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What is the diff between Center, Front and Surround Spkrs

What exactly is the difference between Center, Front and Surround speakers? What are the important components that should be present in each of these? Can they be interchanged? I know you cannot with the center, but not sure, but what about others?
I think it will be helpful for a lot of newbies like me to understand the home theater concept and guide us for buying good speakers.

Thanks...
Rahul.

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for Rahul

In reality, there is no difference. In reality, having the identical same speaker at all positions is ideal. In reality, a vertical speaker is always superior to a horizontal speaker, unless you like watching your movies sideways, lying down.

Having the same speaker at all positions allows for best matching, in timbre, sensitivity, phase, x-over points, yada yada...

So... what's up with the very different looking speakers in any package? The horizontal center is designed that way to more easily fit above or below a display. The smaller surround speakers allow for easier placement, especially to be mounted high enough (well, at least IMO).

Sure, you COULD interchange the speakers. The biggest ones are usually up front since most audio is coming from there. The biggest compromise in a typical package is the center speaker due to horizontal M-T-M layout that provides very poor off-axis response. Ok, you might spared if within 10 degrees of dispersion, maybe even up to 20. However, a typical upright tower or bookshelf gives you about 60 degrees of dispersion. This is quite desired for a wide viewing area. (You will often see me recommending 5 or 6 identical bookshelves to noobies). See, you often can get a superior center speaker, and for less cost, by simply by using an upright bookshelf for center speaker. Problems are 1) do you have space? 2) does it look funny to you?

While a vertical cabinet is also superior, at least a few companies out there put the tweeter on TOP of the mid, such as B&W, Revel, AV123. KEF uses a coaxial setup, and this is just as good, with the added bonus of being not as tall (since no extra space for tweeter is required).

Hmm.. good speakers.... consist of 3 main things: 1) Cabinet 2) Cross-over 3) Drivers. And probably in order of importance as well. You think, huh, the cabinet is most important? Yes. Its hard to find good ones. Actually, all speakers suffer from cabinet resonance. Yes, you can actually hear them, believe it or not, of course you may not be able to distinguish them from the room, or drivers, or x-over, but the total sum of what you hear is distinguishably affected.

There was a recent case of a guy who made a bunch of DIY treatments for his dedicated HT. He is still getting some "bloom" from piano recordings, and its very possible that this bloom is from cabinet resonance. And these are VERY nice Paradigm speakers we are talking about. Pretty much all of us suffer from it.

There are only a couple of speakers that make sure that the existing cabinet resonances are outside of the human hearing range, and those are made be B&W, and they cost as much as an entry/midrange car.

The cross-over. Its the device that gets your drivers acting beautifully in ensemble. If you think about it, a small metal tweeter is going to be pretty different sounding than a polypropelene midrange driver. A lot of R&D goes into this piece, and hopefully a lot of this research is aimed at getting them in phase. People say when you listen to a speaker, you are listening to its cross-over. That's how important it is.

The actual drivers. The most obvious thing one would is linearity. Depending on how linear any driver is, and to which freq points they can keep this linearity up... will very much affect how the x-over is designed. As with cabinets, the actual drivers can suffer from resonances, and this is called "cone resonance".

So, with the above in mind, a great speaker will have these attributes:

- linearity thru much of the human hearing range
- ability to maintain such linearity off-axis, and the better speakers maintain such lineaerity at greater angles

Ah, yes, almost forgot. The acoustics of your room, along with the placement of any speaker in such room, is just as important (IMO) as the speakers chosen. The Absolute Key of what you will hear is the:

Interaction of speakers within any given room. Yes, this is affected by their placement, the room's acoustics, even your listening position. I know this is over everyone's heads, and probably over-kill, but yep... this is what it boils down to.

Im sure that's just the tip of the iceberg. Any other questions?

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What do I look for?

