John Sayers' Recording Studio Design Forum Archive

I am almost done with the interior wall. Two layers of 1,5 cm acoustic heavy gypsum board, caulked airtight with mapegum. Now I have to apply gypsum over the screws and paint it. Meanwhile I observed, that it is a bass overload (some lower frequency F sharp during speaking rings heavily and bounces around. So I will have to build some bass traps in all 4 corners from floor to top.
Studying the various DIY designs I ran into a lot of contradictory info. Some says that one should use wool with alufoil, since it behaves as a membrane. I don't doubt that, but somehow I think that would be tuned on some potentially unknown frequency, which is bad for me. Other says, that one should use low density wool, which absorbs more bass. Owens corning is 40 kg/m3. Some designer talks about rockwool which should be 80-120 kg/m3. Below there is link explaining that rockwool is different fiber structure then OC 700, and needs to be more dense for the same bass absorption. We clearly have no Owens Corning or roxul here. We have Rockwool, Ursa, and Isover, but this latter in my experience sucks balls.
Help me out here:
1. density to be used?
2. fluffy or rigid? or to put some more rigid stuff in front and fill up the triangular space behind it with fluffy stuff?
3. paper/alufoil or not? [I guess not, but I am no expert here]

I have some leftovers of 18 kg/m3 Ursa terra wool. Would that work? Those guys are in my country the only ones who measured and published the results with an independent university lab. You have the curves in the attachment.

I also attach a link regarding wools and equivalents to the OC700 series, that I've found on gearslutz:
http://www.gearslutz.com/board/7421723-post126.html

Thank You again for all Your help.
Tibi

Meanwhile I observed, that it is a bass overload (some lower frequency F sharp during speaking rings heavily and bounces around. So I will have to build some bass traps in all 4 corners from floor to top.

Before you do anything with treatment, you should first do a test with the REW acoustic analysis software to see how the room is behaving empty, with nothing in it. Then based on that information you can decide how to treat it.

Studying the various DIY designs I ran into a lot of contradictory info. Some says that one should use wool with alufoil, since it behaves as a membrane. I don't doubt that, but somehow I think that would be tuned on some potentially unknown frequency, which is bad for me. Other says, that one should use low density wool, which absorbs more bass.

It isn't really contradictory information: Rather, it is information on building bass traps using different principles of acoustics. Membrane traps are one type of bass trap, and porous absorbers are another type. Resonant traps are yet another option, and so are low frequency diffusers. All of them work, and each type has it's uses and its place. So you need to decide which type of treatment you need (based on the REW analysis), and where to put it (also based on the REW analysis), then decide how to build each one, and what materials to use.

Owens corning is 40 kg/m3. Some designer talks about rockwool which should be 80-120 kg/m3.

Owens Corning is a company that makes many different types of insulation, and only a few of them have a density of 40 kg/m3. Rockwool is also a brand name, and they too make many different types of insulation. Maybe you are confusing the brand names with the types of insulation? For bass traps based on porous absorption, if you use mineral wool products then you should look for a density of around 50 kg/m3, or maybe a bit less. Using something as dense as 120 kg/m3 would be too high for good bass trapping. If you use fiberglass insulation, then you should be looking for a density of around 30 kg/m3 or a bit less.

there is link explaining that rockwool is different fiber structure then OC 700, and needs to be more dense for the same bass absorption.

Correct. Rockwool is mineral wool, and the OC-700 product line (which includes OC-703) is fiberglass. Two different materials.

We have Rockwool, Ursa, and Isover, ... 1. density to be used?

As above: if you are using mineral wool insulation, then around 50 kg/m3, or if you are using fiberglass, around 30 kg/m3.

2. fluffy or rigid?

Not rigid, but semi-rigid is good. Rigid is normally too dense, but semi-rigid is good. It is better than fluffy for the actual building, since it is easier to to work with. But both fluffy and semi-rigid are good.

r to put some more rigid stuff in front and fill up the triangular space behind it with fluffy stuff?

That is also possible. No problem.

3. paper/alufoil or not? [I guess not, but I am no expert here]

You can do that if you want, and some tests have shown that it might have a benefit, but there's not a lot of real research on it so it's probably not worth doing until there is more information on it. Just go with ordinary unfaced insulation.

I have some leftovers of 18 kg/m3 Ursa terra wool. Would that work? the only ones who measured and published the results with an independent university lab. You have the curves in the attachment.

