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Alright, I've got the nakamichi CD-400 headunit and I'm actually curious how the sub level control works. It goes from -10 to +10 and if you go past -10 it goes to off. Now what I specifically want to know is.... With sub level controls what exactly does the headunit do to the sub level output to make it louder? When it is at 0 to -10 does it just cut the signal? and then from 0 to +10 it boosts the signal? So does it basically act like a bass boost would on an amp? And then if this is true would it be better to raise the gains and lower the sub level control so that there is no added boost and the signal would have less distortion? Or am I completely off base here? Haha.... sorry for soooo many questions, but I just want a good understanding of what this does to my music and how it affects it. Thanks in advance everybody!

 
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yes, it acts like the bass boost on an amp (somewhere in the manual it should tell you the center frequency). at some frequency (usually about 40Hz) it will either raise or attenuate the NF output signal at the rate you tell it to. it also affects frequencies other than the center frequency, thus boosting most of your bass.

you may know that 3dB=twice the power. so by boosting the bass 10dB, that's more than 8 times the original output. so chances are yes, you will clip the output. but if you listened to, say john mayer (not bass heavy by any means), you probably wouldn't clip the bass (although it would sound weird). your HU has maximum outputs (say 2V, 4V, 5V) and if you boost the output too much, you will clip. but if you stay within these bounds, you'll be fine. you won't gain signal clarity by cranking the amp and lowering the HU level. personally, i have my amp up a little too much, and my HU at -3dB usually. i have plenty of bass this way, and if i want more i can turn up the HU a few notches until the clipping gets bad. i also then know my HU is staying within it's bounds of clean sound up until 0dB for sure.

 
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So I wouldn't benefit by turning my headunits sub level down and then turning the gains up? It seems like turning the sub level on the headunit to zero and then adjusting the gains to where I want them would give me full bass as oppose to having the gains low and the headunit at +10 would give me bass but it wouldn't be as low and such because it is boosting a specific freq. more than it is the rest. Am I making sense?

Because when you turn the gains down a little bit and then turn the bass boost up a little, it doesn't seem like you get the lowest notes out as much because the higher bass notes are amplified by the boost. So it just seems like turning the gains a little higher so I can turn the headunit sub level down a little would give me more of the sound I'm looking for, while also giving me a little head room to play with if I ever want to crank the bass a little more. Also, how high do people usually go with the gains on their sub amp? I'm afraid to go to high although I don't think I'm clipping or distorting yet and I think I could probably get away with going a fair bit higher. But I dunno, I have a nak deck with 4v outputs supposedly.

 
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the scale on headunits is not decibel based, therefore, +10 db isnt 8 times louder than 0 db. its just a number, a fabricated made up number that no 2 companies use alike. i dont quite know if it boosts or not. some headunits dont, some do, check the manual.

 
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I tried checking the manual, it didn't say anything about the sub level control

 
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from crutchfield re: my head unit.

so on mine it is dB based... it goes -15 to +15 on the screen.

on a clarion DXZ835

i would guess that this + and - 6 is actually + and - 12dB (2dB steps). this is the same as it was on my pioneer.

so my assertion is that the numbers are not randomly chosen by the manufacturer in most cases.

 
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again, the decibel level is a relative scale. you can measure ANYTHING with decibels

 
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something 2 blocks away isn't 3dB farther than something 1 block away.

and yes, if one signal is 3dB higher than another, it's got twice the power.

as for the question,
you seem to have this down right. like i said, bass boost is only at a certain center frequency. it's put on for rap junkies mostly. it boosts where most systems will get loudest, 40-50Hz. but it is by no means musical. it affects the neighboring frequencies, but at a lesser rate (picture a hill, with 40Hz as the center and the outsides being say 30 and 50Hz). so you are right, you would get less low low end sound.

 
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So then at the same time, if it is just for a bass boost then how come I can go from 0 to -10 and OFF (which is just past -10) and the bass is completely gone even before I really get to off. I really can't hear anything then. Even at 0 its reletively hard to notice the sub so much. Thanks for all the information so far guys, you've been a good help

 
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the slope of the boost really depends on the HU and your settings. what affects the slope is called the quality factor, or Q factor. it is the ratio of the center frequency to the bandwidth. so in the example i gave before, the center frequency was 40Hz and the BW was 20 (50-30)Hz. 40/20=2. thats a fairly good Q, a sharp hill slope. now if the bandwidth was from 20-60Hz, the Q would be 1, or a more gentle hill. but in either case, if you make such an extreme change to the center frequency, you will have a big effect on the output.

the effect of the bass boost is only really noticable on these low notes. but technically it changes the frequency response of the whole output. see, the hill i described doesn't ever end. it just gets closer and closer to ending, but never goes away (like cutting something in half, you always have something left).

i'm trying to keep this fairly simple. hope it helps. remember that your rear seats are also helping to drown out your sound.

 
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Ok, so the headunit just doesn't have a very steep slope to the Q factor? Because if its at Zero to -10 the sub is just non-existant. And then obviously when its at off its well... off. haha... but anyways, The whole reason I'm asking about all of this is because I got my new nak headunit in the last month and have been trouble tuning my system to where it all sounds right. So its been kind of bothering me.

 
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then turn the gain on the amp up more. you really won't notice a small amount of clipping, and most HU's overrate the outputs anyways. so if you have the amp set at 4 for the 4 volt outputs, that's really pretty low. i have 5V outputs, allegedly, but my gains are set at about .8V for the fronts and about 1V for the sub. in general, metal subs tend to take more power to get going anyways (i assume the 87 series eclipse is aluminum).

 
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No, actually the sub I have is not allunimum. Its the eclipse with the black cone. Well I've got my sub gains up about half way up now(so .5v?) Where I had the gains before was probably closer to where it needed to be for the 4-volt outputs. The gain settings go from 0 to 1 right? Going up by .1 of a volt? Just trying to understand this better. I was playing with it this morning though and I swear it sounds like the sub fads when you go from front to back. Which is odd because I thought the sub output was non-fading. But I might be wrong. I know its wired up right because I double checked that. But when I fade forward the sub definately doesn't hit as hard. Again, thanks for all of the information and help! You're very knowledgable about all of this

 
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maybe did you connect to the rear output then? and not the sub or NF output? it doesn't get affected by fade.

bass is non directional. so those front speakers can provide some bass that you think is coming from the subs. thus fading back can seem to make the sub put out less.

what kind of box is the sub in? size? and how do you have it facing? location in trunk?

gain is really just a volume control. people knock audiobahn like crazy, but i do like on their amp i'm using right now the output power gauge. it's like a needle that shows how much power the amp is putting out (if it hits 0dB when I have the music about 3/4 of the way up i know it's set right).

 
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I know its on the right output because when I use the sub level control on the headunit it does indeed make my sub go crazy loud or very soft. The sub is in a hatch style box thats probably around 1cu. ft. (I think?) and it is in the trunk pressed against the back seat facing with the cone facing towards the rear bumper. I've got some more things I'm going to try this afternoon and see if it makes a difference.

 
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sub level isnt bass boost though, what a boost on the sub level is is just a general boosting of teh voltage from the rca's, not a boosting of the sub frequencies

and yes, 2 blocks is 3 db's more than 1 block, then 4 blocks is 3 db's more, and etc.