This is right from SVS's website under "Questions".
4) What's best for me? Cylinder or Box SVS subwoofer?
Like so many things in life... it depends. Some folks like the cutting-edge, unique and understated elegance of our space-saving cylinder subwoofers, others value the more traditional but likewise slick simplicity of our box designs. In fact, aesthetics ... how you want your sub to look ... is probably the most significant consideration in your decision here. Still, there are some other "pro's and con's" to consider, and even the question of "looks" isn't as straightforward as it might seem at first. How you weigh these issues is clearly a personal call:
In short, cylinders tend to cost less, are noticeably taller, but at the same time lighter and easier to move. They take up far less precious floor space too. Boxes tend to have considerably more "heft" (requiring more "grunt" to place them; most require two people to move very far), have nice flat tops you can put things on, yet cost a bit more than the closest performing cylinder equivalent. Want further discussion on this eternal question??? Read on.
Cylinder Subwoofers:
The original SVS subwoofer designs were all cylinder-based for some very good reasons. First and foremost it's a very efficient audio enclosure from a number of perspectives. The internal pressures of a subwoofer of this class can be intense! Ever wonder why cylinders are used to contain compressed gasses? They can't stretch easily, and tend to resist forms of wall distortion that boxes must combat. In short, a box wall must be many times thicker and heavier to equal the strength of a simple cylinder. This affects several things in turn...
Weight: For a equal level of performance and enclosure space (the key to getting deep and powerfully clean bass) a cylinder will be lighter, and that means easier to move around your room, or from house to house as you go through life. One example. Our PB12-NSD weighs in around 75 pounds. The smallest powered cylinder, the 20-39 PCi is virtually a sonic clone in performance, but weighs nearly 20 pounds less. Now, 20 pounds might not sound like much, until you haul one up to the top floor of a dorm room, or nudge one into a tight spot in a basement. Most our cylinders you can sling on your shoulder, most our box subs are decidedly "two-person lift" entities. Of course we know that for some customers weight is good, it connotes quality and value. If you fall into this camp, then the relative light weight of a PCi isn't an advantage. In practical terms most folks will find 55 pounds quite enough!
Floor space: Because our cylinders go "up, not out" they can contain prodigious amounts of internal volume that would make for a huge box "foot-print". While a round cylinder base-plate can't snug into the very corner of a room like a box can, our cylinder subs still tend to take up less floor space than a box equivalent.
Finish/looks: All our cylinder subs are finished in a tough knit velvet-like black fabric we sourced from a high-end architectural supply company. Its light scattering properties means even our tallest cylinder subs practically disappear in a dark room corner. We've had reports of spouses that didn't even notice a surreptitious SVS upgrade until it was pointed out to them. As a result of the understate design we’ve sold countless thousands of them and most folks love their look. Some don't. They prefer the harder, more conventional edges of a box and fine textured finish or wood veneers. While our entry level box finishes are a similar shade of black, the fact they are not fabric covered enclosures is a plus, and we're not one's to argue. We developed high-performance SVS box subs precisely because folks asked for a more traditional design as an option.
Cost: Because the cylinder design is so efficient and relatively simple to manufacture, an equivalent box subwoofer will tend to cost more. Not much, but for some folks every audio budget dollar counts. A PB12-Plus and similarly performing 20-39PC+ favor the PC+ by $50. Now, you might light Cuban cigars with $50 bills, but if per chance you don't, at least you understand that a box design can cost a bit more up front. Shipping naturally adds costs too, and depending on where you live you can expect a Powered Box to cost roughly $25-50 or so more to ship given their greater weight. Our shipping rates are still amazingly low no matter how price sensitive you are, but if you are especially cost sensitive, the Powered Cylinders have a slight edge that might matter.
Box Subwoofers:
So cylinders have it "all over" boxes, right? Not exactly. Even though we engineer audio solutions for demanding buyers, there is nothing quite perfect (to our way of thinking). Cylinders have their advantages, and so too do their box brethren.
Size: While their designs are similar in nature (using common woofers, amps, ports etc) SVS box subs tend to strike some folks as less visually obtrusive. All while taking up more floor space. Why?? Box subs tend to be able to tuck tightly into a corner (you still need a few inches for the rear firing ports to breathe) and are naturally much shorter to boot. A PB12-NSD is a robust 21" tall (shedding its first generation basepate), while even our shortest cylinder sub is a little over 35" tall. This mid-sized Powered Box is a whopping 25" deep however, while the "Powered Cylinders" a mere 16" in diameter, and thus can fit into the tightest floor-space any theater or media room might present. But our great finishes make a box work like an end table, perfect drink height near a couch. Use a coaster so your Martini is shaken, not stirred.
Performance: If enclosure volume is about the same, there are no significant disadvantages, in terms of raw performance, due to a box shape versus a cylinder. But (there has to be a "but" right??)... boxes do lend themselves to multi-driver configurations that are simply not practical in a cylinder design. The PB12-NSD has single woofer so as you might expect, it's virtually identical to a 20Hz tuned version of our 20-39PCi subwoofer (especially since it shares all the same parts as the PCi subs). If you are with us so far then, you already know that when we released a PB12-Plus/2 a few years back (Powered Box, with two 12" "Plus" woofers and three way porting) you could expect it to perform nearly like two of our top-selling and industry-unique 20-39PC-Plus subs. Boxes can be made bigger and more powerful than a cylinder for those wanting the pinnacle of performance in a single sub.
Cost: Any single woofer box sub from SVS we'll offer will tend to cost about 10% more than its closest performing cylinder equivalent due to more costly enclosure construction, including the offering of premium wood or gloss finishes. Yet, considering even the lowest cost SVS box subs, like the PB10-NSD already outperforms most subs costing from $200 to $1,500 more than ours, we don't think boxes levey much of a premium. In the case of that entry level Powered Box sub, we are actually under the least expensive Powered Cylinder, the amazing 25-31PCi.
Finish: Again, some folks like boxes, others hate them due to their relative commonality in the speaker world. Regardless of how you feel about that, the tough cured-poly finish of the textured black, the beautiful woods or the elegant piano gloss box subs are all stunningly attractive and still durable enough to live in the real world. Textured black is probably the most forgiving of tough rooms, where kids and pets might rule the day. Even the sexy gloss black has been specifically developed to avoid the fragility of lesser versions of this finish. Customers who actually own top brand pianos have commented that their SVS is actually better in the level of depth and quality we offer. The woods are unmatched on our powered boxes. You would have to look long and hard to find any premium quality furniture with workmanship so meticulous or materials this fine.
Practicality: There is not much more practical than a simple box (as long as you have plenty of floor space). You can put it in a corner, put a plant on it, put a lamp on it, put Granny's picture on it (as long as you understand Granny might be moving around a bit during the pod-race scene in Star Wars: The Phantom Menace). A sub like our PB12-NSD will be impervious to your kids' peanut butter and jelly sandwiches, it'll be immune to the most vicious house cat (though to be fair, we've not had one owner report any defeating our tough cylinder subwoofer fabric either). Plants, your best friend's bottle of beer, and that 50 lb. bust of Beethoven are all very bad things to put on top of our cylinder subs by comparison. Their tops must be un-obstructed as their top-firing ports are protected by a relatively light-weight mesh grill. If this matters to you, the box SVS's gain another point in their favor
http://www.svsound.com/questions-faqs.cfm