In theory and regardless of other driver specs, the ideal air mass load compliance [Vb] should be one that raises the driver's Fs by 1.56x, which equates to measured Vas/1.44 or ~156 L using published Vas, though others are saying it's because T/S design theory says the box compliance can't protect the driver even though it takes ~209 L for a T/S max flat 0.707 Qtc alignment whereas the pioneers added some form of damping to reduce box Q if too high.
If going sealed, then the ~156 L can handle ~120 W peak/~21-27 Hz BW whereas the ~209 L can only handle ~100 W peak and while it does in theory go lower, it's too little for humans to tell the difference even with massive room gain.
GM
Your room is a little bigger than mine and I run a stereo pair of dual 15" corner loaded ~14 Hz ~20 ft^3 ML-TQWT [vented tapered pipe horns] that I DIYed in '69 originally tuned to ~35 Hz, so until fairly recently wouldn't recommend sealed, but nowadays a pair of vented Ultimax will in theory out perform them by quite a bit due to the huge power handling increases in recent years and after recently being exposed to affordable ~SOTA DSP, now have an attitude of putting these powerful drivers in acoustically optimum sealed boxes and use DSP to optimize/integrate box alignments in room, which probably will wind up with different box alignments between channels.
In ~short, if wanting max LF output down to tuning and have no need for single digit output, I prefer vented, otherwise sealed with DSP, especially as the room corner frequency rises [~565 ft/~172.2 m/longest room dim.], so ~172.2/6 = ~28.7 Hz where your room gain theoretically begins in earnest or ~the -3 dB point of the ~156 L/0.75 Qtc sealed I suggested. On paper, a pretty good match-up IME IF your room doesn't have high losses due to open doorways or similar.
GM
In ~short, if wanting max LF output down to tuning and have no need for single digit output, I prefer vented, otherwise sealed with DSP, especially as the room corner frequency rises [~565 ft/~172.2 m/longest room dim.], so ~172.2/6 = ~28.7 Hz where your room gain theoretically begins in earnest or ~the -3 dB point of the ~156 L/0.75 Qtc sealed I suggested. On paper, a pretty good match-up IME IF your room doesn't have high losses due to open doorways or similar.
GM
If you play around in Subwoofer box calculator, Sub box calculator you can easily see what sealed vs ported or with sealed what varying volume sizes does. Make sure you keep an eye on Xmax and delay responses. The 3D box design feature is cool and the cut out feature useful.
Your idea of placing both subs at the front in stereo is great for music stereo imaging but bad for even output.
Attachments
I'd definitely build a sealed box for an 18" in that size room, unless you really are a nutter who wants to be able to drop light fittings at a moment's notice.
Chris
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.