**Amplifier Gain setting tutorial**

[jntar]

Most audio equipment dies for one simple reason. Most people push their equipment beyond its limits. Whether it is the amplifier, subwoofer or full range speakers, clipping is the number one cause of failure. To prevent clipping, use this tutorial.

To figure out what voltage you should set the gains to, multiply the RMS power of the amplifiers output by the impedance of the speaker, then find the square root of that number. If you are using an amplifier that has an RMS rating of more than your speaker(s) can handle/rated for, then use the RMS rating of the speaker (instead of the RMS of the amplifier) to determine the voltage to set your amp to. This is also referred to as gaining down.

Gain Setting Equation
Voltage of the output = sqrt(RMS Power X impedance of the speaker)

• Example
  Say the amp provides 100WRMS into a 4 ohm speaker:
  
  Voltage = sqrt(100W X 4 ohms)
  Voltage = sqrt(400W*ohms)
  Voltage = 20V
  
  Again, that was only an example, use the ratings of your amp to figure that out.

Setting the Gain(s)
To set the gain(s), you need two things:

• 1. A DMM (digital multi-meter) that is capable of measuring AC voltage (needs to be able to measure up to a range of 200V).
  2. A test tone CD to use to set the gains at the correct setting.

Now, to set the gain(s):

• 1. Start the vehicle, and pop the test tone CD in the head unit.
  2. DO NOT hook up the sub(s) or speaker(s) to the amplifier while doing this, just leave the outputs unused at this time.
  3.Now, time to set up the head unit.
  • a. If the loudest you listen to your music at on a regular basis is 22/35 with bass @ +3 and treble @ 0 with MX (or any other sound processor) on, use those settings. NEVER turn the headunit above 3/4 of the maximum volume.
    b. Remember to have the car turned on.
    c. If you want to use bass boost on a sub amp, set it prior to setting the gains on the amp and use the center frequency of the bass boost (45 Hz for most amps) as your test tone.
    d. Please remember that if you have a subwoofer volume control on the headunit, set it to full before you set the gains on the sub amp.
  3. Take the leads from the DMM and but them on the outputs from the amp.
  4. Set the gain so that the outputs of the amplifier equal the voltage you found above. This is a MUST.

Here is JL Audio tutorial on their site:
http://www.jlaudio.com/tutorials/Input_Sen...ensitivity.html

And here is 20-80Hz test tones:
http://www.ronelmm.com/tones/

For test tones higher than 80Hz, download this program and you can create your own:
Adobe Audition Trial Version

It is best to use 50 Hz tone for a sub amp (unless you have bass boost, use the frequency that is boosted as the tone), and a 1kHz tone for a full-range amp.

This is a good way to set the gains, but if you have access to an oscilloscope, by all means use it. Then you can set the gains to their absolute maximum as you can see when the amplifier clips.

If you are wondering what exactly clipping is, and what it looks like, read this:
http://www.bcae1.com/2ltlpwr.htm

If you have any questions about this, post up, I’ll try my best to answer them.

Also, remember a sub can only handle what it can, if you set the amp to its RMS you have to remember that the sub can handle only so much. It is box dependant, but it is best if you are not experienced to follow the manufacturers recommendations.

Enjoy, and remember to thump responsibly!

[ExtCaddy]

I'm going to go play with my truck a little later and try all this nifty stuff out.

I know my system is set up wrong, because I turned it up real high and it gets very distorted when I know it shouldn't.

Is it bad to turn a headunit to more than 75% of its volume control? Will this accelerate damage to my speakers? How?

I run a Pioneer 840MP with JL 500/1 powering 2 JL10W6AE's and 1 JL 300/4 powering Focal K2 6.5" fronts. The focal component set is SWEET.

I have an Extra cab truck (1997) with the third door option. I can only fit 4x6 speakers in my trucks factory openings. What should I do for my rear fill? Any opinions?

[jntar]

Originally Posted by ExtCaddy

I'm going to go play with my truck a little later and try all this nifty stuff out.

I know my system is set up wrong, because I turned it up real high and it gets very distorted when I know it shouldn't.

Cool...

