Another idea - post noteworthy speakers, what they changed, and when introduced.
AR - acoustic suspension allows smaller speakers
Advent - about 1970? (I'm not sure what they did better than the ARs...)
Rogers mini-monitors...
What Advent did better than AR was to provide slightly better sound (according to Kloss, who designed both of them) at half the price.
But it brings up an interesting aspect of this whole discussion. Henry Kloss experimented with all sorts of cone materials, voice coil materials, and basket attachments to find something that was inexpensive to manufacture but musically effective. What small company like the startup Advent of 1969 would actually make their own drivers? Advent did. And one thing the Advent had that AR did not was a next-level tweeter design. Some don't think much of the Advent fried-egg tweeter now, but in 1969, Kloss found that the shape (a central dome surrounded by a waveguide shape) had flexibility relative to frequency. At high frequencies, only the central dome did much radiating, while at mid-range frequencies, the whole surface radiated. Thus, the tweeter was able to project substantial acoustic power even down into the mid-range, which permitted a simple crossover at a rather low frequency (something like 1500-1800 Hz, and none too steep at that). The woofer design was damped by the sealed cabinet.
Advents rolled off above 15 KHz, but we've already had the discussion on this forum many times that this is hardly the most damaging thing to actual music, particularly acoustic music. In the late 80's, I compared my Advents from 1977 to Magneplanars at a "high-end" store in San Antonio where I lived at the time. This was not a blind test, but the differences were enough to guard against domination by subconscious bias. After listening back and forth, I asked the guy at the store (who owned the store and was one of the few who was really excellent) if he thought the Magneplanars sounded like frying bacon--just too much sizzle in the high end. His response: "Yes, I suppose they do." When Advent fans use the word "smooth", they mean the high end didn't sound brittle like that, and that may be anathema to people who study measurements today. I'm not exactly sure that it is necessary for speakers to be linear to 20 KHz, because a lot of what they will transmit won't be music anyway, at least from many real sources. We were listening to an LP played on a Linn Sondek LP12, reasonably close to the state of the art in the late 80's. We also listened to a CD, played in my brand new Magnavox CDB-650, which the store owner thought was one of the best available (I agreed and I still agree, if I can find the right belt for it).
Yes, there are lots of better speakers now, but there are also lots of speakers that simply can't do what those bigger acoustic-suspension speakers did, in terms of bass impact that doesn't boom or ring. I think there was a big change with Thiel-Small calculations that led to the universal use of small, ported cabinets, usually coupled to subwoofers to make up for their limitations. These are much pickier about placement, in my experience, particularly in relation to the back wall (and depending on which way the port aims). The smaller box, with prettier veneers and grills, became the dominant paradigm below the very high end, and nobody wants to find a spot for those big Advents, AR's, KLH's, and so on.
I'm always considering speakers, and I auditioned quite a few a couple of years ago. I found that anything below about $2000 a pair did not make a brass quintet sound like a brass quintet. This is subjective and subject to all sorts of derision here, and I don't know what measurements affect my impression (I am sure what I hear is measurable)--maybe it's mid- or upper-bass response. The audition circumstances certainly affected it. But the French horn sounded like a trombone, and the tuba sounded like a euphonium, and the orchestral sound of the trumpets leaned in the direction of a bright jazz sound (think Harry James or Herb Alpert rather than Miles Davis). I was listening to a Canadian Brass CD, and was quite familiar with it. Also, I have played on the same stage with the Canadian Brass on two occasions, and I play regularly in my own brass quintet, so I know what the real thing sounds like. I'm also highly attuned to the sound of individual players and instruments--certainly the outcome of a training process. Surprisingly to me, many of the modern, small speakers simply could not create a realistic timbre for brass instruments.
Advents do. I can listen to that CD through my two pairs of Advents, powered by two B&K amps, at so-called reference volume (peaks at well over 100 dB SPL), walk into the next room (to disconnect my eyes from the sensory process), and it sounds just like a real brass quintet playing in the next room. Making it sound like that requires filling the room with sound, and it seems the small speakers for sale these days simply don't do that. (My room is 15x24, with a sloped ceiling that slopes up from onen side to open into a loft area that has about the same volume, so volume is relatively high but without that many opposing parallel walls). Modern Pioneer cheapies (the SP-BS22LR) have the right timbre, though with a ported-speaker boominess in the mid-bass in comparison with my Advents, but only if I'm relatively close. (I use them for my office system, driven by an Adcom 535.) An old pair of Canton GL260's that I own, which are not really bigger than the Pioneers, have a bit less bass but a realistic sound for a small listening room.
One thing I rarely see measured in loudspeaker tests (with the partial exception of Amir's tests, which measure distortion with respect to SPL up to a point) is the maximum SPL capability of the speaker. Those big drivers in the speakers of old could make loud sounds, while the current inexpensive speakers with drivers of 6" or less just can't, it seems to me, when listening in a larger from 15 or 18 feet away. Now, if someone wants really loud sound, they are directed to horn-loaded speakers, and certainly horn/wave-guide designs have improved over the years from the (inappropriate for home-use) long-throw exponential horns of the past to bi-radial, wide dispersion horns of the present.
Those Advents were a hundred bucks each in the 70's (I paid $115 each for my first pair of NLA's in 1977). I bought the second pair a couple of years ago for the same price (in actual dollars). In real dollars, they would still be inexpensive relative to the market, though I doubt any company like Advent during the pre-Jensen years could do at the same cost point what Advent did in making their own drivers right from the start.
There are no useful measurements of old Advent Loudspeakers (either the 1969 originals or the 1976 replacement that used ferrofluid to cool and damp the tweeters to allow the crossovers to drive them even harder) that I can find on the internet, and I'm thinking the size of these cabinets would make it rather inconvenient to send a pair in carefully restored/maintained condition to Amir. So we have only subjective opinions (including mine) to feed comparisons with modern speakers. But I haven't heard much in anything approaching the same price range that can make as much sound, while still maintaining what is at least an accurate enough frequency response to make brass instruments sound like themselves, and do so with peaks up to 105 dB SPL.
Rick "who'd love to see a Klippel test of restored Advent OLA's or NLA's" Denney