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Car audio pdf

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Car audio systems can seem hopelessly complex when you're starting out. Don't know the difference between and subwoofer and a head unit?. Hints and advices for car sound builders using thoose who want to do a first class car sound instal- The built-in amplifers in most CD:s and stereo casette. your music will sound better at higher volumes, more dynamically and without distortion. Installing JBL car audio products isn't as difficult as you might think it is.


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THE CAR STEREO COOKBOOK This page intentionally left blank. Car Stereo Cookbook How to Design, Choose, and Install. passion for cars spawned Focal's Car Audio collections in the s. These car audio systems and kits are designed to enable car enthusiasts. Doug Newcomb has been writing about car audio since He was editor such publications as Car Audio and Electronics, Sound & Vision, E-Gear, and.

Use the built-in crossover together with a separate crossover. The sub amp power should equal 1. A piece of bent coat hanger will do the job of removing the spring clips just bend a tiny hook in the end and use it to pull off the clip , or you can carefully push it off with a flat-blade screwdriver. Existing locations may be inadequate for reasons of imaging, inability to accommodate drivers of the desired size, or enclosure volume. This may result in damaged equipment or equipment that simply fails to operate. Heat-shrink tubing is slid onto a wire before soldering, then it is slid over the soldered connection and heated with a butane lighter or heat gun until it shrinks to conform to the connection. In a ported system, the sound from the back of the speaker produces a resonant output at the port, much like producing a tone by blowing air across the mouth of a soda bottle.

Adding surface-mount tweeters Low-cost way to improve high-frequency response of moderate-quality speakers.

Pdf car audio

Upgrading existing speakers Simple and unobtrusive way to extend highfrequency and bass response plus increase power handling. Installing speakers in new location Useful when existing speaker locations are inadequate.

Installing separates Provides highest sound quality, but expensive and labor intensive. Adding a subwoofer Best way to achieve thunderous bass—removes burden of bass from the other speakers, allowing them to play louder and with less distortion. A typical listening arrangement for a car is shown in Fig.

This setup has the potential to wreak havoc with imaging. For example, the sax player who was supposed to be standing directly in front of you might now seem to surround you. Or, if the back speakers are louder than the front, the sax player may seem to be directly behind you. This leads to the key question: How much do you care about imaging? For most people, imaging in the car is not a big concern. But for some, it is. Achieving good imaging is not without its sacrifices, either.

It puts a big performance burden on the front speakers as primary drivers, since the rear speakers are used only for fill. In either case, the difficulty of getting good bass out of the front usually makes a subwoofer necessary when good imaging is the goal. For the ultimate imaging performance in car audio, 5.

Surround sound is already popular for home-theater systems, and is starting to appear in factory and aftermarket car audio. A hurdle with upgrading to 5. To achieve the proper surround-sound effect, all five primary channels right and left front, right and left rear, and center channel need to be voice-matched.

It means that the center channel speaker should ideally be at the same height and use the same driver as the other two front speakers. Upgrading to 5. See Chapter 6 for more info. For those who want to perform an imaging overhaul in a four-channel system, here is my three-point program: The goal here is to provide good power handling and frequency response down to Hz, where a subwoofer can take over.

A crossover can be used to block energy below Hz to the primary drivers. This allows them to play louder with less distortion. You may also decide to upgrade your existing front speakers with drop-in replacements or even go with separates. Operating rear speakers at a reduced volume level with respect to the front speakers actually expands the stereo image. A subwoofer takes over the job of providing deep bass where the front speakers normally give out. Removing the burden of bass from the front speakers allows them to play louder and with less distortion.

Chapter 4 has details. Adding Surface-Mount Tweeters Inexpensive speakers usually do a good job of reproducing mid-range, but they generally lack good high- and low-frequency capabilities.

Adding surface-mount tweeters Fig. Courtesy of JL Audio. Cones are an obsolete technology for tweeters. Piezo tweeters are highly efficient and do not require a crossover capacitor, but their advantages end there. Because of their inherently resonant behavior, they almost always exhibit a poor frequency response. Ferrofluid allows better cooling of the voice coil and thus provides greater power handling. It also smooths the frequency response somewhat.

A ferrofluid-cooled model is recommended for high-power applications. Another factor to consider is the mounting base. Some models allow the mounting angle to be adjusted by rotating the base.

This can be quite helpful when trying to mount the tweeters so they aim toward the ears of the listener. Placing Tweeters If you use rear speakers only for fill, you can add surface-mount tweeters in the front only. If you listen to front and rear speakers at nearly equal volume levels, you should add tweeters in the rear too.

For optimum performance, tweeter modules should be mounted using the following guidelines: Some of these rules conflict in a normal installation, and the practical and aesthetic aspects of mounting must be considered as well, so you must weigh the relative importance of many factors. Violating this rule will degrade imaging. Restrict tweeter placement to a 6-inch range in all directions, then consider how to best satisfy the other guidelines.

Possible locations include door Fig. Windshields can be thought of as sound mirrors for tweeters. The apparent image of the tweeter is just as real and powerful as the tweeter itself. If you can see both the lightbulb and its reflection at the same time, you are in trouble—imaging will be smeared. The further apart the apparent image and the actual source, the worse the smearing.

