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How to Set Your Gains

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Forum Name: Car Audio - Hot Topics
Forum Discription: Stickied topics from our car audio forum. Car Audio FAQs. Read First!
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=85479
Printed Date: September 24, 2021 at 10:21 PM


Topic: How to Set Your Gains

Posted By: boulderguy
Subject: How to Set Your Gains
Date Posted: November 11, 2006 at 2:42 PM


HOW TO SET GAINS

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The ADD version -

1. Play a typically loud music CD in your headunit. Set volume to 75%. Wear ear protection.
2. Starting with the amp gains at their lowest setting, slowly raise one gain at a time until you hear clipping from the corresponding speaker. This will sound like audible distortion.
3. Once you've found the clipping point, back the gain down until you no longer hear the distortion.
4. Repeat for any addt'l gains on the amp/amps.
5. Your new maximum volume setting on the headunit is 75%, never exceed that for happy, healthy speaker life.

(This is the quick & dirty method, it'll get you 80% to proper settings. Read on for the other 20%.)
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How to do things right -

What's gain?
Also known as input sensitivity, gains are the small, typically recessed "volume knobs" on most equipment between the speakers & the headunit. All amps have them, also many EQ's, line output converters, some crossovers.

What's it for?
The idea is to properly match the output from different pieces of gear so that each communicates the cleanest signal to the other, resulting in maximum performance and minimal noise & risk of damage.

Know your enemy - Clipping.
Clipping is the tech term for the distortion that occurs when an amplifier is pushed beyond it's capabilities. In simple terms it sounds like significant distortion of the musical peaks. So for instance a big drum strike will sound muddy or distorted when turned up, but remains clear at a lower volume. That's clipping. What's happening is the amp momentarily runs out of power.

To properly understand this w/o an engineering degree you need to know the difference between constant power (RMS) and peak power. Constant power, very simply, is the amount of juice your amp can produce consistantly. Since there are some standards for measuring this it is one of the few benchmarks we have for amplifiers. But since sound waves are exactly that - waves, with peaks & valleys - understand that an amp's output is never constant, it has to increase & decrease with the music signal.

The amp's "reserve power" is what it uses to deal with the peaks in the music. This is called peak power, or my favorite, headroom. Headroom is typically about twice the RMS power of an amp, but can only be sustained for a few milliseconds before the amp gets totally winded.

So a good way to think of this is a 10 yr old jumping on a bed - that's the music signal. The bed is the amp's RMS power, the ceiling above is the headroom limit. If the kid jumps too high he whacks his head - that's clipping. Do it a couple times & he'll survive. Do it repeatedly & there WILL be permanant damage. This is the single biggest speaker killer out there.

So the object of the game is to adjust the bed height (by using the gains) to the right height so the kid can jump around like a caffeinated monkey without ever whacking into the ceiling. So setting the gains properly allows you to get the amp's maximum output without overtaxing the equipment. With me so far?

A few other basics -
To do this properly you'll need a few things:

Ear protection. Stuff some cotton in your ears if you don't have anything better.

A test CD with a sine wave set to 0db, a 50-80hz stereo tone is ideal. This is important - it's far more accurate than using a music CD. You can purchase these at most any guitar or pro music stores, Amazon, or download a program to make your own. Making your own isn't recommended since there are a lot of variables in computers that can affect the final product.

If you have a crossover, you'll need test tones within the frequency range for each amp. For instance if you have a dedicated sub amp crossed over at 80hz, get a 60hz test tone. For your mains, work with a 120hz tone. If you have a 3-way or more crossover, adjust appropriately, just be sure the test frequency is within the bounds of the speaker range. Test each frequency seperately.

Fader, tone controls, loudness/expansion, etc.
Ideally you'll have the sound from your headunit/EQ completely flat on a normal basis. If so, be sure everything's this way before you test. However, if you KNOW you'll have the bass boost activated, some sort of expansion, or the tone controls preset in some way then go ahead & set them before you test.

Otherwise it's best to have everything flat. If you choose to adjust the tone controls later & leave them that way you can always repeat the process. Regardless, be sure the fader & balance are zeroed out.

