Attic Shaped Studio

#481

Cheers Glenn, yes, 70 Hz is almost certainly the ceiling. Confirmed by noting changes at that frequency when I move the mic up or down. The ceiling is woefully under treated at the moment so there's huge scope for improvement. I'm thinking something like 200mm deep low density insulation over the entire flat part of the ceiling. Perhaps using inside out modules so the visual aspect of the ceiling doesn't drop too much.

50Hz and multiples thereof are the width modes. Also very under treated. I've been pondering several options for those. One is the tuned membrane panel from the BBC paper in the early 90s. I think it's about 150mm deep and has a thin metal face. Apparently it'll tackle 50Hz. Another option is "Boggy" type absorber / diffusers at the back of the room (away from influence on the mixing position) to improve ambience when recording drums there.

Cheers!
Jennifer

#482

i don't suppose you have an accurate sketchup model of your room? :-)

or detail measurements of it all on paper etc you could share with me. i have some basic treatments which may be something that can assist as well as the Boggy style diffuser units as dynamic components as we could experiment on what might work. i'm thinking you might benefit from my "twisted path" absorbers which use layers of MLV in the absorption packs to create longer air paths. these typically increase the overall path to boundary significantly without extensive depth or tuning.

#483

I've been discussing some improvements with Glenn. Once the speaker flush mounts are finished, the celling will be next. New absorbers are shown in light green and are 20cm deep low density fibreglass.

The plan is to install four inside out modules in the ceiling for two purposes;

1) Raise (most of) the ceiling from 230cm to something higher, perhaps 260cm. This should get ears further away from the acoustic bad things that happen halfway between boundaries, and perhaps improve the recording acoustics, especially for drums.

2) Installation of deep absorption without lowering the visible height of the ceiling. I could do this on the existing ceiling but it would bring the visible height close to 7 feet, a bit too cramped feeling for my liking.

Construction will be similar to the recessed absorbers I installed at the rear of the room with an outer layer of OSB and an inner plasterboard layer. Hopefully it easier because they'll be half as deep and don't need to be cantilevered like the rear ones.

The joists close to the sides of the room are twinned and tripled with only a narrow gap between them, so the two absorbers at the sides will be installed on the existing ceiling. This will also allow them to reach fully into the corner above the soffit baffle where I think specular reflections are coming from.

Of course, I may remove the ceiling plasterboard and find the plan isn't possible because of some obstruction or other. Let's hope not, especially as I'll be left with a large stack of superfluous plasterboard and OSB sheets in the garage

Cheers,
Jennifer

#484

they make fiberoptic snakes you can use with your smartphone so you can drill a small hole and peek around. the one i have has a built-in light and is 10m long... and of course you can take snapshots etc.

#485

gullfo wrote:Source of the post they make fiberoptic snakes you can use with your smartphone so you can drill a small hole and peek around. the one i have has a built-in light and is 10m long... and of course you can take snapshots etc.

Thanks Glenn, I have something similar, bought to make a similar investigation before I did the "behind the wall" work for the absorbers at the back of the room and the HVAC silencers at the front. Unfortunately, all it saw was a very deep bundle of loft insulation :lol:

I'll give it a go, and then remove a hatch sized rectangle of plasterboard to see what lurks beyond. Should be very easy to repair that if nothing can be added.

Cheers,
Jennifer

#486

It's been a long time since the last major update, and now it's time to build these inside out ceiling modules as previously discussed with Glenn.

The current floor to flat ceiling height is 230cm. If possible I'd like to build these 30cm deep to raise the ceiling to 260cm on the inside of these modules. This will allow ceiling absorbers made from 20cm deep low density insulation plus a 10cm air gap above this while preserving a visual ceiling of 230cm.

Acoustic advantages should be:
1) Absorption to reduce the effect of some room modes and specular reflections.
2) My ears (let's say 120cm from ground) will be vertically less central.
3) I often record drummers in the back of this room, and sometimes vocal groups. Both will benefit from the higher ceiling.

In theory these should be relatively simple to build, but might be made more complicated by the purlin beams I've highlighted in orange on the house plans. If the purlin beams prevent the full 30cm depth I'll have to build the boxes so they go around them. The truss structure in the eaves is nothing like the plans though, so who knows what I'll find when I remove some plasterboard tomorrow

Cheers!
Jennifer

#487

I removed a rectangular panel of of the ceiling plasterboard to see what lurks above. Nice to see the insulation was done well

The purlin beam towards the rear of the room is in the place indicated by the plans. Assuming the beam toward the front is symmetrically placed there will be about 600mm gap between them. The ceiling joists are 150mm high, the purlins sit on top of those.

At the moment I see two options:

First would be regular inside out modules with sloping ends of almost 150mm height. These could stretch almost the entire length of the flat portion of the ceiling. To get 200mm deep absorption would mean 50mm of the absorber visible below ceiling height. This would be fine. The big upside is these will be relatively simple to build. The downside is the ceiling would become 245cm high, which means my ears at the mix position are almost central.

