Jeff Evans
It is also confusing with power and voltage. When two identical in phase voltages add they will produce a 6 dB increase in voltage which is double the voltage (= 4 x power) When  a voltage goes up by 3 dB you get double the power.
 

Just for academic's sake...this is confusing to me because I don't see how you get more power out of nothing.  In this case, we are not sending a single signal through a transistor that adds gain by robbing energy from the DC source, outputting the same single signal, with gain.  In that case we are dealing with Vout/Vin. 

Instead, we are summing two signals into one.  There cannot be anymore energy that what is already contained in the original signals.  In this case we are dealing with V1 + V2 = Vtotal. 
 
That just seems so different to me.  I'm obviously missing something here, which is not out of the ordinary, ha ha.  I probably need to dive into decibels again and get reacquainted.  Apologies if this seems like I'm kicking a dead horse, I just find in interesting and you seem to have a good handle on it.

 
 
 
 
 
 

I know what you mean about the EQ confusing matters Danny, but I tend to EQ the kick and the bass first. I take a lot more care in selecting kick samples and bass patches to go with each other - either the bass is bright and the kick subby, or the other way around. Then I complimentary EQ them both based on that. I think which kind of kick you go for really depends on the kind of track. I know what you mean about subby bass, but in the right kind of track a sub bass line can be heaven. I can't explain it but it takes me into another world to hear those kind of frequencies played in pitches that I can hear and follow. I've heard some great electronic mixes with that kind of subby bass and when it's controlled just right it can sit in the mix perfectly without sounding muddy or rumbly. And it's almost always paired with a brighter, clicky kick. In rock music though, I prefer it the other way around. I love the highs and textures of a bright sounding bass in guitar based music. 
 
I think the problem I have with figuring out kick and bass levels purely by ear is that I can't seem to make my mind up. I'll settle on a balance which I think sounds great, then I come back to it later and think "man, that sounds better the other way around." So I'll do that, then the next day I'm wanting to change it again. One thing I found about this kick/bass balancing trick is that it gets me into a ballpark (emphasis on the word ballpark) around which I feel consistently happy with the balance. Like if I start with that 3dB rule and play around with it a bit within a narrow threshold, I happen upon a balance which I'm liable to stick to. So I guess that for me, there's something in it. I'm sure everyone has their little tricks and shortcuts - like e.g. lowering the attack of a compressor until it hits the transient and then backing it off a bit - which work for some but baffle others. 
 
Sidechaining kick and bass has always seemed like a copout to me and so I've never done it. And I follow EDM production techniques with interest, synths and beats being my main area of interest. Honestly if you go on some of the EDM production forums and Reddits it's depressing to see how obsessed with sidechaining the kick and bass many of these kids are. It's almost like a religion to them. Personally I see absolutely no need for it, especially when you're working with samples and MIDI and you can just play with the arrangement so that the bass and kick hardly step on each other at all. 

It seems to me this tip is very much like the K-System where you set things to a similar average loudness. Same thing Jeff has been telling us about for years. Maybe it's over simplified. Like, maybe one person might take all of the drums in context and give bass equal weight. It seems to me this tip (bass = to kick alone) is actually to cut the overall weight of the bass in the mix as a whole. 
 
This is like using the spicy food meter from 1980 in some small town. :-)
 
Sometimes, not so spicy is cool. Sometimes spicy rocks. Well, most of the time spicy rocks.
 
@Danny ~ Great to see you.
 

OK, more math. Power = V^2/R. If we double the voltage (V), power (P) goes up x4. For twice the voltage, 20log(2) = 6dB. For x4 power, 10log(4) = 6dB. There's a common saying that "dB's are dB's". Both power and voltage go up 6dB when voltage gets doubled. But when you have two sinewaves of different frequencies, the voltage doesn't double although power does. It goes up 3dB. It's all a matter if the two signals being added are coherent or not. Coherent signals add 6dB since every single point of the waveform directly adds together. Incoherent signals only add 3dB since the signals add randomly. Another way to think of it is adding voltage is not the same as adding power.
 
Also, DAWs deal with voltage. Audio meters do, too, since sound pressure levels (SPL) behave like voltage (20log). Sound intensity behaves like power (10log), but we're not normally concerned with that.
 
Hmmm, not sure if any of this helps.

sharke
I know what you mean about the EQ confusing matters Danny, but I tend to EQ the kick and the bass first. I take a lot more care in selecting kick samples and bass patches to go with each other - either the bass is bright and the kick subby, or the other way around. Then I complimentary EQ them both based on that. I think which kind of kick you go for really depends on the kind of track. I know what you mean about subby bass, but in the right kind of track a sub bass line can be heaven. I can't explain it but it takes me into another world to hear those kind of frequencies played in pitches that I can hear and follow. I've heard some great electronic mixes with that kind of subby bass and when it's controlled just right it can sit in the mix perfectly without sounding muddy or rumbly. And it's almost always paired with a brighter, clicky kick. In rock music though, I prefer it the other way around. I love the highs and textures of a bright sounding bass in guitar based music. 
 
I think the problem I have with figuring out kick and bass levels purely by ear is that I can't seem to make my mind up. I'll settle on a balance which I think sounds great, then I come back to it later and think "man, that sounds better the other way around." So I'll do that, then the next day I'm wanting to change it again. One thing I found about this kick/bass balancing trick is that it gets me into a ballpark (emphasis on the word ballpark) around which I feel consistently happy with the balance. Like if I start with that 3dB rule and play around with it a bit within a narrow threshold, I happen upon a balance which I'm liable to stick to. So I guess that for me, there's something in it. I'm sure everyone has their little tricks and shortcuts - like e.g. lowering the attack of a compressor until it hits the transient and then backing it off a bit - which work for some but baffle others. 
 
