Phase response of bass reflex

[wonderfulaudio]

Hi,

How does the phase of the wave thru the port change as we supply a frequency sweep starting with low frequency where the port is not-loaded (no effect of port) and then thru the port tuning frequency and then higher up where the port becomes sealed?

Thanks,
WA

 

[David McBean]

Hornresp is your friend 🙂.

 

[wonderfulaudio]

Thanks David, is the port tuning at 90hz ?

 

[David McBean]

Hi wonderfulaudio,

You are close 🙂.

It is actually 95 Hz for the test example I used.

Kind regards,

David

 

[wonderfulaudio]

😕

The phase at 10hz is about -60 degrees. Now, 10Hz is over 3 octaves lower than the port tuning @95Hz. The port isnt doing anything there. So why -60degrees, I had expected 0. 😕
Can you pls explain?

 

[wonderfulaudio]

Also, what is the reference for this phase, is it the phase of electrical input to the driver? or is it the phase of front radiation of the driver?

 

[David McBean]

Hi wonderfulaudio,

The phase at 10hz is about -60 degrees. Now, 10Hz is over 3 octaves lower than the port tuning @95Hz. The port isnt doing anything there. So why -60degrees, I had expected 0. 😕
Can you pls explain?

At 10 Hz the port output is 68.5 dB. The phase will be zero degrees at zero Hz.

Also, what is the reference for this phase, is it the phase of electrical input to the driver? or is it the phase of front radiation of the driver?

The phase response chart shows the phase-angle difference in degrees between the input signal voltage and the port output sound pressure. In other words, the phase shift through the loudspeaker system.

Perhaps have a play with Hornresp yourself to better understand what is going on.

Kind regards,

David,

 

[wonderfulaudio]

Perhaps have a play with Hornresp yourself to better understand what is going on.

Thanks David, I will do that.

Can hornresp show the driver acoustic front spl/phase and port spl/phase separately (or overlaid)?

Thanks,
WA

 

[David McBean]

Hi WA,

Driver front SPL and port SPL can displayed separately, or overlaid using the Compare tool - similarly for phase.

The examples I posted showed just the port SPL and phase.

Kind regards,

David