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Old 9th August 2004, 01:03 AM   #1
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Default waterfall plots

How do you interpret a waterfall plot? Also, is this a good one?
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Old 9th August 2004, 02:45 AM   #2
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On the Z axis is the time elapsed... so farthest back is the starting point, and time elapses as you come toward the screen (or yourself).

The X axis is the frequency. The Y axis is the sound level, with the reference point at the top, and decreases as you go lower, or toward the bottom of the X-Z plane.
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Old 9th August 2004, 03:39 AM   #3
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That's the worst waterfall plot I've ever seen!

The top (0 ms) curve is the output of the speaker and essentially represents the steady state frequency response.

Shortly after time 0 the input to the speaker is removed and we all wish the speaker would quite vibrating at that time. Alas, it does not and the lower curves represent the ouput of the speaker at the frequencies indicated along the bottom of the graph at the time indicated along the right of the graph.

A really good speaker would have pretty much died down within a few ms.
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Old 9th August 2004, 03:35 PM   #4
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Indeed that is truly horric.
I've never seen a WF extend to 60ms!!!! or even 10ms for that matter...
Which driver is that so I can avoid it like the plague?
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Old 9th August 2004, 03:54 PM   #5
tiroth is offline tiroth  United States
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testing error?
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Old 9th August 2004, 04:15 PM   #6
banana is offline banana  Hong Kong
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Maybe, it's not that bad.

Take a look at the frequency axis. 60ms decay is at 100Hz!!

Above 1KHz the WF does not looks bad.
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Old 9th August 2004, 04:40 PM   #7
SY is offline SY  United States
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Quote:
Originally posted by banana
Maybe, it's not that bad.

Spot on. Unless you know what is being tested and how, you cannot make a valid "good-bad" judgement. Nor can you say much about interpretation.

bonsai, why don't you fill in the details?
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Old 9th August 2004, 08:51 PM   #8
moamps is offline moamps  Croatia
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Hi,

this CSD graph looks like (sub)woofer responce at listening position in (little bit) too reverberant room. (prominent standing waves at 145, 290Hz...)

Regards
Milan
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Old 9th August 2004, 09:02 PM   #9
vuki is offline vuki  Croatia
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It looks like panel vibration measurement waterfall.
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Old 10th August 2004, 12:27 AM   #10
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the speaker in question is the Athena F2, a 2 way speaker system with 2 8" bass drivers. The waterfall plot was measured by a stereophile reviewer.. "Fig.2 Athena AS-F2, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the cabinet's side panel 12" from the top. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)" He did a couple of other waterfall plots, but i don't really understand which is the right one to be looking at.. Here is another one of the same speaker, using different conditions " Fig.7 Athena AS-F2, cumulative spectral-decay plot at 50" (0.15ms risetime)."
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