Originally Posted by Jakeshields
Sounds like gibberish written by the marketing team. It doesn't have anything to do with reality. A 3-way widens the sweet spot compared to a 2-way if both have woofers larger ~5.5", because it reduces inconsistencies in the polar response. If anything it will make the speaker sound "bigger" because more of the reflected sound will match the direct sound.
As with all things, as you go deeper down the rabbit hole--you get a ton of information but both the bood kind and the bad kind. To save time and provide clarity, I went to Dolby's site and they give very basic specifications about "surround" and "Atmos" speakers to assist in the quest. Throw in a little logic and it actually makes sense. Dolby states that the surround AND Atmos speakers should be either the same speaker or "related" to each other to create the sound field correctly. Realistically, since speakers sound different at different locations, they can not and will not "sound the same" because of diffirent locations cause different reflections which color the sound to the room. They then give dispersion specs, if the speakers are not aimed at you (Atmos in ceilings pointing straight down) they need to have a dispersion angle of 80 X 80 degrees--if they are aimed at MLP, you can dut that down to 54 x 54 degrees of dispersion.
Using simple logic and the broad overview that Dolby provides, the "surround field" and your LCR channels (or mains) have different jobs so using the same speakers everywhere can be good or bad depending on the room acoustics, listening distances from the speakers and so on. For example, in my room my LCR use 90 x 45 degree waveguides (horns) for the upper mids/treble so I avoid floor and ceiling bounce which blurs the sound and makes a mess of the spoken word. According to Dolby, my "mains" would not work well as surrounds and considering I have a smallish/medium room I would agree. Granted, haning up 54 pound speakers for surrounds would last until the divorce was final but you get the idea.
My wife is pretty cool about my hobby but if you take my speakers apart, there will be plenty of wood to make a coffin--throwing that out there. Considering my room size, the side surrounds will be around 2 meters or 7 feet away so I need wide dispersion so all the speakers can "blend" at such a short distance. Would a three way have wider dispersion than a 2 way? That depends on the design of the speaker and remember, the taller the speaker and the more drivers it has demands a longer distance away from it to "blend" properly.
The correct dispersion of the speaker reallly does not depend on how many "ways" it has, it depends on the speaker driver size and what the crossover points are to prevent beaming. For example, if I wanted an 80 x 80 degree dispersion--I can get that from Danley Sound Labs and the design is a 12 inch coaxial in a waveguide. I think they cross over the compression tweeter at 1,300 Hz to get that dispersion correct (something like that) You can get 15 inch coaxials but the issue is crossing them at 1,000 Hz to prevent beaming and getting a massive compression driver that can do that squeezed into the small theading allowed (and loading the driver that low with such a small waveguide) If you went with something like the outstanding JBL M2, it has a 15 inch woofer crossing to a massive compression driver/horn at a very low 680 Hz--but you PAY for that!
I learned about dispersion the hard way, PA systems back in the 90's. Most 15 inch 2-ways sound terrible off-axis, most 15 inch 3-ways sounded better but then again, a very few 15 inch 2-ways sounded better than 15 inch 3-ways. PA systems have a few extra specs that consumer audio generally does not worry about, things like durability, size/weight since you have to lug it around and very high SPL levels. The reason 15 inch 2 ways dominated back in the day was they are very, very durable, they are lighter/smaller than 3 ways and they USUALLY cost less than 3 ways until the really good ones cost more than 3 ways. The difference became obvious on the spec sheets, the great sounding 15" two ways crossed over to massive compression drivers on big horns at 1,200 Hz or lower which cost big bucks. A cheaper way to do it was a 15 inch 3-way to avoid the $400 compression drivers and big horns but it was larger/heavier. I used 15 inch 3-ways for that reason. After all, a 70 pound 3-way cabinet was much easier to carry around than something like a JBL 4722N (15" two way) at around 150 pounds. I went with a 15" 3-way and bi-amped it to protect the mids from feedback destruction with a limiter on the mid/high part at 200 watts. The woofers could handle the 800 watts of feedback but the mids could not (I purchased the things at 65% off because of blown mids from feedback and fixed them
For me and my room, listening distances and the fact that I'll keep the speakers longer than I'll live in my present house--I am going coaxials. They are "two-way" but very wide dispersion by design. My LCR is around 11 feet away but the side surrounds at the end most seats on the couch are at 5 feet so I have a choice of small 2/3 way speakers to "blend" properly or a larger coaxial. I am going coax as it gives the performance required, has a smaller "face" and can hammer out over 110dB easily be it a 6.5, 8, 10 or 12 inch coax. I want a 10 inch coax, my wife wants a Bose jewel cube so we comprmosed on a 6.5 inch coax in a box of 1/2 a cubic foot or less. To calm my OCD and to keep with Dolby suggestions, all my surrounds be they side, rear, Atmos elevation or (furture) Atmos ceiling speakers will use the same compression driver with the same crossover frequency and the same "motor" (magnet, voice coil, spider and Xmax) Basically, 6.5 inch coax for side surrounds and 10 inch coax for in ceiling Atmos running infinite baffle as the limits. Since the compression driver has to be so large to handle the 1,500 Hz crossover point--it will give up response over 16 to 17 KHz--because physics. Then again, I am a human adult so smooth response out to 16 KHz is about all I need and it IS a surround--off axis will kill off response over 10 KHz because--physics. You compromise in the right spots where it don't matter and press on!
