How To Choose Car Subwoofer - Part 2

The best of the new subwoofers are alluminum subs. I use a single aluminum Audiobahn 12" in my Pathfinder off of a Kicker amp, and I love it. The sound quality that it gives me is very clean and smooth. The surrounds around the voice coils are usually rubber. Other brands may use other types of surrounds, but rubber is still the most commonly used and most durable.
-Voice Coils-
*The more layers and space that you have, the better sound quality you get. There are two kinds of bass, clean bass and "ghetto bass". Clean bass subs include brands such as Nakamichi, McIntosh, Blaupunkt, Audiobahn, Infinity, and other higher end brands. They usually have dual-voice coils and give very clean bass. There are also such things as "ghetto subs" which can handle enormous amounts of power, such as 1000 Watt+ RMS, but their bass is very dirty and distorted, it's not good for real music. I've seen very expensive subs that have quadruple voice coils (Sony Mobile ES), but a majority of the high quality subs will have dual-voice coils, but you can definitly do with one.
-Driver Sizes-
*Well, as you can see, in the car an 8" sub will make the car vibrate and do everything that someone would want a subwoofer to do. However, the larger the subwoofer, it can get: Louder, cleaner, hit lower frequencies, and handle more power. If you've got a tight budget, an 8" will do the job, but if you're an audiophile or are really into music, then bass is would be very important to you. I think the ideal size for any subwoofer is 12" because it can hit the lowest notes without using all that much power. A 12" can certainly reach lower notes than an 8". If you can hear the difference in frequencies or need that "bang", then you should get a larger subwoofer. However, if you just want to fill in some lower notes but aren't expecting that much, then go for a 8" subwoofer or something like that. It would save you money.
-Amps and Power-
*The power of your amp should depend on the size of the driver or how much bass you want. I use a fairly powerful amp to power my Audiobahn. I know people that are car stereo crazy, and they power over 1000 Watts to some of their subs, but that is over-kill. It can break the glass on a car, and if the subwoofer is poorer quality, there is a huge amount of distortion. You should never exceed the RMS rating on your drivers, because one day your sub will go "pop!", and there will be nothing left. I think something around 200 Watts per driver should be enough for most people. Most amps that have much more power than that are over-kill I think.
-In Conclusion-
*I hope that this review has helped you in finding the perfect subwoofer for your car. If you have trouble finding the right brand or anything, just look up consumer reviews or get advice from friends. My personal advice is that Audiobahn or Blaupunkt are both superb brands and you'll definitely get a lot for your money. But, most brands will make consumers happy. Well, good luck!

How To Choose Car Subwoofer - Part 1

How To Choose The Right Car Subwoofer The Bottom Line Read this review to find out how to choose the right subwoofer(s) for your car. Choosing a subwoofer can be a very difficult but interesting task. When you're choosing a car sub, you need to know what you really want. It depends what kind of music you listen to, and other factors. -Your Car Is Not A House-

*I have heard subwoofers in big rooms in houses. The subs for example were 8", and the rooms were large. The bass was terrible because it wasn't able to fill the room or anything. The vibrations and everything that the sub had to do was not there. The car is a completely different environment. Bazooka makes popular subs, and a lot of people buy their 8" amplified tubes, I have heard these tubes in Jeep Wranglers and in a lot of SUVs, they can make the cars shake and vibrate, and get people to stare.
Car subwoofers can also be as small as 6.5"... So as you can see, the bass reflects of more areas in a car, thus giving a drastically improved bass response because the smaller area. So you don't need to get a 10" or 12" necessarily to get your car to vibrate. -Tubes VS. Box Enclosures- *Tubes - The only brand that makes tubes is Bazooka. Many of the tubes have built-in amplifiers, they are easy to move, and they are quite inexpensive. They are popular because of their simplicity and price. These will create bass, but not the cleanest or lowest hitting bass out there. So if you're into music, then these aren't for you. If you want something to just pound, then these are quite good. However, you can do better with box enclosures.

*Box Enclosures - Box enclosures are when you buy either a ported or sealed enclosure, and put in however many drivers the box can hold. You can get one that holds either one, two, or three. Many people uses sealed enclosures because they are the smaller one of the two, but I use a ported in my car. Unlike tubes, with boxes, you can add whichever brand of woofers you want, and your own amplifier. However, this can be a more difficult task than just putting in a tube. But, you get much more versatility. Whether you're setting up a budget or audiophile sub hook-up, a majority of the people will use box enclosures. -The Different Materials-

*Different subwoofers are made out of different materials. Many of the more inexpensive and common subs are built out of paper cones. These will generally handle the job well, but there will be more distortion, but the price difference is quite large. Polypropylene is becoming quite of a popular polymer, it is higher quality than paper, and still quite inexpensive.

