When designing and integrating high-performance speakers into your car or truck, your local specialty car audio retailer might suggest choosing an amplifier or signal processor that includes a bandpass crossover. If you aren’t used to designing speaker systems, a task that most consumers don’t concern themselves with, then the term bandpass might be confusing. Please don’t fret; we’ll explain what it means and why it’s necessary to extract the best performance possible from your speaker upgrades.

What Are Crossovers?

The theory of a perfect speaker that produces the entire audio range, from a single driver, at an adequate output level with no directivity, is so far from reality that the concept alone makes a speaker engineer’s eye twitch. As such, we need to use speakers of different sizes to cover the audio spectrum. In the simplest of systems, we need a woofer to produce bass and midrange frequencies and a tweeter to produce high frequencies. Since most tweeters are rarely capable of reproducing information below 2 kHz with significant output, we need to block that information. We use what’s known as a high-pass crossover to pass only high-frequency information. Looked at another way, a high-pass filter blocks low-frequency information from going to your speaker.

Once we have routed high-frequency information to our tweeter, we don’t need the woofer to reproduce those sounds. So, the technician configuring our audio system will apply a low-pass filter to the woofer at the same frequency. This filter passes low-frequency audio information below our crossover point to the woofer.

What Is an Electronic Bandpass Filter?

If we decide that we want to further upgrade the audio system with a subwoofer, we’ll need more filtering. Subwoofers are great at reproducing audio frequencies below about 80 Hz. Most don’t do a good job with midbass and midrange information. As such, we want to block frequencies above about 80 Hz from going to the sub. We’ll use an 80 Hz low-pass filter to accomplish this task.

Now that we have a speaker dedicated to reproducing bass, we don’t need our woofer to play those frequencies. We can apply a high-pass filter to the woofer to block audio information below 80 Hz.

The graph you see above is called a bandpass filter. It passes audio within a specific band of frequencies. In this example, our bandpass filter passes audio information between 80 Hz and 3 kHz.

Some car audio systems add a fourth set of speakers in the form of a small midrange driver. In most cases, these speakers are mounted higher in the doors or the dash and focus on information from about 300 Hz up to where the crossover takes over. In a four-way audio system design, we can now move the low-pass crossover on our woofer to 300 Hz and run the mid from 300 Hz to 3 kHz.

Proper Crossover Configuration Is Crucial

There is a lot more to setting crossovers than just picking some arbitrary frequencies that look good on a graph. The values depend on the speaker’s low-frequency capability and its directivity characteristics. The installer calibrating your audio system also needs to consider the physical power-handling limitations of speakers and how loudly the system will be played. Quite simply, it’s not an easy task, and the process is exacerbated by component systems that don’t include drivers with adequate bandwidth to work well together.

If you want the music reproduced by your car audio system to sound amazing, drop by your local specialty mobile enhancement retailer and ask them what’s available for your vehicle. Be sure to audition one of their demo vehicles to ensure that they can deliver the performance you want. It’s not unlikely that they’ll suggest an amplifier or signal processor that includes bandpass filtering to make everything sound 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.

Dash pods, kick-panel enclosures and sealed enclosures in doors might look cool, but they aren’t always an ideal solution for a speaker that will attempt to produce bass. In this context, when we talk about bass, we are discussing audio frequencies below about 300 Hz. In this range, most drivers with a cone diameter of 4 inches or more can play down to around 125 Hz or lower. If the enclosure used with the speaker is too small, you’ll end up with unwanted distortion and limited low-frequency extension.

Modeling Speaker Behavior

Anytime a speaker will be used at frequencies below 300 Hz, we need to ensure that there’s enough air volume behind the driver so as not to affect the overall system compliance. In a sealed enclosure, air acts as a spring. This spring adds to the compliance of the speaker to form a high-pass filter. Yes, we have the benefit of increased physical power handling, but we trade bass output.

For this example, we’ll use a 6.5-inch midrange driver that’s been designed for infinite-baffle installations in the doors of a car or truck or on the rear parcel shelf of a sedan. The graph below shows the driver’s predicted frequency response in an enclosure with an air volume of about 3 cubic feet. This enclosure is large enough to simulate an infinite-baffle installation.

In this application, the driver’s -3 dB point is acceptable at 89.15 Hz, and the system has a Q of 0.672. Both calculations indicate that this mounting location will work superbly when combined with a subwoofer.

