Originally Posted by roddir
Maybe I need to ask this: Since I am going with a Sub, what is the best center channel, powered externally, that only does what it is supposed to do?
Your 2 cents will really help!
There is no "best" because that is determined by your SPL, dispersion, room acoustics, setup compromises, cost concerns, size/weight issues and so on.
With that out of the way, once you read about specifications from Dolby--a few things to note. They specifiy that the LCR sound be the same speaker, this helps you in your quest but they will not sound the "same" because they are in different positions on the room AND they are aimed differently. The L/R speakers should be toed in or aimed at you (more or less) with the center channel being pointed straight at you in the center of the room. They will sound different, they will measure different because of room acoustics. If you want to get OCD, you can toe in L/R so their first reflection points are the same as the first reflection point of the center but most likely, that won't be optimal for your seating position. You could change your seating position to "match" those reflection points but I am assuming you need to use that room for more than audio sooo.... compromise time!
So don't expect perfection or absolute "timbre matching" because your room won't allow that to happen.
Second issue is some folks demand all the speakers being identical so they all "sound the same". Well, a speaker standing in free space (L/R) towards the corners, a center channel closer to the wall (on a cabinet, mounted to the wall etc.) and the same speakers close to or hanging on the wall in different locations of the room which colors the sound different won't "sound the same". They won't because they can't. Granted, it will be much easier if they are alll the same but that leads to another issue--compromises you will make with the speakers so they can all be the same! My center channel weighs 54 pounds and I customised my furniture to hold the beast but I don't want, don't need and sure as heck don't desire 54 pound speakers as Atmos channels above my head!
OK, I could of gone with 15 pound speakers all the way around but then I could not get the SPL and efficiency I demanded at the start. Sure, I could of gone with the 15 pounders (my wife liked that idea!) but the "no compromises" approach to get them all the same would of sunk the quest at the start.
In desperation, I went to the Dolby site and they recommended the same speakers for LCR and the same speakers for the surrounds (all surrounds should be the same and thast includes Atomos) but notice something--the "mains" or LCR should be the same, all surrounds should be the same but it does not say that ALL the speakers should be the same! Now look at dispersion requirements, the Atmos if they are not aimed at you should provide 80 by 80 degrees of dispersion or 54 X 54 degrees of dispersion if they are aimed at your listening position. Think about it, what would happen in a living room setting with 80 x 80 degrees of dispersion for LCR? Well, kiss speakers with ribbons, AMTs and waveguides that limit vertical dispersion goodbye--they won't work for Atmos. Never mind that such a huge dispersion speaker willl give you strong floor/ceiling reflections that willl smeer the sound unless you treat your floors/ceiling to absorb some of it. Digging deeper, the specs for surrounds and mains differ because they are doing different things.
Crawling out of the rabbit hole, time to do a reality check. Go to a THX/IMAX/Dolby Digital theater and physically look at the speakers behind the screen then look at the surrounds--then think about it. Building a system is all about compromise, it will never be perfect because your room will never be perfect and most people won't have acoustic screens in their rooms to place the speakers behind it in the first place. Yes, if you don't have an acoustic screen that is a compromise, the first of many in your quest.
What about subwoofers? Well, if you look at the Dolby spec, you should have subwoofers that can do 20Hz at the -6dB point minimum and should provide 115dB of SPL. Oh yeah, start with TWO subwoofers and go up from there, 3 subwoofers (look up Earl Geddes for setup) or better yet, four subwoofers and proper bass management willl get you "the best". One subwoofer is OK if it is positioned properly and it is just you that demands proer performance. If you have anyone else that will be there, start with two subs and go from there.
How much SPL do you want? Do you want it to be just like a THX theater? If so, you will need high effficency speakers--92dB one watt/one meter or higher as the minimum on AVR power. They won't be small, they won't be light weight and thy won't be cheap because anything big and heavy costs money. The best way to figure out how much SPL you need would be to get either an SPL meter or, at the minimum, a SPL app for your phone and go to a THX theater and watch a movie. You can get the actual SPL measurements to make your decision. If you want that level of SPL, build a system that will do that. If you wish it to be a touch quieter--go for 3dB lower--if you want it "half as loud" go for -10dB quieter. 3dB quieter requires half the power and 10dB quieter requires TEN times less power which gives you much greater abi8lity to fit speakers and not blow your budget. Best to know what SPL requirements you need before ever start to ponder purchasing equipment. Some speakers are unable to give you higher SPL levels no matter how much power you throw into them. There is a maximum for all audio equipment so knowing what the maximum is, matching it with your requirements weeds out the components that won't work.
A few points.
1. Matching the LCR will give you the best results but don't compromise the design or size/dispersion to force that to happen.
2. Match the surrounds/Atmos or make sure the surrounds your purchase can be used as Atmos--because speakers can last for 30 years but standards and your electronics generally won't.
3. Two subwoofers as a start if you will invite other humans to hang out with you. One is OK to get you started but plan on a second or more in the future.
4. Think of the system as three seperate sound fields, the "main" or LCR should be on axis and very accurate. The surround field will be off axis and more diffused as it attempts "3D" which is a different requirement than the main. Subwoofers are last, they should be thought of as their own animal so read up on the chaos they create when you start throwing sound waves that are over 50 feet long in a small room
They make sense once you understand acoustics, standing waves, peaks and nulls that naturally happen with looooong waves in small boxes.
5. If you have any indication that this will be a hobby you persue in the future, I would go for a more modular or "scalable" system. If the AVR has pre-amp outs, you can add amplifiers down the line when/if your needs change (a huge room nn the future) Select the subwoofer(s) that meet the frequency response you desire--don't worry about maximum SPL. Say you get a single sub that does 20Hz and that is what you want--you will improve sound quality by using 2, 3, 5 or more of them which will also increase the SPL naturally. If you pick up a sub that will meet your SPL needs with just one but does not "go low" enough, adding more subs won't make it "go lower" just louder (unless you use front loaded horns but not likely in a living room!)
A few reality hints, figure out the largest speakers you and those that live with you will put up with. Cut out cardboard boxes to give a real world idea of what size actually is in your room. Once you have the max size figured out with the speakers, do the same with the surrounds. After that, make boxes that will be the largest subwoofers you willl alllow. If you can put up with a single 8 cubic foot sub but only one--then set it aside. How large can two of them be? If something like 6 cubic feet for two or only 4 cubic feet for four subs--look at either the 6 or 4 cubic foot option and abandon the 8 cubic foot single monster. The monster most likely will not "fit" in the location of your choosing and create acoustic chaos. Better to go with the smaller sub(s) that go as low as you need and use more of them to get the SPL and distortion demands you have. Don't mix sealed and ported together when it comes to subwoofers! There is one or the other, you can't "get both" by mixing them--welcome to the world of phase, standing waves, peaks, nulls and phase related frequency cancelling--don't blame me, it is how sound waves work.
I don't recommend" anything before I know such things like SPL demands, frequency range, budget and size considerations. The simple answer would be three JBL 4722N theater speakers but they are huge, Mad Max ugly, heavy, expensive and did I mention ugly? No worries about THX reference SPL, almost any AVR willl burn your ear drums but 99.9% of the planet would not put up with their sheer size/weight so I tend to avoid any recommendations without getting the full picture. If AVS'ers have to guess, we jump to massive overkilll as a start!
In summation, go to a THX theater with some way to measure SPL and figure out what number you wish to strive for. Use cardboard boxes to determine maximum size for the LCR mains, the surrounds and the subwoofers--then we can give you accurate recommendations and budget projections. Good luck in your quest.