Domes on Horns vs Compression Drivers on Horns

Just out of curiosity, what a numerical approach says (50 mm dome in an infiite baffle, 0-90 per 5):

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Something that I've toyed with, is taking the idea of a Unity horn and turning it inside out.

If you look at your sim of a convex cap, you can see that it's really well behaved. In a nutshell, as the wavelength of the frequencies become smaller than the radiator, they narrow in a well behaved way.

If I understand the theory right, we can control the beamwidth a *little* (not a lot) by changing the height of the spherical cap. Basically the flatter that the cap is, the narrower than the beamwidth will be when the wavelengths are shorter than the cap.

An externally hosted image should be here but it was not working when we last tested it.


I think that's one of the reasons that the Beolab 50 and the 90 use this strangely shaped array. By curving the baffle they're widening the beamwidth. (Of course, the use of three drivers instead of one also gives them the opportunity to vary the vertical beamwidth by shading the drivers, delaying the drivers, or both.)

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Picture a sphere, with four midrange in the sphere, and a tweeter at the apex.
 
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Hello there .
I been watching this thread from a long time , and appreciate you guys .
I’m Zingali Acoustics speakers maniac , as many people knows that their speakers are horn loaded and mainly equipped with CIARE and B&C compressions and woofers . I actually have few models in my collection starting from lowest range to mid range from their portfolio.
Few months ago i have noticed new version of my beloved booshelfs , asked dealer what is a difference between old and new , he said they change compresion driver 1” with 38mm voice coil and titanium diagram for custom horn loaded tweeter and this version is only custom made for UK market . So i bought ... Spec is exactly a same as my older one with compresion driver so it’s 1500hz 12db/oct . Results are just outstanding, maybe is not so revealing in hi end but got much more depth and better staging in highs , very very interesting application . Please have a look on pictures i have attached .
 
The tricky part about all of this is that what I'm hearing doesn't seem to show up in the measurements...I'm not aware of a way to measure those. (If someone figured out how to do that, LMK.)...
...frequency response tends to be "smoother," which means there are less squiggles, peaks, and dips, compared to compression drivers. According to Toole, this FR smoothness is very important.
Once upon a time in Speaker Builder magazine, some fellows wrote an article about cepstral analysis.* A takeaway from that and subsequent readings over the years leads to my hypothesis that resonances cause delayed releases of energy whose "sound" is the "horn honk" that many hate. Fewer resonances = less delayed energies = smoother response and better sound. I don't remember how to set up to get the cepstral plots...sigh I guess I should go dig in my garage through my publications boxes. Well OK probably this
Reflecting on Echoes and the Cepstrum
is a great starting place.

I believe horns are wonderful tools for loudspeaker engineers, and that by now we can design quite good ones-but often the industry does NOT, for reasons of either other priorities like dispersion, or ignorant copycatting of previous art, ignorant use of old formulas, or visual pandering to customer's aesthetic expectations.

I hope to find some good horns to try a unique design with giant horn on the front and woofers totally out of sight on the back The backwards facing loudspeaker "project"

*P. Newell and K. Holland, "Round the Horn", Speaker Builder, 8/94, pp 24-64.
if someone can access these I'd love to see them
3. K.R. Holland, "The Use of Cepstral Analysis in the Interpretation of Loudspeaker Frequency Response Measurements", Proceedings of the Institute of Acoustics, Vol. 15 Part 7, 1993, pp 65-71.
5. R.H. McEachern, "Hearing It Like It Is: Audio Signal Processing the Way the Ear Does It", DSP Applications, February 1994, pp 35-47. [Golden Gate Enterprises: phone (415) 969-6920]
 
Just out of curiosity, what a numerical approach says (50 mm dome in an infiite baffle, 0-90 per 5):
Thank you! Very interesting.
- The direction of sound is to the right? So the top dome is convex, and the bottom concave (like Focal etc)?
- Does the simulation assume the dome pulses as a dome? Or moves like a pistion?
Hmmm, tell me, can you also easily simulate radiation of say 12" BEHIND and enclosure?
 
Have any of you guys any formula for proper wave guide and horn loading.
What is the difference.
I did see German white papers on wave guide propagation in terms of massive distortion reduction which was promising.
I am not sure, as described above that ready made wave guides can be
applied to any tweeter. There has to be some correlation.
 
Question for you guys - on the idea of using domes with waveguides, would there be any significant difference between using a larger soft dome vs a larger ring radiator dome in a waveguide?

As I've seen people comment before of how a waveguide can widen the dispersion of a ring radiator - but I'm curious as the tip of the soft dome would, "decouple" acting like a ring radiator, while a ring radiator would have/could use a phase plug to even itself out?

