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.

We aren’t sure where or when things went wrong with the basshead crowd, but there’s a serious misunderstanding about how to build a loud stereo system. We’ve lost track of how many of these vehicles we’ve heard that sound utterly atrocious. No, we aren’t talking about the fact there’s 30 or 40 dB too much bass. That’s fine, given the goals. The issue is how horrific the midbass and midrange frequencies sound. The same mistakes seem to repeat in every system. Let’s look at what it takes to make a loud car stereo system that actually sounds good.

Loud Bass Is Easy

Let’s start by addressing bass frequencies in loud car stereo systems. This part of the system design is easy, as many companies offer subwoofers designed with impressive power handling and excursion capabilities. If you want to be loud, your subwoofers must move a lot of air. This means the cones in the woofers need to move back and forth a significant amount. Good quality subwoofers with excursion capabilities of 2 to 3 inches of linear excursion are readily available. Likewise, amplifiers capable of producing more than 2,500 watts of power can push these drivers effortlessly. Combine this with a well-designed, sturdy enclosure and making massive amounts of bass is a snap.

Making Midrange and High Frequencies Sound Good

Here’s where things go sideways when designing a loud car stereo system. Hundreds, if not thousands, of car stereo systems are built with high-efficiency speakers in the doors. We don’t and never will understand this speaker selection choice. High-efficiency speakers get their efficiency by reducing the mass of the cone assembly. This low-mass cone design raises the speaker’s resonant frequency and allows it to play louder with the same power as a driver with a heavier assembly. This reduction in cone assembly mass also dramatically reduces the midbass these speakers produce. It’s common for a high-efficiency midrange speaker to be efficient only from 200 hertz and up.

The graph above shows a high-efficiency speaker’s second and third harmonic distortion (in red and blue, respectively) when driven with just under 4 watts of power. The output at 200 hertz includes 1.5% harmonic distortion. That’s pretty bad at a power level this low. You can also see that the driver’s output starts to roll off around 175 hertz.

As this graph above clearly demonstrates, distortion increases with excursion. If you look at the amplitude of the red and blue traces, they get higher as frequency decreases. This increase in distortion directly correlates to cone excursion requirements to produce audio at lower frequencies. Using high-efficiency speakers below about 300 hertz, even with modest power, is a recipe for a stereo system that will sound terrible.

Further, there’s really no need for the added efficiency. Amplifier power is inexpensive these days. You can purchase a four-channel amplifier that produces a good, clean 75 watts of power per channel for under $300. This is enough power to push all but the most robust midrange speakers to their limits.

Excursion Matters When Reproducing Midbass

Let’s examine the excursion requirements of a 6.5-inch speaker asked to produce midbass information. A three-way system with subwoofers and tweeters requires a speaker like this. In most cases, we’d use a crossover point around 80 hertz, so pay close attention to that frequency in the graphs below.

The red trace in the speaker efficiency comparison graph below is a typical high-efficiency speaker with a sensitivity rating of 92.4 dB at 1W/1M. It has a resonant frequency of 101 hertz and a linear cone excursion rating (Xmax) of 2.6 mm in each direction. The yellow trace represents this woofer. The second woofer is from the Rockford Fosgate T4652-S component set. This driver has a resonant frequency of 49 hertz and a mind-boggling 12.6-millimeter excursion specification. That’s more excursion than some entry-level 10-inch subwoofers. The red trace in the graphs below represents the Rockford Fosgate woofer.

The chart above predicts the output of each woofer when driven with 100 watts of power. Let’s start with the obvious. Up at 500 hertz, the high-efficiency speaker theoretically produces 113.2 dB SPL of output. The Rockford Fosgate woofer is producing 107.4 dB SPL with the same power. So far, you’d think the high-efficiency speaker is the way to go, right? Well, what happens at lower frequencies? We can’t use this graph to answer that, as we need to consider cone excursion limitations. The chart below shows cone excursion versus frequency for the two woofers.

