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What Is the Big Three Electrical Upgrade?

Big Three

We were recently at an event that was hosting a mobile audio system SPL competition. If you aren’t familiar with this sort of thing, it’s a contest to see who has the loudest stereo. We aren’t talking about cranking the dial on the factory radio. Instead, some of these folks build steel and concrete reinforced subwoofer enclosures and feed tens of thousands of watts to their subwoofers.

As you can imagine, delivering that much power requires significant electrical system upgrades. Many of these creations have multiple alternators and huge banks of batteries. If you’ve upgraded your car or truck with an amplifier that can produce hundreds of watts to your speakers, there’s a wiring upgrade called the Big Three that can improve the efficiency of your electrical system. Let’s look at what this upgrade is and why it’s a great starting point for a high-power car audio system.

How Automotive Charging Systems Work

The first thing you need to know about delivering power to your amplifier is that most of the energy will come from your alternator, not the battery. The battery is there to start the car. Once a vehicle is started, the alternator, which is mechanically driven by the engine, provides power to replenish the battery for the next start. The alternator also runs the computers, ignition system, fans and lights in your vehicle. Once you’ve started the vehicle, you could remove the battery and everything would, under normal conditions, operate just fine.

This scenario changes if you add a high-power amplifier to your vehicle. Say you have a 1,000-watt amplifier and you want to deliver that full amount of power to a few high-power subwoofers. At 13.8 volts, most amplifiers of this type will consume about 100 amps of current. If you have the engine running, headlights on and a climate control system in operation, your car or truck may be using 30 or 40 amps of current to power those systems. If the alternator is only rated to produce 80 amps, there certainly won’t be 100 amps left for your stereo.

The additional current the amplifier wants will come from the battery, albeit at a lower voltage. You will likely find that an amplifier rated for 1,000 watts at 14.4 volts can only produce about 800 watts at 12 volts without clipping the output signal and adding significant distortion.

Big Three
When upgrading, make sure the retailer working on your car or truck uses all-copper, full AWG-spec power and ground cables like those from Rockford Fosgate.

How To Make the Most of Your Alternator

The first step in optimizing the electrical system in a car or truck is to reduce waste. In this case, waste is the power converted to heat because of resistance in cables and connections. First, have a look at your alternator and battery. How large are the wires running to and from them? Unless you have a big truck with a high-output alternator, chances are that the wiring is 4 or maybe even as small as 6-AWG.

Big Three
Aftermarket alternators like those from Ohio Generator can produce over 350 amps of current. They are going to need significant wiring to supply large amplifiers.
Big Three
Is a single run of 0-AWG power cable enough for almost 400 amps of current from a Singer alternator? Likely not.

Please make no mistake about it, the company that built your car or truck deliberately chose the smallest, lightest and least expensive wire that would allow the vehicle to function reliably. They had no intention of providing conductors that could handle two to three times what the alternator was rated for.

The Wiring Upgrades that Make the Difference

The Big Three upgrade involves adding to or replacing the existing conductors with larger, high-quality wires. The upgrades in the Big Three are:

  • The run from the alternator chassis to the negative terminal of the battery.
  • The run from the output of the alternator to the positive terminal of the battery.
  • The ground connection from the negative terminal of the battery to the chassis of the vehicle.
Big Three
A representation of the wires that need upgrading to complete the Big Three.
Big Three
It’s not unreasonable to run multiple cables to the alternator to optimize power delivery to numerous electrical systems.

Depending on your vehicle, there may be other wires that can be upgraded at the same time. For example, if there is a main power distribution box under the hood, running new wire to it can help provide more voltage to the factory-installed electrical and electronic components in your vehicle.

Big Three
Two runs of 4-AWG power wires feed the factory fuse block in this Jeep Grand Cherokee.

Another upgrade you may want to make at the same time is replacing the battery terminals. Some factory-installed terminals are notoriously flimsy. If you’re demanding significant current from the battery, then optimizing each component along the way only makes sense.

Big Three
Stamped steel battery terminals don’t provide much room for upgrade.
Big Three
High-quality plated brass terminals like these from Audison Connection allow your installer to maximize current transfer from the battery.

Is the Big Three Enough?

In 2012, we wrote an article about upgrading the stock electrical system wiring in modern cars and trucks. Even though it was a decade ago, new vehicles at the time were being constructed out of materials like QuietSteel and aluminum, and some companies had started using adhesives instead of spot welds to bond unibody panels together. All of these advances in vehicle assembly work against our desire to deliver large amounts of current to an amplifier, especially when we want to use the body as the ground return path.

Power delivery from the positive terminal of the alternator is as important as the ground connection to the chassis and battery. If the current can’t flow through both, you are wasting energy by transforming it into heat. Upgrading and adding grounds with the Big Three is a start. If you are serious about optimizing your electrical system, then you’ll want to add a ground wire from the battery or alternator directly to your amplifier. Back in 2012, we called this the Big Four.

Big Three
Having a ground wire run from the battery or alternator to the ground location of your amplifier can dramatically improve current flow.