Small Speaker Enclosures

What if someone who doesn’t have experience using speaker modeling software decides they want to install this speaker in a pod in the kick panel of a car or, worse, on the vehicle’s dash? Let’s be generous and assume this pod has an internal air volume of about 2 liters or 0.07 cubic feet. What happens to the frequency response of our mid-woofer?

Our enclosure modeling software shows a peak of 4.5 dB at 236 Hz. The system Q has jumped to an unruly 1.605. Equally troublesome is the fact that bass output has been reduced dramatically. This small pod has choked the woofer, and it’s now producing 10.3 dB less output at 90 Hz.

Can We Fix This With an Equalizer?

To the uninitiated, it would seem that applying some equalization might fix the problem. If we keep the volume levels low, we could theoretically add some low-frequency equalization to compensate for output at 90 Hz. With that said, we’ll need to send almost 11 times as much power at 90 Hz for the same amount of output in a properly-sized enclosure.

Unfortunately, while we can tame the peak at 235 Hz, we can’t eliminate the resonance that caused it and the associated distortion. When the cone assembly’s mass, the compliance of the suspension and the compliance of the air in the enclosure interact, there’s a frequency where a small amount of input produces a disproportionally large amount of output. We call this the resonance frequency.

The Qtc value describes the size of the resonance. When looking at Thiele/Small parameters and calculating a driver’s behavior and an enclosure, the Qtc, or Total System Q tells us how prominent a peak in response is. It’s a unitless number in SPL, but software like BassBox Pro or Term-PRO can offer an accurate prediction.

In most cases, we want to keep the Qtc value under 0.8 or maybe 0.9 to limit distortion. These suggested limits apply to woofers in speaker pods as well as subwoofers in their enclosures. If you want your music to sound tight and controlled with no resonance or ringing, then choosing a large enough enclosure is crucial.

Pick the Right Speakers for Your Application

Suppose the audio system design for your vehicle calls for relatively large mid-woofers (4 to 6.5 inches) to be mounted in an enclosure. In that case, it’s paramount that you work with the shop to make sure the enclosure will be large enough or to pick a low-Q driver. As a second example, we model the behavior of a 6.5-inch woofer with a Qts of 0.48 in the same two enclosures.

Why Midrange Distortion Is Objectionable

If you were to talk into a real-time audio analyzer, you’d find that most male voices have the majority of their energy focused between 100 and 1000 Hz. If there’s any emphasis or distortion through this range, voices will sound unnatural and unbalanced.

Ultimately, designing a car audio system upgrade requires that the Product Specialist and installer you are working with balance speaker size with the available mounting locations in your vehicle. If a pod needs to be built, you may find that a smaller speaker will deliver a smoother frequency response with less distortion. It’s counterintuitive, but that’s just the way it works.

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.

Since 1953, the Chevrolet Corvette has been an icon in the North American automotive industry. These two-seaters represent value and performance with styling that always lets them stand out from the crowd. Try as General Motors might, there’s still room for improvement, even on a flagship vehicle like this. Let’s look at some of the upgrades available to improve the performance of the audio system in a Corvette and accessorize the vehicle to make it more functional and look better.

Corvette Audio System Upgrades

Whether your Vette came with an analog radio mounted on its side (a la C2) or a touchscreen multimedia receiver in a C7 or C8, the audio system performance in these cars has never been something to write home about. Thankfully, the aftermarket is here to support your quest for superb sound with hundreds of upgrade options.

Companies such as Custom Autosound Manufacturing and RetroSound offer twin-shaft radio designs that will work with your C1 through C3 Vette. These radios include a modern digital AM/FM tuner, Bluetooth and SiriusXM satellite radio compatibility when combined with an SXV300 tuner module. A USB port will let you connect your iPhone or use a USB memory stick to digital audio files. Best of all, these radios include preamp outputs that allow your installer to add high-power amplifiers to bring your music to life.

For C4 through C6 Corvettes, the options for radio upgrades increased dramatically. Chevrolet used a more conventional design that paved the way for hundreds of radio upgrade options for music enthusiasts. The latest generation of floating-face radios are prime candidates for adding Apple CarPlay and Android Auto to your sports car.

If you have a C7 Vette with a Bose audio system, you can upgrade the vehicle with high-quality amplifiers and speakers using a MOST radio interface such as the M650-GM from NAV-TV. This interface will extract a full-range audio signal from the digital connection between the radio and the factory amplifier. This signal can be fed to a digital signal processor and your choice of an amplifier to create an amazing audio system.

