John Sayers' Recording Studio Design Forum Archive

Hi Stuart,

thanks for your quick and detailed reply!

Although I really really don't want to be one of those guys that asks for advice and then doesn't take it, I'm having to make an executive decision and for now I'm going to leave the flush mount speaker option. I know it will be messier to do it down the line, but I'm hoping there'll be another point when I can afford new monitors at which I could look into it. Right now I've pretty much run out of money (after buying materials for acoustic treatment) and time, as I need to have this room at least basically operational by the time the kids start their summer school holiday, as I currrently have a temporary setup in my living room

So, I've done a REW test to get the ball rolling, hopefully I followed the instructions carefully, I tried to read some other forum posts to see what mistakes us newbies were likely to make and hopefully avoid them (mains hum etc). On first look, to my novice eyes, the results look a little bizarre.... Perhaps I did do something wrong, but I thought I'd upload the file and perhaps you could give an unequivocal "yes you screwed up" or "you don't know what you're looking at" Test was with an Avenson Audio STO-2 mic (flattest in my collection) into Mbox Pro.

I cleared the room for the test, but unfortunately my cloud frames are too bloody big to put anywhere else, and the British weather isn't letting me put them outside! They don't have any insulation in yet, they are basically wooden frames with canvas (Camira Cara), and I put one at each side of the room against to wall to be as unobtrusive as possible. Perhaps they may have affected the results?

https://www.dropbox.com/s/d20ol16cs4vr3 ... t.zip?dl=0

Although I really really don't want to be one of those guys that asks for advice and then doesn't take it, I'm having to make an executive decision and for now I'm going to leave the flush mount speaker option

No problem! We'll always try to give you the best advice, but often there are overriding reasons why you can't take it. "No money" is a very valid reason. If you can't do the soffits now, then by all means postpone them until you can.

So, I've done a REW test to get the ball rolling, hopefully I followed the instructions carefully, I tried to read some other forum posts to see what mistakes us newbies were likely to make and hopefully avoid them (mains hum etc). On first look, to my novice eyes, the results look a little bizarre....

It's a bit unusual, but nothing way out of the ordinary. It looks valid, and clearly the room was absolutely empty when you did that test, correct? Not one single shred of treatment of any kind in there?

Test was with an Avenson Audio STO-2 mic (flattest in my collection)

That's fine. Good choice for a measurement mic. They don't come much flatter than that!

A couple of things about the way you did the test: first, you followed the REW instructions and did them at a level of 70 dB for each individual speaker, but I prefer to do calibrate and test at 80 dB for each speaker, which automatically gives you 86 dB with both of them on, and 85 dB just happens to be the "standard" level for calibrating studios and cinemas. It's also the level that many engineers like to mix at. And at that level, you are pretty much guaranteed of triggering all the modes that want to be triggered. So for all your tests from here on, please re-calibrate to get 80 dB for the "L" and "R" speakers individually. After you do that, do not adjust anything when you do the "LR" test.

Second: You don't need to save each test as an individual file: you can save a whole bunch of tests inside one single MDAT file. Each time you hit "Start Measure", it adds a new measurement set to another tab down the left hand side of the screen. Just make sure to re-name each test as soon as it is done (text box at the top of each tab), so you don't forget which is which. You can get something like 20 or so tests into a single MDAT file, which makes it easy to compare things when you are analyzing.

and I put one at each side of the room against to wall to be as unobtrusive as possible. Perhaps they may have affected the results?

Probably having some effect, but very minor compared to the huge undamped room response,which is thousands of times bigger. Sort of like comparing a speed-bump to Mount Everest... . At this point in the game, that just isn't relevant.

OK, about the actual data: You need new speakers! Or at least a sub. Those things have no low end at all. Below about 38 Hz, they die real fast. Amazingly fast: by 33 Hz, there's nothing left at all! As long as you don't need low bass, you'd probably be sort of OK with that, but if you ever need to mix a 6-string bass, grand piano, church organ, 10-octave keyboards, or anything else that hits the bottom octave of the musical scale, then you really do need something to fill in a bit down there.

Second, your modal response is crystal clear: 67.9, 73.2, 94.4, 104.9, 117.4, 132.3, 137.4, 151, 169, 191, 206. I bet if you plug your room dimensions into a mode calculator, that graph would match your data very handily.

I also bet your room is close to square... several of those seem to be occur in pairs that are very close together...

What are the final interior dimensions of your room?

The other thing that is crystal clear is the SBIR dip at around 79 Hz, and other smaller ones at around 96, 121, 158 and 213. I could do the math and figure out which dimension each of those relates to, but I'm lazy right now, and in a bit of a hurry, as I have deadlines to meet on a couple of projects I'm working on. But you can do the math: the 1/4 of each of those will be directly related to the distance between the speaker and one of the walls, referenced to the location of the mic. I'm betting that the huge dips around 79 Hz are related to the rear wall...

