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Old 3rd June 2013, 02:17 AM   #121
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From what I recall, the SEOS has less collapsing directivity--it has wider dispersion higher up?

If so, then the cornerhorn ... may be an good application.

Instead of gently collapsing directivity to match a regular boxed woofer high up, here I'd think you'd want the widest directivity that matches the wide woofer/wall system and the wide midhorn (augmented by the corner). Hmmmm ...

Both SEOS certainly are sweet looking, grrrrrrrow!

Cheers,
Jeff

Last edited by AudioLapDance; 3rd June 2013 at 02:34 AM.
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Old 3rd June 2013, 02:30 AM   #122
Jay1111 is offline Jay1111  United States
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SEOS 24 looks perfect for something like this

Click the image to open in full size.

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Old 3rd June 2013, 02:49 AM   #123
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Originally Posted by AudioLapDance View Post
From what I recall, the SEOS has less collapsing directivity--it has wider dispersion higher up?

If so, then the cornerhorn ... may be an good application.

Instead of gently collapsing directivity to match a regular boxed woofer high up, here I'd think you'd want the widest directivity that matches the wide woofer/wall system and the wide midhorn (augmented by the corner). Hmmmm ...

Both SEOS certainly are sweet looking, grrrrrrrow!

Cheers,
Jeff
Do any of the larger SEOS waveguides mate to larger diameter compression drivers? How low can it ultimately go with constant directivity?
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Old 3rd June 2013, 03:33 AM   #124
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Originally Posted by Robh3606 View Post
I remember the corner horn that was at the MWAF, the first or second one, many years ago. It was a 15 in a reflex box with a triangle spacer to nest it into the corner with a 10" and a horn on top??
Hi Rob, it has been a while, no doubt. I really liked that original Midwest Audiofest, put together by Mike Baker. I think many of us made some good friends there. I liked that show so much I borrowed the regional show concept for GPAF and LSAF in Tulsa and Dallas, respectively. Some years, I still give the same "Crossover Electronics 101" seminar I did at Baker's MAF too. Didn't do it this year, but we're planning to have seminars again next year.

I'm kind of surprised you aren't all over the constant directivity cornerhorn concept, to be honest. It made enough impression on our mutual friend Duke LeJeune that he makes a version of the constant directivity corner speaker himself, the Rhythm Prism. Some words from Duke after hearing the Pi constant directivity cornerhorn at that same MAF show:
I've always thought all of Duke's speakers sound great. He really has this waveguide loudspeaker paradigm down, in my opinion.

So anyway, I'd like to respond to your comments a little more candidly than I might others, 'cause you and I go way back. I've seen you around the same forums for at least a dozen years, so please forgive if I write with some familiarity. I'm gonna pretend we're sitting in that demo room back at MAF, and we're just chatting. And I guess others can see us talking, and join in if they want too.

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Originally Posted by Robh3606 View Post
I don't see any advantage over a conventional box system as far as control of room modes. There is no directivity control below the Schroeder frequency like in any other system. You are still going to have to address room modes from corner placement like any other system.
I agree, 100%. This design approach doesn't address room modes at all. You would mitigate those with multisubs, just like any other loudspeaker system. But you could implement a Welti multisub configuration just by putting two additional bass sound sources in the opposite two corners. Or you could do a Geddes multisub configuration, placing them somewhere else. Either way, the constant directivity cornerhorn configuration does nothing to address room modes.

- However -

It does prevent self-interference notches from nearest boundaries, because the sound source is essentially flush with the boundaries. The sound source is within 1/4λ well up into the midrange, so it prevents early reflections and eliminates the response anomalies from nearest boundaries. It does provide constant directivity from the Schroeder frequency upwards, and that's a pretty big deal.

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Originally Posted by Robh3606 View Post
We all know at low frequencies the radiation pattern for a system is for all intent and purposes omnidirectional.
Yes, and if you put it in a trihedral corner it becomes confined to this spherical section, giving 9dB DI over omnidirectional radiation. Whether in freespace, on a baffle or at the apex of a trihedral corner, radiation angle is constant at frequencies where the radiator is acoustically small, i.e. below ~500Hz for a 12" or 15" woofer.

