Why many mistakenly believe M/C Surround doesn't sound right [Archive] - Audio & Video Forums

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O'Shag
07-14-2007, 11:53 PM
I'm a two channel guy, but I'm also a multi-channel guy. I've observed that many have a problem with multi-channel because the rear channels are mixed too strongly and causing to much information coming from the rear. There are several reasons this could be, but I believe this to be a direct result of a very common misconception out there. Many believe that using regular speakers for the rear provides a superior solution to the original concept of dipole or bipole speakers. The reason why regular forward firing speakers don;t work properly is that the focused sound intereferes with the front channel information, which works against the primary audio purpose for which rear speakers were designed, to increase the soundfield by providing primarily ambient information.

I've gone through several speakers for the rear, but realized that dipole/bipole speakers - that do not fire directly, but rather fire of to the sides to disperse sound in a non-direct manner - are far superior for rear channel duty. The reason for this is that the sound is not beamed directly toward the ear, but rather out multidirectionally in space. The difference is dramatic. If you are currently using, say, B&W 802s for the front, and 804s for the rear, you might try a dipole/bipole speaker for the rear channels. You'll be surprised at the difference.:6:

kexodusc
07-15-2007, 03:36 AM
Interesting points....


Many believe that using regular speakers for the rear provides a superior solution to the original concept of dipole or bipole speakers.
We're getting into an area of personal preference here - there isn't a universally accepted "Best Configuration". I'm someone who owned 2 different systems with dipoles and just couldn't force myself to like the sound - it was only when I returned to direct radiating speakers that things jived.


The reason why regular forward firing speakers don;t work properly is that the focused sound intereferes with the front channel information, which works against the primary audio purpose for which rear speakers were designed, to increase the soundfield by providing primarily ambient information.

In the age of Dolby Pro-logic, before discrete multi-channel soundtracks were available to us, this was actually correct. Today, the surround channels are mixed differently. Ambience is still important, but the approach has changed somewhat - ambience is now achieved by "blending" the sound across several speakers, much like stereo soundstaging, rather than just using the 2 surrounds as full time ambience producers In today's modern 5.1 tracks, more and more directional sound effects are are placed at the sides and rear of the surround field. Think of any good scenes where 360 panning is used - one area the traditional direct radiating speakers excel at vs dipole/bipoles is the ability to stay true to the directional cues when necessary. A voice shouting from a specific location in the rear left will sound as if it originated in the rear left, instead of being distributed over a much larger area of the room.


I've gone through several speakers for the rear, but realized that dipole/bipole speakers - that do not fire directly, but rather fire of to the sides to disperse sound in a non-direct manner - are far superior for rear channel duty.
A few things - may ask what size your room is?
I have noticed myself that as room size decreases, my preference for dipole/bipole surrounds increases. This is still one area I find they can contribute more than direct radiating speakers. My parents had a very narrow room, about 11 ft wide IIRC, they inherited my dipole speakers, and the difference in the apparent width of the soundfield did seem to grow. There were a few trade-offs, but overall I found the experience to be more pleasant. My last two rooms have been 18 and 20 feet wide. At such a distance the difference in radiating patterns of these speakers is effectively reduced to a point where the traditional speaker's radiating pattern isn't much smaller than that of the dipole/bipole

The reason for this is that the sound is not beamed directly toward the ear, but rather out multidirectionally in space.
This could be your problem. Proper placement is critical regardless of the speaker you use. We're not suppose to aim surround speakers at your ears..they should be off axis - except for multi channel audio sources.
SACD and DVD-A are designed and mixed with 5, direct radiating speakers in mind and with these, traditional speaker positioning where the drivers are aimed at the sweet spot is applies. Dipole/bipoles are destructive to these source.

There's really a lot of factors at play, room size, shape, personal preference and application are just a few. I'm not surprised there's different points of view regarding type of surround speakers. I've also observed there's a love/hate relationship with bipoles/dipoles. I haven't met many people who don't feel strongly one way or another.