Dedicated sub volume controls
A lot of amps have outboard sub volume knobs & headunits frequently have dedicated internal sub volume adjustments. If you plan on using these they should be maxed before setting your gains. If you're not going to use them, best to de-activate them.

Set all amp gains to their lowest point before starting. Usually full counter-clockwise.

Input sensitivity switches
If your amp has a selector switch for different input sensitivities, start by setting it to the highest setting. These are typically expressed in voltages, for example .2-1v, 1-3v, 3-8v. Start with the higher numbers (ex. 3-8v) (lowest sensitivity). If you can't get the amp to clip at those settings, try the next one down until you find the clipping point. You can disregard generally what the markings themselves say since there's no real standard for measuring that stuff. Never trust your system's well-being to those voltage numbers, they're just a guideline best ignored.

Work with one gain at a time.
For example, if you have a L&R gain for your front speakers, you'll be working with each side seperately. If multiple amps, unplug all but the amp you're working with. If a 4+ channel amp, typically you'll have only a single L & R gain, so treat it like a 2 channel. If it has more gains, isolate each & adjust seperately.

Play your test tone thru the headunit. Adjust your headunit volume to 75% of max.
This doesn't need to be precise, just be sure you know where this setting is b/c it's now the HIGHEST you'll ever turn up the volume on the headunit.

(But the amps go to 11...! You're using 75% volume because some CD's will be louder than others. Also b/c there's a small amp in the headunit that will clip if pushed too far. Trust me on this one.)

Now turn up the gain you're working with until you hear the tone quality change - it'll be a distinct change in the tone, there will be distortion. This is where your amp clips. Now turn the gain back down to just below where that distortion occurs. That gain's now set. Repeat for all other gains. Repeat for all other amps.


Final tweaking -
Have an EQ? Want to use the "loudness" button? Want to adjust the bass/mid/treble controls? If you're making minor tweaks (+/-1) there's no real need to worry about gains. If you're talking about bigger changes (+4/-3, etc) you may want to run the tones again to be sure you're still set right.

Also now that the gains are properly set you can adjust them DOWN to balance your system. Need more front volume but don't have a fader? Turn down the rear gains. Sub underpowered? Turn down the mains. The important thing is to never turn them UP from where they are, just down.


A few other notes -

Can't I just use an O-scope or DMM to set gains?
Sure, IF you know the exact output (rarely the rated output) of your amp and you're a freakin' genius with your toys. Generally more accurate & far easier to use your ears.

What about the gains on the EQ/X-over/line-output converter?
Ooh, good question. The general idea here is to follow the same process but use the gains that are the furthest UPSTREAM (I.E. closest to the headunit) and set all the others to their lowest setting. This will send the hottest signal possible thru all the components. Just remember that anywhere the signal splits you'll have to set them there also. For example, if you have a LOC & an outboard crossover you'll need to set gains on both, starting with the LOC. This can get tricky. Let your ears guide you.

What if my headunit says "9v output" and the amp only says "5v input?"
Eh, doesn't really matter. Again, there isn't really any set standard for measuring this stuff & it's usually just marketing. Also remember that music is a wave, not a line, so that rated output is usually a max, not a constant. Just set everything according to the above process, nothing changes.



Replies:

Posted By: 1lowgalant
Date Posted: November 15, 2006 at 8:21 PM

pretty nice write up, exect for the "kids jumping on the bed" analogy. i think haemphyst debunked that analogy in the clipping sticky.

and i highly disagree with your ears being more accurate than an o-scope. sure, the average enthusiest probably don't have a scope nor know how to use it, but your ears are far from accurate, just accurate for your listening preferances.



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Whatever you do, DO NOT let the white smoke leak out of the wires.....




Posted By: soultinter
Date Posted: November 29, 2006 at 7:12 PM
how do you do it w a DMM ?




Posted By: master5
Date Posted: November 30, 2006 at 1:33 AM
Unless you have a DMM that can read and display a sine wave..it can't be done. However, I do believe you can properly set gains by ear but you have to be on the conservative side..especially with subs because there could be clipping that can lead to overpowering the subs that you might not notice..but a scope will. This is even more critical with a bandpass enclosure since alot may be going on inside that your ear won't pick up.

