Having owned both (replaced my X-Sub with a PB10-ISD), I have to say I agree with pretty much everything Ron's said, except I must politely and respectfully disagree about the X-Sub being 80% of a PB10. IMO, it might be 40-50% of a PB10,
maybe. But that's hard to qualify because they sound quite different from each other. One of the first things I noticed about the PB10 was that at similar volumes on similar material, you might seem to hear a bit less bass than you heard on the X-Sub, but you FEEL a lot more.
The difference, I believe, is accuracy. The PB10 is a VERY accurate performer right down to 20 Hz, without any unneeded emphasis on any particular frequencies, whereas I think the response of the X-Sub has more variation to it, at least to my ears. To me the X-Sub sounded as though it was over-emphasizing the mid to upper bass regions a bit but rolling off quickly under around 30 Hz.
After a lot of hours with both subs, I also feel the X-Sub has a fuzzier, less defined sound than the PB10, which by contrast has a very tight, punchy, clean and natural sound (and a LOT more clean output).
HOWEVER, please don't let these comments discourage you from trying out the X-Sub! My comments might sound negative but all this is simply in comparison to a sub that I personally feel strongly is totally in a class by itself. In fact I'm totally serious when I say I think Ron and Tom have made a grave error in their pricing, and should be charging a LOT more money for the PB10-ISD. There's just no way a sub should sound the way it does and perform the way it does for anywhere near $429. (Of course I'm tickled pink that they ignored my opinion and kept the price low.
) If you can possibly stretch your budget to afford it, DO.
If not, I think the X-Sub is a fine product for under $250 and a great value, as long as your particular sample doesn't hum (mine did but only a little, didn't bother me). It's put together really nicely and it does rock the house. My younger cousin is enjoying my X-Sub as we speak, and he's a good young musician with excellent ears.