A few companies make speakers with switch capabilities that can allow them serve as a variety of configurations - I'm a little surprised this hasn't caught on more, maybe both sides just feel so strongly about their preferences that the option presents no value to them.

Feanor
07-15-2007, 06:55 AM
Interesting points....

We're getting into an area of personal preference here - there isn't a universally accepted "Best Configuration". I'm someone who owned 2 different systems with dipoles and just couldn't force myself to like the sound - it was only when I returned to direct radiating speakers that things jived.

In the age of Dolby Pro-logic, before discrete multi-channel soundtracks were available to us, this was actually correct. Today, the surround channels are mixed differently. Ambience is still important, but the approach has changed somewhat - ambience is now achieved by "blending" the sound across several speakers, much like stereo soundstaging, rather than just using the 2 surrounds as full time ambience producers In today's modern 5.1 tracks, more and more directional sound effects are are placed at the sides and rear of the surround field. Think of any good scenes where 360 panning is used - one area the traditional direct radiating speakers excel at vs dipole/bipoles is the ability to stay true to the directional cues when necessary. A voice shouting from a specific location in the rear left will sound as if it originated in the rear left, instead of being distributed over a much larger area of the room.
...

This could be your problem. Proper placement is critical regardless of the speaker you use. We're not suppose to aim surround speakers at your ears..they should be off axis - except for multi channel audio sources. SACD and DVD-A are designed and mixed with 5, direct radiating speakers in mind and with these, traditional speaker positioning where the drivers are aimed at the sweet spot is applies. Dipole/bipoles are destructive to these source.
....


Kex provides the counter arguments above. In my own HT setup I use direct radiating to good effect and they work especially well with SACD.

I think it's more important in the direct-radiating case that the speakers be properly placed. It's also very important to have the sound level properly set, and get the speaker to ear distance right, if necessary by using DSP delay.

nightflier
07-15-2007, 02:28 PM
As someone who just replaced dipoles (actually quad-poles) with direct radiating rears, I can tell you that there is a difference and it is not just a matter of preference. This is especially the case with SACD, where the specs for the format specifically recommend identical speakers. In my opinion dipoles make the setup harder than with direct radiating speakers, because of the fact that they are so physically different from the other speakers in a typical setup.

I've helped quite a few people set up their systems, and while I agree that many people turn the level of the rear speakers too high, this is also because they select different or lesser speakers for the rear and find that no matter what the volume level that is set, they still don't sound right. I have a few demos that I like to use when demonstrating this (mostly creepy scenes with sounds coming from the rear and action films with stuff fling in from a side) and there is a marked difference when A/Bing the two types.

Of course the size of the room is a big factor. Dipoles, typically mounted on the sides, are designed to reflect off the rear walls and so the distances involved will greatly affect the speed at which the sound reaches the ears, an adjustment that not all receivers or pre/pros can do equally well. Throw in another pair of 7.1 speakers for the surround rear channels, and the consequent subwoofer crossover settings, and it all becomes very difficult to calibrate by ear - believe me, I can attribute a lot of gray hairs to the exercise. And we haven't even touched on 2nd/3rd/4th order crossovers yet, another fun little maze that I spent more time on than I care to remember.

I got so frustrated with this that there was a time that I actually considered setting up in parallel two different systems & sets of speakers for SACD and movies (yeah, until I saw the bill). Fortunately I've regained some sanity and am now actually downsizing and returning to a basic 5.1 setup that I know I can at least get my head around. I've been at it for a week now, and it's still not to my liking, but it's a whole lot better than my 7.1 with di/quadpoles setup that I never got set up properly, or at least to my liking.

Bottom line about dipoles, is that they muddy the waters and make setup more difficult, especially for the average consumer. Come to think of it, I'm pretty certain that most DIYers with dipoles have systems they are not satisfied with because the systems are not optimized, but because of what they spent on it, they continue to live with it. They just turn up the volume when they can't hear their rear speakers, or play with the receiver's numerous surround mode settings each time they need better sound. Most of the people I've set up systems for certainly had not spent the time or the money to set things up properly, and I'm going to guess that's also what others here who have become the local "audio gurus" for their friends and family have come to find out.