Did Karlson Blow the Kurve?

I am trying to reduce floor bounce interference and moden technology typically lines up the woofers vertically to distribute the bounce over a longer area reducing its impact.

My intent is to do somthing similar, but using a Karlson-type curve placed in front of the cabinet. The Karlson curve is well documented online and shown below.
http://i.imgur.com/oRygnBt.png

When plotted in a Cad program, the curve comes out as below. Because my cabinet is not quite as tall as a Karlson design, the thinnest portion of the Karlson curve is "lopped off" in the drawing and therefore appears thicker than their design.
http://www.audioheritage.org/photopo...t_02_12_44.jpg

But, upon closer examination, while the Karlson Curve may be an exponential curve, it does not curve in accordance with the way sound "curves." An exponential sound curve would double the cross-section at regular intervals. For example, if the cross-section is 1" at a distance of 5" down and 2" at a distance of 10" down, it should double again and be 4" at 15" down, 8" at 20" down, 16" at 25" down, 32" at 30" down, etc.

Looking at the plot data we see that 30" down, the cabinet is 20.34" across. One octave up should have a cross section of 10.17" and this occurs at roughly 21" down for a distance of 9". Therefore, if we go up another 9", the cross-section should be half of 10.17" or ~5.09". But this would occur at about 14.5" down or about 6.5" up, rather than the expected 9" up. So, the curve (or possibly spliced curves) does not adhere to the ways of sound.

A proper curve for sound ("The Brody Bend") for the same horizontal distance is shown below. This spans 6 octaves with each octave at regular invervals doubling in cross-section.

http://www.audioheritage.org/photopo...t_02_12_45.jpg

Thoughts?

Hi Todd,

Karlson boxes look kind of cool and are fun to contemplate, and certainly have an effect.

I'll speculate that at 30Hz to 300Hz a triangle cut out would be fairly equivalent... or a rectangle or oval.
More like a slightly resistive port or lossy slot loading.

Even JBL has that funky bit they put in front of PA woofers for more even dispersion (currently eon 612/615)
not really for floor bounce though.

Is it really a concerning and measureable woofer issue? or coming from the mid-bass drivers?
Hard to see the woofer getting closer to the floor without tilting it forward... :hmm: perhaps do that and add some triangular side panels to make a short loaded-to-the-floor manifold.
Is that sort of what you are trying to accomplish anyway?

Fun to experiment!

-dave/grumpy

Quote:

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Originally Posted by grumpy

Hi Todd,

Is it really a concerning and measureable woofer issue? or coming from the mid-bass drivers?
Hard to see the woofer getting closer to the floor without tilting it forward... :hmm: perhaps do that and add some triangular side panels to make a short loaded-to-the-floor manifold.
Is that sort of what you are trying to accomplish anyway?

Fun to experiment!

-dave/grumpy

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Spectrum of the 2241H at the seating postion. I get similar from the 10" except that the dip is shifted by one band on the analyzer. May be floor and/or back wall bounce.

I did put a piece of foam core in front of the woofer completely sealing off the panel and the bounce mostly goes away and the whole band is much smoother. But I feel that perhaps this muffles things a bit so decided to try a slot.

My first slot was a V and the results were between that of the foam core and no foam core. Ergo, I thought a modified slot may work better..., or not.

Sliding the mid well back on the woofer cabinet creates a "shelf" and this actually does a fairly good job of reducing the dip for the mid, which is why I'm thinking floor bounce, at least to some extent. But this perhaps messes with the time alignment and possibly imaging a bit. I have no way to quickly A/B this though. I currently have it slid back further than shown, just behind alignment, and placed a piece of foam flat on the cabinet just in front of the mid. I have not yet run the RTA on this scenario to see if this foam is of any consequence though.

Measureable??? Most definitely.

http://www.audioheritage.org/photopo...DSC_000113.JPG

http://www.audioheritage.org/photopo...DSC_000413.JPG
http://www.audioheritage.org/photopo...DSC_000510.JPG
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