[richidoo]

What is the relationship between edge radius and wavelength (frequency), with regard to smoothing edge diffraction? I think Dr. Geddes mentioned somewhere that edge radius need not be larger than .25 * longest wavelength (lowest frequency.)

I know V. Dickason in Loudspeaker Cookbook says it doesn't really matter, but after hearing a couple spherical enclosures I am curious whether the larger radius edges may have some real benefits.

How low in frequency is diffraction even noticeable?
Thanks!
Rich

[planet10]

How low in frequency is diffraction even noticeable?

Edge diffraction has different properties as the frequency goes down. At high frequencies there is time delayed reradiation transitioning to baffle step loss at low frequencies. What is high or low frequency is a function of edge sharpness (round over) and baffle width. Even at the baffle step around over or champher size affects the ripple in the baffle step transition.



For some real world measures of how big to get how low: "Acoustic Diffraction: Does It Matter?" James Moriyasu (Feb 2003 aXp). Its been a long time since i read it, but what i took away was that the bigger the better and that a champher is almost as effective.

dave

[richidoo]

Perfect! Thanks a lot Dave. I'll look for the article.  Also good to know that chamfer can be that smooth. Sphere is hard to make...

[jimdgoulding]

What is the relationship between edge radius and wavelength (frequency), with regard to smoothing edge diffraction? I think Dr. Geddes mentioned somewhere that edge radius need not be larger than .25 * longest wavelength (lowest frequency.)

I know V. Dickason in Loudspeaker Cookbook says it doesn't really matter, but after hearing a couple spherical enclosures I am curious whether the larger radius edges may have some real benefits.

How low in frequency is diffraction even noticeable?
Thanks!
Rich

When the wavelengths are shorter than a cabinet is wide, diffraction effects are both noticable and measurable.  Yes, chamfered edges of one's cabinets in the neighborhood of a tweeter (shortest wavelengths) can matter is a positive way.

[AJinFLA]

What is the relationship between edge radius and wavelength (frequency), with regard to smoothing edge diffraction? I think Dr. Geddes mentioned somewhere that edge radius need not be larger than .25 * longest wavelength (lowest frequency.)

I know V. Dickason in Loudspeaker Cookbook says it doesn't really matter, but after hearing a couple spherical enclosures I am curious whether the larger radius edges may have some real benefits.

How low in frequency is diffraction even noticeable?
Thanks!
Rich

Hi Rich, here is an article you might be interested in with regards to diffraction, that is a bit more comprehensive than the simplified examples above:
http://www.linkwitzlab.com/diffraction.htm

regards,

AJ

btw, not sure if Linkwitz will be at RMAF, but his latest Orion is in RM400 iirc. I'm definitely planning to try to swing by to hear them.

[Æ]

Diffraction caused by the baffle and diffraction off the baffles edges are two somewhat different things. Here is a link to a good article. http://www.speakerdesign.net/understand.html

Jeff Bagby wrote a nice article on cabinet edge diffraction. I have it, but I don't currently know where  you can find it.

[richidoo]

Jeff Bagby wrote a nice article on cabinet edge diffraction. I have it, but I don't currently know where  you can find it.

https://www.box.com/shared/f2jt7sjokm

Thanks for the replies guys!

[Letitroll98]

Ha!  Possibly a nice way of reminding folks to use the search function before posting?     Valuable links regardless.