Phasing irregularities often causes problems of apparent "short throw" at low frequencies. Something as simple as the subs not sitting on the same horizontal plane or aiming in slightly different directions can result in phase-related losses of several dB. Of course if the subs have reverse polarity - i.e. they are 180 degrees out of phase due to messed up wiring - the losses are even higher. The trouble is, when you listen closely to a speaker which is out of phase with other similar speakers, whether acoustically or electrically, it sounds perfectly fine - lots of power and punch. The losses occur at a distance where those long, out-of-phase waves come together and cancel each other out. If you think this could be a problem, check everything out with an electrical phase tester for the subs' wiring and cables. Finally, make sure the subs are geographically aligned and close-coupled. You might not need new subs at all.
When it comes to speakers, the original test method involved connecting the test amp to the output of a test oscillator set at 1,000 Hz sine wave. You would turn the amp up 'til a connected voltmeter read X-number of volts hence watts per the formula and wait for the speaker to "peeeeeep" itself to death (or not).This might happen in fairly short order with some speakers but oddly not with others which seemed outwardly similar - same voicecoil, same magnet. Why? It had to be the cone - the surviving speaker had vibrated more freely at that frequency hence the voice coil moved farther and was able to keep itself cool enough to survive. Ergo, power capacity had to be effected by frequency response.
The audio industry responded to this quandary by developing the "sweep" oscillator test method. Here the frequency of the sine wave could automatically be swept from 20Hz to 20kHz repeatedly and at an adjustable rate. That meant the speaker was subjected to a single "boooeeeeeeep" time after time until it failed (or not). The trouble was, if you did this slowly, the speaker might fail at 100 watts. But if you set the sweep rate fast enough - "bweepbweepbweep" - that same speaker could take maybe 150 watts (!). And of course nobody in the industry could come up with a "standard" sweep rate (an impossible task). So there it sat. A big unsolved problem. People had to have a power rating but RMS wasn't very reliable.
Things came to a head in the 1970s when concert sound burst on the scene. Suddenly everyone was declaring themselves "sound men" and putting big systems together. Now it became important to know how much power a driver could take when music was the source. But all they had were the old RMS ratings. Thus followed a dreadful period wherein drivers were blowing like popcorn while soundmen threw around theories like "Apply twice the RMS rating." or "Apply three times RMS." or whatever.
Pink noise had been developed in the sixties but wasn't widely used in this application until the 1980s. It is the closest you can come to music, in terms of making a driver work. Pink noise is one of the sources manufacturers use these days in establishing "program" power ratings. We do too, but we also use highly compressed rock CDs to represent worst-case live audio conditions.
Anyway, that's why we don't have RMS ratings for speakers any more. But fear not, amps are a different matter. RMS can be used to closely represent the continuous or long-term average output of an amp. Ergo, if you have a 100Wrms amp, you can, with due caution, use a 100W continuous program speaker - a masterpiece of simplicity compared to the old days. Continuous program is how all our speakers are rated.
