Having a digital signal processor in your car audio system is a necessity if you expect your music to sound accurate. We’ve told you many times that speakers are essential to getting great sound. While 100% true, so is the need to calibrate the output of those speakers to work with the acoustics of the environment. Proper equalizer configuration is the only way to make your audio system sound genuinely realistic.

In this series of articles, we’ll look closely at the features included in a digital signal processor and explain how each of those functions improves the performance of your mobile audio system. We’ll also give you some tips to help you find a retailer who has the tools and training to optimize your stereo efficiently and reliably.

What Is Signal Processing?

For decades, car audio systems used analog crossovers and equalizers with sliders or knobs to allow installation technicians to configure and calibrate the signals going to each amplifier. Tens of thousands of hours have been spent tweaking AudioControl, Phoenix Gold, Precision Power and Image Dynamics analog equalizers over the years.

The problem with analog processing is its accuracy. The values of resistors, capacitors and potentiometers in analog circuits varies by temperature and sometimes by age. Another problem is accessibility. Since these devices are somewhat large, tuning a vehicle typically involves repeated trips from the driver or passenger seat to the trunk to make adjustments. This dramatically increases the time it takes to configure and calibrate the system. Finally, there is the issue of repeatability. If you want two different configurations, you can’t reliably change the settings, then hope to return them to their original configuration and have the system sound exactly the same each time. Potentiometers are by nature, nearly infinitely variable. Even a difference of only a few degrees can dramatically change the value of an EQ or filter setting.

According to the definition provided by Analog Devices (a company that manufactures DSP integrated circuits), a digital signal processor (DSP) is a device that takes real-world signals like voice, audio, video, temperature, pressure or position that have been digitized and mathematically manipulates them. A DSP is designed to perform mathematical functions like “add,” “subtract,” “multiply,” and “divide” very quickly. Many companies manufacture DSP chips, and some car audio product manufacturers will note the specific unit they use. Products like Blackfin, SHARC, Sigma from Analog Devices, Symphony from NXP and Velvet Sound from Asahi Kasei Microdevices get name-dropped quite frequently.

In a DSP, the interface between the person configuring the processor and the system is computer-based. Once a system is calibrated, the settings can be saved to a file on the computer. Every time the processor turns on, the software applies the exact same signal modifications. The results are repeatable and predictable.

Processors with adequate memory can store multiple presets. You can have a system calibration for use when only the driver is in the vehicle, then another for when the car has people in the driver’s and passengers’ seats. You may even want a third calibration that raises the crossover points a bit so you can play the system at higher levels without fear of damaging speakers.

When to Use a DSP in a Car Audio System

If you want your music to sound realistic, then you need some form of equalizer in your mobile audio system. Praying that a new set of speakers will magically compensate for the reflections and cancellations in your specific vehicle is a fool’s errand. They won’t, and they shouldn’t. To compensate for the acoustics of the vehicle, you need a DSP with at least 30 bands of graphic equalization on both the left and right channels. You can get away with fewer bands if you are using more channels. For example, 10 to 15 bands of EQ are more than enough on a woofer or a midbass channel. We’ll explain equalizer functions in detail in Part 4 of this series.

Most car audio systems use a dedicated amplifier for the subwoofers and a separate amp for the midrange and high-frequency speakers. Getting the crossover settings between these amplifiers right is crucial to ensuring the bass and midbass in these systems sound good. If the system is more elaborate, it may have dedicated amplifier channels for the tweeters, at which point the DSP needs another set of filters. If you have midrange and midbass speakers, then you need yet another set of amp channels and filters. Most high-end car audio systems use a four-way system with dedicated subwoofers, midbass, midrange and tweeter channels. We’ll explain more about crossovers in Part 3.

The technician setting up your vehicle will likely want to apply some delay to the speakers closest to the listening position, or delay the front and rear speakers so that the sound from them arrives at the same time as sound from the subwoofer. We’ll explore signal delay details in Part 5.

Beyond equalization, crossovers and signal delay, many processors include signal mixers to combine signals from different channels or sources into something that can be used in the upgraded system. Finally, companies like ARC Audio, Audison and AudioControl have processors that will work with the ADS Maestro AR amplifier replacement module to allow your installer to integrate your system directly to your factory radio while maintaining proper mixing of warning chimes and navigation prompts. We’ll look at this more in Part 2.

