Now this is an interesting speaker for sure. A bit surprising in fact for an unassuming speaker. I almost thought those were VU's on these things! Now that would be a quest for sure. These things sound pretty dang solid too
Vintage on Vintage
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The MK III version ('Improved' or not) were a bit sloppy in the bass, which stepped up 5dB below 90Hz or so and went down measurably to 17Hz or so, which set doors rattling even if the fundamental couldn't be 'heard,' the mid-bass cancellation level above, being the level the midrange and top was basically pulled down to. The MK IV had stands as pictured, the bass was re-tuned to roll off a little higher (30Hz or so from memory) and there was extra lf filtering and response tilt controls available behind the bottom trim plates. In a UK room, these speakers weren't at all 'unassuming' I can tell you, but they did so much 'right' back then, the character exhibiting a hint of 'sparkle' up top (the HF1300 had a natural slight peak at 13khz or so. I'd love to hear these again on a modern digital and even modern vinyl source, as I feel they'd come into their own these days. A few years in, the bass and mid-drivers were changed to TDL made ones (there's a lengthy story as to how TDL made drivers, then speakers when IMF went under, the running of both companies basically by the same man eventually, John Wright, who'd designed the 1960s Goldring cartridges - G800 era) I gather.
I should stop reminiscing like this - it's painful how long ago it all was and these were genuinely fun times, with all this new music coming along that really was 'new' and audio gear coming on in many small but varies leaps and bounds...
I may have included the JBL L200s in my list as I have such good memories of their scale and general dynamics (nothing like as coloured as the 4310s we also had), but we only had these huge (for UK rooms) speakers for a short while…
One final make before I shuffle off and shut the memory floodgates - and it's another US design although made in the UK - the AR LST which was awesome as I recall and less response-coloured than the AR3a Improved we had. The AR3-descended 10Pi was an odd looking thing, with the wooden trim/flap covering the controls on top rather than underneath. rare as hens teeth, but a seriously good 'tone' as I remember, which again should do justice to modern sources.