If you are thinking about having your local mobile enhancement retailer add a subwoofer amplifier to your car or truck, you may want to ask them about the remote level or bass boost control options that are available. Being able to adjust the amount of bass your system produces from the driver’s seat allows you to fine-tune the system for the music you are listening to or your mood. Let’s look at five of the most popular options available to adjust the output of a new subwoofer system.

Dedicated Remote Level Control

Many subwoofer amplifiers have a built-in jack that your installer can connect to an included (or optional) remote level control. In most cases, these are RJ11 jacks, similar to what home phones use. The remote includes a long cable that can be run to a location on the dash or center console where the knob or control panel can be installed.

How the remote works is important to the overall reliability of your sound system. To prevent distortion from clipping, the remote should ideally only serve as an attenuator. Your installer will configure the system to produce maximum power from the amp with the level control turned up all the way, then you can turn it down to suit your listening preferences.

Digital Signal Processor Remote Controls

Almost all DSP manufacturers offer some sort of remote control that is compatible with their processors. These remotes can serve as master volume controls or subwoofer level controls and can usually select different presets if the processor supports that function. Whether the processor is a stand-alone system or integrated into an amp, adding a remote is a great choice.

Some processors have provisions to add a remote control that can be assigned to specific channels and operate over a specific range. This remote can be configured to act as a level control for a subwoofer, a center-channel speaker or rear speakers, depending on how the system is configured. This style of remote can also serve as a master volume control for the amplifier in instances where you are not using a radio with a volume knob as a source. This single knob is often easier to use and much less expensive than a full controller.

Remote Bass Boost Controls

Some inexpensive amplifiers come with a remote bass boost control. These controls work in the same way as the adjustment potentiometer on the side of an amp to apply a narrow EQ band of signal boost to the audio signal.

There are two problems with bass boost controls. First, they increase the output of the amp, so your system needs to be tuned with the control at its maximum setting. This configuration makes it difficult to blend the sound of the subwoofer with the mid-bass speakers. Secondly, using large amounts of boost often sounds unnatural. Boosting the region around 45 or 50 Hz is a lot of fun, but the audio information down at 25 and 30 Hz and up at 70 to 80 Hz is just as important. Ideally, a remote level control is a much better choice than a bass boost control.

Source Unit Subwoofer Level Controls

If you have upgraded your sound system with a new radio or multimedia receiver, most include a subwoofer output level adjustment in the audio configuration menu. It’s worth noting that these radios typically don’t produce their maximum output signal on the subwoofer preamp connections unless the subwoofer level control is at its highest setting.

Many years ago, a radio manufacturer placed a rocker switch on the front panel of one of their radios that provided direct access to the subwoofer output level. This was a truly genius idea! These days, you have to press a few buttons or navigate a menu option or two to access the adjustment menu.

Integration Processor Level Controls

Many audio integration processors and converters (often called Line Output Converters or Line Level Converters) have an option for an external remote level control. Depending on the design of these processors, the output controlled by the knob could be paralleled off of a single stereo input, or be from a second dedicated input. If your audio system needs a processor to take the signal from the factory radio or amplifier and turn it into something the amp can use, look for something with a remote level control.

Upgrade Your Car Audio System Today!

Upgrading an existing subwoofer or adding one to your factory car stereo is the most dramatic improvement you can make to your mobile audio system. Alleviating the need for the small speakers in your doors, dash or rear parcel shelf to try to produce bass makes them sound better, play louder and last longer. Drop by your local specialist mobile enhancement retailer today to find out how you can add a subwoofer enclosure and amplifier with remote level control to your car stereo system.

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.

We are at our second-to-last article in our car audio amplifier specification series and this time, we are going to talk about Class AB amplifier crossover distortion. This distortion has nothing to do with the high- or low-pass filters built into your amplifier; it’s a problem with the very concept of the Class B amplifier topology. Don’t fret — we’ll explain what causes it and how it’s minimized to a level of near inaudibility.

