Can the frequency range specs in Crutchfield be trusted or are they just ad fluff straight from the manufacturers?

Well the frequency ranges aren't necessarily representative of the actual RESPONSE of the speaker. Sure, a speaker might go all the way down to 20hz, but what that number doesn't tell you is (for example) the speaker has a huge presence peak at 255hz and the response at 20hz is barely audible.

What one really needs to see is graphs of a given speaker's frequency response. The only problem is that even THAT is governed to a certain extent by the enclosure. So you can't really win.

In the end, I only use the on-paper frequency range as a rough guide.

Here's what I've gathered to learn so far: ported enclosures can be 'boomy' at certain frequencies, while sealed enclosures don't go as loud (but are more accurate),

Ported boxes don't necessarily have to sound boomy, but they will tend to have a frequency peak at a specific frequency which you'll need to plan and adjust around. A sealed box will have a flatter frequency response without as much of a single big peak. And like they say in the Crutchfield catalog, sealed boxes need more powerful speakers and more wattage. Just make sure that your speaker and enclosure are properly matched-- certain speakers were made for sealed boxes, others for ported boxes, for example. And you have to get the box volume right.


but are there BIG differences between the $89 Infinity Kappas and those in the $180 range?

On paper, you should be seeing differences in power handling, efficiency, and frequency response. In real life, you should see differences in longevity and flatness of frequency response.

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Tony Fabris