Chris: I can't see that. The model of narrowing dispersion is valid for an isolated driver, but with a tightly spaced array, the vector sums must include surfaces from the other drivers, not just between elements on the same cone.
Dave: I think you're homing in on the part that I'm not getting yet: in the limit where the drivers are pont sources, Jim's comb-filter model would seem to be appropriate. In the limit where the flanges disappear, we get a continuous radiator with a smooth response. So... what happens in between, and how does that vary with flange width?
Dave: I think you're homing in on the part that I'm not getting yet: in the limit where the drivers are pont sources, Jim's comb-filter model would seem to be appropriate. In the limit where the flanges disappear, we get a continuous radiator with a smooth response. So... what happens in between, and how does that vary with flange width?
what about those conical drivers that sorta have a cone that is shaped more like a long horn, and the outside of the horn radiates the sound in an omnidirectional fassion. Its placed either facing up or down. Doesnt the high frequency travel and radiate from the entire length of the cone structure?
I wish I could find some pictures of measured sound dispertion at various frequencies, but I cant seem to find any at the moment. I know there are lots of them out there, maby someone else can post some.
Think about the amount of overlap that a bass note will have with a driver right next to it. The sound fills nearly 360 degrees, so the amount of sound energy that overlaps will be substantial. The overlap is what causes the sound waves to join together and form a line front, not that the boundaries of the sound wave touch. Assuming the same distance a higher frequency will have a narrower sound dispertion and a lower % of the sound energy will overlap to form a line source.
Think about two waves traveling in the ocean, if the front tip of one touches the back tip of the other, they waves stay the same size, but when they start to overlap, thats when it becomes more powerfull.
On a personal note, however, I am currently using a mono OB line array of the .69ers in my room, unmodified with an OB array of 10's covering the lower notes. I find it very listenable, but I can tell that a little something is missing on the top, but I'm not sure if it is enough to justify adding a XO to the line array and the cost of the tweeter + the time to design and test a good crossover.
Think about the amount of overlap that a bass note will have with a driver right next to it. The sound fills nearly 360 degrees, so the amount of sound energy that overlaps will be substantial. The overlap is what causes the sound waves to join together and form a line front, not that the boundaries of the sound wave touch. Assuming the same distance a higher frequency will have a narrower sound dispertion and a lower % of the sound energy will overlap to form a line source.
Think about two waves traveling in the ocean, if the front tip of one touches the back tip of the other, they waves stay the same size, but when they start to overlap, thats when it becomes more powerfull.
On a personal note, however, I am currently using a mono OB line array of the .69ers in my room, unmodified with an OB array of 10's covering the lower notes. I find it very listenable, but I can tell that a little something is missing on the top, but I'm not sure if it is enough to justify adding a XO to the line array and the cost of the tweeter + the time to design and test a good crossover.
rdf said:
It would if it weren't a flawed assumption. a flat radiating piston starts to beam as the wavelength approachs a multiple (nominally 1/3) the diameter of the piston.
As i said earlier, if someone could com up with the hypothetical radiation in SY's thot experiment they could make a lot of money.
dave
PS: the flange is a red herring.
My take is SY's talking the idealized case of an ideal flat radiating driver. If two such rectangular drivers with infinitesimal frames are butted edge-to-edge it must be so, nothing differentiates the pair physically from a single rectangular driver doubled along one dimension. No differential movement between surfaces and no gap. While it's correct individually they begin to beam above a certain frequency the effect is offset by their output summing at 90 degrees to the long dimension.
someone else can crunch the numbers... here is the math for the directionsl characteristic of SY's ideal rectangle. R is the ratio of the level at angle alpha vrs the on-axis level.
from Olson
dave
As i understand SY's argument, R would need to be 1 for all reasonable lambda & alpha
from Olson
dave
As i understand SY's argument, R would need to be 1 for all reasonable lambda & alpha
Attachments
Only if you define "a driver's dispersion" as being the dispersion one would get if the driver were separated from the other elements. The array dispersion is a different matter, more relevant, and I'm trying to understand that better.
As you might guess, I have a selfish reason for my interest in understanding this...
I'm buried under work at the moment and don't have time to persue it further but 'The Edge' baffle diffraction modelling software might be capable of modelling this by using a very large baffle and square drivers, the latter which can be set to arbitrary precision. Finite element analysis + a little algebra to convert mic height and distance into angle is more appealing than integrals.
Very interesting discusion. And I'm still very interested in maybe building some line arrays with full range drivers. Did anybody read Russell's article in the July 2006 AudioXpress? I'd really like to know what drivers he uses, so I can get a handle on the cost of the project before I go to the trouble of ordering a back issue of the magazine.
Also, are there any other full range line source designs out there on the web for DIY (other than the Parts Express Kuze 3201's)?
Also, are there any other full range line source designs out there on the web for DIY (other than the Parts Express Kuze 3201's)?
I believe he used Pioneer 4" drivers known as NSBs. At least this sure sounds like them:
"I tested a couple of them for him and for the 69 cent price, these 4-inch drivers worked well enough to test my theory"
They are no longer available but there are large stockpiles out there that may be had if someone wants to sell them.
http://www.partsexpress.com/projectshowcase/nsb/nsb2.htm?CFID=4125572&CFTOKEN=48232143
I too would be interested in what the article in audioXpress has to say. The design of the eq is what I would be most interested in. He says:
"Those particular drivers, when combined with equalization, provided response from 25 Hz to about 15 kHz. Power handling was very high and imaging was outstanding. The cabinet size was 87-1/2” high, 6-1/2” wide and 9-1/4” deep without the base. I wrote an article about this first prototype system titled “A Unique Stereo Column System” that was published in audioXpress magazine in November 2005. The design included two of my previous patents: speaker equalization and drivers arranged in a long column"
Getting down to 25hz using a driver with Fs of 105 would be quite the trick I should think. Wonder if the schematic is presented.
amt
"I tested a couple of them for him and for the 69 cent price, these 4-inch drivers worked well enough to test my theory"
They are no longer available but there are large stockpiles out there that may be had if someone wants to sell them.
http://www.partsexpress.com/projectshowcase/nsb/nsb2.htm?CFID=4125572&CFTOKEN=48232143
I too would be interested in what the article in audioXpress has to say. The design of the eq is what I would be most interested in. He says:
"Those particular drivers, when combined with equalization, provided response from 25 Hz to about 15 kHz. Power handling was very high and imaging was outstanding. The cabinet size was 87-1/2” high, 6-1/2” wide and 9-1/4” deep without the base. I wrote an article about this first prototype system titled “A Unique Stereo Column System” that was published in audioXpress magazine in November 2005. The design included two of my previous patents: speaker equalization and drivers arranged in a long column"
Getting down to 25hz using a driver with Fs of 105 would be quite the trick I should think. Wonder if the schematic is presented.
amt
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