Full disclosure: This wasn’t our idea. The first we heard of running a dedicated ground wire was when we were checking out Precision Power’s fleet of Chevrolet Suburban demo vehicles back in the ’90s. The topic came up again when Ford introduced QuietSteel in the F-150 vehicles, and companies were having problems with amplifiers failing because of low voltages. As a solution, JL Audio suggested adding what they called a parallel ground. This wire would connect to a conventional ground point in the rear of the vehicle and run to the battery’s negative terminal or the alternator. A benefit of the parallel ground is that it offers less resistance than a dedicated ground wire or using the chassis. As a result, current can flow through both paths, reducing the voltage drop and improving system performance.

Optimize Your Vehicle Electrical System

If you’ve purchased a high-power amplifier for your vehicle, talk to your local specialty mobile enhancement retailer about upgrading all the wiring in the electrical system. Implementing an upgrade like the Big Three or, better yet, the Big Four will allow the amplifier to produce more power and allow the system to play louder with improved reliability and efficiency.

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

Let’s Talk About Remote Starter and Security System Range

Remote Range

Range is the critical factor in the quality and performance of a remote car starter or security system. That’s the distance between you and your vehicle when you’re sending a lock, unlock or remote start command, or are hoping to receive a security notification. If you aren’t close enough, or the convenience system doesn’t have enough power, signals may not reach the vehicle or the remote.

Remote Starter and Security System Key Fobs

The handheld remote that comes with your vehicle or an aftermarket starter uses radio frequency communication to transmit commands. These work in a similar fashion to a radio station in that they broadcast in a circular pattern from the remote. If your vehicle is close enough and the signal is strong enough, the receiver in the car or truck will relay the command to the control module and execute the function.

Let’s look at two-way remote controls. A two-way remote sends a command such as “unlock” to the vehicle when you press the button. When the command has been received and the doors are unlocked, the transceiver in the car sends a command back to your remote to let you know the request was executed. The benefit of this two-way communication is that you always know the status of your car or truck. There’s no need to guess whether the doors are locked or the engine is running.

Remote Range
Two-way remotes like the new Compustar R5 allow security warnings from the car or truck to alert you when something is wrong.

How Do Remote Car Starter Companies Define Range?

No matter which brand of convenience or security system you’ve chosen, they all try to describe the distance between the vehicle and the remote in a measurable range. The simplest aftermarket remotes usually offer about 1,000 feet (about 300 meters) of range under ideal conditions. The step-up systems provide solutions that work at ¼ mile, 3,000 feet (914 meters) or 1 mile (1.61 kilometers). Some companies offer ultra-long-range radio frequency remotes that can deliver 2 or even 3 miles of range.

All manufacturers of remote start systems calculate these distances based on ideal controlled conditions. With trees, houses or buildings between you and the vehicle, the maximum functional range will decrease dramatically. If you’re inside a building (apartment, office tower, factory, hospital, etc.), that will decrease the effective range. A lot of electrical interference from communication systems will also reduce the usable range. We’ve seen cases where a specific remote solution worked great in one city but barely worked at all in another because a nearby military base was broadcasting something in the same frequency range.

To compare remotes, consider their power levels. The simplest 1,000-foot models could be your distance benchmark. A remote that offers 3,000 feet of range isn’t just three times more powerful; it’s closer to eight times as powerful. Because the signal radiates in a circular pattern, the power level needs to be about four times stronger to double the distance. That would mean a transmitter needs to be 16 times stronger to quadruple the effective distance. So, a remote that offers 1 mile of range is just over 25 times more powerful than one that only provides 1,000 feet of functionality. The 2-mile remotes are 100 times more powerful than the 1,000-foot models, and 3-mile units are an amazing 223 times more powerful.

Manufacturers of remote start and security systems work to increase range in other ways. The first is to switch from amplitude modulation (AM) signal to frequency modulation (FM). As you may have noticed on your car radio, FM offers better noise rejection than AM. The second method to improve range is to use what’s known as frequency-hopping or spread-spectrum communication. A simple way to understand this is to think of spread-spectrum systems as a group of people yelling a command rather than a single person. If there is noise interfering with one person yelling, the message from one of the other people is still likely to get through.

Remote Range
AM, FM and digital spread spectrum (DSS) communication technologies vary in their ability to send a command to the brain of your starter or security system.

Why Is Remote Range Important?

If you park your car in the driveway of your house and want to start it before work, you don’t need much range. A 1,000-foot system will likely be more than adequate. If you’re in an apartment on the fourth or fifth floor and the car is parked below you, the same applies. However, if you live on the other side of that apartment building, you’ll need to send a much stronger signal.

Think, too, about where you work. Do you work in a small office where your car is parked outside the window? If so, 1,000 feet is lots of transmitting strength. What if you work in a hospital, a distribution warehouse or a manufacturing facility and your car is 1,500 to 2,000 feet away? There may also be mechanical and electronic equipment along with the metal structure of the building between you and the vehicle. You may need 20 or 50 times as strong of a signal to let you start the car.

