When considering the tuning of an audio system, we have to consider not only the capacity of the gear and the environment (room), but also the levels which we listen. Many of us will adjust the sound of our systems at levels which are not close to those at which we really enjoying listening. This is fine, if like me, you are going for a pure, 100% scientifically tuned target frequency response. But, if you are tuning the system to your tastes, the levels at which you perform the tuning are critical to the enjoyment you’ll get from the system.
Let’s use car audio as an example.
If you tune a car’s subwoofer to sound absolutely amazing while the car is idling in your driveway, chances are very good it will be far too loud when you hit the road and need to turn up the stereo to overcome the huge increase in the sound of the road. Why? Many assume that the rumble of the road will be louder and mask the sound of the subwoofer and thus having it boosted a little is a good way to ensure you can hear it. But the real issue isn’t the rumble masking the subwoofer, it is the road noise masking everything which requires you turn up the entire volume, which suddenly brings the law of the “Fletcher-Munson Loudness Curve”, or the equal loudness curve, into play.
If you set the subwoofer level to be adequate and clear at, say, an average level of 80dB SPL, which is what many enjoy for casual listening, then when you boost the overall level to an average of 90dB SPL, the audibility of the low bass will increase at a higher rate than the midrange, thus making it appear to be getting louder at a faster rate than the midrange as you turn up the volume. Take a look at the curve below…
The bass at 60Hz needs to be set to about 90dB SPL in order to be perceivably balanced with the midrange at 1kHz at 80dB SPL. So, let’s say you tune your system so the subwoofer is about 6dB SPL louder to make it clearly audible with the midrange at moderate listening levels. Then, let’s say you turn the level up by 10dB SPL to make up for the road noise. The midrange will sound 10dB SPL louder, but the same perceived level in the bass needs only be 7dB SPL louder (at 60Hz), and thus it will now appear to be 3dB SPL louder compared to the midrange. This effect is even more pronounced if you were to tune the system at 75dB SPL avg and boost the level to 90dB SPL avg.
What do you do?
There are no easy answers. I take the approach that if I tune the speakers to be measured as flat at all levels, then I hear what I would hear if I were listening to the performance at whatever level in real life. If I was at a concert and the music was quieter, the bass would be less audible. If I was at a concert and the music levels were higher, the bass would be more audible. That is real life, so at home and in my car I experience the same thing. It is a little disappointing that I cannot enjoy hearing the deep bass if I have the volume turned down, but that’s how the cookie crumbles.
Another approach would be to tune the frequency balance so it sounds best at the highest levels you could see yourself listening on a somewhat regular basis. That way the sound is great when you are in the mood for it and can turn it up, but then it will sound a little dull with missing bass (and treble) at lower levels, but probably not as much as my “measured linear-flat” tuning.
Yet another method could be to tune it to sound best at the levels you tend to always listen (if your radio has a numbered volume indicator you probably have a good idea what level you tend to land on most of the time). If you tune it for perfect balance to your ears at that most common level, then it will sound pretty good most of the time, but it will be boomy and shrill at higher levels and lacking bass and treble at lower levels, but not as much as the prior two methods.
You could also tune the system to sound balanced to your ears at lower volume levels and just deal with the boomy and shrill sound at all higher levels, but I don't recommend it.
Finally, and this is my favorite, is to go find a receiver which has a real proper loudness control. Then you can tune the system at the higher level and as you turn it down the bass and treble will not turn down as fast as the midrange and the overall balance will appear to remain intact. I don’t know who makes electronics with a proper variable loudness control, but Yamaha used to have them in their analog stereo preamps back in the 1980s. I had one, and it worked flawlessly.
Ultimately, this is the problem with our systems. I often wonder of I think everyone has a boomy and shrill system because I generally listen at much higher volume levels than the average joe.
Let’s use car audio as an example.
If you tune a car’s subwoofer to sound absolutely amazing while the car is idling in your driveway, chances are very good it will be far too loud when you hit the road and need to turn up the stereo to overcome the huge increase in the sound of the road. Why? Many assume that the rumble of the road will be louder and mask the sound of the subwoofer and thus having it boosted a little is a good way to ensure you can hear it. But the real issue isn’t the rumble masking the subwoofer, it is the road noise masking everything which requires you turn up the entire volume, which suddenly brings the law of the “Fletcher-Munson Loudness Curve”, or the equal loudness curve, into play.
If you set the subwoofer level to be adequate and clear at, say, an average level of 80dB SPL, which is what many enjoy for casual listening, then when you boost the overall level to an average of 90dB SPL, the audibility of the low bass will increase at a higher rate than the midrange, thus making it appear to be getting louder at a faster rate than the midrange as you turn up the volume. Take a look at the curve below…
The bass at 60Hz needs to be set to about 90dB SPL in order to be perceivably balanced with the midrange at 1kHz at 80dB SPL. So, let’s say you tune your system so the subwoofer is about 6dB SPL louder to make it clearly audible with the midrange at moderate listening levels. Then, let’s say you turn the level up by 10dB SPL to make up for the road noise. The midrange will sound 10dB SPL louder, but the same perceived level in the bass needs only be 7dB SPL louder (at 60Hz), and thus it will now appear to be 3dB SPL louder compared to the midrange. This effect is even more pronounced if you were to tune the system at 75dB SPL avg and boost the level to 90dB SPL avg.
What do you do?
There are no easy answers. I take the approach that if I tune the speakers to be measured as flat at all levels, then I hear what I would hear if I were listening to the performance at whatever level in real life. If I was at a concert and the music was quieter, the bass would be less audible. If I was at a concert and the music levels were higher, the bass would be more audible. That is real life, so at home and in my car I experience the same thing. It is a little disappointing that I cannot enjoy hearing the deep bass if I have the volume turned down, but that’s how the cookie crumbles.
Another approach would be to tune the frequency balance so it sounds best at the highest levels you could see yourself listening on a somewhat regular basis. That way the sound is great when you are in the mood for it and can turn it up, but then it will sound a little dull with missing bass (and treble) at lower levels, but probably not as much as my “measured linear-flat” tuning.
Yet another method could be to tune it to sound best at the levels you tend to always listen (if your radio has a numbered volume indicator you probably have a good idea what level you tend to land on most of the time). If you tune it for perfect balance to your ears at that most common level, then it will sound pretty good most of the time, but it will be boomy and shrill at higher levels and lacking bass and treble at lower levels, but not as much as the prior two methods.
You could also tune the system to sound balanced to your ears at lower volume levels and just deal with the boomy and shrill sound at all higher levels, but I don't recommend it.
Finally, and this is my favorite, is to go find a receiver which has a real proper loudness control. Then you can tune the system at the higher level and as you turn it down the bass and treble will not turn down as fast as the midrange and the overall balance will appear to remain intact. I don’t know who makes electronics with a proper variable loudness control, but Yamaha used to have them in their analog stereo preamps back in the 1980s. I had one, and it worked flawlessly.
Ultimately, this is the problem with our systems. I often wonder of I think everyone has a boomy and shrill system because I generally listen at much higher volume levels than the average joe.
