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Old 28th August 2006, 10:29 AM   #1
deiksac is offline deiksac  Czech Republic
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Default driver offset - time alignment vs diffraction

One question - I am about to rebuild my boxes (using seas excel drivers) and came to an idea to offset the speakers so that I get some time alignment. What am I unsure about: does the benefit of better time alignment outweigh resulting diffraction issues? Another idea was to round the woofer flange but as a result the distance between speakers rises.
The design is here - http://higherground.negercity.cz/dx/vezicka02.gif
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Old 28th August 2006, 01:15 PM   #2
badman is offline badman  United States
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The stepped baffle you propose would be fairly disastrous in terms of diffraction issues: a symmetrical ring like this is a big no-no. You can do 'time alignment' many ways, one is to move the tweeter off center towards the outside of the cabinet, or to do a slanted baffle- I think that a slanted baffle is in many instances the best choice for a normal 2 way with a dome, and then you simply make sure that you have the drivers at the appropriate height for on-axis listening in your space. I am fond of high efficiency tweeters, which generally means horns or ribbons, and a nice thing about them is that the motor is generally further back from the mounting plane, meaning: "time aligned" more easily. If you're really concerned with getting the tweeter and midwoof close together, I'd think carefully about what sub-baffle arrangement works best (perhaps an angular coupling

Avoid symmetrical baffle mounting at all costs- everything should be offset, preferably at "golden ratio" intervals to further disperse reinforcement/loss/etc.
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Old 28th August 2006, 01:25 PM   #3
deiksac is offline deiksac  Czech Republic
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Thanks Badman, I have thought so after reading some Rod Elliott's article earlier today. I know of benefits of ofsetting the drivers, but since the baffle is pretty narrow, I kept it centred (in the drawing) sofar.
Which way would you prefer - to slant the enclosure or go active and introduce some delay on the tweeter?
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Old 28th August 2006, 02:20 PM   #4
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Those who prefer domes over ribbons and horns may use waveguides like Genelec does.
Monacor for instance does even sell a waveguide matching one of their dome tweeters !

Regards

Charles
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Old 28th August 2006, 04:42 PM   #5
badman is offline badman  United States
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Well,
The active option has many positive points. I don't introduce active delay in my active crossover, but it's a perfectly valid approach. I do prefer to use somewhat wider baffles though, the slender baffle approach requires so much by way of baffle step correction....
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