So what does all this mean?

1. Major treatment on the rear wall! Superchunks or hangers, for sure, plus whatever else you can throw at that wall. It needs to be killed. But you will also need something in front of those bass traps to keep the highs in the room: probably plastic will do the trick.

2. Large bass traps in several other corners. The front vertical corners, definitely, but perhaps also the wall-ceiling corners? I'd go for superchunks there too, at at least corner absorbers.

3. Cloud: It definitely needs to be hard-backed, and hung at as steep an angle as you can get within reason. And it needs thick insulation both below and above the hardback. I'd go for OC-703 below, and maybe on top as well, or at least thick "pink fluffy" on top. Here too I'd put thin plastic below the bottom absorber before you put the fabric on. Not so much for returning highs here, but more for preventing the insulation fibers from sifting down all over your gear over time... nasty stuff...

4. More treatment! But let's get to that later.

First do the above, in any order you like, but do another set of three REW tests at each stage, as soon as you have it finished, so you can check that it is working as planned. Do the test BEFORE you put the final covering on, if you can, so that do any modifications that might be needed before covering.

Why all this treatment? The target RT-60 time (or more accurately "decay time") for a room that size is probably around 200 ms (I'll figure it more accurately once I know the dimensions). Right now it is well over 1200 ms!

It's a boomy, screamy, clangy, shrill, roaring, hellish monster in there right now! And that's putting it mildly. It's BIG monster, so it's gonna need some serious taming. You have to get it down to a soft, dull whimper... That needs a lot of taming.

The GOOD news here, is that the overall frequency response isn't that bad at all, and there's definitely hope that it can become a really good room. But you have your work cut out for you!

- Stuart -

Thanks again for the speedy reply!

It's a bit unusual, but nothing way out of the ordinary. It looks valid, and clearly the room was absolutely empty when you did that test, correct? Not one single shred of treatment of any kind in there?

Yup, just computer, speakers and clouds in there, not a shred of treatment! I'm actually impressed with the length of the verb in here, it's like a cathedral!

I prefer to do calibrate and test at 80 dB for each speaker, which automatically gives you 86 dB with both of them on, and 85 dB just happens to be the "standard" level for calibrating studios and cinemas. It's also the level that many engineers like to mix at. And at that level, you are pretty much guaranteed of triggering all the modes that want to be triggered. So for all your tests from here on, please re-calibrate to get 80 dB for the "L" and "R" speakers individually. After you do that, do not adjust anything when you do the "LR" test.

Got it, thanks! Will do future tests at those levels, and save multiple runs in the same file.

Sort of like comparing a speed-bump to Mount Everest...

Haha! I like it

You need new speakers! Or at least a sub. Those things have no low end at all.

Yeah... they are Mackie hr624's, so not a whole load of bottom end thump. A sub will probably be on the cards, new speaker choice dependent. If I rob a bank and end up with some MicroMains.....

What are the final interior dimensions of your room?

The back end of the room is slightly odd, so I've added a quick sketch with dimensions, room height is 2.55m:

The other thing that is crystal clear is the SBIR dip at around 79 Hz, and other smaller ones at around 96, 121, 158 and 213. I could do the math and figure out which dimension each of those relates to, but I'm lazy right now, and in a bit of a hurry, as I have deadlines to meet on a couple of projects I'm working on.

Fully appreciated! Any time spent replying to me is time spent not earning on other tasks, so thanks again for your replies.

1. Major treatment on the rear wall! Superchunks or hangers, for sure, plus whatever else you can throw at that wall. It needs to be killed. But you will also need something in front of those bass traps to keep the highs in the room: probably plastic will do the trick.

I'm hoping I can do both, although it will be more heavily on one side of the room as I have an awkward rear wall door. I am currently thinking of trying to fit as many hangers as I can perhaps with superchunks above and below. Then perhaps also superchunk at wall-ceiling boundary. I also was thinking of putting some pallet wood (bit of a theme) planks widely spaced over rear wall treatment, hopefully this might help with the highs?

2. Large bass traps in several other corners. The front vertical corners, definitely, but perhaps also the wall-ceiling corners? I'd go for superchunks there too, at at least corner absorbers.

Definitely going with front corner superchunks, I may also do the wall-ceiling corners if more is needed.

3. Cloud: It definitely needs to be hard-backed, and hung at as steep an angle as you can get within reason. And it needs thick insulation both below and above the hardback. I'd go for OC-703 below, and maybe on top as well, or at least thick "pink fluffy" on top. Here too I'd put thin plastic below the bottom absorber before you put the fabric on. Not so much for returning highs here, but more for preventing the insulation fibers from sifting down all over your gear over time... nasty stuff...