Logically and not incorrectly, you could wait until you were at the door to the parking lot to start your car and let the air conditioning run in the summer or get the heater working in the winter. However, if it’s the latter, the car won’t warm up much in the two or three minutes it takes to walk across the parking lot. The whole purpose of a convenience system is to make the vehicle more comfortable when it’s time to drive away.

If you have a security system or security features tied into a remote starter, you can receive warnings from the alarm portion of the system on some premium two-way remotes. If you’ve parked your car or truck at a big shopping mall, it’s not unreasonable that you’d be more than a quarter-mile away. With that said, the ¼-mile system isn’t going to work with concrete and steel walls, dozens of stores and hundreds of people on their cell phones between you and your vehicle. Transmitter power is fundamental here – both from the remote and from the transceiver in the vehicle.

A Quick Test of Remote Starter Range

To quantify some of the range claims, we headed to a local light-industrial area to test how far away we could be and still receive a reliable confirmation that a command from our remote worked. The first system featured a two-way remote control with a color display that’s marketed as offering 1 mile of range. We used the infamous remote-to-chin trick (which turns your head into an antenna) to maximize performance, and we were able to get the system to function at a distance of 2,000 feet (615 meters).

The second system features a one-button remote with LED confirmation. It’s listed as providing up to 2 miles (3.2 kilometers) of range. We managed an impressive 1.11 miles (1.78 kilometers) in our urban test scenario. Just as a note, the battery in this remote was a year old, so there is a slight chance we could have bettered that number.

Nevertheless, the real-world numbers in this test came in at 38% and 55% of the maximum the companies use in their marketing. Given the caveats of interference, these aren’t surprising. If we were in a remote part of Texas or Saskatchewan with flat terrain with no trees, cell service, radio stations or buildings, we’d have no problem believing that these systems would deliver every inch of their ratings.

Remote Range
How far away from our cars did the remotes work in the city’s light commercial area?

We took the long-range system to a local shopping mall for a second test and parked at the very southwestern corner of the parking lot. We parked facing the door and in line with the long center hallway in the mall. This positioning would provide a best-case scenario in terms of range.

The first test was to check out the factory keyless entry system. As we walked through the parking lot, we pressed the lock button. At a distance of 195 feet (60 meters), we had to turn around and face the car for it to respond. This continued to work right up to the door of the mall at 290 feet (88 meters). The vehicle continued to react once we were through the first set of doors but not after the second. So, we’ll call that about 300 feet (100 meters) of range.

We switched to the one-button two-way LED remote that’s marketed as offering 2 miles (3.2 kilometers) of range. We continued in a straight line down the mall’s main corridor into the large department store at the end. Just as we passed the perfume section a quarter of the way through that store, we ran out of range. That’s a total of 1,400 feet (427 meters).

Given the line-of-sight benefit, we decided to stray off down a few of the side corridors. A little to the north, with a few dozen more stores in the way, the range was down to 920 feet (280 meters). Farther west of that, with even more stores between us and the car, the range was down to 740 feet (225 meters).

At no time were we disappointed with the test. It was amazing to see just how far we could get and the types of interference that reduced the effective range. On the other hand, it was no surprise to see how poorly the factory remote fob worked.

Remote Range
Being in a building dramatically reduces the range of your remote car starter or security system remote.

What Do You Need To Know About Remote Range?

Just as with some of the overzealous power ratings on speakers and amplifiers we see, using the longest range possible in marketing information is just a part of reality when it comes to the performance of remote starter, security and convenience systems.

When buying a remote car starter or security system for your car or truck, think about the worst-case scenario in terms of how much transmitting power you’ll need. We’ve heard of people starting their vehicles from a monorail when more than a station away from their stop or while flying into a small airport in a small commuter plane.

If you want your vehicle to be comfortable and ready to go when you are, extra power from the car starter or security system remote will give you more warm-up/cool-down time. Drop by your local specialty mobile enhancement retailer today to find out about the security and convenience solutions available for your vehicle.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

Filed Under: ARTICLES, Remote Car Starters, RESOURCE LIBRARY

The Car Audio Distortion Food Chain

Audio Distortion

When it comes to expressing the quality of an audio system component, the amount of distortion it adds to a signal is the defining factor. In this article, we’ll talk about how much distortion each part of an audio system adds – so that you can target your budget for the greatest benefit. We’ll rank four categories of audio equipment based on the amount of distortion they add to your music. Ultimately, our suggestion is to optimize your upgrade budget by focusing on the products that will deliver the most significant improvement in perceived audio quality.

What Is Audio System Distortion?

Distortion is the addition of unwanted information to an audio signal. In minimal amounts, distortion can be difficult to perceive. However, above a level of about 0.5%, distortion is audible and can change the music’s tonal balance and perceived dynamics.

