No matter how hard he or she tries, the installer who’s calibrating your car audio system can’t use a digital signal processor to tune distortion out of your system. We aren’t talking about the harmonic distortion that happens when a signal overloads the processor or an amplifier’s input stage. Preventing clipping is a simple process and one that’s fundamental to completing an amplifier installation. Every part of the audio chain – from the source unit and processor to the amplifier, speakers and subwoofer — adds (hopefully) small amounts of unwanted high-frequency information from harmonic distortion and lower-frequency products from intermodulation distortion to the audio signal. While that seems like a mouthful, it’s time to take a look at the big picture and how product selection affects the performance of your audio system.

Defining a Goal for Your Car Stereo

You don’t need to be an audiophile or “audio snob” to appreciate the benefits of combining amazing products with proper system design, installation and calibration. The difference that clarity and output capability offered by well-designed speakers and proper installation deliver, as compared to low- to mid-quality speakers, is easily discernable by even the most amateur music enthusiasts.

Here’s the first step. Find a song you like. Choose something you’ve listened to many times and really enjoy. Now, play it on your smartphone with the phone sitting on your kitchen table. Turn it up fairly loud. Now connect your phone to a Bluetooth speaker like a JBL Charge 4 or something similar. Listen to that same track again, and more particularly, listen for the differences in the way it sounds. Chances are, you’re going to hear a lot more midbass and drums, and other bass instruments will now start to stand out in the mix.

If you have a good home audio or home theater system, listen again at a similar volume level. If that audio system has a subwoofer, chances are the bass information will have more low-frequency extension, and voices and other midrange instruments will sound clearer. If you don’t have a good home audio system, ask a friend if you can listen to it on their system. Now you have a basic idea of how better audio systems change the way your music sounds.

The last step is to head to a local specialty car audio retailer and ask to audition the song in one of their demo vehicles. If the audio system is designed, installed and calibrated properly, you should hear the music laid out in front of you in what’s called a soundstage. The car or truck’s dashboard should recreate the space where the performers in the recording were situated in the recording studio or on the stage. The balance of the bass to midbass, midrange and high-frequency information should be smooth, and nothing should stand out. It should sound as though you’re sitting at the console of the recording studio.

Let’s Talk about Audio Clarity

Clarity, as defined by the Oxford Dictionary, refers to “the quality of transparency or purity.” Think of a photograph for a second. If you take a photo with a kid’s Fisher-Price camera and the same image with a Sony α9 II with a prime FE 50 F1.2 GM lens, the difference in the detail and color accuracy will be readily apparent. This is why high-end cameras exist – to capture a scene or moment with improved clarity.

Look carefully at the two photos above. The sharpness in the leaves is gone in the lower photo. The detail in the water droplets and the texture in the rocks have been lost. The color balance and the exposure of the images are completely different. Once the accuracy of the original experience is gone, it can’t be restored.

When you’re listening to music, clarity works the same way. The balance between the instruments and performers in the recording was determined by the recording and mastering engineers. That mix was referenced to the monitor speakers and the system calibration in the studio control room. That’s as “accurate” as that song will ever get. Moreover, what each performer or instrument sounds like in the recording studio or on the stage isn’t the reference for accuracy. The front row center seat or the “sweet spot” in an auditorium isn’t the reference either. The recording engineer hears what each of the microphones picks up after they are all combined together and processed. If your audio system isn’t calibrated the same way, or your equipment adds moderate levels of distortion, you don’t hear the same sound. It might still be nice, but it isn’t technically accurate.

What Is Distortion?

Almost everyone who has even a passing interest in car audio equipment thinks that distortion only happens when you overload a component in the audio system. If you ask someone to “draw” distortion, they’ll draw a clipped sine wave. This is an extreme example but isn’t wrong.

In reality, every time we pass an audio signal through an electronic device, (hopefully) small amounts of harmonic and intermodulation distortion are added to the signal. If you were to compare the shape of the original and audio waveform and the signal going to your speakers on an oscilloscope, they’d look very similar to one another. The reality is, small amounts of unwanted information have been added to the experience. Second-, third-, fourth- and maybe fifth-order harmonics, along with the product of multiple sounds being played simultaneously, add themselves to your music.

It’s time for an example. I downloaded a recording of a triangle and imported it into Adobe Audition. I copied the signal from the left channel to the right to ensure that I was dealing with exactly the same content. Then I locked the left channel and applied the distortion processing built into Audition to only the right channel.

