Amplifier Power

Don't judge a book by its cover and don't judge a home audio subwoofer by its amplifier power.

The amplifier power produced by a subwoofer amplifier(either mounted to the subwoofer enclosure itself or as a stand alone component) is an important indicator of the performance potential of the system(complete subwoofer). However, we need to keep a few things in mind when examining the individual components that make up a complete home audio subwoofer.

A driver may perform significantly better than its "specs" indicate it should and the same goes for the amplifier. We'll talk more about the driver in an upcoming "tip of the day". For now, let's focus on the amplifier. If we have two different subwoofers and subwoofer *A* has a 500 watt amp and subwoofer *B* has a 1500 watt amp....subwoofer B is probably the better performer....right? Not necessarily. Even assuming both amplifiers are accurately rated by the manufacturer we still need more information about the system design. System efficiency is largely determined by the subwoofer enclosure size. A small 14" cube subwoofer(about 1 cu-ft internal space) for example will produce significantly less output PER / WATT then a larger enclosure(say 4-5 cu-ft). The differences between these two enclosure sizes will often be in the 10dB range. This means the small cube would require 10(ten) watts to produce the same amount of bass the larger subwoofer does with 1(one) watt. That is quite a difference and only appears more dramatic as we increase the volume levels even further. For example, the small cube will require 1000 watts of power from its amplifier to produce the same amount of bass the large subwoofer does with just 100 watts. The same 10:1 ratio will hold true for all output levels in this specific example.

If we apply this same ratio to my original example we can see that subwoofer *A* will only need to produce 150 watts to match the maximum output potential of subwoofer *B* even though the latter has a 1500 watt amp! The 500 watt subwoofer will essentially be coasting along with plenty of headroom to spare when the 1500 watt example is "maxxed out".

So although it is often interesting to examine individual components in a home audio subwoofer the main point of interest should always be the system performance as a whole product.

Tom V.
Power Sound Audio

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