Room layout and listening position

[Victor_Stoian]

Hi,

having a nearly square room (16' x 14' 8" x 7' 6"), i was wondering if making it perfectly square and (14'8" x 14' 8"), with the layout as in the picture bellow, would be a better approach as using it the conventional way (facing the shorter wall)?
I'm using Dynaudio BM12A active monitors on stands and a SVS sealed subwoofer, my head beeing 38% from the back corner.

Thanx for your comments,
Victor

PS. the picture is from GIK acoustic primer, so Glenn i hope you don't mind.

[Ethan Winer]

Victor,

Square is worse than nearly square, so you should be going away from square, not toward it!

I usually recommend not facing a corner because that puts another corner behind you which focuses reflections toward you. If the wall behind you is flat, as in the drawing, it's probably not so bad. But I would not take a small room and make it even smaller by walling off half of it as shown!

This article shows the best way to set up in a rectangular room:

RealTraps - How To Set Up a Room

--Ethan

[Victor_Stoian]

Hi Ethan,

thanx for your response! I already studied most of your very informative articles.
Another question: according to M.Louden the best room ratio would be 1 x 1.5 x 2.1.
The length by height of my room gives 2.1.
Would i benefit from placing a new wall so that the width by height gives 1.5, again making the room smaller?

Cheers,
Victor

[gullfo]

it would probably help to construct boundary walls to alter the dimensions to get a better ratio. you're current room is likely to have many mode problems. maybe it would help to see a room layout.

[Ethan Winer]

Originally Posted by Victor_Stoian

according to M.Louden the best room ratio would be 1 x 1.5 x 2.1.

There's no such thing as a "best" ratio, and the size of the room is a factor too. I agree with Glenn that posting a layout is in order if you'd like our best advice.

--Ethan

[Victor_Stoian]

as i wrote in the first post, my room's dimensions are 16' x 14' 8" x 7' 6" (4.9m x 4.5m x 2.3m). It's in the basement and all walls, floor and ceiling are made of concrete (beton). There's a window 1m x 1m, on the right wall, and a door on the left wall, in the corner behind me:

--------------------
| ----------------- |
| ----L--------R--- |
| ----------------- w
| ----------------- w
| ----------------- |
| ----- desk ------ |
| ------ me ------- |
| ------------- S - |
D ----------------- |
--------------------

I'm sitting at 38% of the room length, from the back wall, the speakers aprox 6' away. I moved the sub (SVS SB12) around and used RoomEQWizard to see how it performes. I ended up with the sub in the "S" position. The bass response has a peak at 34Hz, that i reduced by 4dB with the PEQ on the sub. There's another peak at 68Hz (about 4 dB) that i left alone.
But the bass is not the problem - i have 3 nulls: -12dB at 113Hz, -15dB at 157Hz and -35dB at 227Hz.
I have 3 corners covered floor to ceiling with 7" thick hamp, 4 foam corner traps (floor to front wall corner) and 6 (1m x1m) basotect absorber for the RFZ.

Thanks again for your time,
Victor

[Græmatter Audio]

Guess I would do something like this - and have done, with results that are as good as can be expected in a conventional rectangular room this small.

I'd do conventional 2'x4' 16" OC + drywall on both sides and insulate to "soften" the side boundaries (compared to the concrete block,) create the desired ratio, provide the means to run electrical, and remove the asymmetrical window from the equation while providing better isolation from the outside, meanwhile creating 2'8" wide "Utility Hall" for storage, noisy CPU, etc. I'd not bother to put drywall on the "hallway" side of the new wall - just cover the insulation with fabric. If you want a wider "hall" 1:1.4:2.1 for the main room could work as an alternative.

Treat first reflections on side walls & ceiling with less dense stuff - and get as much stuff onto the front wall and corners + rear wall behind you that's as efficient in absorbtion down to the lowest freq. that you can find... you are going to need it.


G.

[gullfo]

just curious, why this seating/monitor arrangement? how far are the monitors from the front wall? what type of monitors are they? does your desk prohibit putting the monitors up to the front wall and having your seating position 38% from the front wall instead?

[Victor_Stoian]

the monitors (Dynaudio BM12A, ported) are 3' far from the front wall and i am sitting 6' away.
Don't want them near the wall. If a go 38% from the front wall, it'll be too close. I had them placed like that.
I like it better now, it's more "spacey". I can move my head around (a couple of inches) without having the "center" jump to the left or the right monitor.
Do you think that my nulls would change?
Ehtan is recomending both 38% (front or rear wall), saying "you can get the same benefit by sitting 38 percent of the room length when measured from the rear wall."

Victor

[gullfo]

i'm more concerned about the SBIR by having the monitors so far out from the front wall. i would recommend just trying it with the monitors up to the front wall and seating 38% from the front wall and see what happens.

[Glenn Kuras]

Originally Posted by gullfo

i'm more concerned about the SBIR by having the monitors so far out from the front wall. i would recommend just trying it with the monitors up to the front wall and seating 38% from the front wall and see what happens.

Glenn I think you are on to something. He may want to so put a panel behind each speaker and also put some thicker panels flat on the back wall.

