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Here is all you'll ever need to know when building a subwoofer box
While it is always a pretty good idea to stay away from perfect cubes, they don't necessarily have to be avoided like The Plague. Due to the very small dimensions of most mobile subwoofer enclosures, there is little chance of generating standing waves in the enclosure (standing waves cause nasty response fluctuations). For a standing wave to exist, the distance between parallel boundaries must be 1/2 the wavelength of the frequency at which the standing wave exists. Considering that sub-bass waves vary from 56.4 feet (20 Hz) to 11.28 feet (100 Hz), the generation of a standing wave is going to be impossible....after all, the enclosures we're speaking of have to fit in the average sedan or hatchback!
Any standing waves that might be generated by upper ordered harmonics (caused by distortion) in the enclosure can be readily absorbed with the addition of damping material such as polyfill (available at your local cloth store--it is used to stuff pillows and quilts) or Fiberglastm (the pink stuff) and/or they can be broken up with strategically placed bracing within the enclosure.
In short, don't worry too much about shape. Make the box to fit the space you can allot to the enclosure and forget about it--there are more important things to worry about...like bracing.
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How To Buy A Power Amplifier
Why add an amplifier?
You may think of a power amp as the key to the cranking power that lets
people hear you coming, and while that can certainly be true, there's so much
more to the story. 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 all volume levels. So whether you jam to Pavorotti or Pink
Floyd, whether you run your system wide open or softly enough for
conversation, a well-made power amplifier will breathe life into your music,
bringing out all of its excitement and detail.
What features should you look for?
If you plan to drive a subwoofer with your system, choose an amplifier with a bass boost circuit and a built-in
crossover. A bass boost circuit pumps up the lowest tones, providing extended deep bass impact. A low-pass
crossover sends only bass notes to your subwoofer. And a high-pass crossover relieves smaller speakers of the
burden of trying to reproduce low bass tones they weren't designed to handle. As a result, those speakers can
play louder with less distortion.
How can you add an amplifier to your factory radio?
Even though most factory-installed radios lack preamp outputs, it's easy to introduce your factory stereo to some
real power. Just choose an amplifier with speaker-level inputs. These models allow you to use the existing factory
speaker wires in your vehicle to route the signal into the amp. But don't despair if the amplifier that really turns
you on doesn't have speaker-level inputs. Crutchfield offers inexpensive, easy-to-use line output converters which
let you hook up any amplifier to just about any stereo.
What size amp do you need to make subwoofers really slam?
If you plan to drive subwoofers with your amp, choose one with plenty of power. Low bass notes are power
hungry, and the more wattage you feed them, the better they sound. In general, the larger your subwoofer and the
harder you want it to hit, the more power you'll need. Remember, if you're driving one sub, you can "bridge" a
2-channel amp to get a significant increase in output.
What advantages do you get from an electronic crossover?
An electronic crossover lets you vary the crossover points to achieve the best overall sound in your vehicle.
You'll also enjoy independent level control for the different speakers in your system. You can use this feature to
help achieve better stereo imaging and soundstaging by giving the front speakers or tweeters just the right amount
Where can you mount your amp?
Since space is at a premium in most vehicles, it's important to find just the right spot to mount your amp. Our two
favorite locations are under a seat or in the trunk. Under-seat mounting is space-efficient and keeps the amp
hidden from view. It also lets you run shorter cables from your receiver. A trunk-mounted amp requires longer
power and signal cables but is safely hidden and closer to rear speakers and your subwoofer.
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