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Discussion Starter · #1 ·
I have four amps, set up like this:

one JL HD 600/4
bridged down to two channels feeding the front mids (3 ohm)

another JL HD 600/4
two channels to the front tweeters (6.5 ohm)
two channels to the rear coaxials (4 ohm)

(2) JL HD 750/1s to (2) subs (2 ohm)

I was running around with one sub amp installed and therefore only one of my subs hooked up. I had set all of my gains using a DMM back when I put in the other three amps, and for months it has all sounded pretty darn good. After setting all of the gains last time, I noticed that the MX (Media Expander) was switched on at my Alpine head unit. In the past, I've kept the MX turned off and used my 701 to tune the sound to the way I wanted it. I knew that turning MX off at this point would necessitate me resetting the amp gains to get everything perfect. So today I decide to install the second sub amp and reset the gains on all 4 amps while I was at it. This is where my day got frustrating.

Let me first say that I have set amp gains with a DMM many, many times. I use 50hz, 1000 hz, and 12000 hz test tones to set the subs, mids, and tweets.

Each of the JL amps has an input level switch. My processor has 4V output, so I start out with the amp input setting on "high". My target voltage for each sub amp is 38.7V. With the switch set to "high", turning the gain all the way up still only gets me to 21V. So I turn the gain all the way down and put the amp input level switch to "low". Now, even with the gain all the way down, I can only get down to about 59V.

So there is a range between 21V and 59V that I cannot get to no matter how much I manipulate the gain knob. That sucks, considering my target voltage is 38.7V. This happened on both sub amps.

Now on to the other amps. Setting the gains on the amp for the mids was a breeze. The target number was 30V, and I got there no problem.

Now to the amp that powers the rear speakers and front tweets. The manual calls for 24.5V setting for each stereo set of outputs. Even with the gain cranked, I can only get to about 22V. That doesn't seem right. I checked and rechecked everything, but kept getting the same results. I have never liked having a gain knob turned up all the way, and have never needed to do so, but here I am with it cranked and still can't get to 24.5V.

So I leave it set that way for a minute, hook everything up, turn the volume down to a very low level to start, and dig for a CD. Before I put the CD in, I notice a faint hissing sound up front. It's nothing crazy, but to me, it's noticeable. My experience with these amps up until now has been that they are nearly inaudible when there is no source material, even with the volume cranked. Now I'm getting this hissing sound from up front, and it doesn't seem to change much whether the volume is on 2 or 25. I immediately reach over and turn down both gain knobs on the amp feeding the tweeters and rear speakers. The hissing went away. I knew having those gains cranked wasn't right.

I throw in a CD and start slowly raising the volume at the head unit. Right away I notice that I can not get the volume up even half as far as I usually do before everything is LOUD. It's clear to me that all of my gain settings are out of whack.

I've gone through this whole process successfully with the only things changed being Slash amps instead of the HD amps. Same meter, same test tone CD. I have even gone through the process successfully with these HD amps a few months ago, with the only difference being the MX setting on the head unit.

I even used two separate mutimeters, thinking that one of them might be the problem. They both gave me identical readings.

My frustration level was boiling over, so I stepped away from the whole thing for the night.
Anyone have any ideas on what could be going on here? Anything to check for?

Maybe I'm doing something wrong. Something very simple that I overlooked. The fact that it's not just one amp in the bunch that's giving me trouble makes me believe that the problem is something else.

I'm open to questions and suggestions directly related to this issue. I'll probably dive back into it tomorrow and hopefully get it all squared away. As a last resort, I could set everything by ear, but that's not my preferred way of doing it.

Thanks for taking the time to read through this long a$$ post.
 

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Thanks for taking the time to read through this long a$$ post.

Seems you're addressing me so...

1] turn HU up as far as it will go without distorting [ midrange will work for this ].

2] adjust tweeter amp gain

3 adjust mid amp gain

Adjust sub amps gains....

you are done when music is as loud as you will ever listen to it without distorting.

