Garage Studio Build - Checking my plans are sensible

Hi, I'm about to build a studio room in my garage, in Hertfordshire, England. It will be for composing / mixing, so I'm planning some isolation for the room, to avoid annoying the neighbours if I work late. It won't be a recording studio, so will not feature live drums / guitar amps etc. The garage is a single-size, detached garage, brick built with a gable roof. 3m x 6m. The floor is concrete with a DPM. My plan is to build my studio at the back end of the garage, leaving a small amount of space at the door-end for storage. I've drawn some sketch up plans, and from what I've read on here, the design seems to make sense to me. But I could do with some help working out the details, and making sure that this is fundamentally sound. Here is my model of the garage as it currently stands. I have left off the garage-door end, due to sketchup shortcomings. The gable roof isn't shown, only the beams which currently run the length of the garage. I have included the side door - which will be my entrance to the studio, and opens out onto my garden. Apologies for my Sketchup newbishness: My plan is to use the three brick walls as three sides of my outer leaf, and then to add a stud wall, with drywall on the outer side, to create the 4th wall. I was intending to then use the beams currently in place to create a drywall ceiling. I assume I will need to find out if these beams are strong enough to take a ceiling. They are 2x4 beams, and span the length of the garage. I figure I should then end up with a box, which is my outer leaf. Dimensions W 2.84m x L 3.7m x H 2.51m The ceiling is not shown in these sketches, but would be attached underneath the beams and joining to the stud wall I then plan to build a 4 wall room inside this box, leaving approximately 10cm gap to the outer leaf. The new walls would be stud walls, with drywall on the inside. Beams spanning the 4 new stud walls would be for the inner-leaf ceiling, again with a 10cm gap to the outer leaf ceiling. I'm planning on installing a laminate floor. The inner leaf would have a 2nd door, with an air gap to the outer leaf door. HVAC I'm not panning on installing air-con. I'm sure my budget won't allow it. We do only get about one week of hot weather per year here, and I don't mind running a desk fan for that week. Ventilation however.... not an area I feel confident in, even though I've read plenty about it here. My initial plan is to run an inlet and an outlet duct, at either end of the studio. Then I guess the ducts run back through the gap between the leaves, to the Outer Leaf stud wall, to a pair of ports, with fans fitted. I have seen people build the staggered silencer / baffle boxes on here and I'd be happy to make some of those - they don't look too difficult. So my questions to you kind people are: 1) Have I made any major screwups here? Is this plan generally viable? 2) Is my ventilation plan sensible? How do I work out duct size / fan speed / etc? 3) Should the gap between the two leaves be left as an air gap, or should it be filled with more material? Which would provide better isolation? 4) I saw a post on here featuring a similar build, which mentions painting the brick on the inner surface of the outer leaf, for superior isolation. Is this right? If so, does it require special paint? 5) I don't quite understand how the door system works. How do you create a door frame between inner leaf door and outer leaf door, without coupling the two leaves together? Fabric? 6) Have I missed anything glaring here? If anyone has the time to reply on this I would be very grateful. Thanks. (PS - I haven't planned internal sound treatment yet - my plan is to make a somewhat-isolated room first, then measure inside and work out my sound treatment from there.)

I'm now checking to make sure I haven't accidentally designed a 3 leaf system here. i.e. between my 'Outer Leaf' and and the actual garage door and gable roof. My understanding is that if the air volume between the Outer leaf and the rest of the structure is big enough then the 3 leaf effect is not significant. Please tell me if I'm totally wrong here. The horizontal distance between my Outer Leaf stud wall and the door of the garage is 1.5 m The vertical distance from the Outer Leaf Ceiling to the top of the gable roof is 2m. The space at the garage-door end of the studio and in the roof cavity will be one big space, as the outer leaf ceiling in the design only covers the studio and doesn't extend the entire length of the garage. The plan is to use this spare garage space for storage. So all in all that gives me an air volume in the region of 47 cubic metres between the Outer Leaf stud wall / ceiling.....and the roof / walls at the end of the garage. Is this enough to negate a 3 leaf effect?

Hi there "RKML", and Welcome! It looks like I missed your first post somehow, so I'm glad you posted the update. :)

I'm planning some isolation for the room, to avoid annoying the neighbours if I work late.

It's best to put numbers to that: you need to define how much isolation you need, in decibels. It's easy enough to do, using a proper hand-held sound level meter (not an iPhone app!). ONce you know how much isolation you are getting right now, and how much you need in total, then it's easy to figure how much EXTRA you need, and how to get that, in terms of materials and techniques.

The garage is a single-size, detached garage, brick built with a gable roof. 3m x 6m. The floor is concrete with a DPM.

