Registered: 18th Sep 03
Location: Anglesey, North Wales
User status: Offline
Why do I need an amplifier?
Adding an amplifier gives you a clean power source that can drive your speakers without straining. That means your music will sound cleaner and more defined at higher volumes. A good quality amplifier will breathe life into your music and hopefully make your journey less of a task.
How much power do I need?
When choosing an amplifier, the RMS (root mean squared) rating is the power rating you should pay most attention to. Stereo manufacturers often display peak power ratings on their products. The peak power rating tells you the maximum wattage an amplifier can deliver as a brief burst during a musical peak, like a dramatic drum accent. The RMS figure is much more significant.
The RMS power of an amp is usually less than half of the peak power. For example, an amplifier rated at 100w (peak) per channel would be about 40w per channel RMS. Big difference, isn't it? Be careful when checking specifications of amps before buying, to see what you are really getting. Always ask for the RMS power of an amplifier.
For mids and highs, anywhere from 30 to 50 watts (RMS) per channel would be a minimum. For subs you would need at least 80 - 150 watts (or more) per subwoofer. There should always be more power going to the subwoofers than the rest of the speakers, since human ears are more sensitive to higher frequencies than lower. For example, if you have 4 x 50 watts going to all your mids and tweeters (total=200 W), then you should have at least 200 W or more going to your subs.
A lot of people wonder if too much amplifier power can burn up the speakers. What damages speakers most of the time is distortion, not power. If the speakers have the proper crossovers and are not distorting, then it is really hard to blow them. A bigger amp just gives you the opportunity to go to higher volumes without distortion. Get the biggest amplifiers you can afford and your car's electrical system can handle. More power means louder sound, but most importantly, cleaner sound.
How many channels do I need?
If you are planning to drive more than one pair of speakers from the amp then you are better off going for a multi-channel amplifier, rather than buying a separate amp for each pair of speakers. Multi-channel amplifiers are usually a lot easier to build in to a system because you have one set of inputs, ont set of power wires etc. instead of wiring for each amp. The downside of course, is that your system is then more difficult and expensive to upgrade as you can't, for example, just add more power to your sub.
If you plan to drive subwoofers with your amp, choose one with a built-in low-pass (nb. allows lows to pass) crossover which sends only bass notes to your subwoofer.
Remember, if you're driving one sub, you can "bridge" a 2-channel amp to get a significant increase in output. Not all amps support this.
[Edited on 23-04-2005 by Ian]