Midrange bloom

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Midrange bloom
Comparing the sound of two full-range loudspeakers systems can only get you so far. You can tell they are different but unless those differences are narrowed to only a few areas it's nigh impossible to know what to change. Such was the problem of the PS Audio AN3 AMT tweeter and midrange duo compared to our reference Arnie Nudell pair. Once the two measured close together we fired them up with a variety of music but it didn't take long to get overwhelmed by the differences. The AN3's DSP based servo system is so strikingly better than the older Genesis Technologies leftovers, or even the Infinity IRSV servo system, that we had trouble focusing on the target midrange/tweeter combo. It didn't take too long before we used the Learning Funnel to narrow the problem down. Turning off the AN3's active midbass and servo woofer sections to compare just the two made life a lot simpler though it took some adjusting. Because the tweeter/midrange section only go down to 500Hz there's a lot of music's essential frequencies missing—like listening to a tiny 2" speaker on an old transistor radio. Yet, even with the lower frequencies turned off the differences were easy enough to hear. Arnie's reference speakers had a lower midrange bloom we weren't hearing in the AN3. We looked closer at the measurements but were still befuddled as to the cause. Both systems had 2-pole high-pass filters at the bottom of the midrange ribbons and both measured reasonably close. Yet, there was that lower midrange bloom the AN3 lacked. Then, as if a light bulb flicked on, the answer was staring us right in the face. I can't remember if it was engineer Darren Meyers or Bob Stadtherr that first saw what should have been obvious. The Nudell reference used a long Bolender Graebener ribbon with nearly twice the length of the AN3s folded ribbon. Bingo. That larger area of coverage provided an increased level of energy at lower frequencies in the room in the same way an array of tweeters cumulatively go lower than a single tweeter can. The fix was easy though it meant the measured curves were no longer the same. Now the AMT's advantage of greater dynamics and its effortless means of squeezing air as an accordion does became apparent. In hindsight, I suppose we could have figured this out with measurements alone but that's just not the way it works best. Our ears are still the best measuring tools we have.
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Paul McGowan

Founder & CEO

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