When it comes to upgrading your car audio system to deliver amazingly realistic performance, many people choose what’s known as a three-way front stage. In the simplest of terms, this refers to there being three speakers on each side of the vehicle. As we explained in our article about the need for different speaker sizes, your audio system requires woofers and tweeters to reproduce your music properly. The question is, why add dedicated midrange drivers to the mix? Read on to learn the answer.

The Source of Sound

One key advantage of using a dedicated midrange speaker with a woofer and tweeter is that the small speaker can be placed on the dash or at the top of the door. These locations can deliver the perception that the voices are coming from a point higher in the vehicle than if you were relying solely on a woofer mounted in the door. Ideally, your audio system should — when designed, installed and calibrated properly with a DSP — seem to reproduce a soundstage that spans the middle of your windshield from pillar to pillar, or beyond.

In a two-way speaker system with a woofer and a tweeter, audio frequencies below 3,500 Hz may seem to come from the doors. This causes the height of the soundstage to be stretched vertically in the vehicle, and it detracts from the sense of realism. Adding a set of midrange speakers can raise the soundstage.

Consistent Frequency Response

Every speaker in the world, from every manufacturer, experiences a phenomenon called directivity. Directivity refers to the shape of the sound being created by the speaker with respect to the frequency of the sound. Take, for example, a 6.5-inch woofer. At low frequencies, the sound created by a speaker emanates in a spherical pattern that would, if possible, extend behind the speaker itself. This characteristic is part of why the shape of the mounting surface for a speaker is so crucial to its performance.

As the output frequency increases, the shape of the sphere moves from being equal in a 360-degree circle around the speaker to a ball in front of the speaker. The sound created outside this ball doesn’t cease to exist, but it is definitely attenuated (quieter).

A further increase in frequency results in the ball narrowing to what would be perceived as a spotlight shape. Unless you are in front of the speaker, these audio frequencies will be quieter.

Directivity is an issue because, in almost every vehicle, the speakers aren’t aimed on-axis with the listener. For a door-mounted woofer, we may be at as much as a 70-degree angle. If this speaker is operated with a tweeter and filtered at 4,000 Hz, we may be sitting in a position where there is very little output.

The chart below shows, in general terms, the maximum frequency you want to use for a given size of speaker in order to maintain smooth frequency response throughout the listening environment.

Increased Low-Frequency Output

For the product specialist designing your audio system, selecting a woofer, midrange and tweeter for a three-way front stage may, depending on the brand being used, allow for a slight improvement in bass performance from the woofers. Since there’s no need for the 6.5- to 8-inch woofers to produce midrange frequencies much above 400 Hz, the cones can be a little heavier, so they play deeper than a similarly sized speaker that needs to play to 4,000 Hz.

Some companies switch from using a phase plug on their midrange drivers that play higher frequencies to adding a dust cap. The dust cap adds mass to lower the resonant frequency of the driver.

Another advantage, especially for those audio systems without a subwoofer: Your installer can turn up the output of the woofer relative to the midrange to increase bass output.

Though the image below doesn’t exactly follow the laws of physics, it shows how the output of a three-way speaker system delivers even sound distribution at the listening position.

The image below shows, in the same artistic fashion, how upper-midrange audio information from a door-mounted woofer may not be clearly audible at the listening position.

Three-Way Front Stage System Design

Many companies offer three-way speaker sets that include passive crossover. Passive crossovers allow all three speakers on each side of the vehicle to be powered by a single amplifier channel. In most cases, the crossover points are fixed with passive networks, though some do include options for midrange and tweeter output levels.

To optimize the performance of a three-way front speaker set, it’s best to use a six-channel amplifier along with a digital signal processor. The features of the processor allow your installer to fine-tune the output of each speaker to deliver accurate and natural frequency response at the listening position.

Upgrade Your Car Audio System Today!

If you’re after the most realistic, detailed and accurate car audio system performance available, drop by your local specialty mobile enhancement retailer and ask about upgrading your vehicle with a three-way speaker set. Once it’s installed and calibrated, the results will be amazing!

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.

A while back, we took a look at the difference between single and dual-voice-coil subwoofers. In a nutshell, there is no benefit or drawback to either choice. The options exist so you can present the amplifier you have chosen with a load impedance that allows it to make power reliably. There have been many instances where consumers bring a subwoofer into a car stereo shop in hopes of using it in their vehicle only to find out it’s not the right impedance. They need a 4-ohm sub instead of a dual 4-ohm. The question then becomes, can you use just one of the voice coils? That’s a fair question, and it deserves a detailed answer.

Can You Use Only One Subwoofer Voice Coil?

If you look at the voice coil former and the winding of a single-voice-coil sub, you’ll find a single positive and negative connection. On a dual-voice-coil sub, there are two pieces of wire and two sets of connections. The coils can be wired in series, in parallel or individually to power the subwoofer.

Car audio installers can use a set of specifications called Thiele/Small parameters in conjunction with modeling software to predict the performance of a subwoofer in a specific enclosure. All subwoofer manufacturers provide these specifications with both coils in use.

The short answer about using one coil is no. Using one coil not only affects the thermal power handling capabilities of a subwoofer, but it also changes the strength of the magnetic field and alters the Thiele/Small specifications. Rather than explain the math involved in the change, let’s use an example.

Thiele/Small Parameter Changes

Let’s start by measuring the parameters of an inexpensive 12-inch dual-voice-coil subwoofer. We measured the subwoofer with both coils wired in parallel, then we disconnected one coil and repeated the test. The results are in the chart below:

Sealed Enclosure Performance

We modeled the subwoofer performance using both voice configurations in VituixCAD 2 software. We started with a simple sealed (acoustic suspension) enclosure with a net internal volume of 1.08 cubic feet. Graph 1 shows the output of the subwoofer with 2.83 V (which is 8-watts into a 4-ohm load) applied to the coil. The response is nice and smooth, with a good transition from the midbass region and very little ripple. The Qtc (Total Q Factor) for the system with both coils connected is 0.8. This is a good balance between low-frequency extension, efficiency and low-distortion operation. The black trace that slopes down on the left shows predicted SPL.

Graph 2 shows the response of the same driver when only one voice coil is connected. You can see that the overall output of the system has decreased significantly and that there is a lot more ripple (a big bump in the response around 57 Hz. It’s also worth noting that the total system Q has jumped to 1.18. This Qtc value is quite high and will add resonance and distortion to the system.

Vented Enclosure Performance

Next, we designed a vented (bass reflex) enclosure using the specs taken with both coils in parallel. We simulated a 2-cubic-foot enclosure with a vent tuned to 35 Hz. As you can see from Graph 3 below, using both voice coils results in relatively smooth performance across the entirety of the operating range. The system efficiency has increased dramatically as compared to the sealed enclosure, with a jump in predicted output from 87 dB to 94 dB with the same amount of power.

Finally, we can see in Graph 4 how poor the performance of the subwoofer is with only one coil connected. Output at 40 Hz has dropped by 4.5 dB, and the overall response definitely isn’t as smooth.

Make Sure Your Subwoofers are Wired Properly

The above simulations clearly demonstrate the importance of using car audio subwoofers as they were designed. Your installer will need to wire both voice coils to your amplifier to ensure that the subwoofer maintains its power rating and functions the way the manufacturer designed it. If you have any questions, work with your local specialty mobile enhancement retailer.

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.