Add a Subwoofer for Great Sound

If you’ve been a reader of BestCarAudio.com for any length of time, then you’ll know that adding a subwoofer to your car is easily one of the best bang-for-your-buck upgrades you can make. Corvettes can most certainly benefit from better bass response.

Of course, you’re going to want a subwoofer solution that works with your vehicle. JL Audio offers several Stealthbox vehicle-specific solutions that are exclusively designed for the Corvette. These fiberglass enclosures are molded to fit the contours of your car perfectly. The result is excellent bass in a solution that installs in about an hour.

Park Safely with a Backup Camera

If you’re having a multimedia receiver installed in your Corvette, ask about adding a backup camera. With their low seating position and relatively high rear bumper, Corvettes can make it difficult to see what’s behind your car. If you aren’t changing the radio, you can always have the rearview mirror upgraded with a unit that includes a color display for a camera.

Sound Deadening Makes Driving Comfortable

If you are using your Vette as a daily driver, then you might want to consider having the doors, floor and hatch area treated with a layer of sound deadening. This butyl material absorbs sound energy and makes driving quieter and more comfortable. If you use Bluetooth hands-free systems or a smartphone integration technology like CarPlay or Android Auto, having a quieter car will make your voice easier to be heard.

Radar Detectors and Laser Defense

Who would buy a Corvette only to drive it slowly? If you find you have a bit of a lead foot, you might want to inquire about having a radar detector and laser defense system installed. Radar detectors are available in portable units that are great for quick installation and transportation from one vehicle to another.

For the ultimate protection solution, consider a custom-installed radar detector and laser defense solution. The biggest benefit of a custom system is the availability of laser defense technology. As more and more police forces equip their officers with lidar instead of radar, you need laser shifters to help prevent tickets.

Window Tint and Paint Protection Film

Having the windows of your car tinted offers three benefits. First, tint protects your skin from the harmful effects of the sun’s UV rays. If you spend a lot of time in your car, tint can help to prevent wrinkles, blemishes and, in extreme cases, skin cancer. The same properties that protect your skin also protect the fabrics, leathers, vinyl and plastics in your vehicle. Colors won’t fade anywhere near as quickly, and plastics won’t dry out and crack.

Second, window tint is a great way to help keep the interior of your vehicle cool. Tint films such as 3M Ceramic IR and Crystalline block 97% of the sun’s infrared energy. If you live in an area that’s hot during the summer, heat-blocking window film is a great investment.

If you care about how your Corvette looks, then window tint can dramatically improve the style of your sports car. A nice dark tint can be very dramatic.

Speaking of great looks, you may want to consider having your car protected with a layer of paint protection film. Also known as clear bra, this transparent urethane film applies directly over the paint to offer a layer of protection from stone and gravel chips, bug splatter and stains from road tar. While most installations focus on protecting the front bumper, fenders and hood, other areas that deserve attention are the rocker panels, doors, mirror covers, and the area around the hatch. If you take your Corvette to the track, protecting the rear fenders from gravel and rubber chunks thrown up by the rear tires is a great idea.

Remote Starters Add Comfort

Another great option for those living in areas of the country that get painfully hot is a remote car starter. Though more commonly associated with freezing winter conditions, remote starting your car a few minutes before it’s time to go will let the air conditioning system start cooling the interior.

We know that your Corvette is your pride and joy. It’s important to protect it and keep it safe. If you’ve opted for a remote starter system, then ask about adding security features such as a high-output siren, a remote with two-way communication or a GPS tracking option that works with your smartphone. If your car is moved without your authorization, the tracking system will send an alert to your smartphone, and you can check its location and notify the police if necessary.

Dashcams Add Protection

Whether you’re worried about how the drivers around you behave, or you want to keep track of who or what is prowling around your car when it’s parked, having a dashcam installed is a great upgrade. These compact digital video recording systems install on the front windshield of your car. If there’s an accident, fraud or just something amazing happening in front of your vehicle, you’ll capture it all on video. Many dashcams can be upgraded with rear-facing cameras, and many include GPS options and built-in accelerometers.

LED Lighting Adds Fun and Safety

If you have an older car with incandescent headlights, drop by your local specialty mobile enhancement retailer and ask about high-performance LED replacements. Not only do LED bulbs put out significantly more light, but they are also more efficient. With less draw on your electrical system, the alternator will be happier. Ask the retailer you’re working with to spice up your Vette with some LED lighting. Headlight rings, such as those popularized by BMW, are a popular upgrade. Of course, multicolor LED lighting strips are a great choice for personalizing your engine compartment or footwells or for adding under-car lighting.

