If you’ve been a reader of BestCarAudio.com, you know we’ve published a lot of articles about distortion. We include detailed measurements of harmonic and intermodulation distortion in our Test Drive Reviews to help show you the quality and performance differences between products. In this article, we’ll make a series of speaker distortion measurements using our new Clio audio analysis hardware to explain why investing in the best quality speakers you can afford is crucially important.

An Overview on Distortion

Before we start talking about distortion, we ask that you forget about amplifier clipping. That’s not what we’re talking about here. Yes, clipping IS the addition of significant amounts of unwanted information to an audio signal. With that said, clipping should only happen when an audio system isn’t designed or operated correctly.

The distortion we are discussing happens in low, mid and high volume levels and comes from every component in the audio signal path. Source components in an audio system add a small amount of distortion. Quality amplifiers shouldn’t add much unwanted information when operated in their linear range. On the other hand, speakers can easily add a lot of distortion.

Any time information is added to the original recording, that’s distortion. It could be hiss from an improperly configured processor or harmonics from a poorly designed amplifier. Have a look at this article (https://www.bestcaraudio.com/what-do-better-car-audio-amplifiers-sound-like/) that discusses the performance differences between low-, medium- and high-quality car audio amplifiers to get a feeling for just what they add to an audio signal.

Let’s look at a theoretical example of distortion before we dive into measuring any speakers. Imagine that we’ve created a single-frequency test tone to evaluate the distortion characteristics of audio equipment.

The graph above shows a spike at 1 kHz. There’s nothing else of significance in the display.

Next, we might play the above recording of a 1 kHz tone through a medium-quality source unit. Though it can be subtle, every audio component will add a number of harmonics to the signal. The output of our head unit might look like the graph below.

The graph above shows the same 1 kHz tone, but harmonics have been added to the signal at 2, 3, 4 and 5 kilohertz. The loudest harmonic, measured at 80 dB below the original signal, would represent a signal distortion of 0.010%.

The source unit has added information to the audio signal that wasn’t in the original recording. For example, the small spike at 2 kHz is second-order harmonic, the spike at 3 kHz is third-order, and so on. The relative level of the even and odd harmonics can give the audio component a harsh sound or make it sound unintentionally warm. Either way, the sound has changed from the original recording, and that’s not what we want any audio device to do.

Passing that slightly distorted audio signal into an amplifier will have the same effect. It will create multiples of any and every frequency that passes through it. So, it will add more unwanted information at 1, 2, 3 and 4 kilohertz, along with harmonics of each of those frequencies as they were present in the signal going into the amp. Below about -110 dB, you aren’t going to hear that information. We’ll get into another deep discussion of intermodulation distortion as we prepare to evaluate speaker configurations.

Let’s Test a Car Audio Speaker

It’s easy to create a low-quality speaker. Guess at a cone mass, pair that with some random voice coils, spiders and surrounds, then glue them together, plop those parts in existing baskets and put a label on the box. If you think there are speakers on the market that aren’t created this way, you’re wrong.

A good speaker is typically designed backward, from a target performance objective. For example, the aim could be a smooth response through a particular range of frequencies, enhanced low-frequency extension or maximum output efficiency. Most often, a group of these characteristics are combined during the development phase. Once the guidelines have been established, an engineer can model different components in simulation software. Once a plan is in place, parts can be developed to hit target mass, dimensional, compliance and electrical characteristics.

The companies with a wealth of knowledge in designing and testing speakers have a foundation for what works in each application. As such, hitting a target performance goal is more efficient and the results more accurate. Some companies use test equipment that combines acoustic measurements with laser-based cone movement measurements to evaluate samples and adjust or fine-tune the design. Hardware like this is available from Clio and Klippel.

No matter how hard the engineer tries, designing and producing moving coil loudspeakers is challenging. A little too much or too little glue can change performance. A misalignment of the vertical height of the coil to the cone and spider can result in non-linear performance. It’s easy to get this all wrong, and as such, it’s difficult to produce speaker products that are consistent in offering excellent performance.

