Stuart's Insanity Studio: Design phase

[WayneD]

You're welcome Lou! Thank you sir!

Just thinking out loud here, maybe stir the thought pot a bit, but....

Could Lou's angle be greater as he is seated closer to the front wall? Is Lou's seat 38% of the front of the room? If, and I don't recall if it was ever stated, he is closer than 38% would that account for his speaker/soffit angle of 12deg?

Lou, are you speakers 90 or 60 deg in layout? How does stature fit into the equation? I am sure ceiling height also fits into this too. The relationship of speaker position, ceiling height, room size and physical height. Studiopeople measured Lou all up. If we looked at all his measurements, we could correlate those things together. You would think. Anyway, I may have gone off the deep end here but thought I'd throw this in the mix.

W

[Soundman2020]

Thanks Lou, Wayne, André, et. al.! Yeah, I guess you guys are right. I'm actually going to do that "Lou Blind Listening Test" on the weekend, and see what it it does.... Good idea.

Hmmmm... Lou, do you think it will make a big difference if I substitute "Pisco Sour" for "Beer" in your test protocol? I do want to be accurate about this, you know...

And in the interests of trying to solve the angle mystery, I just wrote to both Genelec and Adam asking for their technical advise on soffit mount angles, and why. Adam USA responded immediately, saying they had passed on my request to the guru's at Adam Germany. No response from Genelc yet. ( But I only sent it ten minutes ago, so I guess that delay is excusable! ).

Anyway, I'll summarize the responses here, when I get something.

------------------------------------

OK, next question: Do my soffits need to go all the way up to the ceiling, or could I use the very top area for bass trapping?

Next, next question: Does the space behind the soffit have to be sealed airtight? (I know the box that the speaker sits in has to be airtight, but what about the rest of the space, around the box?)

- Stuart -

[WayneD]

Stuart, from what I have been reading and seeing so far, the box is sealed and the remainder is open. I believe the space is filled with rock wool or other type as needed. I've seen the bottom open but can't recall the top. Maybe check in the speaker forum? I remember a dude named Gareth I believe had a nice design set going on. Check Lou's pics too. What a wealth of info that thread is. It really opened my eyes. Too bad Rod's book doesn't cover these little things.

W

[Soundman2020]

Too bad Rod's book doesn't cover these little things.

Yeah, good idea!

Rod? Are you listening? How about a "Volume Two", dealing with all these numerous little extras? We sure could use it!

[AVare]

Just to add interest, I checked the tonmeister tonmeister SSF_01_1_E_2002_v2a document. It specifies 1.2 m as the height for front speakers. No inclination angle. For surrounds 1.2 m as nominal with up to 15° downward angle. this is not a detailed question about surround sound. Surround sound is based on solid front speaker location PLUS surrounds.

Andre

[Soundman2020]

Is the quest over?

OK, I have a reply from Genelec, and their reasoning for the 20 degree max angle is a totally different track from what we were thinking, and something that's pretty obvious and we all forgot! Reflections off the console! Duh! I KNEW that! So how come I never thought of it?

Quote: "If the angle goes beyond 20 degrees, the amount of first reflections over the console or work surface increases dramatically, generating disastrous comb filtering effect and ripples in the in-situ measured response."


Well there ya go! Sounds like good solid reasoning to me! They also mention that they arrived at this limit from empirical measurements of hundreds of control rooms around the world: Nobody builds control rooms with more than 20 degree angles, apparently.


They also sent me some very interesting documents, which I'm working through right now.

But "console reflections" seems to be their reason, and that sounds spot-on to me!


- Stuart -


(PS No reply from Adam Germany yet.)

[Soundman2020]

Say, André! Maybe I've found why you had that figure of "7 degrees" on your mind?

In a document on 5.1 speaker placement that Genelec sent me, I came across this intriguing paragraph:


"However, as mentioned above, the resolution of the ear/brain in the vertical plane is about 3 degrees above ear level horizon and 3 to 10 degrees below ear level horizon. Precisely because of this behaviour of the ear/brain, our vertical localisation tolerance is about 7 degrees. Within these 7 degrees, there is a localisation blur (inaccuracy in positioning a sound source) in the vertical plane. This allows two sources to be positioned at slightly different heights without the brain noticing the height difference. This useful human hearing limitation can be exploited when planning the centre channel position, for example. Some tolerance in loudspeaker height can be allowed, and this without disturbing the engineer who is doing multichannel work and panning sound sources across the L-C-R loudspeaker array."