If you look closely at the lower spectrogram, you can see that there are more purple lines running horizontally between the 1,650 and 4,570 Hz fundamental frequencies. That’s added unwanted distortion. Let’s look at it another way.

In the image above, you can clearly see the original recording in green and the unwanted content at 1,244, 2,064, 2,891, 3,299, 6,223 and other higher frequencies that have been added in the blue trace. Those are sounds that weren’t in the original performance or recording. That’s distortion.

Can’t My Installer Tune Out Those Frequencies?

I’ve heard people say that adding a digital signal processor (DSP) to a car audio system is a good way to tune out distortion. Sadly, that’s not how they work. The main goal of the processor is to calibrate the output of each speaker in the system to compensate for frequency response issues caused by the vehicle environment.

In our example, we have two frequencies to deal with in the original recording. If this were the only piece of “music” played on the system, then your technician could EQ out the unwanted information. The problem is that different instruments cover different frequency ranges. If you fix the sound of this triangle, you ruin the sound of an electric guitar, piano or violin. The only way to get rid of it is to prevent your audio system from adding it.

Choose High-Performance Car Audio Equipment

You can read any of more than 30 articles on BestCarAudio.com that explain what to look for when shopping for or comparing source units, amplifiers, speakers, signal processors and subwoofers. For electronics, signal-to-noise ratio and Total Harmonic Distortion and Noise are the numbers to check out. Be sure the SNR is compliant with the CTA-2006-C standard, lest you be fooled by inflated peak-power ratings. Since no car audio companies publish distortion graphs for their speakers or subwoofers, you have to look for features like aluminum shorting rings, flat spiders and copper T-yoke caps, or motor designs like eXtreme BL Linearity (XBL^2) or an underhung voice coil design that reduces distortion. Keep in mind that the latter two include some drawbacks along with their benefits.

What’s perhaps the best experience of all is auditioning products under controlled conditions. You CAN hear the difference between good and great sounding head units, amplifiers and speakers. Before you rush out and buy a deal you saw online or guess at the quality of a product you’ve heard about from a friend, drop by a few local specialty mobile enhancement retailers and audition the components you intend to add to your car audio system. Ask them about the product features and designs that improve their performance. Then find out if they have the tools and training to integrate everything into your vehicle and calibrate the system properly with a DSP. It seems like a lot of work, and it is, but it’s worth every second when your music sounds 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.

Look at any of the top car audio subwoofer amplifier models available from specialty retailers. You’ll find that most include an option for a remote level control or bass boost function. Being able to fine-tune the output of your subwoofer system is great for those times when you want to rock out to an amazing song or calm things down so you can talk to a passenger easily. This article will look at how the subwoofer level controls on source units, digital signal processors and car audio subwoofer amplifiers work.

You Can’t Get More than Full Power

Before we dive into the different adjustment options, consider that the maximum output you’ll get from your subwoofer system depends on the excursion capability of the sub and the maximum power available from your amplifier. You can’t get more bass by increasing the signal to the amplifier when it’s already optimized to make maximum power at full volume. With that said, you can get to full power sooner and increase the amount of bass relative to the midrange and high-frequency speakers in the vehicle. Remember that you may need to limit how high you turn the volume control on the radio if this is how your system is configured.

Think of your subwoofer system like the engine in your car. Once you’ve put your foot to the floor and the engine is making as much power as it can, there’s no way to get more power without some significant modifications to the vehicle. If you want more bass than is being produced by your car audio system, return to the retailer that installed the system and talk to them. You may need more subwoofers, larger subwoofers, a different enclosure, a more powerful amplifier or some combination of these items.

Subwoofer Level Controls in Car Audio Source Units

Almost every source unit on the market with electronic crossovers also includes a subwoofer level control function. This control adjusts the level on the subwoofer preamp output RCAs relative to the level on the front and rear RCAs. These source units are configured to work two ways.

The first example we’ll look at is configured the same as the Sony XAV-AX7000 that the BestCarAudio.com team reviewed here. In the subwoofer adjustment menu, when the level is set to 0, the subwoofer output level is the same as that of the front and rear preamp outputs. If you increase the subwoofer level to 10, the output on the sub preamp output increases. This configuration results in you reaching the maximum output capability of the subwoofer preamp outputs with the volume control set to 38 instead of 49. Turning the volume up higher will produce distortion on the sub preamp output. You can also turn the output down to -10 if you find there is too much bass. Lowering the signal has no adverse effect on the outputs.

