Which mean it averge puts out that many watts

"Root mean square (rms) is, literally, the square root of the mean of the square of a value. It is a process for calculating an average value for a fluctuating value (such as ac voltage or current.) The term rms power is referred to as the average power. A power amplifier rated as having "200 watts rms power" really puts out 200 watts of continuous sine wave power."

http://www.jbl.com/car/featured/sponsors/h..._JBL_REVIEW.pdf

 

yeah, and the formula for calculating RMS is the .707 of a sine wave. which is 100% efficiency in translation of AC -> DC.

because RMS is the "working voltage"

 

Then calculate for the subs to not just the amp.
The point is putting that amp on that sub will never blow it. This it what the discussion is about.

 

you have to calculate for both. above amp RMS you cause 'clipping' of the signal and it becomes more of a square wave instead of a sine wave. This happens if input gain is too high or output impedance is too low.

If input gain is too low you don't get the maximum potential out of your speaker
If output impedance is too high you cause overheating of internal amp components
if output impedance is too low you get too much wattage going through the speaker
above speaker RMS you cause over heating and premature wear.
Below speaker RMS nothing happens


The only good combination is clipless gain, perfect impedance matching, and runnning RMS lower then or at speaker's potential.

 

From alpines web site
MRD-M605 V12 digital mono power amplifier SWR-1242D Type-R 12� subwoofer

There are those who like bass, and those who truly love bass. Love it? Then the SWR-1242 and MRD-M605 combo is the one to keep an ear out for. Featuring one of America's best selling subwoofers, the SWR-1242D, is designed to deliver deep, accurate bass. Pair it up with the MRD-M605, a V-12 Class-D amp, which delivers huge dollar per watt power. Now you're talking big bass!

hmm that amp is 100 watts rms more then that sub is rated for yet the recommend tem together.
dude you do not have to perfectly match rms power in amp speakers and subs. How many systems have you been able to this with yourself personally. Wait how many have you installed yourself ever?

 

i am going to have to agree with shorty if you put an amp that over powers your sub then you are much less likely to blow that biatch. by doing this you can max the sub out without pushing the amp to a level where you will run into distortion and the probability of blowing it. talk to anyone who has done stereo systems for years and is winning competitions. they will tell you to put an amp on that has the capability to over power speaker. pull out all this rms sine wave bull shit you like you are not impressing half of us. i was simply asking folks who have more car audio experience than myself i could car less about what you know how electronics work. i know enough about electronics.

 

I've installed around 10 systems.
I'm an electronics tech. I work on amplifiers and coils all the time. I'll tell you FOR SURE that if you run with higher amp RMS then speaker RMS you're not going to last as long as a system that is running matched.

I cannot find specs on that amplifer:

A class D amplifier is a phase shifted square wave run through a coil. The characteristics of a Class D amplifier change quite a bit because of it's unique amplification method. can you find one that is class AB?

If the manufacturer says go for it, then go for it. They know their systems.

 

Why would you want clas AB class D is better

 

i'm suggesting that maybe the rating was taken in a different method because it's class D. Class AB is the standard amplifier used for any application. because of the phase shifting methods used in Class D, it's output RMS even with a sine wave is unpredictable. This is also why a Class D cannot be used for higher frequencies

 

Ditto ABQ elantra fing02.gif


Above debate:
The thing is, you can crunch numbers and theories all day long until your hearts content, but real world experiance and techs will say the same thing. All you have to do is think about car audio 10 years ago. Who was winning competitions??? Folks who had fosgate amps that said they where running 200 watts on their registation sheets but had the mothas bridged so low you would say it was damn near impossible (some down to 1/2 OHM load!) powering speakers that where made to handle only 1/3 of the power!

Guns don't kill people, stupid mother f*****'s with guns kill people!

Amps dont kill subs, stupid mother f*****'s with amps kill subs!

You would be correct in saying that an amp cabable of putting out 1000 watts RMS cranked to a speaker that is only capable of 500 Watts RMS will most likely blow the speaker. But you miss one important point. You are also going to blow the amp!!!! The whole point of using a larger amp is not to send all that power to your speakers, but to create the most EFFICIENT environment for your sound system AND subs. That means a good box for your subs and providing enough power to reach their potential without stressing the amp that could lead to distortion.

ENOUGH SAID! Back on topic.

ABQelantra: shortyg83 has a great point about that amp. You should really think about how you are going to wire that L7 and consider if that amp is the best solution. It might be. Just double check to make sure it will run at the load you are aiming for. If you are aiming for running that L7 at 1 OHM, make sure that the amp you purchase will be capable of running subs at a 1 OHM load bridged. OR...get a mono block amp that is stable to 1 OHM. OR........get a L7 that is dual 4 OHM like he said. That way you can run at a 2 OHM load. Remember, the lower impedence you run will generally be louder and give more bass, but, it also requires more power and that the amplifier be stable enough to handle such a load. Most people running for spl try to get as close to the 1 or 1/2 OHM load as possible since it sucks as much juice out of the amp as possible.

And...

If you plan on doing a vented enclosure for that L7, do your homework. Trek down to the library or go to your local book store and pick up a book about speaker building. Vented and ported enclosures are MUCH more difficult to build than a sealed box. The ports have to be the correct size, the correct distance away from the speaker, and the correct depth. They also have to be tuned to a certain frequency. And all of this is figured on you having a nice square box. If you are going to have any kind of shaped box, then you are really taking your chances. I know I was going to make a vented encloser for my Type R's, but after learing how to make one of any quality, I quickly re-designed my plans. Just would'nt want you to go through all the work of making your own custom enclosures and then have the possibility of you being disappointed. With a sealed encloser, you really cant go wrong.