Sweetspot *as heard* is wider than you'd think on modern Harbeths you know. Don't shoot the messenger where the grilles are concerned, but the hf response is objectively better (verified by third party tests) with grilles on.
There was a massive thing about Harbeth grille design from the SHL5 and C7 onwards. The cloth just touches the fronts of the tweeters so has less effect it's claimed,than distancing it out *apparently* and the 'frameless frame,' which needs their special tool to remove on mine, is deliberately recessed into a groove to minimise diffraction issues (the entire dispersion 'thing' with speakers like this may really be of academic interest in a larger room well away from boundaries as recommended by the manufacturer as sidewall reflections may be well down in level). Recommendation has always been away from walls with main tweeter at ear level, so toed towards the listener. It's only peeps like me with small rooms and a near to mid field distance that suffer boom and relection issues... In my case if using Harbeths, the C7-XD would almost certainly be better due to narrower baffle and slightly less bass extension, at least now th ebasic 'tone' is so similar to the 5+-XD.
Thofi, in your post #140 above - what the heck are you doing posting here on ASR when you say you don't care what the designer intended from his designs he spent so long developing? I repeat, the grilles *on this model* were carefully researched to be as nonintrusive as possible and to AID the performance of the speakers. Obviously once purchased, you can do what you like to them (one bod converted his XD Harbeths to bi-amp passive use, thereby destroying almost any residual value they had. But hey, they're his boxes so he can do whatever he likes with them...
I remember the same with a now ancient Epos speaker, where the final design meant the port being turned into a 'controlled leak' with stuck in foam plugs. All the 'expert audiophiles' tore the foam out and liked the 80Hz boom that resulted (they all used Linn vinyl players mostly which back then added to the bassy syrup). the designer got so pissed off he just pushed the foams in tightly but didn't glue them in, so the end user could do what they liked - I put mine in sideways as a nice compromise with his blessing
I've been through the whole valve/tube thing twice in my hifi life, once with Quad and rather nice Radford amps in th emid 70's when the Radford wasn't that old and again around 1989 with some Tube Technology mono amps (with ARC SP14 preamp) which proved to be a disaster as they ate the poor thrashed 4 x EL34's a channel to 100W, said valves being knackered after less than a year! Maybe if I'd got a set of same-price (then) E.A.R. 509 cozy-toned mono's, they'd have lasted far longer! All these glowing bottles and over-lush tones just don't interest any more and I rather like the idea now of some of the new tiny power-boxes that can be hidden away (better still, half decent active speakers with amps inside, but hey, this is a Harbeth thread).