ESL and horns are pretty near on the opposite ends of the spectrum IMO. I would "guess" that if you like the Quads you won't like the Uno or at least not nearly as much. I've heard both and that's my "opinion". Good luck.
Avantgarde sounds very good too but their presentation is very different than QUADs. Horn speakers are very details and it will expose any weakness from your equipment so you must use very good equipments in the whole signal chain. By the way, horn speakers does not produce as much depth in terms of sound stage as other speakers, including ESL. You really should audition the Avantgarde before you spend the money. The good thing is that Avantgarde and QUAD hold their value very well so you can take some risk, just more work to pack and ship the pair if you end up not liking the sound.
Definitely take the time to listen to the Unos...if properly set up and driven, they will do things that no Quad (excellent though they may be) could ever dream of. If you listen to a lot of RnR, electric blues, etc. which benefit from immediacy & macrodynamics, you will likely prefer the Unos.
Either way, you'll have added a vital chapter to your audio journey.
Another consideration is: How much power do you intend to drive them with? The Avantgardes are extremely efficient 100db/1w/1m, and can be driven by low powered amps(ie: SETs) to loud levels. As mentioned: They will act as a magnifying lens toward any shortcomings in the rest of the system. Personally I consider that a plus, since any system shortcoming will distract, color or otherwise hinder my musical experience anyway(even if subliminally). Some prefer to remain in the dark about that(ignorance CAN be bliss). Are Quads excellent speakers? Absolutely!! The Unos have a much wider dynamic range, can play cleanly at VERY low or VERY high SPLs(unlike the Quads), but also as mentioned: horns are never very good at depth of sound stage, or pinpoint imaging. They aren't as sensitive to room placement either. If you enjoy the bottom octave of bass(40 to 20hz), both will need a subwoofer. Avantgarde has a massive, matching horn available, IF you have the room. DO take the time to listen to them. Hopefully- the system(including cables) and room acoustics the owner has will do them justice. Then it's a matter of whether their presentation is your cup of tea. If you enjoy actual concert SPLs, you'll like the UNOs. Chances are good that the room the Quads were auditioned in was treated well acoustically. That might give them an advantage, if the home you will listen to the UNOs in is otherwise. Prepare to do some acoustic treatment in your home, whichever you go with. Much of the above has already been stated. I just wanted to encourage you to give them a listen. I've been a horn-hater for over twenty years. New horn technology has modified my stance, given the wide dynamic range of live music/horn systems. I'm still listening to actively bi-amped planars though(I'm addicted to the sound staging).
So far nobody has mentioned this - but you need to consider your listening room. Both speakers are very sensitive to listening rooms but for different reasons.
You need to sit ideally 3m (9ft) away from the Avantgardes. You can get away with 2m (6ft) but if you get any closer the sound will be incoherent. This is because the horns are spaced very wide apart. You will be able to hear each horn as a seperate source. Also, the woofer module is crossed over at 200Hz, very high for a woofer, and high enough to be directional. Because you are sitting so far from the speaker, you will need to place them far apart otherwise your soundstage will be too narrow.
I have heard the Avantgardes in two systems. I was not impressed with the first (listening room too small) but I was impressed with the second. I agree that the Avantgardes are VERY sensitive to quality amplification. They will sound terrible if you use a second rate amp to drive them.
Forget the Avantgardes if your listening room is small.
The Quads are a different proposition. Being a dipole, the speakers can be placed against the side wall with little ill effect. However, you have to deal with the wave from the back of the speaker. You can't have it too close to the rear wall, they should be pulled out into the room. You can't have glass on the rear wall.
The sound of the speakers is completely different. The Quads are exceedingly coherent, have a beautiful midrange, and have fantastic imaging. It is let down by its lack of extension on both frequency extremes. Also, depending on your room - the Quads may not achieve sufficient SPL's to keep you happy.
The Avantgardes have a much more dynamic sound. In fact, incredible dynamics. You will rarely hear better. But if you don't use the right amps, they can sound honky. The sound is nowhere as coherent as the Quads, and the imaging is so-so.
Both speakers have interesting compromises but sound fantastic in different ways. It is up to your listening preferences and which compromises you are prepared to put up with.
Your room is certainly big enough for the Unos (sit 12' away for best results).
Must correct Amfibius' post above - the sub crossover is adjustable on the Avantgardes, and mine is usually set at 140 Hz. Also, Rodman's statement that a separate sub is needed is just flat wrong - these are emphatically full-range speakers. Plus, the level is adjustable...they are flat down to 22 Hz.
I owned Quad USA Monitor Pros for 6 yrs. These are similar to the Quad 2805s. Quads are superb speakers, with a cult-like following in the sense that people who have or had them LOVE them. Quad owners are on the good side; they are not equipment'philes or bass-heads, etc; they are music lovers. Likely Quad owners go to or have been to lots of concerts.