The data shown there is actually not what is needed. That shows the isolation values of a wall system, and seems to be something to do with calculating STC values. What we actually need is information on the coefficients of absorption at several frequencies. Maybe you can call the manufacturer and ask for that? However, at a density of 18 kg/m3 it might be a bit too light for good bass absorption.

- Stuart -

Thank You again for the prompt answer. Meanwhile I am at the "painting the wall" stage. I tried to measure with REW, but I had problems setting up the mic. It does not see my dynamic mics, except for the laptops's mic. Also I have a weird calibration curve of the soundcard, with +10Db extra in the bass domain, so presumably I cannot use the soundcard. I will try to set up via USB through my Tascam mixer. Also I have no measuring mic, but buying one seems to be too expensive. [for something that one uses a few times and then will stay catching dust; also a EMC8000 as other B products probably sucks balls and creates noise]. So I will try to set up my big condenser RODE 2A on omni. As You've said, I tried to measure with the mic and the speaker at the longest two points in the room. I let You know how that goes.
It is hard to calm me down, now that I am about to finish the actuals construction and can start setting up the stuff. I actually have to stop each time when "well, this would be probably OK even like this" kind of thoughts arise in my stupid head. So far I walked every time the "extra mile" and I am confident that e.g. I caulked the crap out of the walls, each layer, both walls, in a manner, that one could use my studio reversed as a boat.
I have to pour some mm concrete on the floor after I will finish the wall painting, and after that the power installation will follow. I will use separate circuits for lights [no fluorescent or other reactive stuff, only wolfram], vents, heating [IR panels], and all four groups of 220V outlets. Also, I think in addition to star grounding [ I have a 35m long wide metalic dedicated ground under the concrete of the studio, and it measures 1,6 ohms, which is better than most hospitals], I will use star wiring for both phase and nulls separately in all outlets, and so I can actually disconnect all power from the subpanel which not is use. Some extra wires, but I think this is good investment in silence. Null and ground are connected in the main panel. Instead of buying some "power conditioners" which seem to be at least in my opinion some expensive power strips, I will use simple varistor equipped power strips.
I am reading about speaker positioning. The nicest one seems to be the Cardas style which would fit to my room, since I am almost [unintentionally] as his golden trapagon sized room. I will probably will need some help on this one. I will try to draw a sketchup to show how I am intending to do, and I will ask You to have a brief look at it. Basically I will use stereo+1 sub, in a LEDE style room, which is not intended to be a mixing room. It is a [future] rehearsal room and audition room, and occasional recording room, with some mobile absorption panels, which occasionally will serve as "voice booth" in some corner with existent absorbers on the wall, otherwise will stay in the front of the windows. The mixes I will do in monitor head sets, and check them out in various players [car, kitchen, bedroom ] Well, this is a bit ahead, but is probably better to think ahead, than have to demolish stuff. I have to finish to read other 3 books on acoustics, to be a little wiser, but so far I understood the following:
1. Bass traps in corners are compulsory, and are never good nor big enough.
2. Diffusers are also ad libitum on the ceiling, which helps a lot, preferably above the listening position, the rear wall and also combined with absorption on the first reflection area.
3. Under 15% of surface treatment is probably not enough to be noticed. It is not clear, which surface though. The whole surface floor included?
4. Too much absorption sucks, and it is a risk of overdoing bass traps which not only absorb bass but absorbs also high and mid, and absorb even better than bass, so one risks to accentuate the bass issue. I've ordered some Rockwool of 50 kg/m3. for the corner bass traps. Behind those I will put some fluffy triangles. [all this is only in calculus so far. If I will not need them, or You will advise me against it, I won't use them].

How about these stuff: I plan to order 2-3 m2 just for ornamental use, the rest I will build myself:

