If you’ve looked at an amplifier installation kit, you’ll see it comes with about 17 feet of power wire, a shorter length of ground wire and a fuse holder. The intent of this fuse holder is for it to be installed as close as possible to the positive battery terminal. As for the fuse size, should it be the same as the fuse in your amplifier? Likely not. Read on to learn why.

Overcurrent Protection Devices

When it comes to overcurrent protection devices in car audio systems, there are two main contenders: circuit breakers and fuses. Our extensive testing has revealed that circuit breakers, while effective, tend to waste a bit more voltage than their fuse counterparts. Moreover, there’s a risk of circuit breakers not opening when an overcurrent condition occurs. That’s why we strongly advocate using ANL and Mini-ANL fuses to safeguard our vehicles.

A fuse is a simple device in that it’s a piece of metal with a specific area through which all the current going to the load passes. We know that all conductors, be they copper, aluminum or an alloy, have a specific resistance for a given area. As such, fuses are sized so that their resistance will cause the fuse to melt when the current flowing through the device exceeds a certain threshold. Once melted, the current no longer flows to the load.

Why Do We Need a Fuse at the Battery?

When a local mobile enhancement retailer upgrades our vehicle with an amplifier, they run a large-gauge power wire to the battery’s positive terminal and ground the amp’s negative terminal to the chassis. In some cases, especially in vehicles built with aluminum or adhesives, the negative terminal must also go to the battery. The purpose of the fuse is to protect the battery from an overcurrent condition.

What could cause an overcurrent condition in the amplifier power wire? Well, if the wire comes loose from the amp and drops onto the vehicle’s body or touches the negative terminal, a lot of current will flow. Without a fuse, the wire will likely heat up quickly, the jacket will melt, and there could be a fire. Likewise, if the power wire is run across a sharp edge like a hole drilled in a piece of metal, that could cut into the wire and potentially short the wire to the ground. If you’re in an accident where the side of the vehicle is crushed, the power wire might be pinched by the folded metal and be shorted to the ground. Any of these conditions will result in a mess if no overcurrent protection device is installed at the battery.

Why Are There Fuses in Car Audio Amplifiers?

Contrary to popular belief, a fuse in a car audio amplifier isn’t to protect the amplifier. Fuses are there to protect the vehicle battery in the event the positive and negative power connections to the amplifier are reversed. Because of how the switching devices in a power supply work, there will be a short circuit if the power connections are reversed. With no protection device, the switching devices will explode violently. The fuse or fuses are not going to prevent damage to the amp if a single switching device fails during regular operation.

So, how are the fuses on an amplifier chosen regarding their current capacity? They need to be large enough to ensure that the amplifier can produce its full rated power without them blowing. We’ve tested a few amplifiers that will pop the included fuses when all channels on the amp are driven at full power into their minimum impedance with test tones. This scenario is different from playing music, so it’s not an issue.

What Size Fuse at the Battery?

To recap, the fuses on the amp protect it from catastrophic failure in the event of a wiring accident. What size should the fuse be at the battery, and what’s its purpose? The fuse at the battery protects the power wire. As such, it should be sized to prevent the wire from carrying more current than it can handle without overheating.

We know there are many official wire sizes, and that wire should be made of copper. However, we also know that there are many mystery wire diameters and that many inexpensive amplifier installation kits use copper-clad aluminum wire. Unfortunately, we don’t know how much aluminum is in these kits, so an educated assessment of the wire resistance is impossible.

The ANSI/CTA-2015 standard for car audio power wiring suggests we should have no more than 0.25 volt of drop across the wire. This will, of course, be for steady-state current requirements. Nevertheless, we’ll use it as a reference for our calculations. In terms of power wire length, we will provide data for 10- and 16-foot runs. Ten feet is likely adequate to connect an amplifier mounted under a seat to the battery under the hood. Sixteen feet is usually enough to mount an amp in the trunk. The table below shows the maximum current the wire can pass for the given lengths, resulting in a roughly 0.25- to 0.26-volt drop.

