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Re: I wonder what's going on electrically? [message #49037 is a reply to message #49035] |
Tue, 07 March 2006 06:00 |
Bill Epstein
Messages: 1088 Registered: May 2009 Location: Smoky Mts. USA
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Illuminati (2nd Degree) |
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While I had the temporary set-up apart and waited for the glue and then finish to dry I was listening to the basic 2-way: 902 and 2226. Union Station didn't sound that different but on the Redbook layer of the Stones "Hot Rocks" SACD, Mick's voice on 'Jumpin Jack Flash' was breaking glass all over the neighborhood! When I replaced the Vifa, first thing I did was listen to "Hot Rocks" again. The edge was gone to Mick's voice and the whole song sounded a little darker. I have/had the 902 padded 14dB and the Vifa has a 16OhmR in parallel and just the 3.0 cap in series for about a 13kHz cross. Can the Vifa be masking the 902 that much or is there just enough resihttp://img133.imageshack.us/img133/1015/supertweeter0051bz.jpgstance change with the 2 drivers in parallel to smooth out the treble?Besides the tone and improved imaging I also like what the super-tweeter "pod" enabled me to do for the convenience and wire dress of the cross-over. Can you find the cat?
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Re: I wonder what's going on electrically? [message #49040 is a reply to message #49037] |
Tue, 07 March 2006 07:25 |
spkrman57
Messages: 522 Registered: May 2009
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Illuminati (1st Degree) |
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Bill, You definitely bring up a interesting dilemma. I too have tried using some different horns/drivers with my 4 Pi pro's(as long as I have a JBL 2226 in the house-I have a 4 Pi to be able to use!)Right now there is a ALtec 806-8A on a 811B horn with EV T-35 tweeter. I am using 15 ohm parallel with 25 ohm series(bypassed with .33 ufd cap) and then running through a L-pad. The T-35 is using a .5 ufd oil cap with shunt .5 mh coil and L-pad also. If the tweeter level is to high, the mid horns sound too screechy and if the mid horns are to high, then the sound is shouty. Trying to add a powered sub in the mix adds more phase issues. The reason for the L-pads is so I can swap compression drivers and horns quickly. Ron
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Re: I wonder what's going on electrically? [message #49042 is a reply to message #49037] |
Tue, 07 March 2006 10:06 |
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Wayne Parham
Messages: 18787 Registered: January 2001
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Illuminati (33rd Degree) |
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Whenever I consider the interaction of a super-tweeter with the rest of the system, I always expect it to have dense interference with the adjacent tweeter just below it in frequency. It smooths the response through averaging, because the two tweeters cannot really be coherent. The tweeters form a two-element array that is several wavelengths apart so interaction is complex. It tends to smooth the field. Look at the energy distribution graphs in the pages on this link, and find those described as having dense interference. The document linked is actually about horizontal arrays, but your super-tweeter forms a vertical array with the tweeter just below it, so the concepts are the same, just on a different axis."Dense interference" is when lobing becomes so severe that response actually becomes smoother. It's massive comb filtering, but on a scale that averages the sound field rather than pitting it. Comb filtering generally produces deep nulls in response, but it is most noticeable when the out-of-phase region is fairly large, so there is a wide spot in the room where some band of frequencies is missing. If the interaction is so dense that nulls and peaks form every fraction of an inch (as is possible at high frequencies) then the sound field tends to average out.
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