http://www.thomann.de/ro/the_takustik_p ... er_set.htm
http://www.thomann.de/ro/eq_acoustics_c ... s_blue.htm
http://www.thomann.de/ro/the_takustik_w ... 8erset.htm (on the ceiling maybe?)
OK. I will get back to You with details, I will kindly ask You to tell me if something is seriously wrong in my ideation so far.
Thank You,
Tibi
So, here are the measurements. I have serious doubts that these are ok. I've used the USB input of a Tascam M164 UF mixer with a Node 2A condenser mic, and a tbone instrument mic - and the laptop's card output linked to an amp and 1 Magnat speaker (20-30000 Hz) in the two opposite corners of the room, exactly as You've told me to. A lot a feedback happened, and I doubt I have a 30 db difference between the bass and midrange, because I cannot hear it. And my ears are perfectly calibrated . That bass range F sharp I was hearing is gone together with the flutter echo now that I have installed the corner traps. (90 cm wide rockwool airrock ND in the short [front] wall, floor to ceiling - and 70 cm wide on the rear wall). I did not remeasured, but I can if You think I should. Anyway, my feel is, that I need very small amount of extra absorption [if any], because the room sounds already well, no bad reverb, and music sounds defined. Of course I have to figure out where to put exactly the speakers etc. [and Cardas or other calculators does not work at all - I think the only good stuff he's right about are the bookshelves]. In fact all this fuss about excluding your room out of the music is rather utterly overstated. I will do it exactly as I did in all my previous rooms, where I moved my speakers until I was satisfied with the sound, and sometimes in "theoretically impossible positions" like "quadro" with 4 speakers freestanding in 3 corners (1-2-1) and one wall covered with 2 mm cork in a room of 4x5x3,5m, or stereo in a similar room with the speakers placed in a mid area of two different walls [as N and W], and no treatment. It is true, full of book and other shelves and furniture. So my feel is that diffusion is way more useful than absorption [at least for my ears], and I already feel that it is enough absorption with 9% of the surface covered [by the basstraps - which absorb way more midrange and high than bass anyway]. I may cover part of the traps with thin cellophane as I've read somewhere - and LISTEN - because the conclusion of all this reading and calculus or softwares [4 years of study] is, that without experiments one just cannot simply trust any info - in the context of his/her particular room. I will add some photos later.

Also I have no measuring mic, but buying one seems to be too expensive. [for something that one uses a few times and then will stay catching dust; also a EMC8000 as other B products probably sucks balls and creates noise

They cost less than a hundred bucks, if you shop around carefully, or maybe a bit more, and they make great ambient mikes for use in your studio after it is built, as well as for other purposes. You'll use it way more than "just a few times" during the studio build and tuning. The ECM8000 isn't too bad, actually. I have one, and also a PreSonus, which is a bit more expensive. They perform about the same.

I am reading about speaker positioning. The nicest one seems to be the Cardas style

Careful with that... take a look around, and see how many pro studios actually use that, or anything even remotely similar.... There's a reason for that... ! Perhaps it might be related to the listening position usually ending up at the exact center of the room, which is the worst possible location for modal issues... You might also want to google "what is a trapagon" to find out that the "geometric shape" that he recommends for rooms, does not actually exist... the only references to this "trapagon" shape, are on his own web site, or other places that talk about it, but nobody can seem to find the math to figure it out, or back it up...

his golden trapagon sized room. I will probably will need some help on this one.

The best help I can give you there is to forget all about mythical magical shapes that don't actually exist, and rather use one of the known good ratios, which are fully understood mathematically, have been fully tested in numerous real-world builds, ad absolutely do work. Just make sure that your room ratio is within the Bolt area, and close to one of Sepmeyer's or Louden's ratios. Also make sure that your speakers are NOT set up so that your head is in the geometric center of the room, since that is the exact point where ALL modal peaks are at their maximum, and all modal nulls are at their minimum. There is no worse location in a room, except for the tricorners.

in a LEDE style room,

LEDE is a very old studio design concept from the 70's, that has long since been abandoned by serious studio designers, in favor of extensions such as RFZ, CID, and NER. LEDE proved to be very uncomfortable to work in for long periods, since it is not a naturally occurring situation. Our brains are not used to it, and don't like it much. RFZ is a much better design concept: retains the good points of LEDE while fixing the bad points, and generally being much more pleasant and more accurate to work in.

is not intended to be a mixing room. It is a [future] rehearsal room and audition room, and occasional recording room,

Then why are you worried about ratios, speaker placement, and room design concepts? If it is basically a live room, then none of that is important at all! That stuff only applies to control rooms.

The mixes I will do in monitor head sets,

Then why are you looking at speaker placement? If you wont be mixing on speakers, then why bother?

1. Bass traps in corners are compulsory, and are never good nor big enough.

In general, yes.

2. Diffusers are also ad libitum on the ceiling, which helps a lot, preferably above the listening position, the rear wall and also combined with absorption on the first reflection area.

