Tweeter diffraction control

[JohnMichael]

I have found that IMO adding diffraction control around most dome tweeters helps with imaging. I have used foam weather stripping and now adhesive felt dots to break up early reflections. Sure it might take away from the look of the speaker but the sonic improvements are worth it. I was wondering how many others use some form of diffraction control and what you use? Thanks

[pelly3s]

jbl used to use a foam ring on the LE-25s and 26s you can still get the rings and they dont look terrible either

[Dick Hertz]

The best method for diffraction control I've found is a flush-mounted driver, slightly offset from the center line of the cabinet, with a 3/4" or greater roundover on the adjacent edges. If it's an existing speaker system, then about all you can use is a felt ring. Madisound sells 'em. They work better than weather stripping because they absorb more high frequencies.

[kexodusc]

Flush mounting really is the way to go. Felt rings can really help out some speakers that aren't flush mounted.

Diffraction control is really tweeter specific. An aweful lot of tweeters when tested displayed no benefit at all to being flush mounted, having the edges rounded over etc. And there are some that are almost unlistenable without these considerations that sound fabulous with them. Some tweeters will actually sound worse flush mounted.

Little tweaks like these are great. Cheap, easy, and a lot of happiness for not a lot of effort. Congrats!

[Swerd]

The best method for diffraction control I've found is a flush-mounted driver, slightly offset from the center line of the cabinet, with a 3/4" or greater roundover on the adjacent edges. If it's an existing speaker system, then about all you can use is a felt ring. Madisound sells 'em. They work better than weather stripping because they absorb more high frequencies.I recently built some MB20s, where Dennis Murphy recommends the 3/4" roundover that you mention. I used the Parts Express 0.375 cubic foot finished cabinets. Those baffle edges are rounded over, I'm not sure what their radius is, but they are smaller than 3/4".


http://www.partsexpress.com/images/302-715m.jpg

Dennis Murphy was curious if these would work with his design, so I took them to his house, where he listened and measured. The bottom line is that the smaller roundover works fine and needs no tweek in the tweeter crossover. Dennis said he was always curious as to how small you can go with a roundover. For the Morel MDT-20 tweeter (and maybe for others too), we now know smaller than 3/4" is OK.

[Bengal]

Just testing...sorry.

[dlr]

I have found that IMO adding diffraction control around most dome tweeters helps with imaging. I have used foam weather stripping and now adhesive felt dots to break up early reflections. Sure it might take away from the look of the speaker but the sonic improvements are worth it. I was wondering how many others use some form of diffraction control and what you use? Thanks

I don't lurk here much, but I happened to see your post. I agree that diffraction control helps imaging. The answer to your question depends on several factors, since there can be several sources of diffraction. These can be the driver faceplate (if not flush mounted), the cabinet edges (most commonly considered), obtrustions on the baffle (non-flat baffles such as steps) and adjacent drivers. All have an impact, but the magnitude varies widely.

There are also several means of diffraction reduction, as have been mentioned as well. Flush-mounting and offsetting the tweeter are two that should be considered necessities in most cases (aesthetics of offset notwithstanding). Roundover is effective, buy IME not as effective as a full real-wool felt application. Any "felt" that is not largely real-wool will be marginally effective, if at all.

My testing of even very large roundovers (I've tried 3") is helpful, but less effective than an optimal felt application. Roundovers are a good second, IMO, as far as edge treatments are concerned.

I have a couple of sections at my web site on the subject of diffraction control and the current issue of audioXpress has an article of mine specifically on the topic, all with information on where and what to buy that has shown excellent empirical results.

If you're interested, my site is:

www.speakerdesign.net

dlr

[poneal]

It isn't easy getting published and I admire anyone who manages to do so. I have read most of your articles on your page and found them very informative. Some of it still above my head, but I'm slowly but surely crawling along. I really apprecaite your input over at the PE board and MAD boards too.

I have a question for you. Do you know where there are frequency response plots of all the different types of crossovers. I've used 4th order LR xovers extensively, but I shy away from the others because I just don't know how they are supposed to look graphically. As you can probably tell, I'm pretty graphically oriented. That and very logical-->programmer. Appreciate your time, Paul.

[dlr]

I have a question for you. Do you know where there are frequency response plots of all the different types of crossovers. I've used 4th order LR xovers extensively, but I shy away from the others because I just don't know how they are supposed to look graphically. As you can probably tell, I'm pretty graphically oriented. That and very logical-->programmer. Appreciate your time, Paul.
I suggest that you go to the Liberty Instruments web site and download the free version of Praxis. I think that you can use that to generate the curves the interest you. You can also now save those files to disk.

If it doesn't have what you want, use the FRC spreadsheet at the FRD consortium. You can create target curves, or you can use the Passive Crossover Designer for targets as well. These latter ones required Excel, however.

dlr