Level the floor

My wood floor is nearly identical to your slope, it is down 3/4" within the first 24" from the wall, then very little slope after that.

My existing rack, bentwood and glass has supports in the back and sides.

I cut new end ’feet’, hard maple, and tapered, 3/4" higher in the front. Note, they extend a few inches past the back and in front of the rack. Big screws with lock washers hold the new supports to the existing end pieces. Not only level, but increased stablility due to extension of the supports..

eric,

even if the turntable is leveled, in OP's case by putting 1" high 'lifters' under the front feet

if your rack is pitched forward under the turntable, the combined weight of all other components is also pitched forward, fronts of each piece lower than the rear, add the combined weight of my 3 glass shelves pitched forward: any vibrations will more readily rock the rack forward then back ...., it is far better to level the rack and have all the combined weight be a downward force.

KLH OEM stand tilted their speakers back 8 degrees

JBL Speaker Stands

For Klipsch (they made their OEM ones also)

Custom, get smaller speakers higher and tilted

mrj OP

I was assuming the speakers would be forward from the back wall, to place them on the very gradual portion of the floor. Thus, shims ought to work.

In any case, I believe speakers should be tilted back so that the tweeters are aimed at seated ear level. This will involve tilting, usually accomplished by a block or riser in the front.

In my case, concealed by the lower ’skirt’ I have attached a 1-1/2" block in the front, the 2 front wheels attach to it, thus the rear single wheel, with no block, keeps the rear of the speaker 1-1/2" lower. Blurred, hard to see, bottom of image

Easier to see, 9th photo here, as well as the speakers in-place tilted

https://www.audiogon.com/systems/9511

My heavy speakers can be on wheels, lighter speakers can be on ’skid’ plates, allowing alternate toe-ins