Constant Directivity Cornerhorns

Wayne Parham

Active Member
There is a lot of interest in high-fidelity constant-directivity loudspeakers these days. I'm very happy about that because I think it's the right path for making the most satisfying home sound system. I've been building my hifi loudspeakers this way for over 30 years.

I wanted to "put a bug in the ear" of others of you that are as interested in this approach as I am. Don't stop at a matched-directivity two-way or a dipole. If you have a chance, also try a constant directivity cornerhorn. I've heard great dipole speakers and I've heard great horn/waveguide speakers but I must say that nothing even comes close to a set of constant directivity cornerhorns. The improvement is that stark.
The whole idea is pretty simple. The woofer is close enough to the walls that they don't cause any self-interference. If they're closer than 1/4λ, there isn't a reflection. It's more like a ground plane, all three surfaces the floor and both adjacent walls being acoustically close to the source. So the source radiates into eighth-space and you don't have any trouble with early or late side or rear reflections - there aren't any. The sound traveling along the walls arrives at the same time as the direct sound without reflection. The only reflections come from opposing walls.

Naturally, the midrange and tweeter cannot be this close to the walls. The acoustic scale makes it impractical at higher frequencies. So I think it is best the midrange and treble sources be horn/waveguides that provide constant 90° radiating angle to match the room corner wall angle. The midhorn needs to be large enough to provide pattern control, and it can be snuggled close enough into the corner that the walls can act as extensions at the low end. Up high, it needs to provide pattern control to keep the coverage angle within the walls. Same with the tweeter.

The thing with waveguide loudspeakers that pair a direct radiating midwoofer with a constant directivity horn is they usually only provides constant directivity in the top decade, about 1/3rd of the audio band. This is the most important region to provide constant directivity, in my opinion, because it's where all the detail is. But the next decade below that is where all the body of the music is, the vocals, instrument fundamentals, most everything, actually. This is where the constant directivity cornerhorn rules.

Not every room has the right corners to be able to take advantage of this setup. So not everyone can use constant directivity cornerhorns. But if you have the right corners, nothing beats this setup, in my opinion. A properly designed constant directivity cornerhorn system provides constant directivity all the way down to the Schroeder frequency, where multiple subs can be used to provide uniform room response. You can actually achieve constant coverage of the entire audio band throughout the room this way.
 
I like the idea, Wayne, and have the room for it. Well, I have good corners anyway ;)
 
Your paper made for some good reading Wayne. I need to reread tomorrow but thanks for the info. Unfortunately my pesky gas fireplace is stuck in the prime corner of the largest room in my house. The next biggest room is 16' by 19' at the widest but with an 10' enclave on one wall. Wonder what size is optimal for CD cornerhorns.
 
Wayne
Can you tell us what constitutes "the right corners" for this set up.
Thanks Borus
 
Cool stuff Wayne. Would love to hear the 7 Pi's.

Yep RC you should cobble a pair.
 
Can you tell us what constitutes "the right corners" for this set up.

Basically it means at least 6 feet of unobstructed wall from the apex and width from corner to corner that isn't too far apart or too narrow. The axes must cross in front of the listeners for best results.
I also find that framed drywall rooms seem to work best. Rooms with very rigid walls like brick, concrete or stucco aren't damped well enough. That's more a modal problem, actually, something that panel traps and multisubs help.
 
I'm curious...

..if there are replacements for the stock K-horn horns that would take advantage of this principle.....:scratch2:
 
You could use the Khorn with a number of constant directivity horns/waveguides. I think you'd need something that could crossover 400-500hz range. A 2" compression driver with a large enough 90x40 or 90x50-ish CD horn should work. YOu might need a super tweeter to cover the last octave. If you are looking for something to drop into the stock horn horn high freq section, you might not have much luck.
 
You could use the Khorn with a number of constant directivity horns/waveguides. I think you'd need something that could crossover 400-500hz range. A 2" compression driver with a large enough 90x40 or 90x50-ish CD horn should work. YOu might need a super tweeter to cover the last octave. If you are looking for something to drop into the stock horn horn high freq section, you might not have much luck.

Hmmm....Yeah I believe it's Cutthroat who has the bass portion of a K-Horn topped with an Altec Multicell.

I have the stuff lying around to do that, but I was hoping to keep the looks of the K-horn intact....:nono:
 
Analog, are you looking for something that will drop in and be factory stock for dimensions, you can't beat Al's setup...
DSCN1749.jpg


He provides the grill facade and you can lurk for a set of Martenelli horns on the Klipsch forum, or pick up the 2" lenses that are becoming the rage, and grab your own drivers. They end up looking quite special. I just don't have the heart to tear up my perfect 1963, so the new modded one sits directly on top.:yes:
 
I've downloaded and printed the whitepaper but have not read it yet. Many thanks :thmbsp:

Are there any practical size limits to how small a corner horn can be?
 
I've downloaded and printed the whitepaper but have not read it yet. Many thanks :thmbsp:

Are there any practical size limits to how small a corner horn can be?

I'm certainly no expert on horns, but I think that you can make them as small as you wish, but generally, the smaller they are, the higher the cut-off frequency. Deep bass horns can and must be huge, it's only physics.

Best Regards,
TerryO
 
The Klipschorn bass bin won't work because the path length is too long. I suppose you could delay the tops but I think it would still be tricky to get CD from this setup.

A single driver won't work as a constant directivity cornerhorn because the pattern of a direct radiator collapses as frequency goes up. It would be uniform above the Schroeder frequency up to some point where the driver was acoustically distant (i.e. over 1/4λ away) from the walls. At that point, it will have a series of self-interference notches in response. Then as frequency rises higher, the directivity will begin to collapse.
 
The wall becomes the wall of the horn. So yes, it is an AC outlet on the wall..

While the original concept of the DECware corner horn was attempting to use a full range driver, reality set in and he also implemented a horn similar to a smith horn, which you see on the top of the corner horn cabinet. My thinking would be to only use it from 90 Hz to 600 Hz. where a 2" CD would takeover.
 
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