Pearljam5000
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If the NFS can measure the M9
I trust it completely lol
I trust it completely lol
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GRIMM Audio LS1c & SB1 DSP Speaker Review
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Sure, it takes a mic/sensor that handles pressure.....very well known...old stuff Circa..2000
The door closing scenario Meyer said was screwing up their sensor tech, is anything but theory.
It was a pure observation..... of an unexpected consequence, of the grand marketing claims made above.
As said before, an acoustic pressure wave from the door closing passes by listener ears before it can be countered. And according to Meyer, gives is an unnatural sound from the servo control trying to maintain strict signal linearity. Best laid plans of mice and men.
Best to hear the door close, .... leave it alone...... and keep the the servo from responding to it.
Noise cancelling headphones are an entirely different animal, without relevance imo..
No noise reaches the ears first, to be cancelled later. Get's cancelled before it gets to the ears.
Noise suppression/countering is on just the noise. There's no servo control trying to maintain electrical signal linearity.
I can only be in one position at one time.
Keith
Pearljam5000
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But what if there are birds chirping in the background?One thing this thread has done for me....is totally reinforce my belief that the best sub measurements are still made out on an empty parking lot.!!
But what if there are birds chirping in the background?
Unless it's a T-rex bird it's probably fine.
kyuu
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The low resolution of that picture makes it hard to see what the frequency is where the error is passing 1% on the low end. Is it ~40Hz? And wouldn't the SNR be dependent on the speaker being tested? If it had more output down low, SNR and therefore accuracy should increase, right? So how relevant is the inaccuracy for speakers that have such weak output that low?
Geert
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Play louder
birds an other noise is uncorrelated and can be averaged away. An NFS takes hours so we can afford to average for quite some time.
kimmosto
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Yes, they mentioned that while purchasing VituixCAD. I guess they use NFS with "multi-way" method/module.
kimmosto
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Maybe because they were all designed without NFSWhy is Finland making so many good speakers?
Measuring in the living room is rudimentary, but doesn't prevent much...anything. There is also large anechoic at Aalto University but it's not always available for commercial projects. It had some weight limit, but I don't know is it limiting anymore.
But what if there are birds chirping in the background?
It makes absolutely zero practical difference !
Only matters is you're overly OCD about THD measurements. Birds chirping are so far out of a sub's passband, they are no problem. Lawnmowers, leaf blowers, air planes, cars, boat trains, a helicopter is the worst !..... yeah problems.
But only for THD again. Temporal averaging of pink, or long sine sweeps can help solve that. Or like I mainly do, just wait for a few moments of quiet to occur.
More than once, I've left a mic SPL calibrator on the ground plane mic being used when running a transfer function measurement....and with the dang calibrator playing its 94 dB 1kHz tone. This happens because I can measure speakers from indoors. Long ethernet runs allow network processing to amps and mics out by the subs. So I don't always see how I last left test setup.
Anyway....to my great surprise, there is very little difference in the transfer function whether the mic is set up proper and open, or with the dang calibrator on it and running !!!!
Even the SPL level is barely effected, if at all. Go figure...1kHz doesn't matter to a sub. (or at least any sub I'm willing to call a sub
)I would have thought the mic shielding by the calibrator around the mic capsule would matter....., but nope...the bass goes right through it without attenuation.
(My experience with speaker measurements, is we take things way too seriously, way too often.
)edit: the biggest problem of all imo, is wind. Totally messes the entire frequency range....and can't be averaged away
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Yes. The frequency axis starts at 40 Hz. I have attached a high res version of the slide as a zip file in post 755. The forum software automatically down-samples pictures to save storage.
[Edit] Here is the link to a slightly different presentation. The slide is slide 28 (but labeled 41).
https://www.klippel.de/fileadmin/us..._3D_Sound_Field_using_Near_Field_Scanning.pdf
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As said before ;-) the system is not only limited by the sensor, the actuator is limited too. Very low frequency, especially close to DC as a slammig door, remains a challenge. As long as people behave, a slamming door should be the extraordinary, though.
Good to know that you were not referring to sense and regulate at the listener's ears. Thank you.
That's the way I saw it too, but didn't really want to get involved in the discussion!
I will call BS on Meyer Sound on this one. Feedback output microsecond by microsecond? That means the control system sampling rate is in the order of 1 MHz.
This is from the lecture notes of the Feedback Control Systems class at MIT OCW 16.30 (lecture 20). When the sampling (update) rate of the digital control system is 15× the required system bandwidth, the impact of processing delay on performance becomes insignificant. That means, if the servo sub works to 200 Hz, a sampling rate of 3000 Hz is all it needs.
Feedback Control Systems | Aeronautics and Astronautics | MIT OpenCourseWare
This course will teach fundamentals of control design and analysis using state-space methods. This includes both the practical and theoretical aspects of the topic. By the end of the course, you should be able to design controllers using state-space methods and evaluate whether these controllers...
ocw.mit.edu
I will call BS on Meyer Sound on this one. Feedback output microsecond by microsecond? That means the control system sampling rate is in the order of 1 MHz.
This is from the lecture notes of the Feedback Control Systems class at MIT OCW 16.30 (lecture 20). When the sampling (update) rate of the digital control system is 15× the required system bandwidth, the impact of processing delay on performance becomes insignificant. That means, if the servo sub works to 200 Hz, a sampling rate of 3000 Hz is all it needs.
View attachment 455325Feedback Control Systems | Aeronautics and Astronautics | MIT OpenCourseWare
This course will teach fundamentals of control design and analysis using state-space methods. This includes both the practical and theoretical aspects of the topic. By the end of the course, you should be able to design controllers using state-space methods and evaluate whether these controllers...ocw.mit.edu
That has always been the Meyer modus operandi: a superficial appeal to engineering and evidence that falls apart with scrutiny. Ditto ATC, Harbeth.
Dark, cold, not much else to do?Why is Finland making so many good speakers?
Well, there were some ideas, but the government increased alcohol tax.Dark, cold, not much else to do?
Dark, cold, not much else to do?
Very expensive beer?
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