Garage Studio Build - Checking my plans are sensible

[RKML]

Ummm... Are you SURE you are doing your reflections correctly??? It doesn't look like it from those diagrams!

Key point: "Angle of reflection = angle of incidence", using the SURFACE NORMAL as the reference axis. Are you SURE you are creating your surface normals correctly? And that you are reflecting in the correct plane, around that surface normal?

- Stuart -

Wow. WOW!!!!

If anyone ever needed a demonstration on the effects of baby-induced sleep-deprivation on an otherwise vaguely competent brain - well there it is.

Of course you're right, and as soon as I read your post I could see I've been doing the angles backwards. I done some weird calculation - measuring them from the vertical, not from the angle of the plywood panel or something like that

Are new parents allowed to fly planes? They shouldn't be.

I'm off to have a strong coffee and a word with myself.
Back to the drawing board.

(At least I've managed to answer my own question from 8 posts ago:)

I've got to be getting something wrong here

YUP!

[Soundman2020]

If anyone ever needed a demonstration on the effects of baby-induced sleep-deprivation on an otherwise vaguely competent brain - well there it is.

Oh yeah! That'll do it for sure!

Are new parents allowed to fly planes? They shouldn't be.

Even worse than that, new parents are actually allowed to take care of small children! Imagine that...

Back to the drawing board.

I think you'll find that your angles will be rather lower than what you had so far.... It's a pity I didn't see that before... I guess I hadn't looked closely enough, or maybe it was just the view point in SketchUp... Dunno... I can't blame it babies, though!

- Stuart -

[RKML]

Erm, lets forget my last couple of posts ever happened....... and we'll try this instead!

Angles of sound illustrated are every 10˚, from 10˚ off vertical to 50˚ off vertical.

The two plywood panels are at 30˚ for the front one, and 15˚ for the rear one.
I think this diagram makes a little more sense....

Re-Test double cloud idea 7.jpg

The only angle that's bugging me a little is the 40˚ one. It's firing into the floor at the back of the room, instead of the rear wall treatment. I could maybe tweak the rear panel and extend it back a little further to catch everything up to 40˚ or so.

If the concept and principle here is right though, I'm confident I could build this one at least!

[RKML]

I’ve managed to find some hefty eye plates to hang my cloud from, and matching chain.
All the fixings are rated for 80kg, and there’ll be 4 on each cloud, so I’m happy that it’s not going to come down on my head.
I’ll use 21mm plywood.

Unfortunately there seems to be a Rockwool shortage in the UK at the moment, and I’ve just run out. Apparently the factory have had a production problem and everyone is out of stock. It’s delayed me a bit but I’ve found a builders merchant in North London that has some so I’ll go and get it on Monday.

If Stu or Greg get a chance to have a look at my panels and see if my new design makes a bit more sense that would be really appreciated. I’m going to try to hang the plywood on Tuesday.

Onwards...

[Gregwor]

Looks awesome to me!

Greg

[RKML]

After an unexpected week's break, the studio treatment work should be continuing this week, first priority being the cloud.

Stuart, if you have any comments on my final 2-part cloud design above I'd love to hear them. All seems to be functional from what I can tell.....!

After that, and with the cloud and front-wall-top-corner-superchunk in place, I'll do an update to show the room in its entirety, and REW tests for both cloud and superchunk.

Based on the results of that I'll start trying to put some decay back with some plastic covering and possibly wooden slats if the tests show they're needed.
All input welcome!

Cheers,

Owen

[RKML]

Large update post coming up after this one.

In the meantime though, I am confused:

In order to check if my major 99hz null was a floor based reflection, I did a test with a whole bag's worth of RW45 on the floor between mic and speaker (so a slab 600mm x 1200mm and 400 mm thick).
Then a re-test without.

RW45 on Floor Refection Point:

RW45 on Floor.jpg

Bare Floor

Bare Floor.jpg

It seems like the null got worse with the rock wool on the floor? I don't understand how.
But certainly I'm guessing that means the null problem is not floor-reflection.
I'm getting a bit glum about the possibilities of me getting rid of that null now. Nothing I've done seems to have touched it.

Anyway, I've got my cloud up now, so final REW tests to come in MDAT format.
My next step is to put the plastic sheeting in place, and I'm researching how much / where to put it.

