Quintet15… Bi-Amping… From Horn1 to Voxativ AC-X

My journey to the sonic ideal was at times pleasurable, but for the most part, frustrating. I had wanted to pursue the active bi-amping + open baffle route after the late great Peter Aczel touted the combination’s superiority over box speakers (or “monkey coffins” as Peter liked to call them) and passive crossovers. Peter Aczel was good friends with Siegfried Linkwitz (also RIP) and his Orion speakers, as well as the subsequent incarnation of his humble genius, the LX521. These were open-baffle, dipole designs, driven by multiple amplifiers through an active crossover. Linkwitz would show up at many audio expositions with the Orion/LX521, powered by budget amplifiers like ATI or Emotiva, and their room would draw accolades from even the most hard-nosed critics in the business. As chief editor of the (now defunct) Audio Critic magazine, Aczel was convinced that open-baffle was, and always would be, better at producing a realistic sound picture, and he at one point announced that he was finished reviewing box speakers, save for very few models such as those from Legacy Audio.

I don’t know if Peter Aczel was familiar with Pure Audio Project (he died in 2017), but I believe he would have championed their design approach and aesthetic. I also believe he would have happily included Ze’ev Schlik in The Audio Critic’s vaunted “White Hat” category of audio personalities.

At one point, I had planned to purchase and assemble a pair of LX521’s from the Linkwitz store, but they were a bit pricey, so I searched the ‘net for an alternative. I was satisfied with my current PSB Stratus Gold i’s, though I could not shake the impression that something was missing; I knew my system could be improved. I then discovered Pure Audio Project and went the PAP route because I wanted to go big. Real big. Though my listening space is currently medium-sized at best, I wanted to plan for the future, so I went with the Quintet15Horn1 model. While waiting on delivery, I ordered an active crossover from Marchand Electronics. Why I did not go with PAP’s Nelson Pass C-1 active crossover, I’m not entirely certain, but it probably had something to do with cost. It was a decision I would later lament, and you’ll soon see why.

Parts began to arrive and I eagerly assembled the Quintets. I thought the horn driver was beautiful, and I was getting excited. At last they were complete. I began listening. I’m going to be honest here: I was not blown away. In fact, I was disappointed. The horns were bright and shouty, but I knew I could tame them with some judicious tweaking of the crossover. While the eight woofers were being powered by two massive Emotiva monoblocks, the horns were driven by a Schiit Aegir (Class-A…ish) at 25wpc. But making changes via the crossover was an exercise in futility; nothing seemed to improve the sound. I was assured by Ze’ev and other PAP owners that the horns (and woofers to a lesser degree) needed not less than 150-200 hours of break-in time, so I let music play as often as was feasible. Soon the horns began to relax and the previously absent lower midrange started to emerge a little, but something else was happening. As the horns slowly opened up, I made corresponding adjustments to the crossover, and soon discovered that the Aegir was poorly matched with the big monoblocks. The Aegir was running in stereo mode and had reached the limit of its output. I needed a different amp if I wanted to take full advantage of the monoblocks and have enough power for the horns to match the woofers. I bought a used Acurus A-150 solid state amp (super inexpensive) to replace the Aegir, which I sold. Now, 150 watts per channel was overkill for the horns, so I attenuated the gain by inserting a passive pre between the crossover and the Acurus. Could I have made adjustments solely on the crossover instead? Yes, but my artist’s demand for symmetry wanted the crossover’s knobs all to be at 12:00! OCD? Perhaps.

The sound continued to blossom, but the lower mids were still not fully present. I attributed this to not enough break-in time, although I was concerned that something else was amiss. I made numerous changes to speaker placement, listening position, room treatment, etc. with only minimal improvements. As I neared the 300-hour point of playback, there remained a nagging sense that it just wasn’t right. I voiced my concerns to Ze’ev, who asked to see the specs of the Marchand crossover. In the meantime, I had auditioned, then borrowed a pair of Voxativ AC 1.6 full range drivers. I liked the difference immediately; more midrange presence was the first thing I noticed, so I thought these drivers are simply better than the horns. Maybe I’m just not a fan of compression drivers? Ze’ev pointed out that my particular crossover model had a steep 24dB per octave slope, which would have the effect of an undesirable woofer-horn integration, and could very well be the sonic bottleneck in my system. This is the precise moment I regretted the Marchand purchase.

However, I was so pleased with the Voxativs, I decided to explore their potential even more. I took a leap and ordered the AC-X field coil drivers (yes, a considerable step up from the 1.6’s), as well as the PAP C-1 analog active crossover, designed by Nelson Pass.

At long last, here I am. The system is now in full bloom. I no longer grind my teeth as I listen, as I did before when the musical presentation was lacking (and bank account shrinking). The elusive lower midrange has arrived, probably thanks to the wonderful Vovativs and the far more synergistic PAP C-1 crossover (with its 12dB slope). There is also a more palpable depth to the soundstage, bass is forthright but not overpowering, and the treble is sweet and without a hint of sibilance. I feel like I have a brand new system and I get the added pleasure of re-listening to all the favorites in my library, whether jazz on vinyl, electronica on CD, or eclectic and world music courtesy of the wonderful radioparadise.com.

I made some less-than-intelligent decisions when putting this iteration of my system together, most likely in the service of saving money. Nothing wrong with saving money, but I have learned that there is a right way and a wrong way to do that. The Quintet15’s were an intelligent decision, and Pure Audio Project’s customer service is unequaled in terms of personability, genuine concern for customer satisfaction, and timeliness. After replacing the crossover, I now look forward to trying the horns again, as they have a solid reputation and deserve a second chance. I have also replaced the Acurus with a NuPrime ST-10 Class-D amplifier for the full range drivers, which I feel is another story altogether. Suffice it to say, Class-D is becoming a serious topology, and one that will likely supplant hot and bulky A and A/B amps in the years ahead. I can hear the groans of disapproval now.

That brings me to the present. Have I acquired my “end game” setup? Only inasmuch as any audiophile has, as we all know this endeavor rarely actually ends. Right now, however, this particular journey has come to a close. There will probably be more (new phono cartridge on the horizon?), but Pure Audio Project will remain a fixture, and any additions or improvements will be in the way of details.”

Matt Wilkins, NC, USA

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