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Posted By: boulderguy
Date Posted: December 02, 2006 at 1:35 PM
Of course an O-scope is the most accurate method, but if you have one & know how to use it - why are you reading this?

Using a DMM is a different story. You need to be really adept with it. Lots of ppl have differing philosophies on using a DMM, I've never seen ay definitive methods that are foolproof w/o being overly complex tho.

As for the "kids jumping on the bed" analogy - nothing wrong with that metaphor if it's used correctly. Which it is. Remember the idea is to explain a relatively complex theory in simple terms, so take it with a grain of salt.




Posted By: spaceman74
Date Posted: December 05, 2006 at 10:05 AM
Yes! The amp runs out of power but the speaker is begging for more. The VC's resistance goes way up as the voltage is going way down. The speaker then becomes "NON LINEAR" and pushes back on the amp causing it to clip. And at the same time, the VC is getting damaged due to the high risistance (heat). "UNDERPOWER".It is not a myth! And not to mention that its aggravated when the spekers are in a wrong size undamped box. I laugh at the guys that say " I have 1000 watts! (on a 12volt charging system)
They crank it up all the time and wonder why their subs keep blowing.

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Keep working! Millions on welfare depend on you.




Posted By: DYohn
Date Posted: December 06, 2006 at 1:36 PM

spaceman74 wrote:

Yes! The amp runs out of power but the speaker is begging for more. The VC's resistance goes way up as the voltage is going way down. The speaker then becomes "NON LINEAR" and pushes back on the amp causing it to clip. And at the same time, the VC is getting damaged due to the high risistance (heat). "UNDERPOWER".It is not a myth! And not to mention that its aggravated when the spekers are in a wrong size undamped box. I laugh at the guys that say " I have 1000 watts! (on a 12volt charging system)
They crank it up all the time and wonder why their subs keep blowing.

Speakers do not cause amplifiers to clip because they become "non-linear" or because their VC resistance has gone up.  This is complete nonsense.



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Posted By: garagexti
Date Posted: December 10, 2006 at 9:57 PM
I see it mentions to have subwoofer level controls in a head unit maxxed out before setting the gains on the sub channel...

I was curious if you still use the same setting procedure after the level control is maxxed to set the sub channel? Do you still use the same wave output (50-80)? Is it still easy to hear audible distortion with only the subs playing?


regards,

D




Posted By: boulderguy
Date Posted: December 11, 2006 at 12:19 PM
triple-yes.




Posted By: master5
Date Posted: January 13, 2007 at 1:32 PM

As far as "sub" level control you really want that set to full while adjusting the gains. Note that the sub control is NOT a boost....in other words it is not designed to give more power to the sub. It is used to compensate for the listeners preference or for different type music or recoring levels. However, if you allow any "headroom" on the sub control it will increase the chance of blowing subs..especially with "typical" listeners.

Many think the sub control is designed to increase the power, but think about it....if you didn't have the control (or if you unplugged a remote bass controller) the bass would not decrease...it would remain at the setting of the gain and equal to the MAX setting of the bass control. However I do agree with EQ settings to be flat during gain adjustment especially if any are on the amp. IMO an amp should not "shape" the sound...only add power, which is what an amp is for.



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Posted By: 1967type-1
Date Posted: November 06, 2009 at 10:47 PM
If you guys are Installers,does your shop carry AudioControl products? If so you should know that you can use the AudioControl "SA-3051" to set the amp gains.The same SA-3051 real time spectrum analyzer  you use to measure SPL,or set up equilizers.It has a sine wave generator in it.You can use it to see exactly what frequencies are clipping and where in the signal they are clipping.You can also use it to check crossover points in electronic crossovers (especially if you build your own modules),check voltage coming from headunits going to amps,The spectrium analyzer and SPL meter are only two of the many things you can do with this piece of equipment..It is a very versitile and valuable tool to have in an install bay.Every shop should have one.