Cheers,

Owen

[Soundman2020]

I did a test with a whole bag's worth of RW45 on the floor between mic and speaker (so a slab 600mm x 1200mm and 400 mm thick).

OK, so take that same bunch of "stuff" and walk it around the room! Try it in many different locations, to see what changes. Put it on top of a chair or ladder, move that around, lean it against the side walls, high and low, put it on the floor BEHIND the mix position, put it up against the front wall, and the back wall... put it any place you can think of, and do a REW test at each location. And especially in one location that you won't like: on top of your desk...

It's almost certainly SBIR or another form of phase cancellation, so moving around a substantial chunk of absorption will have to have SOME effect on that, if you get it in the velocity peak associated with that null.


- Stuart -

[RKML]

And here is the final state of my studio with the following treatment in place

(All treatment with RW45 Rockwool)
Rear Wall: Covered to 30cm depth
Rear Wall / Ceiling Corner: Superchunk 30cm edges
Front Wall / Side Corners: Superchunks 60cm edges
Front Wall / Ceiling Corner: Superchunk 60cm edges
Side Wall First Reflection Points: 20cm thick panels
Front Wall Between Speakers: 10cm thick panel
Cloud 1: 36mm MDF, hanging at 15° Covered with 10cm RW45
Cloud 2: 36mm MDF, hanging at 30° Covered with 10cm RW45
(Both clouds ray-traced to send energy to rear wall)

Here are some Sketchup drawings for a visual idea.
I've made some of the panels transparent so you can see what's going on more clearly:

Studio copy.jpg

Complete Studio 2 copy.jpg

Complete Studio 3 copy.jpg

Complete Studio 4 copy.jpg

Here is the MDAT for the studio above, as shown in the diagrams.
https://www.dropbox.com/s/5nu9rvxqwhi3c ... .mdat?dl=0


Here's the full Waterfall for the studio: (1/48)

Full Waterfall All treatment in place.jpg

And here it is smoothed to 1/6

Full Waterfall Smooth All treatment in place.jpg

It's come a long way since I started. Thanks so much to Stu, and Greg for their help here, and to the board in general for the hundreds of previous posts that I've read trying to research this. It's been a lot of work and learning. This was an empty garage three months ago.
I'm onto my last challenges, I think.

99hz null
I feel like I've exhausted my knowledge here, and the biggest hurdle I'm still stuck with is the 99hz null.

Waterfall All treatment in place.jpg

Having apparently deduced that it's not floor-reflection, (see post above) I really don't know where to go with that. If it's rear wall, I've already maxed out the space with RW45 that I possibly can fill. Any ideas welcome.

Impulse

Impulse All Treatment In Place.jpg

This seems to be ok-ish, if I've understood Stuart's previous posts on this correctly.
I can see that I've got two very quick reflections creeping up to -15dbfs, at 1.05ms and 2ms. I'm guessing those are off my desk, as I've treated all the reflection points on the wall I think.
There were far more reflections above the -20dbfs mark in previous REW tests, and the side panels and cloud have seen those off.

Decay Times
My next job, before I cover all the rockwool with fabric, is to put some surfaces up to reflect some energy back into the room. I can hear audibly that it is a little dead in here when I listen to music.
Here's the RT60, zoomed in to 500ms. The blue (I think? - I'm colourblind) line is T30, the other one is T20.

RT60 All Treatment In Place.jpg

It's not going to win awards I think, but it's a lot better than it was previously.
So before I start covering stuff in plastic, where's my point of attack here? I'm wary of shooting for every little deviation in the graph and ending up with diminishing returns.
I seem to have a lot of messiness around 150 - 1000hz.
According to the equation that I've found in Stu's posts previously (F = 90 / m) I'm going to need plastic thicker than 6 mil to get anywhere close to this.

Three questions:
1) I'm guessing I'll need wood, not plastic to reflect back some 150-1000hz into the room. I guess the equation still remains the same? I've got some thin boarding I could use - I could weigh that and work out if it is going to reflect the right sort of frequencies.