That's a good start, but tell us more about how that roof is built...

My plan is to use the three brick walls as three sides of my outer leaf, and then to add a stud wall, with drywall on the outer side, to create the 4th wall.

:thu:

I assume I will need to find out if these beams are strong enough to take a ceiling. They are 2x4 beams, and span the length of the garage.

I can already give you an answer to that question: They are not strong enough. 2x4s spanning 6m cannot carry any useful load at all. You would likely need something like 2x8, at least, to span that distance with a decent amount of mass. That said, I'm wondering why they are spanning the long dimension? It would be much better to have joists spanning the 3m distance: even 2x4's could carry a light load like that, and 2x6s would probably work fine for a higher load. It may be worthwhile looking into the possibility of raising those existing 2x4 ties (since that's all they are, apparently), then putting in larger joists cross-wise. If you can't do that for whatever reason, then you will probably have to "sister" those existing joists with 2x8s to get enough load-bearing capacity.

I figure I should then end up with a box, which is my outer leaf. Dimensions W 2.84m x L 3.7m x H 2.51m

Rather small! But if that's al you have, then it sure is better than having no place at all!

I then plan to build a 4 wall room inside this box, leaving approximately 10cm gap to the outer leaf.

If you build your wall "conventionally", as you describe, then you could probably get away with a smaller gap, maybe even as low as 2 or 3 cm. If you build your wall "inside out", then you could leave that 20cm gap, and then you'd have the advantage of having much of your treatment already in place! Have you looked into doing "inside out" construction?

Beams spanning the 4 new stud walls would be for the inner-leaf ceiling, again with a 10cm gap to the outer leaf ceiling. I'm planning on installing a laminate floor. The inner leaf would have a 2nd door, with an air gap to the outer leaf door.

:thu: Here too, you could do your ceiling "inside out", and gain several cm of ceiling height.

Ventilation however.... not an area I feel confident in, even though I've read plenty about it here.

You will need it! No doubt about that...

and I don't mind running a desk fan for that week.

You might re-consider once the studio is built and operating: with you, your gear, and your lights in there, in a totally sealed, very well insulated (twice.over!) small room, the temperature is going to rize faster than you'd imagine....

My initial plan is to run an inlet and an outlet duct, at either end of the studio. Then I guess the ducts run back through the gap between the leaves, to the Outer Leaf stud wall, to a pair of ports, with fans fitted.

That's the basic concept, yes, but you only need one fan, not two. It can go either on the supply duct inlet, pushing air through the system, or it can go on the far end of the exhaust duct, sucking air through the system. But you need to do the math to figure out the correct flow rate (volume) for your studio, and the correct flow velocity (speed), and the correct duct size, and based on that, the correct fan.

I have seen people build the staggered silencer / baffle boxes on here and I'd be happy to make some of those - they don't look too difficult.

If you need good isolation, you will definitely need two of those! Depending on how much isolation you need, you might even need four of them.

1) Have I made any major screwups here? Is this plan generally viable?

Generally you are on the right track! :thu:

2) Is my ventilation plan sensible? How do I work out duct size / fan speed / etc?

Start by figuring how many air you have to move (volume) based on replacing the entire air volume in your room about 6 times per hour. That tells you how many cubic feet per minute of air you need to move. Then consider that the speed of the air where it goes through the registers should not exceed 300 fps (feet per second), or it will create too much noise just from moving. Now you can calculate what size ducts you will need based on that ("What cross sectional area will allow that volume to move at that speed?)". Obviously, your fan needs to be rated to move that volume of air in CFM, at that speed, in FPS... but it also needs to be able to overcome the "resistance" of the ducts and the room, which is called "static pressure". There are ways for estimating static pressure based on duct diameter, duct length, number of turns, etc. Then it's a simple matter of checking that your fan can actually handle that static pressure, and still move the right volume at the right speed. Most fans come with a graph or table that shows how much air and what speed they can move it at, for each static pressure.

3) Should the gap between the two leaves be left as an air gap, or should it be filled with more material? Which would provide better isolation?

IT MUST be filled with suitable insulation, and even then it is still called an "air gap", because insulation is mostly air anyway! The purpose of the insulation in the cavity is to damp all of the internal resonances that would be happening in there otherwise, because resonance robs you of isolation. So if you do not damp the cavity, you allow those resonance to happen, and each of them kills some of your isolation. You need it. It is not optional.

4) I saw a post on here featuring a similar build, which mentions painting the brick on the inner surface of the outer leaf, for superior isolation. Is this right? If so, does it require special paint?

It is correct, and you can use pretty much any decent paint that will seal the porous surface of the brick. You can by good masonry sealer at most hardware stores, but almost any quality paint would work.

