Wow, that is one hell of a listening room space and system, nice one @catcando 
Has Jim’s sweet spot throne had to be raised up on a plinth?
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Very cool.
What movie were you watching?
Ikea chair. They sit very low. Plinth was to get it up to regular chair height.
If it’s a Poang yep, have to agree.
That is very fucking 
Crazy good.
This one will be trotted out for years to come
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Indeed, in David Attenborough voice…
Here we can see from the left, The Greater Crested Tit, The Bearded Short Legged Tit and Gregg.
David Attenborough voice off.
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I’ve clearly just put some excellent Japanese jazz on and nodded off.
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Are they 3 way and what crossover is used?
4-way and using Najda - @edd9000 and I were there to do some measuring and adjustment to the XO @Jim was there for the food and to steal the sweet spot 
It’s a very clever design with the tweeter horn concentric with the mid horn and acting as a sort of phase plug, I think. The lower mid is the 4x12” drivers (one would probably do for home listening 
). The tweeter horn was originally mounted with TAD TD-2001s, but they were blown, so Gregg replaced with Faitals HF10’s. The mid horn driver is an 8” cone.
Oh, and 18” subs.
This is your actual million dollar speaker - clearly a lot of R&D money went into these and like a lot of cinema stuff ended up in skips at the end of it’s life 
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Any idea when they were made ?
Not sure, Gregg or Edd can hopefully advise.
2000
That was also the last year they were made, I think.
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I think it was in use from 1990 or so to the 2010s when the remaining Imax cinemas either closed or were refitted with digital projection and a new sound system.
I think bits of ours came from Birmingham, Manchester and the London Science museum.
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This is from the designer of this IMAX system
IMAX never published specifications for theater acoustics or sound systems. The information was proprietary. They didn’t even sell projectors or sound systems: they only leased those items.
There was never any doubt of the results we would achieve in the development process that led to the PPS loudspeaker design. We did enough advance analysis and testing - both in laboratory and in theater environments - to ensure that there were no surprises. The results were as expected.
As for a “sweet spot,” projection quality is more definitive of that than sound quality. When you sit in extreme left or right positions - especially in the front rows - there is inevitably distortion of the image. For that reason, I suggest selection a central seating position - possibly just rearward of the center rows of seats - for the best visual experience. BTW, this applies to all movie formats, not just to IMAX.
The subbass array is driven from a completely separate signal chain than the channel signals. First, each channel signal is routed through highpass and lowpass filters. The highpass outputs are sent to their respective speakers. The lowpass outputs are mixed and send to the subbass amp racks. You will need another amp and additional filtering to drive a subwoofer, but the bandwidth of the main speaker is enough that subbass won’t really be necessary in a residential sound system.
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Rubbish. MOAR BASS.
