how to set gains corectly with a volt meter.....

[97proLX]

not sure if this is posted yet or not but ill post it up incase you guys need help. remember your gain setting is to match the power of the head unit.the gain is NOT a bass volume.
items needed:
1.digital volt meter
2.cd with a 50hz test tone(or if this is for components 1khz)both must be recorded in 0db reference level in the frequency range.
3.beer
---
the formula for this that i am going to use is watts X impedence= sq rt.
disconnect your subroofers(or components) set all your bass and treble at flat.turn your gains all the way down. pop in your cd with your test tone. pop open your beer and take a swig. now connect the digital volt meter your amp, +to + and - to -.
make sure the volt meter is set on AC VOLTS, and everything is connected correctly.now find out the wattage on your amp, for example if your amp is a 1000 watt amp youll take 1000 and multiply it by the impedence of the speakers. so take 1000 X 4 and that will be 4000, then you find the square root of that. which in this case would be 63.25 volts, so there you go. if its a 2 channel amp then you take and divide that by 2. so we will need to see 31.6 volts per channel. so now you turn up your cd player to the absolute loudest you will be listening to it(up to 3/4 of the way up MAX)
now adjust your gain until you see the amount of voltage you came up with before, in our case it was 31.6 volts. now take out the digital volt meter and put it on the other channel and repeat what you just did. now hook your subwoofers or speakers back up and back the gain down a smudge so you have some room to mess with it. now slam your beer and your done, congradulations. if you got this far you have done something most audio install places dont know how to do. pat yourself on the back.

 

[97proLX]

now to find the wattage your amplifier is throwing out= youll need that same volt meter with a digital display and test cd.
you disconnect subwoofers(or speakers) and hook up the volt meter to the amp + to + and - to -. and ill use the same ratings as previous.
so say i got 31.6 volts out of each channel you will take that and times it by 2 for bridged mode, so now you have 63.25....now you take and times that by itself. 63.25 X 63.25= 4000.5625 then you will divide that by the impedence of the speaker....so 4000.5625 divided by 4 = 1000.14...there we go we found out we are using a 1000 watt amplifier.
good luck on this guys, if you have any more questions you can PM me, or post in here.

 

[97proLX]

for a good tone generator free click here

 

[got wake?]

that's one method, but i've still found it better to adjust by ear. since the impedance of the driver is not constant, your method doesn't always work properly. the *best* method is to use an O-scope, but not everyone can afford one. if i use a volt meter, i only use it to find the point where the amp starts to clip (AC voltage no longer goes up), and use that point as a reference to not go over, or if i do, just a little, since a little clipping through a sub is usually not audible.


here's what i recomend for setting the gains of a sub amp:

1) set the gains of the sub amp on minimum.
2) play a song that has the most bass you'd ever play through your system at full volume based on the other speakers (NOT full volume on the HU).
3) slowly adjust the gain of the sub amp up until the bass blends in with the rest of the speakers to your liking, as long as it does not cause audible clipping.

 

[memo79]

What is this "audible clipping" you speak of, master jedi?
Is it a loss of volume? a cd-like skip? what, what???

 

[97proLX]

that's one method, but i've still found it better to adjust by ear. since the impedance of the driver is not constant, your method doesn't always work properly. the *best* method is to use an O-scope, but not everyone can afford one. if i use a volt meter, i only use it to find the point where the amp starts to clip (AC voltage no longer goes up), and use that point as a reference to not go over, or if i do, just a little, since a little clipping through a sub is usually not audible.


here's what i recomend for setting the gains of a sub amp:

1) set the gains of the sub amp on minimum.
2) play a song that has the most bass you'd ever play through your system at full volume based on the other speakers (NOT full volume on the HU).
3) slowly adjust the gain of the sub amp up until the bass blends in with the rest of the speakers to your liking, as long as it does not cause audible clipping.

i wouldnt really reccomend doing it this way though,unless you have done this alot before and feel comfertable doing it and or are used to it... because its a crap shoot on this, its like a 1 in 10 chance its set correctly. but yes an o-scope is much better, and you can find out distortion and everything, but not many people have an o-scope.

 

[vindication]

here's what i recomend for setting the gains of a sub amp:

1) set the gains of the sub amp on minimum.
2) play a song that has the most bass you'd ever play through your system at full volume based on the other speakers (NOT full volume on the HU).
3) slowly adjust the gain of the sub amp up until the bass blends in with the rest of the speakers to your liking, as long as it does not cause audible clipping.

this is how I've always done it, and guess what, it never fails

 

[got wake?]

i wouldnt really reccomend doing it this way though,unless you have done this alot before and feel comfertable doing it and or are used to it... because its a crap shoot on this, its like a 1 in 10 chance its set correctly. but yes an o-scope is much better, and you can find out distortion and everything, but not many people have an o-scope.

how is setting it correctly anything EXCEPT properly blending it in with the rest of the system? you don't have to max out the output of the amp.

