John Sayers' Recording Studio Design Forum

OK, i sketched up a summary of the suggestions

I will try to get wool as similar as possible to OC 703 and 701 (but to stay simple i just used this OC types as reference).

While i readed different threads suggesting less dense wool for thicker traps, what do you think i should use for the 40cm to20cm ceiling and 30cm front site?

Behind the rear wall I will build hangers with 703 like wool. That would be more afford but i think it is worth adding some mass there

One other question came up while i was sketching up: If i angle the slot walls from 20cm to 10cm (that i can put more rockwool behind), do i receive better broadband absorption in the midrange doing this?

http://www.file-upload.net/download-3877198/upstairs-mixing1-3.skp.html

all the best
Aaron

If you are going to do a 1m deep bass trap behind your couch, I'd do that with hangers. That deep might be overkill, but certainly won't do any harm!

Yes, an angled slot wall will give you broad-band treatment. You probably don't need to tune specific frequencies in your case: just go with John's "generic" dimensions, and that will probably work fine.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart,
thank you very much for all your help!
*Updated the mineralwool table on the first site to get an overview on the different specs and I also talked to Rockwool for asking about acoustical infos for Termarock50 and Sonorock but without luck...

I was willing to order SSP1 but found this thread AVare and Ethan say any glasswool with the same weight and density like 703 does the same. Now i feel irritated if i should better order Termarock 50 cause it´s weight and density is the same as 703. The price/material 6,80EUR/m for Termarock 50 is way better too. What do you think?

Here is the link:
http://www.johnlsayers.com/phpBB2/viewtopic.php?t=9677

best regards
Aaron

Yup. Andre and Ethan are correct. In fact, it isn't even really the density that matters: The key point is the gas flow resistivity: how much the insulation resists air moving through it. That is different for different products, which is why you need more dense mineral wool or less dense fiberglass to get the same effect: You only get optimum gas flow resistivity with mineral wool that is about 30% more dense than fiberglass. But it really doesn't matter all that much, as long as you are in the general correct range, and are using the right type of insulation, it will work fine. You only need to be very picky about exact densities if you are trying to optimize something for a specific purpose. As long as you don't go overboard in the wrong direction (like getting 100 kg/m3, or 10kg/m3) then it will most likely be fine, so go with whatever is cheaper, and is within the density range for that type of material. As Andre said: sometimes it even makes sense to get thicker, lower density cheaper stuff!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

i´m just building the left slot wall at moment. looks cool so far. Thank you for the great advice, Stuart! I will upload some pics next time . The wall will be 7cm to 30cm deep. I have few questions that came up while building:

I ordered black "cotton nettle (fire resistant)" fabric for the slot walls and if i breaths trough it there is a medium resistance It looks very dense too.
Can i use it for the slot wall or should i search for fabric that is very pervious to air? Maybe grey garden fleece is better?

Another question; can i use 1,8cm thick mdf panels for the slot wall instead of 2cm? The reason is 2cm from Johns layout is hard to find here.

I searched the whole forum for insulation advice in slot walls. John skizzed polyester insulation in his layout and polyester insulation is almost very light an airy. I guess i should search for polyester wool or can i use really light rockwool? The meanings are here very different and confusing. Some say to use a dense 1"-2" mineralwool sheet and fill the rest with light mineralwool but i could not find people discussing about polyester or very light material for their slot walls...

Aaron

Sounds like it might not be the best stuff. I'd go with something more breathable than that. The slug of air trapped between the slats moves in and out, so any resistance it encounters going in will tend to dampen the resonance and spread the Q broader.

You can use 1.8 cm, yes, but the you should really re-calculate all of the other dimensions to compensate, since you'd be re-tuning all the slots to different frequencies. Depending on your room and the other parameters of the slot wall, that might be, or might not be, a big deal.

In reality, it isn't actually the density that matters, but rather the gas flow resistivity. There is an rough correlation between density and gas flow resistivity for each type, but the types themsleves are different. That's why you see different density recommendations for mineral wool and fiberglass. You can use either, but if you use fiberglass then it needs to be around 30 kg/m3, while mineral wool needs to be around 50 mg/m3. I'm not sure what the density should be for polyester: you'd have to find out what the gas flow resistivity is for the stuff you can get where you are, and see if it will work. Or just use ordinary mineral wool of around 50 kg/m3.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

i just searched and found your math form:

f = 2160 x sqrt ( r / (( d x C x D ) * ( r + w )))

Where:
f = resonant frequency (Hz)
r = slot width
w = slat width
d = slat thickness
C = mouth correction factor (1.2, normally)
D = depth of the cavity.

