Not too long ago, we stumbled across a discussion about the need for large-gauge car audio speaker wire to be connected to a high-power amplifier. The comments on the post were prime examples of how little some audio enthusiasts understand about the signals going to the speakers in their car audio system. So, to help as many people as possible understand the subject, we put together this article to explain why you don’t need 12-AWG wire for your tweeters.

Audio Signals – Amplitude and Frequency

The amount of voltage produced by your amplifier is dependent on the volume setting and the frequency content of the audio signal. Suppose you’re listening to a recording of an electric guitar. In that case, your amplifier will produce significantly less power than it would take to reproduce the lowest notes of a synthesizer or bass, even at the same perceived volume level.

Why do higher frequencies need less power to reproduce? Most of the sounds we hear follow the same approximate shape as pink noise. If you analyze the energy in a pink noise waveform, you’ll see that its amplitude attenuates at a rate of -3 dB per octave or -10 dB per decade as frequency increases.

If you have a typical car audio system, then you may have a subwoofer or two to handle reproducing audio frequencies below 80 Hz, midrange drivers to handle the sounds from 80 to 3,500 Hz and tweeters for those frequencies above 3,500 Hz. The graph below shows the energy fed to the subwoofers, midrange drivers and tweeters using these crossover points.

It’s clear to see that the tweeters are receiving a lot less energy than the midrange drivers in the doors. In fact, it’s about 20 dB less at the highest level. If you had 100 watts going to the door speakers, your tweeters would only need 1 watt of power to keep up. In this example, the average amplitude of the signal going to the mids compared to the tweeters is 13.9 dB louder. So, you need about 4.1 watts for those tweeters if the mids are getting 100 watts. With nearly 5 dB more output required, the subwoofers would need 316 watts, assuming they had the same efficiency as the midrange speakers.

Power in Alternating Current Signals

A commenter in that thread wrote, “Yeah, but it’s AC, not DC,” as if to imply that an AC signal wouldn’t deliver as much current to the speaker. For pure sine waves, this with where the Root Mean Square (RMS) value comes in. An AC sine wave of, say, 10 volts RMS can do the same amount of work as 10 volts DC.

Music isn’t a single constant sinusoidal waveform. It varies in amplitude and frequency. As such, we need to look at an average level. To keep our example simple, let’s use 300 watts, 100 watts and 4 watts for the math involved in calculating how much power is lost due to the resistance of speaker cabling. We’ll also maintain the simplicity of the example by assuming all the speakers in the system have a nominal impedance of 4 ohms.

Current in Car Audio Speaker Wire

For our example, our 300-, 100- and 4-watt power levels translate to 8.66, 5 and 1 amp of current flowing through the respective speakers. Let’s use a piece of 12-AWG speaker wire with a length of 10 feet for our benchmark. If the speaker wire is full AWG spec and is made from pure copper, the 10-foot length will have a total resistance of about 36.3 milliohms. The voltage drop in the wire will be 0.314, 0.181 and 0.026 volts which, if my math is correct, represents a reduction in output of 0.157, 0.091 and 0.018 dB, respectively. In short, these differences aren’t going to be audible at anything other than when the volume is turned up all the way. At even one notch down, those reductions diminish significantly. With the dynamic characteristics of music, it’s safe to assume the average required power is 1/10 of the maximum.

What happens if we run 14- or 18-AWG wire instead of 12-AWG? The chart below shows the reduction in output at the most extreme cases with test tones being played. For your tweeters, it just doesn’t matter. For the mids, at full power, maybe there is a minute loss that might affect the balance of the system. Should you use 18-AWG speaker wire with your subwoofer? Probably not.

What happens at normal listening levels? Say you are commuting to work and the radio is on so you can hear traffic and news with the odd song thrown into the mix. With the typical midrange driver having an efficiency of 86-88 dB at 1W/1M, you are likely to be averaging a lot less than 1 watt of power to the doors. For argument’s sake, let’s say you are. To maintain the same relative output levels, the sub would be getting 3 watts and the tweeters are at 40 milliwatts. Our losses in the speaker wire drop to imperceptible levels of 0.063 dB on the woofers, 0.036 dB on the mids and 0.003 dB on the tweeters. Still worried about speaker wire size?