As you can see, the yellow trace turns translucent at frequencies below 440 hertz. This means that at all frequencies below 440 hertz, the driver will exceed its 2.6 mm Xmax specification when driven with 100 watts of power. If you want your car stereo system to sound terrible, pushing a driver beyond its excursion limits is a perfect way to do it. It’s essentially mechanical clipping, adding vast amounts of nasty distortion to the speaker’s output. Ew! By comparison, the Rockford Fosgate woofer has no problem producing audio information well below the 80-hertz crossover point. Let’s look at another factor, maximum acoustic power.

This graph shows the maximum output capabilities of the two woofers based on their excursion capabilities. The yellow high-efficiency woofer can only handle its full-rated 100 watts of power at frequencies above 500 hertz. The Rockford Fosgate woofer, on the other hand, is good down to 66 hertz. Wow, it’s almost like it was designed for a high-output three-way car audio system! Ensure that you add a healthy dose of sarcasm when reading that last sentence.

Less Power Means Less Excursion

We’ve noted that excursion is directly proportional to frequency so far, and this has been the limiting factor in how much midbass information this high-efficiency speaker can produce. Excursion is also proportional to the power sent to the speaker. If we drive the high-efficiency speaker with 50 watts of power, it can play down to 360 hertz without exceeding its Xmax rating. That’s a bit better. So, how much power can it handle if we want it to match the roughly 66 hertz capabilities of the Rockford Fosgate woofer?

That’s right, if you feed the high-efficiency woofer anything less than 0.65 watt, you can use it as a midbass driver. It will produce 85 dB SPL of output at 100 hertz at this level, so it’s not a total waste. Sorry, that was also sarcasm.

Options for Producing Great Midbass in a Loud Car Stereo System

So, what are the options if high-efficiency drivers aren’t the solution for midbass? Your car audio system needs a good woofer, not a high-efficiency midrange driver. We aren’t talking about subwoofers here. We’re referring to drivers designed to play from 60 or 70 hertz up to at least 400 or 500 hertz with good excursion capabilities. Most work up to at least 2 kHz or higher with minimal issues. These are a bit harder to find, but they do exist. The woofer from the Rockford Fosgate T4652-S set is a good example. So is the woofer from the T3652-S set, as it’s pretty similar in design and capability. You will want to look for a 6.5-inch driver with an Xmax specification of at least 8 millimeters. That is, if you want to drive the woofers with their full-rated power handling down to a crossover point of 80-ish hertz. Above 450 to 500 hertz, you can use those high-efficiency drivers as midrange speakers.

A high-performance audio system design aims to choose speakers optimized to operate within a specific frequency range without exceeding any of their specifications. You wouldn’t use a tweeter as a midrange driver. You wouldn’t use a midrange driver as a subwoofer. So why try to use high-efficiency midrange drivers to reproduce midbass frequencies? They sound terrible at all but a loud conversation level. Drop by a local specialty mobile enhancement retailer today to find out what speakers are available to make your loud car stereo system sound good.

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.

Speaker power ratings are among the most confusing and misleading specifications in the car audio industry. Once you understand the process used to test speaker power handling, you’ll quickly realize that the information doesn’t always translate to information that’s helpful in choosing an amplifier. Let’s dive into the science behind choosing the best amplifier for your car audio speakers.

Speaker Power Ratings

In short, how much power a speaker can handle depends primarily on the voice coil’s diameter, length and number of windings. Secondary considerations include the gap size between the voice coil assembly, the T-yoke and the top plate of the speaker. Closer proximity helps to improve heat transfer away from the voice coil. A smaller gap also increases efficiency. However, if the gap is too tight, the voice coil or former might rub, which can cause damage and distortion. Cooling technologies like a vented pole piece, vents under the spider mounting plateau and vents in the former also help by allowing air to flow around the voice coil.

The type of enclosure used also plays a role in power handling. A sealed enclosure will trap heat around the motor assembly. A vented enclosure will allow heat to escape as air is exchanged through the vent resonance.

Audio Content and Power Handling

A concept that many audio enthusiasts don’t fully understand is how power is distributed based on audio frequencies. Looking at frequency response measurements on a real-time audio analyzer can exacerbate this misunderstanding.

When we look at acoustic audio measurements of pink noise on an RTA, we expect to see a flat line. This indicates that the amplitude of each frequency is equal. While we might want to bump up the bass to make the system fun or attenuate the high-frequency content by a few decibels, we don’t want peaks or dips anywhere in the graph.

