Looks like Mark Seaton was the only one over there that did their homework. At least he was the only one that seamed to get it.
First there are pros and cons (tradeoffs) in everything.
There are always the guys that will claim that a sealed box is the only way to go, blah, blah, blah. Well, our SW-12A sub-woofer works great in a sealed box and has much better low end extension in a sealed box that most. -3db down at 39Hz in only 1.175 cubic feet.
The problem is that -3db down of 39Hz just isn't low enough. For a sealed box design to have the necessary extension it needs to be used with an amp that has a Linkwitz transform circuit. Now how many commonly available plate amps have a transform circuit built in? Then each woofer needs to have its own transform circuit in order to produce the inverse of its roll off. Different woofer, different Q, different roll off, different transform circuit.
I have had dual 18" woofers in here in sealed boxes with custom built transform circuits and big amps on them. Did it hit hard? Sure, but it wasn't the end all be all in sound quality. In fact I really didn't like it. So much gain was required of the amp, then it would drive the amp out of head room and distortion would go up accordingly.
Then when you get a big enough amp to have enough head room to drive the load, and the gain, you run out of power handling on the woofer. The woofer will more quickly reach its mechanical limits and bottoms out. Woofers in a sealed box just will not handle as much power in the low frequency ranges.
And if a sub is being used where it is supposed to be used, covering the first octave (20 to 40Hz). Then things like group delay are really not an issue. The wavelength at 20Hz is about 56 feet long and at 40Hz it's 28 feet long.
IB designs and even a properly set up sealed box design with a transform circuit can be made to sound very good though. You must use more woofers and not over drive them. Long woofer exertions can really compress the air at the cones surface and flex a cone. This is another form of distortion. Using lots of woofers just loafing along solves this. But a lot of people don't have room for a wall of woofers.
The ported box and PR configurations will give you more low end extension and more power handling down low too. Then you can use a standard sub-woofer amp from anywhere.
Now our woofer was specifically designed for three things. Sound quality, low extension down to 20Hz (-3db), and do so in a small box without giving up too much sensitivity.
To get really low extension in a small box with a port requires a large port. With our woofer tuned to produce a -3db down of 22Hz in an optimal ported enclosure means that the port must be 4.8" in diameter and 42" long. Ah, that won't even fit in the box.
Or our PR can be used to get a -3db of 20Hz and do it in only 2.4 cubic feet.
Another advantage of the PR over the port is that there is no port noise. Secondly, the PR can load the woofer in such a way as to increase its impedance in frequencies below 20Hz. In other words the power handling in the sub-sonic range (below 20Hz) goes up by a large factor. In fact the use of the two together (the SW-12A and PR-12A) will keep the woofer from bottoming out.
So, small box, high output levels to 20Hz, good sound quality, and drive it with any common amp.
Here is my favorite budget amp for our woofers:
http://www.apexjr.com/Apexsenior.htmHere is what I really like about this amp:
Variable phase, this is a must! It will output 400 watts (we tested it) into 4 ohms. Sense our subs are 8 ohm loads (big plus) you can run a pair of them off of this one amp. 400 watts on two twelves in a small box.... but it gets even better. Adjust the boost circuit on the amp to give +2db of boost in the 20 to 22Hz range and now our subs are only down 1db at 20Hz. 1db down at 20!!!
Another important factor regarding sound quality is the box design. A good solid box that makes no noise of its own (free of resonation) goes a really long way.
I would still have to say that the best thing about our sub is the sound quality. Some already know. Some of you have yet to find out for yourselves.
Oh yea, the price is really right too.
