Those grills are well suited for low xmax woofers, but probably not best for larger xmax subwoofers unless the front trim on the rim of the subwoofer stands out significantly from the rolled surround. I have a pair on my 10 inch woofers in my main speakers and with an xmax of 3.5 mm, there's plenty of room, but if the xmax is about 12mm, it could get pretty close.
I guess it depends on several factors. I'm using a 15" grill on a 12" speaker. The grill provides for .650" clearance from the baffle face. My Xmax is about .750". The surround will only be .125" above the baffle because I seated the woofer below flush.
I'm in the hole about .100" at Xmax. My design probably can't reach X-max, but I'll add a washer just to be sure.
This grill would have plenty of room for a flush mount 12" speaker with 12mm or less of travel. The Dayton HF in a sealed box comes to mind.
In that case, don't use washers, put some gasket tape on the bottom side of the grille, and I would actually recommend using the grill clamps from Pe, unless you already have a decent plane to clamp them down, and 3 clamps are not likely enough, I've used similiar grilles on subwoofers and they rattled even with 4 clamps, in the case of subs, 8 would probably be better, lol
the clamps that PE sells, are the best way to go, rather than putting a screw through the rubber material, if you dead set on putting the screws through the rubber, which you apparently you already did, I would go with washers that would cover to the outer limits of the rubber coating.
joorge,in answer to your OP,the best grille is no grille at all,in MHO.Years of listening have led me to this conclusion.My recently completed mains have no obscuring material over them.However, if drivers need protection from inquisitive pets or children,then some form of protection is mandatory!As well,pets and kiddies need protection too;they cant be replaced as easily as an driver. Hope this helps.Mike
It seems intuitive that the grill will have some effect. I'm not fussing about a Hz or dB here and there. I interpret the comments to mean that the effect is quite small. If so, I'll proceed with the grill.