Speakers are, by a long way, the most influential component in any audio system when defining performance or quality. Low-quality speakers, or those without specific technologies, can’t match the clarity levels of premium solutions. In addition, many music enthusiasts want their car audio systems to play louder than what’s possible with factory-installed equipment. After all, jamming to your favorite music while going to work or school is a great way to start the day! Is upgrading the speakers the right solution? Let’s look at the physics of loudspeaker efficiency and output capability.

Car Audio Speaker Efficiency

One of the many reasons people ask to upgrade the speakers in their cars and trucks is a desire for the system to play louder. Unfortunately, most high-performance speakers aren’t as efficient as those that the manufacturer provided.

When shopping for speakers, you’ll need to look at the efficiency specification. This number describes the amount of sound a speaker will produce for a given signal from an amplifier. The standard specification describes the speaker’s output in dB SPL at 1 meter from the speaker when powered with 1 watt from an amplifier.

A second standard exists where 2.83 volts are applied to the speaker, and the output is measured at 1 meter. There is nothing wrong with the 2.83-volt rating, except that you have to consider the speaker’s impedance when comparing drivers. For example, a drive level of 2.83 volts equals 1 watt of power when driving an 8-ohm speaker, 2 watts when driving a 4-ohm speaker and 4 watts with a 2-ohm speaker.

The output of a speaker increases or decreases by 3 dB every time the power is doubled or halved. Therefore, be sure you’re comparing like numbers when comparing speaker efficiencies. If no drive level specification is provided, it’s safe to assume the manufacturer will choose the 2.83-volt measurement to produce the highest numbers.

Are New Car Audio Speakers Going To Be Louder?

A while back, we measured the output of a 6.5-inch speaker from a Honda Civic as part of our series on understanding speaker quality. Our measurements showed that this speaker had an efficiency of 89.04 dB SPL when driven with 1 watt of power and measured at a distance of 1 meter. So how does this number compare to common replacement speakers? First, let’s look at a few examples from Rockford Fosgate. I’ve chosen this brand as it has a variety of offerings and many price points and performance levels.

Starting with its most affordable option, the Prime Series R165X3 has a rated efficiency of 91 dB SPL at 1W/1M. You’d be able to hear this 2-dB increase in output. What if you want a better speaker? It seems logical to move up to one of the Punch Series drivers. The P1650 is a very popular replacement speaker, but it has an efficiency of 88 dB SPL at 1W/1M. Does this mean the speaker isn’t as good? No, it’s simply not as efficient. If you want an even better speaker, then the Power Series T1650 is the next step in the series. This driver also has an efficiency of 88 dB SPL at 1W/1M. So why are the better speakers not louder?

When a transducer engineer is designing speakers, they must balance many characteristics. How efficient will the driver be? How low should it play? How much power can it handle? How much excursion is required? Unfortunately, some of these characteristics oppose each other. A driver of a given size that is intended to play lower frequencies will need a lower resonant frequency. This lower Fs value is usually achieved by increasing the cone’s mass and softening the suspension. The increased mass of the cone assembly decreases the driver’s efficiency. An extreme example of this would be a 6.5-inch subwoofer. A typical 6.5-inch car audio subwoofer has an efficiency of around 80 to 81 dB at 1W/1M.

As you can see, the 6.5-inch midrange driver is much louder at higher frequencies. So, why not use it as a subwoofer? Well, it doesn’t have the power handling or excursion capabilities required to reproduce low-frequency audio and high volume levels. A typical full-range 6.5-inch driver might handle about 50 or 60 watts of power and have a maximum linear cone excursion of roughly 3 millimeters in each direction. An equivalently sized subwoofer might handle 150 watts of power and have 9 to 10 millimeters of excursion capability. Since we know that speakers need to move a lot more air to produce bass, it’s clear that the subwoofer would be louder at lower frequencies.

What About PA Speakers?

We have pro audio or PA speakers at the other end of the speaker spectrum. These drivers are designed for applications where the most output possible is required from minimal amounts of power. For example, let’s say you were responsible for setting up the sound system for a Metallica concert in an open-roof stadium. Many of these installations have about a megawatt of power driving the speakers and subwoofers. Assuming 220-volt, 30-amp circuits feed the amplifiers, the sound system would need more than 180 circuits. However, if you could find 3 dB more efficient speakers, you could get the same output for the audience from 90 circuits and half the amplifier power.

