8 ms·

How to measure frequency response of a speaker at home

57 points by philip-b 2y ago

plussed_reader 2y ago
Sounds like they described a sub-par preamp on the wired input; something to the quality of BT compression. You can still tell that from the coloring of a local reference mic.
chevman 2y ago
Always hear my audiophile friends talking about this company/product: https://www.dirac.com/live/ https://www.dirac.com/live/
- DontchaKnowit 2y ago
  Shammy. You cannot truly correct for a room without actually changing the room itself.
  - turbojet1321 2y ago
    You don't have to "truly" correct for the room for EQ/calibration to be worthwhile - you just have to make it sound better than it did. I've used the built-in calibration in my WIIM Pro and it subjectively made a massive improvement. I used to be in-principle anti-EQ, but the AutoEQ project for headphones completely changed my opinion (though obviously headphones are far easier to EQ).
- zeroq 2y ago
  Also Room EQ (https://mathaudio.com/room-eq.htm https://mathaudio.com/room-eq.htm) and REW (https://www.roomeqwizard.com/ https://www.roomeqwizard.com/)
cluckindan 2y ago
You need a calibrated measurement microphone to do this for real. Otherwise the microphone’s frequency response will skew the results.
- jampekka 2y ago
  You can check whether responses differ without a calibrated microphone. But regardless here the methodology is very weak, just playing a sine sweep with a spectrum recorder open and eyeballing the frequency magnitudes.
- thr3000 2y ago
  Indeed, the article is very unsophisticated. Here are some relatively inexpensive measurement mics: https://roga-instruments.com/usb-measuring-microphone/ https://roga-instruments.com/usb-measuring-microphone/ Going the USB route sidesteps the separate DACs, which either add to the problem or run into the thousands.
- dietr1ch 2y ago
  And how do you calibrate a microphone? With a calibrated speaker? :P I'm guessing that there must be a way to either cancel out skews and work around this, but I guess it's just easier to start with a calibrated microphone
  - willis936 2y ago
    Generally you look up your microphone's magnitude response and enter it into whatever interface you have. For home audio receivers they have this hard coded for their included microphone. Also, generally microphones are sensitive to orientation, so to have repeatable results be sure to control that. Position in a room is also essential for repeatability.
  - jbay808 2y ago
    That's a great question! I have no idea. At low frequencies it should be very easy, because the sound is just a pressure measurement, so you can compare against a calibrated pressure reference. So the main challenge is measuring the high-frequency amplitude and phase response. If I had to do this, I'd probably set up a speaker in a long box with standing-wave resonance modes, and put both the microphone-under-test and a laser interferometer at an antinode to measure the change in refractive index that occurs with air pressure. A photodiode should have a flat frequency response out to well beyond 20 kHz, so that would do well as a calibration. But this is probably overkill for audible frequencies.
mandmandam 2y ago
> I eyeballed the two (red) plots and I think they look more or less identical. I overlaid those two images [0], and they seem significantly (though not hugely) different to me. Wouldn't speculate as to why that is though, without checking the consistency of passes with the same setup. 0 - https://imgur.com/a/7GUSmPW https://imgur.com/a/7GUSmPW (with hue shift for comparison)
- philip-b 2y ago
  This is useful, thanks. I should've done it on my own. And checking the consistency of passes would be a good idea too. If you don't mind, I'll update my blog post to include your overlaid image.
  - mandmandam 2y ago
    No worries.. I'd be interested to see the results of a multi pass consistency test.
tetnis 2y ago
'I tested different EQ presets on "Levitating" by Dua Lipa (Youtube Music, Music video on Youtube). The song is fantastic, and I've been listening to it on repeat these last few days' Stopped reading
- jareklupinski 2y ago
  personally I use Korn's "Freak on a Leash", lets me quickly know how low the driver can go
  - topato 2y ago
    Bone Thugs in Harmony "Tha Crossroads" has been my test track for many years. I think the many variences in the various male singing parts is excellent for calibration, as I rarely ever listen to bands with female singers. Plus, the backing track is quite variable as well.
- citruscomputing 2y ago
  can't forget > The music video is fantastic too and so, so beautiful except for the rap part which I don't like.
- sound1 2y ago
  same here :D
mattclarkdotnet 2y ago
To do this at home somewhat accurately, see this article 'How to make quasi-anechoic speaker measurements/spinoramas with REW and VituixCAD' https://audiosciencereview.com/forum/index.php?threads/how-to-make-quasi-anechoic-speaker-measurements-spinoramas-with-rew-and-vituixcad.21860/ https://audiosciencereview.com/forum/index.php?threads/how-t...
TacticalCoder 2y ago
> when Motion+ is connected to my phone via bluetooth, and when it's connected to my laptop via aux-in Why not for it's always interesting to experiment but one is lossy (all bluetooth codecs are lossy AFAIK) and the other is analog. Probably on top of an already lossy source too. They "sound" the same the same way a pixelized color print of Mona Lisa next to the real Mona Lisa looks identical if you're far enough. You may or may not be able to tell the difference but lossy Bluetooth and analog aux-in don't sound the same. I decided to go for a simple setup: a Yamaha fully integrated amp that does it all, including a network streamer. And I stream from Qobuz (lossless streaming) and from my own collection of CDs I ripped to FLAC (lossless and bit-perfect rips even though you're ripping from an audio CD, verified with an online DB of hashes from other people who did ripped the same CDs). So I know that up to amp, it's all lossless. Then the amp does its magic. It's simple really: even though I can't tell the difference between a pixelized color print of Mona Lisa and the real thing from far enough, I'd still prefer to know I'm actually looking at the real thing. A Qobuz (lossless) subscription doesn't cost more than a Spotify one (lossy although they announced they'd move to lossless IIRC). It's 2024: FLAC files are tiny compared to, say, even just a 1080p movie. Bandwith is plenty to stream lossless. Why even bother with lossy? Lossy audio is tech from a quarter of a century ago.
- Fripplebubby 2y ago