Other companies configure their subwoofer level controls on a scale of 0 to 10 or 0 to 20. Though the labeling varies from brand to brand and potentially model to model, setting the output level to its highest setting would result in the preamp output being maximized without distortion when the volume is maximized. This configuration prevents the outputs from distorting when the volume is cranked. In an ideal world, the radio’s sub output adjustment labeling would be something more akin to -10 to 0.

Level Controls in Digital Signal Processors

Just as with a source unit, there’s an upper limit to how much voltage can be produced on a digital signal processor’s output. If the DSP is built into an amplifier, maximum output is determined by the voltage and current capabilities and the impedance of the subwoofer(s) connected to the amp. If your system uses a stand-alone processor, then it can likely produce 5 or 8 volts of signal on the RCA output jacks. Most signal processors include a subwoofer level option that can be adjusted with one of their optional remote controls. As a key part of the system calibration process, the technician working on your audio system will need to ensure that the signal remains clean and undistorted when the volume is maximized.

A unique option that ARC Audio includes in its PS8, PSM and PS8 PRO series signal processors is a configurable level control. When the optional LR1 remote is added, your technician can configure which channels it affects and by how much. If you want the LR1 to act as a sub control, it can be assigned to adjust over a range of -20 to 0 dB and be configured to work with the outputs that feed the sub amplifier. The software configurability means that this remote could also serve as a master volume control for the entire system, as a center channel level control or rear-fill speaker level adjustment.

Issues with Adjusting Subwoofer Output Level

Some digital signal processors offer a bass EQ control aside from their graphic or parametric equalizer. These adjustments are more likely to be found in processors that are compatible with the Maestro AR to integrate directly with factory-installed source units. In most of these cases, the bass EQ is a shelf filter that adds a specific amount of boost below a configurable frequency.

There is a problem with adjusting bass output this way. Suppose your audio system is calibrated to a target response curve, and the crossovers are set properly. In that case, the point at which the subwoofer’s output crosses over with the midbass driver’s output should be at the -6 dB point to sum flat in terms of phase and frequency. If you turn the bass up, that crossover point changes. This mismatch can result in some bass frequencies sounding as though they are coming from the front of the vehicle and some from the back.

In reality, applying the shelf control shown earlier to both the subwoofer and the midbass drivers maintains this phase and amplitude relationship, so your audio system sounds its best.

Bass Boost Versus Subwoofer Level Control

Many subwoofer amplifiers include a bass boost control. These are typically a narrow-band equalizer circuit that’s centered around 45 or 50 Hz. Some entry amplifiers have a switch that adds 6 or 12 dB of boost at this frequency, while others have an adjustment potentiometer that allows for a variable amount of boost, usually up to 12 or 15 dB.

Fancier amplifiers add frequency and Q-factor adjustments to the boost level control to allow your installer to fine-tune the system further. Used gently, these adjustments can add some low-frequency emphasis to a sealed subwoofer enclosure to make it more fun.

While these boost circuits can make listening to your music a lot of fun, when used excessively they typically don’t result in smooth and natural sound. If you want your car audio system to reproduce a recording of a set of drums in a way that makes them sound real, lots of bass boost isn’t a great solution. If you want to rock out with your friends to some rap, dance or techno, it can be awesome!

For technicians setting up an amplifier that includes a remote bass boost or remote level control, he or she will need to ensure that the system can play without unwanted distortion with the volume on the radio maximized and the control turned all the way up. The crossover adjustments will need to be optimized for the system’s typical listening preferences to sound its best.

If you’re considering adding a subwoofer system to your vehicle, an upgrade we highly recommend, then drop by your local specialty mobile enhancement retailer today. They can design and install a solution that sounds great and delivers the performance you want. If you listen to many different kinds of music, be sure to ask them about including a remote subwoofer level control in the system design.

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.

If you’ve browsed amateur car audio groups on Facebook, you’ve likely seen someone post that they have “set the gains halfway” on their amplifier. Their misguided theory is that this setting will limit the maximum amount of power the amplifier will produce. Saying this in the presence of a professional installer is the best way to announce that you don’t really know how the sensitivity control on your amplifier should be set to optimize its output capabilities and minimize the noise in your car audio system. Confused? No worries, we’re here to help explain it all.

