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Discussion Starter #1
Hi all,

Lat night I discovered that the tweeter dome on one of my mains had a small dent in the center (I have no idea when it happened, either... I know I inspected them when I got them... oh, well). A little research tells me that the effect on the sound will depend on if the dent deforms the voice coil around the circumference (which it doesn't). Just for grins, I took a sweep of the damaged tweeter and it's brother (at 3') for comparison, the idea being that any big difference would be due to the damaged tweeter. I know that using the Galaxy 140 is not accurate for measuring full range, but I was not interested in accuracy, only consistency (I figure that both sweeps would be inaccurate in the same way).

The weird thing is, the tweeter dome is protected by a thin plastic bridge in the face plate, and careful inspection reveals that the dent was made by the dome impacting the bridge from behind it. How that happened, I'm not entirely sure (there have been a couple of times I misjudged the volume, and ran for the remote...but why was it's brother spared?).

Here is the left main (with the dented tweeter):

left main.jpg

...and here is the right main (tweeter is OK):

right main.jpg

The only significant difference I can see is the spike/dip at 10k. I know that smoothing should not be used for low frequencies, but how much smoothing is realistic to account for all of the room reflections here? 1/3? 1/12? None? I have a replacement tweeter on back order just in case...
 

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The smoothing is used to get a better idea of the underlying trend of the signal when there is so much comb fitering caused by reflections it's hard to read. To come a bit closer to how you actually hear use 1/3 octave smoothing.

Interesting interference at 10K......

brucek
 

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Discussion Starter #3
Thanx, Bruce!
 
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