Loudspeaker - Specifications

Specifications

Speaker specifications generally include:

• Speaker or driver type (individual units only) – Full-range, woofer, tweeter, or mid-range.
• Size of individual drivers. For cone drivers, the quoted size is generally the outside diameter of the basket. However, it may less commonly also be the diameter of the cone surround, measured apex to apex, or the distance from the center of one mounting hole to its opposite. Voice-coil diameter may also be specified. If the loudspeaker has a compression horn driver, the diameter of the horn throat may be given.
• Rated Power – Nominal (or even continuous) power, and peak (or maximum short-term) power a loudspeaker can handle (i.e., maximum input power before destroying the loudspeaker; it is never the sound output the loudspeaker produces). A driver may be damaged at much less than its rated power if driven past its mechanical limits at lower frequencies. Tweeters can also be damaged by amplifier clipping (amplifier circuits produce large amounts of energy at high frequencies in such cases) or by music or sine wave input at high frequencies. Each of these situations might pass more energy to a tweeter than it can survive without damage. In some jurisdictions, power handling has a legal meaning allowing comparisons between loudspeakers under consideration. Elsewhere, the variety of meanings for power handling capacity can be quite confusing.
• Impedance – typically 4 Ω (ohms), 8 Ω, etc.
• Baffle or enclosure type (enclosed systems only) – Sealed, bass reflex, etc.
• Number of drivers (complete speaker systems only) – two-way, three-way, etc.

and optionally:

• Crossover frequency(ies) (multi-driver systems only) – The nominal frequency boundaries of the division between drivers.
• Frequency response – The measured, or specified, output over a specified range of frequencies for a constant input level varied across those frequencies. It sometimes includes a variance limit, such as within "± 2.5 dB".
• Thiele/Small parameters (individual drivers only) – these include the driver's F_s (resonance frequency), Q_ts (a driver's Q; more or less, its damping factor at resonant frequency), V_as (the equivalent air compliance volume of the driver), etc.
• Sensitivity – The sound pressure level produced by a loudspeaker in a non-reverberant environment, often specified in dB and measured at 1 meter with an input of 1 watt (2.83 rms volts into 8 Ω), typically at one or more specified frequencies. Manufactures often use this rating in marketing material.
• Maximum SPL – The highest output the loudspeaker can manage, short of damage or not exceeding a particular distortion level. Manufactures often use this rating in marketing material—commonly without reference to frequency range or distortion level.