Roger that! Noted.

t's a boomy, screamy, clangy, shrill, roaring, hellish monster in there right now! And that's putting it mildly. It's BIG monster, so it's gonna need some serious taming. You have to get it down to a soft, dull whimper... That needs a lot of taming.

The GOOD news here, is that the overall frequency response isn't that bad at all, and there's definitely hope that it can become a really good room. But you have your work cut out for you!

Yup, that pretty much sums up the sound right now!! haha The good news is that I've had a chance to give some music a blast in here today too, and the isolation seems to be really good, certainly enough for my needs here! Feels like I've just about crossed the first hurdle.

It's getting very exciting at this stage, and thanks again for your amazing input. As a local saying goes; You're one of the good ones!

Adam.

The back end of the room is slightly odd, so I've added a quick sketch with dimensions, room height is 2.55m:

That's fine. There's still space for some bass trapping. Make it deeeeeep!

I'm hoping I can do both, although it will be more heavily on one side of the room as I have an awkward rear wall door. I am currently thinking of trying to fit as many hangers as I can perhaps with superchunks above and below. Then perhaps also superchunk at wall-ceiling boundary.

It's OK to have asymmetric treatment for the low end, bu you you still should keep it symmetrical for high frequencies.

I also was thinking of putting some pallet wood (bit of a theme) planks widely spaced over rear wall treatment, hopefully this might help with the highs?

Yeah, you could do that on the rear wall. As long as they are widely spaced, and not tuned. (You love pallets, don't you? maybe you could call your studio "The Pallet Box"... )

thanks again for your amazing input. As a local saying goes; You're one of the good ones!

- Stuart -

Hello again!

So progress was quite slow over the summer with family holiday and the kids being off school, but I managed to make a little bit of headway.

I now have clouds up, so lights are in and also sockets are all fitted. I have also put in my front end superchunks, so it's starting to look a bit studio-like at that end!

I've done another REW test, perhaps if you get some time Stuart you'd kindly look over the results again? It looks a little odd to me still, especially the fact that the L and R speaker results don't seem to be the same, maybe you could shed some light??

https://www.dropbox.com/s/pe6rfri15kmao ... .mdat?dl=0

The test positions of the mic and speakers are the same, although you'll notice that I now have a temporary desk in with my iMac on. The iMac is currently in front of the speakers by about half a meter and is probably having a detrimental affect, I plan to make a stand and put the screen as close to the front wall as possible in the long run.

I've attached a picture of the front end during testing.

Look forward to your response and any advice you can give about further treatment. Next stop; back wall bass madness!

P.S. Have you got any reserved rights on the name "The Pallet Box" Stuart??

Thanks,

Adam

I realize that you are around the opposite side of the world from me, but there's really no need to post your picture upside down! I'm getting a really sore neck just trying to look at it...

I'm downloading the REW data now... I'll let you know what I see...


- Stuart -

Haha yeah I thought I post the photograph geographically correct (from your perspective).... Not sure why it did that.

Thanks for downloading my test, look forward to any thoughts you have.

Cheers,

Adam

Hi Stuart,

don't wish to hassle a busy man like yourself, but just wondering if you noticed anything particular from my REW? I'm hoping to tackle my bass traps in the next couple of weeks, so any wisdom you can impart would be much appreciated!

Ad

Adam, I'm not sure how I missed your thread for so long!


I looked at your new REW data, but I couldn't find the original empty-room data to compare against. So that's sad! But the new data looks good, valid, and shows some improvement with regard to what I recall form the original.

However, there's a big difference in response between the left and right channels. Not quite sure why, but possibly related in part to the rear wall that has no treatment yet.

The big conclusion I draw from this data is that you need a lot of bass trapping!




- Stuart -

Hi Stuart,

thanks for the reply and sorry for my slow response! Been busy here with the festive season and family, and progress has been relatively slow in the studio, partly due to actually doing some work in here!

My back wall still isn't finished, that's the next big push, so in the meantime I've put all my Auralex Maxwall panels in the back corner and the room sounds actually pretty darn nice

I'll have to do another test to see where I'm at, and also I'd like to look into making some side wall diffusers, so will need to check out the data for that. If I want to put side wall diffusers mid-way down my room to control flutter, would I need to do a REW test from that point in the room to determine which frequency range to design my diffuser around? I'm currently thinking a Skyline style or in the style of the Multifuser.

The big recent progress was building a custom desk for the room. I'm still a joinery novice but quite pleased with my efforts, it's made of reclaimed Scaffold boards and pallet wood (of course!!) It had to be now the studio is officially going to be called The Pallet Box haha! Do you get a cut for the name Stuart??

Thanks again for all your help so far on this long but rewarding project!

Ad

This looks very much like what I am looking to achieve. Very nice marked for later reading!

