Speed kills....

Erik, as you know ESL’s aren’t the only dipole planars. Magneplanars and Eminent Technology LFT’s, both magnetic-planar/ribbon speakers, also have nulls to either side (their radiation pattern is a figure-of-8), but they don’t have the apparent speed of ESL’s, or their liquid see-through transparency and low-level detail. Roger Modjeski says that’s because of the extremely low moving mass of the Mylar used in ESL drivers.

The thought of ESL speakers with direct-drive tube amps really has me lusting. Guess I’m gonna hafta sell some of my vintage drums!

My present speakers are hales t8's (hales has been out of business a long time ago) and they are about as far away from that ideal as you can get.  

 Roger Modjeski says that’s because of the extremely low moving mass of the Mylar used in ESL drivers.

Ime Stax headphones are a very tough act to follow. What they do well, they do very very well.

In general I think the closest approaches in a loudspeaker system will be what Erik suggested, "large drivers in a well treated room." And imo those "large drivers" can be dynamic or electrostatic.

When it comes to the subjective impression of "speed", imo the factors that come into play include the frequency response; power-to-weight ratios (motor strength vs moving mass); coherence of the leading-edge of the waveform; and smooth and quick and uniform decay at the trailing edge of the waveform. Imo amp + speaker + room = a "system within a system", meaning that how the speaker interacts with the amp and with the room both matter.   This will be an over-simplification, but the amp sees the speaker's impedance curve, and the room sees the speaker's radiation pattern. 

It may not be obvious that the frequency response plays a role in "speed", but the balance of top-octave energy relative to the rest of the spectrum is closely related to our perception of "speed". Note that most speakers are beaming in their top octave, so even if their on-axis response looks good "on paper", once the reverberant energy is factored in, they are often lacking in top-octave energy, which will manifest as a subjective lack of speed. But tipping up the on-axis response to compensate can cause listening fatigue. So imo the solution involves minimizing the spectral discrepancy between the first-arrival sound and the reverberant field.

Duke

dealer/manufacturer/feels the need for speed

Erik, there is a reason loudspeaker designers still work hard to get theirs to sound as natural (lifelike timbres, especially vocals) as the 1957 Quad ESL.

Limitations yes, but not at what’s most important to some music lovers. Add a pair or quad of dipole subs, and you may forget about what they don’t do.

Erik, did you meant to say "the perception of speed does NOT come from dispersion alone"? Or is that in fact the main tenet of your assertion?

For speaker designers who have used the Quad 57 as their standard for natural timbre reproduction, I’ve read that in interviews many times over the years (more than a few designers have Quads in their labs), most recently by Roger Modjeski, who said in an AudiogoN post that he voiced his new Music Reference Direct-Drive ESL speaker with the 57---Eric.

Thank you both very much, Inna and Russell. At least I can still talk a good game!

Russell (or anyone else!), if by any chance you’ll be at the Rocky Mountain Audio Fest in a couple of weeks, I hope you can stop by Room 3002.

Duke

@inna asked: "Could you explain in general terms your rationale behind choosing those particular drivers for the least expensive model, forgot the name, the one with big woofer and compression driver?"

I use big prosound woofers and compression drivers (mounted to low-coloration waveguide-style horns) primarily for radiation pattern control. I want the radiation pattern to be narrow enough that, when aimed properly, we can minimize detrimental early reflections. And I want the radiation pattern to be as uniform as is reasonably possible so that the reverberant energy is spectrally correct. Sometimes this calls for an additional rear-firing tweeter.

Additional benefits of using prosound drivers include good efficiency, complete freedom from thermal compression effects at home audio listening levels, and a benign impedance curve. And ime you get more bang for your buck with good prosound drivers.

Drawbacks include large enclosure size and having to deal with anti-horn and anti-big-woofer prejudice. People think big woofers are "slow". Based on power-to-weight (applied motor strength to moving mass) ratios, my big woofer falls in between the 5.5" Scanspeak Illuminator and the 7.0" Scanspeak Illuminator. Unfortunately anti-horn prejudice is harder to overcome, as many people listen with their eyes even when they don’t hear any horn signature.

The new model I’ll be showing at RMAF has a 12" midwoofer with a significantly more powerful motor, resulting in a power-to-weight ratio that compares favorably to high-end 5" midrange cones.

Actually the compression driver has more to do with the subjective impression of "speed", but I’m not sure how to make an accurate apples-to-apples comparison with a good direct radiator dome tweeter - the specs I’d need aren’t available. But I’m reasonably confident the compression driver would do well in the comparison.

Something I found over in the prosound world is that sheer horsepower matters too. There seems to be a correlation between total motor strength and how hard a speaker "hits" down low, while power-to-weight ratio seems to matter more as we go up the spectrum. This just based on personal observations.

Duke

@inna wrote:  "I don't like in your face sound of horns but I understand that's not the case."

There are a LOT of things I don't like about many horns!  In-your-face sound, tiny sweet spot, cupped-hands, and being the obvious source of the sounds you're hearing.  Ime those problems arise from horn geometries optimized for things other than home hifi.   

The geometries I use are benign as far as internal reflections go, which prevents cupped-hands effect and helps the horn to "disappear" as the sound source.  Imaging is also improved... one time at an audio show a man who had been an employee of a horn loudspeaker company remarked, "Wow, I didn't know horns could image!"  They can as long as their geometries don't work against that.  They can also have an unusually wide sweet spot, and again it's the specifics of the horn geometry (and speaker set-up) that make it possible. 

But the relative lack of reverberant energy (due to their narrow radiation patterns) does, as you noted, make horns tend to have a more "in your face" presentation.  Personally I really like the feeling of being enveloped in the acoustic space of the recording, which is just the opposite kind of presentation.  So on my more expensive systems I use additional drivers to add a bit of beneficial late-onset reverberant energy, which imo does a good job of conveying that feeling of envelopment. 

So I am very picky about which horns I use.  And even then if the budget allows, I put a fair amount of effort into minimizing and/or working around the things they don't naturally do well. 

There are a lot of intensely passionate designers out there doing their best to deliver the things they think matter the most.  It's not the road to riches for most of us, but it sure is fun.

Duke

 the perception of speed comes from the dispersion alone.