Where the confusion lies is that the technician working on calibrating your car audio system is using pink noise with the RTA. Pink noise contains random frequencies with the same energy per octave. Put another way, dividing power by the range of frequencies in a given octave will give you the same energy per hertz.

Between 10 and 100 hertz, there are 90 1-hertz frequency bands. We have 900 bands between 100 and 1,000, and 9,000 between 1,000 and 10,000. Let’s say we have 10 watts of power to distribute among those frequencies. In our lowest octave, each one of the hertz bands gets an average of 111.11 milliwatts. In the band between 100 and 1000 hertz, each hertz band receives an average of 11.11 milliwatts. In the top octave between 1,000 and 10,000, each hertz band receives an average of 1.11 milliwatts. Once again, this power distribution produces a flat line on an RTA graph.

The bottom line is that pink noise matches how humans perceive sound. Our ears perceive pink as having the same volume level at all frequencies. Pink noise is occasionally called an equal intensity curve.

What Does Frequency Have To Do with Speaker Power Ratings?

Imagine, if you will, a typical mid-level car audio subwoofer. It might have a 2-inch diameter voice coil former with a winding that’s 1.5 inches tall with a two-layer winding. Rated power handling might be around 400 watts. Now, let’s consider the voice coil in a typical 6×9 speaker. The diameter might be 1 inch, and the winding might be 0.75 inch tall. The speaker might have a continuous power rating of 100 watts. All of this makes sense so far. Less mass in the winding means it can handle less heat.

Now, let’s think about a tweeter. It likely has a voice coil diameter of 1 inch, but the winding might be 0.2 inch tall, and it will surely have no more than one layer. Worse, the wire will be tiny in diameter. Even then, many stand-alone tweeters have a power rating of 100 watts. How can this small voice coil dissipate 100 watts of heat? What about P.A.-style speakers? They often have extremely short voice coils. Yet some claim to have 200-, 300- and even 500-watt power handling ratings. How is this possible?

If the power handling test uses filtered pink noise, then the speaker is tested with less power. A tweeter can’t reproduce bass or midrange frequencies. So, to test their power handling, the noise waveform would be filtered at something like 3,000 or 4,000 hertz. Filtering the bass information removes significant energy from the signal.

If we apply a 2-kHz high-pass filter to a 100-watt equivalent pink noise signal, the result would be only 1 watt of power going to the speaker. Midrange and high-frequency speaker power ratings are almost always quantified this way. So, your 100-watt tweeter can only handle 1 watt of power. Your P.A.-style midrange likely can’t play much below 300 Hz. It might only get 3 or 4 watts of power if appropriately filtered from our 100-watt example.

Matching Amplifiers to Speakers

Now that we’ve set the stage for understanding power ratings, we can finally talk about matching amplifiers to speakers. How powerful of an amplifier do you need for your speakers? The answer starts with the frequency range in which you’ll operate the speakers. With subwoofers, you’ll be playing bass frequencies, so almost all the energy in the music will arrive at the speaker. You’re in the same boat if you have a system with 6.5-inch or 6×9-inch speakers and no subwoofer. You’ll be sending bass information to the speakers. If your system has a subwoofer, you’ll likely only send frequencies at 80 hertz and above to the speakers. That’s about 1/10 of the maximum power compared with a full-range signal. In theory, you only need 1/10 the power to your mids as your subwoofers need. So, 500 watts to a sub and 50 watts to the mids. If you have actively filtered tweeters, they likely only need a few watts.

A lot of this is theoretical rather than practical. So, let’s look at midrange speaker power handling another way. Let’s say you have a set of mid-quality component 6.5-inch speakers. They have a 100-watt power rating, and the woofer might have an Xmax specification of 4 mm. Let’s examine how much the woofer cone moves with 100 watts of power.

The graph above shows us that the driver reaches its 4 mm excursion limit at 110 hertz. If you play music with content lower than 110 hertz, the driver might bottom out or, at the very least, sound terrible. If you want your audio system to sound terrible, driving midrange speakers beyond their excursion capabilities is a great way to do it. With an 80 hertz crossover point, 100 watts is too much power. As it turns out, 50 watts at 80 hertz results in a cone excursion of 4 mm.