If you must mount a tweeter on the top of the dashboard, either mount it very close to the windshield or aim it so that either the direct path or reflected path will strongly dominate over the other. Courtesy of Crutchfield. The crossover capacitor allows only the high-frequency components of the signal to reach the tweeter. This prevents low frequencies from causing distortion in the tweeter or burning it out. The crossover frequency defines the dividing line between the high frequencies, which are passed to the tweeter, and the low frequencies, which are filtered out.

The capacitor should be the non-polarized type also called bipolar. Table shows some common values of crossover frequencies and the corresponding crossover capacitor values for 4-ohm tweeters. If you want to calculate your own capacitor values, use this equation: Changing the crossover frequency strongly affects how much power the tweeter must handle.

For example, lowering the crossover frequency from 8 to 6 kHz subjects the tweeter to roughly 40 percent more power. Similarly, increasing the crossover frequency from 8 to 12 kHz subjects the tweeter to roughly 40 percent less power. Normally tweeter modules are provided with crossover capacitors, but you may wish to use a different value depending on the high-frequency performance of your existing speakers.

Experiment to find the value that sounds best, opting for the smallest capacitor value highest crossover frequency you find acceptable. After installing tweeter modules, you may find that they seem too loud compared to the existing speakers.

This is because tweeters are normally more efficient than full-range speakers. There are three ways you can deal with this: Pads are special attenuation circuits designed to maintain the impedance looking into them. The circuit for padding tweeters is shown in Fig.

Table shows the resistors to use for 3- and 6-dB pads for a 4-ohm tweeter. Be sure to use power resistors, or you will burn them out. The power ratings shown are adequate for a high-power head unit—power ratings will need to be increased when higher-power amplifiers are used.

Mount the crossover and pad components on a small board secured to the car. This will prevent short circuits to ground that could blow your head unit.

Upgrading Existing Speakers Upgrading your existing speakers is a simple and unobtrusive way to extend high-frequency and bass response. It also lets you increase power handling.

Choosing Speakers The first step in upgrading is to understand what you have space for. For odd-size factory holes, mounting adapter plates that permit standard aftermarket speakers to fit are available. Crutchfield has done a tremendous job in this department.

Their catalog shows what size speakers including depth fit in each factory location in your vehicle. They also provide installation guides that tell you how to access and remove your existing speakers. Their product lineup includes a wide selection of speakers. When choosing speakers, opt for a two-way model using a dome tweeter Fig.

If a speaker is to be mounted off-axis from your ears, choose a model with a pivoting tweeter so you can aim it toward you for better sound. Even supposedly reputable manufacturers often make exorbitant claims about power handling and frequency response.

Courtesy of Infinity. A typical 1-inch voice coil can be expected to handle about 35 watts, and a 2-inch voice coil about watts. Sensitivity is a term for how loud a speaker will play with 1 watt of power. This is important if you are using a normal or high-powered head unit, but not so important if you are using separate power amps capable of higher output power. Polypropylene cones are extremely resistant to environmental deterioration and are unaffected by humidity.

But poly cones are a temperaturesensitive plastic, and become soft in the heat, and hard when cold, affecting their sound. Paper-based cones absorb moisture, so humidity affects their sound. Coatings can be used to improve the resistance to humidity and sunlight, and reinforcement additives such as Kevlar, glass, mica, or ceramic can be used to improve the sonic performance of paper-based cones. Materials such as Tri-Laminate, resin laminate, carbon-blended poly, kapok, poly-graphite, graphite-quartz, Foam-Infused IMPP, titanium composite, ceramic metal matrix, Duralam, and mica-injected polypropylene offer the promise of superior performance.

Most of these are variants of polypropylene and paper-based cones, and may provide a performance advantage. What they mainly provide is a marketing advantage. The surround is the soft ring around the outside of the cone with the bulge in it. Strive for the most bass possible in front. It will prevent the undesirable effect of all the bass coming from behind you. The keys to good bass in the front or anywhere, for that matter are a good driver and a good enclosure.

Creating good bass means moving lots of air, so cone area is important too. Choose the largest driver that will fit in a hole.

You can buy adapters that let you mount a larger driver in a hole Fig. Depth extender rings that let you install deep speakers in shallow compartments such as kick panels or doors are also available Fig. Making the Best of the Existing Enclosure The enclosure will strongly affect your sound quality, especially the bass and mid-range.

To a large extent, you are stuck with whatever the car has to offer. Ideally, the enclosure is large, sealed, and nonresonant. In the case of replacing door speakers, doors are usually large and somewhat sealed, but they are typically resonant.

You can reduce the resonance problem by using foam baffles Fig.

Foam baffles have the added benefit of reducing road noise which can pass right through the speaker cone as well as protecting the back of your speaker against water and dirt that may sometimes find their way inside your door. Applying Dynamat or other sound-deadening material is another effective way to improve the sound of door speakers by reducing unwanted door panel vibrations and road noise.