Let’s Look at More Subwoofer Math

Car audio companies seem to like to design car audio subwoofer amplifiers that produce their maximum power into low impedances. We’ve already looked at the sacrifices in amplifier efficiency and increases in distortion at low impedances in another article.

In short, for the same power delivery to the subwoofers, lower load impedances require more current to flow through a speaker’s voice coil. More current means more energy is wasted in the speaker wire due to its resistance. Let’s cook up another example – 750 watts into 4-, 2- and 1-ohm loads with 12-, 14- and 18-AWG speaker wire. Here are the results:

As you can see, this is yet another good reason to avoid amplifiers that require low load impedances to produce large amounts of power. OK, 750 watts through an 18-AWG conductor that’s 10 feet long is a pretty extreme example, but it punctuates the point pretty clearly.

In reality, you will never deliver full power to all the speakers in your car, save for maybe the subwoofer if you compete in SPL contents. In those cases, where tenths or maybe even hundredths of a decibel matter, having oversized speaker wire and amplifier power cable is impossible. Knock yourself out and have your installer run eight-AWG power cables to the subs! For the rest of us who listen to music at even modestly reasonable power levels, 14-AWG speaker wire is well more than adequate, and your tweeters don’t need anything over 18-AWG. Drop by your local specialty mobile enhancement retailer to find out about the audio upgrades that are available for your car or truck. Spend the money you’ll save on not buying monstrous speaker wire for your tweeters and midrange drivers on better speakers.
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.

Car audio sound deadening has been a popular upgrade to improve the comfort of your vehicle and enhance audio system performance since the early ’90s. The original concept of sound deadening was to make cars and trucks quieter and more comfortable by limiting the ability for noise outside the vehicle to get into the cabin. Car audio enthusiasts realized that having their vehicles deadened would dramatically improve the efficiency and performance of their audio upgrades. Today, dozens of companies offer noise control solutions. With that said, they aren’t all created equally. This guide will help you choose the best solution for your vehicle.

How Does Car Audio Sound Deadening Work?

Noise sources such as an exhaust system, the mesh of gears in a transmission or the vibrations of your tires rolling down the road produce sound energy that vibrates the metal panel on the body and chassis of your vehicle. As these panels vibrate back and forth, that sound energy is transferred into the interior of your car or truck. The effect isn’t as significant as having a window rolled down, but this unwanted noise and vibration are clearly audible.

One of the key differences between an entry-level vehicle and something more luxurious is the background noise level in the cabin as you drive. Companies such as Rolls Royce may add more than 200 pounds of noise control materials to their most luxurious vehicles. Along with thicker glass, plusher carpets and even wheels and tires with noise-absorbing technologies, reducing noise in vehicles is big business.

Automotive sound deadening or damping products add mass to metal and plastic panels to reduce the amount they vibrate. Energy from the sound source is converted into microscopic amounts of heat rather than being passed through the panel and into the vehicle interior. High-quality sound deadening products have a second function. Most doors, rear parcel shelves and the rear side panels in coupes have large openings. Some of these exist to allow for the installation of power windows and locks. These large openings do nothing to block sound from entering the cabin. As such, sound deadening products can be used to span these spaces and dramatically reduce noise inside the vehicle.

Sound Deadening Materials

When noise control products originally entered the car audio industry, they were partially petroleum-based and carried a unique and distinct odor. While the damping characteristics were good, long-term adhesion was mediocre, and many consumers complained about the smell. Most of the current high-quality deadening solutions use a butyl base layer with varying thicknesses of aluminum to balance absorption and rigidity characteristics. These are called constrained-layer damping (CLD) solutions.

The characteristics of the material have to be balanced in their design to absorb energy (soft and gooey works well here) while having the rigidity to span openings and reduce noise transfer (firm and dense). Many products branded as car audio solutions come from other markets and fall at the extreme ends of this balance. As such, they don’t provide the best overall solution compared to those engineered specifically for car audio applications. In short, what might offer the most ideal damping when affixed to a flat metal panel might be the worst for bridging open spans in your doors or the rear deck of your car.

