Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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Thanks for the inputs!

Posted by tomservo (M) on November 28, 2006 at 20:28:58

In Reply to: How big was it? posted by tomservo on November 23, 2006 at 09:15:51:

Hi All

Thanks much for your inputs, I am pleased there are others who do not think a shoe or matchbox is the ideal size. To get to the point of CJ’s post and the reason for asking how big..

Bigger is better for a few reasons.
If one fixed the box volume but lowered the low cutoff an octave, one takes a 9dB hit in sensitivity. If your trying to stay below thermally related changes in response, one must stay below about 1/8 to 1 / 4 rated power for that driver.

Larger is better for directivity, if one has a large planar radiator, then one has a significant a mouth of directivity over a point source.
The more directivity one has, the larger the near field is for that frequency.
The larger the near field, the further away you can be and still be dominated by direct sound, the better the stereo imaging (when present in the recording).

What I have is a basic design for a speaker which in its current form (a commercial sound speaker) does a number of interesting things.
It preserves the waveshape of the input signal (square wave in = square wave out) over about the same range as a quad esl-63, a decade.
Unlike the quad, It has high sensitivity (100dB 1W1M) and handles a larger input power but has VERY low distortion at “home” levels..
The design combines the outputs of a number of drivers in a way which causes the seam to be “invisible” in both amplitude, phase and radiation pattern.
It looks like it is one constant directivity source with the acoustic phase response of one driver.
We sell these at work for commercial sound but because of the acoustics involved, the sound (with a suitable subwoofer) is like the hif speaker I always wanted.
Unlike hifi speakers there is no driver to driver interference, no lobes in the radiation pattern and very few speakers preserve time enough to reproduce the input waveshape over any frequency span (although the Manger bending wave transducer is the best I have ever seen).

The speakers I have from work are too big for home use and they sit on a much too big for home subwoofer. Having a pair of subs that each have a 97 dB half space sensitivity @ 23Hz is fun watching movies though.
Anyway, I’m trying to figure out how to package a low frequency element in with or maybe as part of a smaller, lower power Synergy horn in a package that wouldn’t cripple what it does.
I’m thinking the center of the horn will about half way between ear height standing and sitting, with probably a 50X50 degree radiation angle. The horn mouth would likely be about 18 inches wide, which at 50 degrees would control the radiation pattern down to about 300Hz.
Anyway, thanks again for the inputs.
Best Regards,
Tom Danley

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