Move My Studio Out of the Upstairs Bedroom

...and with a trembling hand on the mouse button as I hover over the Submit button... Here goes my first studio planning post. First of all, many thanks to all who have shared so copiously of your talent and expertise to help so many folks here on this forum, and for such a long time. I have been reading posts here for at least 8 years and have learned a great deal from the trials, tribulations and successes of others. I use my studio for mixing mostly, and record vocals and sax in the same room. I do not record live drums and limit my playback levels to 90 to 95db at the most, and usually mix around 85 to 90db. Because of this, I plan to be doing the very minimum amount of construction for the purpose of isolation. I will be putting my studio gear into a separate pier-and-beam building on my property about 35 feet from the house. I believe that the addition of an additional layer of OSB to the existing subfloor followed by laminate hardwood flooring, then adding a single layer of 5/8 drywall to the existing stud and drywall exterior walls with Green Glue and building up and sealing up the existing door will provide adequate isolation for my purposes. I plan to make a few test runs by setting up some playback speakers and monitoring the amount of sound that escapes the building to see if I might need to consider further isolation remedies. My room in this building is 189" long and 160" wide, with a 93" high ceiling with a raised center section that is 72" wide and runs the entire length of the room. These dimensions produced pretty good results on the Bob Golds Room Modes calculator. I chose to go with the 90-degree speaker layout to get the speakers a little further apart considering how close to the front wall the 38% puts the mixing center. Also, I plan to build the side slat walls all the way up to the ceiling. I just haven't yet figured out how to do this easily in Sketchup. My budget for all of this is pretty limited, hoping to do all of this under $5kUS. So, on to the first of what will surely be numerous questions: I have drawn hanger traps behind the speaker soffits on my plan (see attached pics), but I wonder if superchunks might work better. Any thoughts? Is my use of slat wall between the speaker soffits appropriate? Would the addition of a center wedge of slat wall against the rear wall be a noticeable improvement? ADVthanksANCE -Jack

I set up one of my EV's (ZLX-15A) and played some music through it at about 95-98db to take some measurements outside of the building with my Radio Shack sound level meter. Not surprisingly, the worst leakage is at the door. But even then, I have about a 20db drop about 6 ft from the east wall where the door is. This is more reduction than I had expected from a door constructed of one OSB panel and 2x4 framing behind it. The sealing around the edges definitely needs improvement. At the edges of my property line (which is about 90 ft from the studio building), I am seeing a maximum reading of around 70-73db which is about 15-18db above the nominal level between repeats of the tune I was playing inside. I plan to add a layer of 5/8 OSB to the east wall which has the door, and then an additional layer of 5/8 fire-resistant drywall with GG to all interior walls and ceiling. I will be building up the door with some OSB panels to add mass, as well as some Roxul for sound absorption. I will also add an additional layer of OSB subfloor glued to the existing plywood subfloor, followed by sound absorbing underlayment and laminate flooring. After several iterations of laying out the studio, I have decided to wait on the implementation of the speaker soffits. Attached is my current Sketchup image. ADVthanksANCE for any constructive criticisms. -Jack

I would also like to ask if anyone has any experience making the superchunks 48" across as shown below. It will require twice the amount of Roxul compared to making the superchunks 34" across, but I am wondering if the added expense would be worth the improvement in bass trapping. And, due to the underwhelming response to my design post, I must assume I am missing some critical piece of information. Could someone please let me know what information specifically that I need to add? ADVthanksANCE -Jack

Jack, Nice work with sketchup! I am not sure how much help I can be but I wanted to chime in since you have not had any replies yet. As far as isolation goes, from what I see you need to be 15-20 db lower at the property line? I am not sure if just adding 1 layer of 5/8 drywall will get you desired results. There is a lot of leakage through normal building practices so maybe going through everything and sealing it all up with addition of another layer of 5/8 would get you the results you need. I am sure there is someone smarter than me on here who can answer that. Otherwise the design looks pretty good to me. As far as acoustics go, I am not sure if the extra size superchunks will have a good cost to benefit ratio. It really all boils down to what treatment your specific room needs. There is no "fix all" acoustic treatment for every room. Your room needs to be measured and then treated accordingly. I hope this is somewhat helpful Ralph

