When looking at the options for frequency response correction for audio systems, your installer has two choices: graphic or parametric equalizers. Both types of equalizers perform the same task in helping to smooth the peaks and dips in what you hear from your audio system. However, the two equalizer types deliver the same results in very different ways. Let’s take a deep look into parametric equalizers and explain how they work.

What Is a Car Audio Equalizer?

As we covered in a previous article, an equalizer is a device that allows your installer to focus on a specific frequency range and either increase or decrease the level relative to the rest of the music. Equalizers must be used with a real-time audio analyzer to correct for anomalies in the frequency response of an audio system. Everything from your smartphone and smart speaker on your bedside table to movie theaters and concert venues uses equalizers to improve an audio system’s frequency response.

What Is a Graphic Equalizer?

Before diving into the operation of a parametric equalizer, we should review how a graphic equalizer works. The number of bands included in a graphic equalizer indicates their suitability and capabilities. Each of these adjustments is called a band. Each band is assigned a specific frequency in a graphic equalizer (or EQ for short), and the number of bands defines the range of frequencies each covers. For example, if you have a 31-band graphic equalizer, each band will cover about 1/3 of an octave. Conversely, each band covers an entire octave if you have a 10-band graphic equalizer.

The technician can boost or cut these bands based on acoustic measurements made with a calibrated real-time audio analyzer. For example, if there is a 4-dB dip in frequency response at 1 kHz, the technician can boost the 1-kHz EQ band by 4 kHz. Graphic equalizers are very common in higher-end aftermarket car radios.

What Is a Parametric Equalizer?

Though the purpose is the same, parametric equalizers can be more flexible than their graphic cousins. In a parametric equalizer, your technician can select a specific center frequency and bandwidth for each equalizer band. For example, suppose a peak in a system’s frequency response is at 1.1 kHz. In that case, the technician can specify 1.1 kHz as the center frequency of the EQ and then apply whatever amount of attenuation is required to flatten that peak.

A parametric equalizer has a bandwidth adjustment labeled as Q. The concept of Q, or more specifically, Q-factor, is initially unintuitive. The Q-factor represents the ratio of the center frequency to the bandwidth the adjustment covers. A high-Q filter is very narrow, and the low-Q filter affects a broader band of frequencies.

How Is the Q-Factor Calculated?

The calculation to determine the Q-factor of an equalizer adjustment is relatively simple. That said, it’s not arithmetic we typically need to perform when calibrating an audio system. If you look at the image below, you can see the center frequency of the adjustment represented by the uppercase letter F. This would be something like 1.1 kHz, as mentioned in the previous paragraph. The following required information is the -3 dB bandwidth of the range over which the filter adjusts. Let’s use the example of the low-side to high-side -3 dB frequencies being 3,300 hertz apart. The lowercase letter f defines this bandwidth. To calculate the Q-factor, you would divide F by f, 1,100 ÷ 3,300, which equals 0.33. As you can imagine, it would take some measurement to determine the bandwidth of the -3 dB frequencies, so we never do the math to make adjustments.

A higher Q filter might be required if the technician needs to address a very narrow spike or dip. Let’s say that only 1,100 hertz of bandwidth requires boosting or attenuating. Our equation now becomes 1,100 ÷ 1,100 for a value of 1.

Common Q-Factor Knowledge

There are a few pretty common Q-factor values. If the technician wants a parametric equalizer to act like a 1/3-octave graphic equalizer, then a Q-factor of 4.318 will work. If you don’t have many equalizer bands, common in several car audio signal processors, and they want each band to cover an entire octave, then a Q-factor of 1.414 is ideal. These are often the default settings in many systems, though they are rarely suitable for any particular system.

The two images above show how a higher Q-factor affects a narrower range of frequencies. The image below is the ARC DNA software used with the Blackbird amplifier. It allows for Q-factors as low as 0.1 up to 20. The image below shows four equalizer bands, each set to add 10 dB of signal boost at a center frequency of 500 hertz. The white trace has a Q-factor of 10. The gray trace has a Q-factor of two. The green trace has a Q-factor of 0.5. Finally, the yellow trace has a Q-factor of 0.1. It’s unlikely you’d need the widest bandwidth adjustments, but they can come in handy on some processors that don’t have shelving filters.