What About Time?

If you look at speaker specifications, you’ll see both continuous and peak power ratings. Some companies incorrectly refer to the continuous rating as an RMS rating. Using the term RMS implies that the power measurement was done with an RMS current or voltage measurement, not the waveform’s peak values. RMS refers to the amplitude in an AC waveform that can do the same work as an equivalent DC voltage.

Companies with genuine engineering specifications for their speakers will test them at their continuously rated power level for eight to sometimes over 100 hours. The speaker needs to continue to function after the test, and the Thiele/Small parameters should typically remain within 10% of where they were when the trial started. In other words, the voice coil can’t overheat or fail, and the suspension can’t stretch significantly.

With all that said, speakers can handle momentary bursts of additional power beyond their ratings. The problem is that how long these bursts can last without causing damage is difficult to quantify. Let’s say you’re listening to a song with a vocalist and someone playing a guitar. In the middle, there’s a drum break like Phil Collins’ solo from “In the Air Tonight.” If you cranked up the volume during that solo, even at twice a speaker’s continuous rated power level, that’s not enough energy to overheat the voice coil. So as long as the speaker isn’t physically damaged, everything should be fine.

Picking the Best Amplifier for Your Car Audio Speakers

So, after all this science and confusion, how do you pick the best amplifier for your car audio speakers? You choose the amp that sounds the best. Whether an amp makes 45, 50 or 60 watts doesn’t matter, as that’s only a difference of 0.5 or 0.8 dB in maximum output. Is a 100-watt amplifier “better” than a 50-watt amplifier? It is if it adds less noise and distortion to the signal that passes through it.

Think about how reputable companies group the amplifier series they offer. ARC Audio has the ARC Series. Rockford Fosgate has the Power Series. Kicker has the IQ Series. Audison has the Thesis Series. Hertz has Mille. Sony has the Mobile ES line. Aside from some additional features, these higher-end amplifiers sound better than the lower models. They have better signal-to-noise ratio specifications and lower total harmonic distortion numbers. When playing the same music through the same speakers at the same volume, the sound produced by higher-quality amplifiers is more precise and accurate.

How Much Power Do My Speakers Need?

We can’t count the number of times we’ve seen posts on social media asking, “What amp is best for my speakers?” The poster will then list the speaker’s continuous power-handling capabilities, even if the number is irrelevant. You already know your tweeters will never need more than a few watts, so why would you use a 100-watt amp to drive them? Well, if the amp you have in mind has excellent distortion and noise measurements at those low levels, your tweeters will sound better.

What about everyday systems? How much power does a set of coaxial speakers need? If they are an entry-level speaker, 45 to 65 watts is likely more than enough power to drive them to their limits at lower frequencies. If you have a set of mid-priced component speakers, say in the $200 to $400 range, 75 to 100 watts is adequate. If you’ve purchased high-end speakers like the ARC Audio RS, Audison Thesis, Rockford T3 or T4, Hertz Mille, Kicker QS or Sony Mobile ES, an amplifier that produces 100 to 150 watts is a good power range.

Now, is buying an expensive, high-power amplifier a waste of money when using inexpensive speakers? Maybe. Speakers are almost always the weakest link in any audio system when it comes to how much distortion they add to the audio signal. Look at our articles on Understanding Speaker Quality, and you’ll see what we mean. You are better off buying speakers with distortion-reducing technologies like shorting rings, copper T-yoke caps or even more excursion capability and pairing them with a less exotic amplifier. The net result will be much better sound. If you have a great-sounding amplifier already, use it. Just ensure that the technician configuring and calibrating the system confirms that you can crank the volume without worrying about damaging anything. This doesn’t mean setting gains with a scope or distortion tester.

If you need help picking the best amplifier or speakers to upgrade your car audio system, drop by a local specialty mobile enhancement retailer. Please bring your favorite music and listen to it on their display at the same volume levels you would in your car or truck. This demonstration will give the product specialist an idea of the performance level you need regarding speakers and how powerful the amplifiers should be. Don’t hold back. If you like it loud, crank it. Hoping inadequate products will play louder only leads to disappointment, frustration and damaged equipment.

