Speaker specification sheets look precise and are mostly not. Four figures appear on almost every one: power handling in watts, sensitivity in decibels, impedance in ohms, and frequency response in hertz. Each of them means something real, and each of them is routinely published in a form that hides more than it reveals. Here is what to do with them.
Watts: a limit, not a loudness
Power handling tells you how much electrical energy a speaker can absorb before something fails, usually the voice coil overheating or the cone hitting its mechanical limit. It says nothing about how loud the speaker plays, because that depends on how efficiently it converts watts into sound.
Three versions circulate. RMS or continuous power is a sustained rating and is the useful one. Program power is usually quoted as double RMS. Peak power describes brief transients and is the number marketing prefers, because it is the biggest. A speaker advertised at 800 watts peak may be a 200 watt RMS design.
Amplifier ratings have the same problem in reverse. A professional amplifier like the Crown CDi 1000 is specified as 500 watts per channel into 4 ohms, and Crown states the load and the topology, which is what makes the figure meaningful. Consumer listings often omit both. The CDi 1000 entry on this site also carries an “output wattage: 700 watts” line alongside the 500 watt figure, which is exactly the kind of inconsistency to be alert to.
The practical guidance is unglamorous. Amplifier power and speaker power handling do not need to match. An underpowered amplifier driven into clipping damages tweeters far more often than a powerful amplifier used sensibly does, because a clipped waveform sends sustained high frequency energy into a driver designed for brief transients.
Sensitivity: the number that actually predicts loudness
Sensitivity is measured in decibels of sound pressure at one meter, given one watt of input, or sometimes 2.83 volts of input. It tells you how much sound you get per watt, and it is the single most useful specification on the sheet.
The scale is logarithmic and unforgiving. Every 3 dB of extra sensitivity halves the amplifier power needed for the same loudness. A speaker rated at 96 dB needs one quarter the power of an 90 dB speaker to reach the same level. That is the difference between a modest receiver being adequate and being out of its depth.
| Sensitivity | Rough classification | Amplifier implication |
|---|---|---|
| Below 85 dB | Low, common in small sealed designs | Wants real power, 100 watts and up |
| 86 to 89 dB | Average for domestic speakers | Comfortable with a mid range receiver |
| 90 to 93 dB | Above average | Modest amplifiers are fine |
| 94 dB and above | High, typical of horn loaded designs | Loud on very little power |
Horn loaded designs sit at the top of that table by construction. Klipsch has built its Reference range around this idea for decades, and the Klipsch R-620F uses the company’s Tractrix horn on the tweeter for exactly this reason. Small sealed standmounts sit at the bottom, trading efficiency for a compact cabinet.
Two cautions. Sensitivity is sometimes quoted in half anechoic conditions, which flatters the number by about 3 dB compared with a true anechoic measurement. And it says nothing about how the speaker sounds, only about how much of it you get per watt.
Impedance: the load your amplifier sees
Impedance is the resistance a speaker presents to the amplifier, and it varies continuously with frequency. The published figure is a nominal average, usually 4, 6, or 8 ohms. A speaker labeled 8 ohms may dip to 3 ohms at some frequency and rise to 30 ohms at another.
Lower impedance draws more current for a given voltage, which is harder work for the amplifier. Most home receivers are specified for 6 or 8 ohm loads, and many enter protection or overheat with a genuinely 4 ohm load driven hard. The Wharfedale Linton is listed at 6 ohms nominal, and outdoor designs such as the Polk Audio Atrium 4 at 8 ohms, which is the more forgiving load for a multi zone amplifier driving several pairs.
What actually matters is the combination of a low impedance dip and a large phase angle at the same frequency, because that is where an amplifier has to deliver high current at an awkward moment. Very few consumer listings publish impedance curves, so if you are pairing an unusual speaker with a modest amplifier, the manufacturer’s own technical documentation is worth hunting down.
Frequency response: the number with the missing half
A frequency response specification is meaningless without a tolerance window. “45 Hz to 20 kHz” tells you nothing. “45 Hz to 20 kHz, plus or minus 3 dB” tells you the speaker holds within a 6 dB band across that range, which is a real claim.
Without a tolerance, a manufacturer can quote the point where output has fallen by 10 dB or more, which is far below anything you would call usable. This is the most commonly abused figure in the entire category, and the omission is deliberate often enough that its absence is itself information.
The other missing piece is that response is measured on axis, in an anechoic chamber. Your room is not one. Below 200 Hz the room dominates completely, which is why placement changes bass more than any specification does, and why a subwoofer such as the SVS SB-1000 Pro ships with app based room correction rather than relying on its published curve.
What the specification sheet leaves out
Distortion figures are rarely published for passive speakers. Off axis behavior, which governs how a speaker sounds from a sofa rather than a single sweet spot, is almost never published. Cabinet resonance is not published. These matter more to perceived quality than the four headline numbers, and their absence is why listening and reading detailed measurements beats reading spec tables.
Powered speakers put more of this in one place, because the amplifier is matched to the driver at the factory. A powered monitor such as the Behringer Eurolive F1220D, listed at 250 watts with a 12 inch woofer, or a larger unit like the QSC K10.2, removes the amplifier matching question entirely. Note that the K10.2 listing classifies it as a subwoofer, which it is not, and the Behringer entry lists a 12 inch woofer under a field labeled subwoofer diameter. Auto filled spec tables in this catalog frequently put values in the wrong row.
There is one more figure that appears occasionally and is worth more than most of the headline four: the recommended amplifier power range. When a manufacturer states something like 25 to 150 watts, it is telling you both that the speaker will sound thin below the lower bound and that it will be at mechanical risk above the upper one. That range encodes real engineering judgment about the driver and the crossover, and it is a better guide to amplifier matching than a single power handling number ever is.
A short checklist
Look at sensitivity first, because it predicts whether your amplifier is adequate. Check nominal impedance against your receiver’s rated load. Treat frequency response as unusable unless a tolerance is stated. Ignore peak wattage entirely and use RMS if it is given. Then compare speakers within the floorstanding and bookshelf categories on cone area and cabinet volume, which are the physical quantities the specification sheet is trying, imperfectly, to describe.
