This afternoon a measurement session possible, primarely to check if driver mounting went ok.
Tweeter at 100cm, with mounting holes and edge covered with tape:
Serious spike at 28kHz, hump at res-frequency. But else ok.
Distortion via ARTA at 46cm en 2,84Vrms:
Not bad ;-)
Tweeter at 100cm, with mounting holes and edge covered with tape:
Serious spike at 28kHz, hump at res-frequency. But else ok.
Distortion via ARTA at 46cm en 2,84Vrms:
Not bad ;-)
Thanks for the heads-up. Turns out the surround is less than one thickness of painter's tape, .005 inch / .125 mm, so two layers of painter's tape on the waveguide would be more than adequate. Cutting away 1 7/8 inch / 48 mm diameter (I used my tweeter mount as a template) from the centre gives lots of room for the surround, which is about 1 5/8 inch / 41 mm diameter.
Hi and thanks for all the hard work! Please donate on @augerpro gofundme!
I built some active speakers a while ago and I wonder about the benefit of added the 4" elliptic with phase shield waveguide (4x.65 vB 82 ps) on my Satori TW29TXN tweeter. The 4" is the largest I could retrofit. My goal would be to have constant directivity up to ~15khz (instead of the ~7khz I get right now).
Could I reach my goal using this waveguide?
If yes, I am worried about damaging the dome while installing the waveguide, are there any special precautions to take? Sorry if this was previously answered.
Thanks again.
Speaker: TW29TXN, MW13TX, 2xPeerless 830667, Hypex FA253. See pictures for current baffle and current directivity measurement.
I built some active speakers a while ago and I wonder about the benefit of added the 4" elliptic with phase shield waveguide (4x.65 vB 82 ps) on my Satori TW29TXN tweeter. The 4" is the largest I could retrofit. My goal would be to have constant directivity up to ~15khz (instead of the ~7khz I get right now).
Could I reach my goal using this waveguide?
If yes, I am worried about damaging the dome while installing the waveguide, are there any special precautions to take? Sorry if this was previously answered.
Thanks again.
Speaker: TW29TXN, MW13TX, 2xPeerless 830667, Hypex FA253. See pictures for current baffle and current directivity measurement.
Attachments
The answer to that is no as the Satori domes begin to narrow quite a lot as frequency rises. They are wide shallow domes with a big surround. The geometry is not conducive to wide dispersion at very high frequency.
augerpro: I meant routing a new cutout in the actual baffle to fit the waveguide. The stock tw29tx is a 103.8mm circle, the 4" elliptic waveguide is 103.1mm high (121.4mm wide) so it would fit height wise between the mid and the top woofer. If I do this I will rework the crossover to match directivity at the mid/tweeter crossover point, I was wondering if I could improve the top end dispersion (above 5khz) with a waveguide that has a phase shield.
fluid: By eyeballing the hificompass compared to the somasonus measurements I thought the version with the phase shield would help a bit but it seems I should go with a different tweeter instead. I would eventually like to get a horizontal dispersion result in the top end similar to the Revel PerformaBe series.
Thank you both for your input, my understanding is that a waveguide will not help me get what I am looking for.
fluid: By eyeballing the hificompass compared to the somasonus measurements I thought the version with the phase shield would help a bit but it seems I should go with a different tweeter instead. I would eventually like to get a horizontal dispersion result in the top end similar to the Revel PerformaBe series.
Thank you both for your input, my understanding is that a waveguide will not help me get what I am looking for.
Waveshaping devices in front of the tweeter can help to widen the directivity at high frequencies but it needs to be quite heroic to undo the beaming that comes from the Satori drivers intrinsic shape. Lots of trial and error or relatively sophisticated simulation is needed to get the right geometry. The simpler solution is to use a tall dome in the right kind of waveguide. There aren't a lot of options that fit and some like the Bliesma T25A are difficult to get right in a waveguide. The T34A can be very wide and even almost all the way to 20K but the waveguide has to be quite large.
Not enough. I would go for a proven tweeter/waveguide combination and the best one is T25B + printed WGs.
T25A has mainly one reason - get as much off axis sound as possible. But there is no working waveguide for it.
