Having music playing while driving is not only entertaining, but it can be very relaxing. Enjoying your favorite songs while stuck in traffic or on a long drive can help time pass much quicker. We recently received a question from one of our readers about the best way to manage a large music collection. Specifically, they wanted to know what features different radios offer that make accessing a specific artist, album, or track easier. This is a great question, so let’s explore the answers.

Radio-Specific Storage Limits

So, what would be considered a large music collection? One BestCarAudio.com team member loves collecting music. He has over a terabyte of music on his home server, comprising almost 65,000 songs. That’s way more than would ever be reasonable to take on the road with you.

In fact, most modern car radios can’t handle that many tracks. The Sony XAV-9000ES, for example, allows up to 25,000 tracks to be read from a USB storage device. The folder structure itself limits other brands. For example, we looked at the specifications for a Kenwood radio, which allows for up to 999 files per folder, 9,999 folders, and a maximum folder depth of eight layers. We also checked the owner’s manual for an Alpine multimedia receiver. The particular unit we checked lists a limit of 10,000 files and folders, including the root folder. We’ve seen marine radios with a limit of 999 songs and a maximum of 255 folders.

The takeaway is that you must research this specific aspect of the radio you are considering before purchasing. Many consumers assume their radio will recognize all their tracks and play almost anything. If you forget to check, please don’t complain about it afterward. The manufacturers can’t change these limits; they are often based on the amount of memory connected to the radio’s microcontroller.

Modern Factory-Installed Infotainment Systems

For real-world testing, we copied 13 GB of music onto a 64 GB SanDisk USB memory stick. There are 27 folders containing 683 files. This wouldn’t be considered a massive amount of music, but it will help us determine how different source units handle finding a specific track.

We connected the memory stick to the infotainment system in a staff member’s 2025 Mazda CX-70 Turbo Signature, equivalent to the US Premium Plus model. The radio displayed an error message saying it didn’t support the connected device. It turns out that the radio in this brand-new vehicle can’t read USB memory sticks formatted with exFAT. Storage devices must be either FAT or FAT32.

Panasonic manufactures the “radio” in this vehicle, Automotive Systems. Bose provides the amplifier and speakers. This is referred to as a silver box solution. The radio itself has no integrated interface. Visteon manufactures the screen on the dash. The “radio” has the AM/FM tuner, satellite radio receiver, GPS receiver, and the inputs for the pair of USB-C ports in the center console. The radio sends a data stream to the Bose amp under the passenger seat, which then handles the signal processing and drives the speakers and subwoofer.

We tried again after searching for an old 8 GB stick and hunting down a USB-C to USB-A adapter. Now, the radio struggled with the file formats. It wouldn’t play 88.1 kHz, 24-bit FLAC audio files. Remember what we just said about ensuring the radio will play what you want? Yeah, we figured that out by trial and error. After a third trip back to the computer and some work in Adobe Audition, the content was finally working.

Mazda CX-70 Infotainment System

So, how does the Mazda handle navigating extensive music collections? You can search through folders pretty easily. It’s just a few presses on the control wheel in the center console to select the Folder option. If you want to search for a specific track alphabetically, you can choose the Library option, then select from Artists, Albums, Songs, Genres, Composers, or Playlists. From there, you will be presented with a list of options based on your chosen criteria. You can toggle to the right, scroll through the alphabet, and select a song. It’s a lot of button presses, but it works well.

Next, we tested a 2023 Nissan Rogue with Bose speakers and amplifier. Just for clarity, Bose doesn’t make radios. Robert Bosch GmbH manufactures this particular unit. We connected the SanDisk stick to no avail, so it was back to the old 8 GB stick. If you want to carry around a lot of music on a USB drive, support for a large drive will be the limiting factor.

With our little USB loaded with a few hundred songs, we set off to run some errands. We recalled seeing some voice recognition features outlined in the owner’s manual—yes, some of us read the manual. We pressed the voice button and asked the system to play a song. It informed us that it couldn’t because of how our smartphones were connected. If you connect your smartphone using Apple CarPlay or Android Auto, it appears to override the built-in voice commands.

Sadly, our USB listening experience took a turn for the worse. After about 30 minutes of driving, the radio encountered issues updating the screen. The results are shown below. It seemed to work fine the next day, but we didn’t play it for long.

Sony Radio Music Management

We checked with our Editor-in-Chief to see what he had on the test bench. He’d just unpacked a Sony XAV-AX3700 multimedia receiver, so we asked him to try the same test on that. With a large memory stick full of music, the Sony could display all the tracks he’d copied and had no problem reading the exFAT memory stick or playing the high-resolution FLAC audio files. Specifically, the XAV-AX3700 will play FLAC, ALAC, DSD, and WAV high-resolution audio files.

