Subwoofers (FAQ)

From SCION-TECH : The Scion Resource : tC, xA, xB, xD

Contents 1 ALSO SEE 2 GENERAL 2.1 How many subwoofers do I need? 2.2 Where can I install a sub? 2.3 How much does it cost to install subwoofers? 2.4 What sub sounds best? 2.5 Are there any instructions for building a sub box? 2.6 Sub Basics 3 Why add a sub? 3.1 Get Everything You Need 3.2 Which one matches up best to your needs? 3.3 Some key specs to consider 4 Questions 4.1 Which subwoofer will sound the loudest? 4.2 Which subwoofer will sound the deepest? 4.3 Which hits harder: one 12" sub or two 10" subs? 4.4 How much power do I need? 4.5 Should I use a mono amplifier or a multichannel? 4.6 Hooking up 2 subwoofers to a mono amplifier. 4.7 Can I bridge my mono amplifier? 4.8 What difference do cone materials make? 4.9 Are square or triangular subwoofers better? 4.10 What's a dual voice coil sub? 4.11 What about impedance when wiring subs? 4.12 How many subwoofers can I hook up to my amplifier? 4.13 What's Poly-Fill? 4.14 What crossover point should I choose? 5 Glossary 5.1 Basket 5.2 Box volume 5.3 Dual voice coil subwoofer 5.4 Enclosure types 5.5 Frequency range 5.6 Impedance 5.7 Peak power 5.8 Pole Piece 5.9 Power range 5.10 Sensitivity 5.11 Spider 5.12 Surround 5.13 Thiele/Small Parameters 5.14 Top mount depth 5.15 Voice Coil 6 Subwoofer Enclosures 7 Dual Voice Coil Subwoofers

[edit] ALSO SEE

• Amplifier (FAQ)
• Head Unit (FAQ)

[edit] GENERAL

[edit] How many subwoofers do I need?

Anyone really only “needs” 1 subwoofer. Anything more is just for show. Some people buy two lower quality subs thinking they will get more sound from them, when really this is far from the truth. A single high quality 10” subwoofer can and will sound louder and more clear than 2 to 3 lower quality 10’s (or even 12’s!!) If your goal truly is sound quality, spend the extra money on a single sub rather than two of them. However if you feel the need to show off 2 cones in your trunk, then you should still go with high quality subs (high quality does not need expensive!)

[edit] Where can I install a sub?

Space is limited in the Scions, but many people have found very creative ways to get a subwoofer or multiple subwoofers installed.

[edit] How much does it cost to install subwoofers?

The price to have a sub installed is not always crystal clear. There are several factors to account for such as: How many subs? Do you have a sub-box? Will you need a custom sub-box? Do you already have amps installed? Also prices will vary from shop to shop. If you have all the parts (subs, box, wires, amp), then usually you can expect to pay around 100$ for installation of 1 amp and 1 sub box.

[edit] What sub sounds best?

Sub Sounds have more to do with design of the enclosure and the power that is supplied to them. You can spend $500 on a single sub and have it sound horrible if the enclosure is not sized and designed right and/or there is not enough power. As with any other mod, the sub is part of a chain in your audio system and thus should be treated as such. If in doubt post in the audio section of the forum. There are too many subwoofer companies out there to decide on which is the best. Look around and pick some you can afford and are happy with the #’s. Then post in the forums and get other Z owners feedback.

[edit] Are there any instructions for building a sub box?

We have another great tutorial for building fiberglass speaker boxes. Check out these tutorials if you feel like jumping into this project on your own. (more will be coming shortly). Basic Fiberglassing, Subwoofer Box 1, Subwoofer Box Z, MDF Rings, Fiberglassing FAQ

[edit] Sub Basics

A subwoofer by definition is a device designed to produce low frequency energy. It’s ability to produce this energy and the frequency in which it produces it is a function of its cone surface area and it’s Xmax (Linear travel of the cone). The higher the Xmax the more spl a speaker can produce at a given power. The larger the cone area the lower the natural frequencies it can produce. A well-designed subwoofer universally has the following characteristics. First the cone of speaker is stiff enough to minimize distortion during its use while being light enough to require little energy to make it move. Second the speaker must be designed to remove as much heat as possible from the spider area. Thirdly the speaker must be designed to be efficient. Efficiency is one of the most important elements of a subwoofer due to the fact that efficiency directly correlates to the power needed to run the sub, the higher the efficiency the easier it is for an amp to run the sub. There are numerous quality subs on the market today ranging in price from $90 to $900 dollars so it is easier than ever to get a good product. Chose wisely , research heavily and you cant go wrong.

