How to properly set an Equalizer in a car audio system

RTA screenshot using JL Audio Tools for EQ tuning

Car audio equalizers are great, if you know what they’re for and how to use them to your advantage.

Estimated read time: 7 minutes 39 seconds.  Want to read later?

Car stereo manufacturers often brag about their equalizer.  Plastered in bold lettering on the outside of the box you will see phrases like, “3 band parametric EQ” or “7 band pro audio equalizer” “advanced 13 band EQ”.

Are you wondering what difference an EQ can make?

Kenwood Excelon DNX9990HD Equalizer Menu
The 13 bands of equalization in the Kenwood DNX9990HD can turn your listening experience into a dream if you know how to use it or a nightmare if you haven’t a clue about what it can do.

I want to equalize the misbehaving sine (wave).

A lot of people assume if a stereo has an EQ than it must sound really good.  Not necessarily.  High quality sound reproduction still requires a high quality digital to analog convertor.  If you can start out with a good quality head unit that sounds good while listening with the EQ flat, then it can only sound better after correcting for imperfections in your listening environment.  If it sounds unpleasant without any EQ adjustments, consider checking things like phase on your speakers, crossover adjustments on any aftermarket components speakers (tweeter level), crossover settings on any aftermarket amplifiers or maybe even just the quality of the audio components you’re using.

I got a lot of flack from readers for comparing the Pioneer DEH-80PRS to Kenwood’s KDC-X996 while listening at flat.  I did this for a very good reason.  An equalizer is not there to improve the inherent sound quality, detail or ability of a stereo’s DAC to reproduce lively, natural sound (For those that don’t know, DAC stands for digital to analog convertor or what I like to refer to as “what takes the data on your CD or iPod and converts it to the audio that you hear”).

I’ll say that again because I’m sure I may have surprised or confused many readers out there.  An equalizer is not able to improve or enhance a receiver’s ability to reproduce audio in a more detailed or lively manner.  When properly adjusted, it can appear to sound as though it added more life and vibrancy, but in reality, you’ve simply corrected and accounted for imperfections created by the overall acoustic environment.  Basically the closer you can start to perfection, the easier it will be to get there.  So make sure you start with a head unit that sounds pretty darn good without tweaking anything.

Get your tools ready.  No tools?  An iPhone will work too.

Now that I got that out of the way, let’s talk about how you can properly use an EQ to improve and correct the sound in your car audio system.  Before you can begin tuning the audio system in your car, you will need a tool to measure the sound in your vehicle.  How can you correct or improve the sound it if you don’t know where the imperfections lie?  Although my husband John and I both have an excellent ear for music and can generally tune by ear much of the time (interestingly, we’re also both able to pick up and play instruments by ear as well), for perfection, you really have to measure what you’re attempting to correct.  And to measure and analyze sound, we use a few different tools.

One of which is a real time analyzer, also known as an RTA.  Years ago, an RTA was this big, bulky analyzer that we had to set up in a car with a mic stand positioned in the drivers seat.  Thanks to awesome technology, these tools are now easily accessible to anyone.  These days we can accomplish the same thing using an app on our iPhone.  I like to use one of two apps on my iPhone.  Both are made by Studio Six Digital.

JL Audio Tools is a free app which includes an RTA

JL Audio Tools is a free app which includes an RTA (Real Time Analyzer), SPL meter and speaker polarity testing (phase).  The more advanced Audio Tools app provides additional features such as signal generators, audio scope, delay finder and many more acoustical analysis tools.  Either app can be downloaded from iTunes.  Besides the app, you will need some pink noise.  I find the Audio Tools app to be more convenient because it comes with a built in pink noise generator.

Pink noise is equal output of a large range of frequencies, typically from around 20 hertz (slightly below human hearing) to 20,000 hertz (slightly above human hearing) and everything in between.  The equalizer on a car stereo represents a division of bands of these frequencies.  For example, a 3 band EQ may be referred to as representing Bass, Mid and Treble.  Bass may represent frequencies of 60 – 200 hertz, Mid may represent 400-2,500 hertz and treble may represent 8,000 – 15,000 hertz.  The more bands, the finer the division of frequency groups, meaning the greater control you have over correcting and tweaking imperfections.

Analyze this.

So let’s do a little analyzing.  Here is a screen shot of a real time analyzation of pink noise played through my iPhone.

