Is There A Device For Home Use That Can Measure How Low The Bass In My Speakers Is?

hypoman is the first, and only, contributor to this thread to even mention an essential parameter relevant to almost every other suggestion: that the SPL meter must be properly "weighted." The meter elliotbnewcombjr actually provides a link to will be useless for measuring bass output: it is "A weighted," which does not register anything below 100 Hz. The vast majority of such inexpensive meters available on Amazon or eBay are "A weighted," like the one in that link, which are intended for measuring industrial noise levels, not music. I learned this the hard way: I acquired one of those "A weighted" meters, and was puzzled that the readings I got seemed impossibly low for the subjective loudness they presumably measured. A device that will allow you to switch between "A" and "C" weighting will dramatically reveal the difference. And since the OP is interested specifically in "how low" his speakers will go, none of the suggested meters in this thread will be of any use at all in determining this.

dgluke complains that suggesting SPL meters when the OP had asked for Hz is "braindead." But--duh!--Hz are audible as SPL. And then dgluke suggests the Hsu test tone CD, like everyone who mentioned SPL readings also did (even if not the Hsu CD specifically).

The easy way to "measure" if your speakers go down to 20 Hz, or 16 Hz (if you’ve got a Hsu sub, apparently) is to play such a test CD and LISTEN! If you can’t HEAR your speaker producing the tone, measure the output with an SPL meter. If you’re still skeptical, take the grill cloth off and watch the cone move.

Thanks, dgluke, for the John Atnkinson Stereophile link. The whole article is interesting and informative. In any case, I did not know about "B weighting"; my SPL meter only gives me a choice between "A" and "C". There are, of course, several other equalization curves in use; "A" and "C" are just the most common. But, as Atkinson remarks at the beginning of the article, "A weighting" does not correspond to perceived loudness levels, which is what I've certainly experienced and pointed out above—and the SPL meters mentioned, and even linked, elsewhere in this thread are all to "A weighted" devices.

As for the relevance of using an SPL meter to judge how low a speaker's frequency response might go, let me quote Atkinson's own words from that same article: "If you plot, say, a loudspeaker's sound-pressure level against frequency for a given input voltage, the result is the typical amplitude or 'frequency' response."

In short, using an SPL meter in conjunction with a low-frequency test track is, indeed, a valid way of determining "how many [H]ertz my speakers measure for bass," in the OP's words.