As you can see, the maximum current decreases with length. This is because the resistance increases, which results in more voltage drop.

While the above chart is logical, it is perhaps too optimistic about the reality of modern car audio system design. We know of many systems where a run of 4 AWG wire is subjected to well over 100 amps of current. Sure, the amp won’t see the full battery or alternator voltage, but the cable doesn’t melt and catch fire. So, here’s our recommended maximum fuse size chart.

Why Not Use a Smaller Battery Fuse?

Could you use a smaller battery fuse than we’ve recommended? Absolutely. However, there’s an interesting reason why you might not want to. As mentioned, fuses have a specific resistance that causes them to blow when a specific amount of current passes through them. Fuses rated for larger amounts of current have less resistance. As such, less voltage drops across the fuse, and more is available to feed the amplifier. More voltage will result in the amplifier being able to produce more power before it starts clipping.

Fuse Location

Decades ago, the International AutoSound Challenge Association established a rule that said the fuse in a car audio system should be within 14 inches of the battery. Sadly, many people took this to mean that the fuse should be 14 inches from the battery. In reality, the fuse should be as close as possible to the positive terminal to provide maximum protection. Having a fuse 10 to 12 inches away might not provide adequate protection in a front-end collision.

We like the idea of fuse holders that are integrated directly into battery terminals. This design provides the most protection possible should something go wrong.

Ensure that Your Car Audio System Is Protected

While most professional car audio installers know how to adequately protect your vehicle from damage because of a short-circuited power wire, some might need guidance. Before you let anyone work on your vehicle, discuss what type of overcurrent protection device will be used and where it will be installed. A proper battery fuse is crucial to preventing additional damage should something go wrong.

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.

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If you’re looking for the best performance from your car audio system, the limitations of Bluetooth sound quality might be holding you back. Even if you’re streaming lossless or high-res files from Tidal or audio files stored directly on your phone, wireless connections to a car audio source unit are often optimized for bandwidth, not audio quality. Let’s make some simple measurements to demonstrate what happens when you’re using Bluetooth or Apple CarPlay to connect to your radio.

Some Background on Bluetooth Audio Streaming

As we’ve explained previously, Bluetooth is not an audio streaming solution. Specifically, it was designed as a low-power, short-range wireless communication solution that would replace serial cables. Imagine walking up to a printer to get a hard copy of a document rather than having to connect a serial, parallel or USB cable. Though initially developed in the mid-’90s, Bluetooth communication didn’t become popular until around 2004. Now, Bluetooth is everywhere. We use it to connect the controllers to our gaming systems. We use it to connect a mouse or keyboard to a computer. Of course, streaming music from a smartphone or media player to a car radio is also common.

Bluetooth uses different sets of instructions, called profiles, to perform different tasks. For instance, when your smartphone connects to your car radio, it might use the Phone Book Access Profile (PBAP) to download your contacts into the radio. The Hands-Free Profile (HFP) allows the microphone in your radio to send audio out to the person calling you and let their voice play through the car speakers.

Pertinent to this discussion, the Advanced Audio Distribution Profile (A2DP) is used to stream music to the radio. The devices also use the Audio/Video Remote Control Profile (AVRCP) to allow the radio to change tracks and display song and artist information. A lot happens when you connect your phone to your radio wirelessly.

Within A2DP, there are several different CODECs. A CODEC is software that compresses and decompresses data for transmission across bandwidth-limited connections. You can think of a CODEC as a real-time file compression or ZIP process like we use to send large programs over the internet. The data is analyzed and compressed, then transmitted. The receiver decodes the data and attempts to restore the original information. This is where we lose some quality and accuracy. CODECs, like audio formats like MP3, are inherently lossy. This means you don’t get an exact replica of the original file out of the system. It’s pretty good, but it’s not perfect.