5) I don't quite understand how the door system works. How do you create a door frame between inner leaf door and outer leaf door, without coupling the two leaves together? Fabric?

Correct. The two frames do not touch, and you can simply wrap suitable insulation in black fabric, and press-fit it between the two frames. There are other methods too, but that one is cheap and easy.

6) Have I missed anything glaring here?

You are on the right track, for sure!

My understanding is that if the air volume between the Outer leaf and the rest of the structure is big enough then the 3 leaf effect is not significant.

Correct. It's a tuned system, and with very large air gaps, the frequency is so low as to not be a problem.

So all in all that gives me an air volume in the region of 47 cubic metres between the Outer Leaf stud wall / ceiling.....and the roof / walls at the end of the garage. Is this enough to negate a 3 leaf effect?

It's not really the volume that matters, but rather the straight line distance across the gap between the two leaves. The air in the gap acts as a spring, and that distance across the gap is what governs how "springy" the air is. You want it as large as possible. - Stuart -

I must start this post with an apology. Stuart, I am so sorry - you took time to reply in detail to my original post, and I am only replying now, 3 months later. Life got in the way of this particular studio build, literally in fact, in the form of a new arrival. In amongst the sleepless nights and baby-wrangling, all my energy and time for my studio design (and pretty much anything else) was completely diverted, and I have only now been able to return to it. Wow those small humans are high-maintenance! Nonetheless, it was discourteous of me to leave your post completely unanswered, so I sincerely apologise. An update on my studio: Having now no time or energy to devote to the build myself, and with new music projects and deadlines incoming in 2018, I asked a London studio-build company to do the garage conversion for me, and was able to negotiate a decent price. The design they presented was pretty much the same as what we discussed above, and the empty room is now complete. (EDIT Except the ceiling hanging from the long thin beams of course. As you said, they were not remotely strong enough. The outer-leaf ceiling was incorporated into the studio room build instead.) I'm very happy with the SPL isolation results. On testing with a handheld SPL meter, the ambient street / garden noise outside the garage was 55db. I then went in to the studio and played Highway To Hell at 101db. With the doors closed, the level outside in the garden at the side of the garage, and in the street at the front remained at 55db. A subjective test, using the Mk1 Earhole. Inside the studio, 101db was crushingly loud, louder than I would ever dream of working. Outside the front in the street I could hear: nothing. At the side of the garage in the garden I could hear the faintest whisper coming from the side door, but really, you wouldn't notice it unless you stopped what you were doing and concentrated. So I am delighted (and so will be the neighbours, the wife, the baby etc) As the build has left me with an empty room, now the sound treatment begins, and this I am going to do myself. First up I need to get some concrete blocks and sorbothane pads for my speakers to sit on, set up my Mac, and get REW running. I have bought a Presonus PRM1 for this. I've read the thread on calibrating REW, so will be following those instructions I've found some great info about my kind of room in these threads: viewtopic.php?f=3&t=20760&p=140411&hilit=cinder+block+speaker+stand#p140411 viewtopic.php?f=3&t=20798&hilit=concrete+speaker+stand viewtopic.php?f=3&t=21342&p=143964&hilit=concrete+speaker+stand#p143964 viewtopic.php?f=1&t=21357 but before I set up for REW, I haven't quite finished my research yet on listening position / speaker height / placement etc Is there a single thread that contains the theory on speaker placement so I can work this out, before I start with REW? My finished (small but hopefully usable) room is W 229cm x H 234cm x L 330cm Thanks, and sorry again for leaving you hanging! Owen

RKML wrote:

but before I set up for REW, I haven't quite finished my research yet on listening position / speaker height / placement etc Is there a single thread that contains the theory on speaker placement so I can work this out, before I start with REW? My finished (small but hopefully usable) room is W 229cm x H 234cm x L 330cm

Ah ha, I've just found this thread. viewtopic.php?f=1&t=20905&p=141412&hilit=speaker+placement#p141412 Which is enlightening regarding speaker placement.

I've come across 2 things I need to check. a) I can't run the Sorbothane app as it is only available for Windows. Would it be possible for a kind poster who has the app to run the numbers for my Neumann KH120s, and post a screen shot of the results, so I can workout what size pads I need, and what thickness? They are 6.2kg (13.7lb) b) The testing instructions for REW require that I leave the room before the test starts. This makes sense, in order to test the pure room sound. However, surely at any time during practical use of the space, the room is going to feature 200lbs of human, sitting in the listening position. Clearly this will affect the response, and is never going to be absent when the system is being used for critical listening. I'm wondering why it doesn't make more sense for me to sit in the listening position during the test, (head just out of the way of the mic), so that the room tests take my mass into account? Just curious. Thanks.

