|
Speaker Asylum General speaker questions for audio and home theater. |
|
|
|
Speaker Asylum General speaker questions for audio and home theater. |
|
In Reply to: RE: Baffle refraction posted by A.Wayne on May 14, 2015 at 16:17:10:
What you see is a gap between the front baffle and the side walls. In all the Harbeth models I've seen in person, the side wall edges are flush with the front baffle, not raised. I'm not sure why the gap is there, other than to serve as a mount for the grille.
Anyway, the shape of the baffle edge only makes a difference at frequencies where the size of the geometrical features are a significant fraction of the wavelength. My guesstimate would be ~1/4 wavelength. The gap on Harbeth speakers looks to be around 1/4" or 0.6cm, so the presence of the gap shouldn't really have much effect below 10KHz. And even then, the presence of the gap is just going to change the pattern of ripples not their magnitude. Also, the tweeter's radiation pattern is somewhat directional at those frequencies, so the level of diffracted sound is already well below the direct output. I suspect it's sonically invisible.
In order to achieve a meaningful reduction in diffraction effects by rounding the edges, the edge radius has to be pretty large. Large enough to make wood and MDF enclosures impractical, and certainly impossible if you're following the BBC design philosophy of lossy cabinet walls decoupled from the baffle. A compromise for MDF construction is flat beveled edges like Joseph Audio uses. Note the bevel depth is quite significant; it needs to be in order to make a difference. IMHO all the DIY speaker builders who are using a router bit to put a 1/2" radius on the baffle are just wasting their time. If these guys really wanted or needed to suppress edge diffraction in their designs they would use felt.
Another thing to consider is that it might be better to factor diffraction effects into your design than try to suppress them entirely. A rectangular baffle with square edges is easy to model and there are spreadsheet calculators available. You can adjust the baffle dimensions and tweeter placement until the response is optimized, or maybe even use diffraction to help compensate for the tweeter's response. Designing for a complex curved or beveled shape requires CAD software and something like finite difference time domain or finite element frequency domain simulations. Without that you're just taking shots in the dark.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- They aren't raised edges, and I don't think it makes much of a difference anyway - Dave_K 06:36:41 05/15/15 (2)
- RE: They aren't raised edges, and I don't think it makes much of a difference anyway - A.Wayne 07:34:16 05/15/15 (1)
- The BBC LS3/5A design had raised edges - Dave_K 10:17:19 05/15/15 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
