Thanks you ! I've spend some time on finishings 
Tweeter response on axis is very flat and the natural roll-off help a lot for filtering. Acoustics centers are aligned !
As a draft I've use only one cap to reach LR12@2000hz !! (tweeter frd contained in 2,5db from 2 to 20k)
In few week I'll measure polar response to design a proper XO...
Amazing open work from AugerPro ! Thx you
Tweeter response on axis is very flat and the natural roll-off help a lot for filtering. Acoustics centers are aligned !
As a draft I've use only one cap to reach LR12@2000hz !! (tweeter frd contained in 2,5db from 2 to 20k)
In few week I'll measure polar response to design a proper XO...
Amazing open work from AugerPro ! Thx you
thanks s, I remember having seeing your progress on a french forum if my memory deserves me well, but I wasn't sure. The new satori woofer seems sounding fine too with the few testimonials we had here (HifiJim, HifiCompas, ...), it gaves me also the idea to use it in my actual under development 3 ways classic while I have not chosen yet the tweeter tipology yet. Ah it will not looks as pretty as yours !
!
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Finally done working out of town, so now I can get some testing done and answer all the questions piling up.
I've started some designs for the Scanspeak D3004/6600 and R2904/7000. These will all be 6.5" width mouths and greater as I've found these large diaphragms just don't behave well in small waveguides. And with the extended low response and great HD behavior, it just makes sense that most people would be looking to cross these tweeters low. I'm also going to revisit circular mouths. When I first started testing performance went up a lot when I switched to elliptical mouths, but other design properties were still unrefined and so I want to make sure elliptical is still the way to go with my current knowledge. Also, I've seen some people get reasonable results with tweeters I've used on circular waveguides like the Visiton, and I want to understand why that is.
First up are the 6.5" waveguides:
The circular mouths are looking pretty good. I'll need to continue this investigation and create versions for the other tweeters I have once I nail down some best practices. Another thing to note is I'm going to improve the tweeter/waveguide interface. Right now there is a bit bigger gap than I'd like right at the throat.
I've started some designs for the Scanspeak D3004/6600 and R2904/7000. These will all be 6.5" width mouths and greater as I've found these large diaphragms just don't behave well in small waveguides. And with the extended low response and great HD behavior, it just makes sense that most people would be looking to cross these tweeters low. I'm also going to revisit circular mouths. When I first started testing performance went up a lot when I switched to elliptical mouths, but other design properties were still unrefined and so I want to make sure elliptical is still the way to go with my current knowledge. Also, I've seen some people get reasonable results with tweeters I've used on circular waveguides like the Visiton, and I want to understand why that is.
First up are the 6.5" waveguides:
The circular mouths are looking pretty good. I'll need to continue this investigation and create versions for the other tweeters I have once I nail down some best practices. Another thing to note is I'm going to improve the tweeter/waveguide interface. Right now there is a bit bigger gap than I'd like right at the throat.
The T25B circular waveguide response looks smoother and simpler to EQ than the elliptical guide, and the off-axis output also seems more consistent. Nice work! Do you know why the traces are bunched up at 13 kHz?
If someone wanted to get extra sporty with an active crossover they could use a Linkwitz Transform on the low end with Fc = 1600 & Qtc = 0.7, and maybe F0 = 1000 and Qt0 = 0.7, to sort out delay and amplitude issues near the xover point. The high end rolloff looks dealable with a simple 6 dB / octave HF boost and a +2 db with Q=1.4 at 13 kHz.
If someone wanted to get extra sporty with an active crossover they could use a Linkwitz Transform on the low end with Fc = 1600 & Qtc = 0.7, and maybe F0 = 1000 and Qt0 = 0.7, to sort out delay and amplitude issues near the xover point. The high end rolloff looks dealable with a simple 6 dB / octave HF boost and a +2 db with Q=1.4 at 13 kHz.
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Something in between the two seems like it would be best. I'll have to look into it.
Maybe this might be a case where a phase shield would do the trick since speed of sound in beryllium is about 13,000 m/s so the tip of the dome will be at the same position as the periphery -- but secondary radiation from the waveguide entry edge around the tweeter dome could interfere with the on-axis a bit and possibly sum at moderate off-axis angles. I'd guess about a centimetre diameter would do the trick, with perhaps four struts at 45, 135, 225, and 315 degrees for rigidity. Just spitballin' here.
Interesting about the phase shields. I wonder whether that might not be caused by the wavefront simply diffracting too promptly around a flat phase shield and interfering with the main wavefront? Maybe something like a short golf tee could direct the wave in a more useful direction.
Also, a closer look at the Visaton WG148 shows the throat has a short flare from almost parallel walls to the waveguide angle, which seems to help in the high range.
Or perhaps both those ideas might play well together.
Also, a closer look at the Visaton WG148 shows the throat has a short flare from almost parallel walls to the waveguide angle, which seems to help in the high range.
Or perhaps both those ideas might play well together.
Using ATH I modeled an OS contour -somewhat like the Visiton- and it modeled worse. But, that model only holds for metal domes, fabric are too hard to simulate. And all of the domes that worked well on the Visiton that surprised me were soft dome. So I'd like to explore an OS-like contour just for these soft domes.
I have a question- it looks like the 6600 hits above 90db at 1khz, which is higher than most that I've seen you post. Are these test standardized in such a way that I might be able to say that this tweeter would be more sensitive? I'm still building my first set and don't have anything I can listen to yet, but my target is home theater so if I can get closer to 92/93 db at one watt then I'll be really happy.
Brandon,
I am sure you have answered this before, but as STL files don't have measure units integrated in the file, and we use the metric system, I would like to confirm that all the sizes I get are in inches.
For example, the 4 inch WG for the SB26 (wo PS) once opened measures 48 milimiters wide. I can only assume that the correct size for this WG is 4,8" wide. When measuring how tall it is, I get 7.212 milimiters (wo the portruding cylinders in the back) so this is 0.72 inches tall?
Cheers.
I am sure you have answered this before, but as STL files don't have measure units integrated in the file, and we use the metric system, I would like to confirm that all the sizes I get are in inches.
For example, the 4 inch WG for the SB26 (wo PS) once opened measures 48 milimiters wide. I can only assume that the correct size for this WG is 4,8" wide. When measuring how tall it is, I get 7.212 milimiters (wo the portruding cylinders in the back) so this is 0.72 inches tall?
Cheers.
I had similar issues with the scaling on my end; the size on the stl viewer did not make any sense. The way I made sure that I had the proper scale was measuring the throat, as it has to be 1" or 25.4 mm. That is the trick I use when sizing does not make sense ( look for a known measurement and find out if it is in inches, 1/10" or mm)