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.

Understanding how DC voltages combine is quite simple. They add linearly when we wire sources (like batteries) in series. But understanding how AC waveforms combine is complicated. AC waveforms don’t always sum intuitively unless the peaks and valleys align perfectly. We see many examples where people interchange the terms phase and polarity. In reality, those words refer to different phenomena. Let’s take a close look at audio signal phase and polarity.

What Is an Audio Signal?

We will use sinusoidal waveforms as our example audio signals for this discussion. The sounds we hear are combinations of infinite frequencies. If you look at music on an oscilloscope, it would look something like the image below.

Phase refers to the relative timing between two waveforms. A single waveform can’t have phase. We must compare it to something else. As such, we will need a reference waveform for this article. You can see that below.

In Phase

Let’s start with the basics. When we describe two waveforms as “in phase,” we infer that the peaks and valleys are aligned. The starting point of the waveform should happen at the same time. The image below shows two waveforms that are “in phase.”

Two waveforms can be in phase but have amplitude differences. The image below shows that condition.

Reverse Polarity

We often see amplifiers with a switch that inverts the polarity of the audio signal passing through the devices. These are frequently and mistakenly labeled as “Phase.” Let’s explain.

Phase is the relative difference in time between two signals. Polarity refers to a contrasting waveform direction. In DC voltage, we know that if we put a voltmeter’s red lead on the battery’s positive terminal and the black lead on the negative, we’ll see a positive voltage. If we reverse the leads and put the red on the negative and the black on the positive, we’ll see a negative voltage on a digital meter. We call this “having the polarity backward.”

In AC waveforms, the same thing happens. If two waveforms have the same starting point and frequency, but one goes positive while the other goes negative, we refer to one being in the opposite polarity.

Here are our two audio waveforms in the oscilloscope. The yellow waveform shows the opposite polarity to that of the pink waveform.

Let’s consider this in terms of audio signals going to a speaker. The speaker driven by the yellow signal would start from rest and then initially move forward. The speaker driven by the pink signal would begin moving toward the magnet. Activating the polarity switch has the same effect as swapping the positive and negative speaker wire connections.

The image above shows an amplifier with the polarity control switch incorrectly labeled as phase. As a bonus, the amplifier has the infrasonic filter incorrectly marked Subsonic. This labeling is a fairly common error.

If the above amplifier could adjust the phase of the waveform of one signal to be 180 degrees from the other, the waveforms would look like this:

Phase

When discussing phase shifts, we include the peaks and valleys of a waveform and the starting time. This start point or time is especially crucial to discussing audio signals that are never sinusoidal. The starting times move if there is a phase shift between two signals. A difference in starting times implies a delay on one of the waveforms. We can do this quickly and deliberately with a digital signal processor. Adding delay is common in “time aligning” the left and right speakers in a stereo sound system.

Electricians and engineers often discuss phase angles in AC waveforms when driving inductive loads like electric motors. In these cases, the voltage applied to the motor may be “out of phase” with the current flowing through the motor. The same thing happens with speakers and passive crossover networks. These components’ reactive elements (inductance and capacitance) can cause the current and voltage to be “out of phase.” These phase shifts are why we can’t accurately measure the power out of an amplifier without measuring the phase angle between current and voltage. If that was confusing, don’t fret. These are concepts that engineers and technicians learn about in college.

We often talk about degrees when discussing the phase of two waveforms. One complete cycle of a sine wave is 360 degrees. A half-cycle is 180 degrees. The angle between when the sine wave initially moves from the 0-volt level to the first peak is 90 degrees. Here is an example of a 90-degree phase shift between two waveforms:

Here’s what a 360-degree phase shift looks like:

Understanding that the starting points of the two waveforms differ is crucial to understanding how audio waveforms interact. If you were to “align” the peaks and valleys, we’d think these signals were “in phase.” This practice is a common issue for people who try to “time align” a subwoofer to a midbass speaker by reversing the polarity of one relative to the other, then adjusting a delay so there is a sizeable acoustic null shown on an RTA at the crossover frequency. This practice doesn’t consider the start time of the audio signals. Considering phase and start time is required to deliver a system where the sound from the subwoofer arrives at the listening position at the same time as the midbass or midrange drivers.

