In a recent online discussion, someone stated that a car audio amplifier couldn’t be power-hungry. After the eye-twitching passed and our heart rates settled, we knew this was a perfect topic for our series on car audio myths. Let’s look at how amplifiers, specifically subwoofer amplifiers, make use of the power from your vehicle’s electrical system.

What Is Amplifier Efficiency?

There’s no electronic device on the planet that is 100% efficient. If the electrical system in your car supplied 12V and 100 amps of current to an amplifier, that would be 1,200 watts. That amplifier can’t convert 100% of that energy into power to drive a speaker. Yes, the Rockford Fosgate T15kW amplifier had a bank of ultra-capacitors built in that allowed it to produce more power than it consumed for a few seconds. We’re talking about normal amplifiers in this article.

Calculating amplifier efficiency is relatively easy if you have the right tools. First, you need to measure the power going into an amplifier. Since a DC voltage powers amplifiers, a voltmeter at the amplifier terminals and a current clamp or current shunt resistor can give you the information you need. Next, you need to measure the power coming out of the amplifier. Measuring AC signals can be complex because the current and voltage might not be in phase at all frequencies. A tool like the D’Amore Engineering AMM-1 works great because it takes the phase relationship between current and voltage into account in its power calculation. Once you have the two numbers, you can divide the power coming out of the amp by the power going in, multiply by 100, and you’ll have the percentage efficiency.

Examples of Amplifier Efficiency

A good example of an efficient amplifier would be the Rockford Fosgate M5-1000X1 that the BestCarAudio.com gang reviewed earlier in 2021. When driving a 1-ohm load, the amp produced 975 watts at 1% THD+N. The supply voltage was 13.75 at the amp terminals, and the amp was consuming about 98.5 amps of current. The efficiency was 72%.

Another great amplifier is the ARC Audio ARC 1000.4 that was also reviewed earlier in 2021. This four-channel amp produced 1,406 watts when driving a pair of 4-ohm resistive loads. The amp was fed with 13.37 volts and consumed 137.1 amps of current. The efficiency was 77%.

Both of these companies have world-class engineering and design teams behind the products they sell. Sadly, this isn’t always the case. Here’s an example from the other end of the spectrum. Our friends at Of Sound Mind Labs tested a monoblock amplifier that was rated for just over 1,000 watts. It produced 934 watts at 1% THD+N when fed with 13.6 volts. Current consumption was 119.4 amps for a calculated efficiency of only 57.6%. Look at the Rockford specs. The M5-1000X1 made 50 more watts while drawing 20 amps less current.

In short, it’s easy to say that the last amplifier in this example is indeed quite power-hungry. So, where does the extra power go? That energy is converted into heat. The efficiency was so bad that the amplifier shut itself down because of thermal overload after running for only two minutes at full power when connected to a 1-ohm load.

Here’s another way to think about amplifier efficiency. The power going into the amp is either output to the load or is wasted as heat. In our two examples of good amplifiers, the Rockford Fosgate amp would need to dissipate about 380 watts of energy as heat. The ARC Audio amp is in the same ballpark with 420 watts of heat. Our unfortunately power-hungry amp is wasting 687 watts as heat. It’s no wonder it overheated so quickly.

Too Long; Didn’t Read: Can Car Audio Amplifiers Be Power Hungry?

The answer is an unequivocal yes. Sadly, the companies that don’t publish efficiency specifications are often some of the worst offenders. If your amp runs hot, it’s wasting power. It if overheats when played loudly, it’s wasting a LOT of energy. Every amplifier will get warm, but if you can’t leave your hand on it, then there may be better options available. Drop by your local specialty mobile enhancement retailer today to find a high-quality amp like the Rockford Fosgate and ARC Audio solutions we mentioned in this article.

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.

Every so often, someone asks if it’s a good idea to upgrade their factory-installed stereo system by swapping out the original subwoofer with a new one. We aren’t talking about building a new enclosure and adding a dedicated amplifier. They want to put a different 6-, 8- or 10-inch in the factory location and connect it to the OE amplifier. The answer to whether or not this is a good idea depends on a lot of variables. Let’s dive in and analyze this in more detail.