Life got in the way of this particular studio build, literally in fact, in the form of a new arrival.

Congratulations! That's a pretty big reason for taking a break from your studio design!

As the build has left me with an empty room, now the sound treatment begins, and this I am going to do myself.

Whoa! You hired a company to design your studio, and they gave you no design for the acoustic treatment, which is what makes or breaks a studio? :shock:

First up I need to get some concrete blocks and sorbothane pads for my speakers to sit on,

Have you considered flush-mounting ("soffit-mounting") your speakers? That's probably the best single thing you can do to your room to improve the overall acoustic result.

I have bought a Presonus PRM1 for this.

:thu:

I've found some great info about my kind of room in these threads:

Did you also find this one? : viewtopic.php?f=3&t=21122

Ah ha, I've just found this thread.

Just checking here, but did you read my response to the initial post, in the very next post? With a very small room such as yours, many of the "rules" in the initial thread do not apply to you, and many of the "caveats" in my response do apply. A lot of the "rules" are not really rules at all: just good starting points. There are many reasons why you might need to break every single one of those "rules", especially in a small room.

b) The testing instructions for REW require that I leave the room before the test starts. This makes sense, in order to test the pure room sound. However, surely at any time during practical use of the space, the room is going to feature 200lbs of human, sitting in the listening position. Clearly this will affect the response, and is never going to be absent when the system is being used for critical listening. I'm wondering why it doesn't make more sense for me to sit in the listening position during the test, (head just out of the way of the mic), so that the room tests take my mass into account? Just curious.

The main reason for doing the testing with nobody in the room, is for accuracy and reputability. If you see a change on one of the graphs after you install an acoustic treatment device, you would have no way of knowing if the change was due to the device itself, or due to you sitting 2" further back with your head tilted left, instead of right... Or because you did the first test while wearing a T-shirt, and the second while wearing a thick wool sweater and scarf.... You would be making decisions based on flawed data. Remove every single variable from the room, except for the treatment itself. For example:

(head just out of the way of the mic)

How would you achieve that? The mic is omnidirectional, so there is no place that is "just out of the way": it is affected by the proximity of pretty much anything. That's one reason why measurement mics are shaped the way they are: so that the body of the mic itself affects the measurements as little as possible, but even so it does have an effect. Small, but measurable. You can prove this to yourself by taking two measurements in the room with the tip of the mic in the exact same location, but flipped 180°. One test with the mic facing forwards, and the second test with the mic facing backwards, but otherwise identical position. So there's no place close to the mic where you could have your head without it affecting the mic, since the mic is picking up sounds from all directions. Any direction that you block with your head, is going to change the sound field, and therefore the measurement. When you do the testing, you must ALWAYS get the mic in the exact same location and orientation, accurate to small fractions of an inch. Also, it's a myth that the human body acts mostly as an acoustic absorber: it doesn't. It acts mostly as a diffuser. Think about what the human body is made if, and what the surface is like, and you'll find that there isn't a lot of potential for absorption! If you happen to be wearing thick porous clothing (eg, thick sweater and scarf...), then that will act as an absorber, yes, but the body inside the clothing is mostly a diffuser. Also, your body, seated at the mix position, is mostly in the shadow of the desk and console in any case (from the point of view of the speakers), and even then, diffusion is usually positive for the room, not negative. So when you eventually do add your body to the room, yes, it will have an effect, but it will be mostly positive, and not too pronounced anyway. The point of measuring the acoustic response without anyone in the room, is to ensure that the room itself is not coloring the sound, and that your treatment is doing what it is supposed to do, to get the response as close as possible to the ideal. Here's a couple of thread that show how the actual room tuning is accomplished, and what a good outcome looks like: viewtopic.php?f=2&t=21368 www.johnlsayers.com/phpBB2/viewtopic.php?f=1&t=21048 Those might help you get a more detailed idea of how the process goes, and what you can expect. - Stuart -

Soundman2020 wrote:

Congratulations! That's a pretty big reason for taking a break from your studio design!

