I wasn't aware the TC9 doesn't have a shorting ring.
The TG9 is advertised to have a copper cap.
https://www.parts-express.com/Peerl...-Fiber-Cone-Full-Range-264-1064?quantity=2000
Anyway, the good thing about the FSAF test is that we can test and listen for ourselves:
TC9 vs TG9
from:
https://www.roomeqwizard.com/betahelp/help_en-GB/html/fsafmeasurement.html
"...REW's FSAF implementation can use noise (white, pink, brown) or a segment of a user-supplied file as the measurement signal,
allowing distortion results (TD+N) to be obtained when playing back music"
The file can be played back in the default player for WAV files by using the Play FSAF residual button in the Distortion graph controls. The Gain control allows the residual to be scaled up to help audibility, REW will automatically limit the gain applied to ensure the residual does not clip.
The file can be loaded as audio data by using the Load FSAF residual button in the Distortion graph controls."
@JohnPM or @mikets42
Is there a way to keep it for 30 days?
How is this residual computed?
For people like me who are not mathematically trained, please be gentle on the jargon.
I take I should be listening to it with good headphones?
I wonder whether I should start a new thread and post residuals for people to listen to. A FSAF residual test "which do you prefer"... and hide the drivers being tested...
PS.
I need to purchase a couple of SB12PFC as baseline...
The TG9 is advertised to have a copper cap.
https://www.parts-express.com/Peerl...-Fiber-Cone-Full-Range-264-1064?quantity=2000
Anyway, the good thing about the FSAF test is that we can test and listen for ourselves:
TC9 vs TG9
from:
https://www.roomeqwizard.com/betahelp/help_en-GB/html/fsafmeasurement.html
"...REW's FSAF implementation can use noise (white, pink, brown) or a segment of a user-supplied file as the measurement signal,
allowing distortion results (TD+N) to be obtained when playing back music"
...
File measurement residual
"When using a file as the test signal REW saves a copy of the measurement residual (the difference between the measured and linear response) as a WAV file (there are options to also save the excitation, mic input and LTI response as WAV files). The default location for those files is the temp sub-folder of the REW log files folder, whose location is shown in the About REW box. WAV files in the temp folder are deleted after 7 days. The folder location can be changed using the Set FSAF folder button in the Distortion graph controls. The residual files have names starting "res-" followed by the UUID of the measurement.The file can be played back in the default player for WAV files by using the Play FSAF residual button in the Distortion graph controls. The Gain control allows the residual to be scaled up to help audibility, REW will automatically limit the gain applied to ensure the residual does not clip.
The file can be loaded as audio data by using the Load FSAF residual button in the Distortion graph controls."
@JohnPM or @mikets42
Is there a way to keep it for 30 days?
How is this residual computed?
For people like me who are not mathematically trained, please be gentle on the jargon.
I take I should be listening to it with good headphones?
I wonder whether I should start a new thread and post residuals for people to listen to. A FSAF residual test "which do you prefer"... and hide the drivers being tested...
PS.
I need to purchase a couple of SB12PFC as baseline...
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D
Deleted member 375592
It may have some copper cap, but according to the impedance curve, it does not have much. The TG9 impedance curve:
(TC9 is similar but 2x) For most drivers, this blue curve is sloped down by half (p~=0.5...0.6), like for SB12PFC, so you can "see" the shorting ring:
The distortions in the midrange are steadily going down, which contradicts to the usual "up":
You are a step ahead of me. Having the same driver is what I wanted to suggest.
The loudspeaker produces sound. We record it with a mic. Let's separate the recording into undistorted sound and distortions.
So, let's take the source and filter it with RIR in the computer. Then we subtract the result of filtration from the mic. The result is called "residual". Ideally, it should be just microphone noise... but it is not. It also contains distortions. When we listen to the residual alone, we can better understand what was bothering us.
Now, if you understood it, how would you explain it back to me in your "layman's language"?
How do we compute that RIR for this source at that working point - do not even ask. Magic🙂
(TC9 is similar but 2x) For most drivers, this blue curve is sloped down by half (p~=0.5...0.6), like for SB12PFC, so you can "see" the shorting ring:
The distortions in the midrange are steadily going down, which contradicts to the usual "up":
You are a step ahead of me. Having the same driver is what I wanted to suggest.
The loudspeaker produces sound. We record it with a mic. Let's separate the recording into undistorted sound and distortions.
- "Undistorted" sound can still be different from the source. It may be altered by room reflection, speaker coloration, and other effects but it can be recovered to the ideal source by proper equalization. In math terms, "Undistorted" is related to the source by filtering with Room Impulse Response (RIR). Equalization is (to a degree) "unfilter" by "Inverse RIR".
