John Sayers' Recording Studio Design Forum

Hi Glenn,

i really really appreciate your help... your designs gave me new motivation to start this... thanks for that...

i changed the sketchup a bit and added side absorbtion as well as angled the front wood baffle a bit (is this ok acoustically?)

because i really am in the critical planning phase right now... do you recommend a certain soffit design? i wanted to go with johns shelf design but i dont know if i can get my speakers (or the whole mdf box) decoupled enough with that... they weigh 36 kg each...
have to try thick sorbothane maybe... any special hints or tricks?

and do you think my dominant room modes are being trapped enough with only porous absorbtion in the back of the room and the hangers in the soffit front?
and can you determine which frequencies to absorb with hangers ? ( maybe distance to each other or varying angles....) ?
because im really scared that the modes are not trapped enough in the end, because i can´t really treat the room corners...

i know... so many questions...

please help me once again

i wanted to attach the .skp but its 6 mb now... i dont know how to reduce file size....

so only 2 pics

Thanks in advance

Cheers

Andi

anyone?

glenn do you think this is ok?

Thanks

Andi

Andi, your basic idea seems OK, but the speaker geometry doesn't: it looks like your listening position is in the exact middle of the room, which is bad. You could fix that by adjusting the angle of the soffits a bit, pointing them a bit further forward.

well, you CAN do that, but it looks like you might be creating problems fr first reflections like that. Why do you need that piece tilted down?

No since that will only treat the 1,0,0 mode (and harmonics), and maybe some tangentials and obliques that happen to involve those walls. One of the best treatments for modal issues is bass trapping in the tri-corners, or in as many other corners as you can.

Why not? There are twelve corners in a rectangular room, and you seem to have access to several of them...


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

thanks for your reply stuart...

i cant really treat the corners because there are doors in each corner and they have to stay usable...

i really would like to place faaat hangers there but thats not happening unfortunately...

You have doors in your ceiling and your floor?

Like I said: there are TWELVE corners in a rectangular room (count them). Only four of those are vertical. All the rest are horizontal, and most of them are available to you. Think about it....


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

ok, how much is a "bit"?



i just thought it looks better but acoustics go first... any other suggestions?




ok then i will built some chunk-style soffits on the side wall- ceiling and rearwall-floor and rearwall ceiling?



thanks for the math

ok now my reply is readable... i am not yet used to the quote function

Theoretically, a good place for your listening position is 38% of room depth. In other words, 38% of the distance between the front wall and the back wall. That's where you want your EARS. So you aim the speakers such that the acoustic axes just touch your ears, and intersect a few inches behind your head, at an angle of somewhere between 60 and 90 degrees. But you don't need to go crazy trying to get your ears at exactly 38% of the room depth: it's just a rough guideline. What you DO want to do, is to make sure that your ears are not in the exact middle of the room: that's a bad place to be.

Well, you CAN tilt it, if you want, but you just need to make sure that it is not creating first order reflections. The concept of an RFZ design (like yours) is just that: no first order reflections without at least 15ms. So if you can't find an angle for that panel that eliminates reflections, then you could replace the hard panel with absorption: Put a piece of 703 there, with cloth stretched across a frame in front of it, for example.

Sounds like a plan! One easy thing you could do is to just tilt your entire rear wall forwards, and fill it with absorption (maybe wrapped in plastic, to keep the highs in the room). That would give you a lot of broadband bass trapping at the rear, and would look good, too! Or if you don't want to tilt the entire wall, then just tilt the top half: same effect.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

ok i´ll try to achieve that...



so this middle part doesnt have to be reflective? ok cool so i´ll angle it the way it is in my model and make it absorbtive... ?




i will put 4 or 5 big diffractals in the big frame of the rear wall so this is for letting the room a bit alive... but the thing with the angled rear wall is cool. i think i´ll combine the diffusors and rear soffit/wall... somehow..



btw do you know how to make sketchup files a bit smaller for uploading?

mine is 6mb so far...


BiG thanks

Andi

i checked again and im not in the middle of the room, im behind the middle... is this bad or better than the middle? room is 6 metres... listening position is 3.44 measured from the front wall (concrete / not soffit mount wall)

i don´t know what to think about angles above 60 degrees... i´ve never seen it and i don´t really wanna try it either

damnit im stuck here... what to do?

please help me guys...

THanks

Andi

viewtopic.php?f=12&t=10511&p=75426&hilit=speaker+angle#p75426

viewtopic.php?f=1&t=287&p=1726&hilit=speaker+angle#p1726

viewtopic.php?f=1&t=3375&p=23601&hilit=speaker+angle#p23601

viewtopic.php?f=3&t=782&p=5711&hilit=speaker+angle#p5711

viewtopic.php?f=1&t=975&p=7345&hilit=speaker+angle#p7345

viewtopic.php?f=1&t=8283&p=62475&hilit=speaker+angle#p62475


We are! We are giving you solid, sound, good scientific and acoustic help. Just because you have "never seen it" doesn't mean that it is not correct....


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

ok thats totally new to me

thanks stuart i really appreciate your help!

what about sitting more in the back of the room than in the front? my seating point is 42% from the back of the room...

is this bad? if yes i will IMMEDIATELY change the design to achive the 38%

Thanks

Andi

before you do that. you need to be inside of the 60 degree cone, not at the tip. so if you're at 42% of the room length that will probably be fine. also, the massive soffit you are building, the room modes will be forced into behaving differently and the absorption behind that will temper the original modal response so the soffits response is dominant.
i'd extend the slats on the first angled walls on either side to the full length. then the small angled wall totally absorptive, and then the second angled walls - wider slots but still a slat wall.

_________________
Glenn

Glenn, he's talking about 42% from the BACK wall, ie, 58% from the FRONT wall. Not so fine, I think.

Andi, the other thing you could do if you don't want to change the speaker angle, is to move the speakers a bit closer together, which means reducing the size of your center panel. That will also bring the listening position closer to the front wall.

And as Glenn already mentioned, you want your EARS at the 38% point of the room, NOT the apex of the triangle. Since it is your ears that actually do the hearing, they need to be at the location in the room where the modal issues are least serious, which is theoretically 38% of the room depth (and also 62%). The apex of the triangle will be at some point BEHIND your head, since the edges of the imaginary triangle should obviously go through your ears, not your eyes!

So, just to repeat the geometry thing again, for clarity: Draw lines along the acoustic axes of the speakers (not the center-line of the speaker: the acoustic axis), such that the lines just touch your ears at 38% from the front wall, and intersect a bit behind your head. The point where they intersect isn't important: the point that matters is where your ears are.

Once again, 38% is NOT written in stone! It's a rough guideline, a starting point. If you think about it, even moving your head a bit or sliding your chair a little bit will change you far away from the 38% mark anyway. Plus, it seems like many engineers like to be a bit closer to the front wall than 38%. So don't worry about it too much: just make sure your ears are not at 50%, or some other "bad" point in the room.

And as Glenn also pointed out, with large soffits like yours (which is GOOD!) that changes the modal behavior of the room too, most likely pushing the theoretical perfect "38%" point to some other location in the room anyway. So don't sweat it too much: go for ball-park, and you'll find the actual sweet spot once the room is built.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.