Let’s Measure Speaker Distortion

We will start this evaluation of speaker distortion by testing a 6.5-inch coaxial speaker that was introduced to the car audio market in 2004. I knew from the first time I heard it that there was something odd with the design. First, there’s a sharpness in the upper midrange that’s quite unpleasant. The second reason I chose this driver is that it has the tweeter mounted right at the base of the woofer cone. (Why this is important will be revealed in an upcoming article.)

Let’s set the speaker up in my 2.2-cubic-foot test enclosure and measure the driver’s frequency response at a drive level of 1 volt and the microphone at 0.5 meter. The results are in the graph below. Ignore what’s happening below 30 Hz – those are room reflections.

The measurement above tells us a few things. First, there’s a nasty dip of 10 dB at 5 kHz and a second dip that extends from 6.5 to 7.4 kHz. Second, it also has a LOT of energy in the top end, rising steadily from 2 kHz to be almost 10 dB louder than the midrange level. Even if these measurements don’t correlate directly to what might be found in an anechoic chamber, they give us a clear idea about what’s going on with the speaker design.

Let’s Look at Distortion

The Clio measurement system can measure total harmonic distortion and precisely quantify second- and third-order harmonic content. So let’s sweep this speaker again at the same drive level and look at the distortion output. Once again, please ignore the bass information below 30 Hz.

The red trace is the measured frequency response of the speaker that we saw previously. The blue trace is the level of unwanted second-order harmonic distortion. The green trace is the level of third-order harmonic distortion. Finally, the violet trace is the sum of all the distortion content produced by this speaker.

To clarify these measurements, when the speaker is fed a signal at 200 Hz and reproduces that tone at an output level of 85 dB, it will also produce output at 400 Hz at a level of 42 dB and 800 Hz at 34 dB. The 400 and 800 Hz sounds were NOT in the original recording. These characteristics repeat for every audible frequency. So tones at 201 Hz have 402 and 804 Hz harmonics added, 202 Hz tones have 404 and 808 Hz harmonics, and so on across the entire frequency spectrum.

We can see that below 500 Hz, distortion increases quickly as frequency decreases. This phenomenon becomes clearly apparent at about 125 Hz where the total distortion jumps to 21 dB below the primary signal. That’s equivalent to about 10% THD. From 500 to 1 kHz, the distortion level is fairly constant at around 45 to 50 dB below the fundamental signal. That works out to between 0.3 and 0.5% THD.

The type of distortion that is added changes based on frequency as well. Below 500 Hz, the distortion is primarily the second-order blue trace. This kind of distortion is usually because of variances in suspension compliance and magnetic field linearity. Above 500 Hz, the distortion becomes primarily third-order, which can be attributed to changes in inductance. Above 1 kHz, distortion is usually based on cone and surround resonances. When we refer to changes in a characteristic, we are talking about variations in cone position and drive level.

The Tip of the Iceberg in Speaker Distortion

As mentioned, this is a preliminary introduction to speaker distortion. We’ll follow up with additional tests on speakers over the next few months to help explain the differences between low-quality and premium solutions. In the meantime, if you’re shopping for speakers, let your ears do the math for you. Drop by your local specialty mobile enhancement retailer to audition the upgrade solutions available for 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.

If you’ve scheduled an appointment with a local specialty mobile enhancement retailer to have your car or truck upgraded, there are a few things you’ll want to know to make the most of this opportunity. Whether the upgrade involves a new set of speakers, a multimedia receiver with a backup camera or a remote car starter, having the vehicle in a condition that will ensure that the technician can get to work quickly can save a lot of time. We’ve put together this simple guide to help make you a better customer and ensure that your project is completed on time and budget.

Please Arrive on Time

Mobile enhancement retailers work on a schedule. They’ve scheduled your car or truck for a certain amount of time to accomplish a task. In most cases, other clients are scheduled before and after you. If you show up five or 10 minutes late, that’s not only frustrating, but it can affect the entire day’s schedule and put other customers’ projects behind.