Benefits and Drawbacks of Parametric Equalizers

The most significant benefit of a parametric equalizer is that it can zero in on specific frequency response issues quite easily. As mentioned, if a peak or valley is at 900 hertz or 1,100 hertz, then a parametric EQ is a better tool than a graphic EQ band. Many technicians and amateur enthusiasts get hung up on over-equalizing audio systems. Understanding how to interpret measurements from an RTA is crucial to making an audio system sound accurate.

A drawback of many parametric equalizers is that they are often limited in the number of adjustment bands they offer. Some processors have eight, 10 or 15 bands of parametric equalization. This is typically adequate to adjust a single speaker in a fully active three-way system, but fewer than 10 bands might be somewhat limited when used in a two-way application. We’ve seen several digital signal processors with more than 30 bands of equalization with parametric modes. In short, those will have enough adjustability for any system configuration and likely enough to get an amateur into lots of trouble.

What Is a Paragraphic Equalizer?

Just when you think you have a handle on graphic and parametric equalizers, we’ll throw in a third option: the paragraphic equalizer. As you can imagine, this is a hybrid of the graphic and parametric types. A paragraphic equalizer typically allows you to adjust the center frequency of each equalization band but not the Q-factor. These aren’t very common in car audio applications.

Is A Parametric Equalizer Necessary?

The type of equalizer used to calibrate an audio system is much less important than the accuracy and relevance of the system’s frequency response measurement. A technician’s experience in understanding what the RTA shows. It’s not uncommon for someone to adjust a system to deliver what looks like a smooth response on the computer screen, only to have it sound like it still needs work in certain frequencies. Parametric equalizers are powerful tools and can be an ideal solution to calibrate any audio system, but as with any tool, the craftsman’s skill matters the most.

When it’s time to take your car audio system to the next level, drop by a local specialty mobile enhancement retailer and ask about adding a digital signal processor to your car audio system with an adequately powerful graphic or parametric equalizer. Make sure they have extensive experience in proper audio system design and calibration, which is the key to reproducing music with realism 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.

The single most crucial upgrade a person can make to their car audio system is to incorporate a properly configured equalizer. Whether you have a radio and two speakers or a high-end four-way system with active crossovers, ensuring that the system’s frequency response is accurate remains the most important consideration concerning quality. Let’s examine how a car audio equalizer works and why they’re crucial.

What Is an Equalizer?

There are several ways to describe an equalizer. We’ll offer several definitions, as all do an excellent job of explaining their functionality. You can consider an equalizer to be a frequency-specific volume control. Unlike the main volume control, your installer would set this once rather than have it used frequently. Another description is that an equalizer is an audio filter that boosts or attenuates specific frequencies. Ultimately, an equalizer tool allows for the amplitude adjustment of particular frequencies in an audio signal.

In the image above, we see the response curve of an equalizer in a digital signal processor that has added 6 dB of boost at 1 kHz. Any audio signal that passes through this equalizer channel will have the frequencies at and around 1 kHz boosted by this amount.

This second image shows the equalizer set to cut or attenuate frequencies around 1 kHz by 6 dB.

An equalizer can cut or boost the amplitude of different frequencies by specific amounts. While seemingly simple, it’s a powerful and essential tool in creating great-sounding car audio systems.

Why Is a Car Audio Equalizer Important?

Imagine the perfect speaker. Let’s say it’s a 6.5-inch driver that delivers ruler-flat response from 80 hertz to 20 kHz. Magically, it has ideal directivity at most frequencies, producing even amounts of sound in every direction. It has distortion-reducing features like an aluminum shorting ring and copper T-yoke cap. It has a flat-wound voice coil for maximum efficiency. It also has a rigid cone that doesn’t resonate uncontrollably. The suspension design allows the speaker to move linearly through a wide excursion range, so it continues to sound good, even at higher volume levels. The engineers who designed this speaker would have spent significant time measuring its performance in an anechoic chamber to ensure accuracy.

Now, what happens when we put that speaker in the door of a car? It still functions the same, producing audio frequencies at the same amplitude with magically perfect dispersion. Would it sound great? Probably not. Why? Because the listening environment dramatically affects what we hear. This change in frequency response isn’t the speaker’s fault. Notably, a speaker should never be designed for a specific listening environment. Speakers should be as accurate and faithful to the source signal as possible.

