Acoustic Measurements: Understanding Time and Frequency

[Pio2001]

By correcting actual phase response you can get it close to minimum phase so that excess phase is close to zero over the entire frequency range.

That makes more sense than correcting phase itself

 

[QMuse]

Very nice, can you do group delay the same way?

Sure. This is corresponding GD from LP:

And this from 80cm:

 

[QMuse]

That makes more sense than correcting phase itself

You are correcting the phase itself but your target is to have excess phase as close to 0 over the frequency range with smooth phase response to reduce GD. I have compared my results with filters created by Acurate and Audiolense and they do exactly the same thing.

 

[QMuse]

Btw, I have read more than a few times that transmission line designs suffer from "smeared" bass because of the phase issues due to phase being inverted in the transmission lines and then addind incorrectly with the signal coming from woofers. As you can see from the uncorrected phase response and corresponding GD this is not true, at least not for my speakers (Castle Harlech S2). In fact, they have one of the cleanest bass I have ever heard. Looking at the THD distortion graph measured from 1m distance when speaker was at the middle of the room with a single 40Hz tone you can see that THD is only 0.43% at 90dB SPL.

Phase fluctuations and corresponding spikes in GD graph at 130Hz and 220Hz are due to the positioning of the speaker.