Dom's Car Audio Page
Sign My Guestbook
View My Guestbook
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.
Bracing and Strength
Of all the things to worry about when constructing an enclosure, this is probably the most critical element. If an enclosure cannot adequately contain the tremendous amounts of pressure generated by today's high-powered subwoofer systems, the results will be marginal bass quality at best or total destruction of the enclosure at worst.
A flexing enclosure is a lossy enclosure. If the panels on your subwoofer enclosure vibrate, you lose output (SPL) and clarity. The solution is two-fold: use only 3/4" or 5/8" thick medium density fiberboard (MDF) and brace (reinforce) the life out of the box. If MDF (or the brand name Medite) is not available in your area (it can be quite hard to find, but most custom cabinet making shops should be able to supply you with what you need), the only other real solution (barring exotic materials like sheet PVC) is to use a super high-quality plywood like birch or some other marine-grade plyboard. Avoid using particle board at all costs as it is too flaky (literally), doesn't hold screws well and swells like a sponge when water hits it. In short, particle board comes from the Pit of Helltm. Avoid it at all costs.
After the proper materials have been chosen for box construction, the subject of bracing must be addressed. Bracing is very important!
Sealing the Box
Whether you are planning to use a bandpass, ported or sealed box, sealing the edges is very important (isn't everything?). The first step to take in assuring a good tight seal at all joints is to use copious amounts of wood glue. Don't be shy with it--keep a wet rag handy to wipe up the excess. Like bracing, you can never use too much.
There have been some debates on rec.audio.car regarding the use of silicone caulk to seal enclosures since the caustic fumes (acetic acid) released during curing have an appetite for foam surrounds, but with a little understanding of what is going on, this problem can easily be avoided.
Fortunately, most JL Audio subwoofers have a specially treated surround that protects them from hungry acetic acid fumes which is cause #1 not to be overly concerned with using silicone to seal your box. Secondly, the fumes are only released during curing (the time when the caulk goes from a free-flowing gel to an amorphous solid) so all you have to do to prevent damage to the drivers is to wait until the silicone has cured (8-12 hours usually) before dropping the subs in. As one member of the rec.audio.car newsgroup (who shall remain anonymous) can attest, it is not a good idea to stick your head inside the box while the silicone is curing unless you are in search of the world's most obnoxious buzz (don't try this at home kids).
If time is of the essence and you are not (*gasp*) using a JL Audio subwoofer, you might want to look into other sealants that are less caustic.
Go to the ICE Homepage and
get your own free chat!
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
of power.
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.
My Favorite Links
angilefire free web pages
jlaudio online
Free online gaming
mobileaudio.com
Earl Zausmer "The Best page on the web"
The audio-warehouse
Robert's Page
Mark LaFountain's page
Email: dom1416@provide.net