Thanks for the helpful suggestions. You definitely bring up one point I had not considered which is measuring the room first and then decide on treatments required. Since the larger 48" wide superchunks are really just a super-set of the 34" wide ones, maybe I should put two in the main corners behind the speakers, then do a couple of measurements and find out how much they affect the room response. Film at Eleven. -Jack

Jack Im pretty sure an acoustician would measure the room with no treatments and then be able to determine what is necessary. I suppose you could also do it piece by piece but I believe that would take a lot longer.

Hi there Jack, and Welcome to the madhouse! Err, I mean forum! :)

...and with a trembling hand on the mouse button as I hover over the Submit button...

And I, for one, am really glad you clicked!

Because of this, I plan to be doing the very minimum amount of construction for the purpose of isolation.

OK, so sound getting out isn't a big issue, but what about sound getting in? Could any of the following noises mess up your vocal or sax recordings?: Thunder, rain, wind, hail, helicopters and/or planes flying over, dogs barking, traffic driving past / arriving/ leaving your place, people talking outside or elsewhere in the building, phones ringing, radio paying, TV, washer, dryer, vacuum, furnace, footsteps, doors opening/closing, and all the other million and seventeen randoms sounds that occur in and around typical residential areas? If you can honestly answer "No" to that question then you are all set! But if any of those might be an issue the day you finally lay down that very best soft, airy, ballad vocal, once-in-a-lifetime perfect recording, but with birds tweeting in the background and a door slamming right at the climax, then you really might want to re-think your isolation plans... :) I'm actually speaking from personal experience here! I once did have to track drums in a room where birds were nesting in the eaves, and splattered their tweeting all over my great recordings. It took me many days of careful spectral cleaning, liberal but judicious use of compression, and every other trick in the book (plus some that weren't in the book!) to get the tracks in a usable state. I would have killed to have had a nicely isolated live room for that session.... :cen: But anyway...:

I believe that the addition of an additional layer of OSB to the existing subfloor followed by laminate hardwood flooring,

What is under that sub-floor? Is it concrete slab on grade? If so, then just use that as your final interior floor. Or if not, then you might be in for some potential problems, since floors suspended over empty air cavities act exactly like drum heads.......

then adding a single layer of 5/8 drywall to the existing stud and drywall exterior walls with Green Glue and building up and sealing up the existing door will provide adequate isolation for my purposes.

Perhaps, but "believing" it will be so is not really a good way of designing a studio! :) You have to be certain that it will do what you need. I'd suggest that you should first identify exactly how much isolation you do need, in terms of decibels, then check your wall, floor and ceiling design against documents such as IR-761, IR-802, and similar things that can really prove to you whether or not it will. If you just guess about this, then there are only three possible outcomes: 1) you nail it, by pure sheer blind luck, and end up with just the right amount of isolation. If that happens, then run out and buy ever lottery ticket you can find around the planet before your amazing, incredible run of unbelievable luck runs out! 2) You sadly underestimated the amount of isolation, and the room is unusable for the purpose you wanted it for. 3) You sadly overestimated the amount of isolation, and spent a whole bunch of extra money you didn't need to, on isolating to a level that wasn't necessary. I'd put my money on Option 2, but I'd take a side bet on Option 3...

I plan to make a few test runs by setting up some playback speakers and monitoring the amount of sound that escapes the building to see if I might need to consider further isolation remedies.

Right, but once again that's only in one direction. You should also check the ambient levels around your proposed studio, at various times of day and various days of the week, until you have a good picture of what type of sounds you are dealing with, and how loud each one gets.

