Impedance Curve

[jwatts]

I have managed to produce the impedance curve for a woofer in a vented box. Could someone please explain to me what the two peaks are in the plot and the frequencys they are located at.

 

[kelticwizard]

Richie00boy has a webpage which has the printout of small's Closed Box Papers and Neville Thiele's Vented box Papers available for downloading. The answer is to be found there.

Small's series of Vented Box papers will be appearing there soon.

http://www.richie00boy.pwp.blueyonder.co.uk/papers/index.htm

 

[jwatts]

I have been looking for those. Thanks for the help.

 

[kelticwizard]

I don't know how to tell you this, Jason, but I just leafed through both Thiele's and Small's papers on the vented box, and I did not find what the two impedance maxima each stand for. Perhaps an engineer, (which I am not), who can therefor understand most of the equations, (which I cannot), can find it in there.


But I know someone mentioned what the impedance maxima stood for. I'll try to dig up the post.

 

[kelticwizard]

Here we go. Knew I saw it on the board sometime.

The upper frequency impedance peak is the driver resonance in the box, will be different from the driver free air resonance.

The lower frequency impedance peak is the resonance of the port.

The impedance valley between them is the frequency the box-and-port combo ends up being tuned to, (not to be confused with the port resonance alone).

Starting with post # 18, all these things are explained better than I can:
http://www.diyaudio.com/forums/showthread.php?postid=76750#post76750