Hiss is a common sign of having gain set too high [think ratio ];)

Ideally, hottest signal from HU will allow lowest gain needed :cool:

G'Luck
 

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Discussion Starter · #3 ·
Thanks for taking the time to read through this long a$$ post.

Seems you're addressing me so...

1] turn HU up as far as it will go without distorting [ midrange will work for this ].

2] adjust tweeter amp gain

3 adjust mid amp gain

Adjust sub amps gains....

you are done when music is as loud as you will ever listen to it without distorting.

Hiss is a common sign of having gain set too high [think ratio ];)

Ideally, hottest signal from HU will allow lowest gain needed :cool:

G'Luck
Thanks for the input, but I'd rather not set it by ear.
 

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If I came up against the same thing, I would send an email to the manufacturer.

Inquire about modifying the range on the high and low settings [ figure somewhere around $300.00 ].
 

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You should have your input sens. set to "low" for 4v input. I've run into the same problem, I was told that anything above 6v input to use high, anything below to use low. Your problem seems wierd though....
 

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I'm a little confused. Is there another way to set gains for amps? Would that include a multimeter or equipment that is able to read out THD or something along those lines?

I'm not trying to be a jerk, it's a real question :)
You can use a DMM to set to correct voltage, a scope to find out your exact point of clipping, or you can use your ear and test tones.
 

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I
Maybe I'm doing something wrong.
You're using a DMM to set your gains is what's wrong. Don't use a DMM to set your gains the way you're doing it. I don't care if you've done it 200 times and you're following JL's guide or not. It's wrong. It's incorrect. It will cause frustration like you're experiencing and/or potential issues with your system.

The best logical explanation I've seen posed on this forum was by Andy Wehmeyer. Start by searching his name and "gain setting" or "amplifier gains" or something. If that's not enough, keep searching as this has been discussed extensively.
 

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Discussion Starter · #11 ·
I'd search before coming here and asking "How do I set amplifier gains with a DMM?"

But that's not the case. I'm having a very specific issue and I believe it warranted it's own thread.

As for setting gains with a DMM being "wrong" and "incorrect", that's your opinion, and you are entitled to it I suppose, but I don't agree.

I'll be contacting JL today to see if they can offer any advice.
 

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As for setting gains with a DMM being "wrong" and "incorrect", that's your opinion, and you are entitled to it I suppose, but I don't agree.
Hmmm, how do I say this and not sound like an a-hole. No, what I told you was the truth.

This is not to say there's something wrong with your amps, there very well could be. What I'm saying is you are sort of blinded by your methods. Doing something over and over doesn't make it correct.

Here are your assumptions followed by the facts...

My processor has 4V output
With a 0 dB tone played with the HU volume at max, yes. Normally (say at 70% max HU volume) it's not even close. Amp gain "correctness" foiled due to inaccuracy of preout voltage. If you start wrong, you finish wrong. Get it?

My target voltage for each sub amp is 38.7V
How did you arrive at this number? You used a couple figures you're assuming will be constant during normal listening, right? Namely, speaker impedance and amplifier output. Fact is, neither of which are actually constant. Therefore, your "target" voltage is simply a shot in the dark based on inaccurate numbers. Again, start wrong = end wrong. Fact, not opinion.

the amp that powers the rear speakers and front tweets.......but here I am with it cranked
....causes....

Now I'm getting this hissing sound from up front, and it doesn't seem to change much whether the volume is on 2 or 25
....you're 100% correct. I can't think of really any situation that you need to add gain to pair of tweeters. Even with an amp that puts out 20 watts RMS. So, it would be safe to say that if you follow your "DMM gain setting method" you will shorten the lifespan of those tweeters considerably. Good thing you caught your error before they thermaled.

It's clear to me that all of my gain settings are out of whack.

I've gone through this whole process successfully with the only things changed being Slash amps instead of the HD amps. Same meter, same test tone CD. I have even gone through the process successfully with these HD amps a few months ago, with the only difference being the MX setting on the head unit.