My room in this building is 189" long and 160" wide, with a 93" high ceiling with a raised center section that is 72" wide and runs the entire length of the room. These dimensions produced pretty good results on the Bob Golds Room Modes calculator

Right, but that's just the empty outer shell of the building: the numbers you actually need to plug into Bob's calculator are the dimensions of the final inner-leaf walls: the real hard, solid, surfaces that you will eventually see as you stand inside it after the room has been built, but before you put any furniture, equipment or treatment in there. Those are the numbers that actually matter. Plus there's the issue that the results are not 100% valid, since you have: "a raised center section that is 72" wide and runs the entire length of the room", which implies that the room is not a simple six-sided rectangle: Room mode calculators only give valid results for rooms that are rectangular and have only six sides. Your doesn't fit that, so the results you saw won't actually match reality. They probably won't be too far off, but you should be aware that they won't be totally reliable.

I chose to go with the 90-degree speaker layout to get the speakers a little further apart considering how close to the front wall the 38% puts the mixing center.

That's fine. That's good geometry still, but even so you don't need to go crazy about the 38% thing: it's a guideline, a starting position, a roughly decent location, but anywhere around that region will probably also be fine: 33% and 42% would probably be pretty close to the same, and so would 35%, or 41%, or.... you get the picture. There's a tendency when you start designing to try to hit all the numbers you read about, right down to the tenth decimal place, but there really isn't any need for that. Just stay away from the bad numbers, get close to the good numbers, and that's fine.

I have drawn hanger traps behind the speaker soffits on my plan (see attached pics), but I wonder if superchunks might work better. Any thoughts?

Stick with hangers, but only put them below the shelf that carries the speaker. Above that it would be much easier, not to mention cheaper, to just fill in the spaces around the speaker with any old scraps and left-over bits of insulation. And don't forget to leave a clear passage for ventilation, so air can move past the rear of your speaker to keep it cool.

Is my use of slat wall between the speaker soffits appropriate?

I wouldn't do that, no: I would either leave it as a reflective surface, or as an absorptive area, but not as a slot wall. That's a tuned device that will change the sound of the reflected energy, in both the time and frequency domains, which is not what you want to do so close to your head. In other words, it changes both the frequency response curve and the phase response curve, so what you hear coming of that wall will not be a good representation of the real sound. That's in addition to other effects, such as SBIR, comb filtering, edge diffraction, etc. On the other hand, if you soffit mount your speakers, all of those disappear.

Would the addition of a center wedge of slat wall against the rear wall be a noticeable improvement?

Make your entire rear wall thick absorption. The design concept you are following roughly so far, perhaps without knowing it, is called "RFZ", for "Reflection Free Zone": The idea is to force all the early reflections at the front of the room to follow paths that keep them clear of your head, and send them to the back wall, where they get mostly absorbed, but not entirely as you still do want some ambiance in the room. You are aiming to have no reflections get back to your head until at least 20 ms after the direct sound arrived, and even then to have the level of those reflections be about 20dB lower than the direct sound. By the way, I love your signature! Count me in the top 11%... :)

Not surprisingly, the worst leakage is at the door. But even then, I have about a 20db drop about 6 ft from the east wall where the door is.

Right, but you should be measuring at 3 feet, not 6 feet, because that's the "standard" distance for correct acoustic measurements. Actually it is 1 meter, but 3 feet is close enough. At 6 feet there would have been an extra 2 to 6 dB drop, so the real number for your wall isolation is probably around 15 to 18 dB. That's not very good at all.

This is more reduction than I had expected from a door constructed of one OSB panel and 2x4 framing behind it.

Mass law predicts about 26.8 dB of isolation for a 5/8" panel of OSB, or about 24.9 dB for a 1/2" panel, so you aren't even getting as much as you should be. So yes, your conclusion about the seals being insufficient is very correct.

At the edges of my property line (which is about 90 ft from the studio building), I am seeing a maximum reading of around 70-73db which is about 15-18db above the nominal level between repeats of the tune I was playing inside.

What is the limit set by your local municipal regulations, and how is that supposed to be measured? Get a copy of those regs, and check: you might be surprised at just how low the limit is at night an weekends. I'm betting it is way lower than 70 dB.