Potential Issue One: Speaker Impedance

Many factory-installed subwoofers have non-standard impedances. The driver may have dual 1-ohm coils or a single half-ohm winding. Thankfully, there are hundreds of different subwoofers on the market. If your installer has the tools to check the original sub, a solution with the same impedance might be an option. One caveat is that if you’ve damaged the woofer and need a replacement, measuring the impedance might not be an option. You can’t guess at this, and online resources like Mitchell1 ProDemand don’t typically include specifications for the woofer impedance.

Potential Issue Two: Subwoofer Dimensions

There’s always the question of “Will it fit?” Most aftermarket subwoofers are physically deeper than their factory-installed counterparts. This extra depth often results from a large magnet assembly and deeper baskets that allow for increased excursion. If there’s a solution with the right impedance and there’s enough depth in the enclosure, then your installer can move on to issues three and four.

Potential Issue Three: Enclosure Design Parameters

For some unknown reason, many original equipment subwoofers are installed in small sealed enclosures. Perhaps the reduced physical size of the enclosure helps to save weight in the vehicle – a crucial consideration for vehicle manufacturers. A vented enclosure would offer better efficiency and more extension. Nevertheless, the enclosures are what they are. If you plan to replace the speaker used in the enclosure, your installer needs to calculate the volume or design of the enclosure and verify that the proposed replacement will work in that space.

Potential Issue Four: Frequency Response and Efficiency

Though a bit of a generalization, most aftermarket subwoofers are designed to provide good low-frequency extension and do so by sacrificing some upper-bass output or overall efficiency. Suppose your installer were to find a woofer of the correct impedance that would fit and work with the provided enclosure. In that case, there’s the risk that the output characteristics of the new driver may not blend with the rest of the speakers in the audio system. Sure, you might increase your output by a few decibels at 40 or 45 Hz, but the system might have a dip in the response at 70 or 80 Hz where it blends with the speakers reproducing midbass frequencies. It’s far more likely that an aftermarket woofer will be less efficient and will need a dedicated amplifier to reach the same output level. You’ll get more deep bass, but you’ll need more power.

How To Upgrade an Audio System with a Factory-installed Subwoofer

If you want to be guaranteed that the money you’ll invest will be worthwhile, then you need to include an amplifier and preferably some sort of equalization solution with your upgraded subwoofer. Assuming the sub you have in mind will fit and perform well in the enclosure, the new amplifier will let your installer adjust the bass level to suit your listening preferences. The equalizer for the subwoofer can then be used to compensate for frequency response in the audio signal produced by the factory amplifier or variations in output from the new driver you’ve chosen.

It may be simpler to use a different enclosure. The odds are good that the optimized design of a vented enclosure of the correct volume and tuning frequency will result in much deeper and more accurate bass production.

Drop by your local specialty mobile enhancement retailer today to find out how you can upgrade the subwoofer in your car, truck or SUV. If space is at a premium, they may be able to use a factory-installed subwoofer enclosure or construct a new enclosure that fits into the same space.

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.

In the car audio world, terms like subwoofer box rise and power compression are relatively familiar to those who push their sound systems to the limit. So, after extensive research (three minutes) and a detailed planning session (another two minutes), we decided that it would be worth doing an experiment to explain and quantify these elements.

Let’s Talk About Speaker and Subwoofer Efficiency

If you’ve read the technical articles on BestCarAudio.com, you know that speakers of all shapes and sizes are notoriously inefficient. At the highest levels, maybe 2% of the power coming from your amplifier is converted into sound. The rest of that power is wasted as heat. For a high-performance 6.5-inch midrange/midbass speaker, efficiency is around 0.33%. For a 12-inch subwoofer of the same caliber, 0.27% isn’t abnormal. Enthusiasts often misunderstand that a massive subwoofer with a heavy cone, stiff suspension and a large-diameter four-layer voice coil is often less efficient. Efficiency numbers of 0.15% or less are common for some of these big, beastly subs.

Where we see the best efficiency specifications from speakers are in those designed for concerts. The so-called Pro Sound drivers trade low-frequency output capabilities for increased output at higher frequencies. Most 6.5-inch woofers are designed to play down to 75 or 80 Hz without issue in car audio systems. However, drivers designed for concerts typically have 50% to 25% of the cone excursion capability and a higher resonant frequency, so they can only play down to 150 to 200 Hz. The trade-off is an increase in output of 6 dB or more with the same amount of power. Using speakers like this in a car audio system can be tricky as you’ll still need a driver to cover the midbass range from 80 to 200 Hz.

