soffit mount design

[monstertraxstudio]

ok. so the sub sitting in the offset center behind the console wont react with the console firing under it at my feet? a bass port effect? Why is it necessary to have large holes in the couch platform? Now that you have given me direction on the placement of my chair and monitor heights and placement, what do you think about the cloud? necessary with a 14' ceiling? if so possible locations and heights from the ceiling. Wish i had a program that showed the speakers firing out and showing intersecting points for deflection and absorbtion....

I appreciate the time you spend with me on my project, i still havent heard back from John.

[Soundman2020]

the sub sitting in the offset center behind the console wont react with the console firing under it at my feet? a bass port effect?

It is a distant possibility, of course, but not very likely, unless you are playing your bass at extreme levels that just happen to coincide with the dimensions of the space under your desk, and also your desk is sealed to the front and side walls. I doubt it will be an issue.

Why is it necessary to have large holes in the couch platform?

Not in it: under it. I guess I expressed that badly. I meant on the risers, the vertical surfaces on the sides and front of the platform. You need those to help couple that air space to the room space, acoustically, so that you don't have a sealed drum head. It's like the difference between the sound of two identical kick drums: one is set up normally, with nicely tuned heads on both ends and nothing inside, while the other only has one head on it, has huge holes bored in the drum body, all the way around, and is also stuffed full of mineral wool: which one resonates more?

what do you think about the cloud? necessary with a 14' ceiling?

I would use a cloud if you have a first refection point up there, or if you have flutter echo issues in the vertical plane, or modal issues (in which case the cloud should be hard backed), or insufficient absorption on the ceiling without it, or to help establish an RFZ. There are many reasons why a cloud might be needed.

If in doubt, get someone to hold a mirror up on the ceiling while you sit in your chair at the mix position. Look up at the mirror and ask the person to move it around all over the ceiling. If there is any place where you can see the speakers reflected in the mirror, then you need a cloud. Also if the ceiling and floor are parallel and both are flat surfaces, then you need a cloud. The modal issue you'd only be able to detect with REW.

But at a guess, you probably do need a cloud of some type.

if so possible locations and heights from the ceiling.

The location is easy: directly above the area between your head and the speakers, and big enough to cover all the places where you can see the speakers in the mirror, plus a margin around that area of maybe a foot or so. But the height is not so easy to predict,and neither is the angle. One good plan is to hang it on chains from hooks, so you can adjust both the height and angle by lengthening and shortening the chains. Normally you'd want an angle of maybe 12° or so, but once the room is finished you can play around with that until you get the best sound. REW analysis will also help determine if it needs a hard back or not.

Wish i had a program that showed the speakers firing out and showing intersecting points for deflection and absorbtion...

Me too! That would be great if there were an application especially for that. The way I do it is with SketchUp, creating lines at various angles, vertically and horizontally, seeing what surfaces they hit, measuring the angle, then projecting the "reflected" lines at the correct reflection angles, and seeing where those go, etc. It's called "ray tracing", and I do all that manually. It takes a lot of time, and it would be great if there were a plugin for SketchUp to do that for you. There are ray-tracing programs, but they do photo-realistic rendering, which is not really what you need.

i still havent heard back from John.

He's probably tied up on one of his big projects right now. Try again, and if you don't hear back then PM me.


- Stuart -

[monstertraxstudio]

Is mineral wool preferred or can i use r-19 insulation like in all my walls? For a good starting point on the cloud, would a 2x4 frame, whatever the size i need, covered with speaker cloth or some other breathable fabric with 703 in the cavity be aceptable or is the depth important too? How is this determined? IM thinking about some small eyeball led cans in the cloud, for my mix position lighting on a dimmer might be nice.

Is rew a free program and how best it it ran. in my un finished room or wait until i have drywall, paint and my 703 absorbers and treatment where i think it should be based on the mirror testing? I dont want to get the cart before the horse nor do i want to be pre mature.

My walls are framed at the dimensions you suggested with Louden or very close. Im ready to bulld speaker enclosure art deco....when i hear from Mr. Sayer. Im ready to install wiring and cabling and set the couch platform as you instructed. I would like to use mogami but the good cable from rapco is several dollars a foot cheaper, mistake?

