What affects front to back depth in room/ system?

It's probably already been said, but FWIW real 'depth of image' is captured in the recording process. If it ain't there it ain't going to be anywhere.

In a carefully set up two channel system all you get is what is on the recording. There are many variations of what folks think is soundstage mostly depending on how they use their room in their set up and think what they have achieved is really the 'depth of image' so often referred to by folks, it's not. That sound is only the result of management of the rooms construction, size, speaker placement, reflections, and nulls/nodes, etc. 

If you want to see how your system reproduces true depth of image get yourself a recording that has it in the first place. I always recommend Opus 3's "Depth of Image" on an LP if you can use it or CD. IF your system is properly set up its sound will blow you away. It's just amazing! This recording is a compilation of classical, jazz, pop, taken from their recording of such music from their other recordings. Their mic set up is simple and 'correct'. The manual will discuss all of the cuts and tell you what you should hear - if you can't detect all that they tell you exists, then you know that you need to adjust your setup to get there. High quality equipment may help some, but a reasonably good system can get you there. 

@dsnyder0cnn 

Thank you for your post. I appreciate your foot covers.

@dsnyder0cnn my room measures 15’x19’ (4.57m x 5.79m).

The front of the speakers are 4’6" (1.37m) from the front wall. Middle of tweeter left speaker to middle of tweeter right speaker is 7’8" (2.3m). side of speaker to each side wall is 4’11" (1.5m). Ear in the listening position to front of speaker baffle (tweeters are at ear level) is around 9’3 (2.8m)" -same for left and right. I have about 2’ (.6m) from ears to the back wall.

The speakers are about 1 1/2’(.45m) closer together than what it would take to make an equilateral triangle, but this is where they work best (keeping the biggest emphasis on best bass and the right size mouth I hear singing the song).

@wolf_garcia ​​​​and @tablejockey I was just spinning the UHQR Aja tonight (just got it after seeing them with the Eagles last week). Man, if everything sounded as good as that album does, I wouldn’t need to fiddle with all these fidly bits.

@skinzy I’m starting to think the same thing. I’m really curious to see what the difference will be after I treat the room though.

@axeis1 I have Robert Harley’s book (which is pretty great) and of course Paul McGowans- which was quite helpful at the beginning.

@labpro Thanks for mentioning Acoustical Sciences Corporation. I checked out their tube traps a while ago, and was seriosuly considering those.

While we’re here- I’ve been thinking about going with Acoustic Fields (Dennis is who suggested I move speakers from the short wall to the long wall instead...which was a great improvement. The only thing is I don’t see any posts on here about them, but see some of the others. Does anyone here have experience dealing with Acoustic Fields/ Dennis or opinions/ feedback?

I don't think this can be oversimplified. It is a combination  of things. 

* speaker placement

* room treatment

*speaker isolation

* recording styles or techniques

*cabling

*music service 

*low noise in signal

I believe it is a combination of things.  Each helps but it is the cumulative result.

@veerossi - thanks for those dimensions. I don't see any issues. You are kind-of close to the back wall, but that's way better than sitting in the middle of the room, where you would experience bass nulls. Your gear looks great to me, so next steps are probably room treatment, as others have recommended.

Working out how much treatment is needed and where to place it is not rocket science. A few measurements from your listening position using Room EQ Wizard and a calibrated mic (eg., miniDSP UMIK-1) will tell you just about all you need to know. Feel free to PM me if I can help.