amp gain question

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...