Restructuring Recording Room

[EachHit]

Hello,

I hope this thread is in the Right Spot cause it's more a thread looking for help on building the Stuff we need.

We wanted to optimize our Recording Room where we mostly record Drums and Vocals. So we had somebody measuring out the Room and do a Measurement Report. It was quite interesting to hear how the Low Bass frequencies sounded in different positions in the Room.
2 Drumsets are always in the Room cause it's also a Rehearsal Room.

The Report says that there is no need for "Special" Absorbers and Diffusers. Just some Broadband Absorbers and Bass Absorbers. We did some change as the Report suggested so we removed an old platform where the Drums were standing. Now we got a complete even floor. We also removed all previous selfbuild Stuff (for example Some Wood frames covered with Molton ans some filled with Rockwool).

For the Beginning I wanted to know how to build 2 Basstraps which should be in 2 Corners regarding to the Measurement Report.

Maybe someone can come up with Tips on how to professionally build these 2 Traps. For all our Absorbers we wanted to use a Product called Hannotect:
http://www.hanno.com/tl_files/pdf/techn ... Schaum.pdf

We know that there should be some of this stuff in the Bassabsorbers but there also should be some nonwoven Material with specific characteristics in it (e.g. flow resistance ~1.087 Pas/m²)

Maybe someone could help us on how to build the Traps. If needed I can take some real Photos and maybe post more specific dimensions of the Room.

Greetz

[Soundman2020]

I hope this thread is in the Right Spot cause it's more a thread looking for help on building the Stuff we need.

It's fine! No problem.

We wanted to optimize our Recording Room where we mostly record Drums and Vocals.

Drums and vocals are rather different instruments, and rather different acoustics! Drums usually prefer a more spacious, more live sounding rooms, while vocals normally need a drier, cosier, warmer sound. To do both in the same room is a bit if a challenge! I'd suggest that you give some thought to having variable acoustics in the room, so that you can change the sound as needed.

So we had somebody measuring out the Room and do a Measurement Report.

When you say "measure", do you mean they did an acoustic analysis of the room, using reference monitors and an acoustic measurement mic hooked up to a computer? If so, then please post the actual impulse response file here on the forum, so we can download it and analyze it properly. If they did the test using the REW software, then it would be even better if you could post the MDAT file.

It was quite interesting to hear how the Low Bass frequencies sounded in different positions in the Room.

If that's the case, and you have very noticeable differences in the low end, that implies that you have a modal response issue and possibly also SBIR / LBIR issues, so you are likely going to need some pretty serious bass trapping in there, as well as other treatment. Your plan does show two bass traps, but I suspect you will need more than that, and you'll also need it in different locations.

The Report says that there is no need for "Special" Absorbers and Diffusers. Just some Broadband Absorbers and Bass Absorbers.

That's good news, I guess, but personally I do consider bass traps to be "special" absorbers! But maybe that's just me...

On the other hand, your SketchUp model does, in fact, show a large number of very special diffusers, distributed around the walls. It shows a total of eight very large, tuned, Skyline diffusers around the walls. QRD based by the looks of the pattern, and from the dimensions of the wells it would seem that they are all tuned to the same mid-range band. What is the purpose of those? What frequency range are they tuned to? Also, there's a pretty large issue with those diffusers being so close to the location of the vocal artist: Tuned diffusers should never be close to mics, ears or instruments if you want an accurate recording, where "close" means within at least 3 full wavelengths of the lowest cut-off frequency of the diffuser, or ten feet (3m) minimum, regardless of frequency. The reason is due to the "lobing" artifacts that are created by all such diffusers in both the frequency domain and the time (phase) domain. It's not a good idea to have a mic set up at a location where the frequency response is distorted, neither is it good to have a moving sound source in such a spatial relationship with a diffuser and mic (singing and VO both imply "moving sound source"). I would suggest moving or eliminating those special diffusers, at the very least in the area close to where the vocals will be recorded.

You also seem to have a full height (floor to ceiling) slot wall directly behind the drums, and that is also a very specialized device, which is part absorber, part diffuser, part reflector, and is also tuned. Very hard to design and tune one of those for specific frequencies. A bit easier to do so for a range of frequencies (broad-band mid-range tuned absorber, high frequency reflector, with little effect on low frequencies, for example). But once again, having a large flat slot wall directly behind the drums doesn't seem like such a good idea. If you look at photos of professional drum booth setups, you don't see that sort of arrangement very often.

the Report suggested so we removed an old platform where the Drums were standing.

Excellent idea! That was likely not helping at all, and was probably even causing acoustic problems in the room. Smart move.