  > Why even bother with lossy? Lossy audio is tech from a quarter of a century ago. I know I'm rehashing the same argument that has been had around and around for decades but - because it often doesn't matter. In 2024 a 320Kbps or whatever high quality lossy source over a recent bluetooth codec into a Chinesium amp + DAC into a mid-range $500 pair of speakers sounds _awesome_ and the amount of time and money you spend going above that may be a fun hobby but it's really not worth the effort for most people.
softgrow 2y ago
Years ago at uni, one group chose as their control systems term project to take a known bad speaker (2 inch from transistor radio), measure its response, then build an inverse function to make it perfect using an analog computer. Don't know what the result was but they did have fun.
- mitthrowaway2 2y ago
  That will be tough because any attenuation will have to be cancelled by a gain, but the gain will amplify both noise and signal. So the end result might have the right spectral balance but be noisy in the frequency bands where the original signal was weak.
  - llamaz 2y ago
    It's a university project, so it wouldn't have been expected to be perfect. I had to do something similar as an assignment, but if I had the choice, I would have chosen anything else because the project was anything but fun. Everything was implemented using transistors, so it involved a lot of calculations, and simulation in LTSpice.
- fatnoah 2y ago
  Probably even more years ago at Uni, my senior project group built an automated analysis system for a large (literally large,club to stadium sized) speaker company. It was a very cool project that spanned multiple disciplines as we built a phased microphone array, a system to tilt and rotate the speaker, and programmable logic and software to generate and analyze signals. It was proof-of-concept quality, but was later made real and reduced analysis time from dozens of hours to about 45 minutes. Two of the project members were even hired by the company.
lanthade 2y ago
Oh my. I mean, if this guy is happy with his results then more power to him. However, this write up is a textbook case of the blind leading the blind. I don’t even know where to begin. The classic smiley faced EQ, equating spectograph with transfer function, no discussion of phase or any other time domain considerations. It reminds me of when I was 17 and thought I knew everything about computers. Then I went to college and learned how little it was that I actually knew. The author’s knowledge is me when I was 17. I however own thousands of dollars of measurement mics, audio interfaces, and software, and have experience built on decades of pro audio work using those tools and honing my craft. It’s not my desire to slam the author but it’s also important that people don’t take this correct methodology.
- aljgz 2y ago
  `When disagreeing, please reply to the argument instead of calling names. "That is idiotic; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3".` `Please don't fulminate. Please don't sneer, including at the rest of the community.` As a curious person with a degree in Electrical Engineering, and one in Computer Science, very interested in quality audio, etc, I know what you mean. But please, don't be the person who kills curiousity. This person was curious, did some experiments, and posted the result. If you have time, write some of the major ways that such a measurement is inadequate. If not, link to some resources. `Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something.`
  - lanthade 2y ago
    I find it interesting that you chose to respond to my comment like this as opposed to others which are more egregious on the issues you bring up. That aside though, I did mention a number of issues with the write up. Anyone interested is welcome to dig into them and come back with questions if they desire. This is not however an introductory level topic and I elected to not try to thumb tap out a distillation of a very advanced and multi-faceted topic here. I would not expect someone with graduate level qualifications and years of experience in software development to try to distill their work down to my level either.
IAmGraydon 2y ago
>I eyeballed the two (red) plots and I think they look more or less identical. So I guess there is actually no difference in sound and I just imagined it. LOL. Why is this even on the front page? He measured it with a phone's mic, then he goes on to "eyeball" the results, which are clearly different even to the eye. He then declares them the same. From top to bottom, everything is wrong with this.
harrall 2y ago
I own a Soundcore Motion+ and can attest to it to be terribly sounding, even for a Bluetooth speaker.
amelius 2y ago
This assumes your amp and speaker are linear systems.
- wl 2y ago
  Linearity is an excellent assumption for virtually any non-overdriven modern amplifier. THD measurements make sense for speakers, but that's not getting in the way of what the author is attempting to do here. I don't even know where to begin addressing everything that's wrong with this article, but assuming linearity isn't one of those errors.
zkd43 2y ago
I just want to point out that it's a pretty big leap to go from "I observed the same frequency response curve with two different inputs" to "there is no audible difference between the two inputs". There are many other measurements you would need to take to prove or disprove the hypothesis, such as signal to noise ratio and dynamic range. And even then you couldn't really prove it definitively due to the complexity of how humans interpret the sound. When you use Bluetooth, your speaker is functioning as the DAC (digital to analog converter), but when you use the aux, your computer is functioning as the DAC and also amplifying the signal, so it's reasonable to expect them to sound different.
- parpfish 2y ago
  are there any established speaker metrics that would get at something like "reconstruction error"? i've seen total harmonic distortion (THD) published in some spec sheets, but i'm not clear if there's a standard method for how that gets calculated or if it's just marketing hype. moreover, i'm not sure if/how something like THD relates to accuracy of reconstructing more complex naturalistic (i.e., non-sine wave) signals.
- philip-b 2y ago
  Do different DACs frequently sound different? I would expect that it's audiophile's fairy tales.
FuriouslyAdrift 2y ago
Calibrated mic (https://www.minidsp.com/products/acoustic-measurement/umik-2 https://www.minidsp.com/products/acoustic-measurement/umik-2) and Room EQ Wizard (https://www.roomeqwizard.com/help/help_en-GB/html/makingmeasurements.html#top https://www.roomeqwizard.com/help/help_en-GB/html/makingmeas...)

