We aren’t sure where or when things went wrong with the basshead crowd, but there’s a serious misunderstanding about how to build a loud stereo system. We’ve lost track of how many of these vehicles we’ve heard that sound utterly atrocious. No, we aren’t talking about the fact there’s 30 or 40 dB too much bass. That’s fine, given the goals. The issue is how horrific the midbass and midrange frequencies sound. The same mistakes seem to repeat in every system. Let’s look at what it takes to make a loud car stereo system that actually sounds good.

Loud Bass Is Easy

Let’s start by addressing bass frequencies in loud car stereo systems. This part of the system design is easy, as many companies offer subwoofers designed with impressive power handling and excursion capabilities. If you want to be loud, your subwoofers must move a lot of air. This means the cones in the woofers need to move back and forth a significant amount. Good quality subwoofers with excursion capabilities of 2 to 3 inches of linear excursion are readily available. Likewise, amplifiers capable of producing more than 2,500 watts of power can push these drivers effortlessly. Combine this with a well-designed, sturdy enclosure and making massive amounts of bass is a snap.

Making Midrange and High Frequencies Sound Good

Here’s where things go sideways when designing a loud car stereo system. Hundreds, if not thousands, of car stereo systems are built with high-efficiency speakers in the doors. We don’t and never will understand this speaker selection choice. High-efficiency speakers get their efficiency by reducing the mass of the cone assembly. This low-mass cone design raises the speaker’s resonant frequency and allows it to play louder with the same power as a driver with a heavier assembly. This reduction in cone assembly mass also dramatically reduces the midbass these speakers produce. It’s common for a high-efficiency midrange speaker to be efficient only from 200 hertz and up.

The graph above shows a high-efficiency speaker’s second and third harmonic distortion (in red and blue, respectively) when driven with just under 4 watts of power. The output at 200 hertz includes 1.5% harmonic distortion. That’s pretty bad at a power level this low. You can also see that the driver’s output starts to roll off around 175 hertz.

As this graph above clearly demonstrates, distortion increases with excursion. If you look at the amplitude of the red and blue traces, they get higher as frequency decreases. This increase in distortion directly correlates to cone excursion requirements to produce audio at lower frequencies. Using high-efficiency speakers below about 300 hertz, even with modest power, is a recipe for a stereo system that will sound terrible.

Further, there’s really no need for the added efficiency. Amplifier power is inexpensive these days. You can purchase a four-channel amplifier that produces a good, clean 75 watts of power per channel for under $300. This is enough power to push all but the most robust midrange speakers to their limits.

Excursion Matters When Reproducing Midbass

Let’s examine the excursion requirements of a 6.5-inch speaker asked to produce midbass information. A three-way system with subwoofers and tweeters requires a speaker like this. In most cases, we’d use a crossover point around 80 hertz, so pay close attention to that frequency in the graphs below.

The red trace in the speaker efficiency comparison graph below is a typical high-efficiency speaker with a sensitivity rating of 92.4 dB at 1W/1M. It has a resonant frequency of 101 hertz and a linear cone excursion rating (Xmax) of 2.6 mm in each direction. The yellow trace represents this woofer. The second woofer is from the Rockford Fosgate T4652-S component set. This driver has a resonant frequency of 49 hertz and a mind-boggling 12.6-millimeter excursion specification. That’s more excursion than some entry-level 10-inch subwoofers. The red trace in the graphs below represents the Rockford Fosgate woofer.

The chart above predicts the output of each woofer when driven with 100 watts of power. Let’s start with the obvious. Up at 500 hertz, the high-efficiency speaker theoretically produces 113.2 dB SPL of output. The Rockford Fosgate woofer is producing 107.4 dB SPL with the same power. So far, you’d think the high-efficiency speaker is the way to go, right? Well, what happens at lower frequencies? We can’t use this graph to answer that, as we need to consider cone excursion limitations. The chart below shows cone excursion versus frequency for the two woofers.

