History Of home Theater Systems

[Don]

or, Why You Need More Than Two Loudspeakers

In real life, our ears and brain interpret sounds from every direction, in a 360-degree circle, including even the dimension of height. Like a super computer running in high gear, our sophisticated hearing system decodes spatial and directional information in real time, telling us instantly the tonality, frequency content, and loudness of sounds from all directions.

Simple stereo, on the other hand, uses just two speakers at the front left and right, to try and simulate the complex directional and spatial information that we hear in real life. It does a decent job of reproducing a musical event, even fairly impressive at times. But it is limited to those two boxes up front, and two directions, give or take a bit. Even as early as the 1930s, Bell Telephone scientists concluded that a minimum of three channels were necessary to convey a reasonable simulation of an orchestral performance--two channels at the left and right, and one in the middle.

In the late 1950s and '60s, Hollywood sound engineers realized that more channels of sound were better, and added magnetic stripes to the edge of epic 70mm widescreen movies, which delivered up to six separate "tracks" or sound channels. Audiences loved the effect: Multiple channels more closely approximated the multidirectional sounds our ears pick up in everyday life. There was a center channel behind the screen for the actor's dialogue; left and right front speakers for the music, and eventually, left and right surround speakers on each side of the movie theater for ambient sounds-the wind in the trees, crickets in summer, and the howling of wolves. Yikes!

But back then, home audio technology wasn't up to the task of duplicating these events in our living room. Now it is, and it's called "Home Theater"! First came Dolby Surround, with four channels, in the 1980s, and now we have Dolby Digital 5.1-channel sound on virtually every movie issued on DVD. That's six separate or "discrete" channels of sound: left and right front main channels (like stereo), a dedicated center channel speaker for dialogue to anchor the actor's voices at the TV screen no matter where you're sitting, two left and right surround speakers at the sides of your listening area for all those ambient environment sounds, and a sixth deep bass subwoofer channel-it's the ".1" in 5.1--which contributes the shakes and shudders of thunder, explosions, and powerful musical bass effects. If you've kept count, that's a total of five "satellite" speakers--plus one subwoofer for ultra-low bass. Now you see why we need six speakers. And those engineers are working on one more, for height!

[toecheese]

This might be a good question to ask here: why is it .1 anyway? Are the normal 5 (or 6, 7) channels not full range in that the signal that would get crossed-over to the sub anyway? Right now, I can play with my crossover such that stuff that would get sent to my mains goes to the sub as well.

[Otto]

Hi toecheese,

I believe it's because the 5,6 or 7 channels are full range, and that the LFE channel is not, so it's designated the .1 -- it's only a fraction of the others.

[toecheese]

Oh, I know the .1 is not full-range- but my point is- can't the receiver peel off the LFE and send it to the sub anyway? Why even have a .1 channel? It's non-directotional anyway, unlike the other named channels.

[Otto]

I can play with my crossover such that stuff that would get sent to my mains goes to the sub as well.

Yeah, you can do that, especially if you have "small" mains. You are then using your sub to recreate the signal that your mains cannot. Nothing wrong with that. I see your point here -- let's say you're using 10% of the mains' signal and sending it to the sub, call it a ".1". Why, then, have a separate .1 if you can just send the low frequency part of your mains to your sub using your receiver or pre/pro's bass management?

can't the receiver peel off the LFE and send it to the sub anyway?

Sure, and it should. I don't think I've ever seen it in reverse -- adding the LFE into the L/R and sending it to mains, although such a feature may be useful if you have no sub and do have an amp and speakers that could handle it. Anyway... As you know, LFE stands for something like Low Frequence Effects, so that channel has been designated for things that the "artist" doesn't necessarily want in the mains. The program material in the LFE is distinctly separate from the other 5-7 channels.

Why even have a .1 channel? It's non-directotional anyway, unlike the other named channels.

Also, those with "large" mains may not want to employ any bass management, and use only what's been programmed into the DVD's (or whatever format's) 5.1 or 7.1 channels. Maintaining the stereo signal to full range fronts can assist imaging. Although bass is generally considered non-directional below certain frequencies (usually 80Hz down, but I might even suggest it needs to be lower than that to be non-directional), it can still be localized. I can tell my sub's behind me from time to time during movies, less with music. I also have a sub in each of my mains, and those help smooth out that ability to localize the sub problem (for me).

One more thing -- if your DVD player is doing the DD/DTS/whatever decoding and you are using the 5.1 or 7.1 channel inputs on your rec/pre/pro (or perhaps even an integrated amp of some sort...), then you have no bass management, and can still get all the workings of the format. Probably an unlikely usage in this day of reasonably-priced receivers, but possible, I suppose.

So, I guess I don't know the official story, but that's my best reasoning for this morning!

Have a nice day!

[John S]

Speaking of the history of home theater, could this be the first mention of it in print?

[Sonnie]

Where in the world did you dig that up from? lol Philco... been many years since I've heard that name. Hmmm... pretty expensive too back then. Gives true meaning to HTIB.

[John S]

Sonnie, I found this and thousands of others archived:

http://scriptorium.lib.duke.edu/dyna...kTextView/2964

[Wayne A. Pflughaupt]

Nice write up, Don!

It looks like your info for music reproduction kinda “morphed” into movie/home theater reproduction, though. The fact is, two speakers do a fine job of reproducing music (although I expect three would be better, as the Bell techs found), because it mimics a live performance, where the players are always in front of the audience. However, extra speakers for music reproduction are useful for adding ambience and/or mimicking a venue’s acoustical signature. The music DSP effects my Yamaha has do this, and it can be very gratifying.

Regards,
Wayne