- What is RMS power?
- How do I calculate the impedance that results from connecting several loudspeakers?
- What is average power?
- What is programme power?
- Why is the impedance that I measure with a multimeter different from the system's nominal impedance?
- What is AES power?
- What is peak power?
- What is IEC power?
- What is efficiency?
- What is horn EQ?
- What is sensitivity?
- What is this excursion thing then?
- Why is ther no sound from the audio system?
- Why is there a “Clicking” from audio system between changes?
- Why is there a Severe Power hum when audio system is muted?

What is RMS power?
"RMS power" is a misnomer derived from the usual method of calculating speaker power, which is to divide the RMS voltage squared by the impedance (V²/Z). RMS is the acronym for root-mean-square, which relates to the mathematical equation that obtains the average of the modulus of an alternating signal (that is, with positive and negative cycles). The correct expression for "RMS power" is average power. The ratio between RMS and peak values is different for each signal.

How do I calculate the impedance that results from connecting several loudspeakers?
The total impedance for a number of speakers in parallel is equal to the impedance of one divided by the number of speakers. For instance, two 8-ohm speakers in parallel total 4 ohms (8 ohms divided by 2 speakers equal 4).

If the speakers are in series, the total impedance is the sum of the individual impedances of each speaker. For instance, two 8-ohm speakers in series total 16 ohms (8 ohms plus 8 ohms equal 16). In pro audio, series connections are rarely used outside low power applications such as background music, paging, or surround sound.

What is average power?
It is the result of deriving power from an RMS value of voltage or current. It is the correct way of writing "RMS power".

What is programme power?
Programme power is an archaic term dating back to when power tests used sine waves. Many manufacturers, including D.A.S. Audio, apply a convention whereby programme power is twice the average ("RMS") power, although other manufacturers may use different power ratios, which may even vary from product to product. Nowadays the term "programme power" has no specific meaning, although it might be used as a power amplifier recommendation for controlled applications.

Why is the impedance that I measure with a multimeter different from the system's nominal impedance?
The multimeter looks at resistance, not impedance. Impedance is the opposition to the passage of alternating current and varies with frequency. Resistance is the opposition to the passage of direct current. Resistance is normally lower than nominal impedance. For instance, an 8-ohm nominal impedance cone speaker would typically have a (DC) resistance around 6 ohm. See any DAS spec sheet for an impedance curve. Dedicated impedance meters for audio use exist; they typically use a sinewave generator to measure impedance at 1 kHz, so you need to look at the speaker's impedance chart to see what value you should expect at that frequency.

What is AES power?
The AES (Audio Engineering Society) publishes a standard for the measurement of loudspeaker component parameters. Generally speaking, this standard calls for a 2-hour test using pink noise with specified dynamics and with a frequency content that matches the component's frequency range. Although it is a standard for components, it is often extended to the different ways on an active system. The rating always derives from RMS voltage or current measurements, therefore the rating corresponds to average ("RMS") power.

What is IEC power?
The IEC (International Electro technical Commission) publishes standards for loudspeaker measurement. We can speak of IEC power by following those standards. Specifically, IEC 268-1 defines a signal with specified dynamics and a frequency content that tries to resemble that of real music. The rating always derives from RMS voltage or current measurements, therefore the rating corresponds to average ("RMS") power.

What is efficiency?
Efficiency is the ratio between the acoustic power output and the electrical power input to a loudspeaker. Power not converted into sound ends up as heat. Loudspeakers are very inefficient devices that put out more heat than sound.

What is horn EQ?
A compression driver and horn combination exhibits inherent high frequency roll-off. This is compensated at the passive filter network in passive systems, while active ones (with no passive network elements) take care of the correction at the electronic crossover.

What is sensitivity?
Sensitivity is the sound pressure level (SPL) which is measured at a distance of 1 metre in front (on-axis) of a loudspeaker which is fed 1 watt of electrical power. If the measurement uses a different distance or power, the result is scaled so that it refers to the standard 1W/1m.

What is this excursion thing then?
(You can put the sun lotion and Swiss army knife down for now). On a cone or diaphragm, excursion is the movement outward and back or from the voice coil rest position. It is inversely proportional to frequency, so that low frequencies generate more movement than high frequencies. Over-excursion takes place when excessive movement causes scratching or deforming of the voice coil, or even fracture when the coil support "bottoms-out" and hits the speaker's bottom plate. To prevent damage, avoid equaliser gain on frequency ranges below a speaker's operating range (such as 20 Hz on a SUB218, or 40 Hz on a Factor -5), use a high-pass filter and be careful when utilizing large power amplifiers.

Why is ther no sound from the audio system?
Cause: The power plug of one or more sound units or effects not connected properly when the audio systems are connected in series.

Solution: Check the connection power panel making sure of the right connection.

Why is there a “Clicking” from audio system between changes?
Cause: soldered connection breakage and loose connection on the system units, causing signal intermittence

Solution: • 1.Check connection of each unit thoroughly, may require re-soldering of joints and connection

• 2.Because of broken connection the “Click” still occurring after checking each connection thoroughly. Check each lead by multi-meter, and replace any broken cable.

Why is there a Severe Power hum when audio system is muted?
Cause: Grounding problem of shielded line!

Solution: Check the shielded line connection at input, May require re-soldering

Cause: Connecting the units three-prong power plug with the jack of two phase input. poor connection of hot wire and ground.

Solution: Reverse the front line and grounding of the jack of the two- phase input. Normally, left is front line, the right is ground. Using three- prong flashboard, the upper prong should be connected with ground line for safety.

Cause: Some audio systems use two prong plug some equipment must use three prong plug, causing hum!

Solution:Reverse the power plug of loudspeaker and two-prong plug.