As you can see, the yellow trace turns translucent at frequencies below 440 hertz. This means that at all frequencies below 440 hertz, the driver will exceed its 2.6 mm Xmax specification when driven with 100 watts of power. If you want your car stereo system to sound terrible, pushing a driver beyond its excursion limits is a perfect way to do it. It’s essentially mechanical clipping, adding vast amounts of nasty distortion to the speaker’s output. Ew! By comparison, the Rockford Fosgate woofer has no problem producing audio information well below the 80-hertz crossover point. Let’s look at another factor, maximum acoustic power.

This graph shows the maximum output capabilities of the two woofers based on their excursion capabilities. The yellow high-efficiency woofer can only handle its full-rated 100 watts of power at frequencies above 500 hertz. The Rockford Fosgate woofer, on the other hand, is good down to 66 hertz. Wow, it’s almost like it was designed for a high-output three-way car audio system! Ensure that you add a healthy dose of sarcasm when reading that last sentence.

Less Power Means Less Excursion

We’ve noted that excursion is directly proportional to frequency so far, and this has been the limiting factor in how much midbass information this high-efficiency speaker can produce. Excursion is also proportional to the power sent to the speaker. If we drive the high-efficiency speaker with 50 watts of power, it can play down to 360 hertz without exceeding its Xmax rating. That’s a bit better. So, how much power can it handle if we want it to match the roughly 66 hertz capabilities of the Rockford Fosgate woofer?

That’s right, if you feed the high-efficiency woofer anything less than 0.65 watt, you can use it as a midbass driver. It will produce 85 dB SPL of output at 100 hertz at this level, so it’s not a total waste. Sorry, that was also sarcasm.

Options for Producing Great Midbass in a Loud Car Stereo System

So, what are the options if high-efficiency drivers aren’t the solution for midbass? Your car audio system needs a good woofer, not a high-efficiency midrange driver. We aren’t talking about subwoofers here. We’re referring to drivers designed to play from 60 or 70 hertz up to at least 400 or 500 hertz with good excursion capabilities. Most work up to at least 2 kHz or higher with minimal issues. These are a bit harder to find, but they do exist. The woofer from the Rockford Fosgate T4652-S set is a good example. So is the woofer from the T3652-S set, as it’s pretty similar in design and capability. You will want to look for a 6.5-inch driver with an Xmax specification of at least 8 millimeters. That is, if you want to drive the woofers with their full-rated power handling down to a crossover point of 80-ish hertz. Above 450 to 500 hertz, you can use those high-efficiency drivers as midrange speakers.

A high-performance audio system design aims to choose speakers optimized to operate within a specific frequency range without exceeding any of their specifications. You wouldn’t use a tweeter as a midrange driver. You wouldn’t use a midrange driver as a subwoofer. So why try to use high-efficiency midrange drivers to reproduce midbass frequencies? They sound terrible at all but a loud conversation level. Drop by a local specialty mobile enhancement retailer today to find out what speakers are available to make your loud car stereo system sound good.

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 power ratings are among the most confusing and misleading specifications in the car audio industry. Once you understand the process used to test speaker power handling, you’ll quickly realize that the information doesn’t always translate to information that’s helpful in choosing an amplifier. Let’s dive into the science behind choosing the best amplifier for your car audio speakers.

Speaker Power Ratings

In short, how much power a speaker can handle depends primarily on the voice coil’s diameter, length and number of windings. Secondary considerations include the gap size between the voice coil assembly, the T-yoke and the top plate of the speaker. Closer proximity helps to improve heat transfer away from the voice coil. A smaller gap also increases efficiency. However, if the gap is too tight, the voice coil or former might rub, which can cause damage and distortion. Cooling technologies like a vented pole piece, vents under the spider mounting plateau and vents in the former also help by allowing air to flow around the voice coil.

The type of enclosure used also plays a role in power handling. A sealed enclosure will trap heat around the motor assembly. A vented enclosure will allow heat to escape as air is exchanged through the vent resonance.

Audio Content and Power Handling

A concept that many audio enthusiasts don’t fully understand is how power is distributed based on audio frequencies. Looking at frequency response measurements on a real-time audio analyzer can exacerbate this misunderstanding.

When we look at acoustic audio measurements of pink noise on an RTA, we expect to see a flat line. This indicates that the amplitude of each frequency is equal. While we might want to bump up the bass to make the system fun or attenuate the high-frequency content by a few decibels, we don’t want peaks or dips anywhere in the graph.