Originally Posted by ExtCaddy

Is it bad to turn a headunit to more than 75% of its volume control? Will this accelerate damage to my speakers? How?

Most headunits internals(amps and preouts) clip above 75% volume. This is just a safty precaution for you speakers and subs. Yes it will cause damage to your speakers/amps if they are sent a clipped signal. Please read this for an explanation. http://www.bcae1.com/2ltlpwr.htm

Originally Posted by ExtCaddy

I run a Pioneer 840MP with JL 500/1 powering 2 JL10W6AE's and 1 JL 300/4 powering Focal K2 6.5" fronts. The focal component set is SWEET.

I have an Extra cab truck (1997) with the third door option. I can only fit 4x6 speakers in my trucks factory openings. What should I do for my rear fill? Any opinions?

I personally dont like rear fill. If your front stage is good enough you wont need it. Again check the link above for thoughts on rear fill.

[TITANIUM]

I use my ears. If it is distorted, something is turned up too much.

[1buda]

Cool write up, I'll have to read it again later.

[jntar]

Originally Posted by TITANIUM

I use my ears. If it is distorted, something is turned up too much.

You would be surprised how many people do that and then wonder why their subs, speakers, or amps crap out on them. I am not saying that it will happen to everybody, but it does happen often. All I will say is that I strongly advise you use the tutorial to set your gain so that you will have no problems in the future.

[x6369x]

Any tips for setting up a HU for SPL?

[ibthumpin]

quite honestly, all that is over most people's heads. The quick and dirty tactic of 75% deck volume and bring the gains up till audible distortion is detected gets the job done.

[jntar]

Originally Posted by ibthumpin

quite honestly, all that is over most people's heads. The quick and dirty tactic of 75% deck volume and bring the gains up till audible distortion is detected gets the job done.

Originally Posted by jntar

You would be surprised how many people do that and then wonder why their subs, speakers, or amps crap out on them. I am not saying that it will happen to everybody, but it does happen often. All I will say is that I strongly advise you use the tutorial to set your gain so that you will have no problems in the future.

10char

[jntar]

Originally Posted by x6369x

Any tips for setting up a HU for SPL?

Honestly in SPL the settings make very little difference. (Before you flame read the whole post)

If you set your head unit with a -6 bass then set your gain it should and will be the same as if you set your bass at +6 and set your gain. The only difference is that you will have to turn the gain up on the amp for the -6 to match the signal of the head unit.

The gain is not a volume knob. It simply is a tool for matching the output signal of the HU to the input of the amp.


I understand that some of you dont understand this. That is fine. Go to the JL Audio link. TRUST ME, I am not making this up, this is the CORRECT way to set your amplifiers gain. Do this and you wont have any problems, dont do this and you run the risk for failure.

-Justin


EDIT: (just though of more in the SPL subject)

When you go to an SPL show you see a good mix of folks.

You see the normal guy off the street that went to BB or CC and bought all their equipment from them. These guys usually dont do as well as they hope. Reason behind it, they have very limited knowledge in "making a vehicle loud" They think more speaker and amps is all it takes.

Next you see the guys will some experence, these guys usually win the local shows but never go any further.

The last people are the guys that live and breath to be loud. They get paid to do it. Most of them have LOTS of knowledge in math and physics. They use what they have learned to make vehicles that could actually kill you from the pressure.

I guess that that was a bunch of rambling...

Anyways my point was...

Its not one piece of the system that makes the score. Nate Munson has made one 10" woofer hit 160+ dbs. subs, amps, car, box design, impedance rise, etc...all these make an SPL vehicle.

[x6369x]

Originally Posted by jntar

Its not one piece of the system that makes the score. Nate Munson has made one 10" woofer hit 160+ dbs. subs, amps, car, box design, impedance rise, etc...all these make an SPL vehicle.

I understand that ... I only compete locally and just for the hell of it, but I've been in an out of the car audio industry since 1990, so I've been around my share of SPL systems.

I was just looking for any tips to possibly add another tenth or so.

[jntar]

Originally Posted by x6369x

I understand that ... I only compete locally and just for the hell of it, but I've been in an out of the car audio industry since 1990, so I've been around my share of SPL systems.