But if i calculate with sqrt (square metres?): 3,47²
Slat width: 10 cm
Slot: 2,5 cm
Slat thickness: 1,8 cm
deph of the cavity: 30cm

I get a frequency of 6,666...HZ
is it correct? If so i need make the angle smaller or the slat and slot size...


[/quote]
Thats good, i will use sonorock then.


You sayed some posts ago it might be good to put absorbtion to the first reflection point head over the monitor on the ceiling. I removed the wood panels today and figured out there is 6cm more space behind. Should i put 20cm rockwool on the ceiling over the monitor place angled to >40cm to the rear wall or should i better flip the angle that i have 40cm rockwool over the monitor and angle it to the rear wall to 20cm (screeshots added below)?

Tomorrow i will measure again to find out if the frequency range has changed with the deconstruction and new wall of the room and

Thank you very much

Aaron

That's because that equation is for IMPERIAL measurements, not metric. Convert all those to imperial, and you should get the right answer. Somewhere I have the equation for metric, but I can't locate it right now...

I can't figure out those two images, so I'm not really sure what you are saying. But the cloud should be angled lower at the front (over the speakers) and higher further back (over the chair).

Also, you don't need rockwool that thick. 10cm or 15cm is plenty for a cloud.

The easiest way to do this is to build a frame, put the wool in it, wrap it with cloth, then hang the frame from the ceiling, angled slightly.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Tank you so much! This will help me a lot building the ceiling over the sitting position today. I temporary put rockwool in bags to the sites and front and since the left wall is finished the 60hz to 80hz problem is much more better or completely cured. Looking forward to do some tests today to see what happened exactly.
thank you
Aaron

what happened so far:
- removed the wood-slats of the ceiling over the sitting position, the left angled wall and the rear-wall.
- built-on left wall to get a symmetric room (2cm thick drywall)
- temporary placed 20cm thick rockwool in two bags on the new left wall and three bags on the front wall.

Here are the current measurements of the left / right speakers.
I ordered termarock 50 (50kg / 16kPa) for the 10cm to 15cm ceiling over the sitting position (thicker side to the front as you wrote).

Next step i will remove the wood-slats of the right wall and put two rockwool bags there (like i did with the left wall), finishing the ceiling over the sitting position with termarock 50 as soon it does arrive and measuring again. Hope to get the left signal as good as the right one. I used thick HDPP bags for the rockwool. the highs look nice but i still have phase issues around 1000hz. 280-300hz still does not look good too (hopefully the slot wall will do it)... should i tune the slot wall to a broadband frequency around 100-300hz? What do you think? i will try to do the calculations then again .

Aaron

here some pics.
Happy Xmas

Short question for the ceiling over the monitor and window section cause I started to build up the frame... is it good to angle the ceiling absorber from 44cm to 20cm as shown on the sketchup pic below?
I would put in lighter rockwool there "Sonorock 6kPa". I hope to cure the still existing 1000hz reflection problem but also the deeper midrange (300-500hz) by the material thickness of 20-30cm in the first reflection part and 44cm max over the window. Or is it not a good idea making it so thick in considering of the new measuries two posts above?

Best regards
Aaron

Angling would be fine! That would help to give a bit better broadband coverage. How thick are you planning to make it? It doesn't need to be 20 cm thick on one end and 44cm thick on the other: You could, for example, make a panel 15 cm thick and just angle the entire panel, leaving a small air gap at one end and a large air gap at the other. That would be just as effective. Of course, if you really want to make it that thick, there's no reason not to! (Except cost... )


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart, i finished the ceiling construction after reading your post on 28. but i was not able to upload the pic with my ip*d . Thanks for answering.

today is a good day cause i could make some new tests and photos. I can tell about improvements happened to the sound.
What i did so far:
Finished the front 30cm superchunk wall under the window and beside the window there is added 10cm of 703 like wool, preparing the corners for the hangers (i will get wood fibre next week).
The ceiling absorber are finished too. There is a angled one head over the speakers 40cm to 20cm and like you recommended a angled one 15 to 10 cm head over the sitting position. It looks nice and enlarge the room anyhow The room sounds even much more better than before. The sound image is very nice now but i hope the slot walls will help getting the mid range in a better shape. There are reflections from the backwall and side walls that i think cause the canyons in the frequency range.

What do you think about the up-to-date measuring and the coming slot walls?
Should I angle it or better tune it to problematic midrange frequencies with 50-80% wool inside to make it broadband

Does it make sense putting something absorbent on the backwall and measure again to find out the exact frequencys that cause the backwall and both sidewalls?

regards
Aaron