Garden mix room near Nottingham, UK

#121

Day 148

Over the weekend I bought a piece of 18mm play and took it to my friend who has a much better table saw than I. This was for inner door v2, after the first attempt warped.

The revised design is to create a wooden frame 100mm wide to surround the 11.5mm glass that will be the bulk of the door. This wooden frame will be 3 layers thick of 18mm ply glued and screwed together so basically 54mm thick ply around the perimeter of the door. The plan is for the first and third outer layers will be the same size as each other, with the longer lengths the full height of the door. The middle layer will be less than 100mm wide to allow the glass to sit within the sandwich of wood. Fortuitously the 11.5mm thick glass plus two thicknesses of glazing tape will be about 18mm. The layers will be cut such that the outer layer long pieces overlap the middle layer width piece, if that makes sense! Sorry for the lack of diagram.

So after several measurements and a few calculations my friend and I cut the sheet of ply into strips and I brought them home.

Today i used a range of clamps also borrowed from my friend to hold the first and second layers in place, pva glued it all and screwed the two layers together.

First layer with corners clamped

Second layer glued and screwed, and all clamped

Tomorrow once this is dry I’ll test fit that the glass sits in the middle (middle layer was cut to allow 3mm around the glass for sealant) and then get the door trimmed to fit the frame and the hinges attached, before fitting the glass and sealing. The following day once sealant dry I’ll glue and screw on the third layer, completing the sandwich.

#122

This evening I used my circular saw to trim the door to fit the opening, ending up taking a little bit off each of the four sides. I made the cuts by cutting progressively deeper each time, which seems to stop the saw ripping the wood apart too much, with the saw running against a long piece of wood clamped to the door.

I then test fit the glass - thankfully it fit(!)

and then made a jig so that I could route out for the hinges. I’d bought three ball bearing hinges due to the weight of the glass etc.

The jig worked fairly well although I still needed to mess around a little on each hole afterwards. When I finally hung the door I discovered I’d cut the holes for the hinges a bit too deep, so the door won’t actually shut. I think I can fix this with some shims to pack the hinges away from the frame a little. Luckily I have some spare 1mm thick neoprene that was used for shimming the windows.

Finally, I took the door back on to the floor, stuck glazing tape to it and then my partner and I carefully dropped the glass into the door. We had to lift it back up to get it square which was a right pain due to the glazing tape, but hopefully we got away with it. I then silicon sealed the gaps between the glass and the wood, and left it to dry.

#123

That is outstanding work, Gareth. Well done!

#124

Ha ha thanks Starlight, but it really isn't outstanding given that the hinges are sunk too deep! And the quality of the plywood cutting was entirely due to my friend having a really good table saw and associated fences that cut a properly straight line.

I'm really hoping that I can shim the hinges out to work properly. I’ve ordered some shims for hinges from screwfix.

The best thing is, though, that once the door is hung and the stops are in place on the door frame, I can finally clear out the room and do my baseline test, and from there get on with installing the acoustic treatment and soffit walls!

This morning in a break between meetings I quickly glued and screwed the third outer layer to the door frame.

This meant it had dried enough by 5.30pm so that I could use the trimming bit on my router to trim this layer to fit the size of the rest of the door.

With a bit of brute force (it’s heavy!) and a bit of help from my partner I got it attached to the frame. Shimming needed but fingers crossed it’s in!

#125

Superb. I can't wait to see the results of your acoustic tests and how you go about treating the room. It would also be interesting to see how much isolation to the outside you get.

#126

Day 151

Today I managed to spend a couple of hours on the door. I fitted the shims I’d ordered to the hinges to stop the door bouncing/springing as it was being closed.

I replaced the piece of wood that was part of the door frame on the latch side of the door as it has warped and also needed to align better with the front of the door.

Most importantly I fitted the latch and handles, a jest for me from scratch. Went pretty well.

After that I started fitting the door stops to the frame, which are 20mm thick wood with sticky back foam on the edge to give a seal with the door. Did the bottom and one side today and will do the top and other side tomorrow.

My plans had been to add another layer to the door and another set of door stops and seals to that, almost bank vault style, but I think I’ll leave that for now and measure performance first, as the door is already making a difference to sound transmission.

#127

Day 152. BASELINE TEST!!

This morning I finished off the door frame and then took all the tools and offcuts of wood out the room. The seal on the door is great apart from in one corner, so I need to get some more rubbery stuff and put that on. I may in the future get a different kind of seal but for now this is good enough.