Where the confusion lies is that the technician working on calibrating your car audio system is using pink noise with the RTA. Pink noise contains random frequencies with the same energy per octave. Put another way, dividing power by the range of frequencies in a given octave will give you the same energy per hertz.

Between 10 and 100 hertz, there are 90 1-hertz frequency bands. We have 900 bands between 100 and 1,000, and 9,000 between 1,000 and 10,000. Let’s say we have 10 watts of power to distribute among those frequencies. In our lowest octave, each one of the hertz bands gets an average of 111.11 milliwatts. In the band between 100 and 1000 hertz, each hertz band receives an average of 11.11 milliwatts. In the top octave between 1,000 and 10,000, each hertz band receives an average of 1.11 milliwatts. Once again, this power distribution produces a flat line on an RTA graph.

The bottom line is that pink noise matches how humans perceive sound. Our ears perceive pink as having the same volume level at all frequencies. Pink noise is occasionally called an equal intensity curve.

What Does Frequency Have To Do with Speaker Power Ratings?

Imagine, if you will, a typical mid-level car audio subwoofer. It might have a 2-inch diameter voice coil former with a winding that’s 1.5 inches tall with a two-layer winding. Rated power handling might be around 400 watts. Now, let’s consider the voice coil in a typical 6×9 speaker. The diameter might be 1 inch, and the winding might be 0.75 inch tall. The speaker might have a continuous power rating of 100 watts. All of this makes sense so far. Less mass in the winding means it can handle less heat.

Now, let’s think about a tweeter. It likely has a voice coil diameter of 1 inch, but the winding might be 0.2 inch tall, and it will surely have no more than one layer. Worse, the wire will be tiny in diameter. Even then, many stand-alone tweeters have a power rating of 100 watts. How can this small voice coil dissipate 100 watts of heat? What about P.A.-style speakers? They often have extremely short voice coils. Yet some claim to have 200-, 300- and even 500-watt power handling ratings. How is this possible?

If the power handling test uses filtered pink noise, then the speaker is tested with less power. A tweeter can’t reproduce bass or midrange frequencies. So, to test their power handling, the noise waveform would be filtered at something like 3,000 or 4,000 hertz. Filtering the bass information removes significant energy from the signal.

If we apply a 2-kHz high-pass filter to a 100-watt equivalent pink noise signal, the result would be only 1 watt of power going to the speaker. Midrange and high-frequency speaker power ratings are almost always quantified this way. So, your 100-watt tweeter can only handle 1 watt of power. Your P.A.-style midrange likely can’t play much below 300 Hz. It might only get 3 or 4 watts of power if appropriately filtered from our 100-watt example.

Matching Amplifiers to Speakers

Now that we’ve set the stage for understanding power ratings, we can finally talk about matching amplifiers to speakers. How powerful of an amplifier do you need for your speakers? The answer starts with the frequency range in which you’ll operate the speakers. With subwoofers, you’ll be playing bass frequencies, so almost all the energy in the music will arrive at the speaker. You’re in the same boat if you have a system with 6.5-inch or 6×9-inch speakers and no subwoofer. You’ll be sending bass information to the speakers. If your system has a subwoofer, you’ll likely only send frequencies at 80 hertz and above to the speakers. That’s about 1/10 of the maximum power compared with a full-range signal. In theory, you only need 1/10 the power to your mids as your subwoofers need. So, 500 watts to a sub and 50 watts to the mids. If you have actively filtered tweeters, they likely only need a few watts.

A lot of this is theoretical rather than practical. So, let’s look at midrange speaker power handling another way. Let’s say you have a set of mid-quality component 6.5-inch speakers. They have a 100-watt power rating, and the woofer might have an Xmax specification of 4 mm. Let’s examine how much the woofer cone moves with 100 watts of power.

The graph above shows us that the driver reaches its 4 mm excursion limit at 110 hertz. If you play music with content lower than 110 hertz, the driver might bottom out or, at the very least, sound terrible. If you want your audio system to sound terrible, driving midrange speakers beyond their excursion capabilities is a great way to do it. With an 80 hertz crossover point, 100 watts is too much power. As it turns out, 50 watts at 80 hertz results in a cone excursion of 4 mm.

