Horn Speakers - Is it me or.......

[olegtern]

The third inverted horn looks like an odd transmission line to me,I haven't seen the insides though,it may well be a simple horn.

It's just a bass reflex box.

Sorry, that's already been discussed By the way, these speakers sound good. And can be a good reference for a DIY project.

 

[Sokel]

It's just a bass reflex box.

Sorry, that's already been discussed By the way, these speakers sound good. And can be a good reference for a DIY project.

I searched and asked around in Munich show this year but it seems they weren't there.
Friends say they are pretty decent.We'll see

 

[jeffaegrim]

The in your face sound demanding attention is likely related to much direct sound.

However, this can be changed with the use of phase grating diffusion. As always: There's a big difference between diffusers, so anything called "a diffuser" might not work well.

That’s the way I understand it, yes, appreciate the input. Not sure if it’s related, but looking at non-smoothed measurements of a CD horn vs some Harbeth speakers I had before in the same room, there is more „grass“ in the top end with the horn.

Re: diffusion - I know that it’s very hard to make generalisations without knowledge of the room / speakers, but what type of diffusor would be suitable to this application & are we talking about diffusion at first reflection points or diffusion closer to MLP? Just curious, I’ve come to enjoy the prevalence of direct sound.

Btw - just for continuity’s sake - there was a post I made above asking about modifications to the crossover of my JBL S3100 that were possibly made by the previous owner, and the funky in-room FR that they produced. The reader may please disregard these measurements entirely, as the crossover was, in fact, assembled incorrectly. It has since been fixed, and the speakers produce a much cleaner, curve. Thread to follow

 

[robh36062]

Imo the characteristic of a waveguide which warrants use of that specific term IS its approximately constant directivity over most of its bandwidth. In practice the directivity widens at the low end and narrows at the top end, so it's not perfect, but it's arguably quite useful.

Hello Duke

So out of curiosity how would you class the original devices developed by Db Keele at EV back in 1975? This was long before the term waveguide was coined. If you look through the attached paper the directivity was quite good! Then he moved on to JBL to develop the 2342, 2344 and 2360 family. Are these waveguides? Are these a stepping stone towards them?

Rob

 

[gnarly]

In the image below the Oblate Spheroid is the light purple curve, and the mouth round-over is not shown. The Conical, Oblate Spheroid, and Hughes (Peavy) profiles are constant-directivity types, and as you can see they have most of their curvature down near the throat.

My understanding is that the Oblate Spheroid curvature is the one which imposes the least disturbance to the wavefront for a given change in angle, so imo it's arguably the "optimum" for a constant-directivity application.

Nice post Duke, thx.
I've studied that graph and read a lot of horn theory many quite a bit.
The conicals I build (straight purple traces above) , are true constant directivity, but suffer from compression driver to throat transition, and mouth termination.
For the CD-to-throat matching, I've tried the Charlie Hughes throat adaptation. It works, but I don't think it makes enough of a measured or audible difference to fool with, vs a more relaxed bolt in on type fit.
Mouth termination matters more I think. There I've tried secondary horn flares attached to the primary conical ala Keele, and also secondary tractrix shaped flares ala the Klipsch K-402 horn. Both do a good job of smoothing out polar anomalies caused by the poor mouth termination. I've also tried Hughes 'felt around the mouth' approach, and different degrees of simple mouth round overs.

My understanding of OS waveguides appears to match yours. I think its elegant property is how it diffuses internal reflections and diffraction in the most benign way possible.
Someday I hope to use somebody's Mabat /ATH inspired horn (which I think follow along the OS goal path), and use as as the platform to build a synergy. Best of all worlds I think, with the only tradeoff being ports in the horn interfering with wavefronts. From my experience with simple conical MEHs, I feel certain that tradeoff is well worth it.

And beating my own dead horse here, imo "approximately constant beamwidth over most of its passband" [without the use of diffractive features or vanes] is THE defining property of a waveguide.

Yep, my dead horse too
Hey, I figure we can each have our differing viewpoint, and all is just fine.

Although @gnarly also said he has also seen very few CD horns, which surprises me. Whenever I browse a horn catalog, it is dominated by CD horns with their specified '80°H x 60°V' (or whatever) directivity objective. They're everywhere. For example, link.

