How do we counter teh 90 degree phase shift in a 6 db? [message #19728] |
Fri, 06 February 2004 14:22 |
akhilesh
Messages: 1275 Registered: May 2009
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Illuminati (3rd Degree) |
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Hi Everyone, I should probably work this out myself, but it's friday! My question is: I have a full range driver, with a supertweeter corossed over at 16000 HZ at 6 db/octave. Both drivers have similar eff at 95 DB. The 90 degree phase shift that ensues: how do i counter that? Do i push the tweeter forward in relation to the full range? and by how much? Placement of the tweeter is TOTALLY flexible. -akhilesh
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You can't [message #19732 is a reply to message #19728] |
Fri, 06 February 2004 16:13 |
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Wayne Parham
Messages: 18786 Registered: January 2001
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Illuminati (33rd Degree) |
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Actually, a first-order crossover only shifts phase 90o at the asymptote, which is a fancy way of saying the stop band. The stop band is where the driver is attenuated, so this is sort of a "mute" point. Pun intended. Please notice the graph of phase shifts of first-order filters in the post called "Phase, delays and offset baffle spacing." These shifts are an inevitable part of the nature of filters. Both low-pass and high-pass filters are shown, and equivalent baffle offsets are shown at various frequencies. You can line up the tweeter and woofer (or fullrange) so that they are in phase at one frequency and at one specific listening position. Move off axis and the whole thing shifts. But I'm not sure this is really a huge problem when you consider that there are few sound sources in a home sound system, and there are walls and furnature and things of various sizes in the room to reflect different frequency components at different amounts and positions. The numbers of phase modifiers from the environment usually makes much more irregularity than do the electronics.
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