RTA screenshot using JL Audio Tools for EQ tuning
RTA screenshot using JL Audio Tools for EQ tuning

Here is an ideal curve drawn by my lovely husband John who also used to be a judge for IASCA (International Auto Sound Competition Association).  Notice his rules, No more than 3 DB change in adjacent frequencies.  I’ll address that shortly.

Plotted ideal RTA Curve
Plotted ideal RTA Curve

So if I were to try and overlap a proper curve over our RTA analysis, it would look something like this:

Ideal curve overlapped over RTA
Ideal curve overlapped over RTA

Excuse the poor drawing.  I’m using Paint here, not the easiest thing to draw with.  Notice the dB increments on the RTA are in increments of 10 vs on John’s drawing he had increments of 3  .John pointed out that you don’t want more than a 3 dB difference between frequencies.  The larger the gap, the more displeasing the sound.  Listener’s fatigue occurs when there are large gaps between frequencies.  Your brain is actually trying to correct for any gaps or overages it’s hearing and it gets tired and irritated doing so.  To correct these gaps and overages, we can use our equalizer.

Okay, so how do we fix this?

So in this example, it’s safe to say we need to bring the bass down or almost equal to the mid range band.  If we have a 3 band EQ, that will adjust a range of frequencies equally (remember we said roughly 60-200 hertz?).  That won’t help with the large gap between 63 and 50 hertz or the even larger gap between 40 and 50 hertz.  So how do you correct this?  You need a larger range of individual frequency bands to adjust.  If you had a 31 band EQ, that would be no problem.  You could go to the exact frequency that is unbalanced and correct it.  A 13 band gives you a nice range of control as well.  A 3 band EQ is extremely limited.

If there are any external factors that can be adjusted to correct the problem, try tweaking those first.  Examples would be adjustments you could make on your aftermarket amplifier like gain, crossover or bass boost.  Other possible tweaking areas would be subwoofer placement or installing a sound deadening material like Dynamat.  After you’ve addressed any controllable external factors, see if the large gap still exists.  If it does, the only thing you can really do is this.  Adjust the center frequency of your bass, mid or treble that needs balancing, then make your bandwidth narrow, then make your level adjustment (Huh?).

If I lost you there, check out this example:

Suppose we were able to bring  the gap between 32 and 63 hertz to a reasonable level through adjusting gain and/or bass boost settings on our subwoofer amplifier.  Now we can lower our bass level and thus reduce the level of frequencies ranging from 32 to 200 hertz to about where they should be, slightly sloping down towards 200k.  Remember these level adjustments are done equally among the range of frequencies in that band.

Next we can adjust our mid range frequencies on our basic 3 band EQ.  Notice that 250k is at a much higher level than the other mid range frequencies in that mid range band.  How do we narrow in on the small gap that exists in such a wide band?  In the mid adjustment menu on our basic head unit there should be the option (hopefully, if you didn’t cheap out too much) to select the center frequency.  This is the frequency your adjustment range is centered on.

Our choices for center mid frequency usually range from 400 – 2500 on head units that have this option.  We can then select 400 hertz as that is the option closest to the frequency that needs adjusting.  Next we can select a narrower bandwidth.  This adjustment narrows the band of frequencies we’re adjusting when we actually boost or lower the mid level.  That means rather than boosting or lowering a wide range of mid frequencies equally (like a range of 400 – 2500 hertz) we’re centering our adjustment closer to the imperfection located at 250 hertz.  It’s far from perfect as it will also adjust 400 hz, but if we lower that narrowed mid adjustment slightly, we will be able to bring 250 hertz down to a slightly closer level of the other mid range frequencies.

Once we’ve brought that mid range frequency a little more into balance with the other mid range frequencies, we would want to lower the treble slightly to try to get as close as possible to the ideal curve.

That’s how you can tune with a very basic EQ and you can see how limited your control is for true correction.  When you actually have 13 or more bands to work with, you have much better control over correcting imperfections in the given acoustical environment.  EQ’s can allow you to remove large peaks and valleys between frequencies which can create harsh and unpleasant sound reproduction.  When used properly, they can correct and smooth out the overall tonal qualities of your car audio system.  When used improperly, they can make your hi fidelity components sound harsh, hollow, tinny or too bright.  So use your RTA and pink noise and set your EQ properly.  You will be rewarded with the sweet sound of perfection.

How to tune a subwoofer amplifier

JL Audio crossover, gain and bass boost dials

What do all these dials and switches on my amp do?