For the Beginning I wanted to know how to build 2 Basstraps which should be in 2 Corners regarding to the Measurement Report. Maybe someone can come up with Tips on how to professionally build these 2 Traps.

Looking at the SkecthUp model, it seems that you are trying to build something called "Superchunk" bass traps, which are very, very good, and also very easy to build.

For all our Absorbers we wanted to use a Product called Hannotect:

IS there a reason why you wanted to use that for everything? It looks like it should work fine for mid- and high frequency absorbers, but it does not seem to be very good in the low end at all. I would not use that for bass trapping. The manufacturer's data sheet shows that it doesn't have much absorption at all below about 200 Hz, even in the very thickest version. Here's the data sheet for the material that we recommend for Superchunk bass traps, which is Owens Corning OC-703:

703-specs.jpg

As you can see, even at 125 Hz the coefficient of absorption for that stuff is still 0.84, whereas for the stuff you want to use, it is only about 0.2. That's a huge difference. In both cases we are talking about materials that is 100mm thick (4 inches). I would really suggest that you should re-consider your preference for that melamine foam product, and instead see if you can find OC-703 in Germany. If not, then there are other similar products that would work very well. But I would not use that Hanno-tect stuff for bass traps.

We know that there should be some of this stuff in the Bassabsorbers but there also should be some nonwoven Material with specific characteristics in it

Why do you want to do that? What is the acoustic reasoning behind that? There is very little advantage to layering material in a superchunk bass trap: The principle of operation is very simple: Thick, deep porous absorption with good low frequency coefficients. Yes, there is a slight advantage to layering porous absorption with different properties, as you do get a boost at the interface between them, but the effect isn't usually worth the effort.

with specific characteristics in it (e.g. flow resistance ~1.087 Pas/m

Why do you want that specific GFR number? And why so low? The GFR is usually much higher for materials with good bass-trapping characterstics, usually around 10000 to 20000. Here's a graph of the absorption you would get from 100mm thickness of that material:

Generic-porous-absorber-1kRayls.jpg

And here is what you would get for the same thickness of a more typical material, at 15000 Rayls:

Generic-porous-absorber-15kRayls.jpg

As you can see, the type you are looking for has practically no uses at all in low or mid frequency applications. it is only useful above about 2 kHz, in the highs.

Maybe someone could help us on how to build the Traps. If needed I can take some real Photos and maybe post more specific dimensions of the Room.

Superchunks are easy to build: Just cut up full panels of your insulation material into right-angle triangles that measure about 90cm along the two adjacent sides, and stack up those triangles from floor to ceiling. Then build a light-weight wood frame around it, and cover that with some type of breathable fabric. In your case, since you do want to keep the room live enough for drums, I would suggest also putting plastic across the frame, to reflect some of the high frequencies back into the room, allowing only the mids and lows to get through to the absorption.


Here's a thread that shows you the normal way of building Superchunks:


http://www.johnlsayers.com/phpBB2/viewt ... f=3&t=7278

And here's some information on the type of results you can expect:

http://forum.studiotips.com/viewtopic.php?t=536


To be honest, it looks like there are several ways the acoustics of that room could be improved, in order to permit recording both drums and vocals (obviously not at the same time!), and I'm not at all convinced that the treatment plan shown currently is going to do what you want.


- Stuart -

[EachHit]

Thanks Stuart for the Detailed answer,

in the Sketch is some stuff missing. I only posted the one with what we wanted to start. There's a complete Acoustic Curtain all around the Room for infleuncing the Acoustics as needed. The Trap right behind the Drumkit was specifically built and calculated from my cousins former Soundguy. And it seems to do something good to the Room regarding to the Measurmentguy.

I don't really know how the Basstrap should look like. I only have a list of Parts which should be used. But I don't know exactly how it was meant to be built. The Measurment Guy didn't want to give us any drawing unless we order some of his built Absorbers which we intended to build ourselves cause we are on a Budget.
I think the Broadband Absorbers go down to 80 Hz but of course the factor is smaller than One.

The Broadband Absorbers will have a Depth of 150mm cause there are 3 Pieces of the Hannotect stacked on each other I think.

And there should also be a second Drumkit (mine) permanently in the Room on the Right Side facing to the Drums on the left side.

Maybe it is best when I do some Photos when I cleaned up the room cause I need to prepare it for some painting.

BTW: I just had a quick look at the Thread about the Bass Traps. My Cousins old Soundguy builded two of them on Rolls and it seems that they are build exactly like that. Some walls had also a Frame filled with Rockwool. Yeah it is really best when I provide some Photos later on I guess. As a German it is hard to explain something technical in English.

Heavy Greetz