If you have an appointment, we suggest showing up about 15 minutes early. This extra time will give you and the product specialist a chance to confirm the details of the installation and allow the technician to pull the car or truck in and get the product prepared. If you’re having a new multimedia radio installed, the shop may have questions about where a USB connection for CarPlay and Android Auto should be located. If the upgrade is a remote starter, you and the specialist might want to review options like trunk or hatch release or automatic rear window defroster activation. In most cases, these items would have been covered before the quote was provided, but it’s always worth talking about as it’s easier to add them at the time of the installation as opposed to a few weeks or months later.

Please Bring What’s Required

In the rare case where you have the equipment to be installed in your possession before an installation appointment, please be sure to bring it with you. This applies to audio installations as well as remote starters. Many times, the starter and accompanying installation have been purchased in advance so the system could be presented as a gift. Make sure you bring everything with you on installation day. If you’ve opened the package, be sure to put everything back. A missing harness or remote might prevent the project from being completed and could result in additional costs.

Speaking of remote car starters, the specialists at the retailer you are working with might have asked you to bring both keys for the vehicle. This may be necessary to program the interface module to the vehicle. Without them, the installation can’t be completed. If you aren’t sure if you need to bring both keys, please bring them anyhow.

Would You Mind Taking Your Stuff Out of the Vehicle?

This is one of the biggest frustrations for installation technicians. Imagine you’ve scheduled your car or SUV for a subwoofer system installation, but the cargo area is full of sports equipment, work supplies or tools, or even purchases from a recent shopping trip. The technician will need to spend time moving these items before they can start work. This extra work can easily add five minutes to the beginning and end of each project. By the end of the day, it’s not unreasonable for them to have wasted half an hour just moving personal belongings when they could have spent that time upgrading client vehicles.

If you have an appointment, empty your vehicle. Start at the front and work backward with a basket or bag. Empty the center console, the storage compartments in the doors, items from the floor and the back seat. Clear out the cargo area of any items as well. Please do these things even if you don’t think those areas will need to be accessed. Sometimes a technician will have to run wiring through the vehicle for a remote starter or audio system installation. Anytime there’s stuff in the way, time is wasted. Trust us when we say that they appreciate you having the vehicle ready.

Give the Vehicle a Quick Cleaning

It only takes 15 minutes to run a car or truck through a touchless car wash before an installation. Getting dirt and debris out of the door sills will help a technician installing a remote starter stay clean. Clean fenders and the area around the trunk or hatch can prevent scratches, even if a fender cover is being used. The technician working on your vehicle will need to access the battery if an amplifier installation is involved in an upgrade, so they will be moving all over the vehicle.

If you can, vacuum the interior before you show up for an appointment. Some of us are fanatical about keeping the interiors of our cars and trucks clean – some aren’t. Nobody wants to work around old drink cups, food wrappers, stray French fries or used straws. If you can vacuum out sand and gravel, our floor mats will be cleaner for the next client.

Winter Installation Appointments

You can do a few things to help us work more efficiently when it’s cold out. First, if possible, please visit the car wash just before you arrive. Getting as much slush and snow off the vehicle and out of the wheel wells reduces dripping and puddles as the vehicle warms up in our bay.

If we have to remove interior trim panels from the vehicle to install a radio or speakers or run wiring, things go much better if the car has warmed up. Plastics are more fragile when they’re cold. The last thing we want is for something to break. If we’re having a busy day, it might be difficult to factor in time to let the interior warm up. If you’ve got the car up to temperature and the heater’s been on, we can get to work right away and ensure that your vehicle leaves our bay in the same or better condition than when it arrived.

Your Local Specialty Mobile Enhancement Retailer Says Thanks

It’s not easy to run a mobile enhancement business. Anything you as a client can do to help every project run smoothly and efficiently is genuinely appreciated. If there’s an audio component that needs to be replaced, if you’re interested in getting better sound from your stereo or are shopping for a remote car starter to make your vehicle more comfortable, please drop by one of the specialty mobile enhancement retailers near you. They’d be happy to help!

