Power handling and MaxSPL

The loudspeaker maximum performance

How do we determine the power handling and Max SPL of FAVO Audio systems? How should we understand speaker parameters and choose the appropriate amplifier?

Achieving maximum performance from a speaker set requires, among other things, selecting a power amplifier with appropriate parameters. A speaker itself does not have "power" – this is a commonly misused term, but it has become so widely accepted that we will not argue against it. A speaker has the potential to accept a certain current from the source and amplifier and convert it into acoustic power, or more precisely, what should interest us even more, acoustic pressure (SPL)*. The amplifier must be capable of driving the speaker set in such a way as to ensure maximum acoustic pressure while maintaining signal parameters that prevent damage to individual speaker components.

In this article, I will attempt to explain the key concepts related to correctly powering a speaker or speaker sets, including descriptions of the most commonly used parameters concerning their power. You will learn how these parameters influence the selection of an appropriate amplifier. I will also present test procedures and the method for determining the maximum acoustic pressure that our sets can generate.

Terms necessary to describe the behavior of a speaker subjected to a signal.

IMPORTANT! To understand the principle of correctly driving a speaker, we should first know how a speaker can be damaged. We should distinguish the causes of damage and their types.

The two most common cases of speaker damage are:

Thermal damage (burning out the coil) - This occurs when the signal delivered to the speaker causes excessive heating of the coil. The amount of heat generated by the coil exceeds the amount that the cooling system (coil + ventilated magnet) can dissipate to the surroundings. As a result, the coil overheats and burns out. This does not necessarily have to be a high-power (or high-voltage) signal. It is sufficient that the signal causes the coil to stop moving adequately in the gap and generating airflow in the cooling system.
Mechanical damage (caused by excessive excursion) - This damage occurs when the speaker diaphragm is forced to move beyond its designed range of motion. As a result, the diaphragm and/or its suspension can be physically damaged. Such damage most often occurs when the delivered signal consists of lower frequency ranges than the speaker set can handle.

The following three concepts are closely related to the energy delivered by the signal. I encourage you to remember them. They are extremely important for understanding the operation of all devices used in the sound path. They are the key to achieving proper results in working with sound and understanding the causes of failures and equipment damage.

RMS (root-mean-square) - It is a measure of the averaged power level of the signal. The RMS level effectively represents the amount of its thermal energy.
Peak - Represents the maximum, instantaneous level that the signal reaches. For the sinusoidal signal shown in the figure below, the peak level is 3dB higher than its RMS level. This is the signal for which amplifier power is usually specified. In the case of music, the maximum, instantaneous (peak) signal level can easily reach even 10-20dB above the RMS level (i.e., much lower voltage). The peak parameter is also important in determining the threshold of excessive speaker excursion.
Crest Factor (CF) – It is used to describe the ratio of the maximum, instantaneous level that the signal reaches (peak) to the RMS level of the signal, both for pink noise and other signals. It can be expressed as a numerical value (ratio) or in decibels. The Crest Factor for direct current will always be 1 (0dB), for a sinusoidal waveform 1.41 (3dB), but for pink noise with random component values, the CF can vary depending on the difference between the RMS and peak levels. For a CF equal to 6dB (ratio 2), the peak voltage is twice as high as the RMS voltage level.

Power Measurement Method of Speakers According to AES

The AES-1984 Standard describes a method developed by the Audio Engineering Society for testing a speaker to determine the power it can handle.