Sidechaining kick and bass has always seemed like a copout to me and so I've never done it. And I follow EDM production techniques with interest, synths and beats being my main area of interest. Honestly if you go on some of the EDM production forums and Reddits it's depressing to see how obsessed with sidechaining the kick and bass many of these kids are. It's almost like a religion to them. Personally I see absolutely no need for it, especially when you're working with samples and MIDI and you can just play with the arrangement so that the bass and kick hardly step on each other at all. 

 
With you there, sharke. For electronic stuff, most definitely! Those subs are necessity for sure.
 
Ah, making up your mind. Now THAT is, and always will be the issue for me with kick and bass relationships. It's more real instruments than the electronic stuff where that sort of messes with me. I don't have a problem with the more synthetic stuff. You know as long as you're not distorting and that bass is pumping for the dance floor or rattling someones package tray in their car, you know it's right. LOL!!
 
But yeah, making up my mind whether I want to boost lows or just turn up my faders on those instruments can sometimes drive me nuts. Thankfully, I haven't made a bad call on something like that in years. I'm cool with a little bass light or a little kick heavy....that can be changed in seconds. There's just something about bass that I can't get enough of, yet when you feel it the way you like it...chances are, for certain styles of music, you're using too much.
 
I built a new studio about 2 years ago. The room is so tight and tuned, I can literally allow more bass in my mixes. The problem I had at first was...when I felt that much bass in my other room, I knew it was too much. Now every once in a while I'm a little scared to let it go when in reality....it's fine. I need to trust the gear and the room. LOL!

gswitz
 
@Danny ~ Great to see you.

Thanks brother G, great to see you also. :)

fret_man
OK, more math. Power = V^2/R. If we double the voltage (V), power (P) goes up x4. For twice the voltage, 20log(2) = 6dB. For x4 power, 10log(4) = 6dB. There's a common saying that "dB's are dB's". Both power and voltage go up 6dB when voltage gets doubled. But when you have two sinewaves of different frequencies, the voltage doesn't double although power does. It goes up 3dB. It's all a matter if the two signals being added are coherent or not. Coherent signals add 6dB since every single point of the waveform directly adds together. Incoherent signals only add 3dB since the signals add randomly. Another way to think of it is adding voltage is not the same as adding power.
 
Also, DAWs deal with voltage. Audio meters do, too, since sound pressure levels (SPL) behave like voltage (20log). Sound intensity behaves like power (10log), but we're not normally concerned with that.
 
Hmmm, not sure if any of this helps.

Actually, that helps immensely.  I'm embarrassed to admit I didn't square the voltage when computing power, which totally screwed up that simple analysis.  P=IE, and I seriously translated that to P = E/R...ugh...
 
And that's why I beat dead horsies!  It's worth the ah ha moment when someone helps you realize what you did wrong.  Thank you for taking the time.  

Getting right back to the original sound is pretty important too. Like when recording an acoustic kick for example, if you alter the drum tuning on both batter and front head the sound can change so radically. 
 
I have set up a kick drum e.g. my Sonor kick and had a decent mic either inside or in front of the hole cut on the front head. I hold the wooden beater in my hand and hit the batter head. Listening and recording the results. Start tuning the batter head bringing the pitch up, the subs can go away and a new punchy kick results. Lower the kick and the deep sound comes back in etc.. Another thing is the padding inside the kick. Just what it is and how it touches either or both heads. This is the fast transient response of the kick now. Just moving the padding around makes an immense change to the decay of the sound!
 
Working with samples is another good way to get control over your kick sound. Layering kick samples can also go a long way towards shaping the final kick sound right from below 40 Hz to all up into the mids etc...That is the place to alter the eq by altering layer levels in multiple kick samples.
 
Setting up bass EQ in the mixing stages really comes down to how we shape the bottom end of the bass track. Sometimes a steep HPF just in the right spot will clear away some mud and leave a punchy but still nice bottom ended bass sound.  Shelving the low end on the bass track just has a different sound to it. Not better. Or a shallow HPF e.g. 6 dB/oct just in the right spot too to reign in some silly low end bass energy.
 
Electronic music is different again. I produce a lot of it and the bass can be bigger and go lower in my opinion and it can sound amazing. Synths are much more capable in a way down in the very low octaves.  The playback system needs to be able to handle it though. Like live playback.
 
I have always found I have an approach to getting bass levels right in a mix rather than bass/kick levels. What I do is once I get the mix sounding pretty good I drop the bass out and get used to listening to the whole mix minus the bass.  (At this point setting your kick level in relation to the mix is also handy here because you can hear it for a start!) Then I switch over the small mono Auratone type speaker at low volume and listen to the baseless mix on that for a while. Then start pulling the bass fader back in real slow. If your bass sound is good and healthy and does have enough information in it so it is not just sub sound only then you will hear it come back in real fast. And stop when you feel the balance is right. It usually is for me a little lower than where it was before.
 
Setting bass level to kick level is tying the bass level to one thing only. I feel the bass level needs to be adjusted in relation to the whole mix in a way. 
 
The small mono speaker pushes out and makes far worse/obvious any levels of any part of the mix being too loud/soft.
 
The VU meter still does a good job at setting two levels of anything to be very similar or close. And as a result it will sound like it too.