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(o\_|_/o)
67 Volkswagen Type-1 {Beetle}
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AudioControlEpicenter,ESP, EQL,2XS,Alpine 2 MRV-1000,MRV-F-400,Alpine R-10 Element Triple Enclosure,R-8,Kicker MB-100,2 Alpine 6.5 compoment




Posted By: slapinf350
Date Posted: November 06, 2009 at 11:17 PM

I dont recomend doing that use a o-scope thats the proper way to set your gains



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If it flys floats drives or F***s rent it




Posted By: dp1084
Date Posted: November 17, 2009 at 8:41 PM
As far as I have heard before using ohms law to find the voltage given at RMS wattage for both the amp and the sub, the amp could be set with a DMM using the lower voltage. If this is true at what hertz would the highest wattage for a sub-woofer be used?




Posted By: dp1084
Date Posted: December 14, 2009 at 9:37 AM
So far the best idea for setting gains is using an O-scope? Must be rich people, show me a o-scope for cheap. figure that the voltage for a 4 ohm sub @ 250 watts is 31.6 volts this being true if your amp has a higher rms rating than the sub with the sub being 250 rms this works. get a test cd don't burn your own. turn all outputs such as bass boost and sub output to max. unplug the sub attach DMM leads to wires. find the frequency at which the amp you are using hits hardest. boost stereo to highest listening volume normally used. adjust amp accordingly to get a little below full rms.(leaving some headroom for higher power recordings) This is not foolproof if you use cd's and mp3 players it is recommended to copy the test disk and find which is putting out more power and adjust with that one.This is just what i have found to work for less than the price of your sub. If you don't agree then don't use it.




Posted By: incognyto
Date Posted: January 24, 2010 at 1:41 PM
this is the way that I set my gains also according to the jl audio manual's anyway's, i've setup some jbl amps in a chick's car this way. just going off the wattage the amp was rated for.

the equation is desired wattage or rated wattage x ohm load then square root the result. eg. I come up with 31.6 for my 500/1 into one of my 15" type r's dual 4 ohm paralleled. (500 x 2 = 1000 sqrt of 1000 is 31.6) this is with the gains set at 30/35 with sub cntrl at 10/15 with a 50 hz 0db signal then I have a bit of room for overlap or over driving. get's you very close to rated power output. then if the song's quiet most song's I hear won't even hit -6 db attenuation, you can turn it up past the 30/35 and 10/15. and also a 16+ db boost on amp if needed, i've used it on divetree music before haha makes the dixie chick's thump pretty hard!!




Posted By: incognyto
Date Posted: January 24, 2010 at 1:47 PM
even with all this info you still have to listen for distortion or clipping, quite a few people are oblivious to this and crank the gains on the amp's to high, I'm actually guilty of this also when I first started getting boom in the trunk, A couple buddy's still crank the gain's and think it sounds good no matter how much I tell them it sounds like poo. even after telling them they have to lower the gains because at half volume the sub's are overpowering allllllll of the mid's. I like SPL but it has to sound reasonable!! sub farts aren't good.




Posted By: sm00v31
Date Posted: March 31, 2010 at 9:49 PM
The discussion has only covered Subs. If using a DMM do the rules still apply the same to components? I have always set my stuff by ear.




Posted By: mcintosh-asylum
Date Posted: November 19, 2010 at 9:02 AM
but what about the old stethiscope trick for doing spl?

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4 soundstream xxx 15's :)
150.6 with 4000 watts




Posted By: haemphyst
Date Posted: November 21, 2010 at 6:34 PM
mcintosh-asylum wrote:

but what about the old stethiscope trick for doing spl?

And what trick would THAT be? How does using a stethOscope have any bearing on SPL?




Posted By: imking7141
Date Posted: May 13, 2011 at 3:49 AM
This is a very helpful guide, i will defitenatly try it tomorrow morning!
thank!

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chargers#1




Posted By: jomin1016
Date Posted: August 11, 2011 at 10:10 PM
What about this method? setting gains with dmm




Posted By: boulderguy
Date Posted: October 12, 2011 at 11:31 PM
^^ That's a great calculator, I've used it before. Nothing wrong with setting your gains that way using a DMM. Keep in mind the weak link is knowing the amp's ACTUAL power.