It’s become clear that most people think distortion is only present in an audio system when a speaker is overdriven or an amplifier starts to clip. While that level of distortion is very audible, unwanted harmonic and intermodulation distortion is added even at moderate listening levels. For example, a low-quality amplifier providing less than a watt of power to a speaker can add almost 1% distortion to the signal. A poorly designed speaker or one operating outside of its intended frequency range can easily add 3-5% distortion, and a subwoofer driven at moderate levels can be well over 10%.

No. 1 – Speakers and Subwoofers

If the paragraph above wasn’t enough of a hint, let’s make it clear: Speakers and subwoofers are notoriously non-linear. Let’s say you’re feeding a 100 Hz sine wave into an inexpensive woofer. If the design has less compliance (more stiffness) in the forward direction relative to the rearward, the driver’s output will be reduced for half of the waveform. That’s distortion. If the driver has changes in inductance relative to forward or rearward motion, there will be a reduction in output over one half of the produced audio waveform. Distortion is also possible from resonances in the cone, surround and dust cap that add significant unwanted energy.

You need to know that ALL speakers add more distortion as they are driven to higher excursion levels. Aside from not using a properly designed or constructed enclosure for your subwoofers, or trying to play the woofers in your doors at frequencies below 80 Hz, louder means less quality.

When shopping for car audio upgrades, look for speakers that include distortion-reducing technologies. We’ve talked about copper and aluminum shorting rings, copper caps and flat progressive spiders. To minimize power compression (a reduction in output as the speaker is driven at higher levels), you’ll need to choose a solution that balances cooling features like a large-diameter voice coil with acceptable high-frequency performance.

Last but certainly not least, the product specialist you’re working with needs to design, install and calibrate your audio system properly. Proper speaker mounting adapters and spacers made from weather-resistant materials are a starting point for installation. Choosing driver sizes that offer good directivity performance, so your music sounds great from both sides of the vehicle, is another important criterion. Finally, setting crossovers, equalization and signal delays to create a realistic listening experience is crucial. Getting any of these steps wrong will reduce your enjoyment of your favorite music.

Audio Distortion
The Rockford Fosgate Power Series T3652-S component set features woofers with an integrated shorting ring and a large 38 mm voice coil former for excellent power handling.
Audio Distortion
The three-way Audison Thesis TH K3 II A Orchestra features an aluminum shorting ring on the mid and a massive 50 mm voice coil on the woofer for great sound at high volumes.
Audio Distortion
The RS Series speakers from ARC Audio include copper shorting rings in the motor assembly, papyrus-damped pressed paper cones and a unique dust cap that prevents resonance.
Audio Distortion
The woofers in the Sony Mobile ES drivers use a shorting ring to improve upper midrange clarity. Extensive cooling technologies ensure great sound with the volume cranked.

No. 2 – Amplifiers

If you’ve read our articles on distortion, then you know that we have a passion for testing amplifiers. At their worst, amplifiers add maybe 1/10th of the distortion to an audio signal that a low-quality speaker does. This doesn’t mean that they aren’t in a solid second place in terms of where you should invest in an audio upgrade.

Amplifiers are supposed to amplify a signal – nothing more, nothing less. They should output what you feed to them without adding warmth, brightness or changes to overall tonal balance.

Low-quality or poorly designed amplifiers can add distortion because of the crossover between the positive and negative output devices. In addition, they can exhibit frequency response issues from poorly designed bass boost and filter circuits. Amplifiers with high output impedance can be affected by changes in load impedance.

A second consideration for amplifiers is noise. If you turn your car stereo system on and hear a lot of hiss, it’s likely from the amplifier. Every amplifier adds a little background noise. Whether noise affects your enjoyment depends on just how much is added. The signal-to-noise ratio lets you know what’s going on behind the scenes.

A few quick tips for buying high-quality amplifiers: As far as Class-D amplifiers have come, they are best suited to powering woofers and subwoofers. The output filter networks can get a little fussy at higher frequencies. As such, Class-AB amplifiers are better for midrange and high-frequency duties. Second, the physical size of an amplifier significantly affects how much noise is added to the output. Small amplifiers are typically noisier. Third, watch how specifications on distortion are provided. The ANSI/CTA-2006-C standard requires that distortion and noise numbers be published when measured at an output level of 1 watt into a 4-ohm load. Measurements at other levels may be misleading.

Audio Distortion
Even though they were designed decades ago, the Signature Edition amplifiers from ARC audio remain a staple when it comes to clarity.
Audio Distortion
As the four-channel in the Thesis amplifier family, the TH quattro delivers impressive performance and can be fed digital signals directly from a DSP.
Audio Distortion
Rockford Fosgate’s T600-4 delivers 100 watts of power per channel and checks all the right boxes for excellent distortion and noise performance.
Audio Distortion
With impressive noise performance and frequency response that extends to 100 kHz, the Sony XM-GS4 is a quality solution that punches well above its price point.

No. 3 – Source Units

We’ve tested several source units lately, and though their effect on sound quality isn’t as dramatic as the speakers and amplifiers you choose, there are measurable differences from one model to another. While amplifiers have to deal with high voltages and significant current delivery, the signals inside a radio or multimedia receiver are pretty small. These low levels mean that noise from a power supply can affect what you hear.