What Does the Gain Control Do on a Car Audio Amplifier?

Imagine a world where every car radio provided the exact same preamp output voltage at full volume. If you play a song that reaches the maximum allowable recording level for the medium you’re using (CD, cassette, digital audio file or whatever), and you have the volume control on the radio turned up all the way, then you might get a signal that peaks at 2 volts. In this scenario, every amplifier on the market could be configured to produce its maximum rated power when it sees 2 volts of input signal.

In reality, the sources we use to play our music vary dramatically in their output capabilities. An iPod might produce 330 millivolts. An inexpensive radio is likely capable of producing around 2 volts, and a higher-end multimedia receiver or a good DSP might reach or exceed 5 volts. Ignoring the need to balance the relative output level between a subwoofer and midrange speakers (for now), we need an amplifier that can produce full power with signals that vary from few hundred millivolts up to more than 5 volts. The sensitivity control on car audio amplifiers is the adjustment that lets a properly trained technician configure the amp to make its maximum rated power from a variety of sources.

Why Setting Gains Is Crucial

Let’s start with a simple example. You’ve had a subwoofer system installed in your vehicle and you’ve chosen a 500-watt amplifier to drive a pair of subwoofers that are rated to handle 250 watts of power. In the simplest scenario, the technician installing the system should set the sensitivity control on your amplifier so that the amp clips a tiny bit when you max out the volume on a radio that can produce 2 volts of output. If the amplifier is rated to work with sources ranging from 150 mV to 4 volts, then a setting around 2 volts or around 20% from its minimum sensitivity will be pretty close. The technician will check to make sure that the type of music you enjoy will play loudly, then send you on your way to enjoy your upgrade.

Suppose you decide at a later date to update your audio system with a premium multimedia receiver that includes Apple CarPlay and Android Auto. In that case, you might find that it can provide 4 or 5 volts of output on the preamp connections. With this unit in place, the sensitivity controls on your amp are too high, and it would be easy to drive it into clipping. The amp needs to be turned down to just about its lowest sensitivity to make full power at full volume.

The Drawback of Too Much Gain

If you are attentive to listening for significant distortion being added by pushing your amp to the point that it clips, then theoretically, you could leave the sensitivity control at 20%. By lowering it, the amp will add less unwanted noise to the system, and you don’t have to worry about how high you turn the volume. That said, it’s hard not to want to turn the volume up when your favorite song comes on. Noise isn’t much of a consideration with a subwoofer amp, but low- to moderate-quality amplifiers can add a lot of hiss with the gains cranked up when driving coaxial or component speakers.

Amp Gains and Maximum Power Delivery

The correlation between the setting on your amp and how much power is produced is based purely on how much signal is sent to your amp. If you have an extremely low-voltage source like an iPod, then the amp may need to be set at 75% to 85% of its maximum. In this case, turning the amp back to 50% WILL reduce how much power it produces. If the amp is optimized at 25%, then turning it to its minimum will also reduce power.

To state that an amplifier is set “halfway” ignores the variables of source unit output voltages, volume settings, source material loudness, system equalization and the impedance of the load connected to the amp. If you only need 10% of an amp’s gain capabilities, setting it to 50% doesn’t make sense, and it certainly doesn’t limit the amplifier to half its power production capabilities.

It’s Much More Complicated

The sensitivity control is also used to balance the relationship between speaker output levels in actively filtered car audio systems. If you have a 500-watt amplifier for your subwoofer and a 50-watts-per-channel amplifier for your door speakers, setting both so that they clip simultaneously might not deliver an overall system balance that’s ideal. Of course, the design of the audio system matters. If you’re running one 8-inch sub in an acoustic suspension (sealed) enclosure or a pair of 12’s in a bass-reflex (vented) enclosure also plays a huge role in how things will be configured. You also need to take into account that the amp for the door speakers is likely only going to play down to about 80 Hz. Crossover settings complicate the calibration process even further and render tools like an oscilloscope useless without the proper test tracks.

Let’s wrap this up with another example. Say you’re using a high-quality digital signal processor that can provide as much as 8 volts of output to your amplifier. It’s quite likely that you can provide more than enough voltage to drive that amp to or beyond the point that it will add distortion from clipping to the output, even with the amp gain set to its minimum setting. Consider the flawed logic of saying, “I’ll only get half the power if the set the gain halfway.” The reality is, the amp will likely reach its maximum output capability at half to three-quarters of the maximum volume on the radio. If you turn the volume up further, you are just adding distortion to the output signal and risk overpowering the speakers or subwoofers.