Why does the environment affect what we hear? The answer is reflections and resonances. When we listen to a speaker in a car or truck, we hear the sound directly from that speaker. We also hear sounds that arrive a moment later that have bounced off the roof, windshield, side window, seats, floor, dash and center console. These reflections change our perception of the system’s sound reproduction. Depending on the distance from the speaker to the reflecting surface and from the surface to the listening position, the reflections might add emphasis at specific frequencies or reduce the amplitude at others.

Another issue is resonance. Because of the distances between certain surfaces, we can get additional peaks in the system response. For example, a distance of 5 feet between the left and right windows might cause a peak in the system response at 225 hertz and a smaller one at 450 hertz. If the distance from the roof to the floor is 3.5 feet, that might cause a resonance at 321 hertz. The materials on the surfaces affect how much resonance occurs. If your vehicle has a deep plush carpet and cloth roof, the resonance might not be as significant as if it had a vinyl floor and roof. The listening environment wreaks havoc with what we hear from our perfect speaker. The result is peaks and dips in the frequency response, and the system doesn’t sound natural.

How an Equalizer Improves Audio System Performance

Before we can adjust an equalizer, a technician must accurately measure what might need fixing. We use a real-time audio analyzer to make these measurements. A real-time analyzer is essentially a calibrated microphone and display that shows the frequency response of the measurement. Most car audio technicians use computer-based audio analyzers with a single microphone or a multi-microphone array.

Audio analyzers need to be very accurate. If they show a dip at a specific frequency, we should be able to apply a measurable amount of boost to that frequency with an equalizer to produce a flat response curve. This requirement means the microphone must be calibrated accurately. A microphone used for music recording or voice communication likely isn’t ideal for audio measurements as it will impose its frequency response variations.

In the case of all audio analyzers, knowing how to interpret the data they offer is crucial to making audio system adjustments. Understanding measurements and knowing what to adjust in an equalizer takes extensive training to deliver great-sounding audio systems. With that said, the basic concept is that the RTA graph will show peaks and valleys in the acoustic response of an audio system. The technician can then cut (attenuate) peaks or boost dips to deliver a system with a smooth response.

Types of Car Audio Equalizers

There are two ways to discuss types of car audio equalizers. We can look at the different physical solutions or how the equalizers adjust signals. We will discuss the available solutions in this article and save the operational differences for another time.

The simplest of equalizers would be the bass and treble controls in a car radio. Turning either up or down affects a relatively wide range of frequencies, and these are better suited to changing the overall tonal balance of a car audio system than correcting response issues. Many late-model vehicles include bass, midrange and treble control adjustments in their infotainment systems.

Regarding system frequency response correction and calibration, you need fine control over different frequency ranges. For the context of this article, this will mean you need a lot of bands of equalization. A band is a single EQ adjustment that can boost or cut a narrow range of frequencies. Companies like AudioControl, Phoenix Gold and PPI had analog 30- or 31-band equalizers that were popular with autosound competitors years ago.

These days, digital signal processing has made equalization easy. From source units like the Sony XAV-9000ES and XAV-9500ES to stand-alone processors from companies like Audison, Rockford Fosgate and ARC Audio, access to the tools required to calibrate modern car audio systems is easy.

These processors use software on a computer or iPhone/iPad to allow the technician to calibrate your audio system to adjust the equalizer bands on each output channel. As mentioned, we aren’t going to get into the details of the types of equalizer modes (graphic or parametric) in this article.

How Do I Know My Car Audio System Needs Equalization?

While all this information is essential, knowing whether your car audio system requires equalization is equally important. Unless it’s a factory-installed system in a relatively new model vehicle, the answer is yes, it needs equalization. Why don’t those systems need equalization? The answer is simple – they’re already set up for the speakers that came with the vehicle. Even modest, unbranded systems often include equalization in the radio that helps to deliver smooth frequency response.