Thanks, and cheers for you patience. Life has certainly been slammed sideways in some interesting and exciting ways! Now time to get the professional bit going vaguely forwards again :D

Whoa! You hired a company to design your studio, and they gave you no design for the acoustic treatment, which is what makes or breaks a studio? :shock:

Ha, yeah - and very much a question of budget. They did initially quote me for the whole package, including construction and then internal sound treatment / fitting, and it was way outside my budget. I figured the treatment is one part I'm up for doing myself, as an enjoyable project, and also something that fits a bit more with my DIY skill level. I'll enjoy learning about it as much as getting the end results My conversation with them ended up something like, "please make me an empty ventilated room in my garage which no sound gets in or out of," and that came in on budget so we did that. I could probably have got a local builder to do the same thing, based on the right principles and I did get some quotes, but in the end the studio company matched their quotes for construction alone, so it was a no-brainer. Treatment wise I'm planning for (although I don't want to pre-empt the REW data too much): * 60cm x 60cm x 84cm superchunks in the front two corners * A 10cm thick rockwool absorber panel between the super chunks on the front wall * Something at the top of the front wall along the join with the ceiling. * 10cm thick rockwool panel at the first reflection points on each sidewall (60x120cm) * Some sort of cloud - not yet designed * Whatever I can fit on the back wall. More panels? Don't know what's best at this point. I don't think I'll have space to super chunk the back wall corners, unless I use smaller triangles, maybe 30cm x 30cm x 42cm. I have no doubt this is the bare minimum (or even less than that) so I'll get the data done and go from there.

Have you considered flush-mounting ("soffit-mounting") your speakers? That's probably the best single thing you can do to your room to improve the overall acoustic result.

I know, and I'd love to do this as it's clearly the best acoustic option, and I did some research here about the designs etc. I've decided to wait on it for now, based on the time I've got available to me, and the potential for me screwing it up if I rush it! It's just too much of a project for me to take on right now. In the interests of getting the whole thing up and running as soon as possible (like this week if possible) I'm going with concrete blocks as the best possible 'quick' option. Soffit-mounting is definitely going on the list of projects I'll come back to later down the line when (if!) I ever have time to learn a bit more about carpentry, and take it to the next level. Maybe a summer project.

Did you also find this one? : viewtopic.php?f=3&t=21122

I did - I've just been re-reading it. Hopeful that I'll be doing my first set of tests this evening so I'm making sure I'm well acquainted with the procedure. Can't wait to see what an untreated W229cm H233cm L330cm room looks like. :shock:

Just checking here, but did you read my response to the initial post, in the very next post? With a very small room such as yours, many of the "rules" in the initial thread do not apply to you, and many of the "caveats" in my response do apply. A lot of the "rules" are not really rules at all: just good starting points. There are many reasons why you might need to break every single one of those "rules", especially in a small room.

I did - I found it very interesting. I've gone for a starting speaker position with the acoustic axis: * 130cm off the floor * 1.4m between L and R speaker * resulting in 30deg angle * with a listening position 1.3m back from the front wall. About 40% of the room length. I went for the axis at 130cm high as I'm 6'4" and I have to slouch in my chair to get my ears level with the recommended 120cm. 130cm is 56% of the room height.

The main reason for doing the testing with nobody in the room, is for accuracy and reputability. If you see a change on one of the graphs after you install an acoustic treatment device, you would have no way of knowing if the change was due to the device itself, or due to you sitting 2" further back with your head tilted left, instead of right... Or because you did the first test while wearing a T-shirt, and the second while wearing a thick wool sweater and scarf.... You would be making decisions based on flawed data. Remove every single variable from the room, except for the treatment itself.

Thanks - makes total sense.

Here's a couple of thread that show how the actual room tuning is accomplished, and what a good outcome looks like: viewtopic.php?f=2&t=21368 viewtopic.php?f=1&t=21048 Those might help you get a more detailed idea of how the process goes, and what you can expect. - Stuart -

Wow - That place looks incredible! What a great thread. Thanks for all your help here. I think I'm ready to go make some graphs. I'll post them here, hopefully later. One question - I've got the speakers intersecting 12" behind my head as suggested, so that they are pointing at my ears, not my eyes. The mic goes in the head position as I understand - not at the intersection point? If I'm correct, where in the imaginary head does the mic go? in the centre of the head between the ears, at the front / back etc? Thanks! Owen

Treatment wise I'm planning for (although I don't want to pre-empt the REW data too much):

That sounds like a good basic plan, except for the rear wall.... That's going to need a LOT of treatment... No, MORE than that! Keep thinking BIGGER! ... Still not enough.... Think HUGE! ... :) The rear wall of any studio is where the big issues will be. The smaller the room is, the bigger the issues. The rear wall is what will need your mist detailed attention. That's where you should start, not finish. Start with the rear wall, then move on to the rest once you have things reasonably under control at the back... See the other thread, to understand why this is so important. (I could not start with the rear wall for Studio Three, for other reasons, but we did go there eventually....)

I don't think I'll have space to super chunk the back wall corners, unless I use smaller triangles, maybe 30cm x 30cm x 42cm

They don't have to be equilateral triangles: If you can make them bigger in one direction, then do that. FOr example, if there's a door at 30cm along the side wall, then there's no problem with making them 30cm in that direction, but 60cm along the rear wall.... or 50, or 70, or whatever else works. Just make them as large and as deep as possible.