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.

Let’s say that you are building a car audio system intended to produce as much bass as possible. In that case, you are going to need subwoofers capable of handling vast amounts of power. You’ll also need amplifiers capable of pushing those subwoofers to their limits. It’s not uncommon to see cars and trucks with more than 5,000 watts of power being sent to a single subwoofer. In these systems, it’s common to see a pair of amplifiers in what’s called a strapped configuration driving a single speaker. This article explains how the concept of strapping works to deliver massive amounts of voltage and current to your subs.

Strappable Car Audio Amplifiers

First and foremost, you’ll need to make sure that the subwoofer amplifiers you have chosen are capable of being strapped. Making this assumption without checking the owner’s manual can result in a lot of frustration. If you try to strap two amplifiers that aren’t designed for this application, you will damage one or both of them.

Second, don’t assume that a subwoofer amp model is strappable because it has a master/slave switch or an audio signal input and output separate from the standard RCA input connections. Those inputs and outputs may exist to make it easy to daisy-chain multiple amplifiers together, so only a single sensitivity control, crossover adjustment, infrasonic filter and remote bass boost setting works for several amplifiers.

Strapping a subwoofer amplifier involves using two identical amplifiers. The amps must have some sort of master/slave switch, and depending on their design, might also have a polarity or phase control switch. For our example, we’ll assume we are using a single voice coil high-performance subwoofer, just to keep things clear. In reality, as long as the load impedance doesn’t exceed the rated limits of the amplifier, you can wire up as many subwoofers as you want.

Wiring Two Amplifiers to One Subwoofer

Image Caption: A pair of Rockford Fosgate Power T2500-1bdcp amplifiers wired to a single T3S2-19 19-inch Superwoofer. Individually, these amplifiers can produce at least 2,500 watts of continuous power into a 1 ohm load.

The drawing above shows the positive and negative speaker wiring, along with the required jumper wire that runs between the two amplifiers for this pair of Rockford Fosgate amplifiers. Your installer must obtain the correct strapping information from the amplifier manufacturer for the models you have chosen. Unfortunately, that information is not universal or transferable.

Aside from the right speaker wiring, these particular amplifiers have to be connected using a bd-Sync cable and a set of RCA cables. The top amplifier is set to master mode. This amplifier will be responsible for gain adjustment, low-pass crossover filtering, infrasonic filter selection and the remote Punch EQ control function. When set to slave mode, the second amp takes the audio signal from the output of the preamp stage of the first amp and feeds it to the output stage of the second amplifier. This configuration bypasses all the adjustments on the second amplifier.

For this configuration to work, the polarity of the second amplifier has to be inverted relative to the first. On the Rockford Fosgate amplifiers, this is achieved by setting the phase switch to 180 degrees. With this setting engaged, if the audio signal from the positive terminal of the first amplifier is increasing in voltage, the same terminal on the second amplifier will be going more negative. The result is twice as much voltage being applied to the subwoofer as would be available with a single amp, up to the current delivery capacity of the amp design. In the case of these two amplifiers, that would be 5,000 watts of power into this 2 ohm load.

Load Impedance Matters

Just as when your installer bridges a stereo amplifier to a subwoofer, the minimum load impedance decreases compared to when speakers are connected to a single channel. For the Rockford Fosgate amps, the minimum load impedance is 1 ohm when each amp is run independently. However, when two amplifiers are strapped to a single subwoofer, the minimum load impedance is 2 ohms.

The minimum load impedance is cut by half because the power production attempts to quadruple. Allow us to explain.

If a single T2500-1bdcp can produce 2,500 watts of power into a 1 ohm load, the maximum current it can supply to the sub would be 50 amps, and the voltage would be 50 volts. Strapping the amplifier now presents the subwoofer with up to 100 volts across the terminals. If we apply 100 volts to a 1 ohm subwoofer, the power would be 10,000 watts, and the load would draw 100 amps of current. While impressively powerful, these amplifiers can’t supply that much current, so we need to double the impedance to cut the load current in half. Delivering 100 volts across a 2 ohm load results in 50 amps of current flowing through the subwoofer.

