Have you ever wondered what all of those extra features on your head unit do? You know them, they are the features that everyone tells you to turn off, the “gimmicks”, the evil bass boost, and the sound effects. These are the features that everyone says will degrade the sound quality of your system; they cause clipping, and ruin your chances of having a respectable system. Turn them all off!
But, what do these features actually do, and should you be afraid of using them?
LOUDNESS
We’re going to take a look at a particularly interesting feature, the Loudness setting. If you aren’t aware of what Loudness is supposed to do, it is designed to boost (oh no!) the low and high frequencies of your stereo at low volume levels. The amount of boost is designed to taper off as you increase the volume.
What’s the point of the Loudness feature?
It’s actually a pretty clever thing. In order to understand the usefulness of the Loudness feature, you need to be at least somewhat familiar with the Fletcher Munson, or Equal-loudness curve (or contour). The wiki link is below, but basically what Fletcher Munson discovered was that our perception of frequency response changes depending on the amplitude of sound. At low amplitude (aka volume, aka SPL) we don’t perceive low or high frequencies as being as loud as they actually are. At high amplitudes, the lows and highs begin to sound as loud as they really are in relation to the midrange. To illustrate this, listen to a fairly dynamic song at a level you would consider enthusiastic. Nothing so loud that it’s uncomfortable, but the kind of level that you would listen at when you are really into the music. Make note of the frequency response, particularly how the lows, mids, and highs all balance out. Now, turn the music down to roughly conversation level, and you’ll notice that the perception of balance falls apart. The bass is gone, the highs are gone, and you just get mostly midrange. When you turn the volume down, the dynamics are gone, and the perceived frequency response changes. Instead of lowering all frequencies equally, the perception is that the lows and highs fall off much faster than the midrange as you turn the volume down. That is what the Flutcher Munson curves explain, and it’s the reason the Loudness feature exists.
Equal-loudness contour - Wikipedia
Now, let’s take a look at what the Loudness feature does from an objective standpoint, and help people understand if it’s useful, or if it really is the devil people claim. Most head units have a feature like this, on my Kenwood DMX906S there are 3 settings, Low, High, and Off. I believe the Loudness that Pioneer uses is just On, or Off, and I’m not sure how Sony, or Alpine implement this feature. This thread will specifically focus on Kenwood’s version because that’s what I have to test, but I suspect the results will be similar across all brands.
This first graph shows the current frequency response of my system at a volume level of 15. This volume level is pretty low, certainly audible, but not particularly loud, especially while driving at any appreciable speed. I would consider it background volume level, you could hear it well enough to sing along to a song you already know, but you probably wouldn’t hear a new song well enough to learn the lyrics, it’s a pretty low volume level based on how my gains are set (more on gains later), but still a level I use when I have someone in the car and we are chatting, but still want to hear the music well enough.
![260824]( "260824")
The bottom line (sorry, I can’t tell what color it is, I’m not so good with colors, I should have changed this before saving the image) is the frequency response of my system at volume 15, with the Loudness Off. I need to do some work around the mid/tweet crossover, but that’s not relevant for this thread.
The blue line shows the same volume level with the Loudness set to Low.
The green line shows the same volume level with the Loudness set to High.
Obviously, the low end is boosted, and so is the high end, but the midrange stays (basically) the same. From 800hz to around 4khz the response is relatively unchanged regardless of whether or not the Loudness is Off, Low, or High. This is exactly what you would expect to see.
These boosts are what scare people. If you spend all your time tuning for a relatively smooth, and balanced curve, you don’t want the low end, or high end being boosted, right? There’s a chance of clipping the signal with that much boost in the low end, right? Well, not really, and here’s why.
This graph shows the same tune, but at volume level 30, instead of 15. The way my gains are set 30 is pretty loud, not unbearable, but around that “enthusiastic” level I mentioned earlier in the post. This graph also shows the response with Loudness Off, Low, and High, but you’ll notice how different this is than the previous graph.
![260825]( "260825")
At volume 30 the frequency response is exactly the same, regardless of whether or not Loudness is Off, Low, or High. The only difference is that with Loudness on (either Low, or High) the amplitude is higher, but it’s evenly higher, there is no bending of the frequency response. So, by the time you reach 30 on the volume level of your Kenwood stereo, Loudness isn’t doing anything at all (except adding a few extra clicks to the overall volume level), it only affects the response at low volume levels.
