3 part review:
Frequency response graphs from WINISD box program
The Soundstream RUB.124 is a really solid subwoofer for under $100. It has an overall deeper sound than the previously reviewed Pioneer TS-W311D4. I have tried both subwoofers in the large ported box and in a small sealed box. It still retains a slightly punchy feel and is not an earthshaking SPL subwoofer. In my application I have achieved excellent sound quality with enough SPL to hear it on the highway with the windows down.