Zu introduces Soul 6

Excellent informative post, Phil.

Thank you Phil for a great and very complete review. Worth the wait!

My only thought is that it would be nice if one of your tube amps was one any of us could relate to or might have heard - just as a benchmark of sorts.

Also what's your turntable set up?

Amps:

• Williamson. This is a classic push-pull circuit that debuted in 1947. If you have owned a vintage or modern push-pull EL34, KT66, 6L6 amp, you know the realm. My pair are wired for triode output operation. 18w.
• Quad II. I have both made-in-UK by pre-Asian-owned Acoustical Manufacturing Ltd, and Xiao Nan's top clone updated via his proprietary transformers. 12-15w, depending how measured.
• 300B and 2a3 push-pull triodes: Lots of variety in how this genre sounds, both in transformers and circuit execution, as well as in what power tubes you choose. Mine are quick, modern, rich and smooth. 18w and 13w respectively.
• The F2a amp is a modern clone of the old Klangfilm 204 studio/theater single-ended pentode amp, in this case minus one voltage amplification stage and with better transformers. Shindo also makes a couple of F2a amps. Mine are fast, linear, revealing. 10w.
• The EL156 single-ended amp isn't a clone of a vintage circuit. It's a Xiao Nan design leveraging a vintage tube not well known in the US. It was introduced in Germany during the '50s tube wars to compete with the KT88 and 6550. It, along with the F2a, are among the Deutsche Post 10,000 hours tubes. It was and remains one of the best, most linear power tubes ever made. Clean and strong. 18w.
• PX25 SET. This is a Xiao Nan simple circuit, with AC filament so it has a little hum still to be tuned out. 6.5w. If you've owned or heard a modern single-ended triode amp, you know the realm.

Analog: On both of my systems, each is equipped with a Luxman PD444 direct drive turntable. This is one of the 1970s Japanese legends. The 444 accommodates two tonearms. One has a Stax UA70 long arm and a Thorens TA-110 standard length. The Stax has an Ortofon SPU -A Gold; the Thorens a vintage Denon DL103M or DL305. The other Luxman has Victor (Japan) UA-7045 10.5" tonearm and a Victor UA-7025 std length. The 7045 carries an Ortofon SPU Meister Silver; the 7025 a Zu103. I sometimes trade out one of the long arms for a Thomas Schick carrying an Ortofon SPU Meister Silver with a Ruby cantilever. There are a handful of other cartridges that see less time in grooves.

Phono preamps are Nagra BPA, Parks Audio Puffin, Soundsmith MCP-2 Mk II, M2tech Joplin II phono ADC fed into DAC.

The Definition 4 system uses a Luxman TVC for linestate control. The Druid 6 system has a Melody HiFi Pure Black 101 6sn7 linestage in the preamp role, stuffed with unobtainium 1944 production Sylvania metal-base chrome domes.

The Bricasti DACs are M21 Platinum and M1LE-Gold.

Phil

Wow what a great write up - thanks Phil! This is the clearest Zu review I have seen yet, and helps me so much as I contemplate my next speaker move. 
 

I currently run two systems - the “big” system consists of restored stacked Quad 57’s fed by Atmasphere M60’s. My “casual vintage” living room system consists of a restored Marantz 8b amp + McIntosh MX110z into a trusty but tired pair of 1964 Wharfedale W90’s. Needless to say the Quads have ruined me for pretty much all other speakers. I tried replacing the W90’s with a pair of Devore O93’s to try a vintage + modern approach, but felt the O93s sounded slow and sluggish, and overly rich - esp when compared to the Quads. So, I sold them and am wanting to try the vintage + modern approach again, but this time maybe with a pair of Zu Soul 6’s. Based on everything I’ve read, they sound like a good match for the 8b, and have lots of speed and snap - closer to the Quad sound. They also have high WAF, and would fit in nicely with the rest of my mid century decor and gear, a big plus. 

I was also considering the Soul Supremes, but it seems like they would need a sub based on what I’ve read, and what i am trying to achieve. Plus, Soul Supremes are now up to $5k in the finish I want (American walnut), so it seems like a better idea to just cough up an extra 1k for the 6’s? The most important thing to me is how the 6’s sound on electric guitars (Zappa, ZZ Top, Paige, Clapton etc). I am a guitar player and collector, so the tone being “just right” is always my main goal.

Also wanted to ask Phil - Do you have any additional observations or comments after living with the 6’s for a few more months? Any other new Soul 6 owners want to chime in? Thanks!

rhythmnsound,

I owned quad ESL-57 and then stacked ESL-57 40 years ago. Loved them. WIth the right tube amplification and absent deep bass cravings, that is a compelling combination that spoils you for many modern alternatives, within SPL and dynamic limits.

I got into Zu 18 years ago after a multi-decades search for something that would deliver the immediacy of Quad ESL, crossoverless lack of choke points, and with the dynamic shove of an efficient dynamic speaker. From 1980 to 2004 that wasn't available, so I settled on reasonably-efficient 2-way systems. I also ran those Quad ESLs on a precursor to Atmasphere -- Julius Futterman hand-built OTL monoblocks, so we're roughly on the same page if time is offset by many years.

I have listened to many Devore-based systems. The central problem with Devore is poor integration of the behaviors between drivers. Particularly, the woofer behaviors are laggard, so in every Devore speaker I've heard, one hears disparate driver behaviors accentuated by bloated bass that just throws off any chance of coherency. I hear the crossover choke points over unified tone and time/dynamic behaviors, and the differences in tweeter and midrange dynamic behoaviors.

The Marantz 8b can sound old school and slow with certain tubes. If you are aiming for that quick, articulate, acrobatic Quad ESL sound from that amp with a dynamic (Zu) speaker, stuff it with the STR-450 EL34 tube Mesa Boogie sells (NOS last production Siemens/Germany). They are hypertested, reliable, crisp, clean, fast and toneful.

Once you do that, amp attributes accrue to Zu speakers. If you can't do Druid 6, Soul 6 is Zu's most lightning-quick, agile, acrobatic, responsive.speaker, and when you get the Griewe floor Gap adjusted, it's good for easily recognizable 32 Hz tones with an expansive, point-source dispersive soundstage

Point is, if you appreciate the agility of stacked vintage Quad ESL-57s, Soul 6 or Druid 6, or for that matter any Zu speaker is the closest dynamic equivalent for practical use in domestic spaces, and it will blow away the Quad on dynamic elasticity, tonal realism and convincing bass.

Phil