Now if money was no object, if I had a larger room and I was single--you can get a "three-way coaxial" in a way--but better! I think the technical term is a "multi-entrant horn", basically, woofers/mids/tweeters all sharing the same horn with correct time delays and phase so it acts like a point source. The smallest/lightest one I know of is the Danley SM60F with a 5" coaxial and two 8" woofers tucked inside the horn (you'll see the holes which the drivers vent through to keep the time alignment and phase correct) They have a 60 x 60 dispersion and it IS a "3-way" that would meet Dolby specs for surrounds if they are aimed at MLP. Weight at 50 pounds is not too bad (for large rooms) but the size and $2,500 each price might slow you down! However, if you want a point source "3-way" that is the way to go. In reality, I'd get their SM100F which is an 8" coaxial loaded in a large flared waveguide/horn and a 15" to provide the low wend. It has a 110 degree dispersion which would rock for surrounds in large rooms or the occasional barn.
Weight is around 122 pounds each, not to mention the size/cost of them but if you need a "3-way" that has over 100 degrees of dispersion and 128dB of output--you are set!
Realistically, since you are using a subwoofer for HT systems--the "2-way" is actually a "3-way" if that helps. If you journey deep down the rabbit hole to the land of theory--and you want enough SPL to cause massive hearing damage--then technically, the total system should be a "4-way". In theory, a driver should never be driven beyond a "decade" or say the subwoofer does 8 Hz to 80 Hz, the woofer does 80 Hz to 800 Hz, the mid does 800 Hz to 8 KHz and the tweeter does 8 KHz to 20KHz +. IF you choose to go deep in the weeds, that is what you will find and some people on this plenet build speakers that do just that--I am not one of them! I don't have a huge room laying around filled with acoustic panels and a breaking bad pallet of money so compromises that won't be an issue with the SPL, distance and room acoustics I have are key. Sure, an 8 or 10" coaxial would be "better" for my side surrounds but then again, so would a Danley SM100F--so I go for the 6.5 inch because in reality, I don't "need" more than what it can do--just one of those OCD want things. In the future if I need more output than the 112 to 115dB the 6.5 can do, then I'll go to the tens to get me there. Put the old 12.5 pound 6.5 inch coaxials in the rear deck of my car or have computer desk speakers that will make my ears bleed--always a use for small speakers!
In summation, for surround speakers it matters more about the dispersion, the off-axis sound quality, iff the SPL they provide at lower distortion meets your needs, not how many "ways" it has. If you are worried about "future proofing" something, your existing system won't do an actual 2 or 3 row 12 to 20 seat theater anway so take stock in what you have and go in the best direction. My mains/center will do reference levels and more at 20 feet--but not 50 feet but I don't lose sleep over it. I'm at 11 feet and unless I inherit a castle or something, beyond 20 feet is not in my future.
So relax, use whichever one you like, you are paying for it so if the 2 way does what you need--go for that. If the 3 way is what you want--then you have to make that determination for yourself. Good question though, the answer is 3 ways are not inherently better than 2 ways just as 3 ways don't always cost more than 2 ways (JBL M2 cough, cough) The design is critical, your needs help determine which would be better/worse/no difference and the room is always messing up those pretty frequency response charts. Give Dolby a good once over on their site, they tend to be really good at helping you along with specs and education about surround systems, their proper deisgn, setup and calibration. They actually do know a few things about surround!
Give it a good read, pay attention to your room and make an informed decision about what would work best for you, your budget, your size limits and budget limits and go. Enjoy the read and good luck with your build.