Can't wait to see what an untreated W229cm H233cm L330cm room looks like

In an empty room that is isolated well, expect it to look REALLY ugly! That's good, actually, as it shows up all the major issues in their fullest, most ugly splendor, clearly identifying what you need to do in the first round of treatment.

* 130cm off the floor * 1.4m between L and R speaker * resulting in 30deg angle * with a listening position 1.3m back from the front wall. About 40% of the room length.

Sounds reasonable, but the angle doesn't necessarily have to be 30°. If it works out that way, great! If it is 28 or 32, or some such, then that's great too.

I went for the axis at 130cm high as I'm 6'4" and I have to slouch in my chair to get my ears level with the recommended 120cm. 130cm is 56% of the room height.

:thu:

One question - I've got the speakers intersecting 12" behind my head as suggested, so that they are pointing at my ears, not my eyes. The mic goes in the head position as I understand - not at the intersection point?

Correct. Set up the mic so that the tip of the mic is at the point where the middle of your head will be when mixing.

If I'm correct, where in the imaginary head does the mic go? in the centre of the head between the ears, at the front / back etc?

Center, between the ears. Ir gives you an overall picture of what the lows and low mids will be like as perceived by your ears and brain when you are playing both speakers, and a rough approximation of what the high mids and highs will be like for each individual ear when you are playing the L and R speakers separately. If you really want high precision, then you could re-position the mic for those readings such that the tip is where each ear will be, with the mic oriented more towards the speaker than the center, but it's not usually necessary unless you want extreme precision. You can do that now, on the first "baseline" test if you want, as an additional test (in addition to the L and R readings with the mic centered), just to have the data in case you need it later: not a bad idea at all. But you don't need to do that for every single test set, until you get to the final stages of tuning. Be warned that the graphs for the normal L+R measurement will NOT show accurate graphs for the upper end of the spectrum, since there will be cancellation and comb filtering going on at the mic tip. There will be some rather large and broad dips and peaks up in the top end, but they don't actually exist in reality. You won't be hearing that in any case, since your ears are a couple of inches away from that spot, where those artifacts are not present. So ignore the top half of the graph when you are looking at the L+R measurement, since what you are interested for that one is the low end. - Stuart -

Here we go, I think I got this right. I followed the calibration info in the thread accurately I think. Brace yourselves... https://www.dropbox.com/s/qagwvh2tt8z6m ... .mdat?dl=0

Yup, looks about right: nice and ugly with huge dips and peaks in the lows... I'll download it, and take a quick look tomorrow if I have a chance. - Stuart -

Here's your basic "uglies" that are so nice, since they show you the major issues so clearly! Low-end waterfall: beautiful modal clarity, and probably SBIR too! Same data., different method for viewing it. Clarity! RT-60 off the charts! That's one ugly sounding room... And the least useful graph: Frequency response. Nice! I mean, ugly, but nice! However... are you CERTAIN you followed the instructions for calibrating REW? The levels are too low, but about 10 dB: Are you absolutely sure you did it right, at 80 dB per individual speaker, and checked that you got 86 with both? - Stuart -

Soundman2020 wrote:

Here's your basic "uglies" that are so nice, since they show you the major issues so clearly!...

Yeah - its pretty wild in there. Glad the graphs show the ugliness as expected! That 51hz mode is crazy in the room with a reference track playing - it sounds like I've got the world's worst sub speaker running at full whack.

However... are you CERTAIN you followed the instructions for calibrating REW? The levels are too low, but about 10 dB: Are you absolutely sure you did it right, at 80 dB per individual speaker, and checked that you got 86 with both? - Stuart -

I followed the instructions carefully step by step, and I'm 100% confident the HH was reading 80db per individual speaker, and 86 with both. I did have some issues with the input level during the calibration however. I did it a couple of times to try to get it right. I seemed to need the input trim on the sound card running very hot in order to get an input level of -18db showing in REW. I had the input gain on the sound card almost on full - which doesn't seem right. The pink noise 'Check Levels' function in REW (just before measuring) was ok with the trim set like this; it was reading -18db and the app was happy, but then when I then ran the sweeps the app reported clipping. It was as if the sweep was running louder than the pink noise. Or maybe I had the trim so high it was putting the system on the edge of clipping -no headroom left. To rectify this I had to back off the input gain slightly, -2 or -3 db, so I guess the final test was registering around -21db on the input. The SPL at the listening position was definitely still at 86 db LR. I can go back and do this again and try to figure it out. It's possibly a gain staging thing in the internal input settings of my soundcard, although I'm not sure what. My 'soundman brain' was searching to see if there was something silly running like a -20db pad in the input signal chain or something - but I couldn't think where. Having said that, my mental acuity has declined somewhat over the past few months of no sleep :D so it's entirely likely I missed something obvious.

