I understand the argument, but do not recording engineers add extra microphones to capture these late reflections and mix them in the recording?
I think that late reflections are indeed captured and added to the mix, but it is impossible that a 80 ms concert hall reflection from the rear comes with 80 ms delay from the rear of your listening room when all you have is a 2-channel system.
Blauert has discovered that signals in certain frequency bands (he called them directional bands) are perceived as coming from e.g. above or behind with the sound source being in front (Blauert, “Sound localization in the median plane”, Acustica 1969/70, p.206; Blauert, “Localization and the law of the first wave front in the median plane”, JASA 1971, p.466). This means that by spectral manipulation source elevation can be simulated (Bloom, “Creating source elevation illusions by spectral manupulation”, JAES 1977, p.560). By some manipulation (spectral or phase ?) it is also possible to extend the soundstage to beyond the speakers, as can be heard on Chesky JD37.
I don’t know to which extent such manipulations are used in commercial recordings.
I think that our room does not need to be larger than the acoustic space - I have heard systems where the soundstage was much larger than the room.
What were those systems?
IMHO, the most difficult thing to get in the reproduction of a symphony orchestra recordings is the sense of power - loud but without overloading the room and us.
E. Brad Meyer has written a piece entitled “Power, how much do you really need?”, can’t find it any more on the web, could send you a pdf if interested. Depending on your system, personal needs and listening habits, you might need a lot of power indeed. In orchestral pits sound power levels of up to 115 dB SPL have been measured. For very loud rock music (116 dB SPL), Meyer indicates the following: 40 Wpc (99 dB/W/m), 631 Wpc (87 dB/W/m), 2,512 Wpc (81 dB/W/m), figures are for 2 channels driven. A SPL calculator can be found here:
http://www.hifi-forum.de/viewthread-42-61.html
where
Kennschalldruck: Loudspeaker efficiency
Verstärkerleistung je Lautsprecher: amp power per channel
Anzahl Lautsprecher: number of loudspeakers
Abstand zu Lautsprecher: listening distance
Lautstärke: Sound pressure level
Also interesting reading is:
http://www.silcom.com/~aludwig/EARS.htm#Soft_sounds_and_loud_sounds
Overloading the room and us: my active speakers have 2x920 Wpc, which, according to Meridian’s Bob Stuart (Audio 1987, Sept., p.64: The case for active speaker systems) is equal to about 3,000 Wpc in a passive system, maximum SPL at about 135 dB, thus plenty of headroom for whatever comes along. My 2x40 Wpc desktop Genelec begin to thermally compress when being pushed hard, it’s not too loud but very unpleasant and makes you turn the volume down. My main monitors just play loud, very loud, without perceivable thermal compression, so loud without becoming annoying is possible.
Klaus