So in my opinion, if the room has the right corners, this can be made useful.

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Originally Posted by Robh3606 View Post
That's my point if the walls and only the walls are controlling the directivity of the design at the lower frequencies then using that logic I can place any speaker in a corner and make the claim it is CD.
If the sound source is acoustically small and the distance to the apex of the corner is also acoustically small, then yes, the radiation angle is constant and it is set by the wall angle.
The biggest problem of taking "any old" speaker and putting it in a corner is that it probably is not going to be acoustically close to the corner except at bass frequencies, so midrange will suffer from early reflections and self-interference.

But you can design a speaker for that placement, and that's what I'm calling a constant directivity cornerhorn. When properly done, it does provide constant directivity. In a large room or outdoors, it remains constant through the entire audio band. In a small room, it obviously can only be constant above the Schroeder frequency, but as I said, I still find that to be immensely useful.

Let me try a reverse logic on you, and sorry if it sounds like a smart aleck, but I think it will illustrate the point pretty well. It is sort of a reversal of your last statement:

If a straight-walled horn flare and only the horn flare is controlling the directivity of a compression driver then using that logic I can place any compression driver on a straight-walled horn flare and make the claim it is CD.

As you can see, this is a true statement. So I think the arguments about how a constant directivity cornerhorn would act in an anechoic chamber are somewhat academic, because the loudspeaker isn't designed to be used in fresspace. As AudioLapDance said, that "breaks" the speaker. It would be like using a compression driver without the horn.

Of course, a constant directivity cornerhorn crossover is designed for this arrangement. It is designed with the understanding that there is DI from the corner, and there should be physical design aspects that keep things in phase and acoustically close, both to adjacent sound sources and to the apex of the corner.

To me, this design approach is not unlike soffit mounting of a baffled speaker. The benefits of a soffit mounted speaker where the baffle is flush with the wall are similar, in that there is no directivity shift from omni-to-halfspace, the so-called baffle step. One would want to design a soffit mounted speaker to take advantage of this fact too. But in the case of the constant directivity cornerhorn, we go one step better because we include not only the wall behind the speaker but what would have been the ipsilateral wall too. So this configuration removes reflections off either one.

There is only one disadvantage of the constant directivity cornerhorn configuration, and it is a biggie, to be honest. But it isn't an acoustic or even an academic disadvantage, it is purely one of convenience. Or rather of inconvenience. The problem is the configuration can only be employed in specific room layouts, and frankly, it is the rare room that has this advantage. So most people cannot make use of this configuration.

That's why I also adopted the DI-matched two-way, after seeing the JBL speakers made that way. Seemed like a very useful compromise to me. And this kind of brings me back to the subject of this thread, which is that even though a DI-matched two-way isn't constant directivity, it can be made to be pretty uniform. The beamwidth narrows as frequency rises to the crossover point, and then becomes constant. That's a pretty smooth sounding configuration to me. Especially when soffit mounted flush, or if stand mounted, done with flanking subs to smooth the self-interference notch from the nearest boundaries, like the wall behind the speakers.
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Last edited by Wayne Parham; 3rd June 2013 at 03:52 AM.
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Old 3rd June 2013, 03:42 AM   #125
Scaper is offline Scaper  United States
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Originally Posted by darrellh44 View Post
The Pi mid-horn is loaded with a 10" Eminence driver which means it can probably provide CD coverage to considerably lower frequencies.
I'm pretty sure they were going to use the BMS coaxial driver crossed around 400hz going all the way up from a single point source. The BMS distributor said that wouldn't be a problem. I'd have to double check, but I think he said he's run that BMS even lower. Of course, it's a very expensive CD.
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Old 3rd June 2013, 06:58 AM   #126
AllenB is offline AllenB  Australia
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Originally Posted by Wayne Parham View Post
the configuration can only be employed in specific room layouts, and frankly, it is the rare room that has this advantage.
What do you see is so rare about such a room...I mean, if you started with a blank wall and adjacent corners this seems possible to achieve.
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Old 3rd June 2013, 07:22 AM   #127
Omholt is offline Omholt  Norway
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I agree with you Wayne. A contant or uniform polar response is what matters most. Whether it should be wide or narrow depends on the situation and goal. Most horns have a collapsing polar that becomes narrower and narrower. Not only is that a problem for listeners off-axis, but it will also colour the sound in the sweetspot if the room is not treated with broadband absorption.

