Let's Face It, I Was A History Major

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Although I've asked a few times what exactly this contraption is for, I have absolutely zero capactiy for the retention of the answer....it's just that far over my head.  I'm pretty sure it measures something.   The logical part of my brain came up with that all by itself.

This is bolted to the wall down in the Engineering and Technology Center, right next to the anechoic chamber (you can see the spinning wood door to the left).  I'm sure one of our fine engineer-types will chime in on this blog to let everyone know how they can't believe I've been here 7 1/2 years, and still have no idea what this thing is for.  And maybe they'll be so kind as to let us know, after they are through pointing and laughing.

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Published 21 January 2008 09:25 AM by Amy Unger
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Comments

# Andy W said on 21 January, 2008 10:00 AM

It's a "plane wave tube". It's used to measure a compression driver without the effects of the horn.  You're looking at the flange end - where the driver is bolted.

There is a coupler where the flange meets the tube - this is where the measurement microphone is inserted.

The tube prevents the natural spherical expansion of the sound wave; it also eliminates any boundaries.  Whenever sound waves hit a boundary there will be a reflection and /or a refraction.  The reflection or refraction will be picked up by the measurement mic and will be summed with the direct wave.  The result, depending on whether the it is in or out of phase (or somewhere in between), will be peaks and dips in the response curve.

The tube is filled with a wedge of foam (narrow at the flange end, and almost filling the tube at the other end).  This will gradually attenuate the sound (absorb its energy).  We do this because we can't make a tube that is infinitely long.

The wooden chamber at the far end is stuffed to absorb any sound that is left, and therefore there are no (measurable) reflections at the mic.

# Amy Unger said on 21 January, 2008 11:06 AM

I knew Andy wouldn't let me down!

# ClaudeJ1 said on 21 January, 2008 11:55 AM

I don't work for Klipsch, but I have an engineering and management background with DIY audio.

Those things on the shelf are adapters for various driver mounts and there appears to be both 1" and 2" throat flanges at the near end, which are industry standard sizes.

they "level the playing field" when testing different drivers and different design iterations. Very useful tool, indeed!

# Professor Thump said on 21 January, 2008 01:50 PM

You guys have it all wrong.  This is a hand rail for the stairs the giants use.  I keep explaining this to Amy but she just can't grasp it!

Not! :)

# Lonelobo said on 26 January, 2008 05:23 PM

I have some infinately long tubing, but shipping is outrageous so it's only available for local pickup.  Just bring an infinately long truck and you can have it for free.

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