I even used two separate mutimeters, thinking that one of them might be the problem. They both gave me identical readings.

My frustration level was boiling over, so I stepped away from the whole thing for the night.
Anyone have any ideas on what could be going on here? Anything to check for?
You got lucky with the Slash amps, basically. A flawed method yielded tolerable results which you figured was the "correct" way.

Use as many DMM's as you want, doesn't change the fact that the method is wrong.

Here's a quick and easy way to set your gains that will work every time that's based on all know factors: WHAT you are hearing. Your DMM cannot hear anything. Use a DMM to CONFIRM voltage or to MATCH voltage, but not to SET it.


1) all gains down
2) find your loudest, most dynamic song recorded to a CD (I wouldn't trust an Ipod or any lossy file, personally)
3) turn HU volume as high as it will go OR until the sound starts to break up, sound "thin" or distorted. Your tweeters will sound the loudest first, guaranteed.
4) if the mids and sub need more volume to match the tweeters, then slowly add gain until everything matches volume wise.
5) put some more songs in that you like and repeat the process. Maybe 3-4 more times. Not all songs are recorded at the same volume level. Some may seem 2-3 times as loud as others. So, you'll need to find a happy medium.

IF you want to use a DMM, NOW IS THE TIME. :)


Go through and check to see what the output voltage is on all the channels with your three tones. Write down those numbers. Then compare what the CORRECT gain settings are that you just found with your ears VS the WRONG gain settings were "supposed" to be with your method.

At the end of the day, this is how you unlearn "bad" info and relearn better, more effective ways at doing things. The final judge is always your ears. Always!
 

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Discussion Starter · #13 ·
Hmmm, how do I say this and not sound like an a-hole. No, what I told you was the truth.
LOL.

This is not to say there's something wrong with your amps, there very well could be.
It's certainly possible, but I don't think that's it.

What I'm saying is you are sort of blinded by your methods. Doing something over and over doesn't make it correct.
Instead of "correct" and "incorrect", why not just see our different methods as "my way" and "your way"? What makes "your way" the only way, and "my way" wrong? I don't think I'm the one being blinded here. I've set gains by ear before plenty of times. It's not my preferred method anymore.

Here are your assumptions followed by the facts...

With a 0 dB tone played with the HU volume at max, yes. Normally (say at 70% max HU volume) it's not even close. Amp gain "correctness" foiled due to inaccuracy of preout voltage. If you start wrong, you finish wrong. Get it?
I'm not setting my gains based on the rated voltage of the processor. I'm sorry if I was unclear and made it sound that way.

How did you arrive at this number?
JL manuals that came with my amps.

You used a couple figures you're assuming will be constant during normal listening, right?
No. Incorrect assumption.

Namely, speaker impedance and amplifier output. Fact is, neither of which are actually constant. Therefore, your "target" voltage is simply a shot in the dark based on inaccurate numbers. Again, start wrong = end wrong. Fact, not opinion.
You've gotten ahead of yourself.

....you're 100% correct. I can't think of really any situation that you need to add gain to pair of tweeters. Even with an amp that puts out 20 watts RMS.
This statement leads me to believe that you don't fully understand the purpose of a gain knob. It's to adjust input sensitivity. it's not a volume knob. you probably know this, but your statement about "adding gain" to an amp makes it seem otherwise.

So, it would be safe to say that if you follow your "DMM gain setting method" you will shorten the lifespan of those tweeters considerably. Good thing you caught your error before they thermaled.
I disagree.

You got lucky with the Slash amps, basically. A flawed method yielded tolerable results which you figured was the "correct" way.

Use as many DMM's as you want, doesn't change the fact that the method is wrong.

Here's a quick and easy way to set your gains that will work every time that's based on all know factors: WHAT you are hearing. Your DMM cannot hear anything. Use a DMM to CONFIRM voltage or to MATCH voltage, but not to SET it.