With the doors both shut and the air fan running the background noise in the room is around 27dB, which is pretty damn quiet. With the fan off it drops a couple of dB but I'm pleased enough with that. I uncovered my monitors and set some music playing, to see what the volume level was outside. The video attached below shows a 50dB reduction, although I probably have the wrong settings on the SPL meter. You can still hear the bass outside (with music playing at 100dB!) but it's pretty quiet. I will do a test one evening when the outside background noise is less.

I couldn't get video demonstrating the volume reduction to upload, so I dropped it on youtube: https://youtu.be/Eyx0NzJQXtY

Does anyone know what settings the SPL meter should be for this type of measurement? the same as for REW?

Then, after much faffing I set up REW and my borrowed measurement mic and completed the baseline tests. Initially they displayed such that the R monitor looked quieter than the L but now I've re-loaded REW they look OK. Very odd.

So there are some standout nulls and peaks which correlate well with what was predicted for the measurements (5.5m long, 3.25m wide, 2.25m tall). This is good news I think!

There is a phase difference between the two speaker's responses, which I'm guessing means they aren't perfectly symmetrical. Can anyone clarify if I'm right about that? I'll check positioning before committing to their position when I build the soffits, starting on Monday!

#128

50dBC reduction is good. Looking at your door edges I suspect the weakest link will be the closing mechanism and its ability to ensure the seal closes the doors airtight around all edges of each door. I can only see one seal; how many does each door have?

Edit: your post has grown while I was replying! SPL meter should be set to use dBC slow.

#129

Thanks Starlight
I’ll redo those sound level measurements as I think they were A weighted and fast.

There is just one seal and it’s definitely the weak link. I could hear the music essentially pouring out of the top left of the door, looking from the outside, where it’s clear that the seal isn’t touching. I’m going to try making this bit of the seal thicker before worrying about anything else for now. I want to get on with the inside of the room and can always come back to the door and it’s closure and seal.

Cheers
Gareth

#130

That video was well cool. The difference between indoors and out is incredible!

#131

Thanks Endorka! It was very loud in the room and not really audible outside. I do need to try it at night though, as we’ve got quite a lot of background noise round here during the day at the moment with various neighbours construction projects!

I’ll do another video ASAP

#132

Good stuff. Apologies if I am stating the obvious, but the measurement of background noise should also be done with C weighted / slow. There's a whole thing about profiling the background noise, the name of which escapes me at the moment. Background noise can be "rumbly" or "hissy". A weighted won't pick up the rumbly stuff.

#133

Looking good! Change the scale on your graphs ... those are kinda unusable (unnaturally flattering). You want something like 35 - 100db on the graph, and 1/48 or 1/24 smoothing for looking at problem areas. I know this is just initial tests, but if you keep things consistent now, it's much easier to see the progress in your treatment work.

#134

Thanks both

I’ll redo my sound reduction tests with the C weighting and slow settings, which is what I now have it set on following the REW setup.

Good point about the graphs, I’ll change the scale and smoothing and re-post.

On to soffit building this week...

#135

Day 158 - studio build fatigue (and possibly Covid lockdown boredom fatigue)

This week has been slow. I’ve managed maybe an hour a day around work and other commitments, even though Monday was a public bank holiday.

I have managed to make the hangers for under the left side soffit shelf and put some of the framing in for the shelf above the soffit front. I also filled the stud bays under the soffit shelf with Rockwool RWA45 and cable clipped power and xlr cables for the monitors to the framing.

I ended up with 9mm ply for the middle of my hangers as homasote and any equivalent are either not available in the UK or on crazy back order. 9mm ply has the same density as homasote so hopefully should work.

I went with 50mm of fluffy style insulation to line these, although it’s horrid to work with. It’s stuck on with spray glue and then screwed to the top with more of those plastic insulation holders as I used in the silencer.

I set these out at angles, so that the middle of them should correlate with a division of the room width. So as the room is 3.25m wide; half the room is 1.625m and I kept halving til I got to 20.25cm and used this as the spacing working backwards from the centre. In theory this should place them at a node or anti odd of a room mode.

That said, I probably cut the wood for the hanger a bit too big as they are slightly obstructed by the insulation I put between the studs on the walls. They do have a couple of centimetres of movement so I’m sure that’ll be plenty. I can’t imagine that the bass frequencies cause these to visibly swing!

Going to do a full day on it tomorrow in the hopes of getting these soffits done so that the next test can take place.

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