For this article, we’ll use an Apple iPhone and the Sony Mobile ES XAV-9000ES multimedia receiver we recently tested to evaluate audio streaming performance. Apple smartphones are limited in their streaming capabilities as they only support the SBC and AAC CODECS. The Low Complexity Subband Coding (SBC) CODEC is basically the industry standard. Almost all streaming-capable Bluetooth devices will have SBC built in. The Advanced Audio Coding (AAC) CODEC offers better performance than SBC. It’s worth noting that Apple has not adopted Qualcomm’s aptX or Sony’s LDAC, both offering even better performance. If you have to stream audio, an Android-based smartphone is a better-sounding choice. Nevertheless, we’ve got what we’ve got, so let’s see how it performs.

Bluetooth Audio Testing Criteria

When it comes to audio playback, the most crucial criterion is frequency response. Changes to any part of the amplitude of our music can easily be perceived as detrimental. As such, we created a four-minute white noise track. We’ll play this from the phone and then analyze the radio output to see how the stream affects the quality.

Next, we want to quantify accuracy. The most straightforward test is to play a single-frequency test tone and analyze the radio’s output to see whether it added any unwanted harmonic content. We’ll use a 1-kHz test tone for this evaluation.

Lastly, we’d like to measure intermodulation distortion using the CCIF standard. I’ll fully admit that I wasn’t sure whether this test would be possible, as I didn’t know whether the radio would reproduce audio information up to 20 kHz. As such, I created a similar test with tones set to 10 and 11 kHz. Any sidebands and products will be very visible.

Loading the tracks onto the iPhone made me want to bathe with a porcupine family. As much as I enjoy some parts of the Apple ecosystem, using iTunes to load music onto the phone when Android devices are as simple as copying and pasting is infuriating. Ultimately, I used a player called Onkyo HF Player. It was easier than iTunes and supports high-res files. We kept all our test files to 44.1 kHz sampling rates with 16-bit depth.

Bluetooth Audio Quality Measurements

I started by playing the test files directly from the USB memory stick. The Sony is an excellent source unit, and the results are very good for a radio of this caliber.

In terms of frequency response, the 44.1-kHz test track was rendered with smooth response past 20 kHz, just as we would expect for a radio that supports high-resolution audio.

Next, I played the 1-kHz test track. Just as when I reviewed this radio, the performance was excellent, exceeding the limits of the test track itself. Our calculated total harmonic distortion based on the second through fifth harmonics is an impressive 0.0014%, or -97.3 dB.

Finally, we have our custom intermodulation distortion track. It’s tricky to turn this information into a single value, as there are two pieces of information we want to extract. First, we want to look at the amplitude of the f2-f1 frequency. In our USB-based measurement, we can see that 1 kHz is at a level of -93.65 relative to the two test tones at 6.47 dBV. This alone works out to an IMD of 0.0021%, which is very good.

Next, we want to look at the amplitude of the sidebands adjacent to the 10- and 11-kHz tones. The 9- and 12-kHz tones are somewhat high at -66 dB below the reference signal. The third-order sidebands are at -72 dB, and the fourth is at -85.5 dB. If we add these amplitudes and compare them to the reference, we get an IMD of 00776% or -62.2 dB. This isn’t terrible.

Bluetooth Streaming Audio Test

Now, let’s repeat the test by playing the same tracks on the iPhone using the Bluetooth connection to the radio. First, we’ll check the frequency response with the white noise track.

Though subtle, the wireless connection now excludes audio information above roughly 19 kHz. This is still pretty good, and most importantly, the information below remains ruler-flat.

Next, we have the harmonic distortion evaluation with our 1-kHz test tone.

Here, it’s clear that a lot of unneeded information has been added to the playback. It’s not a disaster, as the overall amplitude is fairly low. The harmonic content is -75 dB below the fundamental frequency, equal to 0.017% THD. In short, this transforms the high-end Sony radio performance into a regular consumer-grade product. Based on our listening tests using Bluetooth connections, this jibes with what we’ve experienced.

Finally, let’s look at the intermodulation distortion performance.

Once again, we can see that a lot of garbage has been added on either side of the test signals. The f2-f1 is at basically the same amplitude as from the USB playback test. The second- and third-order sideband peaks are also at similar levels, but the noise around -70 to -80 dBV becomes an issue.