The key test conditions are as follows:

Mounting of the high-frequency (HF) speaker: The driver is mounted on its designated horn, providing appropriate acoustic loading.
Mounting of the low-frequency (LF) speaker: The speaker is mounted in open air, and its orientation ensures that its movement occurs in the horizontal plane.
Test signal: Pink noise with a Crest Factor set to 6dB is fed to the speaker. The pink noise is limited to the frequency band starting from the speaker's resonance frequency (fs) to the frequency fs*10.
Power calculation: The RMS voltage level delivered to the speaker is measured. Power is calculated based on the RMS voltage and the minimum impedance of the tested speaker according to the formula P = V²RMS / Zmin.
Test procedure: The speaker is subjected to progressively higher signal levels in time intervals allowing the speaker to stabilize with each increment. The recommended stabilization time is 2 hours.
Nominal power (AES power): It is determined as the maximum possible power that allows the speaker to withstand the above test for 2 hours without changes in acoustic, mechanical, and electrical characteristics exceeding 10%.

How We Determine the Power of FAVO Speaker Systems:

We base our method on the AES standard but with some important modifications. The AES standard refers to a single speaker, whereas at FAVO AUDIO, we test complete systems composed of multiple speakers and passive filters (crossovers) before delivering them to the user.

How We Determine the Power of Our Speaker Systems:

Speaker Mounting: The speakers are mounted in the appropriate enclosure for the model and tested under conditions identical to those in which the speakers will be used by the end user.
Test Signal: Similar to the AES standard, we use pink noise with a Crest Factor of 6dB. The test signal is subjected to frequency filters (low-cut and high-cut) to limit the spectrum of frequencies delivered to the speaker to only those handled by the tested device.
Power Calculation: RMS voltage is measured at the speaker. The difference is that the power calculation is based on the averaged impedance over the entire relevant frequency range for the given speaker system, not the minimum impedance. This provides a more accurate indication of the actual power delivered to the speaker (P = V²RMS / Zaverage).
Test Procedure: The tested system is initially "warmed up" by a low-level signal for about 30 minutes. We start with a signal level equal to half the nominal AES power of the low-frequency speaker, then the system is subjected to progressively higher power levels, allowing the speaker to stabilize. A 30-minute cooling period is taken between each step to allow for cooling. Power is increased in each step by 0.5dB(W). The speakers, along with all passive components, are tested for signs of wear and damage between each power increase. This "cycle" simulates real-world usage where components are cyclically heated and cooled rather than consistently loaded with a steady current at a stable temperature.
Nominal Power: The system's power is set at 1dB(W) (approximately 50-200W depending on the model) less than the power level that caused irreversible changes in the speaker or its passive components (e.g., crossover when testing a speaker system).

Maximum Acoustic Pressure Produced by the Speaker System:

The sound pressure level (SPL) that a speaker can produce is one of its primary parameters. It indirectly shows how much electrical energy the driver can convert into acoustic energy (i.e., how loud it is).
A speaker with a higher SPL achieved from one watt will be louder than one with a lower SPL. The decibel scale is logarithmic, and it is generally accepted that every 10dB SPL increase is perceived as twice as loud (this is true for mid and high frequencies, but for bass frequencies, only a 5dB increase is perceived as twice as loud)*.
Different drivers will play at different volumes with the same signal delivered by the amplifier. Remember: 1000W from an amplifier into a speaker that generates 97dB SPL at 1W will produce the same real loudness as 500W into a speaker that generates 100dB SPL at 1W. Not only will such a setup be equally loud, but it will also consume half as much electrical energy.

* for details on the equal-loudness contour, see Fletcher-Munson curves and their updates ISO 226:2003.

Every technical specification of FAVO AUDIO includes a section on various SPL values for different signals to help the user compare parameters.

"Maximum SPL (dBSPL@1m)" This is the expected acoustic pressure that will be produced by the speaker system (at a distance of 1 meter) based on the measured nominal power, sensitivity, chosen test signal, and a sufficiently powerful amplifier. However, it should be noted that peak efficiency will be 6dB or 12dB higher than that under "long-term, constant load." This is due to the use of pink noise with CF = 6dB and CF = 12dB during the tests determining the maximum power of the system, as described above.
Other leading manufacturers using different test signals achieve different MaxSPL parameter values. This is a topic for another article, which will certainly be addressed to help you compare different products and choose the optimal tool.

written by: Kamil Kieca