So it's the opposite as with the T25B which is the best one for controlled sound.
As you don't need any of the special performance of the T34A for this project I would give the money to the T25B (which is also the best sounding tweeter I know).
Having constant directivity is more about the driver and waveguide shape in the <10KHz range. Above 10KHz the phase shield can help. For example circular profile waveguides have a more gradual roll off as frequency rises while oblate-spheroid profiles have more of a shelf shape to the roll off. The big surround is the main issue I suspect, more than the fact the dome is shallow. IME shallow domes work well in waveguides, while highly convex or inverted domes are more tricky to play with a waveguide.
If you 3D print, ou could try covering a portion of the surround with the waveguide throat, IME it can work.
If you 3D print, ou could try covering a portion of the surround with the waveguide throat, IME it can work.
Constant directivity seems to mean many different things to different people. I would say that the flatter the DI the more constant the directivity is. Dome tweeters in waveguides don't often lend themselves to producing a flat DI naturally. This is of course a simplification and there are always exceptions and options.
A big surround does make harder as it increases the effective radiation diameter which is one factor. The old idea that a bigger dome beams more does have some truth in it, but there are other factors that can come into play to negate it. Tall domes are tricky in waveguides because they require a specific geometry to work which is often not where anyone starts. All of these things are quite easy to see in simulation.
Tenson gives a good hint above how to make it work better. It can be done, but the T34A does it naturally without any messing around.
The T25B is an easy driver to use in a waveguide. The small inverted surround and overall narrower diameter help to push the natural beaming behaviour up higher than occurs in the Satori domes without any extra effort. The dimensions lend themselves to a slighty rising DI in the waveguide being happy at +/-60 degrees nominal wall angle. To push the high frequency dispersion wider then it is waveshaping or the right shaped tall dome like the T34A.
This is just a description of what you can get with what. There is no suggestion that one is better or worse than the other. I have both the T34A and T25B sitting here. The waveguides I have designed for them are different and are tailored towards what the driver seems to want to do and not force it to what I want it to do. Maybe one day I will have an opinion on which I like better
I've never considered the T34A before you mentioned it. Looking at the dimensions it's almost a perfect drop-in replacement to my TW29TX
.I have also seen your waveguide for the T34A in post #1266 which will also fit my enclosure. Is the dispersion modeling from this post for the T34A waveguide shared in post #1266?
@joep1 if you are still around, feel free to direct message me if you want to chat as we could end up with the same mid/tweeter/waveguide trio thanks to this great community.
Thanks to all who commented.
No that waveguide is about 150mm wide for the profile, 168mm when the mounting ring is attached. I don't have an equivalent simulation for the one I made for joep1, that was an infinte baffle simulation which is not comparable. The small waveguide works better than no waveguide so it will stop a little bit of edge diffraction and smooths the pattern out in comparison to the bare driver. As it mounts within the same footprint it is relatively convenient. If you want the widest radiation in the smallest footprint it's a pretty good option, doesn't mean you will like it any more than what you already have though
Can you give a general idea what a taller dome needs in a waveguide? I'm just curious as I've not used tall domes this way since I tend to like metal domes and I suppose fabric domes tend to be the taller ones.
Wide and shallow not using a circular radius is the best I can offer as a starting point, the T34A one which works the best is +/-70 degrees and 16mm deep. When I first tried with a circular radius I couldn't make it deeper than 6mm before it started to get funky. The combination of dome height/width and surround height/width changes the specifics and sometimes like in the T25A the combination presents an issue that is hard to resolve.
Fabric domes can be a pain becuause BEM simulation isn't going to be accurate when the parts of the dome start to separate out and become non psitonic.
Fabric domes can be a pain becuause BEM simulation isn't going to be accurate when the parts of the dome start to separate out and become non psitonic.
Purifi has some simulations in their latest blog post which illustrates the point re tall hard domes
https://purifi-audio.com/blog/tech-notes-1/the-purifi-tweeter-project-part-1-15
Quote: "Consequently, a tall hard dome is the best choice for the radiator."
https://purifi-audio.com/blog/tech-notes-1/the-purifi-tweeter-project-part-1-15
Quote: "Consequently, a tall hard dome is the best choice for the radiator."