In the case of replacing dash-mounted speakers, the enclosure is an open-backed cabinet. Open-backed cabinets allow the sound from the back of the speaker to be heard—in this case, from under the dashboard. This causes frequency response ripples peaks and valleys in the midrange and cancellation of deep bass. The closer the speaker is to the bottom of the dashboard, the worse the problem is. Some improvement can be made in the case of frequency response ripples by installing a cardboard box stuffed with damping material such as fiberglass or polyester batting behind the driver see Fig.

You may be able to use the flaps of the box as a mounting flange; otherwise you must devise your own method of securing the box. In cases where dash speakers are mounted near the bottom of the dash, it may be best to consider an alternate location. Installing Speakers in a New Location Installing speakers in a new location is necessary when existing speaker locations are inadequate.

Existing locations may be inadequate for reasons of imaging, inability to accommodate drivers of the desired size, or enclosure volume.

This is often the case for front factory speaker openings. This refers to the number of speakers covering a particular frequency range. Even with good-quality drivers, you should not try to create a wall of sound. Not only will it degrade your imaging, it will create a frequency response with lots of peaks and valleys. This is because the two drivers have a slightly different time delay to reach your ear, and this produces an interference pattern that cancels some frequencies and reinforces others.

If you need increased power handling, choose a speaker that can provide it rather than using multiple drivers. Choosing a Location There are two main factors for deciding where to put speakers for the best sound: Imaging depends on where the speakers are with respect to your ears. Imaging also involves things like reflections off the windshield or obstructions, such as passengers. Table shows common mounting locations for front speakers and their imaging and enclosure traits.

The front edge of the front doors is a popular location for front speakers because of the ease of installation. It provides a good enclosure but is a non-ideal imaging location because of the typically large path length difference.

Placing the speakers toward the center or rear of the front doors makes imaging even worse. It causes each listener to hear mainly one speaker and shifts the image too far back. In some cases, it may cause a passenger to block a speaker entirely. If you choose door-mounting speakers, use foam baffles behind the speakers to reduce resonance problems and road noise as well as protect the back of your speakers against water and dirt. Kick panels the side panels, under the dash are one of the best locations for imaging because the path length difference is usually small.

Speakers here should be aimed toward the listener for good results. The small enclosure volume usually strongly limits the bass response. This means you will either need to use back speakers to provide deep bass or add a subwoofer. The dashboard can provide reasonable imaging from a path length difference standpoint, but the top dashboard location suffers from windshield reflections that degrade imaging and frequency response smoothness.

This allows the sound from the back of the speaker to be heard through the bottom of the dashboard. The combined sound from the front of the speaker and under the dash results in a frequency response with ripples in the mid-range and deep bass cancellation. The cardboard box with damping material, explained previously, helps with mid-range smoothness.

Because of the limited bass response, you will either need to use back speakers to provide deep bass or add a subwoofer. Open-back enclosure produces mid-range frequency response ripples and makes bass below Hz difficult Dashboard—front or bottom Open-back enclosure produces strong midrange frequency response ripples and makes bass below Hz difficult The best location for rear speakers should be determined by enclosure rather than imaging concerns.

This is because in most installations the rear speakers provide the deep bass for the entire system. You should choose whatever location provides the biggest and best sealed box. If you have a trunk, use it! Center Channel Speakers For 5. This is in addition to the right and left front, right and left rear, and subwoofer speakers. Ideally, the center channel speaker should be at the same height and should have the same frequency response as the front speakers.

Trying to install a speaker in a dashboard without a factory hole is a difficult project, especially if you want it to look and sound good. In addition to the challenge of mounting a center channel speaker, most amplifiers lack the fifth channel needed to drive it. Fortunately, there are some clever products to help you solve this problem. Courtesy of Clarion. It comes with a 25 watt amplifier. The amp has an internal Hz crossover to prevent overdriving the speaker with deep bass.

Alpine offers another option Fig. The SBS is a dash-mount center channel speaker. It uses a 2. Installing a Door Speaker The first step in installing a new speaker in a door is removing the door panel.

Start by removing the window crank handle Fig. Some handles are held on with a screw, which is sometimes hidden by a snap-on cap. Most are held in place by a spring clip. To remove the clip, you can use a window crank clip removing tool or a piece of coat hanger with a tiny hook bent into the end. Depress the surrounding panel, look behind the window crank handle, and rotate the handle until you see the spring clip.

Then gently push it off with the window crank clip removing tool or pull it off with the hook. Courtesy of Alpine Electronics, Inc. NOTE To reinstall the handle later, first snap the spring clip onto the handle, then push the handle back onto its shaft until it locks into place.

After removing the window crank handle, remove the armrest usually secured with a few Phillips-head screws and any trim around the door handle.

The only thing holding the door panel on now should be a half dozen friction fittings and possibly a few more screws. With all the screws removed, start at a bottom corner and pull the panel straight out. Use a large flathead screwdriver to help pry it off. If a friction fitting breaks, you can get replacements from an auto parts store. Once the corner is loose, work across the bottom and up both sides, being careful not to use too much force. With the bottom and sides loose, the panel should now be hanging by some trim that sticks down into the window well.

