Short answer is the cliche “the more ..the merrier” especially if you expect to swap out components ...test cables ... change inputs... then ease of access is a distinct enabler
Over the years I have learned.....leave at LEAST 12" between the back of each component and the wall. Keep in mind, this is a bare minimum with unusual and sometimes extreme contortion of the body. Not recommended.
depends on so many things. mostly size of your room, and where your gear is relative to your amps and speakers. then next there is length of your power cords and where the outlets are. if your outlets are behind your gear will the power cords need to be suspended across or on the floor. so it's really a planning question. if your phono pre has adjustments on the rear of your gear, or if you will be moving cables around regularly, then more space is critical. if you expect to be a set and forget type then less space is needed as it will be very occasional.
I cannot walk behind my racks as I have too much stuff. but I have about 12" from rack to wall.
then how anal are you on how things look, hiding cables and power cords, etc. etc.
if you leave a large space where everything is seen then it will have a bit of a cluttered industrial look. are your racks see through, or heavy and furniture looking and blocking seeing all the cables?
so picture in your mind the end look you are seeking. or just let it happen.
Having installed racks for a living, you find away to be able to get behind them.
I don't play the reach around game anymore.
So if its close to a wall it has to rotate or pull out somehow.
If you have some form of mass load rack or something to heavy to move, leave it out far enough to get behind it with a flash light.
So yes, literally far enough to walk behind.
I just measured; I got 22 inches...easily a walk-in.
I always had plenty of room behind my audio racks.
If I can walk around my loudspeakers, and I do, I also walk around my audio racks.
As others have said, it depends on the size of the room and the amount of gear you have. Gear is not an issue for me as my system is straightforward and positioned on one rack (TT/IA/CDP). Room size is another matter at only 16' deep, so I have about 18" of space between the rack and the wall. Not enough for me to walk or stand behind, but enough to have easy access to components & cables.
I used the use the mirror trick to see from the front of the equipment right-side up connector labels on the back panels. But I would prefer to be able to walk behind the racks. (I do not plan ever to move things around, but I suspect Kedar will visit at some point to carpet bomb the equipment with Mooks.)
I have to figure out the minimum amount of space I will need to be able to walk behind the racks.
I recently did a direct comparison between two preamps. I rotated the each 90 degrees on my rack so that their back plates were pointed out the side of the rack. It my system were not in my formal living room, I would seriously consider this permanently. It was so much easier to deal with connections. I think the ideal set up would be to have the rack against a wall that has sound proof doors so that the back of the rack could be accessed from another room. If I were designing a space from scratch, this would be a consideration.
My current rack is way to close to the wall, about 9". It is a simple system with few components, but cable swaps are really difficult. One of the things I often think about is how to remove gear from my listening room and still have it be able to function. The latest idea is to move my amps to the basement beneath my speakers and some rack components on the other side of a wall. It takes lots of planning and is quite a difficult problem to solve. I'm not one of those guys who has to see the gear.
I was @ 28.5 inches prior to 22. I lost weight so it allowed me to find a new minimum...I first set it @ 24 inches, but I found out that with my new body I could get away with 22 inches. :b
So the size of the listener is an integral part of this equation, and the age too as we don't bend as good as we age...in general. But I know friends who are in their mid seventies and they can bend graciously.
Do you guys hire cleaning ladies in your audiophile rooms?
After a rough measurement I should be able to walk carefully behind the future row of racks with 15” of space between the back of the racks and the wall.