Resistance Is Futile

Every electronic component or piece of wire has some amount of resistance. These resistances can be very small, measuring in the decimal milli-ohm range for a yard of power wire. For example, the voice coil on a speaker or subwoofer might be wound from wire as large as 18 gauge. For tweeters, the wire can be as small as 46 gauge.

The speaker’s impedance is determined by the size of the wire, the material it’s made from (copper, aluminum or copper-clad aluminum) and the length of the wire. To reach a target impedance of 4 ohms or similar, the engineer designing the coil assembly balances these characteristics along with the target mass for the completed assembly.

Let’s consider one last concept before we get into our discussion about power compression and box rise. As any conductor heats up, resistance increases. Pure copper has a temperature coefficient of +0.393% per degree Celsius. If a piece of wire measures 4 ohms at room temperature (20C/68F), it increases to 4.0393 ohms if the temperature rises 30C/86F. Aluminum has a temperature coefficient of +0.4309% per degree Celsius.

If 2 volts of signal is applied to a 4-ohm speaker, the amplifier delivers 2 watts of power. If the impedance of that speaker increases, the current from the amplifier decreases. If the impedance increases to 4.039 ohms because the coil is now at 30 degrees, the power dissipated in the speaker drops to 0.9903 watts with the same 2 volts applied.

Let’s Look at Power Compression

If you followed the math in the previous paragraph, you’ll quickly realize that heat is the enemy of a speaker. As the voice coil heats up, its resistance increases. As the resistance increases, the power the amplifier delivers to the speaker decreases. To maintain the same output level, you need to increase the power from the amp. The additional energy required to achieve the same output level results in more heat being generated in the voice coil. If you are good at recognizing patterns, you’ll already notice that we are in an endless loop that can quickly approach the thermal limits of the speaker.

Let’s Measure It!

We borrowed a Kicker L7 cone and spider assembly from Lee Mattason at Burlington Radioactive. First, we’ll use our Smith and Larson Woofer Tester 2 to measure the coil’s impedance. Then, we’ll start heating the coil assembly and take additional impedance measurements to see how the impedance changes.

The chart above shows the impedance of the voice coils of the Kicker L7 sub wired in series at different temperature points. At room temperature (17 degrees Celsius), the coil had an impedance of 3.975 ohms at 10 Hz. With the temperature of the coil at 107 degrees, the impedance had increased to 5.08 ohms. As a note, we could smell a faint whiff of the voice coil adhesive with the temperature at 120 degrees, so we didn’t increase it further. This sample needs to go back to the store and be put on display for consumers to see. Damaging it is not an option.

Let’s say we have a subwoofer amplifier rated to deliver the full 900 watts that this sub is rated for. When that amp produces that 900 watts into the 3.975-ohm load, it will be delivering 59.81 volts to the coil. It only takes a second or two for the coil to heat up well past our arbitrarily-chosen 107-degree mark at that power level.

We can now recalculate the power going to the sub with the voice coils at 107 degrees with 59.81 volts from the amplifier and the new impedance of 5.08 ohms. That works out to 704.18 watts. The sub’s output should decrease by 1.07 dB based on simple math, assuming the cone assembly was operating linearly. If you need the same level of output that was provided by 900 watts when the speaker was cold, you now need an amplifier capable of producing 1,151 watts. Then, the sub will get much hotter, much faster, and the impedance will increase even more.

Every single speaker on the planet behaves the same. The voice coil impedance increases as temperature increases. It doesn’t matter the brand, the size of the speaker or its design. Thankfully, small speakers like tweeters rarely see much more than a watt or two of power, so their fragile, tiny voice coils don’t heat up quickly.

A Good Reason to Choose High-Power Speakers

If you’re shopping for speakers for your car, truck, boat or SUV and plan to play them loudly, then choosing a solution with good power handling capabilities becomes as crucial as the sound quality of those speakers. On the other hand, if you are basshead to who competes in SPL competitions and you want to get the most power from your amplifiers so that your system can achieve the highest sound level numbers, then do everything you can to keep the subwoofers cool before your run. In either case, your local specialty mobile enhancement retailer can help you choose speakers, amplifiers and subwoofers that will deliver impressive performance and excellent reliability.

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 were cruising the internet a few weeks ago and noticed a comment from a self-proclaimed car audio expert that new speakers and subwoofers need to be broken in at low power levels. He made it particularly clear that the voice coil needed to be broken in gently. If you’ve ever considered how a speaker works from more than an “it makes sound” perspective or you have a grasp of basic electrical theory, then you’ll know that these are not accurate statements.

