John Sayers' Recording Studio Design Forum Archive

Ok - there are three ways to mount your soffits.

The first is the simplest which is as per my design at SAE and which we've further updated through drawings posted here in these forums. The idea is to make the whole soffit frame as rigid and solid as possible using double layers of MDF/plywood glued and screwed thus lowering the resonate frequency of the whole structure.

Does this mean that the speaker box does not need any rubber/neoprene material inside the speaker box decoupling the speaker from the box?

Does it also mean the it does not matter if the baffle is touching the box because the point is to make the whole thing so rigid that it should not vibrate at all?

The reason for the confusion is because of things like Simo's build where he made a very solid structure, then made sure not to have the speaker box touch the baffle or the finish piece of veneered MDF.

John's design appears to have the speaker box coming through flush and touching the timber finish and the box does not have any springy rubbery material inside, just a very tight fit? Is this correct?

Does this mean that the speaker box does not need any rubber/neoprene material inside the speaker box decoupling the speaker from the box?

For John's method, yes that's correct. It's a very tight fit.

Does it also mean the it does not matter if the baffle is touching the box because the point is to make the whole thing so rigid that it should not vibrate at all?

Once again, for John's method, yes it can touch.

However, you do need LOTS of mass and a very rigid structure to get good results here. So the front baffle will be at least a couple of centimeters thick, maybe more, and will probably need to be built up from two or three layers. The internal framing also needs to be tough, strong, rigid.

The reason for the confusion is because of things like Simo's build where he made a very solid structure, then made sure not to have the speaker box touch the baffle or the finish piece of veneered MDF.

Well, you always need a solid structure, no matter which method you use. But Simo also decoupled his, as far as I recall, using a variation on Barefoot's method. I may be wrong, but I seem to recall that he has the baffle decoupled from the speaker support itself.

John's design appears to have the speaker box coming through flush and touching the timber finish and the box does not have any springy rubbery material inside, just a very tight fit? Is this correct?

Right. You could use thin rubber if you wanted, to protect the finish on the speaker cabinet itself, but you'd need to make sure that you compress it enough so that it does not decouple, and holds the speaker firmly in place.


- Stuart -

Awesome thanks for the clarification Stuart!

I was planning on building the soffit baffles with a sheet of 3/4" MDF and a finish sheet of 3/4" Birch laminated plywood on top of that. Does this sound solid and thick enough to you?

I saw something similar to this on the forum but cannot remember who came up with it, I thought this would be good in case I need to remove the speaker for any reason. The plan is to have a removable bezel that frames the speaker and then the bolt down top on the box holding the speaker for easier removal.

The rubber on top is 8mm gym flooring rubber that I have left over from my workout room, very dense not springy at all, just figured it would be good to help protect the speaker. What do you think? One other question, from the floor to the lowest point on my front wall is 6'1", is this high enough to not cause any issues with the speaker soffits? The ceiling angles up to 8' as it goes back into the room.
I know I have to cut the bezel to match the odd front of the A8X's, just didn't go to the trouble in SU.

Almost done boxing in the duct work in the ceiling and finishing the soffit around the HVAC trunk line, will post pictures soon!

Could you also comment on my idea for the rear wall absorption, after some more research I decided it might be better to get rid of every other slat so the wall is not too reflective. Does this look like a sound idea idea to you "pun intended"

If I build the rear wall inside out I get 1'8" of absorption at the thickest point and 3.5" at the shallowest. The slats are 3.5" with 6" spacing between them.


Thanks!
Allen

I was planning on building the soffit baffles with a sheet of 3/4" MDF and a finish sheet of 3/4" Birch laminated plywood on top of that. Does this sound solid and thick enough to you?

That should be fine.

The rubber on top is 8mm gym flooring rubber that I have left over from my workout room, very dense not springy at all, just figured it would be good to help protect the speaker. What do you think?

Looks good to me. That should keep the speaker firmly and solidly attached to the soffit, but also make it easily removable. Good idea!

One other question, from the floor to the lowest point on my front wall is 6'1", is this high enough to not cause any issues with the speaker soffits?

Looks OK. If that's how low it has to be, then that's how low it has to be!!!

Could you also comment on my idea for the rear wall absorption, after some more research I decided it might be better to get rid of every other slat so the wall is not too reflective. Does this look like a sound idea idea to you "pun intended"

That does, indeed, "sound" like a very "sound" idea! In fact, you could start out with no slats at all, measure the room response with REW, then add a couple of slats at a time and check with REW after each addition, to see how it is doing.

If I build the rear wall inside out I get 1'8" of absorption at the thickest point and 3.5" at the shallowest. The slats are 3.5" with 6" spacing between them.

- Stuart -

Thanks once again Stuart!