PA speakers use designs that trade low-frequency output for increased midrange output. For example, a 6.5-inch PA-style speaker might have an efficiency of 92 or 93 dB at 1W/1M. This would be achieved by lowering the mass of the cone assembly as much as possible. The trade-off would be output at lower frequencies. Unfortunately, many high-efficiency 6.5-inch speakers have an Xmax specification of only 1.5 to 2 millimeters. As a result, they sound horrific when used incorrectly and driven with midbass information in the 80-to-150-hertz range at high levels.

Unlike a car audio system, there’s no need to drive concert midrange drivers down to 80 Hz to help with the perception of bass frequencies sounding as if they’re coming from the front of the vehicle. Instead, the crossover point can be at 150 or 200 hertz, and the system will sound the same to the audience. If you look at the frequency response specification of a concert subwoofer, you’ll find that most are designed to play up to 200 hertz. You may also note that these subwoofers also call for a high-pass filter, or what car audio enthusiasts would call an infrasonic filter at 35 hertz.

As you can see from the graph above, the green trace shows that the speaker is much more efficient in the upper midrange, but at the expense of low-frequency output.

Which Speakers Are Right for My Car Audio System?

In general terms, you have two options for replacement speakers for your car stereo: You can choose from a number of relatively high-efficiency solutions like the X2 speakers from ARC Audio, Prime Speakers from Rockford Fosgate, Prima speakers from Audison or Uno speakers from Hertz. These are great choices if you use a radio with up to about 22 watts of power to drive them.

If you plan on adding an amplifier to your car audio system, your speaker choice might change to something like the ARC Audio ARC Series, the Rockford Fosgate Punch, Sony Mobile ES or Hertz Cento. These speakers can handle more power and have more excursion capability to play louder. With that said, they need more power to reach those output levels. A secondary reward for choosing better speakers is that they are typically clearer and more detailed.

When it’s time to upgrade your car stereo, visit a local specialty mobile enhancement retailer so you can audition the speakers they have on display. Talk to the product specialist about your long-term plans for your audio system, along with your immediate performance improvement goals. They can use this information to select speakers that will meet your expectations.

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 lighting the road in front of your car or truck at night, most enthusiasts focus on light intensity instead of headlight bulb color. It’s straightforward to see the difference between yellowish light produced by incandescent halogen bulbs and the white/blue output of HID or LED bulbs. The science behind these light sources is interestingly similar to what professional car audio technicians measure to calibrate a digital signal processor in your mobile audio system. If you’re intrigued, read on, and we’ll explain in detail.

How Light Works

There have been many detailed scientific dissertations on how light works. These papers explain the electron and sub-electron concepts that allow us to see objects. In short, light is made of photons. Photons are packets of electrons that have been released from atoms. These packets of photons have energy and momentum but have no mass. This means you can shine a light at an object to illuminate it, but the energy from the light source doesn’t make the object heavier.

If we excite a group of atoms, the negatively charged electrons that orbit the nucleus absorb that energy. As more energy is added to an atom, the electrons circle faster and farther away from the center. When the energy source (electricity or heat) is removed, the electrons snap back to their original orbit path but release that added energy in the form of photons. Under specific conditions, the photons that are released produce visible light. If you studied electrical theory in high school, you’d recognize this pattern as similar to how electricity works. The only difference is that electricity involves electrons jumping from one atom to another to transfer energy.

When the light photons escape from an atom, they can have varying energy levels depending on the electron’s position when it leaves the atom. You can think of this as the photons having a specific resonant frequency. As a result, different types of atoms release photons of different wavelengths. The result is differently colored light sources.

Light and Color

We know that light sources have different colors. An incandescent bulb gives off a very different kind of light than a fluorescent bulb, a gas-discharge arc lamp (high-intensity discharge or HID) or a light-emitting diode (LED). Some light sources appear yellow, while others are white or blue. How these light sources illuminate objects can make them look very different.

Let’s take a giant step sideways. You’ve seen plenty of rainbows, but do you know what turns the supposedly white light from the sun into a color pattern that shifts from violet through to blue, green, yellow, orange and red? Water molecules refract the light from the sun. Because white light is made up of many different wavelengths, and each is reflected at a different angle as it passes through the water molecules, the light is divided into its primary components. Sorry, I know. We got all technical again.

