Testing baffle edge treatments for tweeter diffraction.

[dkalsi]

Excellent - thank you soooooo much for posting. Any chance you can show the first set of graphs (I.e, angle 0,15,30,45,60), while including some off-set (e.g. 3db) between each baffle measurement? The difference would be lot easier to see. Thank you again Sent from my iPhone using Tapatalk

[dlr]

Even 30 degrees is surprisingly similar to all. I'm a bit surprised at 30 degrees+. I expected a lot more at least at 30 degrees. Given this, a set of 0/5/10/15 would be interesting, especially given that this is the range within which most listeners position themselves to be seated.

dlr

[wogg]

Been following this on the face place too... very nice work Dave!

IMO the big bevel is the winner, but I'm also surprised at how little difference there is in the off axis measurements. The bevel mostly helped on axis, and kept the off axis changes as smooth as possible. That would be a win for in room power response and likely imaging in the end.

[jhollander]

I think this is great. I had good results with asymmetric baffle treatments. Might be able to fill in and offset the tweeter for future tests

[skatz]

No comment about the Olson research I linked in #17 above? Cabinets J and L corresponding to figures 15 and 17 look very similar to what is being measured here.

[4thtry]

Thanks for the data. I examined and attempted to rank your 2nd set of curves (post 28) for "consistency" across measurement angles. I placed sheets of masking paper over the computer screen to block off unwanted freq bands so that I could clearly see the differences:
-------
1-2kHz
Not much difference
--------

2k - 5KHz

1) Big Bevel (best)
2) Tapering chamfer
3) 7/8" roundover
4) Square box (worst)
--------

5-7kHz

1) 7/8" roundover (best)
2) Tapering chamfer
3) Square Box
4) Big Bevel (worst)
--------

7-10kHz

1) Big Bevel (best)
2) Tapering Chamfer
3) 7/8" roundover
4) Square box (worst)
--------

10khz +
Not much difference

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Comments: There appears to be no clear winner. The square box is, however, the clear loser. The results seem consistent with Olson's original AES paper. The 7/8" roundover did not place well in some of my rankings, probably because it was not "spherical" enough. Thanks again for doing this test. Very good information. Bill

[dlr]

DaveFred, are you able to export the measurements to files? There are some ways to make more extensive comparisons.

dlr

[DaveFred]

DaveFred, are you able to export the measurements to files? There are some ways to make more extensive comparisons.

dlr

Do you have drop box? The data file is 36 megs, I am happy to send it to you.

[donradick]

DaveFred, are you able to export the measurements to files? There are some ways to make more extensive comparisons.

dlr

Very glad to see your participation. Love your analytic analysis...

[stephenmarklay]

This is really cool. Thank you. I have built a few square boxes but use felt around the tweater (like the LS3/5.) I wonder if that is effective at shielding the edges?

[dlr]

This is really cool. Thank you. I have built a few square boxes but use felt around the tweater (like the LS3/5.) I wonder if that is effective at shielding the edges?

As far as I know, felt for diffraction control was first used on the LS3/5A and yes, it is effective. To what degree with the amount they used, I don't know. Thicker and broader is usually better with a point of diminishing returns. It was especially helpful for the LS3/5A since the front baffle was actually recessed to allow for a front grill. However, I have no doubt that more than they used would have improved the response, but as a commercial product, reducing cost is always a top consideration.

dlr

[ergo]

Very interesting study DaveFred - Thank you for sharing.

I created a OneDrive link with write access.

https://1drv.ms/u/s!AvVPh3wl37Nzm4QuUa-opCKb7ktCxQ?e=YJUFZD

Would be cool if you could copy the REW files there. Will make it easier to select the type of interest for further study.

[stephenmarklay]

As far as I know, felt for diffraction control was first used on the LS3/5A and yes, it is effective. To what degree with the amount they used, I don't know. Thicker and broader is usually better with a point of diminishing returns. It was especially helpful for the LS3/5A since the front baffle was actually recessed to allow for a front grill. However, I have no doubt that more than they used would have improved the response, but as a commercial product, reducing cost is always a top consideration.

dlr

Thank you for the comments… I carried the felt over to my new soundbar. I am going to play with some different kind of boxes in the near future and I won’t ignore edge treatments.

[stephenmarklay]

As you're probably aware, having the dome equidistant from 3 sides should generate the strongest ripples. Even on a sq. cornered baffle, the effects would be minimized by having the distance to the edges all diff. amounts, like: 1.25" from the top, 2.5" from left edge, 3.75" from the right. I DO like the fact that 3 of your baffles are equidistant, as the effects from the roundovers and mitres should show strongly w/all 3 edge effects reinforcing each other.

Chris, is it possible to do this with established designs as long as the distance between the drivers is the same (as well as any offesets) without screwing anything up?

[Chris Roemer]

Most usually, the staggered distances to baffle edges will smooth out "on-axis" anomalies. A lot of designs where they're not staggered might not be that great on-axis, but will probably smooth out off-axis a bit.
So, if staggered - you can toe 'em "in" (toward your listening position), but if they'e not, they often should be pointed straight out (perpendicular to the wall behind).
If you want YOUR version to match the one you think you liked enough to build (from reviews), I'd NOT alter the placement of the drivers on the baffle.