[edit] Why add a sub?

Subwoofers are speakers dedicated solely to reproducing low frequencies. No matter what kind of music you like, or how softly or loudly you like to listen, subwoofers are a crucial part of your overall listening experience. Small car speakers have trouble producing enough low-frequency sound to give your music realism and depth. A subwoofer can make the difference between a good-sounding and a great-sounding system.

[edit] Get Everything You Need

• You'll need an amplifier to drive a component subwoofer.
• If you're buying a component subwoofer, you'll need the proper enclosure.
• A Dynamat kit will prevent any rattles from your sub, while reducing road noise to give you louder, richer bass.
• Poly-Fill box stuffing slows sound waves inside a sub box, making the sub perform more efficiently (and louder).
• If you're going to build your own subwoofer enclosure, you'll need box building hardware.
• You may need an amp wiring kit and speaker wire to send signal and power to a pre-loaded sub box or a sub/amp combo.

There are a lot of different ways to add a subwoofer to your vehicle. Which one is right for you depends on a lot of different factors, including your musical tastes, budget, and how much space you have available in your vehicle.

[edit] Which one matches up best to your needs?

1. I want to pick and choose components to build a truly personalized system.

You should start by looking at component subs. A component sub is just the speaker itself — it'll need to be mounted in a subwoofer enclosure (usually simply called a "box") to operate properly. In addition, you'll need to power the sub with an external amplifier. Component subs usually range in size from 8" to 15". There are models designed to operate on low or high power, and in a variety of different types of boxes. They are several different impedance and voice coil setups, so you can pick and choose among models to match up to your system design. If you're starting from the ground up in designing your custom system, choosing the subwoofer is a great place to start.

2. I want an easy "off-the-shelf" sub/enclosure combo.

Check out enclosed subs. Enclosed subs are pre-mounted into a box designed to accommodate the sub. This eliminates the need to choose an enclosure for the sub, so you won't have to do as much work designing and building your system. On the down side, you'll be limited on the number of speaker and box-type choices you have. You'll still need an external amp to power the sub.

An enclosed sub, like this Visonik bandpass model, is one of many excellent ways to add some bass to your vehicle, and can simplify your subwoofer buying decisions.

3. I want a simple, space-saving bass system.

A powered sub is a great way to go. A powered sub combines an amplifier and woofer in an enclosure. Since the amplifier is built-in, there's only one piece of equipment to find a place for and install. Many powered subs are compact and won't take up a lot of room in your vehicle. While powered subs can be very effective bass producers, their smaller drivers and amplifiers may not provide all the sound power you want if you're looking for really big bass. On the other hand, their relatively simple installation and small size make them a great add-on to factory stereo systems.

4. I want a sub that will blend in with my car's interior.

You're a prime candidate for a vehicle-specific sub, either powered or unpowered. These subs are designed to fit in out-of-the-way locations in many cars, trucks, and SUVs, and are often colored to match the vehicle's interior exactly. Like the powered subs we just talked about, they may not be the best choice if you're looking for really big bass, but they'll more than suffice for most listening needs without taking up a lot of interior space.

5. I want a great bass system, but don't want to sweat the details.

Check out the forums and find out what others are doing.

[edit] Some key specs to consider

Once you've got an idea of what type of subwoofer or system you'd like to buy, comparing specs can be helpful in making your decision. Here are some key specs to consider:

1. Power — If you want a system that really booms, there's no substitute for plenty of power. Pay attention to RMS power ratings, not peak power ratings. RMS ratings measure continuous power handling or output and are a much more realistic measure than peak power. Make sure you match the sub's power handling to your amp's power output.
2. Sensitivity — Sensitivity goes hand-in-hand with power to achieve high output. A sub that has a higher sensitivity rating requires less power to produce the same amount of sound as a model with a lower sensitivity rating.
3. Frequency range — Frequency range gives you an idea of how low a sub can play. Keep in mind, though, that the actual performance of the sub can depend on a lot of variables, like the box type it's mounted in.
4. Enclosure type — The type of enclosure a sub is mounted in will have a big effect on the type of sound it produces. In general, sealed boxes give you the deepest, most accurate sound, while ported and bandpass enclosures produce more volume.
5. Number of voice coils — Dual voice coil subwoofers are a popular choice among car audio enthusiasts who want more flexibility in wiring their sound systems. While typical subwoofers have a single voice coil, dual voice coil (DVC) subwoofers use two separate voice coils, each with its own connections, mounted on one cylinder, connected to a common cone.
6. Size of the woofer — It's a never-ending question — what size subwoofers play loudest and lowest? It's not an easy question — you need to consider sensitivity, enclosure type, and available power. If your ultimate goal is to have a system that plays loud and low, and space isn't an issue, go for the biggest subs. But don't underestimate smaller subs. Properly powered and in the right enclosure, smaller subs can put out plenty of sound.
7. Impedance — Most subwoofers are rated at 4 ohms impedance, but 2-ohm, 8-ohm, and dual voice coil subwoofers have become commonplace. When you've chosen a subwoofer, look for amplifiers that will match up to your sub in terms of power rating and impedance. There are a wide variety of amps available, so you shouldn't have any trouble finding one that will bring out the best in the sub you've chosen.

[edit] Questions

[edit] Which subwoofer will sound the loudest?

If you're looking for the sub that will deliver maximum SPL (play loudest), you need to consider sensitivity, enclosure type, and available power.

Start with a subwoofer with a high efficiency (sensitivity) rating housed in a ported or bandpass box.

Next, power the sub with an amplifier that has a power output that is within your sub's recommended power range (preferably in the top third of that range). You'll achieve the slam you're listening for. Using an amplifier with a "bass boost" control can also help.

Consider a multiple subwoofer set-up, as well. It'll require more power, but will play louder.

[edit] Which subwoofer will sound the deepest?

To experience the lowest possible bass tones, select a large woofer designed for use in a sealed box. This type of enclosure is your best bet for driving your frequency response down.

Ample wattage is also a must if you want to hear those lowest bass notes. A woofer with a very low frequency response spec can help deliver extremely low notes. Additionally, larger woofers, because of their size and excursion capabilities, often have the ability to play deeper than smaller woofers.

[edit] Which hits harder: one 12" sub or two 10" subs?

This is a popular question, and one that's difficult to answer definitively. There are so many factors that come in to play — power, enclosure type and size, as well as your specific vehicle and your individual perception. But, generally speaking, given adequate power the two 10" subs will sound a little cleaner and punch harder because their combined cone surface area yields more sound pressure. The single 12" sub, however, may sound a little deeper.

[edit] How much power do I need?

The right answer to this question depends upon which subwoofer you choose. You'll find a recommended power range (in continuous or RMS watts) listed in the specifications for each subwoofer on this website.

The lower number is the absolute bare minimum amount of wattage you need to get acceptable results. Generally, more power is better because bass notes are power hungry. So, to really make your subwoofer deliver, we recommend choosing an amp rated in the upper third of your woofer's maximum RMS power range.

Your amp's RMS output can even exceed the woofer's maximum RMS rating, provided you keep an ear on the sound quality — when the bass starts to distort or "break up," you've reached the performance limit of your amp/speaker combination. Back the volume knob down a bit, and your woofer is safe; clean, high-volume sound will not damage your speaker.

[edit] Should I use a mono amplifier or a multichannel?

Because mono amps tend to be Class D amplifiers, they are a good choice for powering subwoofers — Class D amplifiers have a high power-to-heat ratio and excellent efficiency, which are exactly what you want when dealing with power-hungry low frequency signals.

Most mono amplifiers are designed to run at 2 ohms; some are even 1-ohm stable. Multichannel amplifiers, on the other hand, are typically designed to work with a 4-ohm load. This is an important difference when using your amp to power multiple subwoofers, because you won't be able to bridge your multichannel, 4-ohm stable amp to power multiple subs that present less than a 4-ohm load. Instead, use a mono amplifier to power a 2-ohm load — two 4-ohm subwoofers, or 2, 2-ohm dual voice coil subwoofers, for example. You'll be able to push your subwoofers with the mono amp's maximum power, without running at a dangerous impedance.

