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Old 6th December 2012, 02:19 AM   #351
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Originally Posted by soundaatma View Post
As narrow baffles are the best to maintain the dipole characteristics of CD till the top end of the spectrum, why not use a line array of six to eight, 3" FR drivers with good xmax like the inexpensive Aurasound NS3 instead of a 6" and a 3-4" driver with a crossover.
The NS3 has enough xmax to equalise the low end flat down to 100Hz, below which any sized dipole woofers can take over. A 4" wide baffle of an array of NS3 can maintain CD as high as 4-6KHz above which opposite facing tweeters can be employed. This option even with eight NS3 drivers per side, would certainly be a lot cheaper than a actively crossed equalised and amplified combination of a 6" and a 4" driver.

The only issue might be comb filtering in the vertical axis
I like this idea. If you had 8 three inch Peerless TC9FD-18-08 drivers ($12 ea. at PE or Madisound) (3 inch "full range") (or equiv.) for example, in a vertical line array going from 125HZ (4th order) to 7kHZ, That could be very good. Above 5-6kHZ our ability to localize images drops off dramatically, so integration might be fine with one dipole tweeter at least 42 inches off the floor. I doubt if comb filtering on the vertical axis would be a significant problem. Having no crossover point from 125 - 7KHZ could be special. A speaker that narrow could have stunning imaging. Especially in the lower midrange where we determine image location primarily by timing or phase comparisons.

The best reason for having a larger driver is because of the Xmax required in an open baffle situation. Because of that, I would actually consider doing a closed box, with separate drivers on the front and back. You still have a dipole, if you know how to dampen the chambers right that should be plenty fine, and now the Xmax can be about 1/3 what it would need to be with open baffle. And you have a very narrow transducer for better imaging...
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Old 6th December 2012, 02:26 AM   #352
dewardh is offline dewardh  United States
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I really think that a big part of the better sound he is getting from his new design has to do with stress releave from the 1" dome tweeters.
It depends, I suppose, on how loud you listen. A 1" dome will deliver 100dB at one Meter at 1500Hz. at .5mm xmax (1mm peak to peak). If you're crossing it LR4 that means you can get 105 dB out of the system. How that will sound will depend on lots of things, including the distortion the tweeter is producing at xmax, but it does set a clear limit at which obvious distress is likely to be heard.

Most acoustic (orchestra etc.) sources are unlikely to be producing their maximum output at that frequency, so the demand from a "105dB source" is likely to be a lot less, but trumpets, trombones, saxaphones and maybe even a couple flutes might push it if you're looking for front row levels (but not at normal levels for mid-house seating). For electronic or amplified music, or if you like things "louder than life", then it's certainly possible to overdrive a tweeter crossed that low.

A 4" driver (2.6" diameter cone) with the same xmax will give about 117 dB at the same frequency, and close to 130 dB with a not-hard-to-find 2mm xmax, so if you like it loud that's clearly the way to go (if the rest of the system can keep up).
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Old 6th December 2012, 02:32 AM   #353
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The best reason for having a larger driver is because of the Xmax required in an open baffle situation. Because of that, I would actually consider doing a closed box, with separate drivers on the front and back. You still have a dipole, if you know how to dampen the chambers right that should be plenty fine, and now the Xmax can be about 1/3 what it would need to be with open baffle. And you have a very narrow transducer for better imaging...
Mounting drivers back to back in a box has nothing to do with the Xmax requirements. What matters is the volume velocity (Xmax x Sd), the dipole moment (front to back separation) and the low frequency cut off.
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Old 6th December 2012, 02:54 AM   #354
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John, how do you feel about using eight 3" drivers with good xmax like the NS3 from 120 to 6khz instead of the two midrange drivers with crossover in the critical range. The Sd x xmax will be equal or even better in this case with narrower baffle allowing better CD even higher.

Last edited by soundaatma; 6th December 2012 at 03:00 AM.
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Old 6th December 2012, 03:07 AM   #355
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John, how do you feel about using eight 3" drivers with good xmax like the NS3 from 120 to 6khz instead of the two midrange drivers with crossover in the critical range. The Sd x xmax will be equal or even better in this case with narrower baffle allowing better CD even higher.
As in with a tweeter at center?
Or a line of tweeters.
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Old 6th December 2012, 03:15 AM   #356
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As in with a tweeter at center?
Or a line of tweeters.
Line of tweeters would not be necessary and 2 opposite facing tweeters should suffice. Tweeter in the center of the 3" line would increase interdriver distance in the 3" FR array, so perhaps the tweeter pair at the top of the array may be a better idea.
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Old 6th December 2012, 03:20 AM   #357
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Line of tweeters would not be necessary and 2 opposite facing tweeters should suffice. Tweeter in the center of the 3" line would increase interdriver distance in the 3" FR array, so perhaps the tweeter pair at the top of the array may be a better idea.
So, which is it? Line of tweets? Or at the top?
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Old 6th December 2012, 03:53 AM   #358
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As in with a tweeter at center?
Or a line of tweeters.
Line of tweeters would not be necessary and 2 opposite facing tweeters should suffice. Tweeter in the center of the 3" line would increase interdriver distance in the 3" FR array, so perhaps the tweeter p

Last edited by soundaatma; 6th December 2012 at 04:01 AM.
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Old 6th December 2012, 03:59 AM   #359
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As in with a tweeter at center?
Or a line of tweeters.
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So, which is it? Line of tweets? Or at the top?
I would prefer 2 opposite facing tweets at the top for 7k and above.
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Old 6th December 2012, 04:03 AM   #360
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I would prefer 2 opposite facing tweets at the top for 7k and above.
That would have a peculiar polar pattern to say the least!
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