If you using a 75 degree waveguide tweeter with a direct radiating Mid driver, won't you have to crossover above the pistonic range if you want matching directivity? In other words you'll have midrange cone breakup in you response.
Does that seem correct?
Is there any reason you'd want this directivity pattern?
Thanks,
Dan
Does that seem correct?
Is there any reason you'd want this directivity pattern?
Thanks,
Dan
Exactly what I was thinking.
So why does Parts Express build a 75 degree waveguide which in my measurements are down 9 dBs at 45 degrees. My ten inch woofers then have to be crossed higher into their break-up region in order to match them. About 2.5 kHz instead of 1.5kHz for a 90 degree WG. It seems a 75degree WG would only make it harder for the DIY community to get their design right by doing this--there's a good chance the woofer's response will be rippled and have an erratic decay plus the center to center spacing at the crossover frequency will be further apart. So I figure there must be a good reason to build such a device. My guess is that it will work better in larger rooms b/c it can minimize early reflection problems. It seems that the benefit wouldn't outweigh the advantages in anything but a large have or gymnasium or if you are concerned with mastering your own score. Any other input?
Thanks,
Dan
From Altec literature...
Variable ka is the ratio of the circumference of the speaker, or baffle, to a wavelength. High ka numbers indicate high frequency. A loudspeaker will be omnidirectional starting at ka=1 and the beamwidth will halve for each octave increase in frequency. A baffle will act as a half-space baffle until it reaches about ka=2, where it makes a transistion (45 degrees on log/log graph) to 360 degrees at ka=1. Half space radiation is about 160 degrees (-6db) in real world situations instead of the 180 degrees predicted theoretically. Any loudspeaker in a large baffle is not affected by that baffle at high frequencies where the free-air beamwidth is smaller than 160 degrees or so.
Variable ka is the ratio of the circumference of the speaker, or baffle, to a wavelength. High ka numbers indicate high frequency. A loudspeaker will be omnidirectional starting at ka=1 and the beamwidth will halve for each octave increase in frequency. A baffle will act as a half-space baffle until it reaches about ka=2, where it makes a transistion (45 degrees on log/log graph) to 360 degrees at ka=1. Half space radiation is about 160 degrees (-6db) in real world situations instead of the 180 degrees predicted theoretically. Any loudspeaker in a large baffle is not affected by that baffle at high frequencies where the free-air beamwidth is smaller than 160 degrees or so.
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That's funny. I've debated audio nuts and gurus that claim just that point with me--even a manufacturer!
Yet they have literature and/or design criteria proclaiming their products' and/or builds' superiority. "Just don't make sense."--Ross Perot LineSource, thank you for that information! It is useful. I think I actually understand it. hahaha
Dan
I heard some of these just the other day. They were painful even at reasonable listening levels. I've got some at home at the moment that aren't bad. Not incredible, but not painful for the most part. They are a VERY rough build--well actually not built yet to any real degree. Just in the design and listen phase.
Dan
Different reasons entirely? I think I know what you mean, but maybe not. I think some of the reasons are the same.
Dan
Mostly different. In a large venue I want high directivity so as to get the sound only where I want it because I can't afford to waste any. In a small room I have much more sound than I need so wasting it is not an issue, but I want to avoid the room boundaries so I need high directivity. Seems different to me, but its all how you look at it I suppose.
The ability to aim the sound where it's needed and avoid VERs is what I was getting at. It's just POV. Either way I like the idea of controlled directivity.
Dan
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