[edit] Hooking up 2 subwoofers to a mono amplifier.

The benefits of hooking up two subs to a mono amplifier are the same as hooking up any other number of subs to a mono amp: you can push the subs with more power at lower impedances. Because lower frequencies are less directional (i.e. it's more difficult for your ears to determine where low frequencies come from than highs), bass is often transmitted in mono. Mono here refers to a single channel (as opposed to stereo, or two channels), not one speaker.

Most mono amps have two sets of speaker terminals for convenience of installation: if you are hooking up two subs to the amp and using large-gauge wire, it gives you a place to attach the wires without having to trim them, appearing as if each subwoofer gets its own terminal. But in reality, these terminals are actually tied together inside the amp — both positives are going to the same place inside the amp, as are both negatives. If you are using more than two subs, then you simply use parallel or series wiring (or a combination) to get as close to the minimum impedance of the amp as possible (see our subwoofer wiring diagrams for more information).

[edit] Can I bridge my mono amplifier?

No, you can not bridge a mono amp because there is nothing to "bridge" to — whatever impedance load you present to amplifier is the actual load that it sees. This differs from a multichannel amp in that when you bridge two channels together, you halve the load presented to them (for example, 2 4-ohm woofers wired in parallel and bridged to a stereo amplifier is "seen" as a 1-ohm load to that amp).

[edit] What difference do cone materials make?

Subwoofer cones, like speaker cones, are made of treated paper, synthetics (like Highly Oriented Polyolefine) or composites (like aluminum or injection-molded quartz). Paper tends to be less durable, but, because it is so lightweight, responds quicker than other materials. All these can sound great; you need to experiment with different sounds (and your checkbook) to find the sub that's right for you.

[edit] Are square or triangular subwoofers better?

"Better" is a relative term, since the bass you prefer might differ from someone else's taste. If you're into imaginative looks and style, square and triangular subwoofers might be for you. They'll definitely catch the eye! These woofers also reproduce bass extremely well (Kicker's square woofers are big on the competition scene), though traditional round woofers tend to play more accurately. The triangle shaped woofers might be convenient if you lack sufficient cargo space, since triangular boxes fit into places where standard design boxes fear to go.

[edit] What's a dual voice coil sub?

A dual voice coil subwoofer has two separate voice coils (each with its own connections), offering more flexibility in system wiring than a standard sub. The DVC sub can be wired in three different configurations: parallel, series, or independent. This way, you can wire the subwoofer according to your system design and preferences. Check out the article on dual voice coil subwoofers for more information.

[edit] What about impedance when wiring subs?

Impedance is the amount of resistance speakers provide to the current flowing from the amplifier. Every time you halve the speakers' impedance — switching from a 4-ohm to a 2-ohm sub, for instance — you effectively ask the amplifier to double its output. Some amps can handle this lower impedance, some cannot. The key thing to know about impedance, then, is how to match your speakers to the capabilities of your amp.

The typical car stereo amplifier is stable down to 4 ohms in mono (or bridged) mode or 2 ohms stereo. Some high performance amplifiers can operate safely with loads as low as 1/2-ohm in stereo (1-ohm mono). If you're designing a subwoofer system, ask yourself the following questions:

1. How many subs do I want? More subs = more cone surface area = more air moved = big bass! Balance this equation against the amount of room in your vehicle.
2. How much power do I want? If you're powering your vehicle's speakers with your receiver, you'll need less power for your subs. If you use a multi-channel outboard amp for your speakers, you'll need more power for your subs.

Check out suitable amps in your price range. Once you've found the right amplifier, look for subwoofers that complement your amp in terms of power rating and impedance. Most subs are rated at 4 ohms, but 2-ohm, 8-ohm, and dual voice coil subwoofers have become commonplace, so it's easy to find speakers that will bring out the best in the amp you've chosen.

[edit] How many subwoofers can I hook up to my amplifier?

A well-made stereo amplifier that is stable to 2 ohms should be able to handle up to four 4-ohm woofers (two subwoofers wired in parallel to each channel).