When shopping, ask to see a sample of the product. If you hold a piece of deadening horizontally and it falls limp, it’s too soft. Conversely, if it’s stiff like cardboard, it might not conform well or stay adhered the to complex shapes and surfaces in the vehicle.

Many CLD solutions add a third layer of closed-cell foam on top of the aluminum to reduce noise from wire harnesses, trim panels and door release and lock actuator rods while the vehicle moves down the road.

You’ll want to choose a product that’s primarily black where it might be seen through a speaker grille. The last thing you want is a shiny silver or gray finish attracting attention where it’s not required.

Another class of aftermarket noise control product is mass-loaded barriers. These products are typically a sandwich of closed-cell foam over a lead-like alloy sheet. The dense layer in the center acts as a second barrier to noise and offers impressive energy absorption properties. These products are ideal for installation on the floor and trunk or cargo area of vehicles, and they serve as an excellent replacement for carpet pads.

Adhesive Properties of Sound Deadening

Aside from balancing noise control properties, it’s important to pick a sound deadening solution with excellent adhesion properties. The last thing you want is for the damping material to release from the inside metal on a car door and get stuck against the window.

The deadening needs to stay in place in extreme cold temperatures below -40° C or F to scorching conditions well above 140° F/60° C. If the material breaks down and falls off of vertical surfaces, the mess can be extremely expensive to clean up, and upholstery or interior components such as carpet, door panels or roof liners may need to be replaced.

Safety Considerations

Anytime you’re adding something to your vehicle, safety should always be a priority. Automotive engineers agonize over what would happen in a worst-case scenario to ensure that the occupants remain safe. In the event of a catastrophic accident or serious malfunction, that last thing you want is for something that’s been added to your vehicle to burn quickly. The Federal Motor Vehicle Safety Standard Number 302 is a test designed specifically to evaluate the flammability of automotive materials. Flame propagation from an ignition point must not exceed 102 mm per minute. Ideally, the material will self-extinguish. Likewise, the Underwriters Laboratory UL 94 flammability test for plastics requires that plastics stop burning within three seconds, with an afterglow of less than 30 seconds. The UL 94 standard would apply to foam products in the context of this discussion.

Installation Options for Maximum Noise Reduction

It would be great if sound deadening could be applied to every square inch of a vehicle during the manufacturing process. For hot rod and restoration projects, the installation of more than 100 square feet of sound deadening is commonplace before the wiring and interior are installed. For daily driver applications, many components will need to be removed from your car or truck to achieve the same results. Here are a few suggestions that offer excellent noise control improvement:

• Car doors are large, flat surfaces that allow significant amounts of noise into the vehicle. Having the rear of the outer door skin treated can offer significant benefits. Covering the inner door skin not only helps to reduce vehicle, road and wind noise from entering the vehicle, it can dramatically improve the performance of the speakers installed in the vehicle. In fact, if the inner door panel has access holes in it, having it treated with sound deadening will improve audio quality for less money than a speaker upgrade.

• Floors and cargo areas are another source of significant noise transfer. If you’re going to have the floors done, be sure the installation extends up the front firewall as far as possible to help reduce the transfer of sound from the engine and transmission. Having the wheel wells treated can dramatically reduce noise, especially when it’s raining. The sound of water spraying against a metal wheel well is surprisingly loud.

• The roof and trunk lid are even larger than your doors and can transfer a surprising amount of sound into the vehicle interior. If you’re going to have these surfaces deadened, make absolutely sure the product you’ve chosen has excellent adhesion and thermal properties. You don’t want any peeling issues here.

Benefits of Automotive Sound Deadening

Aside from making your vehicle quieter while you drive, the reduced background noise improves outgoing call quality when using a hands-free Bluetooth system. Likewise, voice recognition technologies such as Android Auto and Apple CarPlay work better when the vehicle is quieter.