I plan to add a layer of 5/8 OSB to the east wall which has the door, and then an additional layer of 5/8 fire-resistant drywall with GG to all interior walls and ceiling.

That would increase your isolation by about 6 dB in an ideal perfect theoretical world, more like 4 to 5 dB in the real world. Adding additional mass to an existing mass means that you are governed by a principle of physics known as "mass law". Basically, it says that each time you double the mass of a single-leaf sound barrier, you get an increase of 6 dB in isolation. The actual equation is: TL = 20 log (F * M) - 47 dB Where: F = frequency (in Hz), M = mass per unit area of the barrier (kg/m²)

I will be building up the door with some OSB panels to add mass, as well as some Roxul for sound absorption.

The same applies here: mass law means that adding another sheet of OSB would increase your isolation from 20 to 26 dB. Doubling the mass again (another TWO sheets added to the existing two) will give you an extrea 6 dB, taking you to 32 dB. Adding another FOUR sheets to the existing four, will take you to 38 dB. adding another EIGHT sheets to the existing eight will get you to 40 dB. But a door made of sixteen layers of OSB might not be what you were expecting... :) There are better ways of getting good isolation that don't involve doors 10 inches thick...

After several iterations of laying out the studio, I have decided to wait on the implementation of the speaker soffits.

The basic geometry, symmetry and layout look just fine. I would add superchunk bass traps in the two rear corners, and do soffits for the speakers, which you seem to be planning to do anyway, but the rest seems fine. I'd also get the speakers off those boxy bases and onto hard, massive, solid stands, with a decoupling layer between. But apart from that, it looks good.

I would also like to ask if anyone has any experience making the superchunks 48" across as shown below. It will require twice the amount of Roxul compared to making the superchunks 34" across, but I am wondering if the added expense would be worth the improvement in bass trapping.

It would definitely be worth it, if you have modal issues on the low end, and since it is a small room it WILL have modal issues in the low end. So yes, I would do that, if you can. The larger size means that they will work down to lower frequencies, and the greater depth also means that the modal damping effect should be larger. The only downside to large superchunks is that they also suck out more mids and highs from the room, along with the lows, so it's a good idea to put a partial membrane in front of the superchunks, to keep some of the highs in the room. There are several ways of doing that. You might even want to consider some type of diffusion in front of them, since your room is borderline big enough to do that.

And, due to the underwhelming response to my design post, I must assume I am missing some critical piece of information. Could someone please let me know what information specifically that I need to add?

It's not you! It's just that there aren't too many people responding to threads lately (I sure wish more people would chime in!), and I'm a bit snowed under with my own "real life" workload right now, so I can't give as much attention to the forum as I'd like. You've been doing everything fine!

Im pretty sure an acoustician would measure the room with no treatments and then be able to determine what is necessary.

maybe I should put two in the main corners behind the speakers, then do a couple of measurements and find out how much they affect the room response.

Both comments are actually right!! :) 8) :roll: :shock: :!: Meaning that it's a great idea to measure the empty room first, with nothing in it except speakers and the measurement mic, then put in the first round of "standard" treatment and measure again, to see how well that did it's job and what else you might need to do. You can go several rounds like that if you want, tweaking the treatment with each round, but you soon get to the point of diminishing returns, where each new round of treatment makes less difference that the previous round, and is harder to design / more expensive to make. Normally three or four rounds is about where you'd want to stop. One reason why it's better to do it this way, with "successive approximation" instead of basing all the treatment on the first reading, is because each new layer of treatment can unmask problems that were hidden in the early measurements. You start seeing details that were lost in the "mush" of the empty room the first time round, but become clearer once you have cleaned up that mush. - Stuart -

Stuart, firstly thank you VERY much for your well thought out and comprehensive reply.

what about sound getting in?

Fortunately, I live in a relatively rural area where I have 1.25 acres, as do my neighbors on both sides for several lots each way, and my neighbor's house accross the street is nearly 400 ft from my house and another 35 ft from my studio out building. The neighbors on either side are easily 150 ft from the studio out building as well. Plus, our subdivision is outside the city limits and are bound only by the restrictions imposed at the county level, which is to say not many.