If you want to bridge a 2-channel amp to one channel, it's best to only connect one 4-ohm woofer. The minimum impedance for the bridged (mono) output of a 2-channel amp is usually 4 ohms. Mono subwoofer amps, like the Kenwood KAC-819, are stable down to 2 ohms, allowing you to hook up two 4-ohm subs in parallel.

[edit] What's Poly-Fill?

You're probably already familiar with Dacron polyester fiber-fill, or Poly-Fill — chances are you've slept on a pillow stuffed with this material. But you may not realize how Poly-Fill can help your bass.

Stuffing your enclosure with the right amount of Poly-Fill can make your box behave like it's larger than it really is. This comes in handy if the volume of the box you've built turns out to be a hair shy of the cubic air space recommended for your subwoofer. Depending on how much Poly-Fill you use, you can actually vary perceived box volume by as much as 30%.

You can also "stuff it" if you simply don't have room in your vehicle for the larger box your sub demands. And adding Poly-Fill to any enclosure can clean up your bass by minimizing unwanted box resonances — and at a reasonable cost.

[edit] What crossover point should I choose?

When we set up systems at Crutchfield, we usually start with a low-pass crossover point around 80 Hz. Through trial and error, we've found that higher crossover points tend to emphasize the source of the bass instead of the overall musical experience. In other words, you can tell the bass is coming from a box in the trunk.

A crossover point between 60 and 80 Hz focuses the power of your subwoofer amplifier on your music's deepest notes (the ones you feel) and helps make the bass you hear seem like it's coming from the front of the vehicle along with the rest of the stereo image.

Your own preferences are also important. If you prefer a hard-hitting midbass boom, or if your front speakers or subwoofers are small, a crossover point of 100 or even 120 Hz is appropriate.

[edit] Glossary

[edit] Basket

The metal frame that holds all the components of a subwoofer together. The basket's rigidity and resistance to resonance help determine the sub's sound quality.

[edit] Box volume

This measurement, listed with each component subwoofer, tells you the recommended interior volume in cubic feet that an enclosure should have to get the best performance from the sub. A variation of 10-20 percent is generally acceptable.

[edit] Dual voice coil subwoofer

While typical speaker drivers have one voice coil, dual voice coil (DVC) subwoofers allow you the advantage of flexibility in wiring your system. Parallel wiring provides for maximum amplifier output, while series wiring lets you configure multiple woofers to one amplifier at an acceptable impedance. In series/parallel mode, you can wire 4 woofers to a single amp, for example, and still maintain a compatible impedance. Independent wiring lets you drive a single sub without bridging (or by bridging a four channel amp to one sub).

[edit] Enclosure types

Sealed box — A sealed box is an airtight enclosure housing your subwoofer. A sealed box is best for any music that demands tight, accurate bass. Expect flat response, deep bass extension, and excellent power handling. Since a sealed enclosure tends to require more power than a ported box, use an amplifier with ample wattage for optimum performance.

Ported box — A ported box uses a vent (called a port) which allows movement of air in and out of the enclosure chamber. This additional air movement reinforces low bass response. You get more output from a ported box than you would from a sealed box at any given level of amplifier output. Some people simply prefer the sound of ported boxes for rap, techno, or any hard-driving music because they play louder than comparable sealed boxes.

Bandpass box — A bandpass box is a special type of ported box designed for maximum slam. The woofer is mounted inside a dual-chambered box; the woofer fires from the sealed chamber into the ported chamber, and sound waves emerge from the ported side. Because the sound that comes out of the port is extra loud within a narrow frequency range, bandpass boxes are considered super efficient. Their aggressive sound is popular with many hip-hop, techno, and metal fans.

Free-air subwoofers — A free-air system consists of woofers mounted to a board attached to the rear deck or placed in the trunk against the rear seat. The trunk acts as the enclosure housing the subwoofer. Free-air systems save space and have flat frequency response. The woofer must be specifically designed for free-air use, and the trunk must be airtight for best results.

A good enclosure design book such as Vance Dickason's Loudspeaker Design Cookbook might be your most valuable speaker-building tool.

[edit] Frequency range

The range of sounds from lowest to highest that the subwoofer is capable of reproducing. The figures listed with the drivers are furnished by the manufacturers. The actual range you'll hear can vary depending upon the type of box, crossover point, and the vehicle the subwoofer is installed in. Under most circumstances, a typical sub will play slightly deeper than its published figures indicate. So, don't base your choice solely on this spec.