Quality equipment often comes with a birthsheet telling you actual test results - great, you're all set. This is maybe 1 out of 25 amps sold on the market today (guessing, it's probably much fewer).

Without that info it's easy to believe your $120 Sony/Crunch/Pyramid etc amp's claim stenciled on the front saying "2000 WATTS!"...So you set the gains to 63.2v...and your new hexagonal plastic subs with a magnet like a vault door erupt into flames...

Take-home message: Setting gains to a voltage with a DMM is great if you have RELIABLE power output specs.

.




Posted By: DYohn
Date Posted: May 14, 2012 at 10:16 AM

boulderguy wrote:

^^ That's a great calculator, I've used it before. Nothing wrong with setting your gains that way using a DMM. Keep in mind the weak link is knowing the amp's ACTUAL power.

Quality equipment often comes with a birthsheet telling you actual test results - great, you're all set. This is maybe 1 out of 25 amps sold on the market today (guessing, it's probably much fewer).

Without that info it's easy to believe your $120 Sony/Crunch/Pyramid etc amp's claim stenciled on the front saying "2000 WATTS!"...So you set the gains to 63.2v...and your new hexagonal plastic subs with a magnet like a vault door erupt into flames...

Take-home message: Setting gains to a voltage with a DMM is great if you have RELIABLE power output specs.

.

... or an oscilloscope so you can see the onset of clipping.



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Posted By: troy14
Date Posted: May 30, 2012 at 9:30 AM
There's one issue that I have with these methods, and by no means am I implying that they are incorrect, but its the same problem I have with the SMD device that has gained so much popularity, even being overpriced.

Anyway, the issue I have is that none of these methods are comparing the input and output stages. The amplifiers job is simple, take input signal A and increase its amplitude. If A in equals A out (at a higher voltage) then the signal is clean. If there are artifacts, it's distorted. (Quite possibly the simplest definition of distortion.)

I've seen people measure with an o-scope and just turn knobs until they get a square wave, but I still maintain that you must compare the input and output signals to determine if there is clipping.

That brings us back to another post about the Audio Control Spectrum analyzer... The key benefit to this (or like products) is that it's generating it's own output (the input signal) and comparing it to the system's output. All things being equally accurate, this is the best way to get the desired result. If you want to get the most out of your amplifier, then find a nice pre-amp that will make the work of your amplifier and give it all the headroom that it could possibly have.




Posted By: jason111
Date Posted: May 30, 2012 at 4:35 PM
I have used this method several times
https://www.youtube.com/watch?v=suX13VixU5k




Posted By: DYohn
Date Posted: May 31, 2012 at 9:24 AM

troy14 wrote:

Anyway, the issue I have is that none of these methods are comparing the input and output stages. The amplifiers job is simple, take input signal A and increase its amplitude. If A in equals A out (at a higher voltage) then the signal is clean. If there are artifacts, it's distorted. (Quite possibly the simplest definition of distortion.)

I've seen people measure with an o-scope and just turn knobs until they get a square wave, but I still maintain that you must compare the input and output signals to determine if there is clipping.
.

The typical "by ear" method we promote most often is intended that you first determine the max unclipped input signal then set the output to the max unclipped level.  Since we are not designing circuitry, this is close enough for normal safe operation of any car audio setup.



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Posted By: androidcaraud
Date Posted: December 27, 2013 at 9:32 AM
Thank you for sharing the useful tips. Its very valuable info.




Posted By: jetfuel08
Date Posted: January 23, 2016 at 9:08 PM
So when “clipping” is happing are is it because the sub doesn’t have ability to move that much? or that the amp can’t put out the power to make it do so?. I am asking because I have clipping on some songs. I’m not completely incompetent when It comes to this Amp stuff. I know not to have my gains all the way up. Could the box that I have be a factor in the way the Amp, and the subs perform? The box I have is a “PreFab” I have been told that Prefabs are Tuned high so is that another reason that I could be having this problem?