Why Are Signal Phase and Polarity Important in Car Audio Systems?

For people who’ve upgraded their vehicles with a radio and two pair of speakers, the primary concern is that the acoustic polarity of all the speakers in the system is the same. When a speaker produces a sound, it should combine acoustically with the output of other speakers in the system. You can test this quickly without any special tools.

Play music with a reasonable amount of bass. Use the balance and fader controls to listen to one speaker at a time. Start with the front left speaker. Now, use the balance to add the front right speaker so both play. The relative bass level should increase when you add the second speaker. If it doesn’t, the wiring likely has a polarity problem.

Repeat the test with the front left speaker playing, then use the fader control to add the left rear speaker. Once again, the bass should increase. If it does, fade rearward so only the left-rear speaker is playing. Now, use the balance control to add the right-rear speaker. Once again, we should get more bass. If the bass decreases when a second speaker plays, drop by a local specialty mobile enhancement retailer and ask them to check the wiring.

Signal Summing and Cancellation

Sometimes the distances between speakers cause incomplete summing of all frequencies. Let’s go back to looking at audio waveforms for a second. If two signals have the same amplitude, frequency content and starting times, how they add together (called summing) is predictable.

In the example above, the signals combine perfectly and the total amplitude doubles. An example would be listening to music at home on a set of stereo speakers and sitting equidistant from both speakers. When it’s perfect, or at least pretty good, signals that are equal in amplitude and in phase in both channels appear to come from a spot between the speakers. Some call this a “phantom center image.” It’s just how stereo recording works and doesn’t require a fancy name.

Let’s look at how signals with different phase relationships sum. First, let’s look at two waveforms, of which one is reversed in polarity.

If one speaker moves outward and the other moves inward, their output should cancel. If you have a pair of subwoofers and one is wired backward, the result is that the system produces no bass.

Now, what happens when one signal arrives before another? Here are the waveforms if one signal lagged the other by 90 degrees:

A few bad things happen when signals don’t start simultaneously. In terms of the combined waveforms, the amplitude only increases by 25% instead of 100%. This happens if you’re at home, sitting much closer to one stereo speaker than the other. The same happens in your car, where the left door speaker is maybe 30 inches away, and the right is 45 inches away.

Audio Content and Signal Summing

Remember, music is not a single frequency, as we’ve shown in the oscilloscope plots. It’s a combination of thousands of frequencies. We don’t talk about the phase between audio signals; we talk about delay times. Every frequency has a different wavelength. So if there is a timing difference between the signals, some frequencies combine, and others cancel. The result produces an uneven frequency response.

Let’s combine some signals in Adobe Audition to demonstrate this.

I created two sine sweeps. These are 20-second tracks that start at 20 Hz and increase in frequency by 20 kHz. The image below shows that the left and right channels are equal in amplitude and phase.

Let’s look at the frequency response of the two signals:

The frequency response graph isn’t perfectly flat because I don’t have control over the speed at which the sweep occurs. In short, the bass is present for longer than the highs. What you need to know is that the response is flat and smooth.

Let’s add about 1.7 milliseconds of delay to the right channel waveform. This is the time it takes sound to travel about 24 inches. That’s not an uncommon path length difference between a vehicle’s left and right speakers.

As you can see, the results are dramatic. The frequency response is full of dips. We call this comb filtering, which happens when two sound sources are at different distances from the listening or measuring position. This could be attributed to path length differences between speakers or to a speaker’s sound reflecting off a surface and recombining with the direct-path sound. If there are path length differences, your installer can use a digital signal processor to delay the signal to the closer speaker. There isn’t much you can do about reflections other than to relocate the speakers.

Audio Signal Phase and Polarity

We hope this serves as a primer to help you understand the concepts of audio signal phase and polarity. A solid understanding of these concepts is crucial to designing and calibrating car audio systems that sound amazing. If you want better sound from your car audio system, drop by a local specialty mobile enhancement retailer today. Ask to hear one of their demo vehicles and discuss the options for improving your vehicle’s stereo.

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.