My horns are 385Hz T=1.4 that I designed to match the flair rate I measured through the JBL driver's phase plug. See http://jhsaudio.com/JBL4way.html
Horns frequently require significant EQ to get them to work right. Just an fyi that you'll probably need to do more than just apply a textbook crossover.
From little I know of horn design (zip?) and performance, I could say a horn would directivity at least this constant from ~ 550Hz on up. https://www.diyaudio.com/community/attachments/1726661699779-png.1357794/
Let me put that another way. If directivity is your priority, have you considered looking at waveguides?
Constant directivity, its sonic importance as described and appreciated by Pierre Qui Roule, Camplo, John Sheerin and Earl Geddes, is definitely on my short list of speaker performance perameters. However, being the resident ignoramus who can't even tell you the difference between a horn and a waveguide, I have no idea what any tradeoffs between them may exist. Not that I'm not curious about those differences, but even I could partake in an invitation to hear a great system using waveguides, there's little incentive as no one will build it for me.
Me?? Build that? Are you joking? Who do you think I am, John Sheerin, Pierre, Pano, NicoB, profiguy, bappe, Weltersys, Superlian, mabat, Kevinkr, et al? Even if you would consent to have Athos use the CAD file for the CNC to cut a block milled pair, I've no idea if my builder would agree to finish my system that way, plus, as Marco said, my Radian745Be drivers wouldn't be a drop in fit. Maybe, if all of the performance documents were available for my builder to evaluate.
I also wish that complete measurements were available for NicoB's next gen TH4001. https://audiohorn.net/next-gen-bi-radial-horn/ , for as Kevin and Weltersys note horns like the A290 and TH4001 will be more suspectible to room reflections than JMLC or Troy Crowe's ES horns.
But I was also expecting a NYC audition of NicoB's horn. Given the great costs involved, I'm not comfortable proceeding with something without first hearing it.
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An example of one of many subjective EQ preferences dependent on listening angle for horns without constant directivity.
Of the four you mentioned, only Earl Geddes is using a horn that would be described as "constant directivity" over most of the frequency range it was designed for.
Since the terms "horn" and "waveguide" have been used interchangably for decades, one has to compare specific examples of them to compare tradeoffs.
Earl called his oblate spheroid (OS) horn a "waveguide" to differentiate it from prior horn's coordinate system.
Here is a 2009 quote from Earl:
"Just so we are all clear on the term "waveguide" here is how it came about.
In 1991 when I found a new and different way to analyze flared conduits, and that this new method predicted some fundamentally different contours, I realized that calling them "horns" was a misnomer since it was exactly "Websters Horn" equation that I discarded when I did my analysis. To be clear on this distinction I used the term "waveguide" to mean a device that is based on a seperable coordinate system. I was aware of the terms usage in RF as well as Bose usage for the "wave radio", but I did not feel that this prior usage would be a conflict with mine. Hence, you can see that the term does mean "seperable coordinate conduits" because that's what it was first used for."
Obviously, the specific distinction Earl made was never universally adopted, and since any type of horn can "guide waves" in some way, people will continue to call them "wave guides" regardless of their flare design.
Art
A waveguide doesn't have a "sound" of it's own when it is designed correctly, fits the application and is installed and voiced correctly.
You value managing room reflections, yet you're not ready to consider horn reflections (diffractions) together with their other properties. Logically, I fear we are not going to be able to change your mind.
Yes, a waveguide/horn dispatches primary energy provided by the driver on a range of frequencies.
Coverage is selected based mainly distance. Sometimes we reduce it slightly when sidewalls are too close, but typically in a regular room/saloon, a horizontal coverage of 90° by 60° is suitable with constant directivity up to at least 7/8 kHz (the sensitivity of the ears aka ISO 226:2003, audibility, and the amount of audio information in the signal explain this).
Since sidewalls significantly contribute to the reverberated field and at the so-called critical distance, we receive approximately 50% of the sound directly emitted by the speaker and 50% from reflections off the walls, constant horizontal directivity ensures that the energy is coherent across frequencies.