The only speaker besides a corner loaded horn that I know of that has a uniform response over a wide frequency area is Don Keele's CBT. Personally I leave omnis out, since I don't believe they work well in a bounded space.

Here's something I wrote in another thread about CBTs:
Quote:
The CBTs can offer both; A spacious soundfield where the reflected energy resembles the direct signal and hence little coloration. Or a more precise and sharp image with treatment if that's what you want. The listener gets to choose and both will work extremely well.
A typical waveguide/horn speaker can however not give the spacious soundfield without much coloration. If you leave the sidewalls reflective, you end up with some reflective energy at certain frequencies and nothing or less at others. In that case, broadband treatment is required for accuracy.

With the CBT the floor reflection is a benefit. It is coupled to the floor and the reflection contributes what is effectively the other half of the CBT. So it negates the need for a full arc. This is a great advantage. It effectively eliminates the need for floor treatment that is problematic at best. Especially as any floor treatment typically exhibits a such a high frequency profile as to not be effective as broadband absorption for a traditional speaker. A bare broadband reflective floor surface is optimal.

The vertical disperion of a full CBT arc is 45 degrees. Therefore I am thinking that when placed on the floor, that the upward tilt would be restricted to 1/2 that. Thus from the horizontal plane it would only be a 22.5 degree upward distribution. As such, this effectively eliminates early ceiling reflections until well behind the typical listening position and thus eliminates the need for ceiling treatment, unlike typical loudspeakers.

The CBT benefits from a near uniform 180 degree power response and a constrained vertical distribution. In both axes it avoids a collapsing polar power response, which so typical of other designs.
http://www.xlrtechs.com/dbkeele.com/...ck%20Large.png

And in all cases, the soundstage of the CBT offers an improvement over traditional speakers, as not only is the power response uniform over the horizontal plane, substantially increasing usable listening positions or eliminating many of the typical constraints that limit listening positons, and the limitations of a nearfield response due to destructive driver interaction (superposition) are effectively rendered moot.
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Old 3rd June 2013, 10:38 AM   #128
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Originally Posted by Scaper View Post
I'm pretty sure they were going to use the BMS coaxial driver crossed around 400hz going all the way up from a single point source. The BMS distributor said that wouldn't be a problem. I'd have to double check, but I think he said he's run that BMS even lower. Of course, it's a very expensive CD.
I was thinking of the smaller SEOS with the woofer/wall and midhorn: so from 1.6k up.

But the big one is interesting ... pushed back into the corner, it would extend the horn, provide lower loading and decrease crossover. Do you think it could make it to 200Hz?

Wayne's philosophy is a bit different. He has 'first order' filters on the the woof and midhorn so they cross more slowly and provide two sources at 200 Hz to minimize the floor bounce notch in the ~200Hz area.

Cheers,
Jeff
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Old 3rd June 2013, 10:44 AM   #129
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Originally Posted by AllenB View Post
What do you see is so rare about such a room...I mean, if you started with a blank wall and adjacent corners this seems possible to achieve.
WAF!!!


No, nothing too spooky: They work best when set up on the short wall and crossed a bit in front of the listening position. Plus you need ideally ~6ft of uninterrupted wall (x, y, z). So not unique or anything but it is a bit of stacked criteria.

I have a room in mind ...

PS Wayne, where are those cool 'animated wave interaction' .gifs you posted at your place? (Less wave interference as you get closer to the corner) A pic is worth 1000 words ...

Last edited by AudioLapDance; 3rd June 2013 at 10:47 AM.
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Old 3rd June 2013, 01:18 PM   #130
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Originally Posted by AudioLapDance View Post
Wayne, where are those cool 'animated wave interaction' .gifs you posted at your place? (Less wave interference as you get closer to the corner) A pic is worth 1000 words ...
They're in the link in my last post, from the Pi Speakers FAQ, and here:
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