Second would be to build the modules 300 high as initially planned, but include cutouts so they go around the purlin beams. The upside is the ceiling will be 260cm above the mix position, less central for my ears than the first option. It will also allow deeper insulation or an airgap, therefore better absorption. Downside is they will be more complicated to build, especially as they have to be sealed and have two layers: One OSB for structure, then plasterboard for appearance and building code compliance. Lots more cuts and seals than the first option. I'll have a think about this.

Cheers!
Jennifer

#488

the first option would be easier because option 2 would require you cut away enough ceiling to layer the rafters with the osb/drywallvapor barrier etc in it's entirety w/ the benefit of overall more air space up there and then recovering the ceiling with openings for the LF - typically in the middle and sides for strongest mode entry.

step one would be to snake your camera up there and look around :-)

#489

Thanks Glenn, I'm definitely leaning toward option two. In for a penny, in for a pound. The camera is a good idea, I used a drumstick to poke around that insulation to determine the location and size of the purlin, if I can get the camera above the insulation it should hopefully give a clearer picture of any other possible obstructions.

You reckon directly layering the rafters (and purlin?) with OSB and drywall would be ok? In my head I imagined building each inside out module as a whole unit then installing it in place, much like this drawing (plasterboard omitted for clarity). Small gaps between the module and rafters for tolerance and lighting wires as I have LED lights on small rails that are an ideal fit directly below the rafters. I imagine both approaches would work but I reckon I'd find it easier to build the modules on my workbench than at height.

Cheers,
Jennifer

#490

I've checked the space with the camera, and to the extent I can see it looks consistent with the plans. I'll remove more drywall, fingers crossed.

Cheers!
Jennifer

#491

definitely build and mount if going moduler. and i think with enough units across the width, you'll have almost the same amount of air (albeit discontinous) but from a trapping perspective, we could consider slats to tune them to correspond to the modes.

#492

Thanks Glenn. I've been removing more ceiling drywall today, slowly and carefully with the aim of preserving decent joining points between the new and old layers. Looks like I'll be able to get a smooth continuation of the sloped ceiling into the modules at the front of the room. Nice. There's a bit of wood at the back slope that would prevent this, but I think it's just a noggin for the drywall, nothing structural. More will no doubt be revealed as I remove more drywall.

Slightly more concerning are two bits of thin (about 18mm) wood running across the top of the ceiling beams. These are not the purlins. The electric supply cable for the lights is tacked along one of them, so fingers crossed that's its sole purpose. It's certainly where the plans indicate electric cable routing. If so, perhaps an electrician can raise it higher and extend the cables to allow 300mm high modules. I'll have a better idea once I've removed more drywall.

#493

I've removed all of the ceiling drywall and much of the insulation above it, and the layout is much clearer. The purlin beams are marked orange on the house plans. They appear to be used where velux window sets are encapsulated between doubled or tripled rafters.

Here's one of the real ones, made from two 195x45mm beams joined together. It's huge. The other purlin beam is the same. These are load bearing and definitely should not be altered so I will make cutouts in the inside out modules to go around them.

Here's an overall view. The rafters are running from left to right in the photo; the two load bearing purlin beams from top to bottom of the photo. I am almost certain the older looking wood above the lights is not load bearing and has no structural function as it's thin (about 18mm), not on the plans, not particularly well attached, squint, and the middle plank ends in mid air. I suspect it was installed by the carpenters as either a temporary fixing or maybe even something to stand on while building the house, then just left in place after they'd finished. There were similar bits of wood in the eaves. So hopefully I'll be able to remove them and have 300mm high inside out modules up there. One of my neighbours built several houses based on the same plans in our street, I'll ask him what he thinks.

Another view.

There's some useful slack electric cable here leading to those lights. Hopefully enough to allow raising the cable 150mm to pass over the modules, otherwise it's time to call the electrician to have it extended. The cable is tacked onto one of those old planks, I'll make a similar attaching plank to raise it. There's a small diagonal beam coming down to the top of the rafter above the lights, also visible in the previous photo. It looks more important that the old wooden planks. I think I'll leave it in place and build round it!

#494

the older flat stuff are nailers for the lights so should be no issue to remove. not sure what the diagonal board is unless there is some room feature or a some stabilization function - so maybe leave it alone. the wiring might be easy enough to use the existing wire to snake some new wiring once the space is sealed up - i.e. run the new wiring on the surface of the interior drywall. i'd run lights off the wall switch and maybe add a switchable outlet up there as well for additional lighting options (e.g. videos etc).

#495

Thanks Glenn, much appreciated. My neighbour checked out the old wood today and said the same thing, and I removed most of it today. I like your plan to snake some new lighting wiring, the existing wiring is almost long enough to permit 300mm high modules, but not quite.

Cheers!
Jennifer

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