I would rate the SMS-1 very highly. I never would have believed it.
Before, adjusting the bass by ear, I could never get it to sound just right. You can't identify the "peaks and big valleys" just by ear. My prior technique: "Put the sub in the corner, play with knobs, and listen" turned out to not be the perfect plan... Now I know that there was a strange peak at the very bottom and a big valley near 100, due to my Q setting (adjustable on my sub), gain, polarity, and placement.
Before, I bought I thought: how much difference can there be by adjusting that little part of the sonic range and the SMS might just change my music to have a different kind of boomy sound? -- or so I thought...
After: The SMS-1 is very easy to use once you figure out the instructions and get all the wires connected. The SMS-1 is so visual -- you see the bass right on the TV screen as a line. After just a few minutes of adjusting, the bass response curve is flat as a pancake and music sounds like I was shooting for. Lets just say I was excited like a litte kid. All different types of bass in the music sounds clean and warm. THE BEST PART FOR ME: Plus, (mentally) I like knowing that it is flat so I don't have to waste time playing with it anymore...
I am surprised that the music sounds so much better now. I can finally just listen and not tweak anymore.
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As an aside (because this next part will apply to hardly anyone), it was still easy even though I did not use the SMS-1 in the standard way. I have stereo Vandersteen 2wq subs. Instead of using the internal sweep tone from the SMS-1 (which would not be possible for me due to the 2wq's odd design), I used the subwoofer warble tones from the Stereophile first CD and watched the response from the SMS-1 on my TV screen while I changed a few settings on my subs. The SMS-1 was a easy-to-use diagnostic tool.
I wish the price was lower so everyone could try it, but it was worth it for me.