In recent years, car radio manufacturers have added simultaneous dual Bluetooth phone support. At a quick glance, the ability to connect two phones to a single radio seems like a great solution for a family where the parents will be travelling in the vehicle at the same time. With that said, depending on the brand of radio you choose, that’s not necessarily how dual Bluetooth or dual phone support works. Let’s look at this subject with a little more detail.

Phone Pairing Options

For many years, car radios have offered the ability to pair with at as many as five Bluetooth devices. The pairing process involves establishing an initial connection between your radio and your phone. In most cases, this step involves going into the Bluetooth menu of your phone and looking for the radio. Years ago, this was a complicated process that involved putting the radio into “paring mode.” Now, the Secure Simple Pairing (SSP) interface makes this process much simpler and eliminates the need to go through complicated steps on the radio.

When the radio boots up, it goes through this list of paired devices and searches for them to re-establish a Bluetooth connection. Depending on the radio, users can set a priority so that a preferred device is always connected first. As an aside, the radio may check the contacts in the phone and automatically download new names and phone numbers right after the connection is established. If you’re making calls using the phone list on the screen, this is a great feature.

Dual Phone Support Options

There are two types of “dual phone support” systems on the market. The first type allows two devices to share the hands-free capabilities of the radio. As such, the system allows the driver to answer calls received on either device by pressing the Send/End button on the radio face or the steering wheel.

The second type of “dual phone” connectivity pairs one phone as a hands-free device and a second phone as an audio source to be used for playing music. The driver may not be able to answer calls on the second device, but can stream from such sources as Pandora, iHeartRadio, Spotify or Apple Music.

Let’s be clear: Two phones are always better than one. We are simply establishing a distinction between the way different source units work.

Always Try a New Radio Before You Buy It

If there’s ever been a message that’s crystal clear to our readers, it’s that you should try the radio you want to buy on a display board at your local specialty mobile enhancement retailer before it’s installed into your vehicle. If support for the simultaneous use of two phones is important, bring both phones and pair them both to the radio. Cycle the power to the radio to see how the phones reconnect. Test to see how the radio responds when a call is received on each device. Also check to see how the radio behaves if only one of the two phones is paired. Since the firmware on radios is often updated at least once or twice after being launched, ask the product specialist you are dealing with if everything is up to date.

You may want to check out BestCarAudio.com’s 2020 Car Radio Buying Guide for a few more items you might want to check on the display before buying. There’s even a handy downloadable checklist.

A Quick Reminder about Bluetooth Terminology

Most consumers think Bluetooth is a wireless phone connectivity solution. While this is true, Bluetooth is actually a low-power, short-range digital communication standard that was created to replace serial cables. How Bluetooth is implemented varies by device. For example, controllers for your Xbox or PlayStation use Bluetooth to communicate with the console to transmit button and joystick commands and receive instructions to activate the vibration functions.

Of course, wireless computer keyboards and mice use Bluetooth. The Apple Pencil that works with the iPad uses Bluetooth. Other applications for Bluetooth include communication between street lights that lets them turn on or off at the same time. There are also car alarms that communicate with a siren under the hood using Bluetooth instead of wires, and smartphone remote control options that let you unlock or remote-start your vehicle using your smartphone. The remote that comes with an Amazon Fire Stick also uses Bluetooth.

Upgrade Your Car Radio for Dual Phone Support

If you find there are often two of you in your vehicle at the same time, and both want to be able to receive phone calls or serve as the disc jockey for your next trip, drop by your local specialty mobile enhancement retailer and test drive a new car radio with dual Bluetooth phone support.

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 subwoofers or speakers, they need to be installed in a correctly sized enclosure to deliver accurate performance and useful bass extension. Speakers are complex devices that rely on their suspension components and the enclosure they are installed in to determine how they perform at lower frequencies. When the product specialist you’re working with is designing your sound system, he or she needs to balance many criteria to ensure you get the sound you want. In this article, we’ll look at the importance of installing subwoofers in enclosures with enough internal air volume.

How Enclosure Volume Affects Speaker Performance

Every speaker of every size is affected by the volume of air in the enclosure behind the driver. Even large tweeters are often designed with cavities behind the diaphragm that can change their performance down near the crossover point. For this article, we’ll focus on midbass subwoofers and look at several real-world examples and application comparisons.

Lately, we’ve seen several instances where multiple subwoofers have been crammed into incredibly small enclosures. The most common example of this is in pickup trucks. The space under the rear seat of your truck is limited. In most cases, there is less than 1.6 cubic feet of air space for the woofers to work with. Physically, you can easily install a pair of woofers, and some custom solutions allow for as many as four drivers under the rear seat. Let’s look at how a popular shallow-mount subwoofer like the JL Audio 10TW3-4 behaves in this space.

