I notice a difference with the grills in place on my RKs. Not massive mind you but perceptible. The grills surrounds are quite thick, seem to close the sound stage a little, or focus the sound.
On the other hand with my old MAs i couldnt tell a difference
If I’m honest I can only think that speaker grilles alter the sound no matter what their construction, foam being the commonest I guess.
Many speakers are specifically designed to sound their best with the grilles on, but I’ve often preferred to use them without.
My SBL grilles have turned to dust and I need replacements but there are no original ones available, it’s quite sobering when you need to spend close to £200 to get some suitably cut foam but I gather the cutting is expensive due to the toxic fumes produced.
I tend leave my n-SAT’s grilles in place although sometimes i do take them off so i can drool over their good looks. I like to look at their tiny drivers and feel amazed at how much sound can come out of such a small box 
My LS50 Meta’s don’t even have the option of grills 
With Naim SBL & NBLs I always left them on. I have 808’s now and also leave them on as my kids can be savages when they are feeling mischievous so its best they don’t see anything interesting behind them! Sound wise I have no idea if they would be better without but no pics seem to display them without so maybe best with 🤷
My Naim Credo grills have a lightweight frame, with a thin black cloth on them. Even though its thin, I still think it sounds better/more open with them off.
The grills are on on my Neats but only because I have a very inquisitive 2 year old grandson so I will have to live with any loss in sound quality for the moment.
I find I get a more focused sound with the grilles on with my Kudos 808s and also prefer the look. A degree of protection is also provided from wagging dog’s tails! I do believe I read somewhere that Derek voiced them to be used with the grilles on.
With my grills in place things are more somewhat “over there somewhere”
One day i will listen to these speakers👍
Coooorrrrrr☺️
Theres someone who does metal grill with lots of holes in that look good for these. the expanded metal company?
Gale I seem to remember.
the ATC metal grills… hmmm! what were they thinking! visually challenging but sonically transparent - only to be used when friends young children appear
Those ATC grills look the part tho, esp on the SC40s. ATC’s recommendation, and the consensus on here, is that these grills make no difference to the sound whether on or off so mine stay on. They look smart, make the speaker look complete and offer that bit of protection.
I have ATC SCM 40’s, the grills stay on, they offer reasonable protection against errant objects, usually from our dogs ‘playing ball’ in the lounge, “BAD DOGS!!”
I really hate the look of speakers without grills and won’t have them in my lounge.
Got my ex-demo Dynaudios less than half price as the shop had ‘mislaid’ the grilles.
Wouldn’t have used them anyway 