Back in car audio’s heyday, we had CD units like the Sony Mobile ES CDX-C90, Clarion ProAudio DRZ-9255 and Alpine’s F#1 Status DVI-9990E. Of course, the days of high-end CD players are gone, but there are still a few options for a high-quality source unit.

Picking a good head unit is tough. You’ll likely choose between something mainstream with good performance or an upgrade to something designed to offer better sound quality. For example, we used to suggest 24-bit Burr-Brown D/A converters. Now, those are in almost every multimedia receiver. Our advice is to choose a product that has the features you want and is clearly designed to deliver improved audio quality.

Audio Distortion
The current godfather of great sound, the Sony RSX-GS9 is a digital media receiver that supports DSD and other media files with preamp output capabilities to 90 kHz.
Audio Distortion
The XAV-9500ES is a floating-display multimedia receiver that’s part of the Mobile ES Family. Full DSP, support for High-Resolution audio and smartphone integration make this a modern home run!
Audio Distortion
The eXcelon Reference DNX997XR from Kenwood combines premium connectivity with support for high-resolution media file playback.

No. 4 – Digital Signal Processors

Putting the DSP family at No. 4 in our list might puzzle anyone who understands how DSPs work and why they are an absolute necessity in a premium car audio system. Let’s make it clear that you need a DSP to equalize and filter the signals going to your speakers for them to deliver realistic performance. As such, a DSP is one of the most important components in an audio system. Its ranking in this article is based on whether or not you need to allocate extra funds to purchase a product in each category to yield better performance. So, having a DSP is a requirement; buying the fanciest one on the market won’t make a huge difference to what you hear.

Having said that, there are subtle differences, especially between entry-level and premium solutions. For example, most digital signal processors use similar DSP chips to perform the audio adjustments. As these are handled in the digital domain, the differences in transparency are more about the analog circuitry and the conversion process.

One tip: Don’t let yourself be fooled by claims about support for high-resolution in a DSP. In most cases, the analog-to-digital and digital-to-analog converters are noisier when running at higher frequencies. Stick with solid performance and ensure that you have an expert configure the system, and you’ll be delighted.

Audio Distortion
The PS8Pro digital signal processors from ARC Audio offer impressive sonic clarity and feature full support for the Maestro AR amplifier integration modules.
Audio Distortion
If you need to undo signal processing in your factory audio system, the bit One HD Virtuoso is the tool of choice. It can tame delays, equalization and all-pass filters to create a perfect starting point for an amazing audio system.
Audio Distortion
The DSR1 from Rockford Fosgate features eight output channels with complete filter, equalization and delay functions. Integrated Maestro AR technology helps to ensure that your audio system will work smoothly.

Choose Your Car Audio Upgrades Wisely

Here’s one last thought on buying high-quality car audio equipment: Every brand on the market is competing for your dollar. Some of them offer excellent products that result from hours, if not years, of designing and testing to deliver the best possible performance. On the other hand, some products are just expensive while delivering mediocre performance. So make sure you take the time to audition several options from different specialty mobile enhancement retailers near you.

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

Car Audio Speakers Aren’t Resistors

Speaker Resistor

A while back, we took a quick look at how alternating current (AC) signals in our car audio systems work. While the amount of work done by an AC voltage source can be the same as that of a direct current (DC) source, the changes in current flow direction add complications. In this article, we’ll dive a little deeper into AC signals and explain why a fixed-value resistor can’t directly simulate a speaker.

Ohm’s Law – AC and DC Current Flow

Ohm’s law is a constant for both DC and AC circuits. When 1 amp of current flows through a resistor with a value of 1 ohm, then 1 volt of electric potential will be produced across that resistor. If the resistor value is increased to 2 ohms, and we apply 1 volt across it, then 0.5 amp of current flows through it. The triangle below shows the three ways we can calculate voltage, current or resistance if we have two of the other variables.

Speaker Resistor
Ohm’s law allows us to do calculations based on voltage (V), resistance (R) and current flow (I) in AC or DC circuits.

In an AC circuit, we know that the current flow switches back and forth. In home and commercial electrical systems, the voltage is in the shape of a sinusoidal waveform. The work done by the voltage or current is an average level of the signal. For a sine wave, the average level, called the RMS level, is 0.707 times the peak voltage referenced to the ground.

Speaker Resistor
The amount of work a sinusoidal AC signal can perform is 0.707 times the peak voltage relative to the ground reference.

Alternating Current Signals Are Complicated

When current flows through a conductor, it creates a magnetic field around that conductor. This phenomenon is known as Oersted’s law, named for Danish physicist Hans Christian Oersted, who discovered this relationship in April 1820.

Speaker Resistor
When current flows through a conductor, a magnetic field is created around that conductor.

In a DC circuit, if we have current flowing through a coil of wire, the magnetic field created in that coil opposes changes in current flow. If we remove the voltage source, the current will continue to flow, even if only for a few milliseconds. This phenomenon is why many automotive relays have a diode on the bottom of a socket. The diode shunts the reverse-polarity current spike that results when we remove the voltage source. As a result, the magnetic field in the relay coil collapses and produces a voltage spike. This spike can damage the circuitry driving the relay or cause arcing in a switch.