Sony makes it very easy to choose songs from different folders when it comes to finding songs. Navigating to the root folder and selecting sub-folders was straightforward. It would be wise to remember this when copying files to the drive. Putting 200+ random songs in a folder likely isn’t the best strategy. Sorting them by artist, album, or genre while copying will make finding what you want easier when driving.

Smartphone Music Storage

Now that we’ve examined a few radio behaviors regarding music stored on a USB memory stick, let’s consider using a smartphone as your music storage device. Apple’s Siri and CarPlay, Google Assistant, and Android Auto make it incredibly easy to access music stored on the phone.

Let’s say you have purchased eight Aerosmith albums. These will likely include Permanent Vacation and Pump. If you want to listen to “Dulcimer Stomp,” activate the voice recognition feature and say, “Play ‘Dulcimer Stomp’ by Aerosmith.” The system will find the track and start playing it automatically. You can also ask it to “play the album Pump by Aerosmith.”

Cloud-Based Streaming

If you don’t have the song stored on your phone, another option is to subscribe to a service like Spotify, YouTube Music, or Qobuz. For about USD 11.00 a month, you can access music from virtually every professional recording artist you want. These services also offer discounts for two users or even family plans that allow up to six users. Spotify and YouTube Music also provide discounts for students.

Is streaming as good as playing a FLAC or WAV file on a USB stick? If your service offers a high-quality stream, the tracks will sound very good over a wired connection between your phone and the radio. However, any compression will remove subtle details. You might hear the difference if your car’s audio system is good enough. With the basic audio quality settings in Spotify, for example, you can detect a loss in quality on a basic six-speaker factory-installed audio system.

Test Your Music Collection Before Buying

What’s the takeaway from our testing? At first, the voice command capabilities of the Mazda seemed promising. Unfortunately, they didn’t work as expected. After that, the system required too many button presses and toggles to reach what we needed. In contrast, the Sony was simple, intuitive, and—best of all—worked seamlessly with our large memory stick and music files.

If you have an extensive music collection and want to enjoy it in your vehicle, always test the interface before making a purchase. This applies not only to aftermarket radios but also to new cars. Yes, we would absolutely avoid buying a vehicle if its infotainment system was difficult to use. You may recall that Ford CEO Jim Farley recently apologized for issues with their Sync infotainment system—this is the second time Ford has had to address these problems.

When shopping for a new car radio, visit a local specialty mobile enhancement retailer. Bring a USB memory stick or your phone and connect it to the radio you’re considering. Ensure it functions the way you want. If not, try a different model or even a different brand.

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 short while ago, while testing an amplifier’s maximum power output, we observed how significantly the power increased with higher supply voltage. This observation made us realize that we’ve never thoroughly examined the relationship between a vehicle’s battery voltage and a car audio amplifier’s maximum power output. It’s time to address that.

Why Does Battery Voltage Matter to Amplifier Power Production?

Today, most car audio amplifiers use loosely or completely unregulated power supplies. As a result, the positive and negative voltages available to feed the output devices become a fixed multiple of the supply voltage. For instance, if the battery rests at 12.5 volts, an amp might generate 500 watts. However, if that voltage increases to 14.4 volts, the amp might produce 600 watts.

Maximum Supply Voltage Limits

To ensure product reliability, companies typically set a maximum voltage limit, which prevents the amp from producing excessive power. But why is this important? All car audio amplifiers convert some of the power they consume into heat. The heatsink and cooling system must dissipate a specific amount of heat energy to control the amp’s temperature. Notably, as the power level increases, the heat that needs to be expelled also rises because amplifier efficiency remains constant at maximum power.

For example, consider an amplifier that is 80% efficient and produces 500 watts of power; it converts 125 watts into heat. If provided with more supply voltage, the amp might produce 600 watts, requiring the heatsink to manage 150 watts of heat. This is likely manageable. Now, if the amp could produce 700 watts at 16 volts, it would have to manage 175 watts of heat—a significant increase from 125 watts. Unless the chassis is massive or there are numerous 0.3 watts, stepping from 14 to 15 volts increased the output by 56 watts.

Why does the power level increase more with each voltage jump? Power is proportional to the square of the voltage divided by the load resistance, according to the formula V^2 ÷ R. Thus, a slight increase in voltage results in a moderate power increase.

How Can You Maximize Voltage to Your Car Audio Amplifier?

Without resorting to unreliable aftermarket alternators or maintaining battery banks, the simplest way to ensure your amplifier receives all the power your battery and charging system produce is to have the technician working on the vehicle install a high-quality, all-copper power cable large enough for the amplifier’s current requirements.

