Showing posts with label stereophonic. Show all posts
Showing posts with label stereophonic. Show all posts

Thursday, October 26, 2017

How'd we stereo on radio before there was stereo radio?


The era of FM stereo radio began in June 1961, but the era of hi-fi stereo radio dates back to the 1950s.

But in the days before FM multiplex broadcasting, listening to stereo radio required two stations . . . and two radios, one AM and one FM. Or you could just buy a "binaural" AM-FM stereo tuner -- two dials, two tuning knobs, and in stereo mode, it would play AM and FM at the same time.

AM was on the left, FM on the right. (Unless, of course, it was the other way around. Or a complete free-for-all?)
 

What in the world would that have sounded like in, for instance, 1958? Let's take what we know about the capabilities of AM broadcasting and FM stations in the '50s, then see whether we can re-create the binaural AM-FM stereo experience.

It's November 1958. You're in Baton Rouge, La. It's 9 p.m. on a weeknight (Monday through Thursday), and you're in the mood to hear some WJBO "3-D" stereophonic sound on your new hi-fi setup.


ON YOUR NEW binaural high-fidelity tuner, your tune in 1150 on the AM dial. Left channel, check.

On the FM dial at 98.1 megacycles, you tune in WJBO's sister station, WBRL. Right channel, check.

Now it's time to sit back, relax and experience "music in three dimensions." For those of us back here in the future, the result sounds better than you would think.

Then again, so did AM radio in 1958. It's amazing what could be done with a wider AM bandwidth, owners who cared and well-engineered radios in listeners' homes.

I HOPE the following video demonstrates that, as I try to re-create what the WJBO-WBRL, AM-FM stereo pairing might have sounded like. I can't tell you how many times I redid this, trying to get the AM sound "right" . . . AM heard over excellent equipment, much better than what we're accustomed to today, from an era decades past.




I KEPT redoing this because I kept thinking, "No. This sounds too good. This can't be right."

And I kept saying this as someone who has a couple of AM-FM hi-fi tuners made in 1960 and knows that some amplitude-modulated stations, to this day, sound pretty decent on a true wideband tuner. This, despite the Federal Communications Commission -- in order to lessen interference and shoehorn more stations onto the dial three decades ago -- putting brick-wall limits on AM stations' frequency response out of the transmitter at 10 kHz.

A young person with good hearing can perceive frequencies up to 20 kHz.
 


But in 1958, many AM stations' transmitters had a frequency response almost as good as FM stations. FM's big advantage was in improved dynamic range, a lower noise floor and, as Steely Dan sang, "No static, no static at all."

Below is a rough representation of the frequency response of the "AM side" -- the left channel -- of the video above.


YOU'LL NOTE that I rolled off the low frequencies, just like a typical AM signal, then sharply rolled off the high end right below 15 kHz. I also bumped up the equalizer curve here and there to "sweeten" the sound a little, as an engineer would have done with even the rudimentary audio processing of the day. I tried not to overdo it. After all, I was worried that it sounded too good; I still wonder what I missed.

Too, the AM channel is more processed -- more compressed and a bit "louder" -- than the FM track. The reason? The easy answer is "That's what AM does."

The longer answer involves an attempt to, first, mimic the lesser dynamic range of AM broadcasting and, second, reflect that AM stations were much more heavily compressed and "hard-limited," because loudness equals distance and listenability on the noisy AM band.

Oh . . . I also added some "AM noise" to the "AM side" of the recording. Not too much, I hope, and not too little, either.

On the "FM side" of the soundtrack, I frankly worry that the audio may be too processed. Alternatively, however, if I were a chief engineer or a program director in 1958 and my AM-FM combo was going to dive into the "binaural stereo" thing . . . I'd want the FM side to match the AM side at least somewhat for loudness.

THAT'S IT for the technical and audio-geek minutiae. I doubt a normal person could stand much more.

Even if you're not a full-bore nerd like me, I hope you've still found a little fascination in this esoteric inquiry into one of the more forgotten aspects of hi-fi and broadcasting.

A phenomenon that births advertising like this (from 1959, after WBRL had changed call letters to WJBO-FM) -- not to mention a moniker like Soundascope Radio -- can't have been a total bust.


Thursday, October 15, 2015

Tonight's vinylpalooza


I'm cheap enough that paying $15 for this 1959 stereo release gave me serious pause at the LP bins of an Old Market antique emporium.

On one hand, I'd rather find a gem for a song at an estate sale or something.

On the other hand, the records from this vendor are usually in marvelous playing condition.

On the third hand, a stereo rock 'n' roll record from 1959 -- the mono version of Bobby Freeman's Do You Wanna Dance album came out the previous year -- and from an indie label, no less. That's likely on the rare side, making the $15 price not a rip-off.

I'll say!

BEFORE LISTENING to this early-rock classic this evening, I did a little Internet price checking for the stereo version of Do You Wanna Dance . . . Jubilee 1086 for all you record geeks out there. And the low price I found it being sold for was something like $29.95. The high price (on eBay, of course) was . . . was . . . gulp! . . . $110. I understand a mint first pressing goes for $200.

Mine seems to be a second pressing. Sigh. I coulda been rich.

Now note that amid all this "What's it wurf???" nerd-o-mania, not a word was written about the actual music, which was great despite following the rock-album convention of the day for a hot act. That would be:

SIDE A
  • Cover something.
  • Cover something.
  • Cover something.
  • Original that'll never be released as a single.
  • Cover something.
  • Hit record we named the LP for.
 SIDE B
  • Cover something.
  • Cover something.
  • Original that you'll hear nowhere else. Ever.
  • Cover something.
  • Original that sounds exactly like the big hit on Side 1.
  • Cover something inspiring. Or something.
That is all. Good night, and good listening.

Wednesday, September 23, 2015

How your hi-fi stereo record works

Click on the picture for larger, readable view

This afternoon's vintage-LP listening comes with a technical note.

And our tech talk today centers on a question: You ever wonder how stereo records put the stereo on the record?


Well, the top photo of the inner sleeve of our 1958 release by David Carroll and His Orchestra explains how the modern marvel of stereophonic records work. And it also contains a caveat for the stereo newbie, as nearly everyone was 57 years ago -- do not play this thing on a monophonic record player.

A mono cartridge on your mono phonograph will tear this sucker up.

See the explanation on the record sleeve for why that is.