In terms of audio system performance, sealing openings in a car door can increase the bass and midbass performance of a speaker by more than 10 dB. That’s like having an amplifier that’s 10 times as powerful! Having the trunk or cargo area of your car treated can help with the performance of a high-power subwoofer system by reducing the energy lost to vibrating panels. Deadening solutions that include foam reduce the buzzing noise of wire harnesses or the sound of interior trim panels rubbing against the metal car components they are attached to.

Upgrading your vehicle with car audio sound deadening is an amazing investment. If you’re interested in improving the comfort of your vehicle, drop by your local specialty mobile enhancement retailer and ask them about adding sound deadening to your car, truck or SUV.

When it comes to producing deep bass from a small enclosure, adding a passive radiator offers some significant performance benefits. If you aren’t familiar with this type of subwoofer enclosure, then you’ve come to the right place. We’ll look at how this design works, the benefits it offers and analyze potential drawbacks. Ready? Let’s dive in!

Common Subwoofer Enclosures

Traditionally, there are two popular types of subwoofer enclosures. The simplest to design and execute properly is an acoustic suspension design, better known as a sealed enclosure. In this configuration, the air inside the enclosure adds to the compliance of the cone assembly to control its motion at low frequencies. When designed with a low-to-modest system Q value (Qtc <0.75, for example), the roll-off response is typically in the 40-55 Hz range at a slope of -12 dB per octave.

The second type of enclosure you often see is called a bass reflex design. These are also known as ported or vented enclosures. In these designs, a vent is added to the enclosure that lowers the system’s resonant frequency. The vent has a specific surface area and length in order to change the resonant frequency of the system. As a gross generalization, bass reflex enclosures are 50% larger than their acoustic suspension brethren but offer extended low-frequency output. In car audio applications, this extended response improves overall system efficiency. The design of the vent is somewhat complicated in terms of balancing surface area and implementing an appropriate radius on the ends to prevent unwanted noise from high-velocity air movement. Below the tuning frequency, the output of this type of subwoofer enclosure design rolls off at -24 dB/octave.

Passive Radiator Subwoofer Enclosure Designs

Imagine if there were a way to get the efficiency of a bass reflex design with the enclosure volume of an acoustic suspension enclosure. The passive radiator is a nearly ideal solution. Imagine that a passive radiator is a subwoofer in which the voice coil and magnet assembly have been removed. A precise amount of weight must be added to the remaining assembly to produce a very low resonant frequency. The weight of the passive radiator cone assembly is roughly equivalent to the air mass that would fill the vent in a bass reflex design.

Let’s Model Some Subwoofer Enclosures

As they say, the best way to visualize something is through comparison. For this example, we will simulate the performance of a Rockford Fosgate Power Series T1D210 10-inch subwoofer in acoustic suspension, bass reflex and passive radiator enclosure designs.

Let’s start with the sealed enclosure design. For a good blend of low-frequency extension and cone control, we’ll target a system Q of 0.707. The software suggests that a net internal air volume of 0.53 cubic foot is ideal. This results in a system F3 of 51.06 Hz, which is typical and acceptable for this type of subwoofer enclosure.

Next, let’s look at extending the low-frequency efficiency of our sub by moving to a bass reflex enclosure design. We’ll double the enclosure volume to a net of 1.06 cubic feet and add a vent that’s tuned to 29 Hz. The vent in this example is tricky. Ideally, it should have a diameter of 4 inches, but the length would be 36 inches and difficult to fit inside the enclosure. We aren’t talking about the difficulty of constructing the enclosure in this article, so we’ll leave that in place for the simulation. The F3 frequency is a thoroughly enjoyable 26.1 Hz.

Last and certainly not least, let’s look at the passive radiator enclosure design. For this simulation, we’ll use a 10-inch radiator with a resonant frequency of 15 Hz, equivalent compliance of 60 liters and a Qms of 4.5. We’ll keep the enclosure volume at 0.53 cubic foot.

As you can see in the graph below, we pick up a tiny bit of efficiency above 55 Hz compared to the bass reflex enclosure. Our passive radiator design is much louder at all frequencies above 25 Hz compared to the acoustic suspension system. This design yields an F3 frequency of 35.6 Hz.