[monstertraxstudio]

Stuart,

Im having trouble getting the speaker and seating locations to work. Im figuring 10'9" to listening position, center of room given the soffit protrusion of about 6-8" from face of front wall. if i calculate a 60 degree angle from me to the wall, it puts center of speaker 5'5" off the sides. your 1/3 is about 7'4" approx. Im using sketchup with the protractor. it puts 11'4" from me to each speaker and the same between speakers. What am i doing wrong. if i protract the 30 degree angles off the face of the front wall to the listening position it puts me at 7' out or so?????

Remember my room is 22' wide currently, you recommended 19' for a perfect louden room. can we compromise with 20'6" after double 5/8" rock? construction is easier that way. what extra treatment would be required? etc...

[Soundman2020]

Wow! Lots of questions there, all at once!

Yes, room geometry has a habit of not cooperating with acoustic requirements! That's part of the "fun" of studio design: things never seem to work out, and you have to fiddle with them constantly, trying to get them to make sense. Don't forget that there is nothing written in stone here: those numbers are all guidelines, not legal demands! You can change them a bit, move things around to try to improve the layout.

I'd go with the setup that gets your head positioned roughly right in the room: on the center line, maybe 35 to 40% front to back, give or take. Then angle out 30° each way from the center line, centered on a point about a 6" to 12" behind your: your speakers will be located on those lines, so sort of slide them back and forth on those lines until the are about 7' or so from your head, and far enough away form the front wall that you can get soffits around them.

But you can tweak all of the dimensions and angles to optimize the layout. And if the room seems out of proportion at the front, visually, then you can also angle the front part of the side walls a bit more, up to the soffits, to improve that.


- Stuart -

[monstertraxstudio]

Thx. I understand. I think I'll go with the protracted layout putting the speakers a bit farther apart. Still on the 30 degree axis and 7 degrees down.

How about leaving the room 20' wide instead of 19'? Can treatment take care of the discrepancy?

Rod

[Soundman2020]

How about leaving the room 20' wide instead of 19'?

As long as you cut the length down to 26.6 feet, that would still be reasonable. Plus, if you design the room using the RFZ concept, then the splayed walls and soffits at the front will reduce the average width, bringing you closer to 19' wide. It's a decent sized room with a high ceiling, so it should be fine.

Can treatment take care of the discrepancy?

Yup! You'll need treatment anyway (and it looks like you'll have some issues around 60 Hz.) so that can be dealt with, to a certain extent.


- Stuart -

[monstertraxstudio]

what method of measurement are you using to determine the 60hz? splayed walls? mine currently are parallel? great stuff cant wait to get designing.

rod

[Soundman2020]

I'm using a simple room mode calculator for rectangular rooms, and just plugging in your values, then looking at the resulting modes to see if they are spread out evenly across the spectrum, or bunched up in places. There are several such calculators available free on-line, but I like Bob Gold's, since it gives you a whole lot of other info, besides just the basic modes.

However, those calculators only work for parallel-walled in six-sided rectangular rooms. If you splay the walls then the results are no longer 100% valid. A slight splay is not a problem, but the more you splay the less accurate it gets.


- Stuart -

[monstertraxstudio]

Im confused on splayed walls. I have parallel walls, floors on all 6 sides. with the exception of the 2- 45 degree walls in the rear of the room. one side is a utility closet and the other is the double door access. So does your calculator show were on the right track with the room design? Wife excited to get drawing and design started.

[Soundman2020]

Im confused on splayed walls. I have parallel walls, floors on all 6 sides. with the exception of the 2- 45 degree walls in the rear of the room.

There should not be any 45° walls in the rear of the room, as that would create acoustic issues with reflections getting back to your ears too soon, or too loud. The rear corners of the room should be used for bass traps, as that's the best place to put them.

If you could provide a sketch of the existing room as it is right now, before you do anything to it, then that would help to understand your situation better. The best way to do that is with the "SketchUp" program, from Google. And the best part of this is the price: it is FREE! Just download it from Google, run through a few of the tutorials on how to use it, and put together a sketch.

About spaying walls: The room should be narrower at the front, wider at the back. The side walls should be splayed at least 12° total (6° on each side). If that would make the room too small at the front, then you can just splay the front half of each side wall, and leave the back half flat. The ceiling should also be angled by at least 12°, and once again it is lower at the front, higher at the back, and you can just angle half of it (the front half) to avoid eating up too much room height.

- Stuart -

[Soundman2020]

Link to thread showing final, completed room, a couple of years later:

http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471

- Stuart -