I'm never going to hear a megaspeaker in a good room am I?

Erik, when I get my $50,000 speakers I'll invite you over so you can have a listen.:)
roberjerman, headphones provide a good datapoint for spectral balance but that is about it. If the system is so bad that you need to resort to headphones you have a lot of work to do and wasting money on headphones is not going to get you there. 

Hello Erik,

     I don’t understand why you would want to waste your time listening to $40K plus speakers in a good room if you have no intention of purchasing them.
     But I actually did attend a private audition, presented by Mr. Diller at a local high end shop, of the $30K Magnepan 30.7 speaker system which consisted of a pair of 7’ midrange/treble panels combined with a pair of some sort of rather large subs. This system sounded spectacular in the shop’s well treated room but I still had no intention of spending that much dough.
     It sounded so incredibly good, however, that it caused me to try and replicate a mini version of it in my room and system. I already had a very high quality Audio Kinesis Debra 4-sub distributed bass array (DBA) bass system that was flat down to 20 Hz in my room. I then replaced my aging Magnepan 2.7Qr main speakers with a used pair of much newer 3.7i speakers, with the true-ribbon treble section and in like new condition, for about $4K.  Voila, a  mini Magnepan $30K 30.7 system for a total price of $6,800.
     The result? The overall sound quality of my custom mini 30.7 system in my well treated room is much closer to the actual 30.7 system’s sq than I ever expected. I would describe both systems as having the typical qualities of upper level Magnepan panels, a fast, smooth, open, natural, highly detailed, palpable and dimensional presentation, along with the added qualities of a very deep and powerful bass foundation combined with powerful full range dynamics, which are not typical Magnepan qualities.
     I completely understand your desire to experience the overall sq level of a pair of mega-speakers in a high quality room. I would love to experience that, too. If you can’t afford or don’t plan on purchasing them, however, it kind of reminds me of imagining making love to an extremely attractive woman; it’s great while the experience lasts but inevitably just disappointing, and a bit sad, when it’s over and you realize once again that it’s pure fantasy.
     Don’t get me wrong, I highly recommend both experiences. It’s just that I prefer to be more practical, constructive and realistic with both the women and audio systems I choose to spend time with.
     Your world’s what you make it, go ahead and take it.

Tim

Erik, I think @mijostyn has expressed the solution for your listening challenge. Send out an open request to Audiogon readers who own a system that fits the $40k speaker criterion and politely ask to audition their systems. In return, you promise to ingratiate yourself to your host(s), tell witty stories, proffer them with wine, scotch, bourbon, homemade hummus with Moroccan dried olives, an LP they have always wanted (fill in the blank), and generally resolve be a most excellent guest.  Once Covid is in the rear view mirror, let said system owners know where you will be travelling and arrange the visit. If you cannot find any takers, I have some $4k Dalis in a big unfinished basement in NC: bring me some good bourbon, and you can hear them! Cheers!

You can come hear my $6000 Ohms.  You will forget about $40k speakers. 
Also I’ll settle for beer or Ripple.

The three speakers Erik identifies as having sounded good in "mediocre" rooms are all speakers which have relatively smooth off-axis response as well as other characteristics which generally result in good in-room response: The Vandersteen Model 7, the Sonus Faber Stradivari, and the magnificent Snell Acoustics Type A. In other words, these are not three random speakers that Erik’s ears picked out - they are three speakers which start out doing some important things right when it comes to room interaction.

If placed in a larger and more theoretically ideal room, the main beneficial differences would be:

1. Increased time delay between the first-arrival sound and the onset of the lateral reflections, and a generally increased decay time. This results in less degradation from early reflections as well as less "small room signarture", so we hear more of the acoustic signature on the recording, and less of the playback room.

2. The bass would be smoother because the larger room would result in greater modal density, which results in more numerous and smaller (and therefore less audible) room-interaction peaks and dips.

Wouldn’t it be nice if these attributes could be grafted into our typical smaller room? How would we go about doing so?

1. Let’s take the fairly wide and uniform radiation pattern of the speakers Erik likes, and chop it in half. Let’s aim half of the energy (now in a considerably narrower pattern) at the listening area, and aim the other half well away from the listening area, such that it bounces off the room boundaries a time or two before arriving. This does two things: It reduces the amount of energy in the earliest (most likely to be detrimental) reflections, and also pushes the "center of gravity" of the reflections back in time, approximating what would happen in a larger room.

2. Various techniques for improving the in-room performance in the bass region exist, so I’ll leave it at that for now.

Room interaction matters a lot to me so I am commercially involved with speakers which have these sorts of attributes. The ones which would qualify as "megaspeakers" (using the $40k yardstick) are SoundLab fullrange electrostats.

Anyway I do not subscribe to the school of thought which says that it’s up to the homebuyer to own a megaroom and up to the acousticians to make the megaroom work for the megaspeakers. In my opinion good room interaction starts at the loudspeakers design stage, whether those speakers be "mega" or otherwise. Kudos to Richard Vandersteen, Franco Serblin, and Peter Snell for paying attention to room interaction.

Duke