Thanks for the response...
I read this article on Wikipedia for explanation of some of the terms that you used. I'm a newbie so I had too, sorry..
http://en.wikipedia.org/wiki/Loudspeaker

So when I go to the store to review speakers and take one in my hand to look at, what should I look for in them? I know I should let my ears do the talking, I'm talking about physically.

Thanks...

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the singularly most important thing

for me to check out in person is the cabinet. The "knuckle rap test". There are some that are SOOO flimsy, and some that are so "dead" that they could break my hand if I hit them hard enough. Cabinet construction is pretty much ALWAYS a compromise with any typically priced speaker. MDF ain't cheap. Lift the speaker to see how massive it is.

That would be #1 for me.

Other stuff.. sure, does it look good? I'd just look at the drivers, perhaps note how big the dust cap is, or how thick the cone surrounds are, mostly out of curiousity, not that this stuff would help me know anything. Or if there are 5-way binding posts. There's stuff inside the speaker you can't see, being the types of capacitors used, or having any idea how much R&D went into the speaker, etc.

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2 way or 3 Way speakers?

I read that 3 way speakers will sound good than 2 way. True?

Thanks...

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speakers

Generally a 3 way speaker will have better bass and a clearer midrange because it will have a dedicated midrange driver only playing midrange (voice range) sounds. Vocals will be clearer. The bass is usually better also because of a dedicated bass driver and overall the speaker will usually handle more power so if you're in a good sized room this will work better than a 2 way.

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2 vs 3

I appreciate what Jason has to say. However, Rahul, its not so cut and dry like that. Like with everything else in audio, and life for that matter, its all about the implementation. Its true that a 3-way allows a dedicated mid driver, but if those 2-ways were used as a satellites in conjunction with subwoofer(s), you in fact have a 3-way system then.

There are some that might have the opinion that the less x-over's the better. Less chance of screwing up they think. Not necessarily my opinion, although my stereo speakers are only 2-way, yet go down to 24 hz @ -3db. If you look at certain well-respected brands such as B&W or Dynaudio, they can sometimes get extremely matching drivers, allowing for 1st order x-overs. This is the simplest type of x-over, and again proponents think that "less x-over is more"... sorta...(that's sort of an oxymoron, I know).

Trust me, there are many 2-way speakers that I rather have than many 3-way speakers. You can have a perfectly crappy 3-way, or an amazing 2-way. There is also the 2.5 way, which does NOT have a dedicated mid driver, but is more like a 2-way with one extra driver handling bass only.

For those who like to listen to either serious volumes, or very bass-rich music such as pipe organ, a dedicated mid driver can and does help a lot. The very difficult excursions from the bass being inflicted on the driver on a 2-way will muddle up the midrange as jason says.

I don't know what else to say. Its just not that simple to state that 3-ways are better. That's like saying Class A amplification is always better than Class H, or that a 15" subwoofer is always better than a 13" subwoofer. Its all about the design, components, implementation, etc.

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The magic numbers!

What are good numbers for all these speakers? frequencies, Impedance, etc...just getting things cleared.
You have speakers with 24hz@+-3db, which is pretty good, considering normal humans can hear sound ranging 20hz - 16000hz.
Thanks...

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there are none.

There are no such things as magic numbers, AFAIK. Frequency response? Most numbers have no problem getting to, or past, the upper limit of human hearing. For the lower end, typical roll-off starts for many speakers anywhere, perhaps at the 40-80 hz area. Some really tiny speakers, perhaps even higher. You will get these #s often as something like 45hz-20khz @ +/- 3db. Well, how much does that really tell you? (Assuming if the spec is even honest. And maybe such a spec was had after tremendous tweaking of the room or electronics so they can fudge #s?). Anyways, lets say its honest. Even then, +/- 3db technically represents a 6db swing. For instance, you could be -3db at 80hz, and then +3db at 81hz. So, even a pretty funky looking graph might still be within the tolerance of +/- 3db. THEN, what about at say listening at a 20 degree angle? How well can it maintain performace? What frequencies are getting short-changed, how many of them, how badly will this conspire for much less than linear response.