- Distortions are what the loudspeaker adds from itself. They may be somehow related to the source, but not necessary. They can not be equalized. There is no simple math relation to the source.
So, let's take the source and filter it with RIR in the computer. Then we subtract the result of filtration from the mic. The result is called "residual". Ideally, it should be just microphone noise... but it is not. It also contains distortions. When we listen to the residual alone, we can better understand what was bothering us.
Now, if you understood it, how would you explain it back to me in your "layman's language"?
How do we compute that RIR for this source at that working point - do not even ask. Magic🙂
FSAF in REW, hmm, accessible enough, ktran perhaps a thread would be nice, not sure if people know any of this. Some useful data might start to accumulate.
I need to start doing these, no excuse to postpone 🙂 I remember mikets42 posting about this few years back and was amazed, unfortunately matlab is way beyond comfort zone.
First thing I'm gonna try is measure exactly on-axis and then bit off-axis and compare how much of a difference cone breakup peak has on the sound. Mid alone, then full speaker. Currently I feel on-axis is way too detectable to ear and would want the sound more even through the listening window and this knowledge ought to help whether it's mostly just directivity in general or also with this distortion stuff.
I need to start doing these, no excuse to postpone 🙂 I remember mikets42 posting about this few years back and was amazed, unfortunately matlab is way beyond comfort zone.
First thing I'm gonna try is measure exactly on-axis and then bit off-axis and compare how much of a difference cone breakup peak has on the sound. Mid alone, then full speaker. Currently I feel on-axis is way too detectable to ear and would want the sound more even through the listening window and this knowledge ought to help whether it's mostly just directivity in general or also with this distortion stuff.
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The distortions in the midrange are steadily going down, which contradicts to the usual "up":
More detail please.
The plot does not show driver input volts.
Is the microphone calibrated?
The plot does not show SPL, but only a relative level, dB.
Thanks DT
These are all 80dB/1m plots. We're all working hard to ensure we're testing as the same level (+/-1dB is almost acceptable, certainly +/-3 to 10dB is not)
D
Deleted member 375592
We do not care about volts. Matching Output SPL only. Mics must be calibrated. all is relative to the 80 dB (1kHz) SPL curve.
Oh yes we do care about amplifier output, call it Watts or Volt Amps.
No Volts, no Amps no Watts
Have you evaluated this new feature by any chance? Would be interesting to hear some feedback on this one...
//
D
Deleted member 375592
Both the TC9 and TG9 have copper caps. Here's a photo showing the pole piece of a TC9FD-18-08 that I accidentally blew up some years ago:
the mechanisms mentioned do not explain the particular odd harmonics distortion that often dominates the midrange and shows up in the current at voltage drive. the relative distortion scales very slowly with the level. This all fits when considering the hysteresis of the iron in the motor.
All models are wrong (too simple) and in this case the hysteresis is the missing component that explains what we observe.
Faraday rings can also increase distortion if not designed right. this is because the Le(x,f) is affected beyond reducing hysteresis distortion.
Except that is not a current-drive (with high impedance output). Box named "Controller" contains DSP processor, and the amplifier is conventional voltage-drive with low impedance output. Please read the paper carefully.
So, with that paper Klippel doesn't acknowledges that the voltage drive doesn't work.
Of course there are distortion mechanism yet to be discovered, and your work is truly worthwhile contribution to the science. But this thread morphed in to a "bashing Klipel" thing...
Crucial word here is "if not designed right". If designed right, Faraday rings lowers distortion.
This is interesting notion. On most graphs distortion goes up with frequency, but why is that? I tried to google but no explanations quickly.
Assuming ~flat acoustic frequency response of ideal driver was flat, either excursion or cone area needs to go down with increasing frequency, to reduce volume displacement to maintain flat response, right? So if cone area stays the same, as in ideal piston, excursion needs to go down with frequency, and the harmonics should go down as well assuming they are excursion related?
If it's good logic, then driver whose distortion goes up with frequency, the frequency response is kept flat by some other mechanism, like maintaining excursion to combat reducing cone area or something? So, distortion goes up with frequency when the frequency response is maintained ~flat with excursion to combat reducing Sd / cone breaking up? Or is it simply just that when driver response drops the noise floor rises in comparison?🙂
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VC-based drivers do not exist !
Obviously it is all about polishing a non existing turd. ;-)
Best regards
Bernd
D
Deleted member 375592
Do you know of any systematic academic studies of shorting rings? Something like: let's add N mm here, and measure the effects. I am concerned that there may be another effect hidden behind the shorting ring. Before Torricelli, people believed that the heavier an object is, the faster it falls, and everybody agreed,