Lift straight up and it should come free. Make sure no internal mechanisms will be affected. Be especially careful to check that the speaker will not interfere with the window and window crank mechanisms. Check the clearance with the window rolled down. Also try closing the door—the mechanism that holds the door open can sometimes intrude into the speaker mounting cavity as the door closes. The risk of clearance problems is smaller when enlarging a factory location for a speaker than when creating a new opening.

Very few doors are solid sheets of metal—there are usually several holes. Double-check the depth available in the door for mounting your speaker. If you think the measurement is too close, you may be able to use a spacer ring. Metal Cutting Tips Here are some techniques that will help you make cleaner cuts and avoid damaging your car: Then cut the corresponding sheet metal with a jigsaw equipped with a metal cutting blade.

If you try to cut both layers at once, you may rip the panel covering.

Audio pdf car

If it does, it will peck numerous dents very quickly! Similarly, make sure the window is rolled up and there are no other obstructions the saw blade can reach. When using a jigsaw or any other power tool, always wear safety glasses or goggles Fig. Tape the supplied template on the exact spot and trace the inside edge with a pen.

Lay the panel flat on a clean surface and cut out the circle with a sharp X-Acto or utility knife. Be patient. A dull blade or too much haste here might rip the fabric.

Repeat the procedure for the other door, making sure to cut in the same place. You can hold the cut door panel against the uncut one and trace the hole with a pen to guarantee they will be the same.

Frequently the speaker location will partially overlap an existing hole, which can be easily enlarged. If the amount of cutting involved is small, a utility hacksaw can be used. If there is no hole to start with, use a drill to make a pilot hole for the jigsaw blade. After the hole is cut, but before the speaker is installed, vacuum out all the metal particles and other debris. Particles can get into a speaker and cause buzzing. Using a utility knife or scissors, cut the sheet to the desired shape and size.

You may find a cardboard or paper template helpful. Remove the backing from the sheet and apply the material to the prepared surface. On large surfaces, remove the backing in sections, working your way down and across the panel. Using a roller tool Fig. Courtesy of Dynamic Control. Use a utility knife to poke holes into any air pockets that may have formed, then roll them out. It will have to exit the body of the car in the doorjamb and enter the door as close to that spot as possible.

Often there are precut holes with plugs in them that will work out nicely. To run your wires from the door into the car body, try to use the factory rubber tubing between the door and the door jamb. If the tube is not present on your car, it may be available from a junkyard. Before you drill a hole in the door, make sure it will provide access to the speaker location.

Sometimes structural steel isolates the front edge of the door. It may still be possible to route this way, but check first. Protect the wiring from the sharp edges of the holes by using rubber grommets in the holes or flexible tubing run between the two holes. This will keep the insulation from being cut after countless openings and closings of the door. Remember to leave enough slack in the wire to accommodate the door opening all the way.

If you accidentally broke a strategically located like a corner friction fitting when removing the panel, replace it with either a new one, or in a pinch, one taken from the middle of the panel along the bottom. If your new speaker is designed to be top mounted, you can replace the door panel now. A foam baffle should be installed between the door and the door panel.

When the door panel is properly positioned, push the friction fittings back into their seats and replace enough of the screws, armrest, etc. Do not reattach the window crank yet, since you may have to remove the panel again. Hold the speaker in its new home, mark the screw holes, and remove the speaker.

Drill the holes. Connect the speaker wires to the speaker, observing the proper polarity. If you attach a set of wires to the terminals of one speaker backward, that speaker will be out of phase and your bass performance will suffer as a result. Connect the minus wire to one speaker terminal and touch the plus wire to the other speaker terminal. Watch the speaker cone when you connect the battery. If it moves out, then the plus terminal of the battery is connected to the plus terminal of the speaker.

Otherwise, the plus terminal of the battery is connected to the minus terminal of the speaker. Mark the plus terminal accordingly. When supplied, use speed clips Fig. They give the screws something extra to hold on to, providing extra support when the door is slammed. Once the speaker is installed, put the grille on immediately to prevent damage to the speaker while you do other work.

Installing Separates Separates also called component speakers are individually installed woofers and tweeters Fig. This is instead of having the tweeter mounted in front of the woofer, as is the case with coaxial speakers.

Pdf car audio

Normally, separates are sold as matched sets, including woofer, tweeter, and crossover. The advantages of separates are the quality of the components—especially the crossover—and the flexibility of mounting.

The disadvantages are the high cost and the additional installation work. The quality of component woofers and tweeters is usually superior to that of coaxial speakers, for marketing rather than technical reasons. The crossover splits the music signal into low frequencies bass , which go to the woofer, and high frequencies treble , which go to the tweeter. In a typical coaxial speaker, a simple capacitor is used to prevent bass from going to the tweeter and nothing is used to prevent high frequencies from going to the woofer.

This approach is inexpensive and small enough to fit conveniently on the basket assembly of the speaker. Unfortunately its performance is marginal. The crossover module provided with component systems does not have the same size limitation, and because of the marketing niche, some money can be spent on a real crossover. The difference can be quite audible, particularly in mid-range smoothness and lower distortion. Having a separate tweeter provides flexibility of mounting in the sense that you can now mount the woofer in a spot that would be unacceptable for tweeter orientation in a coaxial speaker.

