setting my gains through JL tut

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/r7

Silver - Posts: 340

Joined: July 30, 2004

Location: Canada

Posted: September 05, 2004 at 1:31 AM / IP Logged

i found the JL tutorial on setting your Gains very informative, however, in relation to the stats they have for their amps, i have a SS Tarantula 800/5, and im wandering how i can find what my optimal voltage should be.

Tutorial can be found here

mainly i just want to know what my voltage should be, i dont want to overset the gains and completely defeat the point of using this method ;/

any help would be most appreciated. :-)

/r7

Silver - Posts: 340

Joined: July 30, 2004

Location: Canada

Posted: September 05, 2004 at 8:35 PM / IP Logged

errr took me this long to find it was posted in General discussion, can a mod pls move it to the appropriate forum, maybe i'll beable to get a response.

btw - if there is a formula to find the voltage im looking for, pls lemme know :-)

stevdart

Platinum - Posts: 5,816

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Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: September 06, 2004 at 8:38 AM / IP Logged

The Ohm's Law formula E = sq rt ( P * R )...you'll also see it written as E = ( P * R )^.5 Your amp RMS rating is 4 channels at ___ watts @ 4 ohms, and 1 channel at ___ watts @ ____ ohms. You probably have one gain for two channels, say 1 and 2. Read the terminals at channel 1 while setting gain and then verify the same for channel 2. Use the one that has the highest number. Same for channels 3 and 4. And use the terminals you have the sub hooked to for the mono channel. Use the load impedance you are using for the sub, 2, 3, 4 - whatever it is to fill in the blank.

Example: I have a 50 * 4 amp at 4 ohms, and a sub amp at 200 * 1 at 4 ohms. I adjust to 14.14 volts output at each of the main amp channels, and adjust the mono amp to 28.28 volts at the output terminals.

You are using a test CD with recorded frequencies in the range you are testing for?

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

/r7

Silver - Posts: 340

Joined: July 30, 2004

Location: Canada

Posted: September 06, 2004 at 10:29 AM / IP Logged

yeh i created a cd with different tracks for various frequencies.

i just wasnt sure what voltage to raise the gain setting up to without clipping.

thanks for the help stev, didnt understand it all, but i'll read it over n over till i get it :-)

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: September 06, 2004 at 10:37 AM / IP Logged

If you will list your amp ratings, and the impedance loads you are putting on it, we'll verify the voltage you should set gain at.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

/r7

Silver - Posts: 340

Joined: July 30, 2004

Location: Canada

Posted: September 06, 2004 at 11:11 AM / IP Logged

thanks,

my amp puts out:

50watts x 4 channels @ 4 Ohm

400watt x 1 channel @ 2 Ohm

i tried the formula E=sqrt(50*4) and came to 14.14 and with my 400watt channel E=28.28

With these values, all i should have to do is

set my HU @ 3/4, set my gains all down, disconnect my speakers from the amp, and test the channels and raise the gain to 14.14 and leave it.

btw, my digital multimeter i purchased has 2 AC Voltage settings, 200 & 750, i was wandering which one i should set it at?

http://shop.store.yahoo.com/toolsplus/gbegdt-190a.html

The CD i've created has 10 tracks of frequencies ranging from 50hz-100hz and then a 1000hz track as well, i plan on filling in some gaps (as if its needed) and just 'repeat' each track as needed. when testing.

/r7

Silver - Posts: 340

Joined: July 30, 2004

Location: Canada

Posted: September 06, 2004 at 2:01 PM / IP Logged

i set it to 14.1 (closest i could get), one channel was more powerful than the other so i set the 14.1 on the highest, should work.

I used 50hz for my rear deck (my only 'bass' im getting till my sub is installed), my rears are set to low-pass for the time being, when set to full or high, they have too much fill that it ruins things,

thanks for the help stev, for the help proved very useful, after i finally wokeup, and read what you posted :-)

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: September 06, 2004 at 3:40 PM / IP Logged

Looks like you nailed it, /r7. The meter will read best at the lowest setting closest to your target number. Mine has a 20, then goes to 200, so if I'm using the 20 range and get a reading over that, an error shows. So you should use the 200 setting on your meter. But I'm guessing you already figured that one out...;)

I take it you are using just the four channels for mains on the amp right now and saving the mono channel until you get the sub? Yep, I think so...

Glad to be of help with the limited amount of knowledge I have gained here.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

/r7

Silver - Posts: 340

Joined: July 30, 2004

Location: Canada

Posted: September 06, 2004 at 6:41 PM / IP Logged

yeah thats partially right.

im only using my rear channels (laughs) its sad, i wish i could install my components, but after taking off most of the passanger door panel yesterday, the mounts for the 5 1/4's that are in there right now will not fit, and i dont feel like messing up the current mount to fit them in. so i will just leave it to professionals, this way i dont have to worry about a botched job because of my in-experiance, and lack of tools and accessories to make the job easier. its a hit to my pride but i'll be glad once its installed and payed off :-).

but knowing howto set my gain with this meter is quite a handy bit of knowledge.

i shouldnt have to worry about over-powering the speakers if they can handle 65rms eh (having the volume within reasonable limits), not to imply i'd blow them but im wandering if they are bottoming out, i have to play with my fader for the front/rear alot and i dont know if doing that adds more power to the back speakers when fading it from the front to back so i can hear the noise.

anyways, back to cruisin around.

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: September 06, 2004 at 7:06 PM / IP Logged

The thing about fading is this: you fade to the rear and the fronts get lessened. Fade to the front and the rears get lessened. Nothing gains, just something loses. So there is no increase in power to the end you want to hear most, just a decrease in the end you want to hear least.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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