Glenn

[Victor_Stoian]

38% from the front wall puts me 6' from the wall.
The monitors are ported on the rear. I read somewhere that such monitors should be placed at least 1'-2' away from the wall. That leaves less than 4' distance between me and the tweeters - thats too close for me.
This is why i chose the 38% from the back wall, so the monitor's back is 2' from the front wall and my head is 6' away from the front of the monitors.
Actually, my room setup is almost like the GIK Room Kit 2, except for the monster bass trap, beeing stereo (not surround) with desk (no couch).

V.

[Græmatter Audio]

Originally Posted by Victor_Stoian

38% from the front wall puts me 6' from the wall.
The monitors are ported on the rear. I read somewhere that such monitors should be placed at least 1'-2' away from the wall. That leaves less than 4' distance between me and the tweeters - thats to close for me.
This is why i chose the 38% from the back wall, where the monitor's back is 2' from the front wall and my head is 6' away from the front of the monitors.

V.

This is sort of the heart of the issue - your monitors may be overkill for the room.

At the moment your in the position of being forced to choose between imaging and freq. response.

My answer to that problem was to get EMES Blacks (Good overall performance, but more importantly - point source imaging at 3 ft. and under listening distance.)

Of course every room is different - and requires individual calculations for speaker/listener position and modal response ... but there does a appear to be a commonality among rooms this small, namely that modes tend to be more densely packed in the 100-200 Hz range, and more widely spaced at under 100Hz ... meaning that having a good dimensional ratio is critical to getting what modes are present under 100 Hz to "play nicely together." Yes, lots of bass trapping will still be of benefit (and necessary both to dampen the remaining peaks and nulls and to bring overall LF decay time down) but point is if you can get the speaker/listener positioning and SBIR working for you instead of against you, then bass-trapping & a well setup subwoofer system will be the icing on the cake rather than band-aids.

Unfortunately best placement may also mean listening distances of under 3 ft. - and this appears to be true for you regardless of whether you move your speakers closer to the front wall or not - and will still be the case if you alter your interior dimensions.

That's not to say that you might not be able to find an acceptable compromise through experimentation (clever use of the subwoofer may aid in this respect.)

G.

[Victor_Stoian]

Originally Posted by Græmatter Audio

your monitors may be overkill for the room.

What do you mean exactly with "overkill": are the monitors too big, too loud? or maybe the opposite?
What is the problem with my monitors?

V.

[Glenn Kuras]

Actually, my room setup is almost like the GIK Room Kit 2

Yea that set up is more for a home theater and uses the back 38% of the room (most of the time) because of screen size. You may want to try to place some thick absorption behind you to see if that might help.

Glenn

[gullfo]

for the sake of trying... could you check the polarity of the monitors? it could be one of them is reversed which is why you experience the sharp change of center. also, i'd recommend you put them up to the wall (1-2") and place them about 7' apart and then sit at 6', and angled them to a focus point at about 7'. let us know if this changes things.

[Victor_Stoian]

Hi Glenn,

as i wrote in post #9, i already had the monitors placed that way.
As i work with 3 computer monitors on my desk, the distance between the speakers was more than 4' (as far my head to the speakers was). Also half of my "sight" to the woofer was covered by the computer monitors - i didn't had the stands at that time.
I could try it again - when i'll find some spare time.
For sure, i'm gonna try the thick absorbtion Glenn Kuras mentioned.

Thank you all,
Victor

[Græmatter Audio]

Originally Posted by Victor_Stoian

What do you mean exactly with "overkill": are the monitors too big, too loud? or maybe the opposite?
What is the problem with my monitors?

V.

I was referring mainly to their size ... the greater physical distance between the woofer and tweeter in larger monitors will to some extent dictate the distance you must sit away from them in order for them to act as a point source of sound - inside of this distance as you move your head around the differing distance between the woofer and tweeter to your ear will have a tonal impact on the range of frequencies around the crossover point where the two drivers overlap. On the typical two way system, this is around 1500 Hz, which is a rather critical range usually containing key mix elements.
This phenomenon could've accounted to some extent for the dissatisfaction you were experiencing with the conventional 38% from the front wall arrangement when you tried it before.

OTOH the BM12's aren't exactly overpowered - really the only thing the extra size seems to be getting you is a little more low freq. extension compared to the smaller speakers in the range which would be more than capable of sufficient output for the room (especially in conjunction with a subwoofer system) while providing a touch more flexibility in terms of good imaging with closer placement.

There's no inherent problem with the monitors themselves assuming they're used within the range of conditions they were designed for.

Anyhow this might all turn out to be a non-issue afterall - see below ...

G.

[Græmatter Audio]

Originally Posted by gullfo

... also, i'd recommend you put them up to the wall (1-2") and place them about 7' apart and then sit at 6', and angled them to a focus point at about 7'. let us know if this changes things.

This looks like it could work out well ... might need to compensate for the overall lift in low-end due to boundary proximity? The other factor that may arise is that to get the greatest benefit in terms of freq. response with this arrangement it looks like you would end up with the speakers spread a bit wider than what's ideal ... though you could use that spot (about 3 feet from the side walls, against the front wall) for the subwoofer/s and this might help to fill in the nulls under 120 Hz that may still be a problem with the suggested positioning (which looks to be fine for imaging barring other factors.)

G.