Speaker Resistor
Using a relay with an integrated flyback diode helps prevent damage to the device controlling the circuit.

Audio Signals Are Complicated

The current flowing to a speaker (or more specifically, a tweeter) may change direction as often as 20,000 times a second. All speakers (that we will worry about) use a voice coil that creates a magnetic field that makes the cone move. This same magnetic field opposes changes to the current flow direction. As such, we have more opposition to AC flow than we would for the same amount of DC current.

If we connect a digital multimeter to a speaker, the meter applies a tiny DC current to the voice coil. The number on the meter screen tells us the DC resistance in voice coil winding.

For AC circuits, we need to measure impedance. The Oxford Dictionary defines impedance as “the effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance.” Since we skipped over it, reactance is the opposition to AC current flow caused by inductance or capacitance. For example, the voice coil in a speaker will act as an inductor at mid to high frequencies.

Let’s look at a sizeable 6.5-inch woofer. If I use a high-quality digital multimeter to measure the resistance, we get a reading of 3.7 ohms.

Speaker Resistor
DC resistance of our old-school 6.5-inch woofer.

If I want to know how the speaker opposes the flow of AC current, I need to feed it an AC signal and measure the opposition to current flow at any frequency relevant to the application for the driver. For this article, I’ll use the Smith & Larson Woofer Tester 2. This device can measure DC resistance and inductive and reactive capacitance at any frequency up to 20 kHz. The result is a plot of impedance (AC opposite to current flow) along with a phase plot that tells us whether the load is capacitive or inductive.

Speaker Resistor
The impedance of an old-school 6.5 woofer as measured by the Woofer Tester 2.

If we look closely at the impedance measurement, we can see that the woofer has an impedance of about 30 ohms at a frequency of 42 Hz. This is the driver’s resonant frequency (Fs) and represents the point at which the least amount of current produces the most output.

At higher frequencies, the inductance of the voice coil becomes the primary opposition to AC current flow in the speaker. The Woofer Tester 2 measured the inductance of this driver as having a value of 0.827 millihenry. You can see that the impedance starts to rise at an exponential rate above about 250 Hz. By the time the drive frequency is at 20 kHz, the impedance is approximately 54 ohms.

Driving a woofer or subwoofer is one type of challenge for an amplifier. This task requires significant amounts of power. The load can also be heavily reactive, meaning current and voltage may not be in phase with each other.

Driving a set of component speakers is an entirely different scenario. Even the most minute changes in output level can be readily apparent to the listener. Since speakers can present significantly varying impedances based on frequency, the voltage and current supplied by the amplifier will change as well. These variances in load impedance can result in small changes in output level as the amplifier’s circuitry interacts with the load to create a voltage divider. In systems where there is no equalization, especially in home audio systems, these variances can change how the listener perceives the music.

Speaker Resistor
This combination of capacitors, inductors and resistors presents amplifiers with a wildly reactive load to evaluate how it will behave.
Speaker Resistor
The impedance (orange) and phase (blue) measurements of the BestCarAudio.com simulated load circuit.

We created this complex reactive load to challenge amplifiers that cross the BestCarAudio.com test bench. We take frequency response measurements into all the rated loads for the amp and a measurement when connected to this simulated reactive load. Better amplifiers exhibit smaller changes in output level relative to changes in load impedance.

Speaker Resistor
The voltage an amplifier produces across a load can be dependent on the impedance of the load and the design of the amplifier.

The graph above shows the effective frequency response of an amplifier when fed a 4-ohm resistor (in red) and 2-ohm resistor (violet) and our reactive test load (in black). As you can see, the output of the amp varies depending on what it’s connected to. This phenomenon is more common with Class-D amplifiers than with Class-AB designs.

Why Is Impedance Important to Car Audio Systems?

There are a few takeaways from this article. First, if you measure the resistance of a speaker with a multimeter, you are getting a general feel for its ability to pass current. For example, if the meter measures 3.7 to 4.2 ohms, then you have a nominally 4-ohm speaker.

However, if you intend to design passive crossovers, you need to know the exact impedance around the crossover frequency to choose the correct values. While very few people create passive crossovers these days, we do see many people suggesting that those circuits are interchangeable between different brands, makes and models of speakers. Nothing could be further from the truth. You can’t assume a crossover designed for Brand A speakers will function adequately or sound right with Brand B.

Another consideration about AC signals surfaces when measuring power in a reactive load (like a speaker). The opposition to changes in current means that current peaks lag behind voltage peaks in inductive loads. If you want to measure power from an amplifier when connected to a speaker, you need to measure current and voltage simultaneously. We don’t mean by using a voltmeter and current clamp and taking peak readings. You need to measure both using something like the D’Amore Engineering AMM-1. Those “clamped” power readings the SPL guys talk about are meaningless.

