gain setting tutorial 2010

[profundus-sanus]

Since our old gain setting thread is pretty clustered figured it was time for v3.0

READ all of this before you start the process.
disclaimer.... you cannot get a PERFECT gain setting, period. its all trade off. an 0-scope is the best way, but they certainly aren't available to everyone..

Starting from the top

select your test tone

i personally suggest a -5db 60hz test tone. I'm currently attempting to host several test tones at different levels and frequencies. As stated above the db level of each test tone is based on personal preference. -6 db is the lowest i would suggest as it runs a slight risk of clipping, and a 0db tone runs virtually no chance of clipping, unless the music was clipped when produced.
you must be careful here as going from -6db to -3db = half the output power from the amplifier at reference level.
you can create your own test tones here.
http://www.wavtones.com/functiongenerator.php
here is a good argument for using negative db tones
http://www.davidnavone.com/heresHow/...evelSet222.pdf
if you wanna check out your music and see how high it gets look at it in audacity
Audacity: Download

Opening the crossover

You must ensure your crossover's will EASILY allow that frequency through. I'd suggest just set them wide open with the ssf all the way down and lpf all the way up... to ensure that your not getting output cut by those filters. Also if you have any lpf on your sub out on your h/u make sure that is turned as high frequency wise as it goes.
if your using a full range amplifier switch your crossover switch to fullpass

setting up your h/u

generally you want to turn your h/u to to 75% volume or as loud as you'll listen to it without your mids/highs distorting. this is your reference level, or new maximum volume in laymens terms. With pioneer h/u's i suggest turning the sub out all the way up (+6) and would do the same with alpines (+15). i can't comment on any other units as i've not used them.
remember to open up your crossover on your h/u.
turn your digitial multi-meter to AC voltage.
if your using an eq your going to want to use a custom tone which uses the same frequncy as your eq, although if used properly you should never gain with your eq, only cut. when doing that you don't need to worry about it. Remember loudness and other assorted mx boost settings do the same thing.
if your using an auto eq feature from pioneer or imprint from alpine then your somewhat on your own, as you'll have no idea what the cut/gain curve is.

Put the dmm on the amp

Hook the dmm up to your speaker terminals on the amplifier, with the speakers disconnected of course.
saz-3500d with internally paralleled + and -'s so it doesn't matter which terminal you connect to





mm100.4 4 channel
1 channel





2 channels bridged, works the same for a 2 channel amp bridged as well.

Figure out your voltage

voltage = sqrt( watts X ohms)
so if you have a 2500 watt rms @ 2 ohm amp this is how it would look
voltage= sqrt(2500x2)
v=sqrt(5000)
v=70.71
so, in this example, you then set your gain on your amplifier for your dmm to read 70.71
now, you don't always need to set your amplifier to its maximum output if the woofer can't handle it. IN that ccase you can use the wattage you know the woofer will handle if its lower than than what the amplifier can put out.
also if you know your amplifier is underrated as proved by other tests with an o-scope feel free to set your gains to that level.
here's a handy chart to figure out your voltage a less math intensive way.

Fire it up!

turn everything on and put that test tone on repeat at your reference volume you determined earlier.
dial in the gain knob until you find your desired voltage. once your there you can shut everthing down, take your tone disc out, and reconnect your woofers. THen you need to get your crossovers/subsonic filters back to where they need to be.

I can't get my voltage?

first and foremost make sure you have a quality amp. some amplifiers from boss, lanzar, pyle, soundstorm, etc WILL not do rated power and therefor will struggle to put out that voltage.
test your rca's voltage. with everything off disconect your rcas from your amplifier and sit them in a place where they won't touch anything conductive(ie bare metal, amp cases, etc). now throw that test tone back in and turn it back up to reference level.
again your dmm should be on ac voltage with your leads like so
whatever voltage reading you get should be within the amplifiers manufacture rated input voltage. most are rated between 1-9v...
if your not within range you may have to turn your sub out higher or your volume higher.
if you still can't get it turn your dmm to resistance with the leads placed the same way. you should have an extrememly high level of resitance here... if it is low or an open circuit you may have bad/pinched rca's that need replacing.

setting up line drivers

your going to set the line driver just like the amp with your leads the same way as shown above on and output rca and set the output level to whatever its rated at. then continue to set your gains on your amp. its not complicated but just wanted to clear that up.

