Axiom Home Page Forums General Discussion Home Theater Lets plan a theater space

Epson Pj alignment and test pattern for focus/overscan

Cant complain for $300. (Although it took a month to get it!)

Another screenie

Will retest frequency response plot and update. Initial impressions seem as though there should be very little change if any. Good news.

Finishing items are:

Finish screen wall.
Veneer Doors and install hardware and glass.
Panel cover for electrical.
Sidewall absorbtion panels.
Rear wall media shelf and diffusers.

Bunch of work to go!

Do some seating tests before you get too far further... The screen looks way too low to the floor for extended comfort.
Your eyes in a seated position should be around 1/3 up from the bottom of the screen.

The pictures make it look like your eyes will be around lined up with the middle of the screen... Eek!

Will do. I've never heard that guideline before. I thought THX said the axis should be 0-15 degrees above eye level. The planned bar stool row will be way lower by comparison. Right now the midpoint of the screen is just above the tweeters sitting at 39". I think defacto seating eye level is 40". The screen is pretty close to directly on viewing axis.

I left more room above the screen for the planned arch. The screen is cheated 4" or so lower than room height center.

Btw, its 106" diagonal and the seating row is around 140" back.

Shouldn't Don be wearing a golf shirt this time of year?

Don would have to be wearing zany golf pants!


We watched a few eps of Game of thrones and the screen position seems fine. I think the 1/3 guideline is a sensible one to follow, but in my room we got away with on axis. Did that Idea sprout in a forum. Cant find a legit source for it. Curious.

Since the screen is in place I now have a firm boundary to work with for speaker placement tweaking. I toed in the speakers from 8" off centerline at mlp to 5" off centerline at mlp. So, the speaker's direct on axis energy spread at the mlp went from a 16" spread to 10".

To paint the picture very clearly, this is a miniscule change of maybe 2 degrees or so over the distance from speaker to listener. I also turned the sub level down a little for 2 channel sources. (Music gets 7db less subs than do movies now.). The result is a more present vocalist and overall balance to the phantom image.

Here is the result to date. The 2-4khz valley is better. The rest is up to treatments now. Chasing the last few dbs of flatness.

Screen installed, with bass traps, sofa and speakers and subs dialed in. 1/12 octave measurement, pink noise averaged over 30seconds. (I average the tests because the exact position of the mic on the ipad wavers as I hold it-- super accurate I know, but the trends between tests show it is consistent and predictable. )

15 degrees is for the maximum you should have to look up from your seated position, but it doesn't take into account "looking down".

Going with THX specs, your viewing angle, seating distance, and screen size all line up nicely. Many people go a little bigger screen wise than THX (like I am at 138" screen at 12 feet (eyes to screen) and everyone loves it). Keep in mind that THX is NOT about the "big movie experience" of IMAX, Cinemark XD, etc, and I am not saying to go that route, but you may find that you like being a little closer to the 106" screen than 11.667 feet too. My previous theater had 104" and I sat 14.5 feet back and liked it, so no worries either way.
(Here is a nice little THX calculator from many years ago that is easy to use: THX Calculator )

Here is something on the 15 degree that I found with a quick Google search... I can't imagine being in the front row with my eyes lined up almost with the bottom of the image, but that is how it is drawn, not that the 15 degree rule is bad (it isn't bad).


Back to the "eyes at about 1/3 from the bottom of the screen" thing... I just hit up Google...

The following is from AudioCircle.com originally from some woodworking site for hosting. Just from Google...


Home Theater Shack says 1/3 as well (some bozo jumps in and talks about a 50" plasma, but for larger projection screens it is 1/3:
HTS Height of Fixed Screen discussion

They say the same in this conversation from AVForums... 1/3 from the bottom is eye height:
AVF Screen Height conversation


So on and so forth. Several mentions on AVS as well.

The only "mainstream" website that should know this stuff that doesn't seem to say 1/3 is Audioholics, and we know what kind of people are over there. LOL

Maybe it is an illusion of the photos as well. The general rule of thumb is 1/3 from the bottom of the screen should be around 38" off the floor (average human eyeball height when seated).

Of course, lots of leeway here too. If someone reclines or slouches, then their eyes are lower (which would put the screen lower too *in theory*) HOWEVER, they are now no longer looking straight ahead, but are looking more upward, which screws the 15 degree rule and then would say that the screen needs to be higher.

Fun stuff, isn't it?!?

Thanks for a great reply. If I was employing a second row of seating with leg room I would definitely need to reconsider the calculator and move the screen higher. Part of the decision to go this screen size and seating distance was to meet audio criteria first. The speakers and mlp within room serve to satisfy best modal behaviour and 2ch setup ratios. Pretty much the entire build was audio centric in the design phase.

I had to decide if all LCR speakers would live behind the screen and go bigger, but space the LR channels narrower, or go smaller and land the LR speakers closer to a 2ch configuration outside of the screen envelope. I chickened out when I considered the tower speakers interaction with the screen frame and support structure. Smaller screen, wider placement won out. In the end it all is panning out, but making those decisions wasn't easy at the time.