Thunder, rain, wind, hail..., dogs barking

Yes, we're gonna get those on occasion, and the barking would likely be coming from my own dogs.

helicopters and/or planes flying over

Practically never.

traffic driving past/ arriving/ leaving your place

Very seldom. Even during prime drive time, there are only six residences beyond my house and the nice folks there are mostly retired, like me.

people talking outside

That I hadn't considered, but if they are on a neighbors property, if would have to be a knock-down-drag-out confrontation for me to hear it when inside.

or elsewhere in the building, phones ringing, radio paying, TV, washer, dryer, vacuum, furnace, footsteps, doors opening/closing

All of that is pretty much why I am building my studio in an outbuilding away from my house proper.

I'm actually speaking from personal experience here!

In our former residence, I did get some dog barks on a couple of sax tracks that forced retakes. But since my recording setup there was not in a fully walled-in space, this was to be expected. Again, this is one of the reasons for moving the studio out from one of the rooms of the main house.

What is under that sub-floor?

Probably the worst case scenario. The two-room outbuilding is pier-and-beam construction on a sloping grade that makes the larger of the two rooms where the studio will be about 6-7ft above grade. I have consulted with a structural engineer (the guy we bought the house from) about the piers and beams under the building, and he is very confident that everything I plan on bringing into the room would even approach a marginal load on the structure. BUT (there's always a very large but)...

floors suspended over empty air cavities act exactly like drum heads...

This is why I have considered adding additional piers to support 2 additional longitudinal beams under the floor joists that run side to side.

"believing" it will be so is not really a good way of designing a studio! You have to be certain that it will do what you need.

Well, this is exactly what consultations with The Illuminati on this forum are for: to shed light into the unimaginable darkness of us DIY'ers trying to get Ocean Sound on a tunafish budget. >8]

there are only three possible outcomes: 1) you nail it, by pure sheer blind luck

Not too likely, I must agree.

2) You sadly underestimated the amount of isolation, and the room is unusable for the purpose you wanted it for.

Considering that my previous studio setup in a 3-walled room provided some degree of useful work, just about anything I do in the outbuilding is going to be better than that setup was.

3) You sadly overestimated the amount of isolation, and spent a whole bunch of extra money you didn't need to, on isolating to a level that wasn't necessary.

See reference to The Illuminati a few paragraphs back. Hopefully I can arrive at some place between scenarios 2 and 3.

the room is not a simple six-sided rectangle: Room mode calculators (paraphrasing here) results will not be totally reliable

This is a very important point you make for me here, as it reinforces how necessary my own measurements will be.

you don't need to go crazy about the 38% thing: it's a guideline, a starting position

That's very good to know, as well as...

Just stay away from the bad numbers

It would be really good to know what those are as well. I am guessing here, but based on looking at room mode spreadsheets, 50% is pretty bad, right?

Stick with hangers, but only put them below the shelf that carries the speaker.

Will do.

so air can move past the rear of your speaker to keep it cool.

This should not really be necessary for passive speakers, right?

leave it as a reflective surface, or as an absorptive area, but not as a slot wall.

Very informative, all of that paragraph.

Make your entire rear wall thick absorption.

Will do. Yet another very significant paragraph.

Right, but you should be measuring at 3 feet, not 6 feet, because that's the "standard" distance

Look for more measurement results pretty soon.

There are better ways of getting good isolation that don't involve doors 10 inches thick...

With a little further study, I found the info about using MDF for making your own doors. I am going to basically build an entire door using two sheets of 3/4 MDF and use the my existing door, which has a single 3/4 OSB front with 2x4 framing behind.

I would add superchunk bass traps in the two rear corners

Sadly, this is not possible, as the door is in the left rear corner of the room. I will have a 4ft wide one in the right rear corner and a 34" wide one at the ceiling/rear wall junction. Can you recommend a good alternative?

(re - 48" wide superchunks) It would definitely be worth it

Very good to know. I have included the additional materials in my preliminary budget.