For example, you could mount a woofer on the bottom front corner of the kick panel, facing the opposite woofer, and a tweeter on the top rear corner of the kick panel, facing the listeners. Courtesy of Q-Logic. Restrict tweeter placement to a 6-inch range in all directions, then consider how to best satisfy the other mounting guidelines. Separates are most advantageous in front, where mid-range performance is most critical and mounting flexibility is more likely to provide a benefit.

You may choose to use separates in front and coaxial speakers in the rear to save money without sacrificing top-notch performance. If you plan to use separates in the front, consider the kick panel pods by Q-Forms Fig. The pods aim the speakers toward the listener for good imaging, increase the size of the enclosure to improve bass response, and maintain a factory appearance. There are two good reasons for this. Second, there are a tremendous number of options you must choose from every step of the way.

A subwoofer not only gives you a rock-solid bottom end, it lets you play your other speakers louder with less distortion by diverting the burden of deep bass to the subwoofer. A subwoofer is almost a necessity if you use the front speakers for imaging and the rear speakers for fill, because of the difficulty in getting decent bass from the front.

Because subs are so important, manufacturers offer a staggering array of products to support a vast number of approaches. You must choose between everything from powered subs with built-in crossovers to separates, and every combination in between. You can design and build your own box, choose a pre-made one and install your own driver, or buy a ready-made system. There are sealed, ported, bandpass, and other types of enclosures to choose from.

This chapter will cut through the hype and give you the know-how to choose and use the right components, whether you want to buy or build.

System Configuration Options There are six basic configurations for adding a subwoofer system Table The first two use speaker-level crossovers, the rest use preamp-level crossovers. Speaker-level crossovers are used between the amplifiers and speakers and are passive requiring no power.

Preamp-level crossovers are used before the amplifiers and are generally active requiring power. The preamp-level crossover configurations vary only in how they repackage the three basic building blocks of a subwoofer system: Separates provide the greatest flexibility; amplified subs with built-in crossovers provide the most convenience.

Other options fall in between. The secret to good subwoofer performance is in the crossover. Regardless of which approach you choose, make sure you satisfy the requirements for a good crossover. Subwoofer level and crossover frequency are not adjustable. Not recommended. Tri-way crossover, sub Lets you use a single tri-waycapable amp to drive a subwoofer and boost a pair of speakers.

Amp has no built-in crossover or one considered inadequate. Amp with built-in crossover, sub Can save the cost of a separate subwoofer crossover. Built-in crossover may be inadequate. Separate crossover, amplified sub Offers potential cost savings and convenience by combining a subwoofer with a matching amp. Amplified subwoofer has no built-in crossover or one considered inadequate. Amplified sub with built-in crossover The ultimate in convenience. This approach lets you use a single amp rather than two to both drive a subwoofer and boost a pair of speakers.

This would seem to provide a substantial cost savings, but for the same amount of total power, this is not usually the case. In addition, there are a number of performance limitations involved with using a speaker-level crossover. Because a single amp is shared by all drivers, the tweeters are unprotected against clipping of deep bass to the subwoofer explained in detail in Chap.

Unlike most preamp-level crossovers, speaker-level crossovers have fixed crossover frequencies and cannot be adjusted to optimize your system. Furthermore, the subwoofer level is not adjustable with respect to the main speakers with a speakerlevel crossover. This degrades imaging. For these reasons, conventional speaker-level crossovers are not recommended for subwoofers. Tri-Way Crossover, Subwoofer A tri-way or tri-mode crossover connects between a tri-way-capable amp and your speakers.

In addition, there are a number of performance limitations involved with using a tri-way crossover. Unlike most preamp-level crossovers, tri-way crossovers have fixed crossover frequencies and cannot be adjusted to optimize your system.

The subwoofer level is not adjustable with respect to the main speakers in a tri-way setup. For these reasons, tri-way crossovers are not recommended.

Separates Using a separate crossover, amp, and subwoofer offers you the most flexibility and the best performance of any of the configurations. You can choose whatever power level you need in an amplifier and pick a subwoofer that is a perfect fit for your vehicle.

Most importantly, you can select a subwoofer crossover that provides a steep slope as well as important features usually found only in separate crossovers. The amplifier in this configuration either has no built-in crossover or has one that is considered inadequate. You may be able to take advantage of an inadequate built-in crossover to reduce the requirements for a separate crossover. See the box to learn how. Use the built-in crossover together with a separate crossover.

An inadequate built-in subwoofer crossover can be defeated by choosing the bypass setting. Since the separate crossover will now be doing all the work, you will need to choose a model that meets all your needs.

The advantage of this approach is that you then have a single set of controls to deal with, and what you see with them is what you get. Alternately, you can use the built-in crossover to effectively increase the performance of the separate crossover. This reduces the requirements for the separate crossover and can save money. Table shows an example of how this works. The possible crossover setting combinations and their combined responses are shown in Table First, you now have more cutoff frequencies available than either individual crossover provides.

This gives you finer control unless one of the crossovers was already continuously variable. Second, the crossover frequencies shift to lower values when you combine two crossovers—about 20 percent below the nominally selected frequencies in this case. This makes sense if you think about it: The 3-dB down frequency of the combined response must be a lower frequency.

