How to Interpret Basic Loudspeaker Specifications
Have you ever bought a pair of loudspeakers from someone in a van? Well, someone I know did and this is how it was explained to me.
He said while at the traffic light, a man driving a van asked him if he would like to purchase some loudspeakers. After a brief exchange of words, the man asked him to pull over. The man then told a story of too many loudspeakers being shipped to him for a contracted installation. The asking price for the loudspeakers was $300/pair, after some conversation my fellow engineer asked for some qualifications, the man looked around then came to the conclusion that he forgot it somewhere. A presentation of the loudspeakers were made and my fellow engineer, impressed with the presentation, decided that a good price for the loudspeaker was $200/pair. A short time later after an ATM withdrawal, the man was off with $200 and my fellow engineer has a pair of loudspeakers. We can go on discussing the error of this transaction forever, but let us focus on the basics about loudspeakers specifications that will help in the future.
Step 1 To protect yourself against potential disappointment is to understand (even at a very basic level) the information being presented to you (this goes beyond loudspeakers). While some sales person can speak knowledgeable about their products, I have encountered many that either misrepresented products or was misinformed.
Step 2 Have an idea what you would like to purchase, impulse buying is not recommended. When you go to purchase loudspeakers the sales person is prepared to present their products, therefore it is only necessary for you to be prepared to purchase what you need not what you can be sold.
Power HandlingMost often, buyers tend to look at the power handling (in watts) of the loudspeaker, the larger the number the more impressed they are. Generally, power handling is published as Peak, Program or Continuous power. The Peak power is the power the loudspeaker can handle for a very short period (envision 1 beat). This rating should be divided by 2 to get a rough idea of the average (closer to the sound signal of a song) power handling . The Program power rating is based on a simulated audio signal ( similar to music) and gives a better idea of actual power handling. The Continuous power rating is based on a periodic sinusoidal signal (sine wave etc.), this is the power the loudspeaker can withstand without overheating. Continuous rating is usually the worst case scenario, this is the safest of the loudspeaker power handling ratings.
Frequency ResponseThe frequency response of loudspeakers is very important, it gives an idea how uniform loudspeakers reproduction of the original sound will be. The frequency response is specified in two parts, the range and the tolerance. The range specifies the frequencies that are covered by the loudspeaker and the tolerance specifies maximum deviation (usually + or - 3dB) from the average output level. I often see the range specified without the tolerance, the range by itself is useless, even + or - 6dB tolerance is acceptable in some cases.
SensitivityThe sensitivity of a loudspeaker gives the output level (usually dBSPL) for a given input (usually watts). Manufacturers often specifies the output level of their loudspeakers at a distance of 1 meter on axis while the input power is 1 watt. The sensitivity of loudspeakers can be used to determine the output level (how loud) the loudspeaker for a given amount of amplifier power (within the power handling range of the loudspeaker). To increase the output of a loudspeaker by 3 dB requires doubling the input power. For example, if two loudspeakers, A and B are rated under the same conditions at 96 dBSPL and 99 dBSPL respectively, for loudspeaker A to play as loud as loudspeaker B it would require twice as much power. Everything else being equal, the loudspeaker with the greater sensitivity will product a higher SPL level.
The above information is a good start to help in the interpretation of loudspeaker specifications. Good luck and happy shopping!
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