Amplitude and Frequency Together Equal - Loudness Contours

[Richx200]

I have been trying to figure out why, if hearing uniform levels of all frequencies within hearing isn't part of calibrating speakers. Low frequencies are quieter than mid or high yet their levels (SPL) aren't increased, so all frequencies have the same loudness. Wouldn't it be easier to use an SPL meter, equalizer and a set of frequencies test bands to level out the room? Wouldn't that be the essence of a flat frequency response?

I have used ARC to closely flatten a response and then tested the speakers with recorded test bands (20 - 20khz) only to see different SPL levels at different frequency bands.

 

[staticV3]

Wouldn't it be easier to use an SPL meter, equalizer and a set of frequencies test bands to level out the room?

An SPL meter, (presumably Graphic) Equalizer, and a set of test frequencies is just a less precise, inferior version of something like REW+UMIK-1.

Sure you can use it to (try to) correct your system, but it's 2024 now and we have better tools at our disposal.

Flat frequency response in-room is usually a bad idea: https://youtu.be/_tnWB8Rl0Ms

We want our speakers to be anechoically flat (sans a slight bass shelf perhaps), the room then tilts the response slightly warm.

The way I see it, equal loudness contours should never be used as direct frequency response targets.

At most, we should apply the Delta between equal loudness contours at different SPLs as a modifier to our anechoically flat system.

Equal loudness contours basically tell us how our hearing changes with varying SPLs, and applying the inverse of that to our system response can remove tonal imbalance.

Bass becomes harder to hear the quieter you play? No problem, just boost it slightly when volume is decreased.

Treble becomes more obvious as you increase volume? No problem, just reduce it a bit as volume is turned up, so that it doesn't become annoying.

That's pretty much what Receivers, Bluetooth speakers etc. are doing.

 

[DVDdoug]

Equal loudness curves are human perception. They don't show-up in measurements. ...It's "built-into" instruments & music so the music should sound right when played-back (approximately) flat and at the correct volume.

SPL meters are usually A-weighted so high & low frequencies "read" lower than mid-frequencies (very-roughly approximating human hearing) but they are linear so a 10-dB change at 20Hz is a 10dB change, no matter where you start. Even without weighting SPL meters usually aren't flat-enough for measuring frequency response.

Measurement microphones are not weighted. They are (software) calibrated to be flat.

 

[Richx200]

An SPL meter, (presumably Graphic) Equalizer, and a set of test frequencies is just a less precise, inferior version of something like REW+UMIK-1.

Sure you can use it to (try to) correct your system, but it's 2024 now and we have better tools at our disposal.

Flat frequency response in-room is usually a bad idea: https://youtu.be/_tnWB8Rl0Ms

We want our speakers to be anechoically flat (sans a slight bass shelf perhaps), the room then tilts the response slightly warm.

The way I see it, equal loudness contours should never be used as direct frequency response targets.

At most, we should apply the Delta between equal loudness contours at different SPLs as a modifier to our anechoically flat system.

Equal loudness contours basically tell us how our hearing changes with varying SPLs, and applying the inverse of that to our system response can remove tonal imbalance.

Bass becomes harder to hear the quieter you play? No problem, just boost it slightly when volume is decreased.

Treble becomes more obvious as you increase volume? No problem, just reduce it a bit as volume is turned up, so that it doesn't become annoying.

That's pretty much what Receivers, Bluetooth speakers etc. are doing.

Thank you one more question. I know there is a relationship between SPL, dB, and Phons just not sure how it works.