The only downside to large superchunks is that they also suck out more mids and highs from the room, along with the lows, so it's a good idea to put a partial membrane in front of the superchunks, to keep some of the highs in the room.

Would something like the attached diffusors work in front of the rear superchunk? Can you give me some links to any other types of "partial membranes" or other diffusion devices that might work?

it's a great idea to measure the empty room first

Yet another great suggestion. After considering your numerous recommendations here, I am working on revisions to my Sketchup plan. Thanks again for your efforts on my behalf. -Jack (humbled but happy in central Texas)

The two-room outbuilding is pier-and-beam construction on a sloping grade that makes the larger of the two rooms where the studio will be about 6-7ft above grade.

Hmmmm.... not so good, as you suspected. Is that crawl space under your floor open to the outside world? Or is there a basement or cellar or something down there, underground?

I have consulted with a structural engineer (the guy we bought the house from) about the piers and beams under the building, and he is very confident that everything I plan on bringing into the room would even approach a marginal load on the structure.

If he's a qualified structural engineer, then get him to do a proper report on that, and sign it! Ask him to specifically state the current live and dead loads, and the maximum allowable live and dead loads for the floor system and foundations, as they are right now. That will be very useful info for you, when figuring out your materials: Knowing exactly how much extra mass you can add safely would be excellent.

Well, this is exactly what consultations with The Illuminati on this forum are for: to shed light into the unimaginable darkness of us DIY'ers trying to get Ocean Sound on a tunafish budget

Yeah, but we have to teach you the secret "fishtail" handshake first, before we can reveal our deepest mysteries to you! And you have to learn the most important veiled enigma incantations too: "2-leaf good, 3-leaf bad" and "More mass! More mass!" and "Caulk that gap!" are among those... Repeat continuously, day and night, awake and asleep, until your room is finished. Not just anyone gets to our Illumination, you know! :)

Hopefully I can arrive at some place between scenarios 2 and 3.

You sure can. There's lots of info here on the forum about how to do that, and links to publications that go into more detail, if you need it.

It would be really good to know what those are as well. I am guessing here, but based on looking at room mode spreadsheets, 50% is pretty bad, right?

Right. 50% and 25% are the worst, in all three planes, so the spot exactly in the middle of the room all ways around, is the worst of all. The problem is, your head has to be on the center-line (side to side) since symmetry is critical for stereo imaging, and your head has to be 1.2m above the floor while most ceilings are 2.4m high (do the math...), so that only leaves you with front/back location to try to make the best of things. There is also the issue of where the speakers are: they will likely only excite modes that terminate close to their position in the room, which should also not be at 25% or 50% of any of the room dimensions, but often have to be due to practical restrictions.... so it gets a bit complex!

This should not really be necessary for passive speakers, right?

Perhaps. To be certain, wrap your speakers in thick insulation (sides, top, bottom, and back, but not front), then run them for a couple of hours at a level higher than you normally use, and check the temperature of the rear panel of the speaker every few minutes. If it gets warm, then you need ventilation.

Sadly, this is not possible, as the door is in the left rear corner of the room. I will have a 4ft wide one in the right rear corner and a 34" wide one at the ceiling/rear wall junction. Can you recommend a good alternative?

Some people here on the forum have made "superchunks on wheels", that they can move into position where the door is for critical listening, then roll out of the way for door access, and for non-critical tasks. Another thing to consider is that rooms have 12 corners, not just the 4 vertical ones that come to mind: so you could put a superchunk horizontally across the top of the back wall, in the wall/ceiling corner, or across the bottom of the front wall, in the wall/floor corner, or on the side walls, or in any of the other corners.

Would something like the attached diffusors work in front of the rear superchunk?

Those are strange things, and I've never been too convinced about the theory behind them: they seem to follow typical QRD math, but they don't have the very necessary wells, that are needed in order to work. Confusing.... Diffusers are generally not recommended for small rooms, though. Or rather, diffusers based on numeric sequences aren't recommended, since you can't get them far enough away from your ears to avoid the lobing effects. They are great for large rooms, but not so much for small rooms.