Advantages and Drawbacks of Passive Radiator Designs

A second benefit of the passive radiator (P-R) design is that there is no chance of noise from the radiator as compared to a vent. A vent with a small area may produce chuffing noises as the air resonates up and down through the column. Likewise, a hard edge on the inner and outer edges of a vent contributes to the chance of unwanted noise. The passive radiator moves forward and rearward like the subwoofer itself.

On the flip side, the roll-off of the P-R system is steeper than both the acoustic suspension and bass reflex designs at -30 dB/octave. This is because there is a null in the output where the radiator resonates. If we expand the vertical scale on our simulations in BassBox Pro, we can see this dip at 15 Hz. In short, a P-R design isn’t as good as at reproducing infrasonic information as a bass reflex or acoustic suspension system. Whether this response dip matters or not depends on your expectations and the music you listen to. If you like rock, pop and rap music, it likely won’t matter at all. If you listen to classical music with lots of low-frequency organ notes, it might not be ideal.

Companies like Audiomobile, Kicker and Earthquake offer passive radiators that specialty car audio retailers can use to increase the efficiency of your car audio system. They don’t have to be used with the same brand of a subwoofer, so mixing and matching might offer a great opportunity. Some of these companies offer very specific designs for their solutions, while others provide more information to allow your technician to create something special and unique. If space for bass in your car or truck is at a premium, having a passive radiator subwoofer enclosure built might be a great solution.

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.

When it comes to car audio systems, more is better, right? Enthusiasts want more bass, more output and more impact. When your favorite song comes on, turning the volume knob all the way up seems like the right thing to do. For car audio professionals, we need to balance keeping our clients happy with great-sounding audio that will play loudly and ensuring that the equipment we’ve installed functions reliably. Yes, you can turn up the gains on amplifier and it might play a little louder, but that might create a lot of distortion that results in damaged speakers and subwoofers.

A Primer in Over-Driving Car Audio Amplifiers

Every car audio amplifier on the market, save for those classics with built-in limiters, has the ability to produce significantly more power than it is rated for. The issue is, this extra power is riddled with massive levels of distortion that renders the signal unusable. Allow us to explain.

If you’re playing a sine wave through an amplifier and you increase the output level so that the peaks are just below the level at which the amp clips, lets assume you get the full rated power of the amplifier. In this theoretical example, let’s say that’s 72 watts. The output waveform might look something like what’s shown below.

If you increase the signal going into the amp, or turn up the sensitivity (gain) control, the amp will attempt to amplify the signal more. The issue is, there’s always a limit to how much power the amp can produce. That limit is determined by the amplifier rail voltage or the power supply’s ability to deliver current to the load. Let’s say we increase the gain a little bit so that we can play really quiet music loudly. When we play loud music, the output might look like the orange trace in the image below.

It’s important to know that the amplifier is producing more power when it starts to distort. Power is the area under the curve, to put it simply. The speaker may not play significantly louder as this extra power is delivered as harmonic content rather than more output at the fundamental frequency.

In a theoretically perfect amplifier, you can drive the outputs to a point that it produces twice its rated clean voltage. The waveform would look something like the red trace shown below.

How To Calculate Amplifier Power

When calculating power in a sine wave, we use the 0.707 of the peak value as the average voltage, or more accurately, the RMS voltage. The RMS level is the alternating current (AC) signal level that does the same amount of work as a direct current (DC) amplitude. For the green trace, this would be 0.707 x 24, which is 16.968 volts. To calculate power, you square the voltage and divide by the load impedance. For our simulation, that’s (16.968 x 16.968) ÷ 4, which works out to 72 watts.

A square wave, like the one shown in red, doesn’t use this 0.707 multiplier. The peak voltage of 24 volts is used without any scaling. When plugged into the power equation, we get (24 x 24) ÷ 4, which is 144 watts. Unsurprisingly, that’s twice as much as 72.

If we had a speaker with a real thermal maximum power handling of 75 watts connected to this amplifier, and we fed it with 144 watts of power, it would fail. This is why seemingly under-rated amplifiers are capable of damaging speakers. Amplifiers can and will produce more power when pushed to clipping.

