Pros: Small, inobtrusive, moderate price. Significantly improves the sound of the stock radio.
Cons: Supplied mounting system is wobbly, may not be loud enough for larger vehicles.
Properly used, a subwoofer can provide a stunning upgrade to many stock car sound systems. Put simply, the speakers that come with the car or van -- at most 6x9's often as small as 4" -- just can't provide much in the way of real bass, and the tiny spaces allotted in the vehicle's body don't help the matter. The problem is, most subwoofer systems are large, forcing the sacrifice of most or all of the trunk space. What about smaller cars, or a pickup truck -- or in my case, a cargo van -- that only seats two?
SAS has been making tube subwoofers for many years, and this is arguably the end result of all that work: a small, inexpensive, self-powered tube with a specially chosen 6" woofer. No, it won't duplicate the low end of a home theater system, but that's not it's purpose. Like many target users, I'm not looking for the kind of 'thump' that can be heard when the car is approaching from two blocks away; I'm just looking for some *real* bass: a kick drum that is felt more than heard, smooth clear synthesizer bass, and a nice 'thump' from an upright bass.
The BTA6100 is a self-powered speaker system mounted in a laminated tube. It's pretty small: a pair of them could be carried in a standard paper shopping bag, sticking out a little at the top. It's rated at 100W peak -- they don't really say, but that probably means about 50W RMS -- which is enough power to match with the average stock car or truck radio. The tube cabinet is covered in scratch-resistant paint with a rough texture, so it should stand up to the abuse of a trunk. There are only two controls: a volume knob and a polarity switch.
The speaker comes a short mounting harness, but they SAS also sells their 'F.A.S.T.' system which allows connection to the radio without splicing into the wiring; this is great for customers who lease their vehicles. Just connect the regular radio connector into the F.A.S.T. adapter, plug the other end back into the radio, then connect wiring harness from the subwoofer to the third connector. If you know how to get at the radio, the whole wiring can be done in less than half an hour.
The speaker itself attaches with mounting brackets and a pair of cloth straps. This is my only complaint about the system: the cloth straps hold the speaker tube in place, but it can wobble around. A firm mount is important to get all the low end possible from a speaker, so this isn't a good thing. AS also sells a mounting kit which holds the speaker firmly by the ends, but it's chrome plating a little too 'bling' for my liking. I found a little trick that I'd like to pass along: Get two of those metal hose clamps that have the worm gear to tighten them at a local hardware store. The 8" size is just about perfect for this application. Put a small strip of rubber or foam under the clamp at the top of the tube, and tighten SLOWLY until the tube is firmly held in place.
Getting the subwoofer to sound its best takes a little playing around. The polarity switch is easy: the difference in volume will be like night and day; you want the louder one. The volume adjustment is a little more tricky -- or maybe, counter-intuituve. You want more bass, right? Well, turn the bass *down* on the radio, then turn the subwoofer up to compensate. Don't force the tiny built-in speakers to make the bass; hand that job over to the subwoofer. In about 5-10 minutes of listening, you should be done.
How does it sound? It's probably the biggest improvement that can be made to your sound system for under $500. Freed of the impossible task of producing bass, the vehicle's speakers often turn into surprisingly good midrange and tweeter speakers. I bought a pair of Rockford-Fosgate speakers to complete my Dodge Grand Caravan C/V system, but I'm considering taking them back; the change is that much different.
Be aware that the BTA6100 isn't loud enough for connecting to a sound system that fills a large van, or is used for tailgate parties. It's best paired with a pickup truck or car the size of a Mini Cooper/Toyota Prius. If you need more output, there are 8" and 10" versions of the subwoofer tube, or consider using a pair of the 6" models. There are also higher-power versions (250W), but I'm not sure they buy much improvement: that's 5dB more power, but the woofer is 3dB less efficient -- a mere 2dB net -- and they can't use the F.A.S.T. wiring system, so the installation is more complicated.