This could be good news or bad news depending on the frequency you want and the available frequencies.

Beginner's Guide to Car Audio Systems

For best results with this approach, try to set both cutoff frequencies the same. This will give you the sharpest filter characteristic near the cutoff frequency.

Features such as subsonic filters, polarity switches, and Hz bass boost might be included in one crossover, but not the other. This can be a great way to save the cost of a separate subwoofer crossover, but you need to make sure the built-in crossover meets your needs. Similarly, many built-in crossovers offer only a single fixed cutoff frequency. This limits your ability to seamlessly integrate a subwoofer into your system.

Few models offer subsonic filtering. Amplifiers with capable built-in crossovers do exist. It has a 15 Hz subsonic filter, adjustable bass boost, and both speaker and preamp-level inputs. Separate Crossover, Amplified Subwoofer This approach uses a separate crossover in conjunction with an amplified subwoofer.

Either way, this approach offers potential cost savings and convenience by combining a subwoofer with a matching amp. Using a separate crossover guarantees you can obtain the performance and features you need in a crossover without severely limiting your choice of amplified subs.

Amplified subs without built-in subwoofer crossovers are becoming rare as manufacturers realize that they can include a bare-bones crossover for a small incremental cost.

Unfortunately, most of these crossovers are inadequate for the job and need the help of an external crossover. See the box on p.

The separate crossover used with this approach may be a subwooferonly crossover or one with high-pass filtered outputs for the main channels too. If you are using separate amps to drive the main channels, then the latter is the way to go. Many amplified subs are designed to fit in the trunk or cargo area of almost any vehicle.

Courtesy of MTX. Courtesy of Kenwood. This is a compact powered sub that puts out surprising bass for its size. The main concern with all amplified subwoofers is making sure the built-in crossover meets your needs. The line output converter is needed to convert the signals from the premium factory head unit to a standard preamp-level signal suitable for crossover inputs.

The LOCB.

It also has a noise-blanking circuit that activates the audio path after turn-on noises have subsided. With this system, the head unit provides fixed-level audio signals to the factory amplifiers. The head unit issues commands to each amp via the Class 2 data bus to control volume, fader, and balance. This approach provides improved noise immunity, but makes adding a subwoofer more challenging.

Additionally, the GMAA reads the data bus and generates an amplifier remote turn-on signal so the aftermarket amp turns on and off with the head unit, not with the ignition. No line output converter is needed with crossovers having speakerlevel inputs. What to Look For in a Subwoofer Crossover There are a number of considerations for choosing the right crossover for your application. You might choose a dedicated subwoofer crossover with subwoofer outputs only, or one with high-pass outputs too if you use amps to drive your main speakers.

The most important subwoofer crossover characteristics are listed in Table The crossover filter slope may be the single most important item to consider. Cutoff frequency range to Hz minimum range.

Continuously variable—a big plus. High-pass outputs Important if you have amps driving main speakers. Subsonic filter Crucial for ported boxes, beneficial for others. Polarity switch Useful for improving bass. Speaker-level inputs Important if your head unit lacks preamp-level outputs. Preamp-level inputs Ground loop isolation is a big plus for reducing noise problems. Output level controls Of limited value—usually redundant with amp input level controls.

Automatic amp wake-up output Saves having to run remote turn-on wire from head unit to sub amp. Since only deep bass frequencies are nondirectional, this gives away the subwoofer location and degrades imaging. Who wants a bass guitar player under the seat?

A subwoofer cutoff frequency range of 75 to Hz in three or four steps is adequate for most situations. A continuously variable cutoff frequency control gives you full flexibility to seamlessly blend the subwoofer with the rest of your system. Even with high-pass crossovers on your main speakers, the natural low-frequency rolloff of woofers makes it difficult to predict the best subwoofer crossover frequency. A continuously variable crossover lets you avoid a gap or peak in your mid-bass.

High-pass outputs are an important feature if you have amps driving your main speakers. Using this feature saves you from having to install bass blocking crossovers in line with your main speakers. The high-pass slope for the main speakers does not need to be the same as the subwoofer low-pass slope.

A subsonic filter prevents very low frequencies from getting to the subwoofer amp and speaker. A subsonic filter protects against unnecessary distortion and speaker damage as well as reducing annoying turn-on thumps.

Five to 10 dB of bass boost at 40 or 45 Hz extends the low-frequency response of most subwoofer systems without overdriving them. A subwoofer polarity switch lets you select the proper polarity without having to reverse any speaker wires. Choose the setting that gives you the most bass. If your head unit lacks preamp-level outputs, then speaker-level inputs are an important feature.

Preamp-level inputs are provided as standard equipment on almost every crossover. If you plan to use them, buy a model with ground loop isolation. This will go a long way toward preventing system noise problems.

Output level controls are usually provided for each set of outputs, but they are of limited value. They are usually redundant with the input level controls found on your amp. There are many names for automatic amp wake-up output, a useful feature that eliminates having to run a remote turn-on wire from your head unit to your sub amp.

It works by monitoring the DC voltage on a speaker wire from the head unit, and provides a signal to activate the subwoofer amp when the head unit is on. One final point. The important thing is to obtain the performance you need in your combined system.

