Late '80s TV sets seem to aim for good audio quality

[jedo1507r]

Originally Posted by JCFitz

Some of the best tv audio systems come in the projection sets though some still try to use relatively small speakers for such a huge cabinet.I think the biggest speakers I've seen in projection tvs are usually on Pioneer sets.Some of the tiniest are on Sony projos.They still surprise you with bass you wouldn't think could come out of those little 4 inch speakers.

Yep, I have a 2003 Mitsubishi WS-55311 (or equiv., manual not nearby) and it's equipped with what looks like two 4-inch drivers behind a removable grille. The sound is incredible for a television, but then, I have a former neighbor with a late '90s Sony Videoscope XBR with at least four speakers - two on sides of bezel, two woofers on bottom of bezel and sounded as good as a decent shelf stereo system. In this field of standalone TV sound quality, CRT RPTVs and large console televisions sound quite deep - can't do that with flat-panel televisions and possibly any microdisplay; all because of the size and possibly materials of the cabinet.

I had a 1975 Sears 25" console back in the late 90s (was my grandfathers). It only had a 3x5 speaker, but that TV got awesome audio. I was quite surprised. Sounded very hifi. Unfortunately I no longer have that TV.
I haven't had a TV with that good of sound since then.

[andy]

I once had an early 80's Sanyo, or Sears set that had stereo speakers and a simulated stereo circuit, but no audio inputs. It seemed strange that they would go to the expense of a stereo amp without allowing you to feed it a stereo signal.

[wa2ise]

A reason TV manufacturers cheaped out on the speaker (other than the obvious) is that the 4.5 MHz FM sound subcarrier (in intercarrier TV sets) tended to have incidential modulation from the video carrier. This incidential modulation comes from the video IF's frequency response curve, which is sloped at the main video carrier frequency. This is the vistigal sideband Nyquest slope. That slope induces a false FM signal on the video carrier, which, when it is beat against the sound carrier, adds its false (or incidential) FM to the desired FM that is to be the soundtrack of the TV show. That's the buzz sound you sometimes hear during quiet times in the program. But it's different than that buzz you sometimes get on some mis-adjusted sets with white lettering on the video. Often the magnetic fields from the deflection yoke will leak into the speaker to make some of that buzz. So TV makers don't bother to work hard to avoid the buzz in the detected audio if the buzz from the deflection yoke would swamp it out. And you'd use a speaker with weak response at the low audio frequencies, and also the high frequencies to avoid responding to the horizontal deflection frequency (15KHz).

Now, when stereo TV sound came out, consumers expected better sound, and really won't want buzz in it. So separate intercarrier IF strips for the sound were developed. These had peaks at the main video carrier, and another at the sound carrier. Both peaks without any slopes at these specific frequencies. When the sound and video carrier is beat against each other to get the 4.5MHz sound subcarrier, no incidential buzz happens.

Why not just treat the sound carrier as an independent FM station, like they did in the early days of TV you ask? Well, fine tuning becomes a PITA as the sound gets lost easily. Another reason is that the intercarrier system cancels out any incidential FM from tuner local oscillators and oscillators inside cable converter boxes. These were sloppily designed, as the designers knew that virtually all TVs used the intercarrier system. A crummy local oscillator would impart the same incidential FM on both the video and the sound carreirs, and the intercarrier system detector would cancel that indicential FM out. An independent FM receiver wouldn't do that.

[kichijai]

We had a 27" Zenith console from the 80s. It had one 4 or 5" speaker in the lower right that filled our big cathedral-ceilinged family room with huge warm undistorted sound. Today's cost cutting makes me sick.

[Pete Deksnis]

Originally Posted by ha1156w

Wasn't it true that the FCC rules limited the frequency response of TV broadcasts in the late 60's/early 70's? I think it was 100Hz-5kHz? ... I haven't been able to determine of any reasoning behind the limitation, only that they did it.

I haven't researched it, but I don't recall that happening, but I could be wrong. I wonder though, what benefit could come from suddenly requiring a narrowing of the transmitted audio spectrum for a few years?

Back in the '50s, IIRC, WCAU-TV in Philadelphia would use cheap 5- or 8-kc phone lines to pipe in its audio from New York. Video looked fine. But when the station switched to local programming, or even a station break, my young ears easily picked up the difference. Full 50 to 15,000 cycle response capability from local audio vs. the limited bandwidth transmitted over the same facility when fed by the low-bandwidth ATT lines between NYC and Philadelphia.

A radio station of the day would do the same thing to cut the cost of its dedicated phone lines. An AM station maybe would have one balanced line from studio to transmitter with an 8-kc upper limit, but cheaper 5-kc unbalanced (read noisy) lines would back up the good one. If you knew how to listen, the same program one day could sound different the next day.

[Whirled One]

Actually, I think those 4" or 5" single speakers used in old console TVs were considered pretty cheap even in those days, and the audio output circuit on most TVs probably wasn't much more sophisticated than the output on an 5-tube AM table radio. The reason they tended to sound fairly pleasant despite these limitations was probably mostly attributable to the fact they had the benefit of having a nice big baffle courtesy of the big console cabinet. Any small speaker will sound better if you bolt it in an opening in a nice big, reasonably-solid hunk of wood.