Can you give me some links to any other types of "partial membranes" or other diffusion devices that might work?

Sometimes it's as easy as stapling strips of thick plastic across the front with gaps between. For example 6 mill vapor barrier plastic. Another option is broad wooden slats attached to the front, with very large gaps between them (several inches). More serious cases might need thin wood panels covering most of the trap, but angled carefully to keep reflections away from the engineer. There are several options.

After considering your numerous recommendations here, I am working on revisions to my Sketchup plan.

I'm looking forward to seeing that. - Stuart -

After many, many hours in front of the computer, I am starting to get a handle on Sketchup. Here are a couple of images after having reconsidered how to build the speaker soffits.

Is that crawl space under your floor open to the outside world?

Yes, it is. The current exterior of the under space is lattice panels. I have also included a picture the speaker unit from John Sayer's studio components Sketchup file, which was the inspiration for the soffits I have drawn. I have attempted to include all of the various updates that Stuart recommended in previous replies, including a hinged superchunk that pivots on the wall just inside of the entry door. It will probably need some framing that I haven't yet drawn and some kind of roller opposite the hinge and right at the inside corner as well. John's speaker unit shows only a single panel of what looks like OC703 behind and under the chamber where the speaker is located, and I have followed suit, including a single layer of the 7 1/2" thick Roxul I plan to purchase. Does this seem to be on the right track or am I totally off base somewhere? Also, as I have drawn the speaker units and slat walls the same height as the lowest part of my ceiling, what should I do with the space above where my ceiling goes up another 20"? I have put a smaller superchunk-style trap at the ceiling-front-wall junction, but I really don't know what should go above the speaker units. ADVthanksANCE -Jack (suffering from tired mouse in central Texas)

After many, many hours in front of the computer, I am starting to get a handle on Sketchup.

IT takes a while, as some of the concepts are a bit strange, but once you get the hang of it, it's a very powerful, useful tool. And you sure do seem to have gotten the hang of it!

Yes, it is. The current exterior of the under space is lattice panels.

OK, that's reasonably good news. So probably massing up the floor and putting some damping in there would be your best bet. Unless you feel like blowing a few grand on a proper floated slab.... :shock:

including a hinged superchunk that pivots on the wall just inside of the entry door.

That's actually a pretty cool solution you have there! I was even thinking that it probably wouldn't be too hard to have some type of mechanism attached to the door itself, that moves the superchunk out of the way automatically, as you open the door...

John's speaker unit shows only a single panel of what looks like OC703 behind and under the chamber where the speaker is located,

Right. The purpose of that is to control reflections that are coming off the back of the console or desk.

Does this seem to be on the right track or am I totally off base somewhere?

Definitely on the right track! Keep in mind that the soffit has to be very rigid and massive, such that it cannot vibrate. So beef everything up as much as possible. And don't forget to put hangers in the space under the speaker shelf.

Also, as I have drawn the speaker units and slat walls the same height as the lowest part of my ceiling, what should I do with the space above where my ceiling goes up another 20"? I have put a smaller superchunk-style trap at the ceiling-front-wall junction, but I really don't know what should go above the speaker units.

Fill those with insulation as well, and cover the front with fabric. You can always use more bass trapping in a small room, and that is a prime piece of real estate right there: it's a tri-corner! One other thing: your speakers should be offset a bit from the center of the front panel, to improve the acoustic response of the soffit unit as a whole, and it's interaction with the walls. - Stuart -

your speakers should be offset a bit from the center of the front panel

Should the offset be towards the center or towards the sides? And how much? It must be relatively slight because it is not obvious in any of the images I have seen or the descriptions I have read so far. I guess I haven't read enough yet. -Jack

Should the offset be towards the center or towards the sides?

It doesn't really matter: whatever fits your room best.

Should the offset be towards the center or towards the sides?

2/5 of the front baffle is about optimal, if you can make it that far. If not, then just go as far as you can: anything is better than nothing.

