June 2010 Ask the Pro: Speakers
Here are some frequently asked questions by churches regarding speaker systems.
How do I choose the right amplifier power for my speaker system?
A quality professional loudspeaker can handle transient peaks in excess of its rated power if the amplifier can deliver those peaks without distortion. Using an amp with some extra "headroom" will help assure that only clean, undistorted power gets to your speakers. Some professional amplifiers are designed so they have additional headroom. These amps can cleanly reproduce transient peaks that exceed the amplifier's rated power. In this case, select a model with an output power rating equal to the continuous IEC power rating of the speaker.
If budget restraints or legacy equipment force you to use an amplifier with less power, extreme care should be taken to see that the amplifier is not driven into clipping. It may surprise you to learn that low power can result in damage to your speaker or system.
What makes speakers fail?
The speaker surround and spider, known collectively as the "suspension," must be flexible in order to accommodate the excursion of the cone or diaphragm. At the same time, they have to keep the cone or diaphragm from tipping or becoming "de-centered". Suspensions can fail due to environmental factors such as exposure to heat, UV rays, or humidity. It is also possible for the adhesives that attach the suspension to the cone and the speaker basket to fail or to be improperly applied at the time of manufacture.
The separation of tinsel leads is also a common failure. Conducting the electrical signal from the speaker terminals to the voice coil is the job of the tinsel leads. The leads must be light, flexible, and immune from breakage due to fatigue. At the same time, the leads need to be able to carry the full rated current load of the speaker.
What is Signal Burn?
What is DC Burn?
Woofers: When a DC burn pattern appears on the voice coil of a woofer, the problem will be due to a fault in the associated electronic equipment. Most likely, the power amplifier has leaky or shorted transistors that are allowing its internal power supply voltages to be applied directly to the loudspeaker or loudspeaker system.
Midrange and Tweeter: When a DC burn pattern is observed on the voice coil of such devices, it does not always mean that the amplifier is faulty. In systems with passive crossovers, mid and high frequency drivers are protected from DC by the cross-over. The most likely cause of DC-like burns is an overdriven amplifier.
When an amplifier receives an input signal capable of driving it beyond its power rating, the result is clipping. This means that the negative and positive peaks of the amplifier's output.
Should I fuse my speakers?
What is power compression?
How do I select the correct wire gauge for my speakers?
This information is courtesy of JBL Professional, www.jblpro.com.