Not too long ago, we took a look at how speaker-level line output converters worked. We discussed the difference between passive and active devices and explained what features to look for. If you have a vehicle with a premium factory-installed sound system, those interfaces might not be adequate to provide your amplifier with a signal that will sound good with new speakers. So let’s look at some of the intelligent car audio speaker-level interfaces available and why they’re the best choice to upgrade your stereo.

Factory-Installed Audio Systems are Complex

While modern factory-installed sound systems might not use the best speakers and are often limited in power delivery, the signal processing included in them can be pretty complex. Companies like Bose, Panasonic and Harman (the brand behind JBL, Infinity, Lexicon, Mark Levinson, Bang & Olufsen and Harman Kardon) know a LOT about optimizing their products to sound the best they can. So while an aftermarket system might sound better with larger subwoofers, better speakers and more powerful amplifiers, these companies and their technicians are masters when it comes to system configuration and calibration.

A prime example of the capabilities of these companies is the Mark Levinson system in the Lexus LS. There are 23 speakers, including four in the ceiling. The system has a state-of-the-art upmixer that takes a stereo audio track and creates left, center, right, left side, right side, left rear, right rear, front overhead and rear overhead channels. The signals going to each channel are unique, so the system reproduces audio as though you were in a live venue with the stage in front of the listening position. In addition, the system has 2,400 watts of power, so it gets good and loud.

Upgrading these audio systems is complicated. It requires careful planning and accurate measurement of the audio signals that will be used for the upgrades and testing of signal routing for different frequencies and audio sources. This isn’t something you’d want to undertake in your driveway.

Intelligent Line Output Converters

In a more conventional factory-installed audio system, upgrading is less involved but still complicated. Crossovers, equalization, all-pass filters and signal delays are expected on systems with door and dash speakers in the vehicle’s front. Thankfully, a few companies have created line-output converters with built-in digital signal processors that can undo these features and provide a reasonably wide bandwidth signal that’s phase-coherent – like you’d get from an aftermarket source unit.

When the technician upgrading your audio system completes the wiring, these processors require a calibration step. Most include an audio track to be played through the system while the software analyzes the audio signals being produced. Once the measurement step is done, they analyze the information and configure the digital signal processor to undo equalization and signal delays, and combine signals from multiple channels. Once complete, your installer can move on to configuring your new system.

What Happens if You Don’t Undo Signal Processing?

Some upgrade methods work from what the OEM audio system offers. In those instances, you’ll need a digital signal processor with dedicated inputs for each channel from the factory amp. In addition, the system will need to use similar drivers and stock locations. For example, suppose you want your installer to build new A-pillar pods or use speakers that operate in the frequency range where a crossover existed in the factory stereo. In that case, intelligent line-output converters (or a DSP with these features) are necessary.

Let’s look at a simple example of combining two audio signals where one has been delayed from the other by a few milliseconds. This would be akin to using an active line-output converter to combine door and dash speaker signals.

The graph above shows the frequency response of our original signals in red. I applied a 0.6-millisecond delay to one signal, then combined the two to produce the orange trace. As you can see, the frequency response is a disaster. That curve is what’s known as a comb filter, as it looks sort of like a comb you’d use to straighten your hair before work or school. Signal delays are just one of the reasons why it’s crucial for the installer working on your vehicle to understand what’s happening in the time domain and the frequency domain for each channel of your sound system.

Choose Your Upgrades Wisely

If you’ve read this and think, “I have no clue what they are talking about,” that’s 100% OK. This is where you need to choose a professional mobile enhancement retailer to help you upgrade your car audio system. You’ll want to ask them what test equipment they have to measure the frequency and phase response of the factory-installed audio system before you let them work on 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.

A digital signal processor, or at the very least some type of equalizer, is pretty much a requirement when it comes to creating a car audio system that will have realistic tonal balance. There are dozens of methods to configure and tune these processors, and each has benefits and drawbacks. What seems to be an ongoing issue is the need to have someone with the proper training and tools execute the process. The so-called “Golden Ears” method doesn’t work. This article will look at some of the expertise required to complete this process, along with the equipment necessary to deliver accurate and reliable results.

Is It Tuning?

Describing the process of setting up a digital signal processor for a car has long been described as tuning. While technically correct, this term carries the implication that it’s an art form rather than a process. We think a better word to describe the process is calibration. The technician working on your car will take a measurement, perform an adjustment and repeat the process until the final goals are achieved. This process doesn’t require a unique skill set but does require proper tools and training.