[edit] Impedance

The resistance offered by an electric circuit to the flow of alternating current — measured in ohms. A subwoofer rated at 2-ohm impedance will produce more output than a 4-ohm subwoofer, given similar input wattage, because the resistance is lower.

[edit] Peak power

The amount of power the subwoofer can handle as a brief burst during a musical peak. You should not drive your subwoofer continuously with wattage equal to the peak power rating.

[edit] Pole Piece

A solid piece of steel which protrudes up through the magnet into the voice coil assembly, concentrating the energy from the magnet.

[edit] Power range

An external power amp is required to drive any raw component subwoofer. (Don't try to drive one with your in-dash receiver's built-in amplifier.) The low number listed is the absolute bare minimum wattage required to get acceptable sound from the subwoofer. For best results, use an amplifier that provides a power level (RMS, or continuous watts) in the upper part of the subwoofer's recommended range (RMS).

[edit] Sensitivity

Also referred to as efficiency (measured as SPL — sound pressure level), this specification is quoted in decibels (dB). The higher the number, the more efficient the subwoofer is at turning amplifier power into sound, and the louder it plays. A subwoofer rated 3 dB more than another will require only half the power to produce the same output.

[edit] Spider

The spider (also known as the damper) controls the cone's movement and keeps the voice coil centered in the air gap. It acts like a shock absorber, smoothing out the cone's ride.

[edit] Surround

Part of the sub's suspension, the surround keeps the cone centered as it moves in and out of the basket. It's usually made of a durable material like treated foam or rubber in order to withstand the punishing job of producing big bass.

[edit] Thiele/Small Parameters

These are terms used to describe the characteristics of a particular subwoofer. They include resonance frequency of the driver, the woofer's excursion, and air displacement, among others. These figures are useful in predicting subwoofer performance and constructing appropriate enclosures.

[edit] Top mount depth

Tells you the depth of the woofer when it is installed from above the mounting surface. The depth will be greater for subwoofers that are mounted from below the mounting surface.

[edit] Voice Coil

The voice coil consists of a former (or bobbin) with wire wound around it. The voice coil is attached to the bottom of the cone and extends into the air gap surrounding the pole piece. The voice coil translates the magnet's energy into cone motion.

[edit] Subwoofer Enclosures

The type of bass you get from your component subwoofer doesn't depend on the woofer alone. You'll need a strong, tightly-constructed enclosure, such the Q-Logic boxes offered by Crutchfield, for optimum subwoofer performance. Speakers without an enclosure can't deliver full bass because the sound from the back of the speaker can cancel out some low frequencies emanating from the front of the speaker.

Using box-building accessories, you might choose to construct your own box to create the enclosure size that you want. However, unless you have excellent craftsman skills and a solid understanding of enclosure volumes and other technical terms, you're better off purchasing a convenient, professional-looking pre-made enclosure.

Different types of boxes will produce different types of bass:

Sealed boxes: For deep, precise bass

A sealed box is an airtight enclosure housing your subwoofer. A sealed box is best for any music that demands tight, accurate bass. Expect flat response (not excessively boomy), deep bass extension, and excellent power handling. Since a sealed enclosure tends to require more power than a ported box, use an amplifier with ample wattage for optimum performance.

Ported boxes: For forceful bass

Ported boxes use a vent (called a port) to reinforce low bass response. You get more output than you would from a sealed box at any given amplifier wattage. Some people prefer the sound of ported boxes for rock, heavy metal, or any hard-driving music. Ported boxes can deliver deeper bass than sealed boxes, though they need to be much larger than sealed enclosures to accomplish that.

The Q-Logic ported boxes we offer come with pre-cut port holes (sealed with a plastic port plug) and trimmable ports.

Bandpass boxes: Maximum slam!

Bandpass boxes are a special type of ported box designed for maximum slam. The woofer is mounted inside a dual-chambered box (one chamber sealed, the other ported), with the sound waves emerging from the ported side. The sound that comes out of the port is extra loud within a narrow frequency range.

Because bandpass boxes are super efficient within that range, they tend to boom. Their aggressive sound is great for rap, reggae, and hard rock. : : Not all subwoofers work well in bandpass boxes, though; consult our product information or call a Product Advisor to be sure.