As full transparency, modern Class-D amplifiers can’t fully double their power output capabilities. They are more likely to be able to produce 100 or 120 watts in a similar scenario. That’s still well more than our 75-watt speaker can handle.

The Purpose of Amplifier Gain Controls

The gain control on your car audio amplifier exists for two reasons: to allow it to produce its rated power when fed with a variety of source unit voltages, and second, to allow the installer working on your audio system to balance the output of multiple speakers in an actively filtered audio system.

If you have one pair of amplifier channels for your door speakers and another channel for a subwoofer, the relative level between the two needs to be adjusted so that the system sounds good. Many shops will use a standard target curve to which they calibrate the audio systems they install.

It’s clear to see from the above that you don’t need as much power for the midrange speakers as you might for the subwoofer.

Considering Sensitivity Controls and Equalization Settings

Let’s look at another important aspect of setting up amplifiers. In our example, we have a 72-watt amp that’s going to power a set of two-way component speakers in the front doors of a car. As happens in every automotive installation, there are frequencies that need to be attenuated with an equalizer in order for the audio system to hit the target. Let’s say that we needed to pull out 3 dB of output around 1 kHz, boost 400 Hz by 5 dB and cut 100 Hz by 6 dB. The response curve of our equalizer would look like the image below.

Many amateurs will pick a specific frequency at which to set the gains on the amplifier running the midrange speakers. While this process ignores the target curve, it can also run afoul of equalization settings. Let’s say someone chose 1 kHz in our theoretical system to set the midrange amp. Look at our EQ response curve. We’ve reduced 1 kHz by 3 dB relative to the rest of the signal. We’ve also boosted 400 Hz by 5 dB. If the amp is set to clip with the volume control at maximum using a 1 kHz test tone, frequencies around 400 Hz will be significantly distorted. In fact, to reach our output requirements at 400 Hz, we need around six times as much power as is required at 1 kHz. Imagine how much distortion would be added!

What’s Wrong with Having Too Much Gain on Your Car Audio Amp?

If the gain controls are turned up too much, a significant amount of unwanted hiss may be added to your audio system. Worse, if you don’t know what to listen for in terms of clipping or distortion, you can easily send too much power to your speakers or subwoofers and damage them. Balancing all the criteria we’ve talked about while ensuring that you can get the cleanest output from your stereo isn’t as easy at it would seem.

Before you start experimenting with oscilloscopes, distortion detectors and voltage charts, talk to a local specialty mobile enhancement retailer and consider having them set up your system so that it sounds great.

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.

Did you know that a difference of 20 watts of power between one car audio amplifier and another might be completely inaudible? That same 20-watt difference might mean having to keep your windows rolled up on the highway to hear your music. Let’s look at the physics of reproducing sound with moving-coil loudspeakers and why choosing an amplifier with a few watts more than another may be significant or irrelevant.

Car Audio Speakers and Amplifier Power

If you look at a typical higher-end 6.5-inch coaxial car audio speaker, you’ll find that it has an efficiency rating of 86 dB when driven with 1 watt of power and measured at a distance of 1 meter. If the reference is 2.83 V, then that’s 2 watts into a 4-ohm driver, and the efficiency number will be 3 dB higher at 89 dB. If it’s a 2-ohm driver with a 2.83V spec, then that’s 4 watts, and they will add another 3 dB. Aren’t specification games fun?

The first takeaway from this is that it takes a doubling of your amplifier’s power to increase a speaker’s output by 3 dB. At the same time, halving the power reduces the output by the same 3 dB. If you only need 80 dB of output, then our 86 dB efficient speaker will only need 0.25 watt of power to reach that level.

Scenario 1 – Deck Power and Door Speakers

Suppose you have a modest audio system that is made up of a typical aftermarket radio and a pair of equally typical door speakers. Most radios can produce about 20 watts of output per channel, and we’ll use our 89 dB example speakers (though now we have two of them, so the pair will produce 92 dB when each is powered with 1 watt). With 20 watts of power on tap, the system should produce just a smidge over 104 dB of output. Of course, this assumes that the speakers increase the output linearly for every doubling of power. At 20 watts, especially if they are reproducing bass frequencies, you are likely near their upper limit.