You can see there’s a mirror image of the side-band distortion added to the output centered around 30 and 50 kHz. If, indeed, there is any validity to claims about the importance of audio content above 20 kHz, this unwanted information would be detrimental. In short, the intermodulation distortion is a bit worse in terms of the effects on audibility.

Conclusions on Bluetooth Audio Quality

Based on these tests, there’s a subtle but audible difference in sound quality when streaming music over a Bluetooth connection compared with playing the same tracks directly from a USB stick. If you’ve invested in a high-quality source unit or digital signal processor but are transmitting audio wirelessly, you are doing yourself a disservice. The difference isn’t as significant as moving from consumer-grade to audiophile speakers, but where every step in the audio chain matters, Bluetooth remains a weak link.

We’ll start looking for a phone that supports the LDAC codec so we can repeat this comparison.

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 final article in our series on understanding high-end car audio systems moves away from the need for accurate system design, integration, configuration and calibration to discuss audio product quality. If you’ve been a long-time reader of the articles at BestCarAudio.com, you know that we put a significant emphasis on identifying car audio products that perform well. Importantly, those solutions aren’t always the most expensive options. Let’s discuss what higher-quality audio products sound like and how they should behave.

What Is Car Audio Product Quality?

Depending on your point of view, audio product quality can have a lot of different meanings. From the perspective of the retailer you’re working with, it might mean that a particular brand is incredibly reliable. For example, we’ve tested amplifiers from Rockford Fosgate and ARC Audio that can run at their maximum rated power for at least 20 minutes without any issues. In contrast, in the same tests, we’ve tested other amps that overheat and shut down in under three minutes. If you play your music at high volume levels or live somewhere that’s hot in the summer, picking an amplifier with a functional heatsink design will help keep your music playing without interruption. An amp with better cooling capabilities will likely last longer than one that overheats its internal components frequently.

Another consideration in audio product quality is noise. Many low-priced source units use low-quality preamp output stages and even more amplifiers that produce audible amounts of hiss while they make a lot of power. Listen to almost any motorcycle audio system with super-small amplifiers, and you’ll hear the system hissing when no music is playing. Audible noise like hiss isn’t acceptable in a high-end car audio system. During the system design stage, part of the product selection process is to audition the products you want to use. This might be on the store’s display board or a demo vehicle. It’s crucial that you listen for absolute silence between tracks. One note: Every piece of electronics adds a tiny bit of noise. If you put your ear up to a tweeter, you’re going to hear something. That’s OK. When the noise is loud enough to be heard at the regular listening position, then it’s a problem.

Speaker Quality Characteristics

When it comes to all-out audio system performance, the difference between regular consumer-grade speakers and those that sound truly magnificent comes down to frequency response and linearity. Both are relatively easy to distinguish. Once again, part of the purchasing process is to audition the speakers before you purchase them. As we’ve mentioned, you’ll want to bring along your absolute favorite music and listen to it on several speaker options. We recommend starting with a speaker that might even be slightly above your price range. This “should” set a benchmark for how accurate your music can sound. However, there’s a problem. There are several “boutique” or “luxury” brands that, while they are expensive, don’t offer genuinely high-end performance. As such, the key to getting the most bang for your buck will be to visit several retailers and audition as many speakers as possible. After a few visits, you’ll be able to pick out the designs that offer truly accurate performance.

Here are a few tips for auditioning speakers for linear frequency response. Start with the easy stuff. Listen for unwanted emphasis in the high-frequency region. The letters S, T and P might be too loud if there are issues with a midrange or improper level-matching of a tweeter. Listen to music that doesn’t have too many instruments. We hear people talk all day. So listening to voices is a great way to audition speakers. We know a few people actually listen to movie soundtracks rather than music, as the vocal recordings are sometimes less processed. We recently started using “Into My Arms” by Nick Cave & The Bad Seeds for this very purpose. “Spanish Harlem” by Rebecca Pigeon is another track that will make any frequency response issue stand out. No, neither of these is a fun audio system demonstration track. They are, however, a great way to assess the quality of the speakers.

