WinISD: Qtc no longer shown?

I'm designing a ported bookshelf speaker and I'm considering the Seas CA15RLY for the midbass. Using WinISD I modelled the three default alignments (QB3, BB4, and C4). All result in a box of around 7.5 liters and with similar F3 points. I'd like to get a bit better low-end extension, so I increased the box size to 12 liters and lowered the tuning frequency to 48Hz to arrive at a nice flat response until rolloff. This results in an F3 about 10Hz lower.

This will ofcourse increase Qtc, and impact bass transients negatively. But I have no idea by how much. I googled screenshots of older versions of WinISD and the Qtc used to be shown on the 'box' tab, but it isn't there anymore (I'm on version Can I still find Qtc in WinISD somewhere? Or is there another program that can be used to calculate Qtc given the driver T/S parameters and a certain BR cabinet?

Qtc is not really a property of bass reflex, it's a closed box parameter. Change enclosure type to closed box in WinISD and you will find Qtc in the box tab. You might find transfer function and group delay to be more useful information anyway. For more modern cabinet modelling software, give VituixCAD a try.
  • Like
Reactions: 1 users