I've noticed that a lot of people around here recommend the Polk PSW 505 subwoofer. As a person who has built a number of his own subwoofers I've wondered about how good this product really is in the cosmic scheme of things.
Please don't interpret this post as a critique of the PSW 505 as being a bad value. It has been sold lately for less than $200 and at that price it is not that much more expensive than its cabinetry. As I've said before I've built my own subwoofers and I've paid much more than $200 for just the subwoofer driver, and then spent more than $200 for the power amp to drive it. I've also spent more than $200 for just the active crossover. So, in some sense a $200 subwoofer that actually does something is a bit of a marvel!
As many of you know I've been running a computer model that estimates the capacity of speakers to deliver clean sound as a function of frequency. I decided to use it to see if I could figure out some things about the PSW 505.
I found that an energetic AVR member had run some tests on his own PSW 505 and posted the following graph that I've plotted some more information from the computer model onto:
The first line I added is the black line that is my model for a speaker with a 12" diaphragm and 6.5 mm Xmax. The way that it sits on top of the results for the actual measurement suggests to me that the Xmax of the PSW 505 driver roughly in the 6 or 8 mm range which is well below that achievable with the best available subwoofer drivers. Of course a SOTA 12" driver runs 2-4 times the price of an entire PSW 505 system!
Just for grins I added the red line that shows an estimate of the performance of a SOTA driver with a 12" diaphragm and 30 mm Xmax. Basically, everything below 50 Hz is about 15 dB louder which is quite a bit and would sound really cool if you like to crank things up a bit. This driver might require quite a bit more power to do its best - maybe a kilowatt or two.
One point I see is that no way is it fair to characterize subwoofers based on just the size of their drivers because Xmax can vary so much for a given driver size. My current subwoofer is a far more expensive unit that also has a 12" driver that I hope has far more Xmax than the PSW 505. However there's no way to find out whether or not that is true from most vendor spec sheets, and/or published tests by third parties.