Update::

I've had another big push and found time/money to get on with my rear wall bass trapping etc.
I've made the frame and temporarily just stuffed it with the Auralex Max Wall which has been freestanding (and aesthetically annoying the hell out of me!) for about 6 months.
I've also made the canvassed frames which will slot over the top of the trap for the cosmetic finish, which has made the room finally feel like an almost finished studio!!
This buys me a little bit of time to consider the "guts" of the bass trap. My thoughts are currently:

::OPTION A::

A super duper mega chunk, stuffing the whole thing with layer upon layer of low density insulation. In which case, do you think this Earthwool Loft Roll 44would be suitable? http://www.knaufinsulation.co.uk/produc ... ft-roll-44

Does the density of the material have an exact correlation to it's effectiveness at specific frequencies? I know (now, cheers Stuart!) that in general that lower density is better for the low frequencies, just wondered how specific that is. i.e. should I wait until I've done a room test and know the specifics before even thinking bout ordering any insulation?

::OPTION B::

A combination of stuffing the frame with some slabs of low density stuff (like above) but also making some hangers to hang ceiling to floor in the frame.

It's a relatively small space, but I reckon if I put some thought into angling the hangers I could maybe squeeze about 4 in there. I am slightly concerned that as it's a relatively small trap space that the hangers wouldn't be as effective as just stuffing the whole space with insulation.

Any input at this stage would be greatly appreciated! I will be doing another REW test as soon as possible, just need a nice enough day to clear out all the drum kit etc and put it outside for a few hours

Thanks!

Ad.

. . . with layer upon layer of low density insulation. In which case, do you think this Earthwool Loft Roll 44would be suitable?

Looks like it might be OK, but what's the actual density? I could not find that in the specs you linked to. It just says "low density", but without specifying a number....

Does the density of the material have an exact correlation to it's effectiveness at specific frequencies?

Not a perfect linear curve marked precisely on a graph, no. There's lots of factors that come into play, and the curve is more bell-shaped than straight line: There's a point where lower density stops being better, and starts getting worse again. Very low density is as bad as high density. In other words, there's an optimum density for each application and each product type. However, it's a fairly gentle curve, so as long as you are "in the ball park", as the Yanks say, you should be OK. I would look for something around 40-50 kg/m3 if you are using mineral wool. As long as you don't go with 20 kg/m3 or 70 kg/m3, you should be fine. There's no need to be finessing the density to find the perfect point.

should I wait until I've done a room test and know the specifics before even thinking bout ordering any insulation?

Not necessary for bass traps, no. Just get reasonably good stuff, and pack it in thick.

That said, it's important to do a complete set of REW tests before you put it in, so that you have "before" data, showing the room response in all its ugly detail, then do another test as soon as the insulation is in, before you put the face on, to check how it is working, what it did right, and what it did wrong. You will very likely find that it is sucking too much of the highs out of the room, and you need to cover at least part of it with some type of plastic or other reflective surface, to get the highs back again. The "before" and "after" tests will reveal that to you, showing you what highs need to be brought back, and how much they need to be brought back, so you can decide on the thickness of the plastic and % coverage that you will need to control that.

A combination of stuffing the frame with some slabs of low density stuff (like above) but also making some hangers to hang ceiling to floor in the frame.

I would just stuff the frame full of it. There's not really enough space in there to get a good set of deep hangers.

I will be doing another REW test as soon as possible,

- Stuart -

Wow, thanks for the quick reply Stuart!

Stuffed corner of itch-wool it is then! I'll aim for 40kg/m3 and see what the best option is. I was planning on using some left over damp-proof membrane to keep the highs, though wondered whether it would be a little too thick, it's the 1000 gauge green stuff.

As you say, it's all speculation until I get a REW done, so I'll report back with that ASAP.

Thanks!

Ad

So, another progress report.

I went with the Knauf Earthwool rs45 Slabs, 150mm thick as the store had a bit of spare stock and I got a good price.

I've got all the insulation in, and I put on that spare damp proof membrane on over the top, though I suspect from the sound of the high end at the back of the room now that I may need to take some off or all and replace with a thinner plastic.

I've taken REW test at each stage, including with the fabric fascia back on, however I made one rookie error! (hopefully just one). In my haste to get chopping insulation, I forgot to to individual Left and Right speakers tests......doh.

I can see that the mammoth canyon I had at about 73hz is now a mere trough, but other than that I could do with a hand unpicking some of the specifics if possible?

Here is the REW file:

https://www.dropbox.com/s/w336p2cppul9v ... .mdat?dl=0

and here are the process pics:
Note - when I did the Partial Membrane REW test I only had the left side covered, I just forgot to take a pic like that! https://www.dropbox.com/s/w336p2cppul9v ... .mdat?dl=0