Things to Think about When Strapping Amplifiers

By the way, you will want your installer to run at least eight AWG power cables from the amps to the subwoofer. By way of an example, the voltage drop across 12 feet (6 feet for the positive lead and 6 feet for the negative) of eight-AWG copper wire that is passing 50 amps of current is 0.404 volts. So it wouldn’t be crazy to make two runs, or upgrade to six or four-AWG cable if it’s available to reduce that drop and deliver more power to your subwoofers.

Not to sound all preachy, but a potential of 100 volts is a very high voltage. The electrical outlet in the walls of our homes operates at 120 volts. We know it’s not safe to play with those circuits. Make sure your installer has secured all the electrical connections to your subwoofers properly. You don’t want a wire coming loose or shorting. You also don’t want anyone to be able to touch those terminals when music is playing. Quite simply, the results could be lethal.

If you plan on competing in a car audio competition where maximum output matters, then look into car audio amplifiers that are strappable. This configuration delivers more voltage to your subwoofers and will increase the efficiency of your system compared to using low-impedance subwoofers. A specialist mobile enhancement retailer near you can help you choose amplifiers that will deliver thousands of watts to your subs. Drop in today to find out what’s available.

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.

The staff here at BestCarAudio.com look at dozens of installation photos each day and continue to see tweeters that aren’t installed in a way that will maximize the listening experience. Our goal is to help consumers get the best performance possible from their car audio system upgrades, so we’re going to perform two tests to demonstrate the importance of understanding speaker dispersion patterns. This information is vital to optimizing the angle at which tweeters are installed in a car audio system.

Let’s Talk About Speaker Directivity, Again

The term directivity describes where the sound created by a speaker goes. For the purposes of this article, we are going to talk specifically about tweeters. (We’ll follow up soon with another article about midrange speakers and woofers.) A clear understanding of these concepts for all speaker sizes is crucial to proper car audio system design and installation.

As a caveat, we want to make it clear that directivity occurs with every type of speaker from every company at every price point. Inexpensive speakers are no different from those that cost thousands of dollars. For this test, we used a 1.5-inch audiophile-grade automotive tweeter. We choose this driver because we know it has a flat response and minimal distortion.

When we talk about speaker directivity, we need to compare the circumference of a speaker to a wavelength of sound. Wavelength is calculated by dividing the speed of sound (343 meters per second) by frequency. As an example, a 1 kHz tone has a wavelength of 34.3 centimeters or about 13.5 inches. A 40 hertz tone is 8.575 meters or 337.6 inches. The length of the pipes in a church organ is calculated using this wavelength information. The same holds for wind instruments like trombones or trumpets.

For speakers playing low frequencies relative to their circumference (and proportionately, their diameter), energy radiates forward, backward, sideways, up and down. You can think of this in the same way that light radiates from a candle. Candles aren’t brighter to the side or above. The light created by a candle is a point source that radiates outward and evenly in all directions.

At extremely high frequencies, sound radiates from the speaker similarly to light from a flashlight. If you are off to the side of a narrow-beam flashlight, you won’t be illuminated. For speakers, the same thing happens. Off to the side of a speaker, high-frequency information can be attenuated by 24 decibels or more compared to being directly in front of the speaker.

Speaker Diameter Affects Directivity

The directivity characteristics of a speaker depend on the size of the speaker cone or diaphragm. Keep in mind that the advertised “size” of a woofer or midrange doesn’t describe the diameter or circumference of the actual speaker cone. For example, a 6.5-inch speaker doesn’t have a cone with a diameter of 6.5 inches. It’s usually closer to five.