If the room is large enough, then yes. But yours probably isn't. Your ears need to be at least 10 feet away from any numeric-based diffuser, and even further if it is tuned low: at least three full wavelengths of the note one octave below the low cutoff frequency of the diffuser. Any closer than that, and you'll be in the zone of lobing artifacts. The lobing occurs in frequency, direction, phase and intensity for at least those distances. Diffusers should only be used in rooms that are big enough for that.

3. Under 15% of surface treatment is probably not enough to be noticed.

It is not possible to specify the percentage of surface area that a room needs, since rooms come in different sizes: small rooms need a much larger percentage of their walls and ceiling covered with treatment, while large rooms need less. The only way to know for sure how much a room needs, is to calculate it it using Sabine's equations, or the more modern updated versions of those same equations. It is not uncommon to have more than 50% of the walls covered with some type of treatment, and some studios have close to 100% coverage: !5% is very low. What are the dimensions of your room? With that, I can calculate roughly what percentage you need. Is it still 11m x 10.5m by 7m, or did that change? If it is still that size, then it needs 2788 sabins of absorption to bring it within usable acoustics. That implies about 260 m2 of perfect absorption. The total surface area of your room is about 528 m2, so you need about 49% covrage. You can't cover the floor, obviously, so that leaves 413 m2 of wall plus ceiling area: You'll need to cover about 63% of that to get decent acoustics. 15% would basically do nothing at all useful.

4. Too much absorption sucks, and it is a risk of overdoing bass traps which not only absorb bass but absorbs also high and mid, and absorb even better than bass, so one risks to accentuate the bass issue.

Right: Dead rooms sound lousy, but you still cannot skimp on bass trapping. Rather, you install as much bass trapping as is needed, then you treat the front of the bass traps accordingly to keep the mids and highs in the room. The goal is flat decay times across the spectrum, such that no single octave varies vary much from its neighbors. Here's the graph for a control room that I've just finished tuning, that shows how it should be:
That shows the decay time in each octave band. As you can see, it is smooth across the board. And that room has huge amounts of bass trapping in it! There are vertical and horizontal superchunks, membrane traps, perf panel, slot walls, and the entire ceiling is about 3 feet deep in bass trapping, plus a large cloud hung below that. Yet as you can see the mids and highs are all still there. A well balanced room.

So, here are the measurements. I have serious doubts that these are ok.

It's impossible to say from just those graphs. I'd have to see the actual MDAT file, to analyze it fully. However, what can be seen from your room is that it has major, big, huge problems on the lows, between about 50 Hz and 200 Hz, which is very normal for a room that size. That can be fixed with bass traps. All your treatment has done so far is to kill the high-mids and highs. The problems in the lows are almost unaltered, with only small changes. Here is what that graphs should look like, for the range 15 Hz to 500 Hz.:
That shows smooth, clean, even bass response in the spectrogram, and here it is in the waterfall:
Compare your graphs to what it should be, and you'll see the major issues that need fixing in yours.

In fact all this fuss about excluding your room out of the music is rather utterly overstated.

I agree! A control room should be neutral, not dead. It should do nothing to the music, neither take anything away nor add anything to it. Live rooms, on the other hand, should have character, and should sound good.

So my feel is that diffusion is way more useful than absorption

Actually, the opposite is true. As I mentioned above, diffusion can only be used in rooms that are big enough. Your isn't. First comes enough absorption to control the low end, then comes enough reflection/diffusion to get the mids and highs back into the room again.

and I already feel that it is enough absorption with 9% of the surface covered

Not even close to enough. See above: to bring it within spec, that room needs about 49% of the total room area covered, or about 63% of the walls and ceiling.

[by the basstraps - which absorb way more midrange and high than bass anyway]

Then they aren't built right! They are too small, not deep enough, or made with the wrong materials, and there are not enough of them. If they are sucking out too much of the mids and highs, then they need to be partially covered with membranes of some type, where the thickness and coverage ratio can be calculated, based on the results seen in the REW data.

- Stuart -

Thank You again for Your answer.

Soundman2020 wrote:They cost less than a hundred bucks,

]

I've ordered a measurement mic today.

Soundman2020 wrote: forget all about mythical magical shapes

].

In fact in those positions sounds the worst. But all the other placement calculators are giving me close position to that one. At this point I will forget about calculators, and will experiment myself.

Soundman2020 wrote:Then why are you looking at speaker placement? If you wont be mixing on speakers, then why bother?