If you’ve ever heard someone say they upgraded their radio or speakers to an aftermarket unit, but the system doesn’t sound as good, this is why. The equalization would be removed if it were built into the factory-installed radio. It might still exist if the new radio were feeding a factory-installed amp. At the other end of the spectrum, new speakers likely have different frequency response curves than what came from the factory. Changing speakers essentially invalidates the equalization.

If you’re building a new system from scratch with a premium radio and great amplifiers, speakers and subwoofers, part of the system design should include a way to equalize the system. You could opt for a radio like the aforementioned Sony units with an equalizer on each channel. You could also use a stand-alone digital signal processor between the source unit and the amplifiers. Another option is to choose amplifiers that have built-in digital signal processing.

If you’re serious about optimizing your audio system, you’ll need an equalizer for each speaker. The corrections required for a woofer in the front door will differ significantly from that of a speaker in the rear door or on the parcel shelf. More importantly, the equalization will be very different on the left side of the vehicle compared to the right. Having a single EQ for the entire vehicle is better than nothing, but if you want rock-solid imaging and fantastic realism, you need equalization for each channel.

You need someone with experience to set up the EQ. As we mentioned earlier, knowing how to interpret the measurements from the RTA is crucial. Adding equalization that won’t positively affect the system’s performance is easy. There might be a peak or dip on the response graph of the RTA, but it might be something that can’t or shouldn’t be fixed with an EQ. Having a thorough understanding of the laws of physics and extensive experience are crucial to creating a system that sounds genuinely lifelike.

Upgrade Your Audio with a Car Audio Equalizer Today!

If you want to elevate the performance of your stereo system, then you need a properly calibrated car audio equalizer. Start by visiting some local specialty mobile enhancement retailers in your area. Audition their demo vehicles or work they’ve done for other clients. If those systems sound good, they can likely deliver similar results in your vehicles. Don’t be afraid to shop around. You may have to travel to another city to find a shop that can deliver what 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.

Here are three sentences that make car audio experts cringe: “I set the gains halfway” is definitely at the top of the list. “Can I use a 60-watt amp with my 80-watt speakers?” demonstrates a complete misunderstanding of the irrelevance of power ratings. Something like “I tried the remote bass control from my Sony amp in my Rockford Fosgate amp” couldn’t be scarier. Can you imagine the potential for damage? Oh, maybe you can’t. OK, let’s talk about car audio amplifier remote level control compatibility.

What Is a Car Audio Amp Remote Level Control?

Many modern amplifiers, particularly monoblock subwoofer or multi-channel amplifiers with a dedicated high-power subwoofer channel, have an option for or include a remote level control. A level control or bass control is typically a tiny metal box or plastic enclosure with a knob on the front. Your installer can mount the control in the dash or center console so it’s easily accessible. Depending on the amplifier design, the level control might adjust the output of the amplifier, or it may alter a bass boost circuit. Some are fancy and include multiple knobs and a button. Some even include voltage displays and clipping indicators. Ultimately, these controls provide an easy way to adjust the bass level for different music or listening preferences.

The simplest of these controls use a potentiometer. Turning the knob on the potentiometer changes the resistance. In most amplifiers, the remote level control attenuates the signal from the source unit by creating a voltage divider. If you turn the knob up, you get all the signal from the amp. If you turn it down, you get either no signal or a specific percentage of the signal. How the level control works depends on the associated circuitry in the amplifier.

Most potentiometers have three terminals. The outer terminals connect to either end of a resistive element or path. The middle terminal connects to a wiper arm that’s connected to the adjustment knob. When you turn the knob, it moves the arm along the path. The resistance between one end terminal and the wiper connection changes as you turn it. If it’s turned close to one terminal, the resistance will be minimal. The resistance will be large if it’s turned far from one terminal. Potentiometers are sold based on the total resistance of the path or element.

Car audio amplifiers often use multi-ganged potentiometers for circuits like crossovers or level controls. These are multiple potentiometers connected to the same shaft. For example, if a stereo amplifier has a single sensitivity or gain control, separate potentiometers for the left and right channels would be needed. These potentiometers are mounted on a single shaft for convenience.

In applications where the remote control adjusts a bass boost, the minimum setting on the control usually applies no boost. Turning the control to its maximum applies 12 or even 18 dB of boost around a specific frequency. Once again, the amount of boost and center frequency depend on the amplifier’s design.

