Tutorial: Center Channel Lobing

[heeman]

This is a very interesting subject.

Perception is key and is very subjective until you introduce data from measurements taken in the environment like Flint has.

However, can the data be supported with blind listening tests and do we all hear everything equally like the microphone in the analysis equipment, probably not.

Variables and more variables.........

 

[Orbison]

In every instance, the surrounds are very much smaller direct radiators; and there are more of them in order to create a "blanket" of diffuse soundfield throughout the audience.

So would you agree that bipolar type speakers are a decent choice for surrounds (for movies) as opposed to twice as many "small direct radiators"? Or are bipolars still frowned on in that application?

 

[soundhound]

In every instance, the surrounds are very much smaller direct radiators; and there are more of them in order to create a "blanket" of diffuse soundfield throughout the audience.

So would you agree that bipolar type speakers are a decent choice for surrounds (for movies) as opposed to twice as many "small direct radiators"? Or are bipolars still frowned on in that application?

I think Bi polar surrounds would certainly be useful for surrounds (although I stick with monopoles). The directionality from the surrounds on a dubbing stage is more general than specific due to the multiple surrounds per channel.

 

[Orbison]

Thanks SH.

 

[Deleted member 133]

For multi-channel music, then identical speakers might make sense, but even then the surrounds take a more subordinate role than the fronts, so the speakers can reflect that by being smaller. Besides, multi-channel music is really a dying format.

Unfortunately true - and perhaps with one foot already in the grave. However this does not in any way alter one's potential enjoyment of the not-insignificant catalogue of titles that's already out there. Over the last year I've expanded my SACD collection significantly, buying both new and used titles at a fraction of their original prices. On quite a number of these there can be significant involvement of the surround channels. "Realism" and "enjoyment" are two completely different matters; I seriously enjoy multichannel recordings. Some of it realistically represents what I remember "live" performances to sound like (vantage point somewhat dependent), but that which does not can still please.

Jeff

 

[Botch]

However this does not in any way alter one's potential enjoyment of the not-insignificant catalogue of titles that's already out there. Over the last year I've expanded my SACD collection significantly, buying both new and used titles at a fraction of their original prices.

I'm doing it rong! :angry-banghead: (to fill you in Jeff, I just paid over $100 for one SACD that I really wanted). I agree, though, you can get a lot of titles inexpensively and I'm expanding my collection right now, too.
Tom Petty has released their latest album and Damn the Torpedoes on Bluray audio, and King Crimson and Porcupine Tree are re-releasing DVD-A's, but it hasn't started a trend like I'd hoped...

 

[Flint]

SH is absolutely correct. Cinema soundtracks are mixed and mastered using diffused surround sound. Hence the THX spec calling for dipole speakers and sometimes additional decorrelation processing. If you wish to accurately reproduce a movie soundtrack as it would be heard in a cinema theater, then that approach is ideal.

However, most TV shows, DTS recordings, and nearly all surround music recordings are mixed and mastered with identically matched speakers. So, the ideal for reproducing most TV siundtracks or any soundtrack mixe with matching speakers is to have matching speakers.

I've seen professional design guides and several HT installations with both identically matched and diffused sound speakers for surround duties with a method for switching between the two in order to get the ideal for each type of content.

 

[Dennie]

In every instance, the surrounds are very much smaller direct radiators; and there are more of them in order to create a "blanket" of diffuse soundfield throughout the audience.

So would you agree that bipolar type speakers are a decent choice for surrounds (for movies) as opposed to twice as many "small direct radiators"? Or are bipolars still frowned on in that application?

Because of my partially open back wall of my HT/Living Room and many door ways, I run dipole/bipole switchable surround speakers and it works fantastic for movies. I leave them in the dipole position, as almost all of my music listening is in 2 channel.



Dennie

 

[yromj]

The best movie experiences I've had were either in my theater or in an iMax theater. iMax theaters use 5.1 w/ monopole surrounds. They are the only theaters I've been in where effects are not smeared all around but actually move through the auditorium. Granted many effects are ambient (wind, rain, etc.) but there are also many many examples of effects in today's movies where sounds are also placed in the sound field (birds chirping, people's voices in the background, bullets whizzing from distinct locations, etc.).

Monopoles are what we use to create an image for the front of the room and they do that very well. They can also help us locate a point source sound where multi-poles can not. Let's face it, when someone behind and to the left fires a gun there is a point where that sound comes from and it doesn't have to be at one of the exact locations of a speaker, either.

John

 

[MatthewB]

Thanks for sharing this Flint, having tried both ways I couldn't tell a difference but then again I am always in the sweet spot. Having heard your system Flint, you have to have the bionic hearing being able to hear audio dropouts because of all your room acoustics and perfectly designed speakers.

 

[malsackj]

for the people that have not been able to detect and hear the loss of the frequency you might find it easier to find when using a pink noise source in the single speaker to an RTA and as you move you can watch the mic and RTA signal for the dropped frequency and listen to the change in the pink noise. This can help you to train the ear and mind to see the drops and peaks. It drives the family bonkers.

You can also use a graphic EQ to pull down one band and hear this from one position.
The graphic EQ will be broad effect and not as narrow as some of the problem areas when doing the walking test. Also the walking test may not have a 6 to 12 db drop that can be achieved with a EQ. Getting the ear trained to detect 3 to 6 is a good goal.

 

[Flint]

I avoided this advice. If a person cannot hear it, or they think they cannot hear it, then giving them an easy way to prove they can hear it is kinda like opening the curtain and exposing how a magic trick works. It could be very diappointing to someone who completely loved their system and felt it had no flaws.

A simple and very easily audible test is to play pink noise through the center channel alone then move about the seating area. Do the same for the left or right speaker alone. Compare between the left speaker and the center speaker as to how the sound changes while moving around and you'll clearly notice the difference. You can somewhat get the same results by standing up then sitting down while listening to a upright, vertically aligned speaker playing pink noise.