1) all gains down
2) find your loudest, most dynamic song recorded to a CD (I wouldn't trust an Ipod or any lossy file, personally)
3) turn HU volume as high as it will go OR until the sound starts to break up, sound "thin" or distorted. Your tweeters will sound the loudest first, guaranteed.
4) if the mids and sub need more volume to match the tweeters, then slowly add gain until everything matches volume wise.
5) put some more songs in that you like and repeat the process. Maybe 3-4 more times. Not all songs are recorded at the same volume level. Some may seem 2-3 times as loud as others. So, you'll need to find a happy medium.

IF you want to use a DMM, NOW IS THE TIME. :)


Go through and check to see what the output voltage is on all the channels with your three tones. Write down those numbers. Then compare what the CORRECT gain settings are that you just found with your ears VS the WRONG gain settings were "supposed" to be with your method.

At the end of the day, this is how you unlearn "bad" info and relearn better, more effective ways at doing things. The final judge is always your ears. Always!
Once again, I do not wish to set my gains by ear. If it works for you, great! But that doesn't mean your way is correct and my way is incorrect. I thanked you for your input the first time, but now it's clear that you want to push your way of doing things as the only way, and therefore your "advice" isn't helping me. I don't wish to argue with you anymore. Thanks.
 

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Once again, I do not wish to set my gains by ear. If it works for you, great! But that doesn't mean your way is correct and my way is incorrect. I thanked you for your input the first time, but now it's clear that you want to push your way of doing things as the only way, and therefore your "advice" isn't helping me. I don't wish to argue with you anymore. Thanks.
Ugggg...

Keep putting out grease fires with water.
Keep pissing in to the wind.

Keep telling yourself you know what you're doing...

That will work....

Solves all kinds of problems........

:rolleyes:
 

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Thanks for the input, but I'd rather not set it by ear.
Because the drivers all have the EXACT same sensitivities? because setting the amps so that they clip at the same point yields the best distribution of power to the drivers? Because your DMM will tell you when it sounds right? Because your DMM listens to the system and not you?

You have not thought this all the way thru, you are missing some very important chunks of this puzzle.
 

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Discussion Starter · #16 ·
Because the drivers all have the EXACT same sensitivities? because setting the amps so that they clip at the same point yields the best distribution of power to the drivers? Because your DMM will tell you when it sounds right? Because your DMM listens to the system and not you?

You have not thought this all the way thru, you are missing some very important chunks of this puzzle.

LOL.

Setting the gains is not where my system tuning ends. Not hardly. I can always back the gains off from there and adjust the levels and sound in depth with my processor.

What some of y'all fail to understand is that I have set gains by ear plenty of times before. I have chosen not to do it that way, and will be using a DMM and setting the gains per the manual.

You don't have to agree with that method. I didn't start this thread to be a debate on which way is best.
 

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TspenceII, ladies and gents.....I give you Tspence version 2.0.

"You don't have to agree with fantasy, but you have to respect my belief in it."

Genius.
 

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Discussion Starter · #18 ·
TspenceII, ladies and gents.....I give you Tspence version 2.0.

"You don't have to agree with fantasy, but you have to respect my belief in it."

Genius.
Your respect doesn't do anything for me.

Some of you seem very bitter and close minded. It's entertaining to see people who insist that their way is the only right way and that any other method is wrong. I've done it both ways. You've now taken this trhead and turned it into something it was not intended to be.

Oh well. There are people like that all over the internet. Carry on if you must!
 

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Discussion Starter · #19 ·
An unwillingness to debate is simply recognition that you are wrong, and have no way to defend your position.
It's senseless to argue with those who refuse to believe that there are any truths other than the ones that they believe in.
 

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Discussion Starter · #20 ·
I willing...

Convince me.

Tell me why your gain structure makes sense.
Ha! You've made it clear in your posts that you're not.

Sucks about your reading comprehension problems.

Feel free to start your own thread if you'd like to debate this issue.
 
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