How Do You Deal With Baffle Edge Diffraction?
@elizabeth, it may be of interest to you (if you don't already know) that Danny Richie is largely responsible (along with Brian Ding) for the design of the Rythmik/GR Research OB/Dipole Sub that mates so successfully with planar loudspeakers like your MG20.7's. He's a very knowledgeable and talented speaker, sub, and crossover designer. |
You’re correct Erik. I am referring to baffle edge diffraction. Both that and baffle step are important concepts. Good information all around. It’s my understanding that edge diffraction will cause the higher frequencies to “re-emit” from multiple points around the speaker which causes a number of issues. Perhaps worst of all, this “re-emittance” happens out-of-phase with the original sound wave created at the tweeter which really mucks up the sound. I believe this contributes to listener fatigue because the sound doesn’t quite make sense to the brain. (That’s my personal theory. Not sure if tests have been done to verify it.) |
Hey gang, Just FYI, the "baffle step" effect which @Elizabeth linked to is different than I think the OP meant to ask. Here Both are real. Baffle step has to do with how the baffle affects low frequencies of a speaker without rear wall reinforcement. It affects how quasi-anechoic measurements are done, and is related to "baffle step compensation" which is done in the crossover. Basically, speaker designers have to lower the woofer's efficiency to extend the bass low enough. Here is an example of a speaker deliberately lacking in BSC because it is designed for rear wall placement: https://www.stereophile.com/content/crystal-cable-arabesque-minissimo-diamond-loudspeaker-measuremen... See figure 6, and note the steep ramp up to 100 Hz. JA's failure to place the speaker as recommended, and failure to understand what he was looking at makes this review otherwise severely inadequate. Edge diffraction, which I believe the OP was talking about is a different thing. It is prevalent in the mid to high frequencies. As the hemispherical wavefront goes from driver to the edge of the baffle, the corners can cause the signal to re-emit. Instead of hearing just a tweeter: (T) You hear the tweeter plus the edges: |----------(T)----------| with the edge emissions being delayed.It is similar to the idea of first reflection points in a room. There are many approaches to this issue:
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Unless you are using a waveguide,felt is good. Madisound offers felt rounds for just such a purpose. You should also experiment however with the area between your speakers. I have often found that harshness in the highs comes from not enough damping there. Try throwing a blanket there and see what happens. :) Best, E |
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I think that it could be a bad thing too, depending on how the speaker was designed. I owned a pair of TDL Monitors years ago, a large 4 way floorstander, and I experimented with doing that around and between drivers, and to my surprise the blend of the drivers then became disjointed, I ended up doing it lightly just around the tweeter with some benefit. |
