Phono Stage upgrade to complement Dohmann Helix One Mk 2

Dear @mijostyn  : "  without subwoofers the SoundLabs will crap  a brick regardless of what amp you are using to drive them. "

You are rigth and is my experience not only with the Soundlab and other electrostatic . Electrostatic speakers could start to fail between 35hz-40hz and down listening at live MUSIC SPL and as you said it's a matters of distortion levels and that's why any passive dynamic speakers needs to works with subwoofers no matters what.

To handled " accurately " that  low bass subwoofers is a must and have not substitute.

R.

The thing is that Mijostyn chose a not very challenging piece of music (Waltz for Debby is hardly equivalent to the 1812 Overture), played by a jazz trio to boot. You say that any ESL starts to fall off at 35-40Hz. Even accepting that lower limit (which I don’t because the lower limit will be different for diaphragm surface area, stator to panel spacing, etc), there is probably nothing below 40hz (>2 octaves below middle C) in Waltz for Debby. There’s no way to prove my point, since you guys cannot make it to my listening room, but I have no problem with Bill Evans Trio playing anything at realistic SPLs. A small factor to consider also is that Mijo and I previously guesstimated that my speakers have about 400 sq in more radiating surface area compared to his (because mine are wider by 4 inches). Whether this makes a critical difference to bass extension or not, I do not know, but it doesn’t hurt. I also think the curvature of the PX speakers is greater than that of Mike’s speakers, and that might also reduce phase cancellation of bass frequencies. Finally, I do not and did not claim that using a subwoofer would not be beneficial where the music is a really severe test of bass delivery. And yes, a subwoof also helps in a more minor way to reduce distortion in upper frequencies. (Doppler distortion in panel speakers is real in theory and controversial in its actual importance.) Finally, my speakers are easier to drive than any OEM Sound Lab speaker all of which use an RC network in a passive crossover in conjunction with the bass and treble audio step up transformers. Having said all that, rest assured I do think about adding subwoofers once in a while, but if I did I would cross over at maybe 60 to 80Hz and use a very fast subwoofer that can blend with an ESL, not a behemoth. Meantime, since 80-90% if my listening is jazz, I do not feel deprived of bass.

You got me to doing some research on the internet. This is on Wikipedia in the entry about the double bass, the instrument most commonly used in a jazz rhythm section: "The lowest note of a double bass is an E₁ (on standard four-string basses) at approximately 41 Hz or a C₁ (≈33 Hz), or sometimes B₀ (≈31 Hz), when five strings are used. This is within about an octave above the lowest frequency that the average human ear can perceive as a distinctive pitch." The largest Sound Lab ESLs can easily reproduce the lowest tones in a jazz trio or small ensemble, given an amplifier that is suited to the job.

Here's a reminder for the tone purists:

musical instruments (piano included) have complex harmonic structure: the fundamental has a frequency, but striking a note on a piano keyboard means as the sound resonates, many harmonics (integer multiples of the fundamental) also are generated. Each instrument has it’s own characteristic harmonic structure - what we can think of as timbre.

I think this can be summarized as "real music has distortions", albeit harmonic distortions, and, generally speaking, the louder the instrument is played, the more harmonic distortions are induced.  This musical principle may not carry over to modern electronic music.

@lewm , the wider speakers may have more baffling effect which theoretically might help them with bass extension. My point is that I do not want them making bass at all. At the volumes I listen at with the music I listen to (Porcupine Tree is on right now) The bass greatly distorts everything else and cuts my headroom by 10 dB or so. The Sound Labs I have are not standard models. They are 8 foot tall 645s. They have exactly the same horizontal dispersion as your 845's, 45 degrees. I did not go for the 845s as the additional width would have been a tight fit in my situation and the extra surface area did not matter to me as I already had a subwoofer array and the right equipment to manage it. I was getting plenty of volume out of the Acoustats, a speaker 16" narrower than the 645-8s. I was sure the 4"s would not be a sacrifice. 

ESLs are not like dynamic speakers. They do not have the capability to take long excursions and they become non linear quickly under 100 Hz at higher listening levels. Because there is only one driver expected to cover the entire range the entire frequency range is affected by this non linearity. If you play them at lower levels avoiding the non linear zone of excursion they are fine. That is just not my style. Aside from this dipoles make very lumpy bass at best.

Subwoofers are a difficult topic. As @rauliruegas infers they are essential for realistic playback with almost any loudspeaker. Very few speakers produce adequate bass below 40 Hz. What a loudspeaker does at one meter is a far cry over what happens in a real room. The life and breath of music and the venue it was recorded in lies below 40 Hz. It is where concert halls breath and bass reverberates. It is the difference between a live performance and a transistor radio. To make realistic bass a system has to be tailored to it's environment. This requires digital signal processing. The only other way to do it is shear luck and you might as well buy lottery tickets.

Sorry for rambling on. I ripped my right forearm apart today, spent all day in an ER and am souped up on oxycodone.