The old Quad can actually reproduce some bass given the large-ish panel size so they work for small jazz combos, any smaller scale stuff; it isn’t what I would play Sabbath on at high db because that isn’t what the speaker’s strength is-- but voice, strings and even orchestra can work, though I found that on large scale works you hear from a more distant perspective-- like sitting in a balcony, not up front. The midrange can be eerie, it’s so "there" on some recordings; like most things in audio, you often don’t realize that you are hearing an artifact of the machinery playing until it is gone and the Quad can disappear.
All that said, they present a weird load to the amplifier, can’t take power or they will arc (not good) and are dynamically limited in how many db they put out. But dynamics is a relative thing. If you get the system to reveal information at lower volume levels, the crescendos or louder parts don’t have to be as loud in an absolute sense to give you the dynamic range of most music.
I used to use ARC tube amps; I currently use a pair of Quad IIs made in 1961 that were refurbished and retubed with first class glass-- NOS GEC KT 66s, which were originally spec’d for the amp.
They are a cool thing to be able to learn to listen through, and hear the music, rather than having it played at you when everything lines up.
When you consider how well these do what they do, you are willing to forgive some of their limitations given that they came to market more than 60 years ago and many are still in use.
I did a piece on what it is like to own and use them which I can post. But, for some, modern speakers will put them to shame in other areas that may be more important overall. For me, the midrange is absolutely critical and that’s where these shine.
PS: I’d add that the bass that is there, when properly positioned, is coherent and tonally correct so you don’t hear discontinuities typical of multi driver speakers. Adding a sub, at least back in the old days, detracted from that sense of "oneness"-- that the entire presentation is one piece--and you were aware that you were listening to different speakers. The Gradient was used with the 63 and I guess with the 57- the older one-- which is the speaker I’m talking about. There are a multitude of other options to enhance bass, including open baffle, Maggie bass panels, adding more Quad panels, etc. but in my estimation, it defeats the simplicity of the thing. I wouldn’t mind a stacked pair if I could squeeze them in, but my main room is already occupied by a big system, and a stacked set of old Quads in my front parlor would overwhelm the room, aesthetically if not sonically.
You should hear them for what they are and aren’t. I don’t think they are the "right" speaker for someone that needs an all around speaker system for all types of music, especially if you listen to hard rock.
The later model- the 63 -- was a better all around speaker as are the later incarnations, but the 63 I had, as modified by Crosby--which was the bee’s knees at the time-- just wasn’t in the same league to my ears as the original for midrange purity, though it is the "better" speaker for overall use.