Level Controls for Digital Signal Processors

There’s a second type of level control dedicated to digital signal processors. Some companies have simple potentiometer-based controls that adjust an analog signal that feeds back to the microprocessor in a digital signal processor. The processor interprets the signal’s amplitude and then applies that to something in the processing path. The DSP software might allow the installer to configure the remote level control as a bass boost control, a subwoofer level control, a master volume control or even a center-channel level control. In these cases, the control itself is still a simple potentiometer. It’s the software in the processor that adds the flexibility.

Many processors also have compatible computerized level controls. Rather than analog signals or voltages, there’s digital communication between the remote and the computer processor in the DSP. These typically use communications with data lines, power, ground and possibly illumination connections.

Remote Level Control Connections and Wiring

Here’s where things get scary for those who understand basic electronic circuit design. Let’s start by discussing the different connections on modern amplifiers for remote bass or level controls. Typically, you’ll see an RJ45, RJ12 or RJ11 jack, or maybe a 3.5-mm or ¼-inch headphone-style jack.

Simple Level Controls

The level control might require no more than two electrical connections if it’s a simple design. One wire would go to the potentiometer wiper and the other to a terminal at the end of the path or element. As the wiper turns, the resistance between the connections increases or decreases, increasing or decreasing the signal amplitude sent back to the amp.

Here’s the first opportunity for a remote level control from one amplifier to be incompatible with the circuitry from another amp. Let’s say you have a Rockford Fosgate remote, and its potentiometer has a 1,000-ohm rating. For some reason, you want to use it with a Sony amplifier. The Sony remote might use a 10,000-ohm potentiometer. It might work, but the effective adjustment range might be wrong. Worse, there could be a change in the circuitry function, which might boost the signal. This increase in amplitude could overdrive portions of the circuitry and cause massive amounts of distortion.

Wire Connections

The second instance where something might go wrong is that the remote level control and amplifier use a connector with more than two pins. It might have three, four, six or eight. Even if it only uses two connections, the pins must be in the proper position on the connector. The two connections could be backward and still work, but they must match the traces on the amplifier circuit board. In this case, you would likely get no output from the amplifier. If all three wires connect to the potentiometer, you may get all the signal or none of it.

What about a fancier remote that includes something like an LED that illuminates when the amplifier turns on? That LED will need power from the amplifier. It might be a low voltage in the 2.5-to-3-volt range or as high as 12 volts with circuitry on the circuit board in the remote. What if the pinout from a remote didn’t match that of another amplifier, and you feed 12 volts DC into an audio signal path? You could easily damage the amplifier. If the LED is expecting a low voltage, and you send it something substantial, you’ll burn it out instantly.

Completely Incompatible Remote Technologies

Below, you’ll see an image of the JL Audio DRC-205. This remote is designed for their FiX integration processors, TwK calibration processors or VXi-Series DSP-equipped amplifiers. It’s easily one of the best-looking remotes on the market. The remote includes two rotary controls, a multi-color LED and a pushbutton. The color of the LED can indicate which processor preset is loaded or what mode the device is in. The button can change the presets on a DSP. The rotary controls can serve as master volume control and subwoofer level control. Best of all, it’s easy to take the knobs off the remote and mount it neatly on the dash or in the center console of a vehicle. It can be upgraded with the optional VXi-BTC Bluetooth communicator to function wirelessly.

The DRC-205 uses a standard eight-position RJ-45 connector and CAT-5e network cables to connect to supported processors. Can you imagine the havoc that would ensue if you connected a conventional analog remote to the JLid port on a VXi amp or a DRC-205 to the remote level control port on a different brand of amplifier? The results would be instantly catastrophic.

Don’t Experiment with Car Audio Amplifier Remote Level Controls

We’ll wrap this up with an unambiguous statement: Never connect the remote level control from one amplifier brand to another. In addition, unless you’re sure of the compatibility, there may be issues with the compatibility of level controls from one series of amplifiers to another within the same brand. If you’ve lost the level control that came with an amp or need to purchase an optional one, get the specific unit designed for the amplifier you have. Don’t risk guessing. Drop by a local authorized retailer for the brand of amplifier you need the remote for. They can help you get the current part to ensure that everything functions properly.

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.