Non-circular subwoofers

Within the last few years, car audio has seen a few subwoofers using non-circular shapes from manufacturers such as Kicker, Sony, Bazooka, X-Tant, etc. There is no audible advantage to these shapes, and they may carry some distortion penalties. They can, in some situations (limited mounting space, for instance) give a slightly greater cone area and so slightly higher output at low frequencies. The intent of non-round subwoofers is to increase the surface area of the cone. In enclosures of a particular size, more subwoofer cone area is possible with some of these shapes, although the difference may be trivial. The increased cone area moves more air, producing higher sound pressure levels. However, these drivers are not optimized for maximum output level, so the advantage is largely theoretical. The effect of corners in their surrounds is to increase distortion.

An important factor in the "square sub vs round sub" argument is the effects of the enclosure used. In a sealed enclosure, all displacement is determined by

where V_d stands for volume of displacement, x_max to the amount of linear excursion the sub is mechanically capable of (in mm), and S_d to the cone area of the subwoofer (in cm²). These are some of the Thiele/Small parameters which can often be found in the owner's manual or driver specifications. Because of the multiplication, excursion is as important as cone area to generate SPL. However, the importance of these parameters shifts if the subwoofer is used in a ported enclosure. When a subwoofer produces frequencies near the tuning frequency of the ported enclosure, excursion decreases and cone area becomes more important.

Car audio

Automobiles are well suited to the "hidden" subwoofer approach due to space limitations in the passenger compartments. It's not possible, in most circumstances, to fit such drivers and enclosures into doors or dashboards. In addition, there are acoustic problems in most car interiors (e.g., too reflective, too small, too noisy at many frequencies, ...). Typically, subwoofers are installed in the trunk or back seat space.

Some car audio enthusiasts compete to produce very high sound pressure levels in the confines of their vehicle's cabin; sometimes dangerously high. The "SPL wars" have drawn much attention to subwoofers in general, but subjective competitions in sound quality ("SQ") have not gained equivalent popularity. Top SPL cars are not able to play normal music, or perhaps even to drive normally as they are designed solely for competition.

Even normal consumer-grade subwoofers are often capable of generating exceptionally high levels in cars due to the small volume of the typical car interior. High sound levels can cause hearing loss and tinnitus if one is exposed to them for an extended period of time.

Since much bass is felt, sub-bass can be 'augmented' using tactile transducers. These have recently emerged as a device class, called variously "bass shakers", "butt shakers" and "throne shakers". They are attached to a seat, for instance a drummer's stool ("throne") or gamer's chair or car seat, and the vibrations of the driver are transmitted to the body then to the ear via bone conduction. They connect to an amplifier like a normal subwoofer. They can be attached to a large flat surface (for instance a floor or window) to create a large low frequency conduction area, though the transmission of low frequencies through the feet isn't as efficient as the seat. The advantage of tactile transducers used for low frequencies is that they allow a listening environment that isn't filled with loud low frequency waves. This helps the concert drummer to monitor his or her kick drum performance without polluting the stage with low frequency waves from a subwoofer monitor. Bass shakers help the user avoid disturbing others nearby and help to augment the headphone listening experience. However, some feel that the felt vibrations are disconnected from the auditory experience.

Professional audio

Professional audio subwoofers must be capable of very high output levels. This is reflected in the design attention given in recent years to the subwoofer applications for sound reinforcement, public address, and concert systems. Consumer applications (as in home use) are considerably less demanding due to much smaller listening space and lower playback levels. Subwoofers are now almost universal in professional sound applications such as live concert sound, churches, nightclubs, and theme parks. Specifically, movie theatres certified to the THX standard for playback always include high capability subwoofers. Some professional applications require subwoofers designed for very high sound levels, using multiple 15", 18" or 21" drivers. Drivers as small as 10" are occasionally used, generally in horn loaded enclosures.

People accustomed to bass in home audio systems and car audio may think the subwoofers in a concert system don't have much low frequency output, since the human ear recognizes loudness (ie, sound pressure) logarithmically. Concert subs can be 10 times the power rating which equates to 10 more deciBels, but will only be twice as loud. Sound intensity obeys the inverse-square law in relation to distance from the source, and at outdoor events the crowd is many metres away from. The human ear is less sensitive to sound at lower frequencies, so very high levels are needed to hear 20 or 25Hz sounds.

The main speakers may be 'flown' from the ceiling of a venue on chain hoists, and 'flying points' (ie, attachement points) are built into many enclosures. Since subwoofers are larger, heavier, and least localizable components, they can be stacked on the ground near the stage. These enclosures may contain several 18-inch drivers, and the enclosures are typically built from Baltic Birch, sourced from Finland, Estonia or Russia. This material is void free, has many plies, and is exceptionally durable. There can be more than 50 double-18-inch cabinets in a typical concert system.