Basically, what they are saying there is that you can have your center speaker up to 7 degrees higher than your L and R speakers, and not notice the difference.


Maybe that's the seven degree thing? A difference in height corresponding to a 7 degree angle, rather than an absolute angle of 7 degrees?


- Stuart -

[Soundman2020]

Wooohhooo!!! Thank you Genelec!

A few paragraphs further down, it says:

"The ITU is quite strict on the identical height positioning for the three front loudspeakers, however it gives some allowances for the surround loudspeakers. They can be placed higher than the front loudspeakers, and tilted down towards the listening position up to an angle of 15 degrees."


and then:


"The Japanese HDTV Multichannel Sound Forum specifies that, “…All loudspeaker axes should be placed at the same height between 1.2…2.0 m, more than 1.2 m is recommended…”

Hmmm... that's interesting. MORE than 1.2 m is recommended, and up to 2 m? Very interesting!


But then comes the kicker:


"This is an important guideline but acoustically when using large loudspeakers the interaction with the floor (below 400 Hz) and the first reflection cancellation (typically between 100 Hz…200 Hz) can be very serious if the loudspeakers are placed too low and close to the floor surface. As seen in stereo control rooms, the overall height of the loudspeakers is dependent on the room geometry and the listening distance. The larger the loudspeakers the further away from the floor they should be placed to reduce cancellation phenomena. Furthermore, in standard stereo control room construction, studio designers always observe the accepted rule that the main loudspeakers should not be placed higher than 15 to 20 degrees from the ear level horizon. For our brain, if this loudspeaker vertical angle is higher than the above recommended values, the aural and visual coherence becomes inaccurate in our perception."


Bingo!!!! I think that pretty much settles it.

[Lou]

Stuart Quoted:

studio designers always observe the accepted rule that the main loudspeakers should not be placed higher than 15 to 20 degrees from the ear level horizon. For our brain, if this loudspeaker vertical angle is higher than the above recommended values, the aural and visual coherence becomes inaccurate in our perception.

Hang on a minute!

Stuart Wrote:

Bingo!!!! I think that pretty much settles it.

Not quite – Here’s an opinion as to why. I just want to make sure here that everyone who is following this is totally clear about the angle issue, and much more importantly, to which angles we are referring.

I’ll try and explain as best I can. I‘ve just literally thrown these sketches together, but I hope it makes my reasoning clear.

The first image is of course what we’re all used to before we start raising monitor heights. The monitor is pointing directly at the ear, or if you prefer (horizontal) Zero degrees.



The second image places the monitor 10 degrees above the horizontal, and clearly the ear would struggle to perceive what’s happening accurately, because as Andre said, and the above quote agrees, “aural and visual coherence……………..blah blah.”



Finally – if the monitor is tilted forward by 10 degrees then listening accuracy is restored.



So chaps, when we’re all talking about soffit angles, let’s make sure we’re all talking about the same ones. By that of course I mean the fact that both images 2 and 3 above show angles of 10 degrees, yet would give completely good and bad results!

Hope this helps anyone confused by all this!

Regards,

Lou.
(btw - I know the monitor in image 2 is drawn too high, but even if you visualise it with the dotted line going to the centre, much of the sound would still be above ones head! I was in rush sorry.)

[lilith_envy]

Nice diagram,
I think wayneD was pretty right in saying it has alot to do with the room size.
Wouldn't like to put a "one size fits all" angle as gospel. But as long as your comfortable with your final choice

[WayneD]

Thanks lilith_envy, it just seemed to make sense that if you are set back 38% in a 20 foot length room, you would have less of an angle as there is more room. Therefore, there could be less angle. If you cut that distance in half, you are now closer to the front wall (as in Lou's room, sorry Lou, your example was well documented and therefore sticks in my mind). I would also think that height of ceiling would have a direct effect on the placement as well as the angle. I see myself having to deal with just that problem in my space. I haven't nailed down any designs yet, but the fron half of my room is 6'-10" and the rear is 9'-4" plus or minus. So this whole angle and placement discussion is critical to my learning and understanding.

