Subwoofers ... does it sink or swim ???

[Vanquish]

Subwoofers are larger drivers that are used to create the frequencies around and below 100Hz. Ordinary loudspeakers are unable to effectively produce frequencies in this range due to size limitations of the driver. Subwoofers are generally considered speakers of 8" or larger and will require more amplifier power than coaxial or component loudspeakers due to their larger size. Subwoofers will also require an enclosure to produce these lower frequencies effectively. Sometimes the enclosure can be as simple as the trunk of a sedan or as complex as a series-tuned dual-reflex band pass enclosure. The cone size and enclosure required will be two very important factors when deciding on a subwoofer for your system. There are several manufacturers that offer non-typical subwoofer applications. Examples are the tube type subwoofer and the vehicle specific subwoofer system. Tube subwoofers are cylinders (tubes) with one end containing the subwoofer and the other end sealed. These are a fairly common way of adding a subwoofer to a limited space application or a leased vehicle and come in self-amplified varieties as well. Vehicle specific subwoofer systems are usually built from wood and fiberglass and are designed to fit snugly into a factory void or pocket. Because they are specific to one vehicle they are more expensive then either a standard box or tube configuration. However they can’t be beat for fit and use of space. One final note when purchasing a subwoofer. Determine how much space you are willing to give up and then decide what subwoofer you want. You don’t want to decide you want two 15” woofers and then realize they won’t fit in your Geo Metro after you're out of the store. Be realistic about your goals for the system and the space you are willing to sacrifice to achieve those goals. If you want strong bass but have limited space, add more power to your subwoofer system. Aspects and features that need to be considered when purchasing subwoofers are: Enclosure Type: This is the type of box or enclosure your subwoofer will be mounted in. The main types are infinite baffle, sealed, vented (ported), and bandpass.Power Handling: This is the amount of power a speaker can withstand before failing after a given amount of time. The most important number is the speakers continuous or RMS power handling. Peak power handling means virtually nothing.Sensitivity: This is a reference measure of how loud a speaker will be with a certain amount of power at a certain distance. The standard is one watt at one meter. By halving the distance an increase of six decibels will be realized and doubling the power will increase the output by another three decibels. This is a trick used by some companies to make their speakers appear more efficient than they are. Most loudspeakers will be in the ninety decibel range. Keep in mind that a difference of three decibels is equivalent to a doubling of the amplifier Note : Please remember to check the sub type from the voice coil point of view. A double voice coil sub DVC generally offers more wiring flexibility and configuration set up. For example, a DVC 4 ohm sub can be wired to present either a 2 ohm or 8 ohm load to an amp. A DVC 2 ohm sub on the other hand can be wired to a 4 ohm or 1 ohm load. Here's a close up pic of a subwoofer ... the stunning Image Dynamics IDMax.

 

[Vanquish]

Various types of sub enclosures.

The simplest enclosure type is an infinite baffle or free air system. Note: Free-Air™ is a trademark of Stillwater Designs (Kicker) In this system the woofer has the front of its cone isolated from the back of its cone by mounting the woofer to the rear deck or on a board placed across the back of the rear seat.

Advantages of this design include simplicity, minimal occupation of space and lower cost due to not having to have a box type enclosure.

Disadvantages of this design are a larger power requirement, difficulty (sometimes extreme) in completely isolating the two sides of the cone from each other, and slightly less accurate sound reproduction.

The simplest box type system is a sealed enclosure. Here a woofer is mounted in a completely sealed box that isolates the front and rear waves of the woofer.

Advantages of the sealed design include ease of assembly, more lenient box size requirements, excellent transient characteristics, high power handling, and a typically smaller enclosure.

Disadvantages are less efficiency (requires more amplifier power) than vented enclosures and less low bass as compared to a properly tuned vented enclosures above the port tuning frequency.

Vented enclosures are similar to a sealed enclosure in design except that they add a “port” that is a certain length and a certain area around. This port, usually a length of PVC pipe, is tuned to a certain frequency by variation in the two parameters of area and length. By adding this port, the rear wave of the cone motion is used to reinforce the front wave. When done properly the subwoofer system becomes more efficient than a comparable sealed enclosure above the port's tuning frequency. However, below the port tuning frequency the woofer will become unstable and "unload" causing the woofer to oscillate violently, leading to premature woofer failure when driven with excessive power.

Advantages of this design are increased efficiency and a lower frequency extension above the port tuning frequency.

Disadvantages are a more complex design, a larger enclosure as compared to a sealed design, lower power handling, and slightly less transient accuracy.

The most complex design of the common enclosures is a band pass system. The purpose of the band pass system is increased efficiency over a small range of frequencies. This design also helps filter out unwanted midbass and upper frequencies. There are variations on the band pass design known as orders. The simplest design is the single reflex (4th order) in which a woofer in a sealed enclosure fires into a vented enclosure.

Credits : caraudiohelp.com / mobileaudio.faq / the12volt.com

 

[affan66]

Here's a picture of a tube subwoofer, for those who are saving space for other stuff like prams/strollers/golf bags.

This pic is from my car and the sub is a Bazooka RS-10 incher. OK sub la but won't rattle your balls or shake the boobies. The sub goes down to about 40Hz.

The amp is a 6 channel (Audio Twister), with 2 channels powering the tweeters, 2 channels for the mids and 2 for the sub. I am running active, with time alignment.

 

[skar19]

This thread has been edited and will be used as an 'Introduction to ICE' reference for everyone. The information is usefull and its worth the reading. Enjoy.

Thank You

-The Moderator