So if you spend way too long researching the 4430, as I have, you will find scattered comments from renowned people such as Zilch and others, here and on LH, commenting that the (net 5 cubic foot) 4430 cabinet is tuned to around 34 Hz, and that it would sound better (smoother, with more bass extension) tuned to around 29 Hz, perhaps by lengthening the ports. (Going lower than 29 Hz, perhaps by blocking one port, could be really hard on the woofers.) Rather than cutting down the ports, I started a thread here to explore ways of re-tuning the cabinets in a harmless, fully reversible way. In the process, one kind responder pointed me to a tuning calculator here and I spend some time exploring (and discussing on that thread) various options. After mulling it over for a long time, I first dramatically improved my bass response by hard-wiring the normally-switched crossover, as detailed in this thread here. Then yesterday, I went to Wal-Mart and bought for $10 (in the Kitchen and Bath department), one black Mainstays "Double Sink Cushioned Kitchen Mat" (item no. MS41-051-150-86) which is about 3/8" thick soft pebbled black foam vinyl, with tapered edges. After some experimentation I used a new box-cutter knife and a straight edge to cut four pieces, each about 9.5" long and 12" wide, and put one into each of the four port tubes, effectively reducing them from about 4 1/8" inches inner diameter to about 3 3/8" ID, and lengthening them to 9.5 inches. I got this number using the calculator above, for one straight edge and one flared edge on each port. With two straight edges I would have used a nine-inch port. With two flairs, ten inches. Happily, the rubber mat I'm using has one smooth side and one pebbled side, so I can see which one is quieter (a moot issue, I'm finding), and it has rounded factory edges, so I can use that edge for a flared end (see my photo above) or cut a straight edge for a straight end. I can also cut a piece short and mate it with other length pieces, in the middle of the factory port, to test different lengths and/or put a flared or straight edge on either or both ends. The result? The port liners make a huge difference, at least with test tones: Playing a 29 Hz test tone without the liners, the tone is almost completely inaudible. With the liners, it's clearly audible, and a dB meter shows about a 5 dB increase in output at that frequency, dropping below that and rising above. (I haven't used pink noise with an RTA - yet - to get a really clear picture.) I may monkey around a bit more to optimize the length, but I think it's already damn close. Playing music, I go from hearing about 10% of a certain super-low set of notes that I use as a reference (Tosca's Dehli, disc 2, track 1, at around 2:20, which seems to hover around 25 Hz), to hearing about 70% of it. For $10 and an hour or two of playing around, this seems to have been a very good experiment. Edit: JBL's own tuning specs for the woofer (5.64 diameter 11" port in 5CF box = 30 Hz) seem to validate the applicability of the tuning calculator I used above, which yields virtually the same numbers; see http://www.lansingheritage.org/images/jbl/specs/pro-comp/2235/page2.jpg. This sheet indicates an optimal tuning frequency of 30 Hz.