When Not to Use a DSP

There are cases where you shouldn’t invest in a digital signal processor. If your installation technician doesn’t have a high-quality microphone to calibrate the system, there is no way to make the car sound good. Likewise, if the technician hasn’t installed several processors in the past, they likely don’t have a defined process in place that will ensure that your vehicle will sound good. Since you’ll be paying for the calibration process, you should know how long it’s going to take before work begins.

Speaking from experience, configuring basic settings like crossovers, signal delay and output levels within a DSP is easy. The process of equalizing each speaker in the vehicle and knowing how to deal with the anomalies that pop up can be much more challenging. It’s crucial that the technician you choose to calibrate your system understands what he or she is doing. They should have experience tuning many systems in the past. While tuning isn’t an art form, it is a complex process that requires formal training and hours of practice. It’s not something that can be figured out on the fly or that can be done by ear.

Upgrade Your Car Audio System with a Digital Signal Processor

If you’re interested in having your car audio system upgraded with a digital signal processor, start your shopping process by auditioning systems that have been tuned by the technician who will be working on your vehicle. You want to know that your audio investment in an audio system upgrade will yield similar results. Not everyone is well-versed in calibrating digital signal processors – even some technicians who are great fabricators.

As always, we suggest you start with a local specialty mobile enhancement retailer. In this case, it might be beneficial to shop around a bit. Listen to as many demo vehicles as are available. Listen to the same music in each one. Learn what you like, then talk to the Product Specialist you are dealing with about those criteria so they can be recreated in your vehicle.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

As we’ve mentioned before, upgrading the audio systems in new cars and trucks is becoming more and more complicated. Features like crossovers, all-pass filters, volume-dependent loudness control and equalization can make the stock system sound respectable with stock speakers, but they present a significant challenge to drivers when it’s time to upgrade. Let’s look at why crossovers are used and how your installer can deal with them during an upgrade.

What Is an Electronic Crossover?

A crossover is an analog electronic circuit or a piece of code in a digital signal processor that attenuates an audio signal above or below a specific frequency at a specific rate. Crossovers allow speakers to operate within a specific set of frequencies, most often to protect them from damage. For example, if you have a woofer or subwoofer in your vehicle and small midrange speakers in the doors or dash, you don’t want to send hundreds of watts of power to those small speakers. The amplifier will have two crossovers: a low-pass filter that sends bass to the woofers and a high-pass filter that sends high-frequency information to the midrange speakers.

Why Do Crossovers Matter When Upgrading Speakers?

Let’s use an example of a premium factory audio system in a modern vehicle. Many of these systems have a small subwoofer in the rear of the vehicle, woofers in the doors and midrange drivers and maybe tweeters in the dash and A-pillars. In most cases, the amplifier will have three sets of channels to drive this configuration: a pair for the mids and tweeters, a pair for the woofers, and something for the subwoofer. If we had to apply our a crystal ball prediction to the crossover points, we’d guess around 80 Hz between the woofer and the subwoofer, and around 300 Hz between the woofer and the tweeter.

Let’s say you want to upgrade the audio system in this car with speakers that can handle a lot more power and produce more output. This is a common project. If your budget is limited to using a standard two-way component speaker set (a set with two 6.5-inch woofers and two tweeters), then your installer will have a problem getting a suitable signal to power the new speakers. If your technician uses the woofer signal, you won’t hear much in terms of vocals. If he or she uses the mid and tweeter signal, you won’t have any midbass.

While we avoid making any absolute statements, we will say, without any hesitation, that your installer cannot just twist the two sets of wires together to combine the signals. Likewise, no devices can be added to the speaker wires to combine the signals and drive the new speakers.

Dealing with Crossovers in OEM Audio Systems

There are three options to deal with this configuration. Option one is to upgrade with a three-way speaker set that includes woofers, midrange drivers and tweeters. Assuming the frequency limits set by the factory amp work with the speakers you have in mind, this will likely be the easiest upgrade.

Option two is to add an integration processor or a DSP with factory stereo integration features to upgrade the system. These processors can recombine audio signals after they have been filtered by crossovers to create a usable signal that can be sent to new amplifier channels. This method sounds pretty good.