Speaker Components and Break-In

We aren’t going to beat around the bush on this one. The only part of a new speaker that will change from its brand-new-in-box condition after several hours of playtime is the spider. Many spiders are made from cotton or Nomex that’s impregnated with a phenolic resin. When new, the spider can be somewhat stiff compared to after it’s been played for a few hours. The short and sweet of this is, once the spider has been stretched a bit, it’s good to go. An hour or two of playtime at high volume levels is usually more than adequate to make it softer and more flexible.

The important question is, does the sound change before and after? Indeed it does – a bit. A subwoofer or midbass driver might play a little lower, and the total Q of the system should drop a bit once everything is broken in. For midbass drivers, the reduction in system Q might reduce some upper-bass resonance, so frequencies under 250 Hz might seem less distorted.

Breaking In Speaker Voice Coils

We have to apologize. We’re sitting here laughing to ourselves about the audiophile myths that speaker wire needs to be broken in or conditioned before critical listening can commence. Er, no. Wire is wire. It doesn’t rearrange its molecules when an audio signal passes unless, of course, you get the wire SO hot that it starts to glow. Sure, electrons jump between the copper (and aluminum and tin) molecules, but that doesn’t rearrange them.

The voice coil in your speakers is nothing more than a piece of wire (or maybe two) that is wrapped around a cylinder. The wire is attached to the speaker terminals with flexible conductors called tinsel leads. It’s wire. It’s just wire. Nothing more. You don’t need to condition it or break it in.

Comparing New and Broken-In Speakers

As we often do, let’s perform a little test. We borrowed a JL Audio 12W1v3-2 subwoofer from our friends at Burlington Radioactive. All of the subwoofers we have around here have several hours of use on them. We’ll measure the Thiele-Small parameters of the driver, then let it play for a few hours at a high excursion level to soften the suspension. We’ll measure it again once it’s cooled to see what, if anything, has changed.

As you can see from the above specs, the Cms specification, which describes the compliance of the driver suspension, is 108.48 micrometers per Newton. All the other small-signal analysis parameters (Fs, Qes, Qms, Qts and Vas) include the Cms value in their calculations. If this parameter changes, then the rest will change. Let’s see what happens after 4 hours of exercising the woofer with a 27 Hz sine wave at 10 volts into a 2-ohm load.

After eight hours of playing on our bench and another hour to cool off, we repeated the Small-Signal Thiele-Small parameter measurements using our Smith and Larson Woofer Test 2. The Cms compliance specification has increased to 142.57 micrometers per Newton. That’s an increase of just over 31%. Likewise, the Vas specification rose from 42.15 to 55.35 liters. This clearly indicates that the suspension is now softer, or more accurately, more compliant. However, as each driver specification works in conjunction with many other parameters, it doesn’t mean performance will change by 31%. So, let’s model the two sets of parameters in BassBox Pro.

And voila – our hypothesis came true. On this woofer, breaking it in for eight or so hours resulted in an increase in output of just about 1 dB at 30 Hz. That’s not significant. We like that the system Q dropped from 0.707 to 0.69, but again, that’s not something to write home about. Likely, you’d never notice these changes.

The performance benefits of breaking in a subwoofer depend on the design and materials used in the suspension. This JL Audio W1v3 woofer didn’t change much, which means you are pretty much good to go as soon as you buy it. However, some speakers change more after several hours of playtime – we’ve heard it many times.

What You Need to Know About a New Audio System

If you’ve had a new audio system installed in your car or truck and there is no plan to calibrate it with an equalizer or digital signal processor, then get in the car and enjoy it. Play it as loudly as you want. Oh, and please don’t adjust the amplifier settings.

If you have a system installed that will be equalized, then there are some considerations in terms of speaker break-in. Many shops will calibrate the system with their real-time audio analyzer to match a target curve once the installation is complete. They may suggest enjoying the system for a few weeks or months, then returning to the shop so they can give it a quick tweak to address anything you might like changed. Many people like different amounts of bass or highs, so a little fine-tuning is normal. Many shops use a target response curve that includes a lot of midbass boost. Most people realize that this unnatural balance makes male voices sound exaggerated. It might be fun for listening to drums or a bass guitar, but it’s not natural. Nevertheless, a few equalizer tweaks after 20 or 30 hours of playtime is common.