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

Choosing the Best Speakers To Upgrade My Car Stereo System

Best Speakers

When upgrading your car stereo, speakers are the only link between your electronics and your ears. Unfortunately, low-quality speakers connected to the best amplifiers and source units in the world will still sound mediocre at best. In this article, we’ll take a look at the classes of speakers available for your car or truck. In addition, we’ll provide some tips to help you expedite the process of working with the Product Specialist at your local retailer to end up with the best value and performance for your investment.

Start by Determining Speaker Sizes

The first thing that needs to be determined is the size of the speaker you’re hoping to upgrade in your car or truck. In the car audio industry, the most common speaker sizes are 6.5-inch and 6×9. With that said, there are 3.5-, 4-, 5.25-, 6-, 6.5-, 6.75- and 8-inch round speakers, along with 4×6, 4×10, 5×7, 6×8, 6×9 and 7×10 oval speakers. The Product Specialist you’re working with will likely know what size speaker is in your vehicle or they’ll remove a trim panel to check.

Best Speakers
The Punch Series of speakers includes coaxial and three-way options in round sizes from 3.5 through 6.75 inches in diameter.
Best Speakers
Hertz speakers in the Dieci Series cover all the popular oval sizes currently used in cars and trucks.

Once you know the speaker size, the next step in terms of physical requirements is to consider your vehicle’s mounting depth and protrusion limits. The mounting depth refers to how much space is available behind the speaker mounting surface for the speaker basket and motor (magnet) assembly. The limiting factor for door speakers is usually the distance to the window when the lower edge is behind the bottom of the speaker. For dash speakers, the limitation is often venting from the climate control system. For rear parcel shelf speakers, torsion-type springs that hold the trunk lid open are the primary concern.

The second consideration is the amount of space available in front of the speaker. If the installation will use the grille included with the speaker, then this isn’t a problem. However, if the speaker will be installed behind the grille that came with the car, then adequate space must be provided for the tweeter, and the woofer at its maximum forward excursion limit.

Best Speakers
The angled tweeter on the Audison Voce AV X 6.5 delivers excellent performance but adds 7/16 inch to the speaker’s height.

If there’s room, the technician working on your vehicle may choose to build a spacer out of plastic or a composite to move a deeper speaker outwards. It’s worth repeating (as we have many times) that wood spacers don’t last very long in a car or truck door. They will get wet when it rains, and even when painted, coated in fiberglass resin or sprayed with an undercoating, they will eventually swell and become moldy. This deformation is rarely even and can damage or break high-quality cast-basket speakers. Materials like cast acrylic, ABS, high-density polyethylene and expanded PVC are good options for spacers. Most reputable shops will have these materials in stock and will cut custom spacers for your application. We’ve even seen spacers constructed from composite kitchen countertop materials like DuPont Corian. Companies like Metra offer vehicle-specific speaker spacers and mounting adapters to allow for reliable installations that don’t require any fabrication skills.

Best Speakers
This set of speaker adapters was milled from two sheets of 0.5-inch Corian to fit the doors of a Subaru WRX.
Best Speakers
B.J. Curcio at Broken Silence Custom Car Audio in Greenwich, Connecticut, cut these mounting adapters for a set of Triton tweeters using his CNC laser.

Speaker Design

Once you’ve determined the size of speaker that’s suitable for your application, you’ll need to decide on your goals for the audio system. We aren’t quite at the stage where we’ll talk about performance and quality, though. This step involves deciding if you are going to want a coaxial speaker or a component set.

In a coaxial speaker, the tweeter, or a tweeter and super-tweeter are integrated into a single chassis along with the woofer. The benefit of these systems is that they are typically an all-in-one speaker solution. However, if you’re replacing the front speakers in a vehicle, you may want to consider using a component speaker set. In most cases, a two-way component speaker set includes a pair of woofers and tweeters. The woofers would be mounted in the door location, and the tweeters would go in the dash location, in the A-pillars, up high in the doors or in the sail panels. The benefit of a component set is that the higher mounting position of the tweeters may afford better high-frequency delivery, and the source of the sound in the vehicle may be at the dash or windshield level instead of down near your legs.

Best Speakers
Sony’s Mobile ES Series includes the 6.5-inch coaxial.
Best Speakers
Oval 6×9 speakers often can have as many as five drivers. This Sony XS-R6949 has a woofer, a small midrange driver and a pair of super-tweeters.

In the case of component speakers, most include an external passive crossover network. This compact circuit includes capacitors, inductors and often resistors that divide the audio signal from a radio or amplifier into different frequency bands and send the bass and midrange information to the woofer and high-frequency information tweeter.

Component speaker sets are also available as a three-way solution for cars that use a woofer, a midrange driver and a tweeter. In most cases, the mid and tweeter are mounted higher in the door or in the dash to help raise the sound source.

Best Speakers
The APK 163 set from Audison includes a pair of 6.5-inch woofers, a pair of 4-inch midrange drivers and a set of 1-inch tweeters with passive crossovers for each pair.