Many of the features listed above may be included in your power amp. If neither do, you can add one externally if you want to. Choosing a Subwoofer Amplifier Most of what you should know about choosing amps is contained in Chap. There are two additional points worth covering here: The appropriate power for a subwoofer amp mainly depends on how much power is used for the rest of the system and the subwoofer crossover frequency used. The typical frequency distribution of power in music is shown in Table Notice that less than half the power in music is above Hz.

This means that at least half the power in music is below Hz. Rule of Thumb: The sub amp power should equal 1. The rule of thumb says you should use a sub amp that can provide roughly 1. Consider using more power for your subwoofer amp if: An amp used in a maximum power configuration runs hotter, so be sure to mount it where it will have good air circulation.

You should choose the right amplifier configuration to provide efficient power transfer to your speakers based on the number of subwoofers you plan to use and their impedances. Only by doing this are you getting the amplifier power you paid for.

Subwoofers are commonly available in 4-ohms, dual 4-ohms, and dual 2-ohms. Amplifiers usually support bridging and are 2 ohm stable, but there are exceptions. Because of the many possible combinations, the best configurations are shown for convenience in Table Table shows maximum power and rated power configurations for both one- and two-subwoofer systems.

Rated power configurations provide acceptably efficient power transfer to your speakers with little risk of overheated amplifiers. Rated power configurations are so named because they give you the rated power nominally specified using a 4-ohm load.

Maximum power configurations provide the maximum power transfer to your speakers that is still safe for your amp. Maximum power configurations typically provide 50 percent more power transfer than rated power configurations for a given amp. Configurations other than those shown may not provide satisfactory power to the speakers or may risk blowing the amp.

For example, using rated power configurations with higher-impedance speakers than those shown is throwing away amplifier horsepower. Using maximum power configurations with lower-impedance speakers than those shown will most likely overheat your amp. Configurations with the same letter such as b1 and b2 use the same hardware, but are configured differently.

For example, b1 and b2 both use a two-channel amp with a 2-ohm dual voice coil sub. Both provide the same performance, but you may prefer one method of wiring to another or may not have a bridgeable amp.

Of course, you must use an amp that is bridgeable to do this. As an example, a watt per channel stereo amp might be bridgeable to a watt mono configuration. Similarly, a watt per channel four-channel amp might be bridgeable to a watt per channel stereo configuration. You must use a 4-ohm or higher speaker load when bridging. Very few amps can handle using anything less than 4 ohms in the bridged mode.

Be sure to follow the instructions included with the amp for the correct bridging procedure and connections—not all amps are alike. Series wiring refers to connecting multiple speakers or the two sets of terminals on dual voice coil woofers as shown in Fig. Notice that the plus terminal of one speaker or set of terminals is always connected to the minus terminal of the other.

This is so both speakers or voice coils are driven in phase with each other. Calculating the combined impedance of series-wired speakers is easy—just add up the individual impedances. This is true for any number of speakers. Parallel wiring refers to connecting multiple speakers or the two sets of terminals on dual voice coil woofers as shown in Fig. Calculating the combined impedance of parallel-wired speakers is more complicated.

You need to add up 1 over each of the individual impedances, then take 1 over the total. This formula works for any number of speakers.

Once you understand the two basic calculations, you can calculate the impedance of combined series and parallel configurations. All you need to do is break the problem down by calculating simple series or parallel pieces of the configuration first. This is usually 2 ohms for nonbridged amps and 4 ohms for bridged amps, but you should check the specs of any amp you plan to use.

You should avoid series wiring of speakers, with two exceptions—series wiring of the two voice coils of a dual voice coil subwoofer and series wiring of two opposing drivers mounted in an isobarik system. Wiring drivers in series otherwise can cause the back EMF of one driver to modulate the other driver, increasing distortion. These two factors are interrelated, since the type of enclosure you choose might depend on the amount of assembly you prefer, and the amount of assembly you prefer might depend on the type of enclosure.

Subwoofer Amount of Assembly Options If you plan to use one of the powered subwoofer configurations, then your subwoofer and box are already designed and assembled for you.

Otherwise you have the flexibility to choose the amount of assembly you prefer. The three possibilities are shown in Table A ready-made subwoofer is by far the easiest approach, and is sure to look professional. For people who have no interest in delving into box science or construction, this is the way to go. If you choose this route, either buy a product with a solid reputation or audition before you buy.

Installing component drivers in a prefabricated box gives you the flexibility to choose both enclosure and drivers without having to build the TABLE Subwoofer Amount of Assembly Options Amount of Assembly Comments Ready-made subwoofer The easiest approach, and sure to look professional. No guarantee of good sound quality. Component woofers in a prefab box Gives you the flexibility to choose both enclosure and drivers without having to build the box yourself.

Can save money compared to ready-made and provide better performance. Build your own box If you have basic woodworking skills, can save a lot of money. Lets you create any size and shape enclosure you wish, making best use of odd space.

