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Old 21st May 2013, 10:45 AM   #21
graaf is offline graaf  Poland
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Quote:
Originally Posted by Elias View Post
How is uniform different from constant ?
Call me stupid but I don't understand the difference either

Can anyone please define "uniform" vs "constant"?
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Old 21st May 2013, 10:47 AM   #22
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Quote:
Originally Posted by Wayne Parham View Post
That makes it somewhat pointless to optimize pattern control in a region that will be blended with an adjacent source anyway.
Of course it makes sense that the radiation pattern of each driver "matches" because drivers don't blend. Each source continues to radiate as a single source and both patterns are superimposed onto each other which results in interference. Two waves of sine bursts approaching from opposite directions will still look like sine bursts after they passed through another. The wave shape isn't altered.
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Old 21st May 2013, 10:49 AM   #23
graaf is offline graaf  Poland
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Quote:
Originally Posted by markus76 View Post
It's the same thing People simply don't use precise wording.

What kind of directivity is that ...?

Click the image to open in full size.
it's a FCUFS' directivity
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Old 21st May 2013, 12:08 PM   #24
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And it is all achievable with:

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Old 21st May 2013, 12:10 PM   #25
bwaslo is offline bwaslo  United States
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Hey, everyone, let's not start with the name calling again, there's been too much of that already and for no good reason. The OP presented a technical discussion of the relative merits of directivity control and why he likes a certain horn design (H290) rather than some others, no foul in that. No need to get religious about this stuff, it's just hifi.

Not that I necessarily agree with Wayne on all of what he said. I'd still maintain that a "5dB ripple" is really a +/-2.5dB ripple (semantics, perhaps, but 2.5dB response variation is way better than pretty much any real system, in-room). And that much ripple has to do with the baffle situation (lips overhanging, edge effects).

Some (Gedlee, QSC, SEOS) opt to avoid a sharp transition between horn and baffle which presents a diffraction source (waistbanding effect), even if mitigated by horn directivity. If the ripple in the case illustrated came from the SEOS horn being too short, why does it appear at higher frequencies above 2kHz? The horn isn't too short for 4kHz, certainly. Low frequencies don't affect high frequencies, though their responses might perhaps come from similar causes. Larger SEOS (and some go as high as 18" for 1" drivers) don't change in character from smaller ones.

As far as directivity being a "fad", as mentioned earlier in the thread, I strongly disagree. Just because a sound doesn't come directly from speaker to your ears doesn't mean it suddenly becomes inaudible -- if you turn a speaker away from you, you'll still hear it quite well, even up at the treble frequencies. Once released into the room, sounds will reflect around until dissipated, coming again and again at your ears. It can't be avoided (except outside maybe) but you can (1) attenuate it: control directivity so that off-axis is lower than on-axis and (2) make sure it's response doesn't stand out: make the stuff you send bouncing around the room have a similar response to the direct sound so it doesn't sound out of place and will be well-masked by the direct sound. IMO, nothing says "I'm a speaker!" like an off-axis high frequency peak signaling its point of origin.

An elephant in the room with the waveguides discussed above, though, is the vertical directivity response. There's pattern flip in all these asymmetric horns (though I think it's an ok tradeoff to get the drivers closer together) and there will be odd lobes firing up toward the ceiling and floor from driver interference. The floor might have some absorption from a rug (though not likely very effective at mid frequencies) but the ceiling is usually a virtual acoustic mirror giving at least one strong reflection. Having drivers close together helps limit the irregularities some, but not a lot. The only designs I know of that deal with that entirely are the Danley Synergies (and similar designs) and the big Tannoys.
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Old 21st May 2013, 12:26 PM   #26
graaf is offline graaf  Poland
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Quote:
Originally Posted by bwaslo View Post
An elephant in the room with the waveguides discussed above, though, is the vertical directivity response. There's pattern flip in all these asymmetric horns (though I think it's an ok tradeoff to get the drivers closer together) and there will be odd lobes firing up toward the ceiling and floor from driver interference. The floor might have some absorption from a rug (though not likely very effective at mid frequencies) but the ceiling is usually a virtual acoustic mirror giving at least one strong reflection. Having drivers close together helps limit the irregularities some, but not a lot. The only designs I know of that deal with that entirely are the Danley Synergies (and similar designs) and the big Tannoys.
a coincident FCUFS does it too, no "odd lobes firing up toward the ceiling and floor from driver interference"
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Old 21st May 2013, 01:02 PM   #27
Pallas is offline Pallas  Pakistan
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Quote:
Originally Posted by Wayne Parham View Post
It's not a crusade against anyone. This is a technical discussion. One that I would appreciate nobody derail into name calling, or turning it into something personal.
Well, I'm clearly not the only person who read what you actually wrote (as well as the graph labels) and drew that inference...

Quote:
Originally Posted by Wayne Parham View Post
Bearing all that in mind, what do you think of the idea that I've proposed? Do you think a home hifi waveguide should be optimized for smoothness or for pattern control?
Honestly, probably pattern control. The reason being that the pattern is determined by physics and geometry, but if the pattern is fairly uniform over a wide axis, then FR can be controlled with passive/active EQ.

Furthermore, I look at that SEOS graph and I see that a large bit of the variation is a broad peak at 4kHz or so. Assuming that carries through the pattern, basically just one parametric filter will knock that down all over.

Note: no dog in this hunt. I greatly admire what both of you are doing. And went in an entirely different direction (TAD/Pioneer 5" concentric for mids/highs up front in a 3-way + flanking sub setup, 5" KEF Uni-Q's for side and rear surrounds) for my own use. Though I am, admittedly, considering picking up a set of the new plastic SEOS15's, to use with 12" woofers.

Quote:
Originally Posted by Jay1111 View Post
1. On axis linearity
2. Distortion performance
3. Phase integration



4. Off axis Linearity

That's where I see uniform directivity falling on the order of importance. You can obviously have a great sounding speaker without it...
That is the opposite of my experience. Speakers with midband pattern discontinuities invariably sound wrong to me.

Quote:
Originally Posted by Jay1111 View Post
This is a simple generalization and doesn't apply to every situation, or speaker. A few db more energy greater then 45 degrees off axis between 2-4 khz does not magically take over the entire room when you are listening to the on axis sound of the speakers... This idea is just getting ridiculous
Only in the extreme nearfield is one listening to the "on axis sound of the speakers."
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Old 21st May 2013, 01:22 PM   #28
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Instead of "uniform " or "constant" , how about "increasingly" directive?
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Old 21st May 2013, 01:28 PM   #29
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Instead of "uniform " or "constant" , how about "increasingly" directive?
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Old 21st May 2013, 02:09 PM   #30
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Quote:
Originally Posted by bwaslo View Post
IMO, nothing says "I'm a speaker!" like an off-axis high frequency peak signaling its point of origin.
I'd think a "off-axis high frequency peak" would signal our brain "Me (reflection) is the real source and not that speaker".

The other day I was standing on a small airfield with a small plane making its way to the runway. Suddenly the sound of another plane grabbed my attention. When I turned my head there was the closed hangar. What I heard was a reflection bouncing off the hangar door.
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