RMS vs Program vs Peak Power
RMS vs program vs peak power is mostly a question of which test produced the number. The continuous figure, ideally measured to AES2, is the only one that says what a driver survives for hours. Program and peak are derived from it, and makers derive them differently.
Continuous: AES, "RMS", "nominal"
Under AES2, the driver is fed pink noise with a 6 dB crest factor (peaks at twice the RMS voltage), band-limited to its working range (50 to 500 Hz is typical for a woofer), for two hours. Power is calculated from the RMS voltage and the minimum impedance in that range. The rating is the level the driver survives in working order. Makers label the same kind of figure "AES", "RMS" or "nominal"; strictly, RMS describes a voltage or current, not a power.
Program
B&C define continuous program power as double the nominal (AES) figure, +3 dB, and present it as a recommended amplifier size. Music has a crest factor well above 6 dB, commonly 12 dB or more, so an amplifier sized at twice the AES figure can reproduce peaks without clipping while the average power stays within the driver's thermal limit. It is not a licence to run that power continuously.
Peak
Peak is the short-term figure a driver is quoted to withstand on transients. There is no single industry rule for deriving it from the continuous rating, so the same word can mean different multiples on different spec sheets. Read the notes under the table.
Same driver class, different labels
| Driver | Continuous | Second figure | Price per continuous watt |
|---|---|---|---|
| Wavemark WM1850/8 | 1800 W AES | 3600 W peak | 15.3p (£275) |
| Wavemark WM18X451 | 1800 W RMS | 3600 W max | 19.2p (£345) |
| B&C 18SW115 | 1700 W nominal | 3400 W continuous program | 26.1p (£444, Thomann UK) |
All three put their second figure at twice the continuous one, but call it peak, max and continuous program respectively. Compare the first column, and remember the test standards are not identical, so price per watt is a guide rather than a lab result.
Power vs sensitivity
Doubling power adds 3 dB; ten times the power adds 10 dB. A driver 3 dB more sensitive needs half the amplifier power for the same level, so sensitivity and power handling have to be read together. Heat also matters: as the coil warms its resistance rises and output drops. See sensitivity and decibels and voice coils and heat.
What kills drivers
- Over-excursion below the box tuning without a high-pass filter.
- Sustained clipping, which raises average power towards the amplifier's maximum.
- Running program-level power continuously on heavily compressed material.
Size the amp sensibly and set limiters to the continuous rating: see amp matching and limiter settings for subs.
Sources: B&C Speakers, power handling definitions and 18SW115 data, checked October 2026; Thomann UK listed price for the 18SW115 8 Ω, checked 11 October 2026; Wavemark WM1850/8 spec sheet and WM18X451 product data.
Questions
What is the difference between RMS, program and peak power?
Continuous (AES or "RMS") power is what the driver survives on a two-hour pink-noise test with a 6 dB crest factor. Program power is usually twice that and is a recommended amplifier size for music. Peak is a short-term transient figure with no single rule for how it is derived.
Which power rating should I compare between speakers?
The continuous rating, ideally to AES2. Program and peak are derived from it and makers derive them differently, so comparing them across brands is misleading.
How big an amplifier should I use for an 1800 W AES driver?
B&C's convention is to recommend an amplifier of about twice the continuous rating, so around 3600 W into the driver's impedance, with a high-pass filter and limiter set to protect it.
Does doubling amplifier power double the volume?
No. Doubling power adds 3 dB. A perceived doubling of loudness takes around 10 dB, which is ten times the power.