[perfect_prefect]

nice, cant think of any questions that should be raised from someone trying to follow this but im sure they will come up with some

[SolemnSinner]

Hey pro,
When you say to set the Pioneers @ +6, is that for when solely using a -5db tone?

If so....

Where should we set it using a 0db tone?

[profundus-sanus]

pioneer h/u's sub out is a 1db gain per increment... so if you use a 0db tone @ 0 sub out you can turn it up to what you like.

+3 would be the same as a -3b tone + 6 would be a -6db tone etc

[SolemnSinner]

Originally Posted by profundus-sanus

pioneer h/u's sub out is a 1db gain per increment... so if you use a 0db tone @ 0 sub out you can turn it up to what you like.

+3 would be the same as a -3b tone + 6 would be a -6db tone etc

So using a 0db tone, set the sub out level on the H/U at +6 when dmm'ing?

Before I was using a 0db tone and setting the sub level on the H/U @ -6.

[KickinBlazer]

hmmm the voltage chart didnt show up....the only reason i ask is cuz i need it

[profundus-sanus]

chart shows up for me.. all pics are hosted in the same photobucket....

just do the math... its not that hard

[profundus-sanus]

Originally Posted by SolemnSinner

So using a 0db tone, set the sub out level on the H/U at +6 when dmm'ing?

Before I was using a 0db tone and setting the sub level on the H/U @ -6.

if you use a 0db tone and +6 sub out then your max output is the same as using a 0db tone.

if you use a 0db and 0 sub out then you can turn up to +5 later and get the same effect as a -5db tone

[SolemnSinner]

Originally Posted by profundus-sanus

if you use a 0db tone and +6 sub out then your max output is the same as using a 0db tone.

if you use a 0db and 0 sub out then you can turn up to +5 later and get the same effect as a -5db tone

Gotcha'.
Thanks.

[perfect_prefect]

<----cant figure out how to use the tone generator, maybe a tutorial on the next?

[SolemnSinner]

Ah.
Another question for you Mr. Profundus.

DMM'ing the gain with a 0db tone, with the sub out @ 0, 3/4 volume and then turning the sub level to +5 AFTER setting the gain will not clip the amplifier?

[perfect_prefect]

it will not clip the amp, because music unlike your test tone only reaches -6 to -4db. so this is what you are compensating for by turning your sub volume up after dmming with 0db test tone

[SolemnSinner]

Originally Posted by perfect_prefect

it will not clip the amp, because music unlike your test tone only reaches -6 to -4db. so this is what you are compensating for by turning your sub volume up after dmming with 0db test tone

Ok. Very nice explanation.
Thank you.

[Boosted77]

Where's the old voltage to watts chart?

[perfect_prefect]

its simple math...... do you really need a chart? look to the bottom left corner of your screen click the start button, open the calculator. take wattage X ohms, with that answer you hit the sqrt button and thats your voltage for said watts @ said ohms

[profundus-sanus]

the chart shows up on all 3 of my computers...

[crunkjuice1]

There is a link to "old thread" in the first post of this thread go to it right click and save image for future reference.

[dsktim]

ok do i need my subs hooked up so the amp can see a 1 ohm load to adjust the setting

[profundus-sanus]

Originally Posted by dsktim

ok do i need my subs hooked up so the amp can see a 1 ohm load to adjust the setting

no, as stated above disconnect the speakers to do this.

[dsktim]

thanks i saw that about disconnect but i thought i read otherwise somewhere and wanted to check thanks

[perfect_prefect]

i like all the new pics and now the v/wattage chart is showing up. nicely done pro.

[nx04gt]

very nicely done

[AndrewBR98]

very helpful!!

[SpeedEuphoria]

That test tone generator is junk IMO, after converting to MP3 with volume normalizing on, it said the -3db test tone i made had to be amplified by 14db and the -5db test to was adjusted 17db to normalize it. So it pretty much creates a low volume signal more then you think.

When testing with the DMM it was showing ~1/2 the VAC of what music was reading. This was with the tones as generated by the prog and no converting.

Cant someone just post a -3db 60hz and a -5db 60 hz tone so we dont have to mess with it.

OIC now how to make -3db and -6db in audacity, how about a -5db?

[profundus-sanus]

don't convert to mp3, keep it in wave or some other lossless format..

i'll google for a audacity tutorial later and link it here