While participating in some brand-specific online discussion groups, we often encounter the question: “Is it better to use two good subs or one great one?” Are two 12-inch KICKER L7S subs better than a SoloX? Should you opt for two Hertz Cento CS 250 S4s instead of a Mille ML 2500.3 Legend? What about choosing a pair of Rockford Fosgate P3 twelves over a single T1? There are many factors to consider, including enclosure design, output, frequency response and efficiency. Let’s dive into science and math to find an answer.

Maximum Output Level – Part 1

For many car audio enthusiasts, achieving the most bass possible from a given investment is the top priority. So, is a great subwoofer louder than two good subwoofers? Let’s use the CompVR and CompVX subwoofers from KICKER as our first comparison.

We’ll start by setting aside the total enclosure size for now. While this will become important later, let’s first model a pair of KICKER CompVR CVR124 12-inch subwoofers using BassBox Pro.

KICKER recommends an enclosure volume between 1.75 and 2.25 cubic feet per driver for a bass reflex enclosure. We’ve split the difference, using two cubic feet per driver. We let BassBox Pro suggest a tuning frequency of 33 hertz. According to the simulation, the enclosure will produce 123.1 dB, with each subwoofer receiving 400 watts of power. Remember that this SPL number doesn’t account for the vehicle transfer function, meaning the output would be higher in a car or truck.

Now, let’s switch our focus to the CompVX cast-basket 12-inch subwoofer. This driver handles up to 750 watts of power and has an Xmax specification of 19.25 millimeters compared to the CompVR’s 16.5. Let’s see if this makes up for the output difference.

In this case, the single great subwoofer cannot match the output of the two good subs when driven by the same power.

One quick note about the KICKER simulations. KICKER doesn’t specify driver inductance. For this simulation, we left that field blank. The result is a flat response curve at midbass and midrange frequencies. In the real world, that’s not how the drivers would perform in that region.

Maximum Output Level – Part 2

Now, let’s consider a similar scenario with Rockford Fosgate subwoofers. This question initially prompted the article—are two P3 subwoofers better than a single T1? Let’s simulate this and see which setup produces more SPL.

We’ll start by simulating two P3D2-12 12-inch subwoofers in a 3.58 cubic foot enclosure tuned to 40 hertz. The Box Advisor on the Rockford Fosgate website suggests this exact design. Well, it suggested half that volume per driver, but the results are the same.

As the graph shows, this enclosure delivers a solid punch at 50 hertz. With 1200 watts of power, the peak output is predicted to be 125.7 dB SPL.

Next, let’s examine what a single Power Series T1D4-12 can do in its recommended enclosure.

The Box Advisor recommends a 1.75 cubic foot enclosure tuned to 33 hertz for the single T1 subwoofer. Based on the response graph, we agree with this design. The enclosure predicts an output of 119.1 dB SPL when driven by 800 watts of power.

Like in car engines, there is no replacement for displacement when attempting to produce maximum torque. Subwoofer cone area is crucial for maximum output in car audio systems.

Low-Frequency Extension Versus Enclosure Volume

What if your goal is to achieve the most low-frequency output possible from your subwoofer system? Many of the subwoofer upgrades we see perform better at upper bass frequencies due to large drivers being installed in undersized enclosures. If deep bass is your priority, moderately sized subwoofers in relatively large enclosures are the way to go. To illustrate this, let’s compare two Hertz subwoofer options at 30 Hz.

We’ll begin with a pair of 10-inch Hertz Cento CS 250 S4 subwoofers in a 2.5 cubic foot enclosure tuned to 30 hertz.

This system produces 113.9 dB SPL at 30 hertz. Now, let’s look at a single, better subwoofer in a larger enclosure—the Mille-Series ML 2500.3 Legend.

At 30 hertz, the single ML 2500.3 Legend delivers 114.5 dB SPL. Though the difference is slight, the difference would be very noticeable. Letting a single driver “breathe” in a larger enclosure maximizes low-frequency output.

Car Audio Subwoofer Sound Quality

This is where things become more complex. Sound quality and accuracy are not as tightly related to frequency response as you might think. We agree that a poorly designed enclosure with a narrow-band spike will sound inferior to a system with a broad response curve. However, a subwoofer in any high-end system should be equalized to a target response curve. Thus, any two enclosures equalized to the same curve will sound similar, though not identical.

Driver design features affect harmonic and intermodulation distortion in terms of accuracy. For instance, the Mille Legend subwoofers include an aluminum shorting ring that reduces inductance and, thus, improves midbass response. The Legend subwoofer’s inductance is specified at 1.05 millihenries, while the Cento subs measure 3.33 millihenries. Lower inductance means more midbass output, making blending the subwoofer’s output with midbass drivers easier.

Rockford Fosgate incorporates a similar feature between the P3 and T1 subwoofers. The T1 and higher subwoofers feature an Inductive Damping Heat Sink (IDHS) that acts like a shorting ring, reducing inductance. The T1’s dual four-ohm inductance is 2.4 millihenries, while the P3 is rated at 6.94. As a result, the T1 delivers tighter, punchier, and more accurate midbass.

Even without features like inductance management, less expensive subwoofers are still a great choice. However, upgrading to better products often provides more than increased excursion and power handling.

From a sound quality and musical accuracy perspective, the Mille and Power-Series subwoofers stand out as clear winners.

Space for Bass

As we’ve discussed in previous articles, producing deep bass requires that your subwoofers have adequate space. Trying to fit two 10-inch subwoofers in a one-cubic-foot enclosure won’t work as well as using a single eight-inch driver in a bass reflex design in the same volume.

Here’s a perfect example of optimizing an enclosure for subwoofer duties. A single 8-inch Audison APS 8 D driver in a one-cubic-foot vented enclosure delivers more output from 16 to 44 hertz than two 10-inch drivers in the same space. While two 10s might offer more output above 50 Hz, we prefer deeper extension to 35 Hz for a well-rounded sound and a little rumble.

Subwoofer Enclosure Simulations To The Rescue

In conclusion, if your goal is to maximize SPL, using two good subs will generally outperform a single sub. However, a single subwoofer in a larger enclosure may be the better option for low-frequency output. A subwoofer with advanced performance features will offer superior results for the most accurate and detailed bass.

If you’re curious about the best bass solution for your vehicle, visit a local specialty mobile enhancement retailer. They can measure the available space and simulate different subwoofer options to achieve your desired performance. They’ll also explain product features and how they improve sound accuracy and detail.

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.

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.