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Old 7th December 2012, 11:36 AM   #11
dewardh is offline dewardh  United States
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Quote:
Originally Posted by john k... View Post
NOT!
Oracular pronouncements can be amusing but are not particularly helpful . . . some explanation (and examples) of the testing that shows the "inferiority" of the Vifa driver might be more generally informative. Not asking for a full test suite like John Krutke does, or burst tests like SL often posts, but SOMETHING! more than CAPS and EXCLAMATION! . . .
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Old 7th December 2012, 11:47 AM   #12
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Originally Posted by dewardh View Post
Did you get any sense of "difference", or was it "lost in the noise"?
The difference is very small if any. You can (with a bit of optimism ) conclude that the lx521 style baffle has a slightly better polar response and that the smaller lx521 baffle has a higher dipole peak. But the difference is, as it should be at max 1KHz frequency, pretty small.

I suspect most if not all of the mysteries lie either in the tweeter section, which I have omitted because I plan to use Neo3s, or in the vertical response (of all drivers) which I have not yet measured.

I'll upload the measurements later and perhaps I'll manage to do some vertical measurements this weekend.

Regards

Edit:

I have some pictures with me I can share now, all measurements are @1, without dipole compensation and gated @12ms, driver is a scan speak discovery 22w:

Rectangular baffle of 286mm width:
Click the image to open in full size.

LX521 shape(ish) 331mm width:
Click the image to open in full size.

LX521 shape(ish) 315mm width:
Click the image to open in full size.

So basically the blooming at 600Hz is less pronounced and the increase in directivity near the dipole peak is less abrupt, but if you cross at 1Khz it shouldn't matter too much.

I'll post the specific dimensions of the baffles (angles and height) later.

Last edited by moep; 7th December 2012 at 12:06 PM.
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Old 7th December 2012, 12:34 PM   #13
dewardh is offline dewardh  United States
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Originally Posted by moep View Post
The difference is very small if any. You can (with a bit of optimism ) conclude that the lx521 style baffle has a slightly better polar response and that the smaller lx521 baffle has a higher dipole peak. But the difference is, as it should be at max 1KHz frequency, pretty small.
Thanks for the plots, and yes, the difference is . . . subtle. But there is at least a hint that "the shape" is doing something better than (or at least different from) the bland rectangle .

I'll be particularly interested to see if there are more notable differences on the vertical axis (where the baffle differences would appear to be greater).
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Old 7th December 2012, 12:48 PM   #14
Rudolf is offline Rudolf  Germany
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Originally Posted by dewardh View Post
. . . but he said that he observed interaction, and there was enough of it to make it worthwhile. I'm not going to co-locate the rear tweeter like that anyway, but still wonder about the overall effect of the "bigger" baffle.
If you increase the baffle size, you trade radiation pattern "quality" at the upper end of the pass band against load capacity at the lower end. This is true for the monopole tweeter case AND the dipole tweeter case. With the Orions SL always opted for improved load capacity. For the LK521 too?

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Old 7th December 2012, 12:56 PM   #15
dewardh is offline dewardh  United States
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With the Orions SL always opted for improved load capacity. For the LK521 too?
Yes, but with ORION that was because he was trying to get the most out of the drivers in a 3-way. Hard to imagine there being any load related problem with the LX521 tweeters crossed that high . . . it must have something to do with pattern control (or "cosmetics" ).
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Old 7th December 2012, 01:22 PM   #16
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Quote:
Originally Posted by dewardh View Post
Oracular pronouncements can be amusing but are not particularly helpful . . . some explanation (and examples) of the testing that shows the "inferiority" of the Vifa driver might be more generally informative. Not asking for a full test suite like John Krutke does, or burst tests like SL often posts, but SOMETHING! more than CAPS and EXCLAMATION! . . .
It was as useful as the quote I was responding to.

By the way, baffle size and shape has little to do with the response in the 6dB roll off region other than to set where the peak occurs. What it does have to do with is what happens in the frequency region around the peak and what happens as the driver directionality takes over.
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Old 7th December 2012, 01:34 PM   #17
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Originally Posted by dewardh View Post
... there is at least a hint that "the shape" is doing something better than (or at least different from) the bland rectangle .
I made the same conclusion, I can use the LX521 baffle shape and pretend that it's better than a simple rectangle .
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Old 7th December 2012, 02:00 PM   #18
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Guys, I wouldn't waste a lot of time over analyzing this. Deward already mentioned that the LX521 baffle was arrived at empirically. I.e. SL cut a baffle, tested it and it seemed to work. Maybe he cut one baffle, maybe 20. My experience is that it isn't that hard.

Look at the lowewr mid polars for my system. That withthe side panels and all. I don't see any 600 Hz blooming. Looks pretty good to above the 1k crossover point.

Click the image to open in full size.
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Old 7th December 2012, 02:02 PM   #19
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10f, 12M, tc9, all good, right?

I mean, there may be more variation in the midrange choice, than the baffle particulars..
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Old 7th December 2012, 02:03 PM   #20
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Originally Posted by dewardh View Post
Oracular pronouncements can be amusing but are not particularly helpful . . . some explanation (and examples) of the testing that shows the "inferiority" of the Vifa driver might be more generally informative. Not asking for a full test suite like John Krutke does, or burst tests like SL often posts, but SOMETHING! more than CAPS and EXCLAMATION! . . .
He was just doing his Borat impression
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