This thread has the purpose to investigate non-constant directivity waveguide and horns.
I got interested since it is inevitable to avoid the transition from high directivity at high frequencies to omni-directional at low frequencies. I wish for this to happen over a large frequency range to avoid any abrupt change in directivity.
Much has been done on constant directivity waveguide and horns, so I thought to explore the opposite. Some has been done in this area too, but I'm curious to find out how it sounds like.
Take 1
A slightly modified Kugelwellen horn. It starts at 70 degrees and the overall all curvature is stretched to get a bit more in the wg and less back-fold. I did the calculations some 10 years ago (before kids, 3D-printing and the genius tool ATH was available).
Print is 30 cm wide.
Was also 10 years I did some measurements...need to freshen up...
I got interested since it is inevitable to avoid the transition from high directivity at high frequencies to omni-directional at low frequencies. I wish for this to happen over a large frequency range to avoid any abrupt change in directivity.
Much has been done on constant directivity waveguide and horns, so I thought to explore the opposite. Some has been done in this area too, but I'm curious to find out how it sounds like.
Take 1
A slightly modified Kugelwellen horn. It starts at 70 degrees and the overall all curvature is stretched to get a bit more in the wg and less back-fold. I did the calculations some 10 years ago (before kids, 3D-printing and the genius tool ATH was available).
Print is 30 cm wide.
Was also 10 years I did some measurements...need to freshen up...
Looks great - this will be interesting to follow. I'm myself aiming for a bigger version of my Hornflower with 6pcs of 5 inch woffers and a WG that houses/embraces it all... in concrete of course 🙂 Also, very interesting with some real world test using a high quality, rather flat, dome.... photos look fine.
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+1, I still have to understand how you make constant directivity from the low of the woofer til the treble when you have horn transition in between.
Ordinarily you start wide down low. It gets narrow towards the cross, then stays there for the tweeter.
Beaming IN the pass band so ? the WG helps to match the low end of the treble off axis with the off axis of the mid unit its beaming does in its high end ?
I never really understood this as I often seen the datasheet of the tweeters being flat above 1000 hz to 2000 hz till 60° off axis before beaming. The WG are also chose for having a lower crossover than the usual >2K hz cut-off. And below the 2K hz it is flat most of the time for a tweeter but the littliest domes.
Will follow the thread as I am lost. Thanks.
Edit : beaming IN the passband, so. Up to the designer to make the passband beam where it is psyacousticaly nice, aka BBC deep ?
I never really understood this as I often seen the datasheet of the tweeters being flat above 1000 hz to 2000 hz till 60° off axis before beaming. The WG are also chose for having a lower crossover than the usual >2K hz cut-off. And below the 2K hz it is flat most of the time for a tweeter but the littliest domes.
Will follow the thread as I am lost. Thanks.
Edit : beaming IN the passband, so. Up to the designer to make the passband beam where it is psyacousticaly nice, aka BBC deep ?
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good looking stuff.
Very reflection (diffraction) free.
I can see it perhaps adding a little boost below 3khz, and as long as it is flattened out, that means less distortion there.
And a huge plus for waveguide is better integration for phase alignment for the crossover, regardless of the slope.
So, you can get the deepest null when you check the "reverse the phase and see how low you dip at frequency point" is.
Very reflection (diffraction) free.
I can see it perhaps adding a little boost below 3khz, and as long as it is flattened out, that means less distortion there.
And a huge plus for waveguide is better integration for phase alignment for the crossover, regardless of the slope.
So, you can get the deepest null when you check the "reverse the phase and see how low you dip at frequency point" is.
That is the right question! I can't. Therefore I wish to increase the dispersion (decrease directivity) in the treble.
I plan to make it a MEH. So no beaming. This first is just a test print to see if I'm in the ballpark dispersion wise.
Thanks norman,
I think so too.
I guess the phase integration will be challenging since the dome does not provide as much tweeter delay as a compression driver.
Corner bass units (I'd look at the klipsch corner horn or double 15's) with a 90 degree CD MEH on top could be one solution ? Could even look into a non symmetrical horn to change the aiming if needed.
Rob
Rob
Hello All,
It starts out wide down low and gradually narrows as it goes up to the transition to next driver.
Often Constant directivity is a myth. CD often means and hopefully behaves as Controlled Directivity which continues to narrow much the same as the driver down low.
For example; see the gradual tapering of the FatailPro STH100 WG/Horn attached below.
Nothing new here.
"Therefore I wish to increase the dispersion (decrease directivity) in the treble."
Waveguides don't do that, but the opposite. They increase directivity typically below the frequency when the tweeter starts to beam (by it's diameter). As well all types of horns have narrower radiation than "open" drivers.
To achieve smooth and low directivity index (DI) best way is to make a multiway speaker with as small diameter drivers as possible. Crossovers must be set so that the lowpassed driver doesn't start beaming and finally the tweeter should be 19mm diameter version with flat plate! Some drivers have a "phase shield" to prevent beaming very high.