What About Time?

If you look at speaker specifications, you’ll see both continuous and peak power ratings. Some companies incorrectly refer to the continuous rating as an RMS rating. Using the term RMS implies that the power measurement was done with an RMS current or voltage measurement, not the waveform’s peak values. RMS refers to the amplitude in an AC waveform that can do the same work as an equivalent DC voltage.

Companies with genuine engineering specifications for their speakers will test them at their continuously rated power level for eight to sometimes over 100 hours. The speaker needs to continue to function after the test, and the Thiele/Small parameters should typically remain within 10% of where they were when the trial started. In other words, the voice coil can’t overheat or fail, and the suspension can’t stretch significantly.

With all that said, speakers can handle momentary bursts of additional power beyond their ratings. The problem is that how long these bursts can last without causing damage is difficult to quantify. Let’s say you’re listening to a song with a vocalist and someone playing a guitar. In the middle, there’s a drum break like Phil Collins’ solo from “In the Air Tonight.” If you cranked up the volume during that solo, even at twice a speaker’s continuous rated power level, that’s not enough energy to overheat the voice coil. So as long as the speaker isn’t physically damaged, everything should be fine.

Picking the Best Amplifier for Your Car Audio Speakers

So, after all this science and confusion, how do you pick the best amplifier for your car audio speakers? You choose the amp that sounds the best. Whether an amp makes 45, 50 or 60 watts doesn’t matter, as that’s only a difference of 0.5 or 0.8 dB in maximum output. Is a 100-watt amplifier “better” than a 50-watt amplifier? It is if it adds less noise and distortion to the signal that passes through it.

Think about how reputable companies group the amplifier series they offer. ARC Audio has the ARC Series. Rockford Fosgate has the Power Series. Kicker has the IQ Series. Audison has the Thesis Series. Hertz has Mille. Sony has the Mobile ES line. Aside from some additional features, these higher-end amplifiers sound better than the lower models. They have better signal-to-noise ratio specifications and lower total harmonic distortion numbers. When playing the same music through the same speakers at the same volume, the sound produced by higher-quality amplifiers is more precise and accurate.

How Much Power Do My Speakers Need?

We can’t count the number of times we’ve seen posts on social media asking, “What amp is best for my speakers?” The poster will then list the speaker’s continuous power-handling capabilities, even if the number is irrelevant. You already know your tweeters will never need more than a few watts, so why would you use a 100-watt amp to drive them? Well, if the amp you have in mind has excellent distortion and noise measurements at those low levels, your tweeters will sound better.

What about everyday systems? How much power does a set of coaxial speakers need? If they are an entry-level speaker, 45 to 65 watts is likely more than enough power to drive them to their limits at lower frequencies. If you have a set of mid-priced component speakers, say in the $200 to $400 range, 75 to 100 watts is adequate. If you’ve purchased high-end speakers like the ARC Audio RS, Audison Thesis, Rockford T3 or T4, Hertz Mille, Kicker QS or Sony Mobile ES, an amplifier that produces 100 to 150 watts is a good power range.

Now, is buying an expensive, high-power amplifier a waste of money when using inexpensive speakers? Maybe. Speakers are almost always the weakest link in any audio system when it comes to how much distortion they add to the audio signal. Look at our articles on Understanding Speaker Quality, and you’ll see what we mean. You are better off buying speakers with distortion-reducing technologies like shorting rings, copper T-yoke caps or even more excursion capability and pairing them with a less exotic amplifier. The net result will be much better sound. If you have a great-sounding amplifier already, use it. Just ensure that the technician configuring and calibrating the system confirms that you can crank the volume without worrying about damaging anything. This doesn’t mean setting gains with a scope or distortion tester.

If you need help picking the best amplifier or speakers to upgrade your car audio system, drop by a local specialty mobile enhancement retailer. Please bring your favorite music and listen to it on their display at the same volume levels you would in your car or truck. This demonstration will give the product specialist an idea of the performance level you need regarding speakers and how powerful the amplifiers should be. Don’t hold back. If you like it loud, crank it. Hoping inadequate products will play louder only leads to disappointment, frustration and damaged equipment.

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.