For whatever the reason, I've never heard Quads perform up to their considerable potential at dealers or at shows. And thus I am wondering if the 2805's you heard and liked were heard in someones home. Its been mentioned in bulletin boards that Quads are difficult to set up effectively. I never thought so. Pay attention to the details common to setting up any speaker. After that, catch the 1st reflection points with room treatment, room treat some of front wall behind the speakers, and don't put any objects in between the speakers.
As has been mentioned, Quads are somewhat shy in upper frequencies and in the bass. Their recessed upper end is not noticeable or is hardly ever noticeable likely as the lightness in the bass serves to not highlight the recessed high end. It was only after listening to my next speaker that the recessed high end in the Quads became obvious. Another thing about the Quads, should they ever require repair, QS&D on the east coast and Nick Gowen (True Sound) on the west coast provide their clients with some of the best support in the industry.
Something that may sway your selection between the Quad and Avantgarde is the type of music you listen to. The Quad's limitations, their lack of bass, lack of small and large scale dynamics, their inability to play reasonable loud limit the types of music played satisfactorily. These characteristics may not affect you if you listen mostly to rock, folk, jazz, vocal, world music, and chamber. If you enjoy orchestral music or organ music, these limitations at some point will be bothersome.
I have a different take than Electroid who guessed that if one likes one of these speakers they'd not like the other. I own Avantgarde Duos which share many similarities to the Unos. The Duos, when set up correctly and used with synergistic equipment, share the magic that music lovers love their Quads for but adds a lot more to the table. Should a Quad owner decide they want that next step that gets them closer to the real thing, Avantgardes can provide that next step.
The Duos do not limit the types of music played as all types of music play well. AGs are full extension, no upper or lower frequency limitations. Large scale and small scale dynamics are literally breathtaking. When you walk by an open window where music is playing, it is easy to determine if the music is live or reproduced. It is the inability to reproduce dynamics, shared by many systems, that is the give away. When AGs are playing, your mind has to work a lot harder to decide if the music is live or not.
The AG's ability to capture subtle dynamic changes is as important if not more important than their way with large scale dynamics. Listening on the Quads to someone like Sinatra or Ella with their amazing instruments, the essence of these singers comes through loud and clear. Superb sounding voices are in between your speakers. The Duos add to this the subtle low volume vocal characteristics that grace their vocals. Instead of just the essence of their singing, you hear all of their singing--this is a huge difference. Instead of having superb sounding voices in between your speakers, you are now sitting in the club where they are singing. With classical, in part due to the emotion involvement gained in hearing the subtle details that other systems ignore, I'm anxious to get home for a listening session after leaving a symphony concert.
With the Quads, guests would listen and be awed with the sound. And why not? The sound was more music-like with none of the showy but ultimately grating characteristics heard from some systems. Non-audio types were stunned that a stereo could reproduce music so well. With the Duos, reactions were dramatically different as guests felt they were participates at a concert. At times theyd clap after a song or an LP side finished.
Regarding some of the comments in this thread. Someone implied that the Avantgardes cannot be placed close to a sidewall. My recollection of their dispersion characteristics is that they do not project much sound in that direction. Thus, I think the AGs can be placed close to side walls.
Per the mention that AGs do not image, soundstage or focus well. That is incorrect--don't blame the messenger! If AG's youve heard are lacking in those areas, there is something amiss in the electronics, front end, cables, room placement, crossover adjustment, etc. My AGs have created a large rectangular soundstage with images properly placed all over the stage including way behind each speaker.
George, good luck on your quest. You are considering 2 fabulous speakers, there are no wrong decisions.
I agree with tubes108, I have owned quad US monitors for many years and loved them and they are great speakers, But I purchased a pair of Unos for a small room and they take the music to another level, whether I play the musuc low or loud the sound is pure,transparent and dynamic. Depth is every bit as good as my quads, and I can play any kind of music without ever having to worry if the speakers will break up.Of course associated equipment is very inportant as the unos are like large magnifying glasses, but once set up properly in a properly treated room, they will outperform any quad I have heard.The realism is quite fantastic, listening to them from an adjoining room and it sounds like live music is playing.
I need to echo Majicjazz and Tubes 108 in that I have the Uno speakers and the imaging and soundstaging in my 20' x 25" room is fantastic. In fact it is the best I have ever had after close to 40 years playing this game. During that time I have had three pairs of Quads so I know what I am talking about. The Unos do require great electronics in front of them as well as cabling, etc. Everything makes a difference, but if you're willing to work at it the Unos are phenomenal. I have a pair Duntech Princess speakers (similar to the Dunlavy SCIVa) that I also like very well and have owned for twenty years.If you can hear the Unos with the Tom Evans Linear A amp and his pre-amp you will be in audio heaven - dynamics, soundstaging, imaging, harmonics. the ability reproduce "you are there with the music" emotional hit I strive for are there in spades. You can play them at any sound level and still have all these values in place which also is incredibly unique. I also like to listen at realistic sound levels with no distortion and this may be the crowning glory of the Unos. As people who are not audiophiles listen to my system, the words used more often are "pure" "sweet" "real" and "we're right there!" Quads are great, but if you have the room and the electronics you owe to yourself to hear the Unos.