"Constant directivity" has almost been renamed "so-called constant directivity" by many members of the speaker building press

If the horn or waveguide dimensions don't at least meet Keele's formula for lowest frequency specified, you smell bogus from the gitgo. (formula posted earlier)
Next thing to look at is does that lowest frequency cover the range of intended operation of the driver planned to go with it.
Last thing is to build a proto, and curse cause it doesn't hold pattern as low as hoped ...Lol

 

[Bjorn]

Re: diffusion - I know that it’s very hard to make generalisations without knowledge of the room / speakers, but what type of diffusor would be suitable to this application & are we talking about diffusion at first reflection points or diffusion closer to MLP? Just curious, I’ve come to enjoy the prevalence of direct sound.

Depends on the distance you have. Diffusion over a wider frequency area needs some distance. If you have enough width, diffusion of opposite side wall reflections will give the most pronounced effect.
The rear wall behind the listening position is also a great place for diffusion if there's enough distance.

The RPG Modffractal is the best I've tested. You need a diffuser that diffuses high enough in frequency. Most stop around 4-5 KHz and that's too low.

 

[Duke]

Hello Duke

So out of curiosity how would you class the original devices developed by Db Keele at EV back in 1975? This was long before the term waveguide was coined. If you look through the attached paper the directivity was quite good! Then he moved on to JBL to develop the 2342, 2344 and 2360 family. Are these waveguides? Are these a stepping stone towards them?

Rob

I did not read the paper. At first glance it looks to me like he is joining together different horn shapes in order to get the radiation pattern shape he wants in both planes.

I would probably call them constant-beamwidth or constant-directivity horns.

Where the change in the angle of the walls happens reflections will occur, same thing at the fairly abrupt mouth terminations. Some of the reflection energy will propagate back down the horn all the way to the diaphragm and reflect back out again, partially ping-ponging back and forth and decaying as it does so. Imo this is a source of "horn honk".

And I can see how these horns could conceptually be stepping-stones towards modern waveguides, though I do not know what role they may have played in Earl Geddes' thinking on the subject. Earl was using JBL 4430 studio monitors (a landmark design itself imo) when I first met him, and he told me that for about ten years he had been wanting to build the speaker that became the Summa.

I think the day will come when the Summa is appreciated as being a point of inflection in loudspeaker design.

 

[jeffaegrim]

Depends on the distance you have. Diffusion over a wider frequency area needs some distance. If you have enough width, diffusion of opposite side wall reflections will give the most pronounced effect.
The rear wall behind the listening position is also a great place for diffusion if there's enough distance.

The RPG Modffractal is the best I've tested. You need a diffuser that diffuses high enough in frequency. Most stop around 4-5 KHz and that's too low.

Thank you - I might give that a try one day. Distances might be a problem, though, what with everything being set up in an apartment and all. 2.5m space behind the MLP at best

 

[Duke]

The conicals I build (straight purple traces above) , are true constant directivity, but suffer from compression driver to throat transition, and mouth termination.
For the CD-to-throat matching, I've tried the Charlie Hughes throat adaptation. It works, but I don't think it makes enough of a measured or audible difference to fool with, vs a more relaxed bolt in on type fit.
Mouth termination matters more I think. There I've tried secondary horn flares attached to the primary conical ala Keele, and also secondary tractrix shaped flares ala the Klipsch K-402 horn. Both do a good job of smoothing out polar anomalies caused by the poor mouth termination. I've also tried Hughes 'felt around the mouth' approach, and different degrees of simple mouth round overs.

I didn't realize you were designing and building and optimizing your own horns! That is indeed... what's the word I'm looking for... oh here we go: "gnarly". I tip my virtual hat to you!

Someday I hope to use somebody's Mabat /ATH inspired horn (which I think follow along the OS goal path), and use as as the platform to build a synergy. Best of all worlds I think, with the only tradeoff being ports in the horn interfering with wavefronts. From my experience with simple conical MEHs, I feel certain that tradeoff is well worth it.

That very seriously might be the ultimate! As I'm sure you know.

I have lately been using Marcel Batik's math with his permission, as his math optimally smooths the transition from the virtually-straight sidewall to the mouth round-over such that the rate of change in the curvature is very gentle, to minimize the mouth reflection.

The profile Marcel prefers is not quite an Oblate Spheroid, as (if I understand correctly) he's found a variation which optimizes for a bit better frequency response smoothness. I prefer ye olde Oblate Spheroid because it has the best match between the on-axis and off-axis curves, and I don't mind a bit more complexity in the crossover filtering. Last weekend I measured a 12", 70-degree-pattern Oblate Spheroid which used Marcel's math and it had the best match between the on-axis and off-axis curves of anything I have ever measured.

"Constant directivity" has almost been renamed "so-called constant directivity" by many members of the speaker building press

Yes I try to remember to use qualifiers because our beloved "constant directivity" waveguides are not quite so, but arguably close enough to be useful.