An expensive-for-its-size electronic device called a spectral illuminance analyzer or a spectrometer can analyze the frequency content of a light source. The spectrometer works precisely the same way that a real-time audio analyzer (RTA) looks at the amplitude of the different sound frequencies produced by an audio source. As you may have guessed, we’ve added one to the BestCarAudio.com lab.

If you compare the two spectrographic measurements, you can see that the water vapor in the clouds is blocking increasing amounts of green, yellow, orange and red light. Unsurprisingly, we are left with a light source that makes everything look dull. This is because the water vapor in the air has quite literally filtered out the light energy that makes colors pop.

The software scales the measurement window to make it easy to see energy levels at different wavelengths. This is similar to the way our eyes or the iris and shutter on a camera work together to deliver a similar level of perceived brightness for a given lighting condition. The chart below shows both measurements overlaid, one on top of the other. You can see that the overall brightness level on a cloudy day is significantly lower.

The measured light level was 106,252 lux on a sunny day, whereas the cloudy day was only 9,069 lux. Converted to candlepower, the numbers are 9,874 and 843.

Headlight Bulb Color

When it comes to the headlights on your car or truck, bulbs come in various colors for a variety of reasons. At the incandescent end of the spectrum, most have a yellowish look. With that said, halogen bulbs (which use iodine and bromine gas) have less yellow and produce more light output than old bulbs that use argon. Here’s the spectrographic analysis of a relatively simple halogen light bulb.

As you can see, there is a lot of energy in the red portion of the light spectrum produced by this bulb. To be clear, it’s not an amber bulb, though; we should find one of those and test it as well.

OK, we’re back from the hardware store with a pair of Sylvania 3057AK amber turn signal bulbs. The graph below shows their spectral energy.

How we perceive the color of a light source is dependent on the frequency content of the energy coming from the bulb. Warm light will have more red energy, where a cool bulb will be bluer.

Color Temperature and Color Space

If you’ve ever shopped for HID headlight bulbs, you know their color is often described by a specific Kelvin value. For example, a yellow fog light bulb might be rated at 3,000 K, where a factory-installed HID or LED bulb might be a very pure white rated at 6,000 K. Those bulbs with a very blue tint are often up in the 8,000-10,000 K range.

Most people think these values are somewhat arbitrary, but the reality is, the light color can be measured with impressive accuracy using the right equipment. Our spectrometer can do this quickly and easily. The software will also plot the measurement on what’s called a color space chart. The chart outlines the level of red, green and blue in the light source and uses X and Y coordinates to describe the location on a chart. For our testing, we’ll use the CIE 1931 color space chart. The image below shows us where our measurement of the Wagner bulb falls.

The software tells us the Wagner light source has a correlated color temperature of 3,174 kelvins. As mentioned, that’s considered a warm yellowish light. The amber Sylvania bulb has a color temperature of 1,857 and falls into the orange and red portion of the light spectrum.

White Light Isn’t Always Made Up Of All Frequencies

The last item we’ll touch on in this article is a bit of a tease toward some future content we are working on. If you’re reading this, then you’re likely looking at a computer or smartphone screen. The light created by that screen is made up of tiny red, green and blue pixels. The colors you see depend on the intensity of each of those pixels. If the screen is to be blue, then only the blue pixels will be illuminated. For violet, the red and blue will be turned on. Yellow is produced by red and green. You can easily see this pattern by looking at the CIE 1931 color space images above.

What might be surprising to some is that the perception of white can be made up of specific amounts of red, green and blue light. The chart below shows a measurement of the light produced by the laptop screen on which this article was created.

Behold! Our Dell XPS 13 laptop screen is perceived as white, yet it’s primarily red, very light green and mostly blue light. Here’s how the white light it produces measures on the CIE 1931 chart.

Our screen has a correlated color temperature of 6,662 K. If we were scoring it on even whiteness, that’d be an excellent result. But does this score mean it’s a perfect source of white light? Absolutely not! We’ll leave you to ponder that thought as we prepare the next few articles.

Lead-in Image: Thanks to Josh Matthews for sharing this photo of an Acura RSX equipped with decidedly blue headlights.

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.