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In Reply to: RE: How does loudness fall with distance from speaker? posted by ph5y on June 10, 2016 at 06:52:25
Double the distance and SPL falls 6db.
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True for most speakers but not for planars and line sources where the drop is basically linear, I believe.
Planars and line sources follow the same inverse square rule unless they're at least 3 wavelengths in dimension, and even then they will revert to the inverse square rule at a distance.
Hello Bill:
Yes 3 WL lengths line arrays to keep those freq in the near field but directional line arrays like the few horn and rear cancelling designs claim to be able to reduce their length and maintain lower than expected freqs in the near field. Never really been able to understand that.
Rafaro
The straight line array can have a reduced SPL fall off, even half of a point source but this only happens when the line is long compared to wavelength.
The weakness of the design is that this is very frequency dependent so most line arrays are curved to make them more like an astigmatic point source instead which reduces the spectral balance change with distance, while reduced, the interference pattern they produce imposes a limited working distance requiring "delay rings".
A true point source in a large horn can have much greater throw, have little or no distance related spectral change, sounds better, is more intelligible and is smaller, with the down side of being a smaller sale for the dealer.
+1
Point source horns over line arrays.
Hello Tom, Dennis and group:
Walking within the nearfield of a line array I can appreciate the stable sound pressure but always get the feeling of a synthetic nature to the sound. The chaotic nature of the sound reconstruction within it to me its audible and distracts from the performance. This is understandable considering that we evolved our hearing listening to point sources and as such find them sounding natural. The popularity of line arrays seems more to do with the ease of mounting and dismounting them and ease in providing SPL coverage but at the expense of a natural stable sound spectrum. Your designs Tom are based around your patents with innovative point source horns. I hold your designs in the highest regard. My interest in speaker design started after getting "dumped" the Job of setting up the sound system in addition to playing bass in the band. By necessity I rapidly evolved to high efficiency compact but expandable exponential horn designs. I have enjoyed the learning experience perfecting the designs and I am happy with results but I donīt play or even do Gigs anymore. Anecdotally it does seems that line arrays with directional speakers expo horns in my case can produce lower than predictable freqs using shorter columns.
Regards
Rafaro
" I believe."
hahax
(I think not)
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