A week old thread, but I'll add something since I do currently own the SVS Ultra bookshelfs and had owned the KEF LS50s for a good 4 months. I've also done a lot of A/B testing between them in my own room, at my own space, on the volume I like.
I don't want this post to be super long so I'll try and keep it short;
I'll be extremely frank here, the tonality between the Ultra and LS50 are actually pretty damn close. Until the point where I could use one PEQ curve between them and they wouldn't sound too obviously different. It's only noticeable on some content and if I focus on the differences. Since movies are mated with a sub(s), I have my subs blend very seamlessly with either pair where it's difficult to tell the difference between Ultra and LS50 on the low-end, hell I think it's damn near impossible.
The Ultra does have a slight bit more forward presentation on the mids, I use the Ultra Center as my center for multi-channel movies so it applies generally to the bookshelf also. But on stereo content, the mids on the Ultras a little more in my face than the LS50. Neither is bad, it's just a preference thing. I personally like the Ultras more in this regard.
Tweeter wise, not much to split between them to be honest. On paper and technically speaking, the Ultras would sound brighter and more forward. But I found it wasn't the case in my room at least. The LS50 may or may not have more detail, but that's something movie content cannot really show. I'll get back to this with music...
This is the only genre where I can differentiate them noticeably and even then, it's not very significant. In a 2.0 music only setup, the Ultras low-end is the definite winner in my books. It just hits harder, quicker, more accurate and it's just so, sooo clean. The LS50 lacks in this space and often times, I can hear a feint but noticeable reverb between the lowest octaves of a male voice and the mid-bass.
The tweeter, welp the KEF wins in this area. I'm fine with the Ultra's tweeter for movies, but on music... they too can sound a little too bright and yes I know what the hell bright is considering the Prime bookshelfs were my main drivers before either of these. There can be cases of sibilance on the Ultras that you know can only be remedied with a DSP to a certain extent.
The LS50 has a very detailed, smooth top end yet it doesn't lack that expressive energy that is an absolutely must have criteria in my book. I hate plain, dull tweeters that for the sake of not sounding harsh, becomes overly veiled.
Now I play A LOT of games. And games these days has gotten increasingly complex in how dynamic they can sound on the fly. Unlike a movie or a song, many parts of a game's aural experience derives proceduraly on the fly.
Both the Ultras and LS50 does fantastically well in games. The most important area to a game (audio wise) is accuracy of sound directionality. If I were to play a game in plain stereo, the LS50 would win every time in terms of the soundstage. I mentioned it earlier, its top end is just beautifully detailed and that translates into a very wide and deep gaping soundstage that effects are coming from areas from my wall and not just the screen. As an example, it's eerie to hear a train coming from the far left side of my wall and it hasn't even arrived on my screen yet.
That said, the Ultras aren't too far back either. They do have a wide soundstage as well, but it lacks some depth and instead has more width. But at the same time, the bass on the Ultras are just so forceful and fun to listen to that it makes the LS50 feel meek in comparison. I love how the Ultras always punch me in the gut, while the LS50s are more... "eh, here's some bass, I'll massage you with it."
The tldr though; I love both pair of speakers. I sold the LS50s because the Ultras to my ears are the best all-rounder (which was what I'm looking for) while the KEF LS50 is a little more focused on certain genres.
Hope that helps you out, even if it's a week old thread.
PS: One other thing, if you can get 3x LS50s and make them your LCR instead of mating the center channel to a Q600 (I loathe the Q series btw), that would be preferable instead. You can use the Q series speakers for surround if you want. But if you're set on getting a pair of LS50s, try getting a single LS50 for center. I'm sure you'll have jaw drop syndrome from the seamless blending on the front stage of your audio setup.
P/S 2: Yes. you can put the LS50 horizontally and there wouldn't be any dispersion issue (which is what I did). I know some crazy LS50 lovers actually bought 7 x LS50s just to have a seamless 7.1 setup.
Last edited by Ben Tan; 03-14-2017 at 04:16 AM.