amp and speaker compatibility

I've looked online into this issue and I've seen two opinions regarding amp and speaker "continuous average power(CAP)" (commonly, but incorrectly called RMS): ~It's better to overpower than to underpower ~You must match the CAP of the amp and the speakers (closer is better) I'm not sure of what to believe, so I come to 12Volt with this question: Will this be a PROPER amp and speaker buy? Cadence F100 5-channel amp with: ~100x4 @4ohms + 300 ~125x4 @2 ohms + 500 [will be powering] (4x) MTX TN653s ~rated at 45 CAP. (1x) Stock 8" Sub ~rated at ? CAP Will there be damage to the speakers on normal function? Is this too much CAP for the speakers?'97 Lexus ES300

(Expertise Level: Recently gotten into working with cars)

You can use any amp with any speaker as long as you know what you're doing.  In general it is better to buy more power than you will need.  The max continuous rating of the speaker should NOT be your target, but it gives you an idea of when the speaker will fail.  Just set your amp up properly with properly set gain and don't over-drive the speaker and you'll be fine.Support the12volt.com

To clarify, it is advised to buy more power than needed, set the gains properly, and enjoy? If so, excellent. Thanks for your help.'97 Lexus ES300

(Expertise Level: Recently gotten into working with cars)

Funny that many say that speakers should have a power handling GREATER than that of the amp. I once did too based on NOT blowing the speaker by overpowering. However, IMO the reality is as DY stated - set gains etc. And IMO even if there are no gains as in HUs etc, then I'd rather the amp be the source of distortion rather than the speakers. I don't recall hearing of CAP for audio outputs. However now I have seen & googled it, and I agree CAP is NOT the same as RMS. Of googling interest was this... "In 1974 the Federal Trade Commission (FTC) required that audio power and distortion ratings for home entertainment equipment be measured with power stated in RMS. [Amplifier Rule CFR 16 Part 432 (39 FR 15387)]."

oldspark wrote: Funny that many say that speakers should have a power handling GREATER than that of the amp. I once did too based on NOT blowing the speaker by overpowering. However, IMO the reality is as DY stated - set gains etc. And IMO even if there are no gains as in HUs etc, then I'd rather the amp be the source of distortion rather than the speakers. I don't recall hearing of CAP for audio outputs. However now I have seen & googled it, and I agree CAP is NOT the same as RMS.

So you agree that more CAP in the amp is better/allowable as long as the gains are set properly? I made up "CAP" after seeing someone mentioning how RMS is not the correct term. I just thought I would use the correct terminology. :)'97 Lexus ES300

(Expertise Level: Recently gotten into working with cars)

Well, more RMS... I like the "CAP" abbreviation because I can now say consistently that I don't like caps - whether capacitors, or CAPs, or upper-case letters in audio replies, or unexpected bangs behind me whilst working (LOL). To me RMS is the correct parameter since overloading is generally related to heat which is an RMS parameter. Things like overload punch-through and similar failures usually relate to peaks which neither RMS nor CAP relate to (in typical waveforms). As I understand it - and may DYohn & Haemo & the other gurus correct me - an oversized amp could blow undersized speakers, but with properly set gains, the max output is limited hence NOT overpowering the speakers.

oldspark wrote: To me RMS is the correct parameter since overloading is generally related to heat which is an RMS parameter. Things like overload punch-through and similar failures usually relate to peaks which neither RMS nor CAP relate to (in typical waveforms). As I understand it - and may DYohn & Haemo & the other gurus correct me - an oversized amp could blow undersized speakers, but with properly set gains, the max output is limited hence NOT overpowering the speakers.

RMS does not apply to power; there is no such thing as "RMS Wattage" or "RMS Horsepower."   RMS is a means for measuring voltage.  In amplifiers, the correct term is "Continuous" power, and it is determined from the RMS voltage output of the amplifier.

I agree with your second statement.

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RMS does apply to power (Watts). Interesting though that average Power is defined as Vrms x Irms, whereas for RMS Power, it is the the RMS of V x I where the only "real power" is for matched frequencies. (eg, V @ f1 x I @ f2 = 0 Watts when F1 is not equal to f2) To me, the reality is RMS power - eg, the heat in a resistor etc.

oldspark wrote: RMS does apply to power (Watts). Interesting though that average Power is defined as Vrms x Irms, whereas for RMS Power, it is the the RMS of V x I where the only "real power" is for matched frequencies. (eg, V @ f1 x I @ f2 = 0 Watts when F1 is not equal to f2) To me, the reality is RMS power - eg, the heat in a resistor etc.

Well, maybe it is a recognized engineering term Down Under, but here in America "RMS Power" as applied to audio amplifiers is a misuse of the term.

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No - you have the same definition of RMS power. RMS is not CAP - that CAP Wattage will be larger for speakers than their RMS. Whether you use CAP instead of RMS (despite the apparent FCC "ruling") is whatever it is. Now, is the actual audio "power" from speakers from their resistance, or inductance, or both?