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.

When it comes to subwoofer sizes for car audio systems, many people think that bigger is better. While we won’t argue with the fact that a speaker with more cone area can be more efficient, the output capabilities of a subwoofer depend significantly on the enclosure it’s installed in. In this article, we are going to look at a sure-fire way to make sure you get the bass performance you want from your mobile audio system.

Why Do You Need a Car Audio Subwoofer?

Making good bass that is clear and loud requires a lot of air movement. A small 4-inch speaker in the dash of your car or truck simply can’t move far enough to pressurize and rarify enough air to make acceptable bass. Subwoofers are speakers that are designed to play frequencies below 100 Hz. These speakers feature large voice coils to dissipate large amounts of heat, with suspension designs that allow for lots of cone movement. When installed in a properly designed enclosure, subwoofers relieve the smaller speakers from having to try to play bass frequencies. Being able to focus on midrange information reduces cone excursion requirements and decreases distortion.

Subwoofer Size Versus Low-Frequency Extension

When buying a subwoofer, you need to determine how much space you’re willing to assign for the enclosure. Larger subwoofers require a larger enclosure to produce the same amount of low-frequency output as smaller-diameter subwoofers. To begin to understand this concept, let’s use a few examples. Say we have enough room to have an enclosure built with an internal air volume of 2 cubic feet. This is a very flexible size in that the options for subwoofer are extensive. We could use a pair of tens with the enclosure sealed, a pair of tens with a vented design, a pair of twelves sealed, or a single 12 in a vented design. Which is loudest? Which is best? Let’s have a look.

The graph below shows the predicted free-field output of a pair of ARC Audio Black Series 10-inch V2 subwoofers in a sealed and vented design with a total volume of about 2 cubic feet. The red curve is the sealed design and the orange curve is the vented design.

The vented design increases the total system efficiency at all frequencies from 20 Hz to beyond 100 Hz. In this simulation, the dual 10-inch vented design is the winner. What about using larger woofers? Let’s compare the performance of a pair of Black 10’s to a pair of Black 12 subwoofers. The yellow line in the graph below represents the predicted output of a pair of Black 12V2 subs.

As you can see, in this simulation, the response curve of the 12-inch subwoofers mimics that of the tens, but with an increase in efficiency of more than 3 dB.

Here’s where things start to get tricky. What about a pair of tens in a vented design as compared with a pair of twelves in a sealed enclosure? The graph below tells the tale.

Down to 25 Hz, the tens in the vented design are more efficient than the twelves in a sealed design. What if you want good efficiency and want to fill in that deficiency in efficiency below 25 Hz? How about throwing a simulation of a single twelve into the mix?

The green line added to the previous graph shows the response of a single ARC Audio Black 12V2 subwoofer in a 2-cubic-foot vented enclosure. It’s not as loud as the pair of tens or twelves above 30 Hz, but it’s the loudest at 20 Hz. It all depends on your choice of music and how much low-frequency extension you’re after.

More Subs Isn’t Always Better

We are going to add one more graph to our article. This graph shows the original pair of 10-inch Black-series subwoofers in the 2-cubic-foot sealed enclosure in red and the predicted response of using three of those subs in the same enclosure. Up at 70 or 80 Hz, there is some increase in output, but down around 30 or 40 Hz, where the fun bass exists in most music, the output is almost the same. So, is there an advantage to running three subwoofers in this enclosure? Not really.

What About Subwoofer Power Handling?

The final consideration in this discussion of the best subwoofer choice for a given amount of space is power handling. There are two types of power handling to take into consideration with subwoofers: thermal and physical. Thermal power handling is determined primarily by the size of the subwoofer voice coil. Larger coils can handle more heat. In the case of the Black subwoofers in this article, both subs have a 3-inch coil, but the 12 has a 500-watt RMS power rating as opposed to the 400-watt rating of the 10.

In terms of physical power handling, that’s something that needs to be evaluated in simulation software. The graph below shows how far the woofer cones move relative to frequency. The chart below shows the sealed tens in red and the vented tens in orange. With an Xmax spec of 16 mm, the vented enclosure is good to just around 22 Hz. At that point, the cone might bottom out. Adding an infrasonic filter at this frequency would help prevent damage. In reality, unless you’re deliberately playing music with lots of extremely deep bass, you should be fine.

Upgrade Your Car Stereo with a Subwoofer

If you’re heading to your local specialty mobile enhancement retailer to talk about adding a subwoofer to your audio system, start by planning how much space you can allot to the enclosure. This information will help the product specialist determine what size subwoofer and how many are best for your listening preferences.

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.