The Engine Management System Analogy

If you’re into cars or trucks, then you’ve likely seen the thousands of options available to set up an electronic ignition and fuel injection system for a modern vehicle. At the most basic level, ignition timing and fuel delivery maps are required to let the engine know how much gas to squirt into the cylinders and when to fire the spark plugs. These three-dimensional tables aren’t much different from the signal delay, output level and equalization settings in a car audio DSP.

Start with the Basics

If you buy a stand-alone engine management computer for a project car, something like an AEM Infinity or Holley Terminator X, the starting point is to tell the system what it will be controlling. Your technician needs to set up the crank position sensor and confirm that it’s reading the true mechanical top-dead-center of your engine. Next, they’ll need to configure fuel injector information to let the computer know how much fuel they can flow. They will also need to set up any O2 sensors and a MAP sensor. If there are fuel and oil pressure, temperature, cam position and throttle position sensors, the list goes on and on. The tech will need to understand the calibration of each of these sensors and enter that into the software long before he or she tries to start the engine for the first time.

On a DSP, your mobile enhancement technician needs to set up the signal inputs and configure how those will be routed to the channels of the processor. Next, they have to set crossovers for each channel based on the speakers in the vehicle. This requires an understanding of the speakers’ capabilities, where they are installed and what drivers are being used in adjacent frequencies. They also need to understand what type of crossovers to use to deliver the smoothest frequency response while protecting the speaker from damage. On the latter, how loudly the system will be played has a significant role in setting filter frequencies.

The technician can now move to set signal delays. Whether they use a tape measure or an acoustic technique using impulse tones, these settings need to be close to right before the frequency response calibration process starts.

System Calibration Ensures Accurate Performance

Once the engine is up and running, it’s time to start making measurements and adjusting the fuel and timing tables. The engine or vehicle will need to be installed on a dynamometer to provide the engine with different loads at different speeds. The technician will work through the fuel map while reading from one of several wide-band oxygen sensors to calibrate the amount of fuel the injectors feed into the engine. At the same time, the ignition timing needs to be adjusted for a similar table to tell the spark plugs when to fire in each revolution of the engine. Getting these settings right works in conjunction with fuel delivery, as firing the spark plug at the wrong time might result in not all the fuel being burned. Too much timing or too much ignition advance can damage the engine. The technician will monitor power production in each table cell (engine speed versus load) to optimize the system.

Back to our audio example, once the system is up and playing, the technician will use a calibrated audio analyzer to examine the frequency response of each channel in the audio system. Again, they are looking to ensure that reflections and resonances caused by the vehicle interior haven’t changed the sound at the listening position.

Since it always happens, they use graphic or parametric equalization to compensate for these changes. But, just as with the engine management system, too much adjustment can also lead to speaker damage. Likewise, the technician needs to examine and fine-tune the interaction between speakers running in adjacent frequency ranges or on the other side of the vehicle. Those with the tools and training to do so will also measure the phase response of the system to further fine-tune the calibration. Properly configured phase response is part of what helps to produce “up front bass” in an audio system with a subwoofer in the cargo area or behind a seat.

Calibration Equipment is Crucial

You’ll note investment in equipment is required to complete either calibration process. On the engine side, a wide-band oxygen sensor and a dynamometer are necessary to evaluate how each change to fuel delivery and timing affects the engine’s performance.

A calibrated real-time analyzer and appropriate test tones are the primary tools on the audio side. In addition, an audio analysis system that includes a time-referenced measurement is necessary for more advanced tuning with phase evaluation.

What if someone tries to calibrate either system without these tools? Is the infamous “butt dyno” going to be able to pick out a deficiency in a particular cell of a fuel or timing map? Would ¼-mile timeslips let them know if day-to-day drivability is smooth? Tools are a necessity to ensure proper optimization.

Is It Right or Wrong?

In an engine management system, lack of optimization might reduce the maximum power that the engine can produce and reduce fuel efficiency. If it’s too far out of what’s ideal, the engine can overheat, or in the other direction, pre-detonation or knock might occur that can damage a piston. Ideally, the engine should run smoothly and deliver excellent power and fuel economy at all load conditions

If things aren’t configured properly in a car audio system, there is a chance that a speaker or number of speakers could be damaged by overdriving them. In most cases, the audio system won’t sound right. For example, voices might not sound realistic. They might be too bright or have too much bass information. If the delay and level settings aren’t correct, vocals and instruments may sound as if they are coming from the incorrect location on the soundstage, the sounds might be blurred, or there may not be a soundstage at all.