 

[got wake?]

What is this "audible clipping" you speak of, master jedi?
Is it a loss of volume? a cd-like skip? what, what???

clipping is when the output reaches max voltage output, but the user tries to get more output. the only way to increase the output without increasing the voltage is to increase the amperage output. when analyzing this through an oscilliscope, you'd see perfect sine waves, just before clipping. once you reach the point of clipping, the top and bottom of the waves are flattened. full clipping is a square wave, rather than a sine wave. it usually takes a bit of clipping before you can hear the clipping through a subwoofer. clipping can help for SPL comps, but for daily driving it's a risk not worth taking. the sub doesn't move any further, since the voltage is not increased any, but there will be more amperage flowing through the sub. the higher the amperage, the hotter the sub gets. if the sub isn't moving any further, then there is no more cooling with clipping than without it, but there is more heat generated. that heat will kill the sub.

 

[Poseur]

This is just skimming the surface of somthing in a mannar that could quite possibly do more harm than good.

 

[talon4x4]

When you say find out the wattage of your amp, you are reffering to RMS not max power, correct??

I defineltly think that is a great starting point for tuning your system. JLAudio has a little movie on their website showing exactly how to do what you described. So that method can't be that bad, as some have pointed out.

 

[Badger Biker]

I used the DMM method in the past and it worked fine for me. (Utter newbie.)

I would like to see someone with an experienced ear try and set everything though, so I could learn that way.

 

[got wake?]

When you say find out the wattage of your amp, you are reffering to RMS not max power, correct??

I defineltly think that is a great starting point for tuning your system. JLAudio has a little movie on their website showing exactly how to do what you described. So that method can't be that bad, as some have pointed out.

problems with their tutorial:
1) they make the assumption that you are only going to play the HU up to 3/4 the volume. i've had systems that didn't need to be turned up half way to reach full volume (did that so the volume would go up faster), and my current system can be turned all the way up on the HU, since i'm using optical output, so there won't be any HU clipping at full volume.
2) they give you the output voltages for their HU's, however not many manufacturers offer that. if you know the rail voltage, it's ok to use it, if you need to achieve full potential out of the amp. but what happens when you don't need the full output of the amp?


the tutorial is decent for their amps, given that they specify the voltage you need to find. however they don't take into account the difference in impedance from sub to sub. i've seen 4 ohm subs that measure in as high as 4.2 ohms, and as little as 3.2 ohms. that'll cause a few issues. also, the impedance changes based on the enclosure the sub is in. look at some impedance graphs for futher info.

 

[talon4x4]

I'm only using a single sub DVC and I already measures the impedence at 4.05, so I just adjusted the numbers. I'm using an Alpine HU and never turn it up past 29(35). So it should be a decent way to start out, correct?

 

[got wake?]

I'm only using a single sub DVC and I already measures the impedence at 4.05, so I just adjusted the numbers. I'm using an Alpine HU and never turn it up past 29(35). So it should be a decent way to start out, correct?

yeah, if your only goal is to set the gains to the amps rms power. but i can think of a ton of amps that put out well over their rms power, so using this method cuts off usable power. not having a proper understanding of how the AC voltage output works and trying to adjust your gains by that will lead to problems, whether it be unbalanced blending, too much or too little power, or over exerting the amp. just cause it's supposed to be able to put out 1600 watts rms doesn't mean it really does. in that case, you may high the AC voltage with no load, but as soon as you hook up a load, you end up with problems.

 

[memo79]

2.cd with a 50hz test tone(or if this is for components 1khz)both must be recorded in 0db reference level in the frequency range.

And where, on this earth (at least the part that consists of the internet) can I find this 50 hz test tone to download? I've been looking for a while now.

 

[FrigginGLI]

And where, on this earth (at least the part that consists of the internet) can I find this 50 hz test tone to download? I've been looking for a while now.

Most test cd's will have a 50 hz tone on there.

 

[memo79]

Most test cd's will have a 50 hz tone on there.

Yeah, see that's my problem. When I walk into an audio shop and ask for a cd that has audio test tones, I get this (uhm) (shrug) . Hence my efforts at trying to find it online.

 

[talon4x4]

Come on you guys have google.....don't ya?!?! Here is where I got mine and they work great. Each tone is 10 seconds long, so just use repeat. This guy has everything from 10hz-1000hz, he also has a couple of sweeps. You can get the individual tones or grab them all in one convient zip file. I used Nero to convert them on the fly to .wav and burn them to an audio CD. Have fun! Maybe somone could get the link stickied for everyone to use. It doesn't have all the features of say the Sheffield Lab test CD, but hey, there FREE!!

http://www.snapbug.ws/sinewaves/

 

[memo79]

THANK YOU!!!!

I did try to google it, but I guess I just wasn't looking the right way.