Baffle width and roundovers

[Ryan_M]

Since I don't know enough to figure this out on my own I hoping someone can answer this for me. I'm wondering how or if roundovers affect the spec'ed baffle width for a given design. I figure small roundovers (i.e. 3/4"R) don't have any effect. For instance if a design says the baffle should be 11" wide and I use a 3/4" roundover bit on the baffle edges everything is just fine.

But what about a large roundover, say 3" radius for example. Does the flat part of the baffle need to be 11" or the outsides of the roundovers need to be 11" (as in a flat front of 5" width) or does the answer lay somewhere inbetween?

[JRT]

Since I don't know enough to figure this out on my own I hoping someone can answer this for me. I'm wondering how or if roundovers affect the spec'ed baffle width for a given design. I figure small roundovers (i.e. 3/4"R) don't have any effect. For instance if a design says the baffle should be 11" wide and I use a 3/4" roundover bit on the baffle edges everything is just fine.

But what about a large roundover, say 3" radius for example. Does the flat part of the baffle need to be 11" or the outsides of the roundovers need to be 11" (as in a flat front of 5" width) or does the answer lay somewhere inbetween?

I suggest you model it using either BDS (baffle diffraction simulator) or Edge, or perhaps both.
Then you can compare the effects of variations in edge radii and baffle widths. Follow the links.





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[curt_c]

I suggest you model it using either BDS (baffle diffraction simulator) or Edge, or perhaps both.
Then you can compare the effects of variations in edge radii and baffle widths. Follow the links..

Edge, strangely enough, doesn't model edge modifications. -Certainly a significant oversight in an otherwise excellent program. BDS is the best bet here. Investigate chamfers as well, as they can be easier to implement and nearly as effective.

C

[Pete Schumacher ®]

Edge, strangely enough, doesn't model edge modifications. -Certainly a significant oversight in an otherwise excellent program. BDS is the best bet here. Investigate chamfers as well, as they can be easier to implement and nearly as effective.

C

And for rectangular baffles, don't forget Jeff's Diffraction modeler.

[JRT]

Edge, strangely enough, doesn't model edge modifications. -Certainly a significant oversight in an otherwise excellent program. BDS is the best bet here. Investigate chamfers as well, as they can be easier to implement and nearly as effective.

C

I've used BDS, but not Edge.
...shouldn't have recommended something I haven't used.

Thanks for clarifying.





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[fbov]

To first order, baffle width drives baffle step compensation while baffle roundover drives high frequency response.

Baffle step compensation adjusts tonal balance over many octaves, mostly below 1KHz where wavelength is still large compared with baffle width. It's compensating for the difference in driver low end output depending if a driver is radiating in "all directions" - a spherical pattern - or just a hemisphere, as when mounted on a wall. Since the only true spherical pattern comes from a point source, any baffle-mounted driver is somewhere between spherical and hemispherical conditions. the baffle width just determines where inbetween.

Roundover affects diffraction, starting at wavelengths that are twice the distance from the driver to the edge (1/2 wave cancellation). A sharp edge that's 4" from the driver would have maximum diffraction effects starting at an 8" wavelength, about 1.7KHz. The effect is maximized by a round baffle - all edges at the same distance - thus the practice of offsetting tweeters L-R and sometimes putting them as close to the top as possible.

There will be interactions, but that's a second-order effect best investigated via simulation, as others have suggested. It just helps to understand the fundamentals before diving into the details.

Have fun,
Frank

[Ryan_M]

Investigate chamfers as well, as they can be easier to implement and nearly as effective.

C

I wasn't so much after it being 'effective', more so for aesthetic reasons. I just want to be careful that (for example) building a 12" wide baffle with 3" round overs won't require a change in the XO when the original design was built with the standard 3/4" roundover.

So I'm assuming the steps I need to take would be to model the 'as specified' baffle then model the same thing but with a large roundover and compare... but then what am I looking for? How will I know if it will not work with the XO as designed?