Option three is an amplifier replacement module and new amps. Executed properly with a new DSP, great amps and speakers, this will be the best sounding option. Ditching the tuning built into the factory amp will let your technician upgrade the vehicle with whatever speakers you want and calibrate the system to sound great. Of course, this will be the most expensive option, but every aspect of the system’s performance can be addressed.

What About Passive Signal Summing Devices?

Some basic analog signal summing devices are available. These units can take the woofer and midrange audio signals and combine them. If your technician has a way to check whether the crossover points, slopes and signal equalization on both channels are absolutely identical, then you might be able to get away with this. Unfortunately, those conditions almost never happen. The result is typically very poor sound quality with what’s known as comb filtering. Comb filtering looks like a series of frequency response dips and is caused by phase issues between the two signals that are being combined. In short, this is risky at best and is unlikely to result in improved sound quality.

Who Should Upgrade Your Factory Audio System?

I know we’re starting to sound like a broken record, but it really is getting harder and harder to upgrade the stereos that come in new cars. It’s not just the fancy Bose, JBL, Lexicon or Burmester systems either – even base-model sound systems without external amplifiers include small digital signal processors right in the radio to improve the performance of the factory speakers. When it’s time to upgrade that boring stereo in your car or truck, start by visiting your local specialty mobile enhancement retailer. Ask them how they deal with audio systems that include crossovers and equalization. Based on their response, you can upgrade your stereo or continue your search for a retailer with the tools and training to make your stereo sound amazing.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

Over the years, we’ve highlighted car audio installations that look amazing and we’ve explained some of the science that goes into making those systems sound great. A professional car audio installation technician needs to possess a unique set of skills that includes a certain amount of creativity, as well as a detailed understanding of how vehicles and audio components work. If either area of expertise is lacking, the result of their efforts may not sound right or look as though it belongs in a vehicle. It’s a tricky balance that requires years of training and hours of planning for a complicated build.

The Art of Car Audio Installation

When it comes to creativity in the design and execution of a custom car audio installation, coming up with unique locations to mount amplifiers and processors, to integrate the cosmetics of an upgraded set of speakers or to highlight something like a plexiglass subwoofer enclosure isn’t easy. Many professional technicians have taken to making sketches of the components they plan on creating. This process can help clients understand why the project will take a certain amount of time.

Imagine a speaker upgrade in the door of a classic sports car. Likely, the vehicle didn’t come from the factory with a 6.5-inch woofer in the door. There are probably a few dozen options for mounting a new speaker in that door. The technician could cut a hole in the trim panel and the metal frame of the door, then install the speaker with its included grille. If the door is any color other than black or gray, the tech might choose to paint the grille to match the interior of the vehicle.

Many low- to mid-price speakers come with grilles that include modern, angular styling that might not fit with the lines of the vehicle. In this case, the technician may choose to make a trim ring around the speaker basket, create a grille and cover it with acoustically transparent cloth.

If there’s going to be a lot of work done in the vehicle interior, then adding a theme to the installation might be something the client would enjoy. This theme could carry into the cargo area in the form of a custom amp rack or subwoofer enclosure. Many high-end installations combine the use of vinyl, laser-cut acrylic plastic and pressed metal mesh to create a solution that looks as though it rolled off the vehicle assembly line.

Car Audio Upgrade Science

As important as it is to ensure that the new car audio products installed in a vehicle look as though they belong, the technician needs to keep the laws of physics in mind. Simple things like the placement and angle of the tweeters in a set of sail panels or dash can play a significant role in how the driver and passenger hear the highest audio frequencies.

Installers need a firm understanding of how to combine different-size speakers based on specifications like resonant frequency while taking into account directivity concerns due to cone diameter. This information, combined with measurements from acoustic analysis equipment, will affect crossover points.

There are hundreds of factors to take into account during a modest to complicated audio installation. Technicians have to consider where to route wires to prevent noise interference. They have to plan how to run power cables to avoid damage from heat and vibration. They need to know what signals they need to test to add an amplifier or processor to a factory radio.

The process keeps changing, and new vehicles introduce new technologies. Where once an installer could trust the chassis of a car or truck as the ground path for a high-power amplifier, alternatives need to be used in vehicles with aluminum construction or where adhesives are used instead of spot welds. These are a small percentage of the reasons why so many professional installers invest thousands of dollars each year in training.