What you want are respected, non-affiliated, 3rd party measurements. People often use the various periodicals to find them, or sometimes online as well. The hard part is understanding the graphs. Especially those with time-decay, or "waterfalls". Even tougher is to combine all the #s for the big picture.

Rahul, are you a fan of any sport? Let's take baseball, for instance, anyways. A lot of people still think about an out-dated and way over-rated statistic for a baseball batter, and its called "batting average". Yet, this batting average cannot account for power, nor patience at the plate (base on balls, etc, though striking out is over-rated for hitters, its a bigger factor of a pitcher's performance instead). Let alone any defensive abilities. You want to know the whole picture before you give that guy 10 million a year.

So, some people can and do fall in love with any particular graph, but sometimes they miss the forest for the trees. There have been baseball players, that in my opinion totally suck, but people they think they are good because their BA is decent. One is local to me, and people do not realize how bad the other stats are on this player, ie baserunning ability, complete lack of any power, weak defensive skills, etc.

There are no magic #s. As far as impedance, this is not a compromise in theory, unless your amp cannot handle the load. And this is not even talking about SPL with any given sensitivity or given distance from speakers. To increase output by 3db normally means double the power required. ALSO, the power required increases exponentially with distance from speakers.

Sensitivity is usually rated at 1 meter distance, at 1 watt.

I have a speaker that has a planar-magnetic tweeter and mid driver made by Bohlender-Graebener, with metal cone woofers that are small. The sensitivity is average, and the power handling is average, at least by the specs. I've also learned since my purchase that this speaker is at its best when vertical, even when the tweeter is mounted higher in the horizontal position. Baffled at first (pun intended), it is due to the horizontal nature of the actual tweeter. Crazy, eh? Specific performance capabilities can be very dependent on physical arrangement of anything from waveguides to phase diffusers or lens.

However, this speaker of mine suffers in off-axis response, and IMO, cannot handle a whole lot of power. I could perhaps predict these circumstances from what I know of speaker technology, and that the speaker has a rather small enclosure, with small drivers. However, there's not much in the "specs" that would help me predict these issues, otherwise, AFAIK.

How often do you ever find specs or graphs that show exactly how any speaker suffers in compression with greater power? Perhaps never for you.

Back to your frequency specs... lets take a couple of subs for example Here are your "freq specs":

22hz @ -3 dB. 1000w RMS, 2000w dynamic
18 Hz @ -3db. 2500w, RMS short-term

Hm, just a 4hz difference, for TWICE the price? Wouldn't seem worth it, would it now...
Well, the deeper sub also has specs such as 20-86 hz @ +/- 1.5 db. It also handles MUCH greater output before suffering serious compression. It also suffers from less harmonic distortion throughout its operating range. How do I know? By using Google a lot, hehe. I just bought my first AV magazine ever this week. Haven't perused it yet, but I do hope there are some cool analytical tests in there somewhere or other...

Are you getting my point? If you need another analogy, take cars for example. Some differing cars might have a healthy amount of power, lets say 250HP for example? Well, that power could be useless unless the suspension is good, or you only like driving in a straight line. What about your safety when using this 250HP, ie stability-traction control, crash ratings, ABS, airbags, etc. What about the gear ratios so that you can actually get off the line quickly. What about heated seats?! You might see why some similary "spec'd" cars might have differing price tags. (Sure, often due to luxuries, but not always). Also, regarding power, 250 HP will not be very impressive in a tractor-trailer rig, but will be very, very impressive in a light-weight fiberglass 2-seat roadster. This is why power ratings on a speaker is just one tree of the forest. If it is insensitive, then more power is required (and hopefully it knows what to do with that power without a lot of compression, port-chuffing, bottoming-out, whatever else happens to wimpier speakers).

That was really long. Anyways, I am not the one to answer this question. To the best of my knowledge, there are no magic numbers. To the best of my knowledge, very very very few people know how to understand the phalanx of measurements of any given speaker and judge its performance. And even between those few that can, they often disagree anyways.