For our 1.5-inch tweeter, the diaphragm has a circumference of roughly 4.712 inches, which is the wavelength of 2.865 kHz tone. Each speaker has a unitless value known as ka. The ka value is the driver’s circumference divided by wavelength. Directivity can be described as multiples of ka. For our tweeter, ka is equal to 4.712 kHz; ka = 0.5 is 1.43 kHz; ka = 2 would be 5.7 kHz; and ka = 5 would be 14.3 kHz. Above a frequency where ka = 1, the speaker becomes increasingly directional. Below this frequency, sound radiates evenly in all directions — even behind the speaker.

The graphs above represent a generalization of how the output of a speaker changes as you move off-axis from being directly in front of the driver. As can be seen in ka values of 1 or less, you would hear almost as much of that frequency when standing behind a speaker as you would being directly in front of it. By the time ka = 3, you don’t hear anywhere near as much to the speaker’s side, and it only gets worse as frequency increases.

Directivity Testing

We set the tweeter up on a pedestal and took a series of measurements at 12-degree increments. The graph below shows how the tweeter output decreases at high frequencies as the listing angle increases.

The red trace represents being directly in front of the speaker. Frequency response is within 5 dB from 1.5 kHz to above 20 kHz. Since we don’t have an anechoic chamber and are using windowed FFT measurements, these are adequately accurate results for this article.

The blue line has the microphone positioned 12 degrees to the side and directly on-center. At a meter, that’s a distance of only 20.9 centimeters or roughly 8.2 inches to the side. There are some minor changes in response up to 15 kHz of about 1 dB. At 20 kHz, the output has decreased by about five dB.

The dark green trace now has the microphone located 24 degrees off-axis. Overall output is down another dB or two between 3kHz and 15kHz, but the output at 20 kHz is down 13 dB. As we move farther and farther to the tweeter side, the output decreases more and more.

Think back to the math we did to calculate that ka = 1 frequency of 2.865 kHz. All the frequency response measurements are nearly identical at that frequency and below, and they start to separate more and more at multiples of that frequency. It’s almost like the math works!

Option 2 – The Tweeter Bounce

It’s not always physically easy to position a tweeter so it aims equally at the driver and passenger. One option in these instances is to install the tweeter near the base of the windshield and point it upward. The sound from the tweeter will bounce off the glass and radiate into the listening area.

While this sounds ideal, there are drawbacks. In this configuration, you effectively have two sound sources with different path lengths. This difference in path lengths will cause a certain amount of constructive and destructive interference called comb filtering.

The graph below shows the response of our audiophile tweeter at zero degrees in red, at 48 degrees in blue and measurement at 90 degrees off-axis in green. The fourth measurement is still at 90 degrees, but we have added a large piece of glass in front of the tweeter and angled it at 45 degrees. This last trace is in gray and shows us the measured response off of the glass.

Bouncing the tweeter output off our windshield analog, the response above 4 kHz is as good as if the tweeter were installed on-axis directly with the listening. But, unfortunately, everything comes with a price. We now have a dip of about 8 dB at 2.7 kHz. Yes, we could fix that with an equalizer, but that would require driving the tweeter with more than six times as much power around that frequency range. We could raise the crossover point to 3.5 kHz, but now we might have frequency response problems with the high-frequency information from the midrange speaker.

The Takeaway on Aiming Tweeters

If you want to hear all the music your stereo reproduces, then it would be ideal to be within plus or minus 15 degrees of on-axis with the tweeters in your car audio system. Any effort you might have put into reproducing the highest audio frequencies with better amplifiers or high-resolution audio players is lost if you are beyond that angle. You can also explore how your system behaves with the tweeters in the corners of the dash. You’ll sacrifice a bit of stage width and may have to deal with some frequency response issues at lower frequencies than sail panel locations, but it might require less fabrication.

We’d never argue that installers and technicians have different tuning and installation methods. With that said, and in spite of their best efforts, they can’t change the laws of physics. Choosing a tweeter location that has both of the tweeters pointed at the middle of the car between the driver and passenger’s head will ensure both can enjoy extended frequency response with good symmetry from both sides of the vehicle. Drop by your local specialty mobile enhancement retailer today to discuss how they can aim the tweeters in your car or truck for the best performance.