Let’s start with a single subwoofer in 1.5 cubic feet of space. Our enclosure simulation software predicts a -3 dB frequency of 45.95 Hz and a total system Q of 0.483. This low Q tells us that it is likely too large of an enclosure for this driver. Thanks to the impressive excursion capabilities of the TW3 subwoofers, things will work fine.

Now, let’s say we want more bass. The seemingly logical move would be to add another subwoofer, right? If we ask our technician to install two drivers in this 1.5-cubic-foot enclosure, the -3 dB point raises to 47 Hz, and the Q increases a bit to 0.643. Based on the shape of the graph and those numbers, this combination looks like a great solution.

Thankfully, JL Audio knows how to design a subwoofer to work in a small enclosure. The response of these systems is smooth. Now, let’s double down again and see what happens when we use four woofers in this 1.5-cubic-foot enclosure. Our software says the -3 dB point is now 50 Hz, and the Q is 0.738. Both are great numbers.

With that said, we need to look carefully at where the increase in output happens. The single-driver solution predicts an output of 106.4 dB, the dual driver system predicts 109.4 dB, and the quad-sub solution says 112.4 dB at 60 Hz. As science indicates, that’s a 3 dB increase for every doubling of cone area for a given power rating. But does that mean more usable bass? Let’s look at what happens down at 35 Hz. The single driver enclosure is predicted to produce 102 dB of output. The dual-driver enclosure should produce 104.4 dB. Finally, the quad-driver enclosure should offer 105.9 dB at 35 Hz. We saw a gain of 2.2 dB from the single to dual increase and only 1.5 dB from the dual to the quad system.

Why? Because the volume of air in the enclosure limits cone excursion at lower frequencies. More specifically, the ratio of the available airspace to the driver’s equivalent compliance (this specification is called the Vas) decreases as the effective enclosure volume decreases. In this example, we get more upper bass around 60 Hz with four subwoofers, but beyond two, we don’t get much more deep bass.

Extreme Cases Result in No Bass

As we mentioned, JL Audio did a great job designing its TW-Series subwoofers to work in very small enclosures. Not every subwoofer on the market is designed this way. Balancing the design of a subwoofer trades efficiency for low-frequency extension. Let’s look at an example that doesn’t work. In this case, we have a very shallow 8-inch driver that’s been crammed into a tiny enclosure in the door of a car. The enclosure has a net volume of 0.15 cubic foot. The enclosure fits, but does it work?

As you can see, this is a disaster. There’s a huge peak at 450 Hz and barely any output below 100 Hz. Given that most subwoofer systems operate below 60 Hz, this doesn’t work. Oh, the system Q is 1.79. Target Q-factors are typically in the 0.6 to 0.95 range. This would sound unpleasant in every way.

Does this make this a bad subwoofer? We modeled the driver in a 1-cubic-foot enclosure and it still didn’t make much bass. It’s clearly designed for an infinite baffle application.

A better solution for this ultra-small enclosure would have been a high-quality 6-inch subwoofer. The graph below shows the aforementioned 8-inch sub and a 6.5-inch sub in the same 0.15-cubic-foot enclosure. The 6.5-inch sub is 12 dB louder at 40 Hz.

What About Vented Enclosures?

Let’s circle back to the beginning and look at how a vented enclosure might change our subwoofer system performance. We’ll remind you that we want the subwoofer to be able to produce lots of energy between 30 and 60 Hz for deep bass.

The graph below shows our 1.5-cubic-foot truck enclosure’s performance with subwoofers in sealed (acoustic suspension) and vented (bass reflex) designs.

As you can see, between 20 and 50 Hz, the single subwoofer in a vented enclosure is louder than four subs in a sealed design. At 25 Hz, the vented design can produce 106.9 dB, whereas the four drivers are only making 100.7 dB. That’s a HUGE difference! The vented enclosure would cost less, sound better and require less power from your amplifier to recreate the lowest notes in your music. Your installer will also have an easier time blending the system’s output with the midbass speakers in your truck because there’s less of a peak in the response at the crossover point. It’s a complete win-win!

Picking the Right Subwoofer Solution

When it comes time to shop for a subwoofer upgrade for your car or truck, be sure to ask the specialty mobile enhancement retailer you are working with about your options in terms of the enclosure. It’s pretty common to see a single subwoofer in a vented design deliver significantly more output than multiple drivers in a sealed enclosure.

Lead-In Image: Thanks to Jim Skaggs at the team at MTI Acoustics for the lead-in photograph.

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.