Our second and equally illogical example would be a scenario where you have an amplifier that’s capable of overpowering your speakers. Imagine a subwoofer rated for 200 watts connected to an amplifier that could produce 1,000 watts. Is “setting the gain at half” going to protect this sub from damage? If you have an audio source with extremely limited output voltage, maybe. Suppose you have a source capable of producing more than a couple volts, then nope. You’ll likely destroy it.

If you’re starting to get the impression that setting the gain correctly in a car audio system with multiple amplifiers isn’t as simple as you first thought, then this article has served its purpose. It’s a complicated process that requires the technician working on your vehicle to consider many factors. More importantly, if you’ve damaged a set of speakers by overheating the voice coils, you’ve overpowered them. Too much power produces too much heat. That’s it. Period. There’s no other reason this happens. It doesn’t matter how your amp was set. You melted them.

If you’re having problems with your car audio system, look for a qualified specialty mobile enhancement retailer in your area to help configure your system properly or help you choose a combination of components that will work together to deliver the performance you want.

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 designing and integrating high-performance speakers into your car or truck, your local specialty car audio retailer might suggest choosing an amplifier or signal processor that includes a bandpass crossover. If you aren’t used to designing speaker systems, a task that most consumers don’t concern themselves with, then the term bandpass might be confusing. Please don’t fret; we’ll explain what it means and why it’s necessary to extract the best performance possible from your speaker upgrades.

What Are Crossovers?

The theory of a perfect speaker that produces the entire audio range, from a single driver, at an adequate output level with no directivity, is so far from reality that the concept alone makes a speaker engineer’s eye twitch. As such, we need to use speakers of different sizes to cover the audio spectrum. In the simplest of systems, we need a woofer to produce bass and midrange frequencies and a tweeter to produce high frequencies. Since most tweeters are rarely capable of reproducing information below 2 kHz with significant output, we need to block that information. We use what’s known as a high-pass crossover to pass only high-frequency information. Looked at another way, a high-pass filter blocks low-frequency information from going to your speaker.

Once we have routed high-frequency information to our tweeter, we don’t need the woofer to reproduce those sounds. So, the technician configuring our audio system will apply a low-pass filter to the woofer at the same frequency. This filter passes low-frequency audio information below our crossover point to the woofer.

What Is an Electronic Bandpass Filter?

If we decide that we want to further upgrade the audio system with a subwoofer, we’ll need more filtering. Subwoofers are great at reproducing audio frequencies below about 80 Hz. Most don’t do a good job with midbass and midrange information. As such, we want to block frequencies above about 80 Hz from going to the sub. We’ll use an 80 Hz low-pass filter to accomplish this task.

Now that we have a speaker dedicated to reproducing bass, we don’t need our woofer to play those frequencies. We can apply a high-pass filter to the woofer to block audio information below 80 Hz.

The graph you see above is called a bandpass filter. It passes audio within a specific band of frequencies. In this example, our bandpass filter passes audio information between 80 Hz and 3 kHz.

Some car audio systems add a fourth set of speakers in the form of a small midrange driver. In most cases, these speakers are mounted higher in the doors or the dash and focus on information from about 300 Hz up to where the crossover takes over. In a four-way audio system design, we can now move the low-pass crossover on our woofer to 300 Hz and run the mid from 300 Hz to 3 kHz.

Proper Crossover Configuration Is Crucial

There is a lot more to setting crossovers than just picking some arbitrary frequencies that look good on a graph. The values depend on the speaker’s low-frequency capability and its directivity characteristics. The installer calibrating your audio system also needs to consider the physical power-handling limitations of speakers and how loudly the system will be played. Quite simply, it’s not an easy task, and the process is exacerbated by component systems that don’t include drivers with adequate bandwidth to work well together.

If you want the music reproduced by your car audio system to sound amazing, drop by your local specialty mobile enhancement retailer and ask them what’s available for your vehicle. Be sure to audition one of their demo vehicles to ensure that they can deliver the performance you want. It’s not unlikely that they’ll suggest an amplifier or signal processor that includes bandpass filtering to make everything sound great.
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.