Choose Your Installation Technician Wisely

We aren’t afraid to state that, sadly, not every person installing car audio equipment for a living is qualified and adequately trained for the task. As a consumer, your job is to choose a company that provides the right combination of services to ensure that your upgrade will look and sound great and last for many years. You can start the process of shopping for a qualified retailer by visiting the local mobile enhancement specialists in your area. Be sure to take note of the class of cars they are working on, any certifications their technicians have on display, and the brands they sell. All of these factors can provide insight into their capabilities.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

When it comes to correlating how the parameters of a speaker translate into music reproduction, well, the details are often somewhat sparse. One speaker characteristic that’s often overlooked when searching for new subwoofers or woofers is Q. This unitless number is a key component in describing how the suspension and motor work to control and damp cone oscillation at its resonant frequency. Different Q values affect efficiency, frequency response and, ultimately, sound quality. It’s not an intuitive topic, but understanding Q factor is crucial to picking the best bass solution for your car audio system. This is a full-propeller-beanie discussion, but it’ll be time well spent.

What Is Speaker Q?

If you’re an audio aficionado, then you may have heard of speaker specifications called Thiele/Small parameters. These specifications can be used to simulate and predict the low-frequency performance of a loudspeaker. Three of the specifications relate to a topic called Q. Q (or quality factor) is a unitless number that describes how underdamped an oscillating circuit is. A higher Q value means that the circuit or system has low damping and will ring or resonate for longer.

Here’s an analogy that might help you understand. Do you know those springy little door stoppers that kids like to play with? They go boing when you flick them. In the right setting, they’re somewhere between entertaining and amusing. After a few dozen flicks, they become annoying. They have a high Q factor. They bounce back and forth for a few seconds after the initial input (a flick of your finger) is applied.

If you were to apply a piece of electrical tape to the top of the door stopper, it would act to damp the vibrations. The effect would lower the Q of the spring system, and the resonances (vibrations) would stop faster.

For most mechanical or electrical circuits, a Q of 0.5 is considered to be optimally damped. A Q of 0.3 would be over-damped, and a Q of 0.7 would be under-damped. A tuning fork, for example, has a Q of roughly 1,000.

Speaker Q Factor

For the purposes of this discussion, we are going to look at a typical door woofer (6.5-inch) to evaluate how different Q factors affect frequency response. The perfect speaker would have a flat frequency response that’s determined by its Thiele/Small parameters. It would look like this:

Qts is the Thiele/Small parameter that defines the total Q factor of a speaker. The value takes into account both the mechanical and electrical Q factors of the driver, equally.

Most car audio speaker manufacturers don’t fully understand the relationship between Q and frequency response, or they choose to ignore it to deliver a certain “sound.” Unfortunately, when it comes to truly high-end speakers, tailoring the frequency response of the system should be left to an equalizer built into a digital signal processor, and not a characteristic built into a speaker.

Here are the benefits of using a higher-Q door woofer: They are more efficient in the upper bass and midbass region. The extra energy stored in the suspension is released and adds to the output, typically in the region focused around 140 to 160 Hz. If you’re designing an audio system without a subwoofer, the extra bass can be of some help in making the system sound fun.

The drawback is that the extra energy that is stored and released by the suspension is distortion. It’s sound that wasn’t in the original recording. Remember, the suspension of the speaker is a spring. You don’t want it to continue to resonate back and forth after the signal goes away. That back and forth motion not only affects the frequency domain but the time domain. Sounds continue to ring out after the original input is gone. In subwoofers, this is often what’s described as being boomy. In a door woofer, it’s sloppiness. Conversely, a properly damped speaker is often described as sounding “tight” or “fast.” Since speed can’t change, these descriptions are limited in their accuracy.

Shopping for Great Woofers

If your car audio system includes a subwoofer (and it really should), then you’ll want to search for a door woofer that has a low Q. Some 6.5-inch woofers like the Audison Thesis TH 6.5 II and Audiofrog GB60 have Qts values under 0.5. The Morel Supremo MW6, Hertz MP 165P.3, and Focal ES 165 KX3 woofers also have relatively low Qts values. Lower values (0.4 to 0.5) are better, and you’ll want to avoid anything above 0.6 if you have a subwoofer and want properly damped midbass performance.

Drop by your local specialty mobile enhancement retailer and talk to them about how best to upgrade your car audio system to deliver amazing bass and midbass performance and accuracy.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.