Originally Posted by HMenke
I'm looking for advice from experienced subwoofer builders on the best design software to use. Adire LspCAD looks excellent but it looks like it only works with their brand of woofers and the selection of their woofers is limited to one type per size. Am I right about that?
I am interested in building a Sonotube with 15" woofer tuned to less than 20 Hz (if that is possible).
Also I am curious how important it is to calculate exact internal volume (subtracting for volume occupied by vent tube etc.)
I am not "experienced" but currently in process of doing a DIY subwoofer project. Both WinISD Pro and UniBox are free. (Google is your friend). UniBox does require Microsoft Excel but I am finding it "apparently" more useful and it seems to be somewhat better regarded over at htguide. I do like the high pass (rumble)filter modeling in WinISD Pro which is useful for trying to avoid exceeding the driver's Xmax or Xmech down below the tuning point.
Sure it is possible and practical to do a vented sonotube using a 15" driver with below 20 Hz tuning. I think most of the experienced builders would tell you to use a 6" min dia port to avoid port noise/distortion. Some of us are concerned with the resultant port resonance getting too low for the long port length that results. (This leads me to try a ~ 230 L box with dual 18" passive radiators using a 15" driver --- $300 more expensive).
The resulting internal box volume is important for determining the tuning (port dimensions) so yes, you have to subtract the port volume (entire cylinder), the driver volume, braces, internal plate amp (if used), etc.