Initial thoughts on Rear Wall. All rockwool panels 60cm x 120 cm The three uprights are 20cm thick The top one is 10cm thick. My thinking here is informed mostly by time pressure and simplicity for me to make on my own. I'm thinking "what can I do successfully, for most effect, in the limited windows of time I can get to do this right now?"

Although thinking again, it wouldn't much more work to do this, if it had appreciably greater effect:

Or this isn't out of the question: 20cm thick wall panels:

I'm thinking "what can I do successfully, for most effect, in the limited windows of time I can get to do this right now?"

Search the forum for "superchunk". Build two of those, large ones (at least 24" on the sides, bigger if you can), in the rear corners, another across the top in the ceiling/wall corner, and fill the rest of the wall with 6" of 703. Then do another REW test. - Stuart -

Soundman2020 wrote:

I'm thinking "what can I do successfully, for most effect, in the limited windows of time I can get to do this right now?"

Search the forum for "superchunk". Build two of those, large ones (at least 24" on the sides, bigger if you can), in the rear corners, another across the top in the ceiling/wall corner, and fill the rest of the wall with 6" of 703. Then do another REW test. - Stuart -

Will do. I’ll get on the case 2 quick questions: *In the UK the equivalent of 703 seems to be RockWool 45kg/m3. All good? *I can only come out 20cm from the wall at the sides because of the door frame. Higher up the thread you suggested that the triangles could be non equilateral and instead have longer sides along the back wall. If I can only come out 20cm from the wall either way, should I just fill the entire wall with 20cm of RW, right to the edges, as this would cover the entire potential area for Superchunks, and more. (Edit: I know 20cm is not at all deep in those corners, but it might be the best I can do in the space. Still worth doing?) Cheers, Owen

Rear wall done. 24" Superchunk at top of wall. As I couldn't fit superchunks in the corners I did the best I could and went for 'fill the wall with as much as I possibly can.' The whole wall below the top superchunk now has 30cm of RW 45 on it. Currently uncovered by fabric. It comes out past the door a bit, but you can squash it to open the door, and I just wanted to get as much on there as I could in the space. Here's the mdat https://www.dropbox.com/s/q7su6yhmw76eo ... .mdat?dl=0 I'm reading threads on here to educate myself on how to read these REW files. I feel like I understand the functionality of most of the graphs, but if anyone has any choice threads they can recommend on REW interpretation I'd love to read them. I know Stuart is generous with his knowledge and takes time to help, but I'm also very aware that this is an internet forum, and not 'Stuart's Free Acoustician Service!' I'd like to pull my weight if possible :) Thanks! Owen

Can you upload some real life pictures of what you've built and installed? I think you need more bass trapping to smooth things out more. That, or you have some extreme SBIR issues. Can you also post some physical measurements of your room (you've probably already done so) as well as speaker and measurement microphone placement? From there, someone might be able to determine if those deep nulls and tall build ups are SBIR related. Greg

Gregwor wrote:

Can you upload some real life pictures of what you've built and installed? I think you need more bass trapping to smooth things out more. That, or you have some extreme SBIR issues. Can you also post some physical measurements of your room (you've probably already done so) as well as speaker and measurement microphone placement? From there, someone might be able to determine if those deep nulls and tall build ups are SBIR related. Greg

Cheers Greg, I will do. I’m sure there’s huge SBIR going on, as there is 0 treatment at all on the front wall at the moment. The speakers will be banging their signal straight off the front wall and side wall. The only treatment in the room as yet is the 30cm rockwool coverage on the rear wall, with Superchunk at the top. The room is smaaaaaaall! It’s W229cm L330cm H233cm

Superchunk now installed in front corners. https://www.dropbox.com/s/qaot66v99juab ... .mdat?dl=0 The decay times appear to be stepping into line, but clearly that's a huge null at 100hz.

I know Stuart is generous with his knowledge and takes time to help, but I'm also very aware that this is an internet forum, and not 'Stuart's Free Acoustician Service!'

:thu: Thanks! Comment much appreciated! For 'Stuart's Paid Acoustician Service!', press the 'PM' button... :)

Here's the mdat

It looks like you changed all the settings on your DAW, so it is not possible to validly compare the two readings. There's a difference of about 7 or 8 dB in the SPL levels (this test was done 8 dB louder than the first one), which implies that you could have been triggering modes that were not triggered the first time, or could be triggering modes differently. That's over 5 times more energy you were pumping into the room, so it's probable that things were not excited in the same way. Here's the difference, when smoothed to 1/3 octave: So that's a problem. You need to go back and repeat the tests using the exact same setup and calibration you used for the very first test. - Stuart -

Superchunk now installed in front corners.