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Cody Robinson




Posted By: geepherder
Date Posted: January 24, 2016 at 8:48 AM
Clipping is when the amp can't produce enough voltage, so the peaks of the AC are "clipped" off.

On an oscilloscope, this looks more like a sine wave and a square wave got together for some "sweet love making".

This will sound similar to a sub overexerting itself, but that is distortion, not clipping.

If you have access to an o-scope, you can see if it is indeed clipping or if you're overdriving your sub.

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My ex once told me I have a perfect face for radio.




Posted By: boulderguy
Date Posted: January 24, 2016 at 9:38 AM
geepherder wrote:


On an oscilloscope, this looks more like a sine wave and a square wave got together for some "sweet love making".

^^^ HAHahahahahah, sweet love makin', nice ;)

There are a whole mess of reasons that distortion occurs at higher levels. If you think your levels are correct (you can always double-check with the DMM-voltage method), the next place I'd look is how well the box & sub are matched.

For example, if you're using a ported enclosure, is it tuned to the right freq for the sub? If sealed, is it solid enough to produce high SPL without resonating? Lots of threads about this stuff out there.




Posted By: prince504
Date Posted: December 29, 2016 at 7:11 PM
I noticed the SMD DD-1 uses 1kHz and 40Hz test tones. But the OP said to use 120Hz for the main amp (I assume a 4-channel amp hooked to the front and rear speakers).

Is using 1kHz the wrong way to do it? Having a hard time finding 120Hz test tones...




Posted By: DYohn
Date Posted: February 19, 2017 at 10:51 AM
1Khz is fine.

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Posted By: kenwood_nut
Date Posted: March 27, 2021 at 10:02 AM
Obviously SOMEONE knows their car audio stuff here! NICE write-up, especially for beginners in car audio!

I just have one thing to mention: equalizer/tone settings. I've watched a ton of videos about all kinds of different ways to set gains, and the best were with an O-scope, which I recently purchased. My head unit and amp are about to be replaced, so I haven't worried about using any tools to set my gains just yet. At this point, everything is set by ear and seems to be perfect.

But what I always wondered was if you set all your tone controls in your head unit to flat, then set your equalizer frequencies all to flat, THEN set your amp gains, the minute you turn up the frequency levels, won't you then introduce clipping by cranking up frequencies? The answer I found was YES! Several professional installers have done videos that suggest you set your amp gains with your equalizers (in the head unit and/or external) set they way you will listen to your music most. And this makes more sense.

If you turn your bass to flat and don't have it up when you set your gains, the minute you crank up your bass you're NOT going to like what can happen. SO, for this reason, once I get my head unit and amp plus 4 new speakers installed in the next few weeks, I'm going to try setting my amp gains FIRST with my equalizer settings the way I plan to keep them most of the time. You can always turn them down, but don't want to turn them UP if you set your gains with them at a certain level.

I'm sure this might sound like a bunch of crap to most of you, but it certainly makes sense to me. I'm not making this stuff up, I've actually saw several videos suggesting doing it this way. Once I try it, if I don't like the results, I can always set things to flat and do it all again. I'll set my head unit's equalizer to CLOSE to flat, then my external 7-band parametric equalizer will be left the way I listen to my music 90% of the time. If it works as I expect it to, I'll be happy! My new head unit has a built-in 25-band equalizer, so THAT going through an external 7-band might be frequency overkill in my opinion. So yeah, I'm going to have my highs way up where I like them, and my bass flat like it always is on my head unit (but turned way up on my bass level control on the equalizer.

Okay, time for everyone to tell me how wrong I am or how they can't believe I even posted this! I get sarcastic comments all the time on facebook when I offer advice from what I've learned in my 45 years around car audio, but it's usually from people younger than my own kid, so I just ignore it. As I mentioned above, I don't make this stuff up. Anyone who thinks I'm wrong about setting amp gains with frequencies adjusted above flat can watch the same videos I did. It would sure be more adult than slamming ME for posting this.

NO, I'm NOT saying the original post was by any means incorrect! I'm merely stating that there is an alternate way of setting gains that makes more sense to ME personally. The rest of you can do it the way stated at the beginning of this thread.

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