amp gain question

well thats a touchy subject but heres my thoughts and more than likely some others an some maybe not.....

some think that they just blew the sub due to lack of power....but they have there gains maxed which is going to clip the signal which will distroy a speaker....so what I am trying to say is that if you back off on the gains on your amp then you should be just fine....rather if your amp was too small...and you wanted to compensate for it so you turn the gains all the way up....

thats my take on under powering

The input gain control on an amp will not limit the power it can produce.  An amp is designed to produce full rated power with the input gain control in any position.  So no, setting the gain lower will not limit its power output.  The gain control is designed to match the input sensitivity to the output voltage being supplied to it.  This is neceaasry in car audio because there is no industry standard voltage for line-level signals.  Have you ever seen an input gain on home amps?  No, because there is an industry standard for home equipment.

The gain control is used to match the amplifier's output curve to the source units input.  Set lower = higher voltage input.  NOW, if the input remains the same, then adjusting the input gain SEEMS to act like a volume control.  What you are doing is adjusting the amplifier to think the input voltage is something it is not.  The  common misconception is you have somehow limited (or boosted) the amps power output.  No, you have adjusted its performance curve at that one inpoint point to be something other than what it is supposed to be.  Set the gain too high and then when you turn up the head unit, the amp will clip.  Set it too low and you lose the ability to listen at low volume levels.  But the amp will still produce 100% of its rated output.

Oh, and I've said it before and I'll probably say it a hundred times more: underpower CANNOT harm a loudspeaker if the amp is set up properly.  OVERpower and clipping harms loudspeakers.  It's called physics.

Now, if you install a nice big SPL system and your bass is too much to use on a daily basis, the only thing you can do is change your system, lower the overall volume, or cut the bass using an EQ or the tone controls in your head (or some other processing device.)  This is a common result with people who install big amps and big subs: it sounds like a cool thing to do and it looks great, but you can't really listen to it.  Indeed, most people who compete seriously would never use their 150db competition car for daily driving and daily listening.  They'd go deaf.  One trick I've seen is to cut the signal going to all but one driver in a multiple sub system for normal listening and only "turn on" the rest of the system for competition or showing off.  I also know people with multiple amp setups: a conservative 100 or 200 watt amp for daily listening and a 1500 watt monster for competition.  They switch the big fella on maybe once or twice a month.

Dyohn can you input on your thoughts of underpowering a sub

You can underpower a sub all day long and cause no problems to a subwoofer. The RMS power handling of a sub is a guide at best, it is the thermal barrier that the sub can safely transfer the input power into heat and sound. Heat is what is going to cause a sub to fail, it is a natural byproduct of producing power in any way shape or form. (had a cider or two here, so don't mind if I ramble on - nice day outside - the snowchickens aerobatic team is praticing here this week - had the time to sit and enjoy). Anyways the peak power rating of a sub is what the speaker can dissipate as a snapshot in time. It can respond to that level of input for that brief moment in time but if left continously playing that signal, the speaker will not be able to dissipate the excess heat build up and you end up with the dreaded sss (smelly speaker syndrome). If you run less than the rms rating of a sub into the amp and do not run the amp into clipping, the sub will play and last a long time. What may happen is that your spl may not be what you expect (which leads to improper gain setting), the bass will lack impact and definition beacuse of not enough power, but it will not blow if the gain is set correctly and the sub does not see a clipped signal. A sub may actually play a clipped signal and never fail, depending on the length of time that it is playing the signal, the type of voice coil former used, the type of box, the type of cooling system in the sub in question. All these factor into the if or when the sub will fail due to clipping. Once a sub is damaged due to clipping, it is only a matter of time before it fails. If you drastically overpower a sub and the voice coil former cannot dissipate the excessive heat generated, it too can cause failure of the sub.

Your vehicle has a speedometer that says it can do 260 kmh. It does not mean that you must do that speed all the time. You car has a tachometer, the redline is at 7000 rmp. You know that if you exceed that redline bad things can happen to the engine, but if you stay below it all is fine. The clipping point of an amp is the redline on a tach. It is partially determined by the input voltage of the amplifer coming from whatever source (cd player or processor). It is also determined by the amount of boost or cut in the frequencies that the amp is playing as well as the source material itslef. A gain control is not a volume control, it is a level matching device to the output voltage of the source unit that is supplying the input signal. It is designed to be turned down, not up. A sub has a happy range of power that it can handle safely, the rms power rating is a good guide to follow for general everyday use for the person who wants to listen to his / her music. Underpowering the sub again is fine, it will play all day long, the trick is to have the gain set properly and prevent the clipping which cause the dreaded sss.

   YOu guys R the greatest, loved the sss, and the tack compairson

thanks again....for the knowledge....

Thank you, haemphyst.  It's always good to get some of the actual technical details described.  I try to not get into the engineering side too heavily on here, since this forum is aimed at average users and installers, but your desciption is 100% right on and very germain to this discussion!

The bottom line is: you can use pretty much whatever equipment in whatever combination you choose so long as you know what yo are doing and have it set up correctly.  Overpower and underpower are both things that tend to plague the novice or people who don't really understand that audio is produced by electricity and that there are many physical phenomenon involved beyond brand names and the idiodic consumer demand to "make it loud."

By the way, how do those Morel's sound in a car?  I've used those drivers in home theatre center channels before, but not in a car...

DYohn] wrote:

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Thank you, haemphyst.  It's always good to get some of the actual technical details described.  I try to not get into the engineering side too heavily on here, since this forum is aimed at average users and installers, but your desciption is 100% right on and very germain to this discussion!

The bottom line is: you can use pretty much whatever equipment in whatever combination you choose so long as you know what yo are doing and have it set up correctly.  Overpower and underpower are both things that tend to plague the novice or people who don't really understand that audio is produced by electricity and that there are many physical phenomenon involved beyond brand names and the idiodic consumer demand to "make it loud."

By the way, how do those Morel's sound in a car?  I've used those drivers in home theatre center channels before, but not in a car...

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