Speakers and the amplifier on a decoder are rated by Watts of Power and Ohms of Impedance. It is very important to try to match this. A mis-matched configuration will definitely affect the volume and could fatally damage the decoders amplifier.
Watts of Power
The Watts of Power rating for current production decoders varies by manufacturer and model. It is best to review the specs for your appliction to be sure what your decoder is rated at. Most are rated at 1 Watt. This will be the basis for our discussion.
Matching the wattage of the speaker to amp is important because a mismatch can cause poor sound quality and premature failure of the speaker.
In general, a higher the wattage will produce a louder the installation. That's why the rock stars want more power. What was it Terrible Ted said... "If it's too loud, you're too old"...
The actual value of wattage delivered to the speaker is determined by the rating of the amp, the wiring circuit, and the volume setting for playback.
A 1.0 watt amp will deliver 1.0 watts to a single speaker when the volume is set to 100%.
A 1.0 watt amp will deliver 0.5 watts to a single speaker when the volume is set to 50%.
Multiple speakers affect this calculation even further. There are a number of sites on the web that discuss the formula for calculating this. I like to leverage the knowledge of the web and have found an easy way to do the math. Read on...
Ohms of Impedance
The Ohms of Impedance rating for current production decoders varies by manufacturer and model. Again, it is best to review the specs for your appliction to be sure what your decoder is rated at. Most are rated at 8 Ohms. This will be the basis for our discussion.
Matching the impedance of the speaker to the amp is important because a mismatch can cause poor volume and premature failure of the amplifier.
In general, a lower impedance will produce a louder installation. But be careful! This is also the quickest way to smoke the amp. If the impedance is too low, it will over-drive the amp and cause rapid failure. The high road here is to be equal to or higher than the actual rating of the amp.
Mark Roach used the excellent analogy of a light bulb to describe the matter. At 6 ohms, you are going to stress the audio amp. It is designed to work optimally with an 8 ohm load. If you put less than the rated [impedance] on the amp, it's going to start working too hard. Sure, you will get a bit more volume, but for how long ? It's kind of like a 12 volt bulb. It's designed to work optimally at 12 volts. It will still work at lower voltages, but with diminished light output. It will also light at 14 volts and be even brighter than designed, but the bulb will be stressed and its life severely limited.