Due to this feature only changing the response at low volume levels, there is no risk of clipping due to the extra boost. This final graph shows all 3 measurements together, as you can see, even with Loudness on High the low end still measures lower than it would at volume 30. So, it is easily within the limits of your system, and you are not risking clipping at all by using this feature (as long as your gains are set correctly).
![260826]( "260826")
GAINS
Setting gains doesn’t need to be complicated, you don’t need an o-scope, and you really don’t’ need a multimeter, but the way you set your gains is still important for this feature to act appropriately. The stereo is not measuring the SPL to determine when to taper off the boost, it’s only basing the amount of boost on the actual number on the volume knob. If your gains are set too high, and you use the Loudness feature, then you may be at pretty high listening levels by volume 15, which means that there is a lot of boost happening. It’s important that your gains are set low enough that you are using most of the volume range within the head unit. On this Kenwood, 40 is the max volume, so a listening level of 30 is a good level for pretty enthusiastic listening. You can go a bit higher on the volume knob, and having some extra for low recordings is good, but you want your max volume to be up in this top ¾ range. You do not want to set your gains so that your max listening level is down in the 15-20 range. If you do that, the boost that Loudness provides will be unpleasant, and you could risk clipping, depending on the response curve you’ve tuned to, because you will never (or rarely) reach a volume level on the head unit where the Loudness actually tapers off.
That’s in for now, instead of fearing the Loudness feature, you now know what it does, and can choose to use it if you wish. I think that if your gains are set correctly, the feature is actually really clever, and I keep mine set to Low at all times. This gives me a perceived frequency response that matches my target curve over a much wider range of volume levels. Even at low volume, I still have good bass response, and dynamics. Even though the volume is low, it still sounds like music, and not just vocals. As I increase the volume, the effect tapers off, and by the time I’m at enthusiastic levels there is no boost at all, and I am listening to the response that I tuned for.
I hope you found this useful. I’m considering exploring some of these other built in “mystery” features, and posting the results here, if you all want to see the results. I'm undertaking a quest to see how good a basic active head unit, with limited EQ can actually sound, if the tuning features are fully understood, and used to my advantage. We'll see how far I can get with this Kenwood DMX906s before a standalone DSP is a must.
Thanks to Alex aka. Redliner99 for lending me his mic to take all of these measurements!
But, what do these features actually do, and should you be afraid of using them?
LOUDNESS
We’re going to take a look at a particularly interesting feature, the Loudness setting. If you aren’t aware of what Loudness is supposed to do, it is designed to boost (oh no!) the low and high frequencies of your stereo at low volume levels. The amount of boost is designed to taper off as you increase the volume.
What’s the point of the Loudness feature?
It’s actually a pretty clever thing. In order to understand the usefulness of the Loudness feature, you need to be at least somewhat familiar with the Fletcher Munson, or Equal-loudness curve (or contour). The wiki link is below, but basically what Fletcher Munson discovered was that our perception of frequency response changes depending on the amplitude of sound. At low amplitude (aka volume, aka SPL) we don’t perceive low or high frequencies as being as loud as they actually are. At high amplitudes, the lows and highs begin to sound as loud as they really are in relation to the midrange. To illustrate this, listen to a fairly dynamic song at a level you would consider enthusiastic. Nothing so loud that it’s uncomfortable, but the kind of level that you would listen at when you are really into the music. Make note of the frequency response, particularly how the lows, mids, and highs all balance out. Now, turn the music down to roughly conversation level, and you’ll notice that the perception of balance falls apart. The bass is gone, the highs are gone, and you just get mostly midrange. When you turn the volume down, the dynamics are gone, and the perceived frequency response changes. Instead of lowering all frequencies equally, the perception is that the lows and highs fall off much faster than the midrange as you turn the volume down. That is what the Flutcher Munson curves explain, and it’s the reason the Loudness feature exists.
Equal-loudness contour - Wikipedia
Now, let’s take a look at what the Loudness feature does from an objective standpoint, and help people understand if it’s useful, or if it really is the devil people claim. Most head units have a feature like this, on my Kenwood DMX906S there are 3 settings, Low, High, and Off. I believe the Loudness that Pioneer uses is just On, or Off, and I’m not sure how Sony, or Alpine implement this feature. This thread will specifically focus on Kenwood’s version because that’s what I have to test, but I suspect the results will be similar across all brands.
