you use MDF?

What you've described is similar to what Takitaj found a few years ago testing an early oval guide I did, coincidentally he had done a shallow oval(as I recall) guide that tested similarly. Ryan Bouma found the same result testing a very similar guide. As DanP pointed out, I hope I'm paraphrasing correctly, there is no magic in guide geometry, depth and contour can be manipulated to produce a desired effect.

[augerpro]

Pete would you have some measurements of just the tweeter?

[Pete Schumacher]

Check the link in my signature to the 8" 2-way. Toward the end of that thread I mention the 1" deep guides pictured below. I made an elliptical as well as a round guide. Both ended tangentially to the baffle surface and carried simple circular arcs to the throat opening. Here the elliptical has been sanded (but not sealed). Completely smooth to 400grit in only 10 minutes.





Here's some response plots from page 22 of that thread. The RS28A in the elliptical is the green plot. The blue is the 27TBFC in the elliptical. The red is RS28A in the circular guide. To me, the red plot is closest to the ideal with the most extended top end response and as you can see, about 10dB of "gain" compared to the response at 15KHz





And finally, the system response with the current crossover.

[badman]

looks a lot like Behringer Truth 8031! Not a bad thing.

[greywarden]

[Face]

For those who want a WG for a 7-8" woofer, why reinvent the wheel?

http://www.diysoundgroup.com/plastic-seos-12/seos-8-tweeter.html

[Pete Schumacher]

For those who want a WG for a 7-8" woofer, why reinvent the wheel?

http://www.diysoundgroup.com/plastic...8-tweeter.html

Sometimes you want a baffle that looks seamless.

I've even worked up a couple of kits using the SEOS-8 for the RS225P and the 8BG51 and RS28A. It's a nice little guide and works quite well.

But I think I like my shallower guide even better. But it does require more work to finish it than using the SEOS.

[TN Allen]

Guides in solid wood can be very attractive, especially if it is a double guide combining tweeter and midrange, or tweeter and small woofer. Shrinkage and expansion can be a minor problem, as the openings vary out of round ~1-2%, changing the throat from round to oval, but that is not too noticeable. I don't know how it affects the guides effect on sound.

I agree though that if something is available off the shelf that works, printing new guides makes no sense, given the cost and time, 3D printing is a slow process. The surface finish can also be a problem, it is not nearly as smooth as a molded surface, although future printing processes and filaments may improve that.

[Face]

I agree, I would love for a SEOS 8 cut in a solid wood baffle. Although, this kind of works too: https://imgur.com/8hnuKlk

[TN Allen]

Do you have one of the guides? Perhaps it can be duplicated in wood, provided it's legal to do so. I haven't worked with a guide using that rectangular shape yet, it might be interesting to do so. Could you or someone else test the result, and compare the data to the original?

[greywarden]

I've always wanted to build something similar to the Fern & Roby Beam speakers. I think that's my next project after I finish the Shockwave speakers

[TN Allen]

Greywarden,

I found the website, it's an interesting idea, do you know what is inside the cabinets, are they bass reflex, sealed, maybe T/L. It would be easy to do a quick baffle in MDF if you want to try a prototype.

tna

[augerpro]

I don't want to step on Erich's toes copying one of his designs, protected or not. Besides we're swimming in different pools as far as application.

Pete> Could estimate the AC offset in your latest speaker (with crossover in place)? When we get to the 8" guide I'm guessing we'll have trade off in depth required - probably shallowish for response, and deeper to match AC.

[Pete Schumacher]

I didn't recess the B&C woofer completely flush since the flange is so thick. So right now the offset is basically zero. If the woofer was completely flush then I think a 1.25" thick baffle would be about perfect to keep the alignment. Maybe even 1.125"

[augerpro]

If the woofer was completely flush then I think a 1.25" thick baffle would be about perfect to keep the alignment. Maybe even 1.125"

In other words the depth of the guide is the same as the depth of the baffle?