Being that a lot of this thread has been discussing the use of smaller~3/4" dome tweeters, or larger soft domes - I'm wondering how a larger ring radiator could play into this



Thanks everyone in advance
 
Hello Patrick,
I have read this group and I am very interested in using the Tymphany NE19VT with its 3D printed adapter on a Synergy horn for home use with a rather limited maximum sound pressure and I wanted to know in your opinion what could be the minimum crossover frequency with a cut at 18db / oct. I can also go below the 1500Hz indicated above.
Thanks
Guglielmo
 
Question for you guys - on the idea of using domes with waveguides, would there be any significant difference between using a larger soft dome vs a larger ring radiator dome in a waveguide?

As I've seen people comment before of how a waveguide can widen the dispersion of a ring radiator - but I'm curious as the tip of the soft dome would, "decouple" acting like a ring radiator, while a ring radiator would have/could use a phase plug to even itself out?

Being that a lot of this thread has been discussing the use of smaller~3/4" dome tweeters, or larger soft domes - I'm wondering how a larger ring radiator could play into this



Thanks everyone in advance

It's a "chicken and the egg" problem:

1) a 3/4" dome is small enough that you generally won't see dips in it's response, if you put it on a waveguide

2) trying to get anything bigger to work on a waveguide is tricky UNLESS you use a very large coverage angle. If you look at the waveguides that @augerpro has published, they're wide enough so that a relatively large tweeter isn't an issue

3) a ring radiator with a diameter of 25mm can work fine on a waveguide of almost any angle, but the drawback is that it only has as much displacement as a 3/4" dome (because a donut has less surface area than a circle.)

So it's tricky.

I like the 3/4" domes, but nearly all the good ones are gone now. The NE19VT was a great one, and it's unobtanium now.
 
At the moment the alternatives I know of are NE19VTS and Vifa XT25. To be able to match a 3.5 inch midrange / woofer I would have to go around 1200 / 1300Hz to have enough space on a Synergy horn.
I'm trying to simulate a two way "mini" Synergy with a dome tweeter and two Peerless SLS-85 that go down to about 100Hz.
You would prefer a NE19VTS or a Vifa XT25?
 
Hello Patrick,
I have read this group and I am very interested in using the Tymphany NE19VT with its 3D printed adapter on a Synergy horn for home use with a rather limited maximum sound pressure and I wanted to know in your opinion what could be the minimum crossover frequency with a cut at 18db / oct. I can also go below the 1500Hz indicated above.
Thanks
Guglielmo

Depends on how loud you want to play.

A 3/4" tweeter can produce a maximum of 101dB at 1500Hz assuming no power compression : http://www.baudline.com/erik/bass/xmaxer.html

If you stick it on a horn that's sufficiently large, you can probably get that number up to about 107dB or so.

THX minimums require 105dB.

In a nutshell, if you want to play reasonably loud, you're probably looking at a 3rd order highpass at around 1800Hz or so.

Check out "Crossovers: a step further" by LeCleach. There are some crossover topologies where you can include a gap between the crossover points. Basically set the lowpass on the midbass at 1500Hz and the highpass at 1800Hz.
 
I believe that the NE19VTS satisfies my needs also in consideration of my listening at home and that with the SLS85 it will not sound at stadium level. I just wanted to know if in your opinion, the 3D tweeter adapter should be considered as part of the "driver" or as part of the horn when calculating the distances the position of the Synergy's midrange port? For the tests I will start with a Minidsp. The gap between the crossover points is an interesting idea that I will study.
 
NE19VTS isn't available any longer

Distance from the midrange taps to the tweeter in a Unity horn should be measured from the tap to the diaphragm of the tweeter

Note that you can delay the output of the midrange by quite a bit, via the use of an acoustical lowpass, and electrical low pass, or both

One of the challenges with the Lambda Unity Horn from about 22 years ago was that they offered it with a variety of compression drivers, and some of them had a very long throat, causing issues:

061397c880fad210122886d4974b0dc27c8f2b32_2_447x500.jpeg
 
The long explanation is in the LeCleach paper named "Crossovers: A Step Further."

The short explanation is that each "order" in a low pass filter delays the output by about 90 degrees at the xover point.

In other words:

1) If you have a woofer and a tweeter on a flat baffle, in order for them to be in-phase, the highpass and the lowpass filter need to be first order. (90 degrees)

2) If you have a woofer with a 3rd order low pass at 1500Hz (like a Unity horn) the output from the midrange is delayed by 270 degrees at the xover point. 1500Hz is nine inches long, and a delay of 270 degrees works out to about 6.75" at the xover point.

The woofer taps in an SH-50 are 3.5" from the throat of the horn. But some of that additional length is the distance from the throat of the compression driver to the diaphragm of the tweeter.

Basically, you have to be careful about making the xover point too high, or you won't be able to get the tweeter close enough to the midrange. And compression drivers with long throats probably aren't optimum for a Unity horn. It's been a long time, but IIRC, the idea of using a TAD compression driver with a Unity horn was the idea of Lambda Physics, not Tom Danley. The original Lambda Unity Horn used a B&C DE25 - the same compression driver that was used in the Sound Physics Labs TD-1 Unity Horn. (Get it? "Tom Danley Unity Horn #1")