 

[gnarly]

That very seriously might be the ultimate! As I'm sure you know.

I have lately been using Marcel Batik's math with his permission, as his math optimally smooths the transition from the virtually-straight sidewall to the mouth round-over such that the rate of change in the curvature is very gentle, to minimize the mouth reflection.

The profile Marcel prefers is not quite an Oblate Spheroid, as (if I understand correctly) he's found a variation which optimizes for a bit better frequency response smoothness. I prefer ye olde Oblate Spheroid because it has the best match between the on-axis and off-axis curves, and I don't mind a bit more complexity in the crossover filtering. Last weekend I measured a 12", 70-degree-pattern Oblate Spheroid which used Marcel's math and it had the best match between the on-axis and off-axis curves of anything I have ever measured.

Awesome Duke ! it's great to hear you are employing Marcel's work.
Do you have a 3D printer? I don't have one, but may get one soon, especially since I can't get good Baltic (russian) birch anymore to make conicals.

 

[Newman]

...Someday I hope to use somebody's Mabat /ATH inspired horn (which I think follow along the OS goal path), and use as as the platform to build a synergy. Best of all worlds I think

...I have lately been using Marcel Batik's math with his permission, as his math optimally smooths the transition from the virtually-straight sidewall to the mouth round-over such that the rate of change in the curvature is very gentle, to minimize the mouth reflection.

...Awesome Duke ! it's great to hear you are employing Marcel's work.

I mentioned upthread that a commercial product is in the wind that brings together Marcel's and Earl's work.

You won't see any MEH tech in it though. Dr Geddes does not hold it in high regard, and very much does not see it as the 'best of all worlds'. Not for home audio.

cheers

 

[Duke]

Awesome Duke ! it's great to hear you are employing Marcel's work.

Earl recommended Marcel's work to me.

Do you have a 3D printer? I don't have one, but may get one soon, especially since I can't get good Baltic (russian) birch anymore to make conicals.

No, I was involved in the design phase, and I'm doing the crossover so I made the measurements. The CAD work was done by someone with expertise in multiple areas, he also oversaw the manufacturing of the waveguide and did the final assembly of the parts. The 3D print was done in powdered carbon fiber using a process called "laser sintering".

I can put you in touch with him if you'd like, but just so you know, this was not an inexpensive project.

 

[gnarly]

No, I was involved in the design phase, and I'm doing the crossover so I made the measurements. The CAD work was done by someone with expertise in multiple areas, he also oversaw the manufacturing of the waveguide and did the final assembly of the parts. The 3D print was done in powdered carbon fiber using a process called "laser sintering".

I can put you in touch with him if you'd like, but just so you know, this was not an inexpensive project.

Thanks for that kind offer.

I'm pretty sure if I go the printed horn route that I'll want to get a printer and wade in to it in DIY fashion. I truly enjoy every step in the DIY process ... the design, building protos (over and over haha), measuring, and implement processing/xovers etc.
Building the final proto version for stereo or LCR, often feels anticlimactic, and seems more like work.

You won't see any MEH tech in it though. Dr Geddes does not hold it in high regard, and very much does not see it as the 'best of all worlds'. Not for home audio.

That's a pity. I'd love to see his audio intellect help refine the synergy concept into a better horn/waveguide than conical.. (Perhaps though, since commercial interests might be in play with anything he works on, patent infringement could be a show stopper from the gitgo...wild guess.)

Doesn't really matter though, as too many people have heard synergy designs, be they Danley's commercial boxes, or DIY one-offs. There's an ever increasing crowd that realizes MEHs are not just the province of PA, but may in fact be the best full-range co-axial implementation currently known.
A lot of really smart folks are trying to use advanced waveguides for MEHs........for home use Folks who have already mastered good designs similar to the Summa etc..

Personally, I think MEHs need to be big to reap their main benefit...full-range integration that extends lowest frequency of pattern control.
So far all the "advanced waveguides used for MEHS" designs I've seen have been relatively small. I figure due to 3D printer size constraints and costs of large prints.
I'm not so sure this has any advantage over a well done co-axial like from KEF, or good waveguide-over-cone builds like from Genelec, Neumann, Geddes, etc.
I think every driver section above the subwoofer handoff needs to be incorporated into a MEH for best of all worlds results.

Anyway that's just me,.... my thoughts / speaker preference ....which means no more than Geddes, or yours, or any other person's does.......
.......or the even general population's mean preference (ala Harman).....