What if we switch the radio to a high-power unit like the Sony XAV-AX7000 that can produce 45 watts of power per channel? Now, assuming the speakers can handle the extra power, the system will produce about 107.5 dB of output. That extra 25 watts increases how loudly our music will play by 3.5 decibels. It doesn’t sound like a lot, but it would be audible.

Scenario 2 – Small Subwoofer Amplifier Versus Large

In our second example, let’s look at the higher power levels involved with driving a subwoofer. Say we have a Rockford Fosgate amplifier capable of producing 1,000 watts of power. Considering the transfer function of the typical vehicle interior, a pair of 10-inch subwoofers in a vented enclosure might have an efficiency of about 101 dB at 40 Hz when each is driven with 1 watt. When we increase the power to the subs to 500 watts each, the system should produce 128 decibels of output. That’s pretty darned loud! Keeping in mind that we need to double or half the power level to produce a change of 3 dB, what happens when we pick an amplifier that can produce 1,050 watts or that same increase of 25 watts to each subwoofer? Well, the system will play 0.21 decibel louder. While you might be able to measure that with a Term-Lab SPL system, it’s unlikely you can hear that small of an increase.

Looking at Power Specifications Using Decibel-Watts

While most of us are used to seeing the decibel unit used in the context of measuring volume levels, it can be applied to a variety of electrical applications. If you take a close look at the power measurements in any of the BestCarAudio.com Test Drive Reviews, you’ll see we list watts and a number called dBW, or decibel-watts. The unit dBW refers to decibels referenced to one watt of power. As such, if the amp produced 1 watt of power, it would be rated at 0 dBW, or no increase or decrease relative to 1 watt. If it made 8 watts, then it would be rated at 9 dBW. One hundred watts is 20 dBW, and 1,000 watts is 30 dBW.

Suppose your speakers or subwoofers can handle the power in terms of thermal capacity and cone excursion capability. In that case, you can add the dBW number to the 1-watt efficiency number of the speaker to estimate how loudly it will play. Of course, no midrange speaker is going to able to deal with 200 watts of power, and a subwoofer isn’t going to increase its output linearly when driven with 10,000 watts.

Backtracking for a moment, to provide some clarity, when we use an RTA or SPL meter to measure a sound source’s volume level, we measure dB SPL. Similar to the way that the decibel watt (dBW) references 1 watt of power, the dB SPL unit references 20 micropascals or, 0 dB. A sound level of 20 micropascals is considered the lowest hearing threshold of a young, healthy ear. Of course, if we can measure this pressure (20 micropascals), then 0 dB isn’t absolute silence or a vacuum. It’s just a reference level. In the same way, 0.25 watt is -6 dBW; it’s possible to have negative SPL numbers or a room that’s quieter than 0 dB. Microsoft built an anechoic test chamber that has a noise level of -20.35 dB SPL, or 20.35 decibels quieter than 0 dB. It’s said that the sound that air particles create from bumping into one another in a still room is -23 dB SPL.

When Watts Matter and When They Don’t

Let’s take all this information and put it into use. If you’re shopping for a new radio, then one that produces 45 watts is going to provide an audible improvement over one that produces only 20 watts. If you are shopping for an amplifier for your speakers, a 75-watt and a 100-watt amp will only increase output by just over 1 dB. If one subwoofer amplifier produces 25 watts more than one that makes 750 watts, the difference is only 0.14 dB. The best way to think of amplifiers is by ranking them as small, medium and large. A small stand-alone speaker amplifier would be 50 watts per channel. A large one would be 100-125 watts. A small sub amp would be 250-300 watts, a medium would be 600-800 watts, and a large would be 1,200-2,500 watts. Worrying about whether the amp makes 1,150 or 1,175 watts (a difference of 0.09 dBW) is a waste of time.

When it’s time to upgrade your car audio system with a new high-power radio or an amplifier, drop by your local specialty mobile enhancement retailer and ask to audition several options on the same set of speakers or subwoofers and the same source unit. This is the best way to determine which solution offers the least distortion and most accurate sound. Just a reminder, don’t get hung up on a few watts – that’s truly the least of your worries.

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.