You want to listen for dynamics at lower frequencies, as would be produced by woofers and subwoofers. This is the second characteristic of speaker quality. Listening at lower volume levels doesn’t tell you much because the speakers aren’t working very hard, and, as such, the cones aren’t moving much. Inexpensive or low-tech speakers can sound fine when loafing along at these volume levels. Where features that improve linearity come into their own is when you start to really turn up the volume. First and foremost, the music should just get louder. There shouldn’t be any change in frequency response or tonal balance. Bass frequencies, in particular, should remain tight and dynamic.

If things get sloppy or boomy, the speakers you’re listening to have linearity issues. The problem could be a simple excursion issue where the speaker has run out of voice coil length. The issue could also be more complicated. Some speakers, especially larger woofers like a 6.5-inch, change frequency response depending on the cone position. When the voice coil is in its most outward or forward position, less of the voice coil is in the magnetic gap, so there is less inductance. When the speaker moves rearward, the opposite happens. With more of the voice coil wrapped around the T-yoke, there is more inductance and, as such, less upper midrange output. These position-based issues are surprisingly common in mid-priced speakers and those expensive speakers that are just overpriced mid-quality solutions. While not a guarantee of performance, woofers and subwoofers that include copper or aluminum shorting rings or a copper T-yoke cap typically exhibit less change in performance as the cone moves inward or outward.

Amplifier Quality

Sadly, there are no specifications available from reputable manufacturers that completely describe an amplifier’s sound. Of course, frequency response is a factor, but nobody provides measured frequency response under a reactive load. Further, there is no standard for a reactive load test. As such, predicting their performance is impossible, particularly in the case of Class D amplifiers.

Second, relevant distortion measurements or specifications are also difficult to interpret. Some companies that offer great-sounding amplifiers say that their amplifiers operate at less than 0.1% THD+N. I would hope so, as that’s a pretty lousy distortion specification. Others that provide really low distortion specifications, like 0.002%, aren’t clear about how they measured that number. Was it at a particular frequency or output level? Based on our extensive experience with reviewing amplifiers, it appears that intermodulation distortion performance is more relevant to the “sound” of an amplifier than harmonic distortion. Even fewer companies even test for IMD or publish relevant data.

As an aside, the lack of accurate and detailed quantification of amplifier performance allows these boutique and luxury brands to proliferate. Consumers are often misled by the higher prices, thinking that they are buying something truly magnificent. Often, the reality is that these solutions are inexpensive products with strong marketing programs. See “Lipstick on a Pig” for reference. But we digress.

So how do you pick an amplifier that sounds good? Once again, it would be best to listen to as many as possible under controlled conditions. This means using the same speakers and volume levels. Making this happen is extremely difficult, as very few retailers match the amplifiers on their displays so they all produce the same output. We have decades of experience in auditioning amplifiers, and we can pick out the ones that sound bad, good or great, often in different systems. However, expecting anyone to devote thousands of hours over decades to establish this experience is unreasonable.

The answer remains: You have to listen. Dynamics are once again a good tell. We recently reviewed a small amplifier. It sounded pretty good at lower volume levels. The reduced energy storage (because of the small size) made the amp sound softer when pushed harder. The attack of a kick-drum was mushier. A rim shot on a snare didn’t make us wince. Now, it’s really difficult to separate the difference in amplifier performance at low versus high output levels from the same changes in performance from speakers. As such, you want to audition amplifiers with genuinely high-quality speakers, even if they are better than what you plan to use.

What Does Audiophile-Grade Car Audio Sound Like?

The point of building any audiophile-grade sound system is to extract the most accuracy possible from a recording. As the previous articles have detailed, the frequency response, sound source and imaging are crucial to presenting the music accurately. Those characteristics are primarily focused on audio system design, installation and calibration.