This article discusses the various adjustments made when installing a car audio subwoofer amplifier. Addressing cross over adjustments, gain adjustments and Bass EQ

Estimated read time: 3 minutes 45 seconds.  Want to read later?

Hello everyone!  I’ve been meaning to write this for a long time, so sorry for the delay between posts.   At Sounds Incredible Mobile, I get plenty of customers who like to install their equipment themselves.  I’m all for that, unless they don’t know what they’re doing and they blow something up because of improper installation.  So, if you’ve got a nice amp and sub you want to install, but you’re afraid you don’t know what you’re doing as far as tuning goes, this article is for you.

So what are all these adjustments and dials on the side of the amp?  What do they do?

Side view JL Audio JX 500/1
Side view JL Audio JX 500/1


Low Pass Filter. This is the 1st thing you’re going to want to adjust. If you’ve got a car with decent sized speakers, like 6.5″ or 6×9, you’ll want to set this to about 80 hertz (lo-pass). If your head unit has built in crossovers, you want to set those at 80 hertz (hi-pass) as well. This way your interior speakers are playing 80 hertz and up, the frequencies they’re most capable of playing and your subs will be playing 80 hertz and down. This way everything is playing as efficiently as possible and each component is playing the frequencies they’re designed to play. If your speakers are smaller than that, you may want to set the cross over on the amp and head unit around 90-100 hertz to make up for what the smaller speakers can’t really reproduce. Once that is set, we can move on to gain.

Gain is not a volume knob, that’s a very important thing to remember when it comes to tuning. In fact, it’s so important, it bears repeating: gain is not a volume knob. It’s a sensitivity level adjustment.  It’s about matching the sensitivity of your deck’s subwoofer preout to the amplifier.  Let’s say you have a basic head unit with a 1.8 Volt preout.  The amplifier is not going to be as sensitive to a 1.8 Volt preout as one with a 4 Volt preout.  So you want to match the sensitivity.  Minimum on an amp gain is usually 5 Volts, Maximum is usually around .2 Volts.  Even your cheapest aftermarket head unit is usually at least around 1.2 Volts, so even then your gain should never be maxed out.

If you’re going speaker level in, you’d probably be surprised to learn you’re probably around 5 Volts, so even with a stock head unit, you shouldn’t have to crank the gains.  If it sounds like you need to, please read an earlier post about adding an amp and sub to a stock system.  If you get the wrong speakers for the source of the signal or if you have a stock amplified system, you may need to tweak a few things to get the sensitivity right.

A good rule of thumb is to never put the gain up more than 3/4, but if your deck is on the higher voltage side, less should be sufficient.  Remember, distortion is what kills subs and speakers. It’s a lot harder to hear distortion on bass than it is on interior speakers. And certain songs may distort at certain volumes while others do not, so it’s something you really have to pay attention to in order to avoid damaging your equipment. So crank the volume, put on a variety of music, and slowly bring up the gains to a point where it sounds good, but you don’t hear the subs flubbering or distorting.

Bass EQ.  What exactly is Bass EQ?  Frequencies have wavelength, a frequency of 45 hertz has a wavelength of about 25 feet.  This means in order to hear the full cycle of a 45 hertz wave, that wave has to travel a full 25 feet.  The distance from your subwoofer box and your ears is probably less than half that distance (This is why I love time correction/time alignment!).   The other issue you run into in a car environment is incidental sound waves.  That 45 hertz sound wave is not only trying to travel to the front of the cabin, but part of it is going to hit the other walls of your trunk and bounce back towards the front.  Some of these sound waves will put that 45 hertz frequency out of phase due to the timing of the sound waves.

By boosting that frequency, we help to make up for any phasing issues that may occur due to cabin design.  It helps to play around with the placement of the sub before actually turning this adjustment up.  Sometimes you have to use Bass EQ just to correct phasing issues that occur due to road noise.  This is definitely true if you find your system sounds good when you’re not moving, but your bass disappears as your drive.

Bass boost adjustments are usually tuned around 45-50 hertz on amplifiers, so they are boosting the playback of that particular frequency.  Bass Boost or Bass EQ adjustments should be done last after all other adjustments have been done and subwoofer positions have been tested as it’s really an attempt to correct for poor cabin acoustics.

The car is a tough environment for acoustical bliss, but it can be achieved with some technical understanding and some time and patience.