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Old 18th September 2011, 02:46 PM   #991
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That may or may not be true. I don't think early reflections are good, but it's not just the clarity thing. There are big problems just in terms of amplitude response from early reflections in some frequency bands. If the delay of the reflection is close to the half period of the waveform, it makes roller coaster response. It's very noticeable when compared with another speaker that doesn't do this, night and day.

When you have a dip at 120Hz caused by self-interference from the wall behind the speakers or floor bounce or a room mode, it messes up vocals and instruments like piano, guitar and trombone. Some sound too thin, others sound throaty. It depends on where the null is in relation to the peaks surrounding it.

This notch isn't always a sharp thin notch, either. I suspect if that were the case, it would be maybe a little less audible. Sometimes it's wide, like half an octave. Even if thinner, when it makes a 15dB notch that spans two notes, then you can really hear it as singers, piano keys or whatever progress through the range.

The thing is, so many people have never compared two similar speakers, one set up as a constant directivity cornerhorn, another in a more traditional cabinet. So it is easy to get used to the sound of the midrange ripple and not notice it. But your microphone will clearly show it. And if you take two speakers - one a constant directivity cornerhorn and another a traditional box pulled away from the walls a few feet - you'll definitely hear the difference, as plain as day.
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Old 18th September 2011, 02:59 PM   #992
Pano is offline Pano  United States
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Wayne I've tried several times to simulate this in the CARA room software and just can't see a big difference. But I'll keep trying!

If you can give me some typical box dimensions and frequency ranges to look at, I might have more luck finding it. Also: Would it have to be a horn loaded cabinet, or would the effect be similar on a direct radiator placed on a corner baffle?
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Old 18th September 2011, 03:10 PM   #993
graaf is offline graaf  Poland
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hey Pano!
What is the ideal directivity pattern for stereo speakers?
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Old 18th September 2011, 03:15 PM   #994
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Hmmmm?
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Old 18th September 2011, 06:12 PM   #995
gedlee is offline gedlee  United States
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Quote:
Originally Posted by Wayne Parham View Post
You can fit your waveguide into the corner as you see fit, blending its flare contour with the walls if you wish.
Which puts the driver outside the room - not very practical.
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Old 18th September 2011, 08:24 PM   #996
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So what does everyone experience when they lean to the side? Wintermute gets an image shift to the opposite side, I get a shift that stays on front of me.

Same side: 1
Opposite side: 1

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Old 18th September 2011, 09:34 PM   #997
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Quote:
Originally Posted by dantheman View Post
So what does everyone experience when they lean to the side? Wintermute gets an image shift to the opposite side, I get a shift that stays on front of me.

Same side: 1
Opposite side: 1

Dan
Without data on the speaker directivity, angular separation, toe in, and general room set-up, is such information of any use ? If the data can't be correlated to anything, then nothing will be learnt from it.
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Old 18th September 2011, 09:48 PM   #998
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I think everyone knows their speaker's pattern here and how to use a tape measure. I hope so anyway. Can't really discuss optimal patterns w/o some idea of that info. I'm surprised that in this group, the thought hasn't sparked any conversation especially since we are discussing ideals.

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Old 18th September 2011, 10:26 PM   #999
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My point was that you were asking just for what people hear when moving left and right without also asking for information on their speaker set-up to attempt to correlate it with something
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Old 18th September 2011, 10:51 PM   #1000
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Originally Posted by speaker dave View Post
Your scenario sounds good and I accept your math but you are being a little misleading regarding where this started from and what I said. When I suggested that nulls where the cause of the contrary shift in stereo image you said that it was more likely an overcompensation of the time intensity tradeoff.
Dave, I take your point, and I'm not attempting to be misleading. In fact when I did the numbers and it didn't come out as favourably as I expected them to, I still presented the results anyway instead of being disingenuous by letting the matter quietly drop.
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My mental math said that sound at about 1 foot per msec would take a 1 foot net distance shift for 2 msec. This is because the difference is double the lateral shift since you are getting closer to one unit and farther from the other. I realized there would be a vector slope factor so I upped the 1 ft to 1.5. Your math is more accurate. Sound travels a foot in .87 msec and the geometry of your 60 degree triangle cuts the shift by a factor of 2 (not the 1.5 I guessed). In the end the 1.5 feet (I did not say 1 foot) I mentioned would require a 13dB balancing shift, plus your 1 dB for drop due to distance. So we are at 14dB by proper calculation rather than 16 dB by my estimate!

Note that 14dB and the 1.5 ft lateral shift would be perfectly complimentary amounts. One would balance the other out and the image would not shift at all (in theory). Your contention was that we had overcompensated for the time intensity difference to the point where the image shift went in the wrong direction. How much level shift would that take? Would it take as much as twice the 16dB per 2 msec that maintains a stationary image? It would have to be significantly greater than 16 for 2 to cause the contralateral shift.

If your speakers fall off 7dB in 6 degrees then they will just balance out (not overcompensate). Thats a pretty steep slope. A speaker's polar might make it at some frequency. I wonder if it will be flat in response at that point in the polar curve?
I think expecting it to work over +/- 1.5 feet in horizontal location is expecting too much. Part of the reason I used 1 foot for the calculation was that +/- 1 foot lateral movement is about the widest I've experienced in practice where the phantom image stays roughly in the middle 25% without collapsing.

More might be possible with better directivity control, but my speakers are only horizontal CD (~90-100 degrees) above 4Khz, and have a significant pattern narrowing (and power response dip) at 3Khz, as the crossover frequency is too high to match the directivity of the full range driver with the ribbon tweeter as you normally would in a proper CD design. (I cross it over higher for other - to me - more important considerations than strict directivity matching)

Still, the sweet spot widening effect seems to work with crossing in front of the listener instead of crossing behind, it's just now that I've done these calculations its left me unsure as to exactly what's behind it, and I'm now thinking that straight intensity/time trading can't be the sole explanation, even if it does help somewhat.

Perhaps other factors are also at work, such as reduced ipsilateral wall reflections, and the extra pattern narrowing at 3Khz may be playing a role as well - a significant reduction in output in the presence region of the nearer going-further-off-axis speaker may have more effect on image location than full spectrum intensity/time trade-off would suggest. (I've found small errors in left-right balance in the presence region can have quite an effect on pulling the image to the louder side, more so than at many other frequency ranges)

In short, I'm not sure exactly what's happening.
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