Subwoofers may or may not be fed with signal from the main program mix, instead having kick drum, bass and keyboards routed to them. This avoids the low frequency 'drone' of feedback that can occur if the vocal microphone signals are reproduced by to the subwoofer system. Some concert sound companies use subwoofer systems made by the same manufacturer of the flying speakers, but many others select subwoofers from other manufacturers, better suited to their truck-pack, cost, or other criteria.

Servo subwoofers

Some active subwoofers are also servo controlled, using a feedback mechanism which generates a signal based on the movement of the cone. The signal is used to correct for any deviations from the motion intended. Several manufacturers make servo subwoofer systems, usually accelerometer-based. The advantage of servo subwoofers is reduced distortion. The primary disadvantages are cost and complexity. A successfully implemented servo system addresses the limitations of conventional subwoofers:

• mechanical non-linearities
• thermal non-linearities
• magnetic non-linearities

Active and passive

Generating high output at low bass frequencies is a demanding task, so the driver, enclosure, and amplifier are designed to work together as a package. These subwoofers with a built-in amplifier are called Active or powered subwoofers. The amplifier in these units have built in crossover, phase, and sometimes equalizer capabilities.

Some amplifiers include an adjustable low-pass crossover, which limits the range of the subwoofer to low frequencies. For example, if a listener's main speakers are usable down to 80 Hz, then the subwoofer crossover can be set so the subwoofer only works below 80 Hz. The crossover section may also include a high-pass "infrasonic" filter that prevents the subwoofer driver from reproducing frequencies below its capabilities. The subwoofer phase control allows a listener to adjust the phase (time) alignment of the subwoofer system relative to the main speakers. Doing so eliminates or minimizes the acoustic cancellation between the subwoofer system and main speakers, the result of them not being in phase within the crossover region as heard at the listener's ear. Phase settings may be a two-position switch (0° or 180°) or a continuous adjustment between these two values.

Some subwoofers are built with their own internal amplifier. Designers of this type can add a degree of corrective equalization to ensure optimum performance. Some also include a user-adjustable equalizer that allows boost or cut output at certain frequencies, and these vary from a simple "boost" switch, to elegant parametric equalizers for detailed speaker and room correction. Some even include a calibrated microphone to measure the subwoofer's in-room response, so the automatic equalizer can correct the response to some pre-determined performance.

Passive subwoofers have a subwoofer driver and enclosure, but do not include an amplifier. They sometime include passive crossovers inside, with the filter frequency determined by the factory. These are used with third-party power amplifiers, taking their inputs from active crossovers earlier in the signal chain. While few home-theater-in-a-box systems use passive subwoofers, this format is still popular in the professional sound industry.

Overview

Subwoofers use drivers (woofers) (typically between 8" and 18" in diameter) , but some have been as large as 60". Some drivers as small as 4" may be referred to as subwoofers but drivers less than 8" generally have neither the cone area nor excursion ability necessary to produce deep bass, especially in practical sized enclosures. The most common subwoofer sizes in professional audio are 12", 15" and 18".

All loudspeakers characteristically exhibit trade-offs between frequency response and response time (transient response) depending on the characteristics of the voice coil, properties of the magnetic motor, the cone mass, and the nature of the enclosure. While cone size and voice coil inductance are major factors, a recent study indicates that the role of inductance is more important than was previously believed. The effects of the cone mass are not significant at sub-bass frequencies.

With the advent of the CD, the demand to reproduce deep, clean, loud bass increased, and had increased again with the introduction of digital audio Surround sound formats like Dolby Digital and DTS, which make extensive use of subwoofers for special effects. In modern music, the subwoofer 'channel' is often used aggressively by producers to enhance the listening experience.

Subwoofers are available in several formats, including bass reflex, acoustic suspension, infinite baffle, horn loaded, tapped horn and bandpass types. Each enclosure topology design has advantages and disadvantages in efficiency, bass extension, and cabinet size. Bass-reflex enclosures are the most common type in domestic hi-fi and professional sound.

The fundamental difficulty for subwoofers is to couple the motion of the cone to the listening environment, while limiting cone excursion to safe levels, cooling of the voice coil, while minimizing distortion, and maximizing output. Since the human ear is increasingly insensitive as frequencies decrease, these requirements are hard to meet simultaneously.

Subwoofer

A subwoofer refers to either a woofer, or a complete loudspeaker dedicated to the reproduction of bass audio frequencies, typically from 150 Hz down to 20 Hz. In the case of a rotary woofer, it is possible to reproduce frequencies down to 1 Hz. Bass frequencies below about 80Hz become increasingly difficult for typical floorstanding or bookshelf loudspeakers to reproduce at high playback levels (100 dB or more) because they do not have large enough drivers to generate the required amount of air displacement. Therefore, subwoofers are useful for augmenting main loudspeakers by providing playback of low bass frequencies at high levels.