Specifications exist for a reason — they encode engineering decisions and physical constraints that have real consequences in use. The challenge is knowing which specifications carry meaningful information and which are measurements conducted under conditions too idealised to be useful. Approaching a specification sheet with this understanding saves time, narrows the field before the audition begins, and prevents obvious mismatches.
Frequency response is the most quoted specification and one of the most widely misrepresented. A frequency response of 40 Hz to 20 kHz tells you almost nothing without knowing the measurement conditions: at what distance, in what environment, within what tolerance window, and whether the measurement is on-axis only or includes off-axis behaviour. A ±3 dB tolerance at 1 metre on-axis in an anechoic chamber is a meaningful, demanding specification. A ±6 dB tolerance at unspecified conditions is nearly useless as a comparison tool. Where full frequency response curves are published — showing the actual shape rather than just the frequency limits — they are far more informative than the single-line specification.
Sensitivity is a specification that translates directly into practical system matching decisions and should be evaluated carefully. A 2 to 3 dB difference in sensitivity between two speakers has the same effect on loudness as doubling or halving the amplifier power. For a given amplifier, the sensitivity specification determines whether the speaker is an easy or demanding drive — and whether low-powered amplifiers are viable options.
Nominal impedance and minimum impedance are both relevant, as discussed in earlier articles. The minimum impedance point — which determines the maximum current demand on the amplifier — is more useful than the nominal rating. Where manufacturers publish impedance curves rather than single-number ratings, they are providing genuinely useful information.
What specifications cannot tell you is how a speaker sounds in your room with your electronics. They can rule out obvious mismatches — a speaker too insensitive for a low-powered amplifier, a bass extension too deep for a small room — but they cannot confirm a match. That requires the audition.