Open source Waveguides for CNC & 3D printing!

augerpro

Member
2006-08-27 11:02 am
New waveguides! Bliesma T34B looks pretty good out of the gate. I think I've finally nailed the throat for the Scanspeak ring radiator, so I'll be expanding to other sizes and shapes now. The Scanspeak dome is a bit tougher nut to crack. But I'm going to move to a different contour, I suspect fabric domes work better in OS contours. Unfortunately, my Peerless DA25TX had a resonance at 16khz, must be defective. I have another on order.

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augerpro

Member
2006-08-27 11:02 am
Awesome work augerpro on the new waveguides! The Bliesma T34B is looking really good! As expected the large chamber causes the waveguide to provide only ~6dB gain vs the 8dB gain on the T25B due to the much smaller chamber optimizing for reactance anulling.
Yeah pretty encouraging first result. Weren't you looking to design a 12" for the T34? Any progress? Should be able to model it in ATH/ABEC pretty easily.
 

bcodemz

Member
2014-02-21 1:19 am
Yeah pretty encouraging first result. Weren't you looking to design a 12" for the T34? Any progress? Should be able to model it in ATH/ABEC pretty easily.
Yes I'm gonna want to design a 12" version. I can't wait to do it, but I've been extremely busy with the holidays and stuff. I will have significantly more free time in a few months and then I'll tackle it hard core. I didn't get to do much audio stuff this year, oh boy am I gonna make up for it next year!
 

bcodemz

Member
2014-02-21 1:19 am
hello bcodemz,

What part of the WG are you referring to with "chamber"? Is that the section of the WG immediately connecting to the tweeter structure?

I'm referring to the rear chamber behind the tweeter dome. For horn loading generally you want the rear chamber to be as small as possible so there is a better match between the pressure experienced by the driver in the rear chamber vs in the throat. A better match results in more efficient horn loading. This is why in front loaded horns you see the driver crammed in as small of an enclosure as possible. You'd think that's hurting low end efficiency, but it's actually increasing low end efficiency.

Most tweeters have a large chamber in order to improve low frequency extension and get a lower Fs. The T25B is one of the tweeters that does not have a large rear chamber (roughly 1/5th in volume of a T34B if my math is right), and therefore you see a maximum of 8dB of waveguide gain in a 6.5" waveguide. But with other tweeters like the Scanspeak's, SB26, T34B, etc, you only see ~6dB of gain in the same 6.5" waveguide. They have larger chambers, which is evident since a lot of those tweeters are flat to 1KHz whereas the T25B is barely flat to 2KHz.
 
Hello folks,

I'm working on my 6+1 bookshelf loudspeaker.
A 5.75" waveguide with an SB26ADC and a 6" SB Acoustics MW16
For the moment I've only made an on axis measurement to make a quick & dirty dsp XO. A [email protected]

For people that already done some polar measurement (I should do mine next week), do you think I should use another XO ?
Maybe an LR24 first ? A bit lower maybe ?
I'm looking for a smooth DI...

Anyway, if you have any comment on that, I'll enjoy more "intellectually" my week-end, before propers measurements next week !
++
 

augerpro

Member
2006-08-27 11:02 am
Refined a couple of the previous designs and measured them today. Also added the first variant for the Peerless DA25TX. I'm surprised by the Peerless, it's a small dome which has worked well for me, but this has a big dip on axis. I would have expected it to measure very close to the SB26ADC given how similar the domes are. I may have to start working in ATH/ABEC for this one to figure out what works.

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I’m curious, what do you think of this tweeter?

https://www.parts-express.com/Peerless-OC25SC65-04-1-Textile-Dome-Tweeter-264-1018
I’m not sure what makes a tweeter suitable for use in a waveguide, but this one has a sensitivity of around 96db; one of the highest I’ve been able to find for a dome tweeter. It is also very cheap, and I wonder if we could mate it with a couple of reasonably sensitive woofers to create something with high output from a cheap amplifier. Does this seem like something worth pursuing, or is it just too low-end?
 

jcga

Member
2004-06-11 7:49 pm
Paris
Yes, but give me a week. I often use shims to see how that affects things, and in this case they were better, so I need to incorporate that additional depth into the model.

Take your time, no rush here, grand son at home... quite busy days until end of the week !
Anyway, thanks very much for all your contributions
 
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