FP: When i took those readings, i was running a pair of highly modified 4 ohm AR 9's
. These are four way, five driver 150 lb tower with dual 12" woofers, an 8" mid-woofer, a 1.5" upper midrange and a .75" tweeter per cabinet. Since all of the drivers are bandwidth limited due to being a four way design, and there are two "beefy" woofers sharing the load for the extreme bottom end, and the lower mids are fed into an 8" driver, and the dome mid has a sharp crossover slope, and the tweeter is crossed over quite high ( 7 KHz )none of the individual drivers are really stressed, nor do they see nearly as much power on an average basis that most other designs would. As such, they can play phenomenally loud while still retaining their composure. If these speakers were produced today, they would easily retail for well over $10K.
I used to drive these with a Perreaux PMF 2150 ( 200 / 400 wpc ) running the top end and a Perreaux PMF 3150 ( 300 / 500 wpc ) running the bottom end. I was running into amplifier saturation though, so i ended up moving to two PMF 3150's, which was better but still not enough power. I am currently driving these speakers with a Sunfire Signature, which i had shut down due to thermal stress as previously mentioned. I've not had any problems with the amp shutting down now after several modifications were performed. In case you're wondering, we pulled the current limiters out of the circuit, raised the temperature that thermal shut-off occurs at, increased the power supply reserve capacity, changed caps in the feedback network, etc.. This amp now clips at 1480 wpc @ 4 ohms, which is the nominal impedance of the AR 9's. The 3150's used to pound on the Sunfire in terms of bass impact prior to the modifications being done, but now it is so close that i don't know if there is a difference anymore. The two 3150's are now running multiple subwoofers in another system that i have set up.
As a side note, the recent article in Stereophile about loudspeaker dispersion, frequency response and and baffle diffraction mentions the fact that the most prominent work done in loudspeaker research and design in the last 50 years was done by AR. For the record, their findings were published in 1978. All of their findings when performing that research went into the technology used to make the AR 9's, which were released in late 1978 / early 79.
While many people don't realize it, this speaker and the associated research has been extremely influential in the design of other speakers since that time. While many people don't realize it, AR was the company that "invented" Acoustic Suspension ( sealed & stuffed ) designs. They also were the ones responsible for the invention of "domed" drivers. They were also the first to utilize side-firing woofers, which was done for multiple reasons. One should make note that their woofers were mounted very close to the floor though, as this is the only side-firing approach that makes sense acoustically. They were also the first to use acoustic damping material on the baffle to minimize diffraction i.e. AR's famous "Acoustic Blanket". Technically speaking though, Dunlavy holds the patent on this even though AR was the first on the market with such designs. Evidently, Dunlavy's patent and AR's products crossed paths at the same appr time.
How many other speakers that you are familiar with utilize design aspects or technology that AR brought with them to the table in this model??? Quite honestly, i can spout off dozens with one brand in particular coming to mind.
With minds like Edgar Villchur ( owner and founder of AR ), Henry Kloss ( partial owner and one of the original founder's of AR along with KLH and Advent ), Roy Allison ( who later went on to found Allison Acoustics and did tons of studies regarding the loudspeaker / room interphase ), Ken Kantor ( who went onto work with NHT and is currently doing work under the name of Intelligent Audio Systems ), etc... you can see how this type of product came to be. As yet another side note, the NHT 1259, which is considered to be the most widely used woofer in DIY subwoofer designs, is quite similar in electrical characteristics to the original AR 12's. So much for "modern technology" advancing by leaps and bounds.
I've also got a set of AR 90's set up in the same system. These can be seen at the link above and have received the same modifications that i've performed to the 9's. They are nearly identical to the 9's with the only differences being the fact that they use dual 10's instead of 12's and have a slightly smaller cabinet. Both are low Q sealed and stuffed 4 ohm designs. These are fed from a modified Sunfire Cinema Grand Signature with a "measly" 800 wpc. For sake of clarity, i was only running the 9's when i took those readings.
Other than that, i also have a pair of highly modified LaScala's. These are rated at 104 dB's, but quite honestly, would blow up LONG before the AR's would in terms of power handling. Then again, the Klipsch are FAR, FAR more efficient, so you don't need to throttle them near as hard to achieve similiar output levels. The LaScala's are factory rated at a peak SPL level of 128 dB's in stock form using the "standard" Klipsch woofers. I've got their "Pro" series woofers in this specific set of LaScala's, which is good for measurably more bass and higher power handling. The most i've ever dumped into the LaScala's was a few hundred watts and that specific amp was clipping quite noticeably on peaks at that point. Needless to say, it didn't sound all that hot, but it sure was LOUD : )
As far as measuring acoustic output goes, i use a Bruel & Kjaer system. Anybody that is familiar with lab grade test equipment will be familiar with this name and their spl meters. I've also got stock and highly modified RS spl meters for sake of comparisons with other people's RS meters.
Hope this answers some of your questions. Sean