Do You Need a Special Process to Break Your Car Audio Speakers In?

Do you need to break in your new speakers or subwoofers? No. You don’t. They work just fine out of the box and will handle all the power they are rated for. Actually, the stiffer spider means the woofer will move less for a given amount of power from your amplifier. If cone excursion might be an issue, it’s more likely to show up after the woofer has been exercised for a while.

Drop by your local specialty mobile enhancement retailer today to find out what speaker and subwoofer upgrades are available to make your car audio system sound amazing! And don’t fret about breaking everything in – just enjoy!

Image Credit: Thanks to Dave from Andre’s Electronic Experts in Kamloops, British Columbia, for the lead-in and voice coil images.

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.

Decades ago, car audio professionals were adamant about the statement that tweeters needed to be installed right beside the midrange speakers in your car audio system. Is this accurate? The answer is that it depends on a few variables. Keeping them close can’t hurt, but it might come at the expense of improving the soundstage location in your audio system.

Why Did Tweeters Need To Be Installed Beside Midrange Speakers?

Decades ago, almost everyone used passive crossover networks to divide the audio signals from the source unit or amplifier in car audio systems between the tweeter and midrange drivers. Passive crossover design is much more complex than most people understand. The values of the components need to be altered based on proximity, distance and even the direction the midrange and tweeters are facing.

Most crossover networks were designed to provide a smooth transition from the woofer to the tweeter when both are installed beside the other on the same plane. Imagine what you see in a car audio display at your local specialist retailer as this reference. The reality is, this isn’t how many of these systems are installed in a vehicle. A few companies caught on to this and designed their networks to deliver smooth response in typical installation situations.

Back in 2005, our friends at Of Sound Mind Labs were reviewing a set of car audio speakers for a car audio magazine. As part of the process, they took frequency response measurements with the tweeter mounted on the same plane as the 6.5-inch woofer from the set.

The large dips around 1,000 and 5,500 hertz certainly aren’t ideal. Worse, boosting around 5.5 kHz with an equalizer will dramatically increase the work the tweeter needs to do and could cause damage at high volume levels.

After a discussing the measurements with the engineering team that designed the speaker set, it was revealed that the intended application was for the listener to be about 45 degrees off-axis to the midrange, and the tweeter was to be angled toward the listening position and installed beside the midrange using the included surface-mounting installation kit. The reviewer added the tweeter mount and measured the system off-axis as described.

As you can clearly see, the response is now amazingly flat through the 1 kHz and 5 kHz ranges. There was no equalization applied – the crossovers were optimized to deliver a smooth response in configuration. Frustratingly, this information wasn’t in the owner’s manual.

Adjustable Passive Crossover Networks

Over the years, a few companies have offered adjustable passive crossover networks. The intent was to allow your technician to fine-tune each speaker’s output around the crossover frequency for different installation locations. Alpine and Focal were good examples of this crossover-configured flexibility. This solution wasn’t perfect but was much better than not having any adjustment at all.

Modern Audio Installations

In the last few years, car audio digital signal processors have become popular and much more affordable. Aside from equalizing each speaker’s output in the audio system, a significant benefit of a DSP is that your installer can adjust the crossover points and apply signal delay to each speaker to ensure that the output of each arrives at the listening position in-phase. What does all this gobbledygook mean? Your tweeters don’t have to be installed right beside the midrange speaker, so long as the technician working on your car or truck knows how to use the DSP features to produce a smooth response in the vehicle.

Let the Experts Design and Install Your Car Stereo System

More often than not, information about the proper application of passive crossover networks is only shared with authorized retailers. The staff at these facilities invests a significant amount of time and money in attending manufacturer and industry training events in order to glean this sort of information and deliver the best possible solutions for clients. Likewise, the training offered by DSP manufacturers allows experienced retailers to configure and calibrate your audio system efficiently and accurately.

Too Long; Didn’t Read – Do Tweeters Need To Be Installed Near Midrange Speakers?

The short and sweet answer to the question about installing tweeters near midrange speakers in a car audio system is that it depends on the crossovers. The improvement in stage height afforded by having the tweeters in the sail panels or A-pillars instead of low in the doors is just one small reason modern car audio systems should be designed and calibrated with a digital signal processor. Drop by your local specialty mobile enhancement retailer today and audition one of their demo vehicles. Based on your feedback about what you hear and enjoy, they can design an audio system that will deliver the performance you want in your car or truck.

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.