57 points by philip-b 2y ago

Sounds like they described a sub-par preamp on the wired input; something to the quality of BT compression. You can still tell that from the coloring of a local reference mic.

chevman 2y ago

Always hear my audiophile friends talking about this company/product: https://www.dirac.com/live/ https://www.dirac.com/live/

DontchaKnowit 2y ago
Shammy. You cannot truly correct for a room without actually changing the room itself.
- turbojet1321 2y ago
  You don't have to "truly" correct for the room for EQ/calibration to be worthwhile - you just have to make it sound better than it did. I've used the built-in calibration in my WIIM Pro and it subjectively made a massive improvement. I used to be in-principle anti-EQ, but the AutoEQ project for headphones completely changed my opinion (though obviously headphones are far easier to EQ).
zeroq 2y ago
Also Room EQ (https://mathaudio.com/room-eq.htm https://mathaudio.com/room-eq.htm) and REW (https://www.roomeqwizard.com/ https://www.roomeqwizard.com/)

cluckindan 2y ago

You need a calibrated measurement microphone to do this for real. Otherwise the microphone’s frequency response will skew the results.

jampekka 2y ago
You can check whether responses differ without a calibrated microphone. But regardless here the methodology is very weak, just playing a sine sweep with a spectrum recorder open and eyeballing the frequency magnitudes.
thr3000 2y ago
Indeed, the article is very unsophisticated. Here are some relatively inexpensive measurement mics: https://roga-instruments.com/usb-measuring-microphone/ https://roga-instruments.com/usb-measuring-microphone/ Going the USB route sidesteps the separate DACs, which either add to the problem or run into the thousands.
dietr1ch 2y ago
And how do you calibrate a microphone? With a calibrated speaker? :P I'm guessing that there must be a way to either cancel out skews and work around this, but I guess it's just easier to start with a calibrated microphone
- willis936 2y ago
  Generally you look up your microphone's magnitude response and enter it into whatever interface you have. For home audio receivers they have this hard coded for their included microphone. Also, generally microphones are sensitive to orientation, so to have repeatable results be sure to control that. Position in a room is also essential for repeatability.
- jbay808 2y ago
  That's a great question! I have no idea. At low frequencies it should be very easy, because the sound is just a pressure measurement, so you can compare against a calibrated pressure reference. So the main challenge is measuring the high-frequency amplitude and phase response. If I had to do this, I'd probably set up a speaker in a long box with standing-wave resonance modes, and put both the microphone-under-test and a laser interferometer at an antinode to measure the change in refractive index that occurs with air pressure. A photodiode should have a flat frequency response out to well beyond 20 kHz, so that would do well as a calibration. But this is probably overkill for audible frequencies.