2) Higher up this thread, Stu recommended around 180 - 200ms decay for my size room. I seem to be getting that, or thereabouts for everything over 1khz. Is it worth my getting some thin plastic drop cloth on the back wall and trying to get those high frequencies reflecting a bit more, or are they looking ok? Subjectively, the room sounds a little dead in the high end to my ears, but that may be because I'm used to less-treated rooms

3) If I put in wood panelling that works out according to F = 90 / m to reflect 500hz (for example) then does it also reflect all frequencies above that too? Like a high shelf on an EQ? Or would it reflect mainly 500hz, and some either side, like a bell curve EQ?


I think that's enough for this monster post for now. If I think of anything else that's scrambling my brain I'll post again.

Cheers!

Owen

[Soundman2020]

Not sure if you noticed, but I posted something just before you did...


- Stuart -

[RKML]

Not sure if you noticed, but I posted something just before you did...


- Stuart -

Cheers! I saw it after I posted my long post - and I've been on the case accordingly, hunting SBIR with my huge block of RW45.

So... I feel like I've got some data that means something... I just don't know what it means.
I tried the 40cm thick slab in various places, on the rear wall, on the floor behind my chair, etc.
Nothing had any effect on the null until I tried the one that you hinted at - on top of the desk.

This had some effect:

From Nothing On Desk:

Waterfall All treatment in place.jpg

To RW45 On Desk

RW45 On Desk.jpg

The null gets 4db less deep.

So I thought I'd take that to it's logical conclusion, and remove the desk completely. I just took it out of the room and put the iMac and interface on the floor.

Now the null is still there, but moves from 99hz to 111hz.

No Desk

No Desk.jpg

Now I'm confused. At first this suggested to me that the null was desk bounce, and now the desk is gone it's floor bounce.
But surely the extra distance to the reflection point (speaker-to-floor instead of speaker-to-desk) would mean that the SBIR frequency would get lower, not higher?
So what have I just found out? It seems backwards.

Then, because I could, I tried another measurement with no desk, and the big slab of RW45 on the floor where the reflection point would be.
And the null stays at 111hz, but gets much deeper - from -67db to -58db

RW45 On Floor - No Desk

RW45 On Floor No Desk.jpg

So now I'm totally baffled.

If you've got any answers Stuart, and also any thoughts on my three questions re. foils and decay-reflection in the long post above, I'm ready to learn!

Cheers,

Owen

[Soundman2020]

If you've got any answers Stuart,

Hmmmm... Hopefully the desk is still out? If so, put a tall ladder right where it was, and balance your insulation panel on top of that... might be ceiling bounce? If that makes no difference, keep trying other spots around where the desk was, at different heights and angles. See where you can get the largest effect.

Also, in your various MDAT files, take a look at the IR data to see if you can spot reflections that change position (timing) as you move the insulation panel around.

And it might seem counter-intuitive, but if you can easily take out one of your clouds, try doing that and see what changes... (If it's a big hassle, then probably not worth it)

...and also any thoughts on my three questions re. foils and decay-reflection in the long post above...

First things first! Deal with the big null. But basically, you have a lot of high-end roll-off on the frequency response, but it's not reflected in the time-domain response, so I'm wondering if that is speaker related, or signal-chain related.... Do you have any EQ applied anywhere? Maybe on the speakers themselves?

- Stuart

[Gregwor]

I had a big null that was introduced in the crossover in my sub. I used y cables to split the signal between the sub and the mid/highs which really helped bring up the null. Are you using a sub?

Greg

[RKML]

Ah cheers Greg, but no sub in this tiny room!

Can't find anything that would do a high end roll-off in the hardware. The interface has no EQ functionality at all, and the speakers (Neumann KH120) do have an 'Acoustcial Controls' EQ section on the rear panel, but the switches are all set to 0.
I did notice that the high end roll-off seems to be gone on the REW tests which I did with no desk in the room.
I'll fire up REW and take a snapshot and post it up here, when I get back in the studio.
Could interference from the desk be causing a high end roll-off?

SBIR hunting will re-commence when I get a few hours in the studio later.

[Soundman2020]

Are those graphs from just ONE speaker, or from both at once? This is why you need to do three tests each time: one with just L, one with just R and one with both LR. The LR test will tell you all about the low end of the spectrum, but you cannot judge the high end from that, since even minor variations in mic placement can create huge interference that trashes the high end graphs. So you need the individual L and R data for the high end.... but that's doesn't tell you much about how the speakers are working together in the low end! So you need all three tests...

I'm guessing that we are looking at "LR" tests in the above?


- Stuart -