Gain formula?

Right, to even the balance, err on the side of caution.

Thanks for your help....I can just buy a multimeter at Radio Shack, right? Or is one brand better than another?

DMM=digital multimeter.  I have one from Sears hardware, about $25 to $40.  Radio Shack should have a good selection, too.  These are not true RMS meters, which cost considerably more, but will get the job done and provide you a valuable tool for the toolbox.

OK, I'll give in... yep, everything everybody has said above is correct. I will continue to stand by my previous suggestion, and never blow a speaker. If you are overpowering you speakers (meaning, running a higher powered amplifier than the speaker is rated for) you ARE going to blow your speakers if you insist on setting the gains to "the RMS output voltage of the amplifer". If you do this, number one you will already be running beyond the speakers rating, but then, while the speaker is distorting due to overpowering, you are never going to hear the additional distortion of the amplifer clipping, if it gets that far... and we all know what this does to a speaker. The clipping, in addition to overpowering your speaker to start with, will leave you with the question of WHEN, not IF... Also, even IF you buy an amplifer with the power exactly matched to the driver you will be connecting to it, and you are going to be amplifying your, say Diamond Components with one amp, AND your Eclipse 87000 series subwoofer with another amp, the efficiencies of these speakers will NOT be matched, the components will be louder... so as you turn up your volume, the gain curves will not be linear, the subwoofer amp will have to be a faster gain slope to reach RMS output at the same time the components do. Now, the sub amp will be putting out more power, even though it *IS* RMS power, the components are still likely to be louder, necessitating the user to "turn up the bass", or whatever - driving the sub amp into clipping, again, increasing the chance of early woofer failure. If you think about all of the points raised above, I think you will see I am right, and in a multi-amped system, the DMM method is TRULY a waste of time, and NOT the correct way to do it. Personally, I use an oscilloscope to discover the clipping point of the headunit, set the gain of the amplifier for the LEAST efficient speaker in the system, running the amp to JUST where the driver starts to complain at the resonant frequency of that driver, then I use an RTA to set the gains on the remaining drivers in the system. I also am a fan of overpowering a system, often running an amplifier rated for at LEAST twice the rated RMS power of the driver. Your RMS output voltage will change once you drop a speaker on the terminals. I do it this way, because a speaker is a highly reactive device, and you use the resonant frequency of the driver under test because this is where maximum mechanical motion occurs, with minimum power input. (I also tri-amp my existing system, AND soon will be quad-amping it... The DMM method would ABSOLUTELY GUARANTEE a blown driver...) But you guys go ahead and do it the way you want... I don't know what I'm talking about... While the DMM method is probably pretty safe, I still feel the ear is a far more sensitive measuring device, and will also give you FAR better warning as to when the amplifier or the speaker is driven to far.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

I can't take the credit for that formula. I guy at www.sounddomain.com came up with it.. I used this formula and know my subs and full range sound so much better..

... which is why I always recomend using loudspeakers rated for 2X to 3X the RMS power of the intended amplifier.  We call that a safety margin.  Matching levels by ear as haemphyst sugegsts is far preferable to simply setting up all amps to produce their maximum power levels and rolling (unless you have an RTA at your disposal or unless you have mathematically pre-matched all speakers and power ratings to create the proper blend before you even began the install.)Support the12volt.com

"... which is why I always recomend using loudspeakers rated for 2X to 3X the RMS power of the intended amplifier. We call that a safety margin. " That does not really matter though. If the amplifier starts clipping, I can Guarantee you that you will blow most drivers.

Poormanq45 wrote: "... which is why I always recomend using loudspeakers rated for 2X to 3X the RMS power of the intended amplifier. We call that a safety margin. " That does not really matter though. If the amplifier starts clipping, I can Guarantee you that you will blow most drivers.

Amplifier clipping has more to do with the installer and the system setup than anything else (except maybe very poorly made amplifiers)... but if the thermal rating of the loudspeaker voice coil is at least 2X the rated amplifier RMS output, there is no way the amp can "blow" the speaker.  A 100% clipped output (AKA square wave) is 1.414 times the voltage of the full clean RMS output, or approximately 2X the same power.  So, if your loudspeaker is rated for 200 watts and your amp is rated for 100 watts and you bone-headedly overdrive the amp into 100% clipping, the loudspeaker will be driven near its limits and will get hot and will make non-musical noises, but it will not blow.

Now to contradict myself, you could "blow" a poorly made speaker by driving it past its mechanical limits at its max power rating... but that's more a problem with some designs than a clipping issue. 

The most dangerous situation is using an amp with the exact power rating of a loudspeaker (and thinking you are safe) and then not being able to recognize and prevent clipping.  THEN you can toast a loudspeaker pretty quickly.  Of course using an over-powered amp can also destroy a loudspeaker with no clipping at all, but people who intentionally set up systems like this GENERALLY know what they are doing and don't overdrive them.

Support the12volt.com

I agree with DYohn here. There's a nice article about this explaining why on www.bcae1.com. It is titled, "Too Little Power." Poormanq and others, check it out if you're interested. I also agree 100% w/ haemphyst's gain setting method. Lizard, what are you doing listening to people at sounddomain for? ;-)New Project: 2003 Pathfinder

haemphyst wrote: OK, I'll give in...

Now that'll be the day!   lol   Before I move to strike my testimony from the record, I will state that there are some basic presumptions involved.  Anybody who is so inclined to set his system up accurately (and we know that not everybody is) is presumed to also have first made sure that he isn't setting up a 600 watt amplifier for a 300 watt speaker!  So let's give our setup guy this benefit of the doubt...

...that a lot of people can't tell by ear what they can see on a meter.  Lack of time and experience, if you will...

...and if we also presume that a setup by this RMS voltage output would result in the highest amount of voltage allowed, not a level that can be increased but only decreased if or when clipping or distortion is later detected by ear (as I mentioned earlier...)

.....then if that much can't be allowed in this court, then I reckon I have spent about 14 hours over the past 10 months posting this same information on this forum and nobody told me to quit!

There, that makes me all better.   lol