[mulveling]

Gosh those are particularly beautiful speakers! I found the GRF 90's predecessor, the Yorkminster SE (though superficially different, they are very similar on paper and share the 12" pepperpot driver and rear-porting), to have a bit too much treble energy for my liking, on flat settings - more so than the adjacent models Kensington and Canterbury. However I also did get absolutely excellent bass response from the Yorkminster, in my room - they really beat the pants of Kensington SE & Canterbury SE in that. The Yorkies also had more detail and transparency than either, though not more than the newer Canterbury GR.

In general, the Kensington SE, Yorkimnster SE, and Canterbury GR (to a lesser extent the Canterbury SE, which was darker) have all been able to produce searing treble at times. It's something I'd struggled with intermittently in the past, especially after major component changes. Maybe this is the downside of the efficient tweeter horn. Gear matching is crucial (some gear is just NOT pepperpot horn friendly up top) - perhaps that's why I ended up greatly favoring Koetsu cartridges (cartridges like upper Ortofon MC's are just too much up top), and also use tubes. The VAC amplifiers and integrateds, particularly the latest auto-bias line, are absolutely superb matches with Tannoy Prestige speakers. Just beautiful. I have a pair of Signature 200iQ on their way to my Canterbury GR right now. I literally can’t imagine a more perfect balance than this with the 200iQ’s - nothing missing, nothing out of proportion just my target for beautiful music.

And certainly, further experimentation with positioning, acoustic controls, even speaker feet can possibly make strides towards your ideal sonic balance. I hope you make progress and enjoy a long relationship with these beautiful speakers!