Choosing an enclosure for your subwoofer

Q-Logic's convenient enclosure ratings are being adopted by more and more manufacturers. Here's how it works — pick a subwoofer from Crutchfield's wide selection, and you'll notice a recommendation for "Box Type" listed in the sub's Key Features (based on the manufacturer's air space recommendations). We check every sub for fit, so if you want to see boxes that work with the sub you selected, click on "Recommended Accessories." If you don't see a particular box listed for your sub (or if no box is listed), call a Product Advisor at 1-888-955-6000 to check out your options.

Q-Logic Box Types

• Type 1: Small, sealed box — produces tight, focused bass. The most accurate bass response of all box types, but requires more power.
• Type 2: Medium box — comes equipped with pre-cut port hole(s), port hole plug(s), and ports, so it can be used for either sealed or ported applications. More efficient than a sealed box, so you get more bass SPL with a little less accuracy.
• Type 3: Large Box — comes equipped with pre-cut port hole(s), port hole plug(s), and ports, so it can be used for either sealed or ported applications. Much more efficient than a sealed box, so you get more boom for your buck, but with less accuracy.
• Type 4: Bandpass Box — sealed/ported hybrid. Highly efficient, but with less accuracy.

Free-air subwoofers

A free-air system consists of woofers mounted to a board attached to the rear deck or placed in the trunk against the rear seat. The trunk of the car acts as an enclosure which houses the subwoofer and isolates sound from the back of the speaker, solving the sound cancellation problem of subs without an enclosure.

Free-air systems save space and have flat frequency response. The woofer must be specifically designed for free-air use. The lack of a box makes them more convenient to install, but their power handling levels are usually much lower than their boxed counterparts.

[edit] Dual Voice Coil Subwoofers

Dual voice coil subwoofers are becoming a popular choice among car audio enthusiasts who want more flexibility in wiring their sound systems. While typical subwoofers have a single voice coil, dual voice coil (DVC) subwoofers use two separate voice coils, each with its own connections, mounted on one cylinder, connected to a common cone.

The key difference between single and dual voice coil subwoofers is the multiple wiring options DVC subs offer:

• Parallel: A dual 4-ohm voice coil subwoofer with its coils wired in parallel presents a 2-ohm load to your amplifier. Since an amplifier produces more wattage at a lower impedance, the parallel connection ensures you'll get the most output from your amp. In the same fashion, if you have a stereo amplifier and two DVC subs, wire both subs for 2-ohm impedance (one per channel) for maximum output.

• Series: Series wiring lets you configure multiple woofers to one amplifier at an acceptable impedance. Wire both coils in series for an 8-ohm impedance, and then wire two 8-ohm subs together in parallel for 4-ohm total impedance (perfect for most 2-channel amps bridged to mono operation). Another example: if you have a high-powered 2-channel amplifier, wire four 8-ohm subs per channel (each channel sees a 2-ohm load).

• Independent: You can wire each voice coil to a separate channel of your amplifier, if you prefer not to bridge your amp. Independent wiring is a nice option if you're wiring two DVC subs to a 4-channel amplifier — one voice coil per channel.

DVCs and high-performance amplifiers

Some amplifiers are designed with an unregulated power supply — these amps are favored by mobile audio competitors for their superior performance. An unregulated amp's power increases dramatically when it sees a lower impedance load. For example, an amplifier that produces 75 watts RMS x 2 channels at 4 ohms would double its power to 150 watts x 2 with a 2-ohm load. DVC subwoofers (particularly the dual 2-ohm models) give you the flexibility to wring every bit of power out of this type of amplifier.

Also, if you choose to add an unregulated amp as a power upgrade to your existing DVC subwoofer system, you can simply rewire your subs for optimum impedance. Remember that most car amps are stable down to 2 ohms in normal operation, and to 4 ohms in bridged mode. It's important to check your amp's manual for its operating parameters before hooking up a DVC sub wired for low impedance!

A DVC sub offers the same performance whether it's wired in series or parallel. Its power : handling levels, frequency response, and other specifications do not change — the only difference is the impedance presented to the amplifier. As a result, you'll use the enclosure that's recommended for your sub, no matter how it's wired.