This kind of speakers are considered "old school" noways... And yes, they do sound different from high DI speakers in a room. For example Revel towers vs. JBL M2 or MEHs.
Waveguides don't do that, but the opposite. They increase directivity typically below the frequency when the tweeter starts to beam (by it's diameter). As well all types of horns have narrower radiation than "open" drivers.
To achieve smooth and low directivity index (DI) best way is to make a multiway speaker with as small diameter drivers as possible. Crossovers must be set so that the lowpassed driver doesn't start beaming and finally the tweeter should be 19mm diameter version with flat plate! Some drivers have a "phase shield" to prevent beaming very high.
This kind of speakers are considered "old school" noways... And yes, they do sound different from high DI speakers in a room. For example Revel towers vs. JBL M2 or MEHs.
Notice you have also a lot of in between loudspeaker with big WG for just the tweeter todays. I assume the difference with all those is the quantity of room reflexion time delayed that arrive at the ears ? Indeed treble beaming more makes that confortable fall in the end near Harmann curves something, but just in the highs I surmise in spite of beginning from the bass.
Many also try to be more in the direct field by putting the chair nearer from the speakers than the distance gap between L&R speakers, to put side walls reflexions (and flloor / ceilling) behind the sweet spot (so time delaying indirect sounds) : Joachim Gerhard listening area technic.
Many also try to be more in the direct field by putting the chair nearer from the speakers than the distance gap between L&R speakers, to put side walls reflexions (and flloor / ceilling) behind the sweet spot (so time delaying indirect sounds) : Joachim Gerhard listening area technic.
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You'll get the best result if you can design the speaker to work well with the room, and you sit back away from it by the normal amount. This is challenging to do.
Yes, but that horn is not CD, it has a tractrix curvature. Or an I missing something?
Sorry, I forgot to mention "in relation to constant directivity waveguides". A CD wg should have constant directivity, and if so, the dispersion in the lower treble is small compared to what I'm trying to do. I wish to have a smooth transition from something like +-35 degrees at 10-20 kHz to +-180 degrees as low as possible. Final speaker might be 90-120 cm in diameter.
So controlled beaming is what I aim for sort of speak...
OK Peter, now I understand!
I find it very useful to study Klippel NFS measurements and analyses by Erin and Amir. Pay attention to speaker construction and crossover points to see common traits of how to achieve the result.
Typically DI and "radiation angle" is defined by -6dB level. But that is very insufficient info - IMO we must go way beyond -6dB and way beyond 90deg off-axis horizontally, and also study vertical dispersion.
https://www.erinsaudiocorner.com/loudspeakers/
https://www.audiosciencereview.com/forum/index.php?pages/Reviews/
I find it very useful to study Klippel NFS measurements and analyses by Erin and Amir. Pay attention to speaker construction and crossover points to see common traits of how to achieve the result.
Typically DI and "radiation angle" is defined by -6dB level. But that is very insufficient info - IMO we must go way beyond -6dB and way beyond 90deg off-axis horizontally, and also study vertical dispersion.
https://www.erinsaudiocorner.com/loudspeakers/
https://www.audiosciencereview.com/forum/index.php?pages/Reviews/
Yes you are missing something.
It is CD: as in Controlled Directivity, gradual and smooth narrowing as shown in the plot that I posted above. Call it a Tractrix curve if you like.
Ronnie, your 'fog horn' approach is similar to the 'diffuser trumpet' that Kevin Scott uses for the Living Voice Vox horn speakers.
Measurements and directivity aside, it will be very difficult or even impossible to match the acoustic signature of such a highly efficient system with direct-radiating woofers; the trumpet will stand out, especially at short distances.
Integration/homogeneity is the key to any decent sounding system.
The ceramic tweeter that Peter uses is also a 'tough nut to crack'.
A few weeks ago I listened to this classical/textbook 3-way system:
The Eton units: 27cm woofer, a 20cm midrange and a 28mm tweeter with ceramic - magnesium alloy dome. The woofer cones consist of a three-layered sandwich construction with aramid fibers and hexagonal internal structure.
While the speakers had potential, I still had the impression of listening to 3 individual drivers instead of a single system, The tweeter stood out in particularly negative way: the sound of earthware.
Measurements and directivity aside, it will be very difficult or even impossible to match the acoustic signature of such a highly efficient system with direct-radiating woofers; the trumpet will stand out, especially at short distances.
Integration/homogeneity is the key to any decent sounding system.
The ceramic tweeter that Peter uses is also a 'tough nut to crack'.
A few weeks ago I listened to this classical/textbook 3-way system:
The Eton units: 27cm woofer, a 20cm midrange and a 28mm tweeter with ceramic - magnesium alloy dome. The woofer cones consist of a three-layered sandwich construction with aramid fibers and hexagonal internal structure.
While the speakers had potential, I still had the impression of listening to 3 individual drivers instead of a single system, The tweeter stood out in particularly negative way: the sound of earthware.
Why don't you just cross to an exponential where directivity matches the lower driver at crossover?? That's old school.
Rob 🙂
Rob 🙂