Suppose you’re seeking the best possible performance from your audio system. In that case, a three-way speaker set that’s installed in combination with six channels of amplification and a digital signal processor is the way to go. We won’t get into DSP applications in this article as we’ve covered it many times already.

If you’re going the DSP route, many companies sell their mid- to high-performance drivers in pairs. The Product Specialist can help you chose a woofer size, an appropriate midrange solution and tweeters to create a bespoke configuration for your vehicle’s speaker locations.

Best Speakers
The RS Series speakers from ARC Audio are sold in pairs. You can pick from the 1-inch tweeters, 3- or 4-inch midrange drivers and the 6.5-inch woofers.

Speaker Selection Considerations

Now we get to the part where you decide what level of performance you want from your audio system. Do you need an inexpensive speaker to replace one that came from the factory that’s worn out, or are you trying to upgrade the audio system to deliver clearer, more detailed sound? Part of this consideration includes deciding how much power you have available and your preferred listening level.

For example, suppose you want to recreate the Kiss concert in Ottawa, Ontario, from back in the 1970s. The show reached an output level of 136 decibels. In that case, you need speakers that can handle a lot of power, have significant woofer cone excursion capabilities and include features that will help to ensure they sound good when played loudly.

A quick aside here: Speakers are much more complicated than most people think. For every speaker, as it plays louder, more distortion is added to the output signal due to mechanical and electrical non-linearities, along with cone, dust cap and surround resonances. If you want a speaker that will be clear when played loudly, then choosing something with technologies like a copper or aluminum shorting ring and a copper cap will help. The diameter and length of the voice coil play a prominent role in determining peak power handling. Some 6.5-inch mid-woofers have 2-inch diameter voice coils. Likewise, the suspension should use a flat, progressive spider, and the cone, cap and surround should be designed to eliminate resonance. It’s a complicated balancing act to get this perfect.

Let’s back up here. If you want your music loud, then you’ll need to consider the speaker power handling specifications. If they’re compliant with the ANSI/CTA-2031 standard, those numbers will tell you how much heat energy the speakers can dissipate before they are damaged. Power ratings do NOT define the quality of a speaker. There are terrible-sounding speakers with high power ratings and some that sound quite good with low ratings. Car audio enthusiasts need to stop buying speakers based on power ratings.

Auditioning Speakers Helps Determine Quality

Most car stereo shops have display boards that can be used to audition speakers. Here are a few quick tips. First, when switching from one speaker set to another, try to make the listening level equal. Even slightly louder speakers will sound better because you can hear the quieter parts more clearly. Second, bring one or two songs you know pretty well to the store to listen to the speakers. A dynamic track with a wide frequency range will tell you a lot about the dynamic and damping characteristics of a speaker. A song with clear male and female vocals will tell you a great deal about the clarity and accuracy of the drivers. Lastly, listen to them for a short time at high volume levels. If they sound stressed, they are likely missing distortion-reducing technologies.

When shopping, your goal is to find the speakers that sound the most accurate for a given price point. For a 6.5-inch speaker set, you can pay anywhere from about $55 for an introductory-level two-way coaxial speaker to well over $5,500 for a premium two-way component set. The power handling, output capability, frequency response and, most importantly, the speakers’ clarity increase as you move up the price range. Better speakers reproduce audio signals more accurately, recreating the original sound from the recording studio in your vehicle without adding unwanted emphasis, leaving anything out or adding distortion.

Upgrade Your Speaker Upgrade

You can improve the performance of your audio system significantly by having sound deadening installed in the doors of your car or truck. High-quality deadening products reduce the transfer of noise energy into your vehicle and make it easier to hear the quieter parts of your music.

If you have a vehicle with large openings in the door, sealing those with fiberglass or plastic and then covering the area with deadening can dramatically improve a door speaker’s bass and midbass performance. We’ve seen gains in output of 10 dB from the addition of sound deadening alone.

Best Speakers
Mobile Toys in College Station, Texas, lined the interior of this Ram pickup truck with SoundShield sound deadening material.

Another upgrade that can help with the performance of your speakers is to have your installer add a set of rubber or foam gasket rings around the drivers. These rings help to seal the gap between the door and the speaker to prevent sound from bouncing around and potentially causing cancellation.

Best Speakers
RoadKill Fast Rings from Stinger Electronics help improve the performance of your door speakers.

The Best Way To Improve Your Door Speakers

Finally, if you’re after the best performance possible from a set of door speakers, the best upgrade you can make is to add a subwoofer system to your vehicle. Relieving the speakers’ need to reproduce bass frequencies below 80 hertz can significantly cut the power sent to the speakers. Just as we mentioned earlier, the speakers won’t need to work as hard and consequently will add less distortion to the audio signal. The result will be a system that can be played at higher volume levels with less distortion. That’s a win-win!

When it’s time to replace or upgrade the speakers in your car or truck, drop by a local specialty mobile enhancement retailer and audition the options available for your vehicle. Always remember, when it comes to sound quality and accuracy, the speakers in your vehicle are your most critical consideration.

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

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