]

Because I have integral hearing as 20-31000 Hz proven by medical audiometry - which is more a course than a blessing, and it bothers me if one note sounds louder than the other. And that is why I am sure, that the measurement I've done is an artifact. There is no way that the bass domain sounds 30 db louder than the midrange, and I would not hear it. If I've got it right , every 3 db is roughly doubles the loudness as perception. There is no way, that 90 Hz is 10 times louder than 3000 as the graph shows. Well, I will remeasure once the measuring mic arrives.

Soundman2020 wrote:LEDE is a very old studio design concept from the 70's

Well it is not an exactly LEDE design. I just will have a more absorbtive part on one end and a more live one on the other end. I also plane to build some mobile traps of 8 cm thick foam, so I can use the absorptive side for a vocal space. Normally these will stay covering the window and symmetrically on the other side.

Soundman2020 wrote:f the room is large enough, then yes. But yours probably isn't. Your ears need to be at least 10 feet away from any numeric-based diffuser

I was thinking to install some diffusers on he ceiling like these
http://www.thomann.de/ro/the_takustik_w ... 8erset.htm
and use a large 4x2,8m book-shelve at the rear end of the room as a diffuser. I may arrange the books on it as I have seen some tips on this site. The listening position is at least 6 m from the real wall.

Soundman2020 wrote: What are the dimensions of your room? With that, I can calculate roughly what percentage you need

The measurements of the room are 3,9x9,9x9,1x5,7m with hight which is not constant, as You can see on the picture, basically there are no parallel surfaces in the room.
2.

Soundman2020 wrote:Then they aren't built right! They are too small, not deep enough, or made with the wrong
materials

[/quote][/quote]

I have super-chunks made of 50 kg/m3 rockwool, 90 cm wide and approx 60 deep on the front wall corners from ceiling to floor, and 60 cm wide 45 cm deep on the real walls. The bad reverb I had before is gone, and music sounds ok. I don't hear any bass overload, and nothing drives me to add bass, or do any correction on the eq. What I meant by "they absorb more mids and highs than bass" was according to the frequency absorption graphs, which invariably shows a greater n for the mid and high frequency than on bass. [e.g. 0.8 vs 0.2] In fact I was planning to put some celophane to cover part of them to increase mid/high reflection.
I know it is irrelevant because I did the measurement with the laptop's mic, but here are the measurement done after the basstraps [the ones in the previous message are with the empty room !!]

The measurements of the room are 3,9x9,9x9,1x5,7m with hight which is not constant,

OK, no problem. Taking the average width and length, it works out that you need 1021 sabins of absorption in that room. Discarding the floor, you have about 150 m2 of wall and ceiling space, so you'd need to cover about 63% of that with absorption to bring it within ITU / EBU specs. That's probably a bit too much for that room, in my opinion, so I'd start out with say 750 sabins to see how it goes, which works out to roughly 45% of the wall and ceiling area. But I would not cover it in large sections: Rather, I'd so the walls in a sort of "checkerboard" approach, to spread the absorption around evenly. I'd do it with panels of 4" 703 set in frames, so you can move them around the room easily and do some more tests.

In fact in those positions sounds the worst.

Yep! I've written about those voodoo "golden trapagon" thingies before on the forum, plus the Cardas recommendations for speaker placement, so I'm not surprised that they didn't work for you either! There's no acoustic testing behind any of his ideas: just ancient magical relationships from the depths of Greek mythology, apparently. But no reports of actual acoustical testing in reputable independent acoustic labs....

At this point I will forget about calculators, and will experiment myself.

Id suggest setting up your speakers against the short wall, with each one about 110cm from the side walls, the acoustic axis set at 120cm above the floor, angled in at about 25°, and with your head about 300cm from the front wall. That would be a good starting point for your adjustments.

And that is why I am sure, that the measurement I've done is an artifact. There is no way that the bass domain sounds 30 db louder than the midrange, and I would not hear it

The bass end MUST show louder on the graphs, in order to be perceived at the same level as the mids and highs. Human hearing is not linear: we do not hear all sounds at the same level: Google "fletcher-munson curve" to understand this.

Also, the human ear cannot interpret small changes in sound pressure level accurately. Most people can only just hear a change of 3 dB, and even seasoned engineers with well trained ears find it hard to discern a change of 1 dB.

If I've got it right , every 3 db is roughly doubles the loudness as perception.

No, you have it wrong: 3 dB is twice the sound POWER, yes, but not twice the perceived intensity. A sound needs to increase by about 10 dB for most people to judge that it is twice as loud, or decrease by 10 dB so that most people say it is half as loud. Once, again, human perception of sound is not linear.