Upgrade Your Corvette Today

Whether you’re driving a Corvette that’s fresh off the showroom floor, the car you had in college or a custom restoration, your local specialty mobile enhancement retailer has thousands of options to update your vehicle. Drop by today and talk to them about new communication technology, a better sounding stereo system or a lighting upgrade.

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.

Speaker pods and build-outs on A-pillars are becoming increasingly common in custom car audio installations. While some of these solutions look cool, the laws of physics can work against these cosmetic efforts to degrade the performance of your car stereo system. The subject of speaker installation could (and should) fill a book. In this article, we’ll look at the benefits and drawbacks of mounting speakers in a way that’s not flush with the surrounding surfaces.

Speaker Directivity

Before we dive into our discussion of speaker pods, we need to have a quick reminder about speaker directivity. At frequencies where a sound’s wavelength is below 1.75 times the speaker cone’s diameter, sound emanates equally in all directions. Crucial to this discussion is an understanding that the description “all directions” includes the area behind the speaker.

By way of an example, let’s look at a 2.5-inch midrange driver. Let’s assume for simplicity that the cone has a diameter of 2.5 inches. As such, a 5.4 kHz tone would have a wavelength equal to the cone’s diameter. A sound with a wavelength that’s 1.75 times the cone’s diameter would have a frequency of about 3.1 kHz. As we stated, sounds with frequencies at or below 3 kHz will radiate in a spherical pattern from the speaker’s center, including areas behind the speaker.

Sound Reflections Can Wreak Havoc with Your Music

Car audio system design combines a multitude of talents. The Product Specialist designing your audio system needs to have a firm understanding of the available speaker mounting options in your vehicle to create a speaker installation solution that will meet your expectations. The technician working on your car needs to know how to optimize each speaker’s performance in those locations to deliver measurably accurate performance. There’s no doubt that perfect execution is a combination of a thorough knowledge of the laws of physics and some artistic style.

If you look at home speakers, you’ll see that each driver is typically mounted flush with the enclosure’s front baffle. This decision doesn’t happen by accident. Because sound radiates rearward from the cone, it will bounce off this mounting surface. All these reflections combine with the speaker’s energy directly radiated, and both signals eventually arrive at your ears. When the baffle is even with the speaker, the results are quite predictable and usually acceptable.

What would happen if the speaker stuck out an inch or two in front of the baffle? The sound reflecting off the baffle may not add to the sound coming directly from the driver at all frequencies. This difference in pathlengths causes cancellations at some frequencies, making the speaker system very difficult to calibrate with an equalizer.

Calculation Frequency Response

Despite the belief that delivering great sound in a car or truck is magic, it’s easy to predict the frequency where reflections can become an issue in a car audio system. Imagine if a speaker pod is sitting 3 inches in front of your car’s windshield. This location results in the sound bouncing off of the glass traveling an extra 6 inches before it combines with the energy radiated directly from the speaker cone.

If we look for a frequency where one half of a wavelength is equal to our 3-inch distance, we find that at 2.26 kHz, the sound is one half-wavelength out of phase with the original source when it sums back together after reflecting off of the glass. At this frequency, the sounds will cancel each other out. The result is a notch in the frequency response of the system. This acoustic cancellation repeats at 6.7 and 11.3 kHz. Those last two will be inaudible as comb filtering at frequencies significantly above 1 kHz is difficult to perceive because the Q is of the notch is very high.

This phenomenon doesn’t just happen with midrange speaker pods on your dash. Without some compensation, differences in sound arrival times between the left and right speakers or front and rear speakers can produce the same effect. In home audio, placing a speaker so that the driver is 8.5 inches in front of a wall will produce the 400 Hz, 1.2 kHz and 2 kHz dips you see in the image above. The same thing happens at the frequency where sound created by the speaker bounces off of the floor and combines with the sound coming straight from the driver.

If you are working with a car stereo shop to design an audio system upgrade for your car or truck, it’s not difficult to minimize the effects of comb filtering by having your speakers mounted as flush as possible with the vehicle. Where there are front-to-rear or left-to-right pathlength differences, implementing signal delay or an all-pass filter in a signal processor from a company like ARC Audio, Audison or Audiotec Fischer can dramatically improve the way your music sounds. Placing your speakers in pods away from door panels, the windshield, side windows and the dash might not be an idea that’s as good as it seems.

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.