Tone Controls

I have personally driven more than 700 vehicles in the past 10 years. Because all but about 5% of them were driven during an extensive Listening Evaluation, I have a perspective that may be of interest regarding the use of tone controls.

Tone controls (Bass and Treble) seem to remain a mystery to most people. You know what I mean. What tone control settings do you find on cars that you drive but don’t own? Pick up a rental Mustang and what do you find?  Bass & Treble at Maximum Boost is a common situation.  Sometimes you find all controls set to Detent (Bass, Treble, Midrange, Fade and Balance at 0 or midpoint). Are these controls purposely factory set to provide a suboptimal amount of bass and treble? Or are they just “there” with no useful function? In my opinion tone controls are often used in a “more of anything” is better mode or just ignored because most people don’t understand how they may be useful.

Let’s start from the beginning. Most cars have simple Bass and Treble controls that either increase or decrease the amount of low frequencies or high frequencies that come out of your speakers. Some cars have Midrange control, but the use of multiband equalizers has all but disappeared. Many people fail to realize that the Fade and Balance may also be useful. The Fade control adjusts the amount of sound that comes to the front and rear speakers while the Balance control adjusts the relative loudness of the Left and Right channel speakers. In my experience, all of these controls can help optimize the sound quality inside your car. For the most part detent is a useful starting position, even if the salesman thinks otherwise. 

Of the 700 factory cars system I’ve tested, roughly half of them do sound better with all operating controls set to Detent (no kidding). In the other cases -1 or -2 Bass and -1 Treble are the most common settings which offer the best sound. Or, in the case of my 2001 Corvette, 11 am for both of the rotary Bass and Treble controls makes things sound best. On the other hand, my 2005 Buick Rendezvous requires settings of -5 Bass, -2 Midrange and -2 Treble to sound most natural. But exactly what is “natural?" You need a reference. I have a set of 63 Tracks taken from commercially available CD recordings that cover the full range of material found in the market that are speed bumps for car audio systems. But the most important reference material for tone control settings is what I call "Natural Music" which covers male and female vocals and orchestral recordings with acoustic instruments. My playback reference for car audio systems is a high-quality stereo or multichannel home audio system, setting the car system to match the home audio system as closely as possible. The reason that we don’t use live acoustical music as the reference is because few people have access to live classical voice and acoustical instruments on a regular basis.

The most common tonal balance errors found in car systems is in “Uneven Bass” and “Excess Sibilance” on female voices.  Uneven Bass is where a ab upright bass has adjacent notes that are either too loud or practically inaudible depending on what note is being played or where a voice has too much upper bass and the singer sounds like he or she has a mild head cold.  Listening to Joe Williams “Dimples” (Delos), a softly recorded track that may require full gain to attain satisfactory loudness on some system, Joe’s baritone shouldn’t have too much baritone and the bass instrument should be even and matched to the loudness of high frequencies. Typically cutting Bass by -1 or -2 (10 to 11:00 am with rotary controls) will often help balance the sound. With regard to sibilance and the Treble control; Susan Vega’s voice on “Tom’s Diner” (Solitude Standing) should not exhibit a ripping, scratching sound when she pronounces the letter “s”.  A -1 cut in treble may fix or partially fix this condition. However cutting Treble by -2 or greater sometimes causes other high frequency sounds to become dull.

Some will argue that “I never listen to acoustical instruments or female vocals.” You will find over time that when you balance your system to sound most natural with these recordings, everything else will also sound as good as it can, Also note that I can’t remember the last time where a boost of any tone control made for better sound.