There is no way, that 90 Hz is 10 times louder than 3000 as the graph shows.

I can't see that on the graphs at all, since you are showing then at entirely the wrong scale, both in amplitude and in time, and also in frequency. If you upload the actual MDAT file some place where I can download it, then I'll take a close look and analyze it correctly. I'd also need to know exactly where in the room you had the speakers and the mic for that test.

I was thinking to install some diffusers on he ceiling like these

Those are ordinary QRD diffusers. "QRD" means "Quadratic Residue Diffuser", which is a fancy way of saying that the are based on mathematical sequences. Those have heavy lobing, since they seem to be based on a low-order prime: looks like it might be 11. So you would definitely need to be at least 10 feet (3m) away from those, to avoid the artifacts.

and use a large 4x2,8m book-shelve at the rear end of the room as a diffuser.

That's actually a myth. Yes, books in shelves do diffuse sound to a certain extent, but not enough or in the right way to be useful. Most books are similar in size, and not wide enough to cover a useful frequency range.

In fact I was planning to put some celophane to cover part of them to increase mid/high reflection.

Cellophane wont be thick enough. It will only affect the very, very high frequencies.

- Stuart -

Dear Stuart,

Soundman2020 wrote:Id suggest setting up your speakers against the short wall,

Distance from the wall? Close to the wall? In all room acoustic books I've read they advise to avoid placing the speakers close to the wall due to bass problems. I will obviously try it. In fact I have always have put them 20-50 cm from it and sounded good.
The measurement mic is on the way.

Soundman2020 wrote: low-order prime: looks like it might be 11. So you would definitely need to be at least 10 feet (3m) away from those, to avoid the artifacts.

I already have ordered them. I will have around 5,8 m2 of those. I can put them 3 m away from me on the ceiling close to the large end of the room, on the back wall - where I might have more than 5m away from me. Should I put them in checkerboardstyle and vertical/horizontal or 45 degree angled zig-zag?
Can I put a few of them on the front wall between the rockwool panels? [if my head will be 3m away as You've said?

Soundman2020 wrote:Cellophane wont be thick enough. It will only affect the very, very high frequencies.

So what can I use? Paper? nylon membrane? diffuser panel?

Soundman2020 wrote:If you upload the actual MDAT file some place where I can download it,

https://www.dropbox.com/s/1b76znkpmu2zm ... .mdat?dl=0

https://www.dropbox.com/s/fqwrtupc0qerk ... .mdat?dl=0

The first file was recorded without any treatment, with the mic as far as possible from the speaker [high corner vs. opposite low diagonal corner, ad You've instructed me to do] using a tbone guitar recording dynamic mic.
The second file is with the corner traps, but with the laptop's mic, between the speakers placed 2 m front the front wall, and about 1,3 from the side walls.

I know, that those are not comparable, and also that they are probably a waste of Your time, so considering all this, maybe it is a better idea to wait for the measurement mic, and do it as You will instruct me to place everything. But since You wanted me to upload, I did.

I have also some 4 m2 8 cm wide foam, to add to the absorption. I will cut them in smaller pieces e.g. 25 x 25 cm, to spread them around. But I will wait until You will answer - to the properly measured room mdat I hopefully can do soon. And now some photos.

Thank You, I really appreciate Your help.
Tibi

Dear Stuart,

Here are the measurements. I identified by ear 2 good spots, named position1 and position 2. I also did the middle of the room, as a reference, and the 38% ..since everybody seems to think that should be the one, and finally the back end also.

Here is the link.

https://www.dropbox.com/s/kmnj742nrvg4c ... .mdat?dl=0

Thank You in advance,
Tibi
PS. For the details, please see my previous post with photos. Since then, I added 2 more traps on the lateral wall, also have 2 mobile traps - one of them covering the window and the other symmetrically on the other wall, also 3 more clouds in the same line as the first one on the central line of the ceiling.

Position 1 and position 2 are not very good. The response is not smooth for both, there's a big hole in response at about 46 Hz for pos2, a very large bass boost for pos 1, and other issues for both.

"middle" is really bad (as expected) and "back of the room" is pretty bad too.

The best position is the one labeled "38%", as it has the smoothest overall response, and the best chance of being usable, with treatment. You might want to four other positions: about 12" and 6" in front of '38%', and about 6" and 12" behind it.

Overall, you need a lot more bass trapping in that room: the decay time below 100 Hz. is nearly one second in all cases! I would shoot from something between 300 and 400 ms for that room.

