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How to measure frequency response of a speaker at home

crabman.me

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Re: How to measure frequency response of a speaker at home

#11

Post by topato »

jareklupinski wrote: post #7
tetnis wrote: post #6

'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

personally I use Korn's "Freak on a Leash", lets me quickly know how low the driver can go

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.

Re: How to measure frequency response of a speaker at home

#12

Post by dietr1ch »

cluckindan wrote: post #3

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

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

Re: How to measure frequency response of a speaker at home

#13

Post by mattclarkdotnet »

cluckindan wrote: post #3

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

iPhone mics are consistent enough to be used for most purposes. Apple provides the correction curves and they are used by apps like Audiotools

Re: How to measure frequency response of a speaker at home

#14

Post by TacticalCoder »

> 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.

Re: How to measure frequency response of a speaker at home

#15

Post by willis936 »

dietr1ch wrote: post #12
cluckindan wrote: post #3

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

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

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.

Re: How to measure frequency response of a speaker at home

#16

Post by garyfirestorm »

cluckindan wrote: post #3

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

Not just that but the FRF calculation is slightly complex. You need to take into account windowing function, amplitude correction factor, sampling rate and block size of each measurement and %overlap… leakage is a very important thing in signal processing and spectral analysis. Also you need an anechoic environment to capture this, because you would be also capturing room reflections and characteristics of room acoustics.

Re: How to measure frequency response of a speaker at home

#17

Post by crazygringo »

cluckindan wrote: post #3

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

I've always wondered... is there some way to mathematically "solve" for this with multiple microphones and multiple speakers?

Like with 2 of each, or 3 of each, where you play the same waveform through every possible pair of speaker and microphone, you can solve some kind of system of matrix equations to determine the only possible combination of responsiveness at each device at each frequency?

Or do you just need a reference microphone with known characteristics, period, end of story, because math can't do it?

(Obviously from a practical perspective you want the reference microphone... I'm just curious about in theory.)

Re: How to measure frequency response of a speaker at home

#19

Post by hunter2_ »

crazygringo wrote: post #17
cluckindan wrote: post #3

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

I've always wondered... is there some way to mathematically "solve" for this with multiple microphones and multiple speakers? Like with 2 of each, or 3 of each, where you play the same waveform through every possible pair of speaker and microphone, you can solve some kind of system of matrix equations to determine the only possible combination of responsiveness at each device at each frequency? Or do you just need a…

I believe it's hardly different from trying to deduce perfect distances from multiple rulers of dubious precision: you need to compare them to one of extreme precision. Arranging 4 rulers into a perfect square proves that they have equal lengths, but you still don't know their offset from standard length.

However, if you ignore tolerances and assume that every microphone of a given model number has equal response, then it's simply a matter of having that known response information available, similar to a hypothetical brand of ruler being known for coming up short.

Re: How to measure frequency response of a speaker at home

#20

Post by jbay808 »

dietr1ch wrote: post #12
cluckindan wrote: post #3

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

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

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.
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