CBT36 Array - Page 5 - AVS Forum
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post #121 of 129 Old 02-01-2014, 09:40 AM - Thread Starter
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Originally Posted by Martycool007 View Post

Also, just out of curiosity, when designing and building a line array, how do you know what the optimal number of tweeters and mids would be? I can only imagine how nice a RAAL based line array would sound! Just wonder how many of them it would take to give a great SQ? I would also assume that the cheaper Fountek NeoCd3.0 ribbon tweeter would sound terrific in a line array!

The length of the line determines how far in distance and low in frequency the nearfield can be extended. Keeping the driver lines close in length is important. The number of drivers and wiring scheme has to be considered so that the impedance is reasonable for your amp(s). If it's a straight array I've found a 4-5 ft. long line can work pretty well though if you can go longer than that you can increase your output capability and vertical coverage (provided the line is shaded). Smaller ribbons like the CD3.0 could be used if the woofer line is designed to allow for a higher crossover point.

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post #122 of 129 Old 02-01-2014, 10:15 AM
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Originally Posted by Rick Craig View Post

... If it's a straight array ...
Rick:
Are you aware of anyone implementing the techniques from Don Keele
"Implementation of Straight-Line and Flat-Panel Constant Beamwidth Transducer (CBT) Loudspeaker Arrays Using Signal Delays," presented at the 113th Convention of the Audio Engineering Society, Los Angeles (Oct. 2002)

http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2002-10%20AES%20Preprint)%20-%20CBT%20Paper2.pdf

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post #123 of 129 Old 02-01-2014, 11:53 AM - Thread Starter
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Originally Posted by WVSyd View Post

Rick:
Are you aware of anyone implementing the techniques from Don Keele
"Implementation of Straight-Line and Flat-Panel Constant Beamwidth Transducer (CBT) Loudspeaker Arrays Using Signal Delays," presented at the 113th Convention of the Audio Engineering Society, Los Angeles (Oct. 2002)

http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2002-10%20AES%20Preprint)%20-%20CBT%20Paper2.pdf

Yes, THX did this and I know of some others experimenting with it as well.

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post #124 of 129 Old 02-01-2014, 01:39 PM
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Originally Posted by Rick Craig View Post

... and I know of some others experimenting with it as well.
Do you have any details about how they implemented the delay?
Thanks

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post #125 of 129 Old 02-01-2014, 04:26 PM
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Rick,

I am curious about the tweeters used in your Gamechangers. In the CBT36, a point is made that the very small, closely spaced tweeters help to avoid comb filtering below about 15K. The tweeters used in the Gamechangers are larger (1" domes?) and more widely spaced. Theoretically, shouldn't that affect the sound quality? Any noticeable effect?

The reason I am asking is that I am considering using 84 1/2" Parts Express tweeters used in the CBT36 as a tweeter line next to a BG RD75.
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post #126 of 129 Old 02-01-2014, 06:54 PM - Thread Starter
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Originally Posted by WVSyd View Post

Do you have any details about how they implemented the delay?
Thanks

We've discussed it some but I don't know what specific approach they are using now.

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post #127 of 129 Old 02-01-2014, 07:31 PM - Thread Starter
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Originally Posted by gworrel View Post

Rick,

I am curious about the tweeters used in your Gamechangers. In the CBT36, a point is made that the very small, closely spaced tweeters help to avoid comb filtering below about 15K. The tweeters used in the Gamechangers are larger (1" domes?) and more widely spaced. Theoretically, shouldn't that affect the sound quality? Any noticeable effect?

The reason I am asking is that I am considering using 84 1/2" Parts Express tweeters used in the CBT36 as a tweeter line next to a BG RD75.

3/4" domes with spacing that makes them uniform up to 10K. I've also used 1" domes in straight shaded lines with good results. The linearity, power handling, and sensitivity of the larger tweeters in my opinion greatly outweighs the comb filtering plus I can adjust the response above 10K with the DSP EQ from my DEQX unit. The effect is very angle dependent so I think the composite response tends to offset the audible effects of the combing.

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post #128 of 129 Old 02-02-2014, 12:00 AM
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I wish there was a polar response of the Gamechanger.
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post #129 of 129 Old 02-02-2014, 04:08 PM
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Originally Posted by omholt View Post

A waveguide even at a size of 15" has wide and no controlled directivity below 1000-800 Hz and it beams in the highs. To call that a better directivity is a misunderstanding IMO. The result is coloured reflected energy and an unven response below 1000-800 Hz compared to a CBT.

True in the lower freq but our ears are much more sensitive between 1 and 3 kHz.

And I wouldn't say that a WG with 1" throat beams more than a 1" dome, and in fact will have much better directivity control and power response.

All of which is not to say that the CBT may not be better sounding.

[edit] Well I was *very* surprised to read that regarding localization

"1000 to 3000 poor Neither timing/phase nor intensity differences predominate."

I thought we were most sensitive to imaging cues in that range; perhaps it's just SPL.

from a little more than half way down the page here

http://web.archive.org/web/20100410235208/http://www.cs.ucc.ie/~ianp/CS2511/HAP.html

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