How Do Class AB Amplifiers Work?

Before we can explain what crossover distortion is, you’ll need a basic understanding of how the output of a Class AB amplifier works. In a Class A amplifier, a single transistor (or bank of transistors) takes care of controlling the voltage going to the speaker. When no signal is being produced, the transistor is set at a 50% output level (and gets VERY hot). As the alternating current (AC) from the signal source passes through the amp, the output voltage goes up and down until it reaches the maximum or minimum possible level associated with the transistor being off or at its maximum output level.

In a Class B amplifier, we use one transistor to handle the positive half of the waveform and a second transistor to handle the negative half. The primary advantage is that when there is no signal present, both devices are almost completely turned off and very little power is consumed.

The Class B topology is where our crossover distortion problem arises. As the audio signal swings from positive to negative, it needs to switch from one device to the other without any issues. It’s at this point where the signal crosses over from one device to the other that problems can happen — hence the name, crossover distortion.

Amplifier designers who truly care about the sonic qualities of their products know how to handle this transition and can effectively eliminate crossover distortion by biasing the positive and negative output devices into their active regions. While this does create a little more heat, it reduces distortion dramatically. This is where the Class A part of an AB amplifier comes from: The devices are turned on a little bit (like a Class A amp), but for high-level signals, act in a Class B configuration.

 

Why Does Crossover Distortion Matter?

At low output levels, even in moderate-quality Class AB amplifiers, crossover distortion is more prevalent than when an amplifier is producing very low amounts of power. More accurately, the effect of crossover distortion decreases as the output level increases.

Let’s look at the distortion characteristics of three different amplifier topologies to gain a better understanding of that statement. Up first is our truly outrageous low-quality four-channel amplifier. This workhorse of mediocrity has served us well through this series in explaining the kind of harmonic distortion versus its output level.

For a stark and dramatic contrast, we’ll switch to our high-end amplifier. This amplifier is unique in that it uses a high-bias design intended specifically to reduce crossover distortion in the transition between the positive and negative output devices. The graph below shows the distortion of 0.09% versus the output level.

Choosing the Right Amplifier for Your Audio System

If the goals for your audio system are world-class performance, and you intend to use Class AB amplifiers, you can reduce the effects of crossover distortion by matching the power requirements of your speakers with amplifiers that will operate higher in their output range. For example, if you want a 150-watts-per-channel amp for your mid-bass drivers, you may only need a 50-watt amp for your midrange speakers and a 10-watt amp for your tweeters to achieve the same acoustic output level. BestCarAudio.com published an article on speaker power handling that explains why.

While you can’t always choose high-quality amplifiers with extremely low power levels, you can minimize the effect of crossover distortion by not using a monster amp on your tweeters. Your local specialist mobile enhancement retailer would be happy to design and install an amazing car audio system upgrade — drop by and talk to one of their Product Specialists today!

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.

It’s time to look at the input stage of how a modern car audio amplifier works. The input stage is responsible for interfacing with your radio and provides features like the gain control, crossovers, bass boost, remote level control and signal summing that your installer will use to make your stereo system sound great and function reliably. While we don’t need to get into the specifics of the components in this part of your amp, understanding the importance of the features is crucial in picking the right solution for your applications.

RCA Preamp and Speaker Level Inputs

Your amplifier can’t amplify an audio signal if you can’t connect the amp to your radio. Almost every amplifier on the market has RCA input jacks that allow your installer to connect an aftermarket radio quickly and easily. We say “almost” because some amplifiers are designed exclusively for integration with factory-installed audio systems. These amps may have a set of wires on a pigtail harness to accept signals.

In most cases, speaker-level signals are no different than a preamp signal other than they are usually higher in voltage and, because they have already passed through an amplifier stage (in the factory-installed radio or amp), may contain a little more distortion.