When a singer's voice increases in frequency, the sound should not become "tiny" due to the non-constant directivity's impact on sidewalls. Since sidewalls in regular rooms are not as close as the ceiling and floor, and our ears are placed horizontally, we generally try to adapt the vertical dispersion slightly as well.
This is one of the reasons we often see 90° by 60° dispersion patterns. In other applications like cinemas, nightclubs, or outdoors, the distribution of the audience can influence these considerations, but that's a different topic.
If your position in height varies, its interesting to be constant in vertical too but be careful to not put too far away the acoustic center of the woofer:
Since the horn's directivity control diminishes when the wavelength becomes significantly longer than the horn's height vertically or width horizontally, designing the horn to be vertically constant for a substantial portion of the midrange (let's say below 7 kHz) will result in a horn with a tall mouth, so it's a matter of choice.
In brief , if the horn/waveguide maintains constant horizontal directivity, it will create a wide and immersive soundstage without a horizontal sweet spot. If there are no irregularities in directivity, it will be highly faithful and coherent across the entire bandwidth. (Of course, room acoustics and implementation will also play a significant role here.).
If it's constant vertically in medium range you will also reduce vertical sweet spot.
Another point about energy, what is present off axis is no more present on-axis, energy is not created from nothing (first law of thermodynamics), so it's important to not "wast" it and sent it, at the frequency it need , where it needs only.
I've tried to closely correlate the technical aspects with their perceptual implications for the listener.
Of course, a horn should be without midrange narrowing or midrange beaming (caused by diffractions, as AllenB discussed)
Coverage is selected based mainly distance. Sometimes we reduce it slightly when sidewalls are too close, but typically in a regular room/saloon, a horizontal coverage of 90° by 60° is suitable with constant directivity up to at least 7/8 kHz (the sensitivity of the ears aka ISO 226:2003, audibility, and the amount of audio information in the signal explain this).
Since sidewalls significantly contribute to the reverberated field and at the so-called critical distance, we receive approximately 50% of the sound directly emitted by the speaker and 50% from reflections off the walls, constant horizontal directivity ensures that the energy is coherent across frequencies.
When a singer's voice increases in frequency, the sound should not become "tiny" due to the non-constant directivity's impact on sidewalls. Since sidewalls in regular rooms are not as close as the ceiling and floor, and our ears are placed horizontally, we generally try to adapt the vertical dispersion slightly as well.
This is one of the reasons we often see 90° by 60° dispersion patterns. In other applications like cinemas, nightclubs, or outdoors, the distribution of the audience can influence these considerations, but that's a different topic.
If your position in height varies, its interesting to be constant in vertical too but be careful to not put too far away the acoustic center of the woofer:
Since the horn's directivity control diminishes when the wavelength becomes significantly longer than the horn's height vertically or width horizontally, designing the horn to be vertically constant for a substantial portion of the midrange (let's say below 7 kHz) will result in a horn with a tall mouth, so it's a matter of choice.
In brief , if the horn/waveguide maintains constant horizontal directivity, it will create a wide and immersive soundstage without a horizontal sweet spot. If there are no irregularities in directivity, it will be highly faithful and coherent across the entire bandwidth. (Of course, room acoustics and implementation will also play a significant role here.).
If it's constant vertically in medium range you will also reduce vertical sweet spot.
Another point about energy, what is present off axis is no more present on-axis, energy is not created from nothing (first law of thermodynamics), so it's important to not "wast" it and sent it, at the frequency it need , where it needs only.
I've tried to closely correlate the technical aspects with their perceptual implications for the listener.
