For stereo imaging, do only L-R differences matter ?

[wchang]

A related topic - I sometimes see photos of listening rooms where 2-channel audio is being fed to 3 channels, Left, Right, and center.

I have often wondered how the 2-channel stereo signal is split into 3 channels. Is it as simple at (L), (L+R), (R) ? This seems like the most straightforward way to do it... But I could also imagine a split of (L-R), (L+R), (R-L). This seems like it might not work well with some recordings... ? Thoughts?

j.

I just happen to have spent all yesterday experimenting, after a few months' hiatus from "console stereo". No, your question must have been the trigger. There are two still-active relevant threads here and occasional posts to the fullrange gallery on this subject. I think it's complex and here are some excerpts.

(culmination of my wall-bounce biamp off-the-shelf console)
https://www.diyaudio.com/community/...from-a-single-loudspeaker.200040/post-7681161

(@acmn method, if same 3 drivers star & series-connected then 2L-R | L+R)
https://www.diyaudio.com/community/...from-a-single-loudspeaker.200040/post-7690681

(the crux of the problem I think)
https://www.diyaudio.com/community/...ntom-center-image-problem.393540/post-7688840

(@ASCTim explanation of trade-offs)
https://www.diyaudio.com/community/...ntom-center-image-problem.393540/post-7691065

(Hafler mystery, to me)
https://www.diyaudio.com/community/threads/full-range-speaker-photo-gallery.65061/post-7605036

I'm very new to this "nonstandard stereo" thing and have my own (immediate) needs and therefore biases. I'll try to summarize my many experiments later. Short conclusion is that differential (L-R, 2L-R etc.) in principle reduces stereo separation at high frequency producing enhanced mono; then tricks are needed to recover stereo effect.

 

[wchang]

Addendum: I'm listening to a modified, symmetric version of "Hafler differential" using four drivers (Tangband W3-871) instead of three with a symmetry-breaking middle. Sounds great, though I can't say stereo soundstage is any wider. Maybe someone can simulate the circuit (from @MITsound). The driver I added, third from left, is just the second driver reversed polarity (the short divider helps). If these two are swapped the sound becomes hollow and shrill.

Uncannily, from the position where I took the photo, the arrangement sounds just like sitting at a real proper-sized harpsichord, the music coming from beyond the drivers in stereo. Must be how it was recorded. (Celine Frisch, Bach Goldberg Variations.)

 

[freddi]

very interesting - I used the "DynaQuad" 50+ years ago and around 50 ago with four Dynaco A35XL and a Citation 12 amp. That really unlocked loads of low frequency ambient information sounding great on Sinatra's "Only For The Lonely" LP. (the CD is quite good too)

I've never been up close enough to a real harpsichord to hear one. I
like the revival iron frame Pleyel instruments a lot for color variation and strong tone.

Seems to me one way to mic a harpsichord for recording would be to use PZM mics on the lid. Some live recordings at Youtube sounds pretty bad.

I'm a huge admirer of the "Goldberg" variations - including one performance on a Kurzweil piano/synth.

In the rare case you've not heard it -

ah - here's an old upload of a 1963 Goldberg set by George
Malcolm - I don't believe I've heard it.

Harpsichords with the bass pedal clavier are fun - I bought the E. Power Biggs LP when first released.

Oh - are there any modern recordings of the Siena Pianoforte? ITs vintage recordings have fascinated me for nearly 60 years.

 

[rayma]

Appears that piano only survived into the 60s.
https://en.wikipedia.org/wiki/Siena_Piano

 

[freddi]

@rayma - I believe it was up for sale in Israel a few years ago

Its a shame recordings aren't done with it (assuming its s in playing shape)