Unibox High-Pass Filter

[69stingray]

Is there a way to add a high-pass filter in Unibox? I see you can add a low-pass, but I want to add a high-pass to my woofer to limit the excursion at low-freq (and hopefully increase power handling).

[CharlieLaub]

I do this all the time when designing filter assisted vented alignments. Unfortunately you cannot do this directly in Unibox. Instead I use Jeff Bagby's Box and Circuit Designer to design the filter and then I import it in to Unibox. Box and Circuit Designer can be downloaded at:
http://www.pvconsultants.com/audio/eq/boxcircuit.htm
If you go to that link you will see an example screen shot. The right hand side of the image shows the various options for HP and LP filters, a parametric equalizer and a Linkwitz Transform circuit. It might be useful to refer to that image while I go over step 1.

Step #1 - create the filter in Box and Circuit Designer:
First, disable everything in the filter section except what you will need. You will need to set and then load "No Low Pass" in the section "Textbook Low Pass Filter" (unless you want to include one). Then go to "Two stage High Pass Filter" and set up the HP section you desire. To get a Butterworth Fourth order filter, set the Q of section 1 to 0.541 and the Q of section 2 to 1.31. Fourth Order Bessel Q1=0.521 and Q2=0.805. Second order Butterworth filter has Q1= 0.707 and second order Bessel has Q1=0.577. You can also choose other Q values if you would like and preview the response in the plot called "Electrical Circuit Transfer Function". Once you have the configuration that you want, click on the button "Save Electrical Filter to FRD". This will open a Save As dialog box where you can enter a path and file name.

Step #2 - import this FRD filter file into Unibox:
Open or restore Unibox. On the Speaker Design tab, near the top just above the Closed Box response curve you will see a section called "Frequency Response Correction Filter". Click on the FRD button and you will be prompted in an "Open File" windoze dialog box for the folder and file name. Choose the file you created in Box and Circuit Designer. Then enable this filter by checking the box "Activate External Active Filter" just below the FRD button. You will need to recalculate your Unibox model at this point.

Voila, you now have a Unibox model with an active HP filter. While you need to have two applications open and go back and forth a bit it's not too hard to use Unibox and Box and Circuit Designer together in this way.

Any questions, just PM me.

Charlie

[69stingray]

Thanks Charlie, I will have to look into that, I will let you know if I have any problems.