But there's a huge, major big problem with the way you are taking the readings: you did not calibrate REW with an external sound level meter! REW is showing that you conducted the tests at 150 dB which is impossible, of course! So you need to calibrate REW properly and do your tests at a level of about 80 dB for each individual speaker, which should automatically give you 86 dB with both speakers on.


- Stuart -

Hello Stuart,

I apologize for not writing for this long time.
After 4 years of study and 2+ years of DIY alone, my room is ready.

First of all, I would like to thank You for all Your priceless help You gave me. Surely, without You I would have done some major and irreversible mistakes. Especially the ventilation system, which by the way insulates 90 db at 100 Hz, I am grateful for Your advice and exaggerating further. Also for the advice regarding the distance between walls (28 cm), and 60 cm at the wall with windows and doors. It happens, that I work for the public health authority and have access to professional sound measurement devices, which show a final attenuation (C scale), of 80 db at 100 Hz. Which is amazing for the investment and the DIY [myself] involved. Surely the windows leak, as You have foreseen, but at 6 m distance from them, the reading is equal with the baseline noise in the city day and nighttime. In fact the best test, beside the db-meter, is the reaction of my neighbor, who never lamented at all for the noise, despite my playing metal at 3 am. And his house is at less than 2 m from my studio, and while building he promptly lamented each time I used a battery screw driver (just to have a reference). I have a drum set and 200 W bass amp that I sometimes use at 3 am with my band). It is true, we could not hear him+her lamenting anyway . But they have no idea, that I have a studio. Otherwise they would came to protest. Also, with all this insulation, I have no global warming issue, because temperature never went upon 20 Celsius degrades inside. I don't need an air conditioning at all. Sometimes I open the window nighttime to change air. Other wise, the vents change it in 4 minutes. My electric heating consumed about 1000 KWh total during winter (audio consume included), and kept temperature above 17 C [and here temp drops consistently under -30]. Reminder of the wall structure from out to in: 3 mm cement cover - 10 cm Rockwool MaxE, 30 cm brick(with holes), 10 cm URSA wool, 8-32 cm air, 10 cm Isover acoustic wool, 1 layer of 4layered aluminum, air, plastic heat membrane, 2 layers of acoustic gypsum board(heavy and expensive). All this on a 8 tone concrete floor on 4 cm Rockwool step wool, completely decoupled from the outside wall. And since I have done it myself, nobody screwed it up. Windows are 2x double glazed German second hand windows from the 90s at 60 cm distance from each other. These are the weak point, but since they are directed towards no neighbor they work perfectly. Doors done by "yours truly" starting form modified second hand German office doors with ladder and wool on them, redone the frame entirely, and added weight. In fact the outside door is unmodified, the inner is tuned up to 150 kg, and both with double rubber seal. Windows as well, with added rubber seal. So, I have overdone it, but it worth every penny. And as a reference, with absolutely every cost, the outer shell done by a construction firm, the permit, the bribery of officials, all materials up to the last nail cost 16000 euro. And 2 years of work almost every day/[and night].
Another myth busted: "economical" bulbs does not induce noise in the recording chain. First reading Newel's and Gervais's books I have installed wolfram bulbs, which consumed almost more than the heating. Then I have tried to change them. Nothing happened. I guess, if one does a real star grounding, with independent 36 m of 6x0.5 galvanized platband buried under the foundation, and all wires took from there and linked individually to each outlet by 3 mm2 copper wires eliminates all noise, despite the fact, than the light circuit was not grounded at all. I have used only 2 wires of 1mm2 for them. For the outlets I did all wires coming individually from the panel, with separate fuses. Nothing is divided.
Acoustics: Here I have some troublesome statements do make. 1. In Romania, there are no acousticians who worth jackshit. Furthermore: I am sure, that everything has a fully valid scientific explanation, but NOTHING IS BETTER THEN YOUR EAR to establish setup of stuff (speakers, sweet spots), if that works. And speakers sound much better in the corners, than anywhere else. In fact, I can hear amasingly well the music in my studio at low levels, and we can rehearse having crystal clear sound, without cranking the shit out of our gear and killing our ears [like we did before in other locations, because the bad acoustics made us do that]. Since I was a kid I could easily and effortlessly identify all sound pitches with 100% accuracy. On the other hand, I am PhD in life science, who worked 30+ years in prestigious research institutes (yes, you may say, so I am not a real musician, I agree), so I know something about data analysis and reliability. I can say without any doubt, that REW SUCKS BALLS. Reality has nothing to do with the graphs one gets, and probably that