Whether the amp uses preamp or speaker-level signals, it should have a feature called Balanced Differential Inputs, or a variation of those words. This simple circuit compares the signal (or noise) on the center conductor and the shield of an RCA interconnect and uses an Op-Amp (a small integrated circuit that can be configured to compare or combine two signals into a single output) to remove anything common to both conductors. If you are using twisted-pair interconnects, EMI or RFI noise should be common to both conductors and thus will be reduced or eliminated by this circuit. When shopping for an amp, Balanced Differential Inputs are one of the first things you should ask the salesperson about.

Signal Processing Features

The next important feature in any amplifier is the sensitivity or gain control. This adjustment allows your installer to configure the amp to produce maximum power for a specific voltage that matches the maximum undistorted output of your source unit, or your power requirements based on the design of your audio system. The gain control is something that should be set once using an oscilloscope and a real-time analyzer (RTA), then not touched again unless the design of the system changes.

Most modern amplifiers include some form of electronic crossover that limits the range of frequencies that pass from the inputs to the outputs. A high-pass crossover only allows frequencies higher than the crossover point to pass and would be used on midrange and high-frequency speakers. A low-pass crossover allows audio signals lower in frequency than the crossover point to pass through the amp. This type of crossover would be used for woofers and subwoofers. Depending on the design of your audio system and the features of your amplifier, your installer may choose to combine high- and low-pass crossovers to create what is known as a band-pass crossover. This crossover would be used on midrange or midbass drivers to cut out low- and high-frequency information.

Many amplifiers have a bass boost control. This control operates as a single-band equalizer that the technician installing your sound system can use to reinforce a narrow band of frequencies being sent to a subwoofer. In reality, adding a narrow-bandwidth boost to your audio signal, from a purist perspective, makes no sense. Most systems sound better with proper DSP equalization to deliver smooth and predictable response across the entire operating range from 20 Hz to the upper limit of your sub around 60 or 70 Hz. A peak at any particular point will sound unnatural.

Remote Level Controls

Most high-quality subwoofer amplifiers come with a remote level control or remote bass boost control that can be installed in the front of the vehicle. This control allows the driver to turn the bass up or down to suit the music he is listening to or his mood. When shopping for an amp, look for units that offer a level control as opposed to a bass boost. As we mentioned above, adding emphasis to a narrow band of frequencies doesn’t sound as natural as turning as adjusting the overall output of the subwoofer.

Amplifiers with Integrated DSP

A friend of ours was in charge of developing a series of high-end amplifiers for one of the well-known head-unit manufacturers. The goal was to include as much flexibility as possible in terms of crossovers and signal summing. The complexity of the amp grew to a point where it was becoming difficult to fit all the switches and adjustments on the side of the amp. To provide their clients with the features they wanted, the company decided to remove all the controls and implement a digital signal processor (DSP) to handle everything. Now, the installer could combine signals from multiple sources, set crossovers very accurately and equalize the signal to deliver a smooth and predictable response from the speakers. Sure, your technician will need to connect a computer to the amp, but the results will be fantastic!

Great Features and Great Design

As important as the features of the amplifier you choose are, the design and component layout of the input stage of a car audio amplifier can have a huge effect on the performance of the amp. Keeping these components away from noisy sections of the amp like the power supply and output stage can dramatically reduce the signal-to-noise ratio of the amp. For this reason, larger amplifiers often sound and perform better than their compact counterparts. As with any design, the electronics engineers and technicians who develop the circuits and lay out the components have to balance performance, features, cost and size.

Find the Latest Car Audio Amplifiers at Your Local Car Stereo Shop

When it’s time to shop for a new amplifier for your car, truck, motorcycle or boat, make some notes about why you need an amp and what you want it to do. Armed with that information, the product specialists at your local stereo shop can help you find a solution that will meet your requirements quickly and efficiently and ensure that your mobile audio system sounds magnificent.

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.