Quote:
Originally Posted by A.Wayne
Hello rlacoste,
I disagree with the group delay statement when using a rear firing port, there is no real proximity effect and as such a sealed speakers is no more linear phase than a vented , If only discussing Front firing ports , agree ...
Regards,
|
You are rewriting the book on loudspeaker design…
Sealed box has 2nd order high pass behavior while vented box (
front or rear) has, at best, 3rd, but usually 4th order high pass behavior.
The group delay is a measure of the slope of the phase response at any given frequency. In any passive loudspeaker which is a minimum phase device, there is a unique relationship between amplitude and phase which allows for determination of phase from amplitude. Therefore phase response can be calculated from frequency response.
A group delay of a 3rd or 4th order system ( i.e. vented) is always larger then a 2nd order system ( i.e. sealed).
Read Dickason's "Loudspeaker Cookbook 7th edition" for a reference :
Page 31 –sealed box group delay simulation -
max GD 7.5ms
Page 64 –vented box group delay simulation -
max GD 40 ms (no less than 24)