is why its free. In my humble opinion it does not worth to an amateur to invest in those kind of softwares [money and especially time]. I agree that sound and sensation it is subjective. But since I had a guy who owes a professional studio, who came to my place [long before I had this rehearsal room ready] to record voice in my bedroom [which had no acoustical treatment except a 3 mm layer of cork one entire wall, 2 other walls almost covered by book shelves with random crap on them, and had 4 speakers on 3 walls - 2 on 1 wall, and 2 on another wall 90 degrades, so 3 speakers upon each other in one corner] and he said, that it sounds much better, than in his professional studio, allow me to doubt the validity of those measurements. Also, I have 3 groups recording and hiring my establishment and preferring it to professional studios, despite the same [or more] price they pay for it, because of the sound, and they are amazed how quiet they may play and still hear every detail. I disagree, that one should not have a room signature to the studio sound. Why should all studios sound the same? I think it should sound good, not the same. I guess this is the just as the fact, that magnetic tapes sounds much better than any digital crap may come out from any studio nowadays. Why they compress everything to death, and all levels are equal? Listen to some Van de Graaf albums recorded in the '70s. It is complete somehow, no frequency is left unused, and still not overwhelming, allover level is rising and lowering. And is sounds excellent. One can listen 40 times to an album without getting bored or used to the sound. If you are listening music on the mp3 player or iphone, you lose all that, and that is the reason why "modern" recordings sounds the same regardless of genre [!!!], flat and boring. I just simply refuse this attempt to standardize my studio and make it sound the same with all the rest of them studios. I guess people back then went to Sound City or Abbey Road for a reason. And not only the brilliant gear and engineers. Also for the sound signature of the studio. And it is true, that nobody ever recorded since - a drum-set sounding as good as in Sound City. And they almost had no treatment! Except maybe the piss on the walls.
Despite of REW measurement, the spots I did identify by ear, sound much better, than the position where the nice almost flat graphs that I obtained. So, as I am a part of the flower-power generation, allow me to "flip the bird" to REW . We are musicians, and not spectrographs. It may be the fact, that my room is completely irregular, and REW maybe was done to assess regular rooms. I sincerely couldn't give a flying fuck. But I would like to share this experience to others, who are doing the reading for their future studios. In fact, if you are a big star [so you won't be on this site], you can afford proffesional help, and by all means pay them. If you are an "amateur" who have a good hearing [audiophile], than screw the theory, since is much more complicated [way too much variables], than worths studying. I am not sorry, that I bought the measuring mic [Superflux ECM999], which records excellent guitar cab. I surely would not buy ever any Behringer product, which usually suck, and generate a shitload of noise [including their noise gate ] But my message to future studio builder musicians [not deaf fucks]: TRUST YOUR EARS MUCH RATHER THAN SOFTWAREs. Each case, the goal of an amateur/semipro studio is to do some good demos, not to compete with the professional studios. You are plainly dumb, if you think, that you can do that [as gear and as well as experience]. So, in no way try to do your studio as I did min. It may not be the sound for you. Experiment yourself.
Please, don't take this as an insult. I respect science and also Everybody. In fact, on the acknowledgement list on my studio wall, there is also a "Hall of Blame" with "Stuart from Chile without whom this project would have been impossible" among others. Anytime, You will found Yourself in my area, You have limitless shelter, food an beer.
Thank You again and forever!
Tibi

If anyone needs details of photos, don't hesitate to contact me.
T

Thank you so much for posting that, Tibi! I always wondered what had happened to your project, and it's good to hear that it worked out so well for you.

It's always great to hear about the final outcome of studios built by forum members, especially when things work out like this, and you are satisfied with the results. I'm very glad that we could help, and thank you very much for your kind words about my part in this. Being able to play drums at 3 AM without bothering the neighbors at all is a major achievement: it's the dream of many drummers, and the fact that you succeeded is certainly great motivation for other drummers to learn from your thread: you have proven that it CAN be done, when you follow the solid sound principles of isolation.

It would be great if you could post some photos of how you did things, and how it worked out in the end: When you've done that, I'd like to add your thread to the list of "Successfully Completed Studios".

I wish you great success with your drumming, and if I ever find myself close to where you live, you bet I'll drop in for that offer of some beer and food.

Best regards,




Stuart