W

[Soundman2020]

Reading more on the stuff that Genelec sent me: They did an in-depth survey and analysis of 164 studio control rooms around the world, and came up with very interesting results:

(I'm summarizing here)

59% use soffit mounting for their speakers (the rest use free-standing)
85% have the speakers mounted ABOVE the recommended 1.2m height
Of those with speakers mounted above ear level, 62% are tilted down.
The angle of tilt is up to about 15 degrees, commonly, 20 degrees max.

The reason for placing the speakers above 1.2m is to avoid or reduce notches in room response in the 80-120 Hz range, which is associated with a mode for 1.2m speaker height.

About one third of all the controls rooms they analyzed had notches in this range, with most of them centered around 100 Hz.

There is more interesting stuff on there, but I thought it was interesting that the vast majority of rooms have tilted speakers mounted above ear height, with angles approaching 15 degrees.

I'm feeling a little bit more comfortable now! I might even venture to raise my speakers a little and tilt them another couple of degrees, as that would help my design.


- Stuart -

[AVare]

Nice research!

"The Japanese HDTV Multichannel Sound Forum specifies that, “…All loudspeaker axes should be placed at the same height between 1.2…2.0 m, more than 1.2 m is recommended…”

Hmmm... that's interesting. MORE than 1.2 m is recommended, and up to 2 m? Very interesting!

Remember the source's primary interest is video. Where there is a conflict with video and audio monitors being in the same space, the video takes precedence.

But then comes the kicker:

"This is an important guideline but acoustically when using large loudspeakers the interaction with the floor (below 400 Hz) and the first reflection cancellation (typically between 100 Hz…200 Hz) can be very serious if the loudspeakers are placed too low and close to the floor surface. As seen in stereo control rooms, the overall height of the loudspeakers is dependent on the room geometry and the listening distance...

Speaker height is one of many factors in a good control room design. No kicker.

Andre

[Soundman2020]

Nice research!

Thanks! I guess you noticed that I like to have all my ducks neatly in a row beforr I'm satisfied!

Speaker height is one of many factors in a good control room design. No kicker.

I guess I should have been a bit more specific. The part that I thought was the "kicker", was this:

"... studio designers always observe the accepted rule that the main loudspeakers should not be placed higher than 15 to 20 degrees from the ear level horizon. For our brain, if this loudspeaker vertical angle is higher than the above recommended values, the aural and visual coherence becomes inaccurate in our perception."


So, summarizing again, it seems that there is a "de-facto" limit of 15 to 20 degrees, and that there are many inter-related reasons for the limit, including at least these three:

1) Ear response (frequency curve) for sounds coming from above.
2) Reflections from consoles / work surfaces.
3) Aural / visual coherence.

Remember the source's primary interest is video. Where there is a conflict with video and audio monitors being in the same space, the video takes precedence.

Tell me about it! My company sells and installs high-end video editing / effects systems, and I'm always astounded at how little they care about the audio in their suites! They can have a million dollar editing system in there, with top-of-the-line video monitors, state-of-the art HD-SR VTRs, really cool furniture, fittings, lighting etc. And a pair of US$ 100 speakers on the floor, under the desk, behind the operator's feet.... Go figure....

(And don't even mention the acoustics in those rooms... I think my bathroom sounds better than most editing suites.)

OK enough of that for now.

<< RANT-MODE = OFF >>



- Stuart -

[WayneD]

The interesting note here is "studio designers always observe the accepted rule that the main loudspeakers should not be placed higher than 15 to 20 degrees from the ear level horizon."

Now we know why they ear height when sitting. The ear height measurement, against the height dimension will then allow you to figure the placement angles. What is the recommended distance to stay away from the ceiling? I have been in studios in NY that have them almost to the ceiling and angled down alot where the room is wider than it is deep.

Nice work Stuart!

W