mandmandam 2y ago

> I eyeballed the two (red) plots and I think they look more or less identical. I overlaid those two images [0], and they seem significantly (though not hugely) different to me. Wouldn't speculate as to why that is though, without checking the consistency of passes with the same setup. 0 - https://imgur.com/a/7GUSmPW https://imgur.com/a/7GUSmPW (with hue shift for comparison)

philip-b 2y ago
This is useful, thanks. I should've done it on my own. And checking the consistency of passes would be a good idea too. If you don't mind, I'll update my blog post to include your overlaid image.
- mandmandam 2y ago
  No worries.. I'd be interested to see the results of a multi pass consistency test.

tetnis 2y ago

'I tested different EQ presets on "Levitating" by Dua Lipa (Youtube Music, Music video on Youtube). The song is fantastic, and I've been listening to it on repeat these last few days' Stopped reading

jareklupinski 2y ago
personally I use Korn's "Freak on a Leash", lets me quickly know how low the driver can go
- topato 2y ago
  Bone Thugs in Harmony "Tha Crossroads" has been my test track for many years. I think the many variences in the various male singing parts is excellent for calibration, as I rarely ever listen to bands with female singers. Plus, the backing track is quite variable as well.
citruscomputing 2y ago
can't forget > The music video is fantastic too and so, so beautiful except for the rap part which I don't like.
sound1 2y ago
same here :D

mattclarkdotnet 2y ago

To do this at home somewhat accurately, see this article 'How to make quasi-anechoic speaker measurements/spinoramas with REW and VituixCAD' https://audiosciencereview.com/forum/index.php?threads/how-to-make-quasi-anechoic-speaker-measurements-spinoramas-with-rew-and-vituixcad.21860/ https://audiosciencereview.com/forum/index.php?threads/how-t...

TacticalCoder 2y ago

> when Motion+ is connected to my phone via bluetooth, and when it's connected to my laptop via aux-in Why not for it's always interesting to experiment but one is lossy (all bluetooth codecs are lossy AFAIK) and the other is analog. Probably on top of an already lossy source too. They "sound" the same the same way a pixelized color print of Mona Lisa next to the real Mona Lisa looks identical if you're far enough. You may or may not be able to tell the difference but lossy Bluetooth and analog aux-in don't sound the same. I decided to go for a simple setup: a Yamaha fully integrated amp that does it all, including a network streamer. And I stream from Qobuz (lossless streaming) and from my own collection of CDs I ripped to FLAC (lossless and bit-perfect rips even though you're ripping from an audio CD, verified with an online DB of hashes from other people who did ripped the same CDs). So I know that up to amp, it's all lossless. Then the amp does its magic. It's simple really: even though I can't tell the difference between a pixelized color print of Mona Lisa and the real thing from far enough, I'd still prefer to know I'm actually looking at the real thing. A Qobuz (lossless) subscription doesn't cost more than a Spotify one (lossy although they announced they'd move to lossless IIRC). It's 2024: FLAC files are tiny compared to, say, even just a 1080p movie. Bandwith is plenty to stream lossless. Why even bother with lossy? Lossy audio is tech from a quarter of a century ago.

Fripplebubby 2y ago
> Why even bother with lossy? Lossy audio is tech from a quarter of a century ago. I know I'm rehashing the same argument that has been had around and around for decades but - because it often doesn't matter. In 2024 a 320Kbps or whatever high quality lossy source over a recent bluetooth codec into a Chinesium amp + DAC into a mid-range $500 pair of speakers sounds _awesome_ and the amount of time and money you spend going above that may be a fun hobby but it's really not worth the effort for most people.

softgrow 2y ago

Years ago at uni, one group chose as their control systems term project to take a known bad speaker (2 inch from transistor radio), measure its response, then build an inverse function to make it perfect using an analog computer. Don't know what the result was but they did have fun.