This first graph shows the current frequency response of my system at a volume level of 15. This volume level is pretty low, certainly audible, but not particularly loud, especially while driving at any appreciable speed. I would consider it background volume level, you could hear it well enough to sing along to a song you already know, but you probably wouldn’t hear a new song well enough to learn the lyrics, it’s a pretty low volume level based on how my gains are set (more on gains later), but still a level I use when I have someone in the car and we are chatting, but still want to hear the music well enough.
The bottom line (sorry, I can’t tell what color it is, I’m not so good with colors, I should have changed this before saving the image) is the frequency response of my system at volume 15, with the Loudness Off. I need to do some work around the mid/tweet crossover, but that’s not relevant for this thread.
The blue line shows the same volume level with the Loudness set to Low.
The green line shows the same volume level with the Loudness set to High.
Obviously, the low end is boosted, and so is the high end, but the midrange stays (basically) the same. From 800hz to around 4khz the response is relatively unchanged regardless of whether or not the Loudness is Off, Low, or High. This is exactly what you would expect to see.
These boosts are what scare people. If you spend all your time tuning for a relatively smooth, and balanced curve, you don’t want the low end, or high end being boosted, right? There’s a chance of clipping the signal with that much boost in the low end, right? Well, not really, and here’s why.
This graph shows the same tune, but at volume level 30, instead of 15. The way my gains are set 30 is pretty loud, not unbearable, but around that “enthusiastic” level I mentioned earlier in the post. This graph also shows the response with Loudness Off, Low, and High, but you’ll notice how different this is than the previous graph.
At volume 30 the frequency response is exactly the same, regardless of whether or not Loudness is Off, Low, or High. The only difference is that with Loudness on (either Low, or High) the amplitude is higher, but it’s evenly higher, there is no bending of the frequency response. So, by the time you reach 30 on the volume level of your Kenwood stereo, Loudness isn’t doing anything at all (except adding a few extra clicks to the overall volume level), it only affects the response at low volume levels.
Due to this feature only changing the response at low volume levels, there is no risk of clipping due to the extra boost. This final graph shows all 3 measurements together, as you can see, even with Loudness on High the low end still measures lower than it would at volume 30. So, it is easily within the limits of your system, and you are not risking clipping at all by using this feature (as long as your gains are set correctly).
GAINS
Setting gains doesn’t need to be complicated, you don’t need an o-scope, and you really don’t’ need a multimeter, but the way you set your gains is still important for this feature to act appropriately. The stereo is not measuring the SPL to determine when to taper off the boost, it’s only basing the amount of boost on the actual number on the volume knob. If your gains are set too high, and you use the Loudness feature, then you may be at pretty high listening levels by volume 15, which means that there is a lot of boost happening. It’s important that your gains are set low enough that you are using most of the volume range within the head unit. On this Kenwood, 40 is the max volume, so a listening level of 30 is a good level for pretty enthusiastic listening. You can go a bit higher on the volume knob, and having some extra for low recordings is good, but you want your max volume to be up in this top ¾ range. You do not want to set your gains so that your max listening level is down in the 15-20 range. If you do that, the boost that Loudness provides will be unpleasant, and you could risk clipping, depending on the response curve you’ve tuned to, because you will never (or rarely) reach a volume level on the head unit where the Loudness actually tapers off.
That’s in for now, instead of fearing the Loudness feature, you now know what it does, and can choose to use it if you wish. I think that if your gains are set correctly, the feature is actually really clever, and I keep mine set to Low at all times. This gives me a perceived frequency response that matches my target curve over a much wider range of volume levels. Even at low volume, I still have good bass response, and dynamics. Even though the volume is low, it still sounds like music, and not just vocals. As I increase the volume, the effect tapers off, and by the time I’m at enthusiastic levels there is no boost at all, and I am listening to the response that I tuned for.
I hope you found this useful. I’m considering exploring some of these other built in “mystery” features, and posting the results here, if you all want to see the results. I'm undertaking a quest to see how good a basic active head unit, with limited EQ can actually sound, if the tuning features are fully understood, and used to my advantage. We'll see how far I can get with this Kenwood DMX906s before a standalone DSP is a must.
Thanks to Alex aka. Redliner99 for lending me his mic to take all of these measurements!
I'll have to confirm that with some measurements. 