If you choose your speakers wisely, you can save money compared to ready-made and get better performance. Advice on choosing a speaker and box is given later in this chapter. Prefabricated boxes are available in a variety of sizes, shapes, and types sealed, ported, bandpass to accommodate almost any size driver or drivers. They generally come carpeted and have speaker terminals installed.

Some prefabricated boxes are custom made for specific applications. If you have basic woodworking skills, building your own box can save a lot of money. It also lets you create any size and shape enclosure you wish, making best use of whatever odd space is available. Box design and construction are covered later in this chapter. Why use a box at all? The basic answer is that the back of a speaker makes as much sound as the front, but of the opposite polarity.

In practice, speakers without any enclosure will provide some high frequencies and mid-range, but no deep bass. This is because the sound from the back of the speaker gets delayed due to a longer reflected path to your ear. This causes sound cancellation at some frequencies especially low ones but reinforcement at others. Using an enclosure is the practical solution to this problem. The most popular enclosure types for subwoofers are shown in Table Free-air or enclosureless subwoofers are designed to be mounted on the rear deck or behind the backseat, using the trunk as a large speaker enclosure.

Car Audio Systems For the Total Newbie

The idea here is for the trunk to isolate all of the sound from the back of the speaker, thus avoiding the problem of sound cancellation explained previously. Assuming you have a trunk and a suitable mounting location, free-air subwoofers eliminate the need to build or buy a box.

The problem is that most trunks do not provide good sonic isolation. This means that sound from the back of the speaker can be heard in the passenger compartment, canceling out deep bass. To check this for yourself, have a friend with a deep voice talk into your open trunk from the outside. You should be listening inside the passenger compartment with the windows rolled up. If you can barely hear your friend, then a free-air subwoofer will work in your car.

Otherwise, choose one of the other options. Using a sealed box effectively prevents sound from the back of the speaker from being heard, but also affects the sound coming from the front of the speaker.

The air inside a sealed box acts like a spring, effectively changing the behavior of the speaker. How this affects the sound depends on the size of the box and the particular driver. Sealed boxes offer a number of advantages over the other enclosure types.

They are the easiest box type to design and build. Eliminates the need to build or buy a box. Poor performance in most cases due to poor sonic isolation of trunk causing deep bass cancellation.

Car Stereo Cookbook

Sealed Easiest box type to design and build. Woofer is protected against turnon thumps and subsonic bass. Provides the deepest bass if you must use a small enclosure. Cannot provide bass as deep as the other enclosure types for large enclosures. Ported More difficult to design and build than sealed systems. Provides no woofer protection against turn-on thumps and subsonic bass. Can provide bass at least an octave deeper than sealed boxes for a given driver.

Requires a much bigger box than sealed systems. Bandpass More difficult to design and build than either sealed or ported systems. Produces sound over a narrow frequency range, reducing the requirement for a steep low-pass slope in a subwoofer crossover.

Transmission line Elaborate and expensive construction required to create the internal labyrinth structure. Possible to achieve deeper bass than with a sealed box. This is a big benefit if you are planning to use component woofers in a prefab box. The spring effect of air in a sealed box provides woofer protection against turn-on thumps, subsonic bass energy, and going over bumps. Sealed boxes provide the deepest bass if you must use a small enclosure. The big drawback of sealed boxes is that they cannot provide bass as deep as the other enclosure types for larger enclosures.

Ported enclosures make constructive use of the sound from the back of the speaker. Because of this, it becomes possible to achieve deeper bass than with a sealed box. In a ported system, the sound from the back of the speaker produces a resonant output at the port, much like producing a tone by blowing air across the mouth of a soda bottle. The first step is to ditch your factory speakers and replace them with premium units.

Premium speakers are made out of higher quality materials, so they sound better and last longer than factory speakers. That alone will typically result in a huge improvement over the factory sound. That might sound like a lot of nonsense, but it basically means that the amplifier will be able to sit between your factory head unit and your new speakers and allow you to turn your music up without any distortion.

When you add one or more amplifiers, you also have the option of adding a subwoofer.

That will provide you with richer bass, but you can also add a digital sound processor to improve the sound from all of your speakers.

There are a lot of options when you build a car stereo system from the ground up, so a lot of newbies shy away from that sort of drastic change. If you really want to dive in, you might want to start by considering the types of features you want out of your car stereo, which can help you find the perfect head unit.

That can be accomplished in one of two ways:. Powered subwoofers are simpler, but adding an amplifier and a subwoofer gives you more flexibility. Either way, a subwoofer is the best way to get that bass pounding.

If you're after the absolute easiest way to add more bass to your car audio system, then a powered amplifier with speaker-level inputs is the way to go. These units combine an amp and a subwoofer into one unit, so there isn't any guesswork, and they can be hooked up to any factory or aftermarket head unit.

This is the absolute easiest way to install a new head unit, and it ensures that you can pop the factory stereo back in any time you want. Share Pin Email. Jeremy Laukkonen is a tech writer drawing from experience as a technology ghostwriter and as the creator of a popular blog and a video game startup.

Updated October 30, Go sit in your car, close the doors, and crank up the windows. Put on your favorite CD and turn up the volume. Listen to the music. There are a lot of different ways for a newbie to tear into a factory sound system upgrade, so there are a handful of questions that can help set you on the right path: