Will "sub level" affect amp gain

I am installing my sub woofer tomorrow and plan on setting the gain using ohm's law and a multimeter. My question is about the pioneer HU I have and it might be a dumb question.

I know to set all of the EQ and effects to off or flat when setting the gain. The HU also has a sub woofer level control built in that I assume I should set to zero. My question is will raising or lowering the subwoofer level on the HU affect the actual voltage the amp produces? I know it's all about matching levels but I am getting confused. I will list the components below.

Pioneer DEH-P9400BH
6.5" Alpine coaxials in doors
3.5" Kicker coaxials in rear pillars.
Both fullrange speakers are running off of the HU.

Kicker CVR 10" DVC 4 Ohm 400RMS
Kicker ZX400.1

The amp is actually bench rated at 480RMS.

Just a note this is going in an FJ cruiser. Thanks!

 

Yes, it will affect it.

If it has a true 0db, with a boost (+) and cut (-) adjustment, set it to 0. Then you can use it to adjust your bass up or down when listening to music.

With your gains set with a 0db test tone (as I assume you are doing with a multi-meter), you will rarely, if ever, approach full power when listening to music, so some adjustment to turn it up or down will come in handy.

 

Yes I will be setting the amp gain with the multimeter. Upon further research some say the "sub level" control is actually an attenuation so I should set it to max then set the gain. That way I can't induce clipping by upping the level but can attenuate it if I need to. Also on the HU I only have two of the high frequencies bumped up on setting normally so I may just set the gains on the sub like that.

 

That was why I mentioned if it was a true 0db with gain and cut. Alpine's (AFAIK) are all a cut only, with +5 as a 0db from the rest of the system.

If the pioneer is the same, I would set it at 3 (on a scale of -5 to +5) to give you a little bit of room to turn it up.

At 0db on a test tone, you will rarely, if ever, get full power out of the amp when listening to music. It isnt recorded at 0db...

 

Oh ok. I see what you were saying now. Thanks for the info!

 

Just basically doubling up on what Matt said. My amp is rated at 350W while my sub is rated at 250W. I set the amp gains to get a 320W output to the sub with a 50Hz test tone, considering that actual music will not drive it that high. I've not blown up my sub at all....

Also, I set the sub level on my Pioneer 4300 HU to zero for the gain settings.

 

I'm pretty sure the amp gains don't control how many watts the sub see's overall but not positive. Also something I was looking at this morning. This HU and all pioneers I have dealt with have a SLA setting. My XM radio is usually not as loud as other sources so I it set up to 4 to level out the sources. Does anyone know if this is going to affect the overall voltage? I don't want to set the amp by the cd source and the XM be higher.

 

1) Watts = Amps * Volts, so yes gains affect the actual wattage that the sub sees. You are measuring the V from the amp's outputs and varying the gain to set the V to get the desired high-end W from the amp.

2) yes, SLA affects output from the HU, so SLA setting will affect the output from the amp

3) Not a question asked, but I think you're starting to overthink this. If you are running the amp that close to the upper end (clipping level), I'd advise you to dial it back a bit to ensure you don't get to that level and leave a bit of headroom on the amp.

 

Thanks for the info. To be honest I have never set an amp using a volt meter. I always just did it by ear so I don't know what to expect really. I am doing it all this afternoon so I guess I will find out. I think I understand what you mean about the gains in relation to watts. You are basically setting the MAX watts the speaker will ever see from the amp??? I guess as long as the levels "sound" like they match regarding the SLA setting then I should be good?

 

What Lurkin said. Every adjustment you make to your head unit, including SLA adjustments, EQ, and volume knob will affect the watts going to a speaker. It may be minimal, but it affects it.

OP - you have it right in your last post. When setting gains on the amp you are setting the highest level the output will be *using the defined parameters on the head unit*.

By this I mean - If you set the head unit to 25 volume, EQ at 0, and the SLA wherever you like it, as long as you do not exceed these settings, your max wattage from the amp will occur when these factors (and the same music or test tone source is used) are matched.

With music, since you will rarely reach 0db as you do on the test tones, you will rarely reach the output max you set up.

If you start messing with bass boost, EQ, SLA, or turn the volume up over 25 (or your set number), you will provide more voltage out of the head unit (into the amps), and this will send more power out to said speaker (use the formula given by Lurkin above).

If you are comfortable setting by ear, do so. If you have to crank the gains on an amp (unless you have a VERY low output head unit), you probably need more power or more speaker, cranking the gains is not a bonus. If you hear clipping or speaker distortion, you have problems (though people can rarely hear less than 10% distortion on a subwoofer)

If you want to set with a DMM, do so, and then put some music in and listen. Make small adjustments to the gain/EQ to get it right, and rock on. A minimal amount of distortion for short periods of a song wont kill equipment, and one last time, music very rarely reaches the kind of peaks a 0db test tone does, so you have a bit of built in leeway there by default.

 

Thanks Matt. I believe I understand now.

 

Not necessarily. If the HU has enough Voltage to drive the amp to full Volume even at minimum gain (the control turned to the highest numerical setting) then adding more gain simply changes when it makes full power.

 

Correct, I did make the assumption that it was understood that there isn't infinite power (W) available by constantly increasing the gain (V).

 

Do you guys recommend using a 0db test tone or -3db? I tried to set it by listening last night but I just can't hear the distortion as well on lower notes as I can the highs. I am going to set it by DMM tonight using a 50hz tone. Everything flat including the sub level at 0. FYI the sub level on this Pioneer ranges from -20 something to +5 so that makes me think 0 would be a good setting with the sub level with a little room for adjustment.

Again I apologize for "overthinking" this but I tried last night and what sounded "good" to my ears actually sent the amp into thermal protection. I was playing constant low notes for a while though trying to set it.

 

Not sure what is "right", but I used a 0db 50Hz test tone with the sub level at 0, and all other settings flat. ...and set with a DMM

 

That is exactly what I was planning to do.

 

You just need a tone in the range the speaker will be playing. 50Hz will be fine for the sub. Then set it with the DMM. You're probably not going to hear the distortion with the tone. You'd set it by ear if you're listening for distortion. With the DMM use the 0dB tone and the DMM and you'll be good to go.

 

Ok I have a good one for you guys. I have them amp and everything hooked up. I have the gain set "properly" and no distortion when playing at high volumes. When playing at a higher volume the first night the amp just cut off. I thought o great I fried it. That was not the case though as it came back on after a few minutes and a few cycles of the ignition key. I then thought it had just got too hot which I thought was weird since I wasn't operating it outside of it's limits. I let it set for the night and on the way to work the next day it worked fine. I get in the truck to leave later that day and nothing! Protection light again! After I got home I tried and tried to make it work but it would not so I took it out and hard wired it to the battery to make sure it wasn't a ground or power issue which it was not. I then got mad, set it on the counter and left. When I came home I decided to give it another shot and tapped on it forcefully with my palm a few time, touched the leads to the battery and it came on!

The kicker rep I spoke to told me to setup a bench test and all that which I don't really have the resources to do and also said it could be a bad solder joint or something like that that is breaking when the amp heats up and reconnecting after cooling down and/or me hitting on it. What do you think?

 

Try a different sub. You might have damaged yours which would show the amp a short which will engage its protection mode.

 

It does this without the speaker connected as well. Goes straight into protection and will only come on with either time or hitting it or a combination.