I was just looking for any tips to possibly add another tenth or so.

I am not real big into the SPL comps. I go to a few but having a reg cab truck hasnt helped me too much. I only have 1 trophy in my collection for SPL...I am more of an SQ guy.


Here is a few links to tips and tricks...
http://forums.caraudio.com/vb/showthread.php?t=63004
http://audioforum.termpro.com/cgi-bi...3;t=005383;p=0
http://forums.caraudio.com/vb/showth...light=SPL+tips

[TribalVision]

A strong front stage will always win the SQ show.. People always ask me what speakers I have in the back and they're shocked when I say "none".... I dont need any. My fronts are plenty strong to fill the cabin with sound. I could actuaslly use some more power, but we're good for now.

DOWN with rear fill..... unless its the family car..

[jntar]

Originally Posted by TribalVision

A strong front stage will always win the SQ show.. People always ask me what speakers I have in the back and they're shocked when I say "none".... I dont need any. My fronts are plenty strong to fill the cabin with sound. I could actuaslly use some more power, but we're good for now.

DOWN with rear fill..... unless its the family car..

I definatly agree 100%
Rear fill to me does nothing but throw off your imaging and phasing

[jntar]

Should this be a sticky?

[Stroker 1500]

This would work for setting the gain on components also right? What kind of test tone would you use for setting the amp that powers the components?

[Stroker 1500]

Also im trying to learn a little about this, i try and set it by ear but i haven't been in it long enough to get it perfect just by ear. What do you usually set the subsonic at? If you have 2 subs that are 500 RMS each and there both 2ohm dual voice coil and its wired to be a 2 ohm load at the amp (mono block) then you would use the equation of:
Sqrt(1000*2) so you would get a 44mv setting correct? Now lets say the amp is only 850 RMS @ 2 ohms so its a bit under the RMS of both subs would you be able to achieve the 44MV setting? How exactly would you set this? Do you have any advice on how the bass boost should be set?

EDIT.. I just re-read again and realized that you should only use the speakers to find the voltage if the rms of the amp is higher than the subs.. Still would like answers for the other questions though. (bass boost and subsonic)

[jntar]

Originally Posted by Stroker 1500

This would work for setting the gain on components also right? What kind of test tone would you use for setting the amp that powers the components?

Yes this will work for setting any amps gains. I use a 1khz or 1000hz test tone. The link in my first post has all the tones you will ever need.

[jntar]

Originally Posted by Stroker 1500

Also im trying to learn a little about this, i try and set it by ear but i haven't been in it long enough to get it perfect just by ear. What do you usually set the subsonic at? If you have 2 subs that are 500 RMS each and there both 2ohm dual voice coil and its wired to be a 2 ohm load at the amp (mono block) then you would use the equation of:
Sqrt(1000*2) so you would get a 44mv setting correct? Now lets say the amp is only 850 RMS @ 2 ohms so its a bit under the RMS of both subs would you be able to achieve the 44MV setting? How exactly would you set this? Do you have any advice on how the bass boost should be set?

EDIT.. I just re-read again and realized that you should only use the speakers to find the voltage if the rms of the amp is higher than the subs.. Still would like answers for the other questions though. (bass boost and subsonic)

Like you stated you use the amps to set the gain, or the speakers rms rating if the amps puts out a higher power.

I recommend that you dont use the bass boost. I dont like them, if you do feel free to use them. Set the bass boost to where you like it then set the gain. **do this at a lower setting so you dont risk destroying the speakers or amps**

Subsonic is box dependant.
If you have a sealed box that is in the manufacturers specs there is no need for the SS filter.
For a larger sealed box I usually set it to 20hz
for a ported box...set the sub sonic filter around 5-10db lower then the tuning of your box. The reason, if you play too low of a note in a ported box the sub will begin to unload and bottom out. This is REAL bad. My experience has let me to 10db below is the best setting for the installs that I have done.

[95Silverado]

What about a basslink? Would I set it up the same way? Also, how would I know the voltage of the gain(basslink doesn't have a display for it)?