Surrounds vs. bookshelf - any difference?

[EddieG]

For home theater is there a difference between bookshelf speakers and surrounds? I would think not, but doing some searching I found references to speakers that are marketed as "surrounds", such as Infinity Beta es250.

Thanks!

 

[phlakvest]

Surrounds like the es250's you linked are called di-pole speakers. As opposed to bi-pole like bookshelves.

They are designed to radiate the sound, and be less direct than bi-pole's.

read the section Rear speaker placement, dipole vs. direct radiating.
in this article for more details about which to use where.
http://www.audioholics.com/tweaks/speaker-setup-guidelines/loudspeaker-placement-guide

 

[jliedeka]

If the speakers are unipolar (drivers on one face only), there's no difference. The thing you may need to look at is the rated frequency response. Something marketed as a surround may not provide as much bass as something marketed as a bookshelf. You'd probably want to pair small speakers with a sub anyway.

Of course, there are bipole/dipole type surrounds that are designed to disperse sound rather than act as a point source. There's no law that says you couldn't use them in the front but that wouldn't be my cup of tea.

Jim

 

[no. 5]

For home theater is there a difference between bookshelf speakers and surrounds?

Sort of; any bookshelf can be a surround, but "surrounds" often can only be used in that capacity. The reason being "surrounds" are often dipoles (but not really true dipoles), and in this case, it does really awful things to the sound quality.

The explanation to why these 'dipole' speakers are marketed as surrounds comes from the notion that surrounds should not be localizable, but really, localization is often essential to the effects the surrounds are creating.

Surrounds like the es250's you linked are called di-pole speakers.

For what it's worth, the ES250's actually have a switch on the back that allows the user select their operation; dipole, bipole or monopole.

 

[Clearwave]

For home theater is there a difference between bookshelf speakers and surrounds? I would think not, but doing some searching I found references to speakers that are marketed as "surrounds", such as Infinity Beta es250.

Thanks!

I'd look into how the speaker is intended to be set up in the room. For example, is it a wall mount speaker with less baffle step compensation or intended to be placed several feet away from a room boundary.

 

[fredk]

but really, localization is often essential to the effects the surrounds are creating.

I don't think that is quite correct.

The idea of surround sound is to mimic what we hear in large spaces. Often, as much as 1/2 of what we hear is actually reflected sound, which is not localized/directional. It is sound that is reflected from a widely dispersed area and delayed from the original souce (depending on distance and what it is reflected off), that queues us as to what our surrounding are.

A good example of this would be the scene in Casino Royale where Bond steps out of the lobby of the casino onto the street. On my system, the traffic sound was comming from all around (front, back, sides, while the dialog was comming from in front of me. It sounded like I was sitting in the middle of the street, watching the scene.

In order to achieve this illusion, the surrounds need to distribute the sound they produce widely in the room and to blend in transparently with the sound comming from the mains (some of the traffic sounds would have been coming from these speakers as well).

Surrounds with drivers firing in multiple directions seem to do a better job of this.

 

[brendy]

However with movies sometimes the director wants the sound to come from a particular location in the room.

 

[jostenmeat]

This is something that Ethan Winer said recently. This portion has more to do with higher surround mounting. However, the pdf he linked does talk about dipole vs monopole.

"That's old school, and is derived from movie theaters years ago when the rear channel was mono. The idea was to put the rear speaker(s) up high so the sound bounces around the room before it reaches your ears to create more ambience that also has some stereo width. But what works in a large theater doesn't necessarily work in a home-sized room. More to the point, these days movies have all the needed ambience already embedded in the soundtracks. This PDF contains a more modern guideline from NARAS (National Academy of Recording Arts & Sciences), the technical vision of the Grammys:

http://www.grammy.com/pdfs/recording_academy/producers_and_engineers/5_1_rec.pdf

The emphasis is on rooms used to mix movies, but the same applies to rooms you watch in.

--Ethan"

Start reading at the bottom of pg 28 for the discussion on dipoles, and their poor localization. Its short, however.

One of the first rules stated in the intro seems to be the use of monopoles when mixing. Its underlined on page 29 as well. Of course, even if dipoles are bad in the mixing room due to phase anomalies, dependence on boundaries, and generally poorer bass response, I don't think that must necessarily mean they are bad in any given room with any particular consumer's wishes. I'm sure YMMV. Me? I use monopoles.

Other little things they say about mixing include having the same surround height as the mains, ideally have all the speakers equidistant from listener, with a rather high ceiling, at least two sidewalls treated acoustically, bass trapping, yada yada yada yada . . .

 

[no. 5]

I don't think that is quite correct.

Remember I said "often" not "always". Because sometimes the director intends for a sound to be localized, if briefly.

The idea of surround sound is to mimic what we hear in large spaces. Often, as much as 1/2 of what we hear is actually reflected sound, which is not localized/directional. It is sound that is reflected from a widely dispersed area and delayed from the original souce (depending on distance and what it is reflected off), that queues us as to what our surrounding are.

A good example of this would be the scene in Casino Royale where Bond steps out of the lobby of the casino onto the street. On my system, the traffic sound was comming from all around (front, back, sides, while the dialog was comming from in front of me. It sounded like I was sitting in the middle of the street, watching the scene.

In order to achieve this illusion, the surrounds need to distribute the sound they produce widely in the room and to blend in transparently with the sound comming from the mains (some of the traffic sounds would have been coming from these speakers as well).

Surrounds with drivers firing in multiple directions seem to do a better job of this.

Surround sound can mimic the 'sound' of any space, but one must remember that the reflections in a small room are not like those of a larger one; a defuse sound field (or like you said "reflected sound, which is not localized/directional"), as it exists in a large space, does not exist in a (relatively) small room. The distances are too small, the delays are too short and the reflections are higher in level.

Therefore, the sense of envelopment created by a mulitichannel soundtrack is done by the recording engineer, it is up to them to provide appropriately delayed, level reduced sounds in the appropriate channels to create the illusion, and that illusion can mostly mask the reflections from the room. The direct sound from the surround channels is, in effect, standing in for the reflections that would happen in the space that the filmmaker has put on the screen, to paraphrase Floyd Toole; the surround illusion can be created at will, without any help from the room.

Speakers need to do certain things, and be in certain places to excel when producing the desired effect. Certain places because the angle a sound arrives from is important with regard to envelopment, and do certain things because directivity is important to sound quality, the kind of 'dipoles' marketed as surrounds have directivity issues. It is noteworthy that the recommendation for dipole surrounds comes from a time when there was only a mono surround channel.

If I seem overly critical, remember that I am discussing the technical merits two methods, the enjoyment received from either is not in question.