I got to tinker and experiment with the sealed subwoofer with acoustic egg crate foam inside.
Since my sealed subwoofer enclosure is comprised of a separate 4-chamber (one for each sub driver @1.5cu.ft. each), I was only able to fill up 2 chambers with acoustic foam, so it means only half of the whole enclosure is stuffed. The subwoofer set is bi-amped (1 amp for the 2 left pieces, and 1 identical amp for the 2 right pieces), so I was able to do an A-B test if there are any differences in the bass output/quality (left drivers vs right drivers).
NOTES:1. The sub drivers are meant and designed for HT (slam and SPL), so SQ is not of top priority here (although distortion must of course be kept to a minimum). For me, I find these 12" drivers a bit slow and not too musical for SQ music (compared to expensive subs), but it is very good for HT, even for very low frequencies, kayang kaya niya, it is really hard to bottom-out.
2. For the experiment, the bass range is from 0hz-150hz, but next time it will be high passed from 50hz-150hz (upper/mid bass duties).
3. Each driver is 350w RMS rated, but I think the amp is a bit underpowered for them. Estimate ko is 250w RMS lang ang actual for each sub real-time.
TEST MATERIALS1. Fast Five (starting scene where bus tumbles and then title screen booms)
2. Man of Steel (Fighting scene with main villain near the end)
3. MI: 4 (Scene where bomb explodes near the Russian Kremlin I think)
4. Master and Commander (Ship fight scene) - nawawala copy ko :p
5. You can recommend me a movie action scene and I'll try it out
OBSERVATIONSDoing an A-B testing (over and over), reveals not much difference between A and B enclosures, it's really hard to distinguish between the two sides for HT bass heavy scenes since you are focused on the action and not for any SQ.
Please note that the acoustic foam is only 2" thick, so it may not be sufficient to absorb the lowest frequencies at that thickness. I wonder if there is any difference if I will make it 4" or 6" thick? That would be another experiment
Also, if I line the whole enclosure literally with acoustic foam and no fiberfill? Although that may also change the internal displacement too much.
SIDE EXPERIMENTFinished on doing HT tests, I decided to just try out some SQ music to see if there are any differences on more "subtle" bass duties. Although I don't consider these sub drivers as "musical", I just did it anyway out of curiosity.
Playing Jennifer Warnes - Way down deep, I did notice a slight difference in bass quality from A and B.
When I was about 1-2 feet away from the drivers, I noticed that side B (with the acoustic foam) had slightly less distortion/vibration from the driver cones, probably due to the back waves being "more" absorbed/diffused than the the other side (A) without acoustic foam. But of course it is not a night-and-day difference, you really have to hear it or listen critically to distinguish the two (A-B). But yes, there is a slight improvement, although just a little (but every little step matters right hehe).
VERDICTAlthough there are too many factors to consider (that I haven't done yet), putting 2" acoustic foam inside the enclosure (sealed) reveals little/negligible improvement for HT SPL/slam duties, but MAY have a slight improvement when used for subtle SQ music bass duties, wherein distortion must be kept at a minimum.
For now, I'll remove the acoustic foam from my sub enclosure and put it somewhere else more useful, like my Monitor Audio speaker and BG full towers, soon