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.

It seems do-it-yourself installers have taken a liking to our discussion about wiring multiple subwoofers to a single amplifier. The popularity makes sense, since many car audio enthusiasts aren’t familiar with series and parallel wiring. A question came up on Facebook a few weeks ago asking if it was better to wire a pair of dual voice coil subwoofers in series with their coils in parallel or vice versa. We thought it might be fun to turn that question into yet another experiment and dive deep into the options of series-parallel wiring.

Wiring Dual Voice Coil Subwoofers

Unless your installer has access to some very low impedance subwoofers, most installations will see the subwoofers you have purchased wired in parallel. For example, say you’ve chosen a pair of 10-inch subs with dual 4-ohm coils. In that case, your installer could wire all four coils in parallel to present a 1-ohm load to a monoblock subwoofer amplifier. What if you’re after a solution that will offer the best sound quality possible, and you’ve chosen a two-channel Class-AB amp to power your subwoofers? In most cases, these amplifiers want to see a 4-ohm load when bridged. It’s not difficult to wire a pair of dual 4-ohm subwoofers to present this load, but there are a couple of options.

Series the Coils’ Woofers on Each Driver, Parallel the Subwoofers

Your installer’s first option is to wire the voice coils on each subwoofer in series. For our dual 4-ohm subwoofers, this wiring configuration would add the voice coil impedance on each driver to produce a nominal 8-ohm load. Next, your installer would wire each subwoofer in parallel with your amplifier to create a 4-ohm load.

Parallel Each Woofer’s Coils, Series the Subwoofers

The second option is to wire the voice coils on each subwoofer in parallel, then wire the two subwoofers in series with each other to the amp. Each subwoofer would have a net impedance of 2 ohms, and wiring those loads in series would present our amplifier with a 4-ohm load.

However, our subwoofers aren’t resistors. We talked about the reactive characteristics of speakers and subwoofers not long ago in this article. Since we’re dealing with inductance and capacitance along with the resistance of the voice coil, is there a chance that the two wiring options present different results in terms of performance? Let’s see what happens!

Let’s Do a Test!

We have a pair of 10-inch subwoofers that we’ve meant to install into the sound system in our office. Yes, we need the ability to reproduce 25 Hz with authority while watching Cleetus McFarland, AvE, Project Farm and bigclivedotcom on YouTube. OK, maybe we don’t NEED it, but we want it. As we described in our examples above, the subwoofers have dual 4-ohm voice coils, so they’ll be perfect candidates for our experiment.

First, we measured the Thiele/Small parameters of one subwoofer using our new Clio Pocket 1 portable measuring system. Next, we measured the sub with its voice coils wired in series and then again with the coils wired in parallel to generate the data below.

Not surprisingly, the mechanical characteristics like resonance frequency (Fs) and compliance (Vas) didn’t change. As we expected, the electrical measurements like DC resistance, electrical Q, and inductance (at 1 kHz) did change.

Electromechanical Series-Parallel Wiring Results

Next, we wired the subwoofers together in the configurations we showed in the two diagrams at the beginning of the article and repeated the measurements to see what, if anything, had changed.

We’ll start by saying that the differences are minimal. The reality is, the system will work just fine wired either way. With that said, there are signs that wiring the coils on each sub in series and wiring the subwoofers in parallel is slightly beneficial.

If you look at the chart above, the DC resistance of the C-S W-P configuration is a little lower, as is the driver’s total Q (Qts). A lower Q-factor can mean less resonance at Fs and a more accurate bass response.

Sometimes an experiment yields earth-shattering results. Other times, the outcome is subtler or less controversial. Most professional installers wire coils in series and those subwoofers in parallel. If you need a hand choosing suitable subwoofers for your car audio system or help in wiring them, drop by your local specialty mobile enhancement retailer today.

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.