setting my gains through JL tut
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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=38618
Printed Date: May 15, 2024 at 6:02 PM
Topic: setting my gains through JL tut
Posted By: /R7
Subject: setting my gains through JL tut
Date Posted: September 05, 2004 at 1:31 AM
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. :-)
Replies:
Posted By: /R7
Date Posted: September 05, 2004 at 8:35 PM
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 :-)
Posted By: stevdart
Date Posted: September 06, 2004 at 8:38 AM
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.
Posted By: /R7
Date Posted: September 06, 2004 at 10:29 AM
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 :-)
Posted By: stevdart
Date Posted: September 06, 2004 at 10:37 AM
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.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: /R7
Date Posted: September 06, 2004 at 11:11 AM
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?
https://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.
Posted By: /R7
Date Posted: September 06, 2004 at 2:01 PM
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 :-)
Posted By: stevdart
Date Posted: September 06, 2004 at 3:40 PM
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.
Posted By: /R7
Date Posted: September 06, 2004 at 6:41 PM
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.
Posted By: stevdart
Date Posted: September 06, 2004 at 7:06 PM
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.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: /R7
Date Posted: September 06, 2004 at 7:32 PM
awesome :-), i was hoping it worked like that, but i wasnt sure if thats how things were done (to me it seemed logical though)
so now at least i'll beable to know if its bottoming out, its too loud without worrying about the fade.
Posted By: SnomanF150
Date Posted: September 07, 2004 at 3:53 PM
In my experience, most every JL audio Amp I've installed, the gain has been set at just about 10 to 11 o'clock. That will usually be max rated power with no clipping. I have a paper somewhere I got at a training seminar somewhere if your interested. (this is tested with 1kHz)
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George
David's Car Stereo
Baton Rouge, LA
Posted By: /R7
Date Posted: September 08, 2004 at 12:26 AM
thanks snoman, but its no bother :-), gotter set, figured the formula out so its all good :-)
Posted By: TonyPTX
Date Posted: September 11, 2004 at 12:30 AM
This has been a very insiring thread to say the least....a basic question and it gets into the old funny business of how Amp Manuf. rated their amps... For the above stated equations, is the power listed (50W x 4 channel @ 4 ohm) the RMS power the Dynamic power? The reason I ask this is because I just finished installing a new setup with a new Fosgate Punch 4004 (highs) and an old MTX Thunder 202 amp for my sub. The Fosgate is CEA-2006 complaiant and lists the nameplate RMS power @ 14.4 VDC of 50W x 4 @ 4 ohm (Ironically the test sheet that's packaged w/ the amp had 99 RMS Watts/channel @ 4 ohms, but I think this is a typo because the name plate RMS power @ 14.4 VDC of 100W x 4 @ 2ohm. HOWEVER.....the MTX is a bit older and so, it has two seperate nameplate power ratings (RMS @ 12.5 VDC of 140W bridged into 4 ohm) and (Dynamic Power @ 14.4 VDC of 200W bridged into 4 ohms) with a max input of 2.5 Vrms. The factory acceptance Test sheet just shows "165W RMS All Channels" My question now is....on the MTX, should I be using the 140W value or the 200W value? The sub is a RF Z-Punch 10" SVC @ 4 ohms. Secondly, the HU is an Alpine 9805 with 4V max on the pre-outs. Seeing 2.5Vrms on the MTX is making me wonder if I need to adjust the gain on that amp all the way down (or do I need to get it replaced for compatability?) TonyPTX
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