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First gig with QSC K10 speakers !
Art Welter:
Dick Rees wrote on Thu, 20 August 2009 15:24
Alan Roberts wrote on Thu, 20 August 2009 14:57
I've been concerned about what I perceive as a drop-off of high-frequency content after about 35 feet. Now, I will admit that my volumes are low, but it seems that other speakers I use may be better at projecting beyond 35 feet. I need to play with this a little more to make sure I'm not imagining things.
Alan....
What may be perceived as a "drop off" in HF 35' out into a room may actually be a result of the direct sound (at those frequencies) being overwhelmed and/or phase cancelled by the reflected sound. All bets are off once you go beyond the critical distance.
DR
Dick,
Not to quibble with what you say, but the more extended the HF of a speaker to start with, the more HF air loss is apparent.
For a speaker without much response above 10 K, the difference at 35 feet would hardly be measurable, while one with flat response to 15K would be around 4 dB down at that distance.
Art Welter
Don Boomer:
Hey Art
What's the source for the graph?
Ivan Beaver:
But take 2 loudspeakers.
One that is 6dB down at 15K and one that is flat to 15KHz.
At any distance the one that has the extended response will STILL have more HF-because it started with more-assuming the rest of the system was level matched.
The air loss will reduce the level of both the same (dB wise). The air doesn't care what what the starting level is (in a linear condition).
Art Welter:
Don Boomer wrote on Wed, 26 August 2009 12:41
Hey Art
What's the source for the graph?
It is on the EAW site.
Art Welter:
Ivan Beaver wrote on Wed, 26 August 2009 13:29
But take 2 loudspeakers.
One that is 6dB down at 15K and one that is flat to 15KHz.
At any distance the one that has the extended response will STILL have more HF-because it started with more-assuming the rest of the system was level matched.
The air loss will reduce the level of both the same (dB wise). The air doesn't care what what the starting level is (in a linear condition).
I agree with what you wrote.
My point was that listening to a driver that rolls off above 10K such as the JBL 2470, which is already more than 10 dB down at 15K, air loss does not really make a difference at 50 feet. Whether the response is -15 or -20, 15K will be pretty much inaudible even for golden ears.
The JBL 2425, on the other hand, at 50 feet would drop from about -3 to -8 at 15K, from “a little” to “a lot” down.
The K-10 is -6 at 18K, on axis probably fairly similar to the 2425 graph, air loss would be noticeable.
Art Welter
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