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Gaga 20th February 2018 09:00 PM

Hi Brandon,


Christoph> if you get a chance, work the sim more on the SB26ADC. Of interest: a shim at the throat to move the dome back, vertical wall radius, and to a lesser extent the horizontal wall radius - though I feel that is pretty right on.
Will do so. Try to do it during the next weekend and will come back with results soon.

Hi Ro808,

Christoff, if it's not too much of a hassle, it would be interesting to see the effect of a small area of "low curvature" (or even flat) in a (rather deep) waveguide for a hemispherical dome tweeter.
Some space of 2-4mm around the surround "to breath" > might eliminate/cancel interferences.
I'm not sure if I get your idea. Could you possibly give a rough drawing of the profile you are suggesting with rough dimensions? This will help for a simulation.


augerpro 21st February 2018 01:25 AM

4 Attachment(s)
Here are the results for SB26ADC on the 8" waveguide. Note, I usually measure with and without phase shield, sometimes with a shim between mouth and tweeter, and sometimes check vertical responses on more promising/new designs. All of this is noted in the screenshot.

augerpro 21st February 2018 01:29 AM

2 Attachment(s)
Much awaited results on the Transducer Lab N26CA! Probably the best of the bunch on the troublesome 5" waveguide. I think the squiggle around 10khz is a similar to issues I had with the SB26, might just need a small lip and/or some tape on the mounting face to stop vibration. Wish these weren't NLA, moving up in size will probably make some beautiful plots.

augerpro 21st February 2018 01:33 AM

8 Attachment(s)
Here is the TW29RN on both 5" and 8" waveguides. With pinned center it's no surprise the phase shield does nothing. The top octave has me miserable. The difference version A and B is slightly different wall radius.

augerpro 21st February 2018 02:06 AM

1 Attachment(s)
For anyone unfamiliar with the natural response of a horn loaded driver, here is the N26 after some simple filtering to flatten the "tilt":

augerpro 21st February 2018 02:42 AM

3 Attachment(s)
Roland, Christoph> here some pics to show what I'd like to focus on (other than the ever present top octave dip in the on axis response so common in waveguides):

Attachment 673037

Attachment 673038

A couple posts back I mentioned the flawed phase shield. The support rod was off-center, and so the response was different when going off axis to one side or the other. Here are the plots going the opposite direction of F above, I *assume* the response with the fixed phase shield should be the average, if so, it should look real good:

Attachment 673039

BTW you can also see the ripple below about 4khz flip flop, so all that ripple is just the baffle diffraction.

Ro808 26th February 2018 01:35 AM

Brendon, apart from the issues >10kHz these look promising, especially the elliptical.

Could you post some pics of these last 2 waveguides with the SB26ADC mounted?
Just to check the throath area: the distance of the surround towards the walls, the height of the dome vs the surround vs. the waveguide.

fatmarley 26th February 2018 06:58 AM


Originally Posted by Ro808 (
Christoff, if it's not too much of a hassle, it would be interesting to see the effect of a small area of "low curvature" (or even flat) in a (rather deep) waveguide for a hemispherical dome tweeter.

Can't remember why, but when I was experimenting with waveguides I thought a bigger gap would solve the top octave issue too.

augerpro 27th February 2018 12:50 AM

1 Attachment(s)
Roland> if I understand you, here is a closeup so you can see how much is outside the surround (about a 1mm):

Attachment 673040

It's tough to get a good pic of these, the nylon is always over-exposed

Pallas 17th March 2018 07:44 PM

1 Attachment(s)
I notice all your WG's are fully rounded. Have you noticed that Revel's waveguide for the SB26 aluminum tweeter has a vertical crease of sorts?

Attachment 673041

I don't know how much harder that would be to model, but wanted to throw it out there.

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