-jostenmeat

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Equally fine speakers would be a nice idea, but I must part

from jostenmeat's prescription because of what is the typical balance of info fed to the speaker set by the receiver.

The one speaker that should not be chintzed on is the center channel as it is the one there to anchor the dialog close by the screen. Typically, the center channel speaker if fed perhaps 60% plus of the total audio.

In a surround setup is does most of the work. It is a whole different world from old time stereo fro music which is most highly concerned with the best possible front L&R for accuracy & musicality. So, introducing a center & giving it the most part of the audio signal is an entirely different world.

Sure, I have center with my living room TV 5.1 surround setup but avoid a center for my music listening in old fashioned glorious stereo. My stereo for music might possibly be aided by adding a good sub woofer, but I wouldn't even entertain the thought of introducing a center there.

The big surround fans may be so enchanted with the Star Wars type special effects that they would regard the huge slam impact factor of a powerful sub woofer to be their idea of the most important speaker in their surround setup.

Yes, compared with stereo, bringing in a center channel substantially downgrades the importance of the front L&R because the majority of audio info being fed them is primarily diverted to the center channel instead.

But I think everyone should approach getting speakers as very important & worthy of perhaps saving up for them as you will have decent speakers for a lot longer than the individual electronics of receiver or TV that will get replaced sooner. Speakers just basically don't wear out of become very obsolete. The electronics sound pretty much alike; speaker brands have their own sound characteristics & are the source of most all the sound differences. Fortunately one can start with just two well selected speakers & add on as time allows more budget. (Yes, usually by sticking with the same make & model line of speaker - & they don't have to cost so much as to be unaffordable.)

Hang in there as it is not incredibly hard to understand - not really rocket science.

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Hanging in there!

I've learned a lot in past few weeks since I posted this question on CNET. Not scared anymore hearing about all those speaker numbers Happy

So far I'm researching on what speaker system will be good for my living room(apartment,15x20, should not disturb neighbors!). As much as I would like to have those tower speakers(my wife says she will surely kill me if I get those),I cannot have those. So I've to be content on a smaller/compact speaker size that wife will approve off(size, budget and color!...sniff sniff...)

I'm going to keep on looking. Few shortlisted so far are Mirage, Infinity, Onkyo...Sure that this list will grow...Will then go and hear them out and then decide.
Wife has tabs on our stimulus check, so I have to think of something else. Oh, I've a birthday coming!!! Wink

We are also planning on getting a house so this picture will change drastically. House=>Basement=>Tower speakers...hmmmmmmm

Will keep you posted...
Thanks..

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Hang in there

Im glad you're not afraid of speaker #s. A lot of them are wishy washy anyways.

Don't let Bill's nebulous post confuse you. I don't know if you take his advice as spending more on the center, or more on stereo mains, but the fact still remains that a VERTICAL BOOKSHELF IS A SUPERIOR DESIGN TO A HORIZONTAL MTM SPEAKER. Not only that, it often costs less (not more).

His mis-match speak is nebulous at best to me. At worst, its simply bad, wrong advice. Period.

If you ever do towers, try to get matching front 3 towers.

Everyone gets some large cabinet, credenza, but I personally find those very overwhelming to the room. Now that I have an audio rack to my SIDE, it looks very clean up front. No annoying lights either.

With such a setup you can have your cake and eat it too, in audio terms. Now, I don't expect the majority to agree with me here, but, IMO:

-it looks better, cleaner
-costs less
-allows better performance in BOTH video (less direct ambient light) and audio (ideal placement and configuration chosen).

Did I mention that it costs less?

Please take a look at this picture of B&W home theater setup with a horizontal speaker. At least the tweeter is top mounted here, but this is just ridiculous. The center speaker should definitely be a matching tower. Why do they show the badly chosen horiz center? Its called MARKETING... (center channels often cost a lot more for what your getting in performance, compared to other speakers)...

good luck.

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I forgot to post that B&W pic

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