The difference between run-of-the-mill audio equipment and those components that sound truly exceptional is revealed as accuracy. Does a performer’s voice sound authentic or like a very good audio system? Realism is the next level. When it doesn’t sound like you’re listening to audio equipment, and it sounds like the performer or instrument is out in front of you, you are experiencing something truly exceptional. Of course, it takes a complete system to make this happen. A great source unit, a high-quality digital signal processor, excellent amplifiers and truly amazing speakers are all necessary. It all needs to be installed, configured and calibrated correctly, too!

A while back, we were rewiring the test bench in our lab. We use an ARC Audio PS8-50 to power the audio system on the bench and the nearby computer. The main computer’s TOSLINK digital output feeds audio to the amp. We also use the test bench computer’s analog output. After completing the rewiring, we tested everything to ensure that it was all working. We played the same song from each computer. There was an audible difference between the two sound sources. We fine-tuned the output levels to make sure it wasn’t a psychoacoustic trick and repeated the comparison.

The TOSLINK connection sounded better than the line output on the lab bench computer. Tonally and spatially, they sounded the same. The difference was in the clarity or transparency. There was less “other stuff” on the signal from the main computer. Think of it as hearing less static from a radio station. Better, think of it like less grain in a printed photograph. The image was identical, but it was clearer. Another example we use is the difference between driving with a spotless windshield and one that needs that annoying greasy film that builds up on the inside removed. Of course, you can see where you are going through both. However, the difference is clearly visible when you get that just-slightly-dirty window clean.

Wait, I Like My Music LOUD!

So far, this series of articles on audio quality hasn’t talked much about those who want their audio systems to play louder. Now, unfortunately, there are a lot of people who think loud doesn’t sound good. More people don’t know how good loud can sound. One of the best things about an excellent car audio system is that you are welcome to play it loud. You aren’t going to bother the rest of your family or the neighbors if you crank the volume while driving to work. You are in your own little entertainment cocoon.

A well-designed audio system should sound great at background levels and at concert levels. All the features that make a speaker great also allow them to play loudly. This wasn’t the case 20 or 30 years ago. High-end speakers of that era were fragile. They used tiny voice coils that didn’t weigh much. An audiophile-grade 6.5-inch woofer might have more output capability than some entry-level 8-inch subwoofers. If the SPL guys heard what great speakers sounded like, they’d ditch that pro-sound stuff in a heartbeat. We’ve converted a few folks over to using an audiophile-grade front stage for their systems that are capable of over 150 dB SPL. Their music stays clear and detailed, even at volume levels that blur your vision and rattle your fillings.

The Four Stages of Truly Audiophile-Grade Car Audio

Well, there you have it, a series of four articles that explain what to expect from a genuinely audiophile-grade car audio system. If you are a true music lover who cares about the quality and accuracy of what you are listening to, take a drive down to a local specialty mobile enhancement retailer and start the process of designing a genuinely high-end audio system. Do your work beforehand to choose a shop that has the skills to properly execute the system design, integration, installation and calibration. Be sure to shop around. Many shops with great reputations can’t deliver on what we’ve talked about in these articles.

Associated Articles:

The Four Stages of High-End Car Audio – Frequency Response
We explain why proper system design and calibration are crucial to recreating music with realistic tonal balance and frequency response. (https://www.bestcaraudio.com/the-four-stages-of-high-end-car-audio-frequency-response/)

The Four Stages of High-End Car Audio – Part 2: The Soundstage
At a concert, the music you hear should sound like it’s coming from the performers on the stage. This article explains what to listen for to determine the accuracy of the soundstage in your car audio system. (https://www.bestcaraudio.com/the-four-stages-of-high-end-car-audio-part-2-the-soundstage/)

The Four Stages of High-End Car Audio – Part 3: Imaging
Once you’ve established a good soundstage, an audio system with precise imaging will provide the sensation of real live performers out in front of you rather than a blurred wall of sound. (https://www.bestcaraudio.com/the-four-stages-of-high-end-car-audio-part-3-imaging/)

The Four Stages of High-End Car Audio – Part 4: Product Quality
One of the most crucial components in designing a truly audiophile-grade car audio system is using excellent equipment. We explain what to look for in terms of speakers and amplifiers and why the performance difference is crucial.

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.