mitthrowaway2 2y ago
That will be tough because any attenuation will have to be cancelled by a gain, but the gain will amplify both noise and signal. So the end result might have the right spectral balance but be noisy in the frequency bands where the original signal was weak.
- llamaz 2y ago
  It's a university project, so it wouldn't have been expected to be perfect. I had to do something similar as an assignment, but if I had the choice, I would have chosen anything else because the project was anything but fun. Everything was implemented using transistors, so it involved a lot of calculations, and simulation in LTSpice.
fatnoah 2y ago
Probably even more years ago at Uni, my senior project group built an automated analysis system for a large (literally large,club to stadium sized) speaker company. It was a very cool project that spanned multiple disciplines as we built a phased microphone array, a system to tilt and rotate the speaker, and programmable logic and software to generate and analyze signals. It was proof-of-concept quality, but was later made real and reduced analysis time from dozens of hours to about 45 minutes. Two of the project members were even hired by the company.

lanthade 2y ago

Oh my. I mean, if this guy is happy with his results then more power to him. However, this write up is a textbook case of the blind leading the blind. I don’t even know where to begin. The classic smiley faced EQ, equating spectograph with transfer function, no discussion of phase or any other time domain considerations. It reminds me of when I was 17 and thought I knew everything about computers. Then I went to college and learned how little it was that I actually knew. The author’s knowledge is me when I was 17. I however own thousands of dollars of measurement mics, audio interfaces, and software, and have experience built on decades of pro audio work using those tools and honing my craft. It’s not my desire to slam the author but it’s also important that people don’t take this correct methodology.

aljgz 2y ago
`When disagreeing, please reply to the argument instead of calling names. "That is idiotic; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3".` `Please don't fulminate. Please don't sneer, including at the rest of the community.` As a curious person with a degree in Electrical Engineering, and one in Computer Science, very interested in quality audio, etc, I know what you mean. But please, don't be the person who kills curiousity. This person was curious, did some experiments, and posted the result. If you have time, write some of the major ways that such a measurement is inadequate. If not, link to some resources. `Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something.`
- lanthade 2y ago
  I find it interesting that you chose to respond to my comment like this as opposed to others which are more egregious on the issues you bring up. That aside though, I did mention a number of issues with the write up. Anyone interested is welcome to dig into them and come back with questions if they desire. This is not however an introductory level topic and I elected to not try to thumb tap out a distillation of a very advanced and multi-faceted topic here. I would not expect someone with graduate level qualifications and years of experience in software development to try to distill their work down to my level either.

IAmGraydon 2y ago

>I eyeballed the two (red) plots and I think they look more or less identical. So I guess there is actually no difference in sound and I just imagined it. LOL. Why is this even on the front page? He measured it with a phone's mic, then he goes on to "eyeball" the results, which are clearly different even to the eye. He then declares them the same. From top to bottom, everything is wrong with this.

harrall 2y ago

I own a Soundcore Motion+ and can attest to it to be terribly sounding, even for a Bluetooth speaker.

amelius 2y ago

This assumes your amp and speaker are linear systems.

wl 2y ago
Linearity is an excellent assumption for virtually any non-overdriven modern amplifier. THD measurements make sense for speakers, but that's not getting in the way of what the author is attempting to do here. I don't even know where to begin addressing everything that's wrong with this article, but assuming linearity isn't one of those errors.

zkd43 2y ago

I just want to point out that it's a pretty big leap to go from "I observed the same frequency response curve with two different inputs" to "there is no audible difference between the two inputs". There are many other measurements you would need to take to prove or disprove the hypothesis, such as signal to noise ratio and dynamic range. And even then you couldn't really prove it definitively due to the complexity of how humans interpret the sound. When you use Bluetooth, your speaker is functioning as the DAC (digital to analog converter), but when you use the aux, your computer is functioning as the DAC and also amplifying the signal, so it's reasonable to expect them to sound different.

parpfish 2y ago
are there any established speaker metrics that would get at something like "reconstruction error"? i've seen total harmonic distortion (THD) published in some spec sheets, but i'm not clear if there's a standard method for how that gets calculated or if it's just marketing hype. moreover, i'm not sure if/how something like THD relates to accuracy of reconstructing more complex naturalistic (i.e., non-sine wave) signals.
philip-b 2y ago
Do different DACs frequently sound different? I would expect that it's audiophile's fairy tales.

FuriouslyAdrift 2y ago

Calibrated mic (https://www.minidsp.com/products/acoustic-measurement/umik-2 https://www.minidsp.com/products/acoustic-measurement/umik-2) and Room EQ Wizard (https://www.roomeqwizard.com/help/help_en-GB/html/makingmeasurements.html#top https://www.roomeqwizard.com/help/help_en-GB/html/makingmeas...)