Whoa! Slow down! You are rushing way ahead of yourself! Take the time to analyze each set of REW tests completely, BEFORE roaring off full-steam into the next round of treatment... At least this time you did the test with the same levels as the second test, but they are both invalid as compared to the first test, so you don't really know what you have accomplished at all! In fact, according to the latest test you have already used too much absorption in the room overall, since your overall decay times are now too low across the spectrum, especially in the low end. You are now down around 140 ms for everything under 250 Hz, so before going any further, you need to deal with the issues that you have already created by over-treating.

The decay times appear to be stepping into line,

What decay time did you have in mind? it seems too low to me, even for a small room like that. You started out with nearly 900 ms EDT, and now you are down to 103.... For me, that's less than half what I would use for such a room. Why do you think that is "stepping into line"? :)

but clearly that's a huge null at 100hz.

Yup, and it will stay exactly where it is until you do something to treat it! So far, nothing you have done is anywhere near the location that is causing that problem... :) You have only treated the places that are NOT related to it, and until you treat the location that IS related to it, you won't see any change... - Stuart -

Soundman2020 wrote:

Whoa! Slow down! You are rushing way ahead of yourself! Take the time to analyze each set of REW tests completely, BEFORE roaring off full-steam into the next round of treatment.. In fact, according to the latest test you have already used too much absorption in the room overall, since your overall decay times are now too low across the spectrum, especially in the low end. You are now down around 140 ms for everything under 250 Hz, so before going any further, you need to deal with the issues that you have already created by over-treating.

Oh no... After all the months reading this forum, and now I'm that guy aren't I. Dammit. Left alone on my own on a Saturday afternoon, with no baby to look after and a stack of Rockwool at my mercy... :D Luckily it's not a problem to pull out what I put in - nothing is fabric-covered yet, and it's just held in place with tacks and twine at the moment. Everything is easily-modifiable.

It looks like you changed all the settings on your DAW, so it is not possible to validly compare the two readings. There's a difference of about 7 or 8 dB in the SPL levels (this test was done 8 dB louder than the first one), which implies that you could have been triggering modes that were not triggered the first time, or could be triggering modes differently. That's over 5 times more energy you were pumping into the room, so it's probable that things were not excited in the same way.

Yeah, I'm annoying myself here with my seeming inability to get this right. One thing I do know is that each time I test, the HH is definitely registering the speaker level as 80db on L and R, and 86 with both together. So hopefully the sweep tone is the same level, and is affecting the room the same way each time. I'm sure it's a mic input trim issue that is affecting the final levels that show in the tests I'll re-calibrate REW, and do a new set of tests, all with exactly the same settings - it won't take long.

What decay time did you have in mind? it seems too low to me, even for a small room like that. You started out with nearly 900 ms EDT, and now you are down to 103.... For me, that's less than half what I would use for such a room. Why do you think that is "stepping into line"? :)

:) I think that is me using a bit of 'British' understatement. What I meant was - the decay is nowhere near as huge as it was. I think I was a bit spooked by the original RT60 that went off the scale - so went over the top trying to bring the decay down. I have now done some reading on ITU/EBU recommendations and I have a clearer idea now why too little decay = also not ideal. Bob Gold's calculator gives *RT60 (ITU/EBU Control Room Recommended): 138 ms* for my room. I'm guessing this is 'recommendation' as opposed to 'hard rule'? I also don't know whether it's best to err above or below that number for given frequency areas.

RKML wrote:

but clearly that's a huge null at 100hz.

Soundman2020 wrote:

Yup, and it will stay exactly where it is until you do something to treat it! So far, nothing you have done is anywhere near the location that is causing that problem... :) You have only treated the places that are NOT related to it, and until you treat the location that IS related to it, you won't see any change... - Stuart -

Gotcha. If you don't mind fact-checking me - I've attempted to do some learning here.. (without getting ahead of myself) Room W 229cm H 233cm L 330cm If I'm reading the room-mode calculator correctly, the 52hz peak, and the 104 hz null are both being caused by the same axial mode - between the front / rear walls. 52hz = 6.6m 104hz = 3.3m One is boosting, one is nulling in my listening position. Have I understood that correctly? Then I've got the other big peak around 143hz, which I think corresponds to the axial mode between floor and ceiling? So in terms of potential treatment: I can see how an angled cloud with a hard back might sort out the 143hz, by essentially 'lowering' the ceiling, and putting the surfaces off parallel, so you no longer have an axial mode there. I don't know the solution to the front / rear axial mode. Maybe I'm barking up all sorts of wrong trees here! Thanks, Owen