In a car audio installation requiring about 15 feet of power wire, we suggest the following cable sizes: 10-AWG for loads up to 22 amps, 8-AWG for loads up to 35 amps, and 6-AWG (if you can still find it) for loads up to 56 amps. For loads up to 88 amps, a 4-AWG cable suffices. If you must pass 218 amps of current over 15 feet, a cooling fans, this difference means the amp won’t run as long before overheating.

Moreover, increased supply voltage presents another issue: the maximum voltage ratings on components. For example, most amplifiers include filtering capacitors on the power connections, which might be 16-volt, 1000 μF units. To accept more than 16 volts, the manufacturer might need to upgrade to 25-volt capacitors. These higher-voltage capacitors are larger and more expensive. Additionally, diodes and other protection circuitry components might need upgrades to handle higher operating voltages, further increasing costs with little performance gain under normal conditions.

Testing Amplifier Maximum Power Output

We decided to test this further using a Rockford Fosgate Punch-Series P300X2 two-channel, full-range amplifier. Recently, we re-tested several amps with our new power supplies, and although this amp wasn’t on the schedule, we decided to test it anyway.

We set up the amp and connected it to a bank of 300-watt, low-inductance ceramic power resistors configured for a four-ohm load. Initially, we set the power supply to provide 16 volts to the amp, just under its maximum upper voltage limit. We then increased the signal to the amp until the output signal was within 1 to 1.05% THD+N. Afterward, we decreased the supply voltage and signal, measuring power output at 0.5-volt intervals until reaching the minimum power output of the power supplies. To comply with the ANSI/CTA-2006-D car audio amplifier power measurement standard, we measured power at 14.4 volts instead of 14.5 volts.

The difference in power output between 11.25 and 16 volts is substantial, as the chart shows. With an increase of 4.8 volts, the amp nearly doubled its power output. We simultaneously captured current draw measurements to calculate efficiency. This class-BD amplifier remained between 67% and 68% efficient throughout the entire range of measurements.

In our full Test Drive Review of the amplifier, our original maximum power rating was 360.1 watts at 14.15 volts. This time, we measured 398 watts at 14.4 volts. While you likely won’t hear the 38-watt difference, it’s worth noting that an amp rated to produce 300 watts made 400 watts. Rockford Fosgate fans already know they’re getting more than they paid for.

Plotting Amplifier Power vs. Battery Voltage

Let’s examine that chart as a graph.

Interestingly, while the relationship between the maximum power an amp can produce and the supply voltage appears linear, it’s not. The increase from roughly 12 to 13 volts yielded 48.3 more watts. The jump from 13 to 14 volts added 50-AWG power cable is necessary. For up to 289 amps, use a 2/0-AWG cable. Finally, if you have a massive amplifier or multiple smaller amps, 4/0-AWG cable over 15 feet is suitable for 422 amps. While these cables can undoubtedly pass more current, the voltage drop for these calculations is set not to exceed 0.35 volts over the entire length. Don’t forget to account for losses in the return path, which, if the cabling size and length are the same, would result in a 0.7-volt drop.

The Math on Power Output Versus Power Wire Size

To illustrate more clearly, for our 300-watt amplifier, losing 0.7 volts at the power terminals reduces the output by around 35 watts, roughly 10% of the rated power. If you think skimping on a power cable is a good idea, here’s the math to prove otherwise.

Consider this amp’s maximum theoretical power output with 15 feet of 10, 8, and 4-AWG cables for power and ground connections. Assuming the electrical system could maintain 14.4 volts at the battery, a 15-foot run of 10-AWG power and ground cable would reduce the voltage at the amp to 13.11 volts. With 8-AWG cables, the voltage would drop to 13.59 volts, while using 4-AWG cables reduces the drop to 14.08 volts. If you splurged on 0-AWG cable, the drop across the cable would result in the amp receiving 14.27 volts. You might have expected less drop across 30 feet of 0-AWG power wire, but that’s not the case.

If you’re curious why Rockford Fosgate overrates its amplifiers, it’s because most installations lack adequately large power and ground cables. If you waste a volt across the power wire, in the case of the Punch P300X2, the maximum power output drops by about 10%. You’ll still get all the power you paid for, but not as much as possible. Therefore, investing in larger power and ground cables is more cost-effective than buying the next-size car audio amplifier in a series.

Don’t Starve Your Car Audio Amp for Voltage

Even after an average of three and a half decades in the mobile enhancement industry, none of our team members recall anyone publishing similar data. It may have happened, but we haven’t seen it. This data highlights the critical need for adequately sized power cables. If you’re considering upgrading your car audio system with high-power amplifiers, ensure the wiring is sufficient to maximize the power output from your chosen amp. Visit a local specialty mobile enhancement retailer today. Choose an amplifier that sounds great and is efficient, then ensure it is installed with the largest power and ground cables you can afford.

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.