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Old 21st May 2007, 12:33 AM   #351
claudio is offline claudio  Italy
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CSD is one of the unfinished part of Speaker Workshop.

MJL could export the impulse responses from SW and import in another program that calculates CSD.
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Old 21st May 2007, 11:21 AM   #352
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Quote:
Originally posted by planet10
decay plots?

dave

Sorry Dave, as Claudio says there is not a utility for spectral decay in speaker workshop.
Claudio, what program will convert the impulse results to CSD plots? Or would the impulse tests themselves give enough infomation on decay without conversion? At this point I would have to go back and run the impulse tests, as I didn't in the first place.
Barring the decay, Dave what are your opinions on my findings here? Ready to put this one to bed?
I run a couple of damping tests on the baltic birch box: with loose stuffing (pink fiberglass) and with the walls lined with my rubber backed carpet. Will post those results shortly.
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Old 21st May 2007, 02:05 PM   #353
claudio is offline claudio  Italy
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MJL, actually to do a NF measurement you did an impulse response: if you haven't saved each IR you have to redo all the measurement, to get CSD or else.
My suggestion: use ARTA whose demo mode allows you to save the picture of the measurement; with ARTA you can calculate the CSD, the step response, so just repeat the measurements with this program, if you like, the calibration procedure is pretty quick.
Other program option, that I know, are Loudspeaker Lab, Praxis but I don't know what the demo mode allows.
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Old 21st May 2007, 02:10 PM   #354
Geoff H is offline Geoff H  Australia
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Arta will give CSD plots. I'm still getting a grasp on interpreting them.

30 dB is well inside our usual dynamic range. How much would you pay for an amp with a 30dB s/n ratio? Vinyl approached 60dB.

Impulse tests should show a difference.

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Old 21st May 2007, 02:50 PM   #355
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Quote:
Originally posted by claudio
MJL, actually to do a NF measurement you did an impulse response: if you haven't saved each IR you have to redo all the measurement, to get CSD or else.
I just did the pulse measurements for each box, and will post those results (which are just in graph form, but should give a good indication of decay for each material).
As far as installing Arta for this purpose, I resist. I have Speaker Workshop running and calibrated, and don't want to mess that up (took long enough to get that right). Besides, SW does everything I need it to do, and at this point, I know it's accurate.
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Old 21st May 2007, 02:54 PM   #356
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Quote:
Originally posted by Geoff H
Arta will give CSD plots. I'm still getting a grasp on interpreting them.

30 dB is well inside our usual dynamic range. How much would you pay for an amp with a 30dB s/n ratio? Vinyl approached 60dB.

Impulse tests should show a difference.

Point taken about the noise level, but keep in mind all of the materials exhibited the same noise level.

Impulse test to be posted shortly.
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Old 21st May 2007, 03:06 PM   #357
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As follows are the impuse charts for baltic birch and MDF. As can be seen, not a wild difference between the two. MDF has slightly higher peak amplitude within the first 12 ms, but quickly settles down. Decay time seems to be the same.
Note: Plot has been 1/6 octave smoothed.
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File Type: gif bb and mdf pulse.gif (24.6 KB, 606 views)
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Old 21st May 2007, 03:16 PM   #358
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Here is the pulse response for spruce, with an added bonus - pulse for the carpet lined BB box before I had to tear it all out to test the untreated panel.
Once again, spruce is looking pretty good, with overall lower amplitude than MDF, but with a sligtly longer decay time.
As can be seen, lining the panel with my carpet had next to no effect on amplitude or decay time. This was unexpected.
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Old 21st May 2007, 08:47 PM   #359
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Quote:
Originally posted by MJL21193
Barring the decay, Dave what are your opinions on my findings here?
FR doesn't tell us much. The impulse response should tell us more, but the results are hard to interpret.

Instead of smoothing, an average of a number of trials to reduce noise would give results that should remove some of the unknowns.

We also don't know how much of the impluse is panel & how much is speaker radiation wrapping around the panel.

dave
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Old 21st May 2007, 09:26 PM   #360
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Quote:
Originally posted by planet10


FR doesn't tell us much. The impulse response should tell us more, but the results are hard to interpret.

Instead of smoothing, an average of a number of trials to reduce noise would give results that should remove some of the unknowns.

We also don't know how much of the impluse is panel & how much is speaker radiation wrapping around the panel.

dave

How is that freq. response doesn't tell us much? It tells us what is available to be heard, and at what frequencies. The impulse results are what they are. My equipment, though not professional, is very accurate.
As for smoothing, it's necessary, as I am using a large sample size (132K) and there is in average - I have the repeat count set to 7. That's 7 times the sample rate averaged. I also ran the individual tests 3-4 times in a row to make sure the results are consistant.
Wrap around from the driver could be a possible influence, but as mentioned earlier, attempts to block it's output were of little impact. Mic placement for the panel impulse tests was less than 1/4" from the panel. Similar test for the driver at that distance and sound level would be off the scale of the chart.
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