Is there a major advantage to using 703 vs Roxul for the treatment, I have seen people face their superchunks with 703 and then use rockwool or pinkstuff behind, is this necessary?

What about the panel absorbers...

Thanks,
Allen

Alright! Finally finished beefing up and sealing the outer leaf! What gigantic pain in the --- that was! I laid out my walls and got the first built and temporarily tacked up last night.
Hopefully will be finished framing this week, going to try and do a little after work each night but we'll see how that goes. It's really HAPPENING!!!

Great work Allen!
I can't wait to be at that stage(framing inner walls)
"What gigantic pain in the --- that was! " Perfectly said!

New day, new wall.

I got the first angled wall built, I'm hoping to get the front wall and possibly the angled one on the other side done today too... We'll see...

I'm doing a double top plate as well, just have these tacked up temporarily to make sure everything fits right, then will bring them down add
the second plate and nail them to the slab.

Lookin' good Allen. Great to see that the beef-up is finally behind you. You did two layers of 5/8" beef correct? Are you already noticing a difference in the noise from upstairs? Any hindsight tips you noticed along the way?

Also I have a question for you on framing. What is the purpose of doing a double top plate and when would I choose to do it or not do it? Does one have to do it for code, or is it just adding to the structural capability of the wall that may be a factor if for example, you are framing your ceiling joists on these walls.

Many thanks for sharing and keep up the great work!

Andy

then will bring them down add the second plate and nail them to the slab.

Don't forget to caulk under the sole plate before you nail them down! Those seals are important... 3 beads of acoustic caulk along the sole plates: one down the middle, and the others about an inch each side of that. (If you can't get acoustic caulk, then any good-quality, non-hardening bathroom/kitchen caulk will do.)

Did I mention that seals are important?


- Stuart -

(PS. Don't forget the importance of air-tight seals!)

Hi Andy,

Yes its for the structure, I'm attaching the joists to the top plates "decoupled ceiling", actually as far as the inner leaf is concerned I'm trying to go a little above and beyond what is required by code for my own peace of mind and so hopefully I don't get harassed by the building inspector,
I'm so happy to be done with the outer leaf beef up!!!

Yes I did 2 layers of 5/8s everywhere. The biggest tip can think of right now is to pay somebody else to do the beef up!
There was definitely a difference in the noise from upstairs at each step, both in footfall and air born.
Stuart, thanks for the tip, I will definitely do that!

I have an HVAC question that I think I know the answer too but would love a confirmation. I was thinking of doing this for my return, but am I losing a bunch of isolation by not having the silencer directly attached to the inner leaf? If that IS the case I was thinking of putting a silencer in the floor joist above porting the duct straight out the back and buying one of these Fantech exterior mount fans to send the return outside. The one I'm looking at is a RVF 6 that is speed variable and does 381cfm. If I go the joist silencer option and I'm mounting it between the sub floor joist above, how do I decouple from the outer and or inner leaf?

Thanks!
Allen

Ok, almost done with framing, finishing up the ceiling joist right now and I have a question.

Is there any difference between angling the ceiling down towards the front wall for RFZ or hanging a hard backed cloud?

Based on my room size 16x14x8'3" even if I angle the ceiling am I most likely going to be adding a soft backed cloud for LF absorbtion anyway?

I planned on doing an angled ceiling and have the angle worked out already, but now I'm wondering if it's worth it if I can achieve the same RFZ design with a flat ceiling and angled hard backed cloud.

Thanks
Allen

Ok, finished the framing, will take and post some pics this weekend, I decided against the outside mounted fan for various reasons one of which being not wanting to cut a 6 inch hole in back of my brand new home. I believe that the drawing I did for the return with the silencer built in a soffit in the adjacent room is good, the only thing I want to make sure I got right is the neoprene on the vent in the gap decoupling the inner leaf from the outer leaf, just worried about sound escaping from there. For the soffit housing the silencer I am planning of building it out of double 5/8 drywall and filling loosely with insulation.

Thanks,
Allen

Ok,

Finished the framing! Starting to look like something now! I decided to go with putting the HVAC return silencer in the exercise room that is adjacent to the studio. The silencer will have a vent that penetrates both leaves which will be cut in the middle and wrapped with rubber and sealed to prevent flanking, as per one of Stuarts suggestions. I have built a soffit in the corner of the exercise room that will house the silencer and the a Fantech FG6 that will be drywalled but have an access panel for future serving of the FG6. The fan will be attached to the outlet of the silencer and then exhaust to a register in the soffit. I am going to wire a speed control for the fan into the studio.

Not sure why some of my photos are rotating when I post them, I tried rotating the and saving them on my computer to compensate for the rotation on the upload but they still rotate the same amount? Any suggestions?