Of course, a horn should be without midrange narrowing or midrange beaming (caused by diffractions, as AllenB discussed)
Even though I've now handed off high tweeter duty to a pair of Faital HF10AK drivers in AH1100 horns, the Rosso 65CDN-T in the AH 425 is what I was running prior and still am up to 7Khz. I'm actually considering going back the the 2 way, it was so good. I'm thinking something was lost in adding the second horn, especially imaging. @oltos if you already own these horns and drivers, just set them up and have someone build you a pair of cheap boxes for your Altecs and be done with it, or at least use it as a starting place as someone else suggested. And you might want to consider a Sublime K231 active crossover, they're relatively simple and might cost less then a passive. These drivers are really well behaved in the AH425s and there are options for room correction filters that can sweeten the pot at the end of it (or just don't worry about it).
Cross them at 700-800, or get Troy to print you out his rear covers for the Rossos and go to 600 if you like. This will sound excellent and probably beat the hell out of most of the old school horn combos people pay way too much money for although I admit if I had the room I'd own a pair of VoTs just because they're so sexy and iconic.
Hell I might even be willing to make you the cabs for the 416s if you can wait a while.
Cross them at 700-800, or get Troy to print you out his rear covers for the Rossos and go to 600 if you like. This will sound excellent and probably beat the hell out of most of the old school horn combos people pay way too much money for although I admit if I had the room I'd own a pair of VoTs just because they're so sexy and iconic.
Hell I might even be willing to make you the cabs for the 416s if you can wait a while.
I remember both Pierre and Gary Dahl had failed to integrate Raal ribbon tweeters with the AH425 for consistent satisfaction. But while not the same midrange horn, see here how John added a tweeter; scroll towards the end. http://jhsaudio.com/JBL4way.html Would imaging thereby return this way, while still retaining the newly gained HF extension and air?
Please excuse my near-total ignorance; 7-8khz appeared twice above, in consecutive, informative posts. Surely high frequency response >8khz is essential for fidelity, therefore a hard requirement for any horn/waveguide/constant-directivity speakers?
Confused by the off-axis low standard....
Confused by the off-axis low standard....
They’re two different builds, first a single 15”, second 2-12” AR.
I apologize if it wasn’t more clear-with the added HF horn the system is crossed at 7k, if I remove it the active module for the high cross is also removed, allowing the Rosso 65CDN-T/AH425 to play free which it does very well up to 13,500hz when it rolls off pretty quickly.
Thanks for clarifying. One never know what people are doing ;-) ports plus passive - double is better ;-)
Btw, I like your work. The upper speaker has a mirror like surface and seems to be very even. Maybe a nice option for @Oltos if you offer to help him.
Beautiful work, Bryan. No doubt, if things were otherwise I'd gladly ship you the 416s. But Gary Dahl shared his plans for building the
sealed midwoofer cabinets, which I had Jim Salk clone back in 2015. Here's Gary's system at an audio club event, with the 416s atop his subs.
https://www.diyaudio.com/community/attachments/pnwas17-jpg.632591/
Love the black paint job Gary did on them later on. https://www.diyaudio.com/community/attachments/img_3796-jpeg.1193321/
And here's my 416s which Troy Crowe still has after testing them. https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed
Well heck you’re in great shape! Gary’s speakers were one of my inspirations for my current setup actually, they’re elegant and no doubt sound phenomenal especially with that big RAAL in the mix.
Jim Salk does beautiful work. My standmounts are bery similar to his Silks, a Jeff Bagby design with RAAL 70/20s up top. I love how RAALs perform, so natural and unforced.
Well then since you’ve got most of the parts already I’m doubling down on my recommendation to just grab an active and go for it!
You’ll need a few cables and another amp, but it’s still very straightforward all in all. I still have tubes on my horns but I got over my doubts about class D when a buddy surprised me with a class D he made so I threw it at the woofers and it’s a match made in heaven.
Jim Salk does beautiful work. My standmounts are bery similar to his Silks, a Jeff Bagby design with RAAL 70/20s up top. I love how RAALs perform, so natural and unforced.
Well then since you’ve got most of the parts already I’m doubling down on my recommendation to just grab an active and go for it!
You’ll need a few cables and another amp, but it’s still very straightforward all in all. I still have tubes on my horns but I got over my doubts about class D when a buddy surprised me with a class D he made so I threw it at the woofers and it’s a match made in heaven.