As Geddes has documented on here, dome tweeters are not ideal for waveguides or horns. As I understand it, the main reason is that the diaphragm shape is wrong.
For instance, the tip of a 1" soft dome is 1/2" closer than the edge. Half an inch probably doesn't sound like a lot.
It is.
A pathlength difference of just one half inch will create a dip at 13,500Hz. This is because 13,500Hz is one inch long, so the tip of the dome will be one half wavelength out-of-phase with the edge.
The solution I've been using is to horn load the SB Acoustics SB19. Due to it's 3/4" dome, the dip is 'pushed' all the way to 18khz.
JBL uses a different solution. If you look at their waveguides with domes, the dome is 'squashed', basically it's only a fraction as tall as a typical dome tweeter. And to top it off, there's a phase plug.
And you can't buy those JBL tweeters, they're not for sale.
But - I have good news! While perusing the QSC catalog today, I found that they're selling a very similar item, for eight bucks.
This might be a great option for someone who's looking to do a waveguide project, but doesn't need the extreme efficiency of a compression driver (or the price tag.)
QSC SP 000061 00 Tweeter for AD S52 | Full Compass
Also, I'm willing to bet this is an OEM driver made by B&C. Here's why I think this:
1) QSC seems to use B&C and Celestion for the most part
2) the numbering scheme on the driver is the same that B&C uses
Not too shabby for $8
For instance, the tip of a 1" soft dome is 1/2" closer than the edge. Half an inch probably doesn't sound like a lot.
It is.
A pathlength difference of just one half inch will create a dip at 13,500Hz. This is because 13,500Hz is one inch long, so the tip of the dome will be one half wavelength out-of-phase with the edge.
The solution I've been using is to horn load the SB Acoustics SB19. Due to it's 3/4" dome, the dip is 'pushed' all the way to 18khz.
JBL uses a different solution. If you look at their waveguides with domes, the dome is 'squashed', basically it's only a fraction as tall as a typical dome tweeter. And to top it off, there's a phase plug.
And you can't buy those JBL tweeters, they're not for sale.
But - I have good news! While perusing the QSC catalog today, I found that they're selling a very similar item, for eight bucks.
This might be a great option for someone who's looking to do a waveguide project, but doesn't need the extreme efficiency of a compression driver (or the price tag.)
QSC SP 000061 00 Tweeter for AD S52 | Full Compass
An externally hosted image should be here but it was not working when we last tested it.
Also, I'm willing to bet this is an OEM driver made by B&C. Here's why I think this:
1) QSC seems to use B&C and Celestion for the most part
2) the numbering scheme on the driver is the same that B&C uses
Not too shabby for $8
Have you seen the ring radiators from Vifa/Scanspeak? They`re somewhat flat and have a phase plug, not bad for a waveguide use 
. Focal have a series of inverted dome tweeters which would be more like a CD, the TC90 and its siblings. I`ve had an XT25 which work nice in a shallow waveguide, such as the WG300 from Monacor and have had one of the first versions of the TC90 but its surrounds failed after some three or so years abuse.
http://static4.shop033.com/resources/B2/166322/picture/DF/85019103.png
. Focal have a series of inverted dome tweeters which would be more like a CD, the TC90 and its siblings. I`ve had an XT25 which work nice in a shallow waveguide, such as the WG300 from Monacor and have had one of the first versions of the TC90 but its surrounds failed after some three or so years abuse.http://static4.shop033.com/resources/B2/166322/picture/DF/85019103.png
I really like Seas 27TDFC in Seos 8 waveguides.
I currently have them in a Impulse H6 inspired project.
I'm in the middle of a Impulse H2 inspired project and I am going to use the same combo there.
Further down road I may have a look at the Scanspeak D2608/913000...
I currently have them in a Impulse H6 inspired project.
I'm in the middle of a Impulse H2 inspired project and I am going to use the same combo there.
Further down road I may have a look at the Scanspeak D2608/913000...
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There are lots of dome tweeters that are flatter. Having a mask in front of the dome just complicates wave propagation.
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Personally, I wasn't able to make the RS28 work on a waveguide. Basically the diaphragm is large enough that getting to 20Khz is already a problem. (The 'stock' RS28 includes a phase plug.)
I think it *might* be possible if you took it apart, made a new faceplate and phase plug that's integrated with the waveguide.
But I've had much better results with tweeters under 1" in diameter.
Here's the Seos 8 with an RS28:
Hello,
This is the vertical or the horizontal dispersion ?
Hello,
This is the vertical or the horizontal dispersion ?
It looks like on a single axis with phase
It's called black MDF, its colored through. Its relatively pricey around 38 euros per square meter (the black one, other colors may depend).
Just an example:
Coloured MDF | Sonae Arauco
Greetz Swany.
Just an example:
Coloured MDF | Sonae Arauco
Greetz Swany.
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