Mighty 1650 said: "FWIW many broadcast processors correct phasing issues when swtiching down to mono."
The phase correction feature is something that deserves its own thread and many comments from anyone who can describe how it works and exactly which processor models provide the feature. I would suggest that phase correction should be on the list of must-have processing abilities for radio transmitters.
Must have features include:
Compressor to raise average level to bring the station forward on the dial and overcome ambient noise in the listener's environment;
Limiter to allow maximum level while preventing over-modulation;
Equalization to place sonic energy in the audible region heard by the average ear and reproduced by typical loudspeakers;
Phase Correction to maximize monaural quality without diminishing stereo quality.
Those are some features everyone should have for their transmitters.
A huge part of the discussion is whether these things are done with software or hardware.
On typical harware processors, i have never seen phase correction to realign left/ right phase to make mono better.
I have only seen seperate boxes like the Howe Phase Chaser, that i expect would have a variable delay/lag to one chanel to automatically align phase with the oposite channel to compensate for better mono or stereo phase compatability.
These units were typically used for tape head mis alignment correction.
Paul.
I may have gotten confused by the big red "polarity" light displayed on the Optimod 9000A. I had understood this to correct stereo phasing issues, until I just remembered the 9000A has a mono input. Whoops!
The 9000 has a phase flipper that changes the phase 180 degrees if the negative modulation peaks are greater than the positive peaks.
This is to maintain speech asymetry peaks are mainly kept in the positive direction.
The 9100 optimod superceeded this with a phase rotator to make speech more symmetrical insted.
Paul.
Absolute phase is something I don't recall being talked about on these forums but we are talking about it now since the previous several postings about the Optimod 9000/9001 are talking exactly about maintaining "absolute phase."
It is such a real topic, in fact, that Wikipedia has a whole page devoted to it.
if you want to hear really good mono then listen to WSM 650 within their 5mV contour. sounds almost as good as mono FM!!! i run mono on FM due to the extremely low power signal we are allowed.
The Pretty Things are a band that were contemporaries of The Beatles and Moody Blues, recording in the late 1960s at Abbey Road. They said they weren't able to play their album S.F Sorrow live until 1997, because of all of the studio effects, and technology wasn't advanced enough. I was watching the live video on you tube, to be found under Pretty Things live Abbey Road.
Carl, you should have a phase corrector in Stereo Tool! I'm not sure how to run it over files, but you can stream through it. It can improve the sound on things like old cassette and open reels and they should be more mono compatible. I'm not sure how broadcast processors intelligently fix phase issues on the fly, because phase correction can hurt some recordings that deliberately use phase effects!
Older mp3 encoding could totally ruin the sound of a stereo source that came with phase issues, and I mean render it unlistenable. Now you can use 320 kbps dual channel and LAME, but way back it was Xing 128k for dialup.
I know that Thelegasy is totally gone on high fidelity in Album Rock, and I'm all for it, it's good that someone is trying to promote higher fidelity in radio broadcasting, not just accepting the normal way people are listening, but trying to do a little better and show the way it should be done. Someone has to the the Poet and someone has to be the Radical to affect change. As for the Moody Blues albums you mentioned, those should be in stereo on big speakers or good headphones, they seem to be made for it and lack the punch on mono AM, though it's better to hear them than not hear them.
I'm glad that processors have gone to phase rotation, it does spread the power of a speech waveform out, something that easy to see in a wave file by comparing the original and processed waves. There was a time when the rules allowed AM radio to have an unlimited positive peak, so it could be well beyond +125 %, so phase flipping would probably an asset more at that point, getting 150 to 180 % peaks, which wouldn't be hard with some voices.
Also, what do you think about the Beatles remasters from 2009, have they fixed up a lot of the stereo issues you've talked about?
Most albums that are considered Classic (insert genre here) were at some point recorded with AM Monoral sound in mind simply because not everyone was sporting a true hifi stereo system. Heck most were listening on a small portable AM radio.
Barry jogged a forgotten memory from the pre-FM stereo days... when rock and roll AM dominated the airways.
Yes, I remember that singles used special equalization curves intended to make the song JUMP OUT on AM stations.
They were not concerned with stereo in those days as far as radio play was concerned.
Yes those were the good old days. Good old AM radio with great DJs and the hit parade....the true age of radio....no one cared about stereo. Cars came with an AM radio and one speaker in the center of the dashbord.
Mark
I do like old pop records with the vocals front and center, it's an exciting kind of sound, especially with a good vocalist! Motown comes to mind. On many I can even hear the rest of the band being turned down or just taking a cue and playing quietly when the vocalist is on. Now records are recorded so differently, it seems like they're using processing to get everything to fit.
The processing used to "get everything to fit" is hypercompression.
They do not play well with audio processing,and sound horrible, i avoid these tracks as much as possible.
Paul.
And if the car was really cool you had a rear speaker and a fader control.
Don't forget the "spring reverb" unit.
Yep! I once saw rear speakers called "Heavenly Horns." The sweetest sounds this side of Heaven.