Choose an Expert to Calibrate Your Car Audio System

Just as you wouldn’t let an amateur calibrate a high-performance race car engine, it’s paramount that you choose a technician with the experience and tools required to design, integrate, configure and calibrate your car audio system. If you choose the wrong shop and technician, you may not get the most from your investment, and the system might not sound impressive. In a worst-case scenario, the speakers could be damaged if you turn up the volume. So make sure you audition several systems the shop has created and make sure they can deliver those same results in your car or truck before you agree to hire them.

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.

Whether it’s Black Friday, Christmas, Back to School or just a regular sale, many car stereo shops around the country offer subwoofer system upgrade packages that let you add bass to your stereo at an affordable price. These packages typically include a 200-300 watt amplifier, a single subwoofer, an enclosure and an installation kit. We’ve noticed a trend in the choice of enclosure included in these systems. We want to offer some advice on an upgrade that will dramatically improve performance and value.

Sealed Versus Ported Subwoofer Enclosures

The goal of these car audio subwoofer upgrade packages is to deliver an affordable way to add bass to your vehicle. As such, the products these systems include are typically chosen based on their price rather than their combined performance. Most options include a 12-inch subwoofer and a sealed enclosure. While this combination works well, it might not offer the best bang for your buck. Let’s look at an example.

Let’s use an ARC Audio X2-Series X2-12D4 12-inch subwoofer as an example. It’s not an entry-level subwoofer compared to some of the low-cost options on the market, but its performance, build quality and capabilities make it worth every penny. The sub is rated to handle 250 watts of power. Let’s model it in a sealed enclosure with a net internal air volume of 1 cubic foot.

As you can see, the response curve is nice and flat. By way of specifications, the system has a Qtc of 0.894 and an F3 frequency of 42 Hz. These numbers are ideal terms of delivering clear and accurate bass.

Less Subwoofer, More Enclosure

What if we switch things up a bit and go with a 10-inch subwoofer in a vented enclosure? This cost of the system might go up a little bit, but is it worth it? Let’s model the 10-inch version of that subwoofer in a vented enclosure with the same net 1-cubic-foot internal air volume. For this simulation, the enclosure has a tuning frequency of 33 Hz.

You’d think we knew what was going to happen before we started writing, wouldn’t you? The 10-inch sub in the vented enclosure is louder at all frequencies between 20 Hz and 75 Hz. How much louder? We made this chart below to show you.

If the two systems’ differences were less than a decibel, the comparison would be a wash. The 10-inch sub in the vented enclosure produces around 3 dB more output from 40 to 50 hertz. This increase in output level is significant.

System Efficiency and Power

Aside from getting more output for a similar investment, there’s another way to look at this. Let’s say you want to listen at a specific volume level. The subwoofer in the vented enclosure can produce that output with less power. This means the amp won’t run as hot, the subwoofer won’t heat up and the amp will draw less current from the vehicle electrical system. We’ll add a power comparison to our graph above to show you just how much less is required for the same output.

In the chart above, we compare the output of the 12-inch driver with 250 watts to the amount of power the 10-inch driver in the vented enclosure requires to produce the same result. At 45 hertz, the requirement is less than half the power. This equates to much less current draw on the electrical system in your car. It also means the voice coil of the subwoofer won’t heat up as much. This reduction in power to the sub can help reduce power compression and further improve the efficiency of the subwoofer system.

If you are wise with your purchasing strategies, you might ask if there are any drawbacks to using a vented enclosure instead of a sealed one. So long as the enclosure has a large enough vent and includes a smooth radius around the vent opening, there aren’t any issues. In addition, you can see that the overall shape of the response curve is similar to that of the sealed design, so the system will sound similar. In all honesty, it’s a win-win situation.

Upgrade Your Car Audio System with a Subwoofer

One of the best upgrades you can make to your car audio system is to add a subwoofer. So drop by a local specialty mobile enhancement retailer today to find out what’s available for your vehicle. If they have a subwoofer system package available, ask about upgrading to a vented enclosure. The improvement in efficiency will be worth every penny.

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.