It must be relatively slight because it is not obvious in any of the images I have seen or the descriptions I have read so far.

The issue is that if you put a speaker in a perfectly symmetrical baffle (for example, in the middle of a circle) then you create a sort of "focusing" effect directly ahead, of frequency response. If you have a different distance from the speaker to each edge, then the response is more even and better spread. If you download the baffle designer ("Edge") and play with the parameters for positioning the driver on the baffle, you can clearly see this issue: The closer you put the driver to the center, the worse the response is. That's why most speakers do not have any drivers close to the center o the front baffle: they are spread much closer to the edges than the center. And since a soffit is just a big baffle, the same principles apply. Barefoot can probably explain this much better than I can, but I haven't seem him around on the forum lately. - Stuart -

2/5 of the front baffle is about optimal

That's 40% of the front baffle of the speaker, right?

Keep in mind that the soffit has to be very rigid and massive, such that it cannot vibrate.

Like 2 pieces of 3/4 plywood? I'll probably use OSB behind and a pretty one in the front.

Fill those with insulation as well

When you say fill, you really mean fill, like in this image? The panel under the speakers is the only non-filled cavity because it will have hangers behind. I calculated the angle for the slat walls as 17.5 degrees, which is half way between 12 degrees (for a 60 degree setup) and 22.5 degrees (for a 90 degree setup). Is that correct? Thanks very much for your help and the sharing of your considerable expertise. -Jack

This is a view of the rear chamber behind the speaker shelf. I have drawn panels of 7 1/2" thick Roxul attached behind the front walls. Will this be sufficient or should this area also be totally filled with Roxul? ADVthanksANCE -Jack (room demo almost done in central Texas)

Anyone??

Will this be sufficient or should this area also be totally filled with Roxul?

That's probably fine, but "more is better". You can fill the entire cavity if you want: I normally suggest using it to dump all your insulation off-cuts from the entire studio. Each time you have a left over piece of any type of insulation while you are building the walls and ceiling, hangers, bass traps, or anything else, then save it in a big bag until you have the soffits done. Then pour the contents of the bag into the cavity... - Stuart -

While I really like the idea of putting the scraps to work, I recently saw the sample shown below. Would putting full height hangers here be better use of the space for bass trapping? I also need to post some pics of my more recent Sketchups of the room. ADVthanksANCE -Jack (still drawing Sketchups in Bastrop, Tx)

Would putting full height hangers here be better use of the space for bass trapping?

You can certainly do that below the speaker shelf, which is exactly what John usually does with his soffits (take a close look at his sample), but it's not much use doing it above the shelf, as the hangers would be behind the infinite baffle, sealed off from the room (except for the tiny speaker ventilation slots). - Stuart -

And finally, some progress. Ain't it funny how life gets in the way sometimes... The drywall is all done (walls and ceiling have additional 5/8" with Green Glue, 26 sheets, 24 tubes) and so is the flooring (additional 3/4 OSB subfloor with subfloor adhesive and laminate flooring with thin foam underlayment). I had a choice of either filling in an existing hole in the front wall where an huge exhaust fan was mounted or putting in a window so I can look out at my many backyard trees, so I opted for the window. See photo below. I also ran the initial measurements with REW. See links below. Right side only https://dl.dropboxusercontent.com/u/44731396/MT%20Room%20Right.mdat Left side only https://dl.dropboxusercontent.com/u/44731396/MT%20Room%20Left.mdat Both together https://dl.dropboxusercontent.com/u/44731396/MT%20Room%20Left%20and%20Right.mdat Please checkout the images from my most-recent Sketchup design. Since I have no idea how to read much of the data in the mdat files, I am asking for any assistance The Illuminati can provide. ADVthankANCE -Jack

Anyone??

Jack, with REW you can save multiple test results inside one single MDAT file: you don't need to create separate files for each test, like you did here. There are also some issues with the way you did the tests: You are starting the seeps from 0 Hz, which isn't necessary and just clutters the files with unusable data. Start the sweeps at about 20 Hz. You are also ending the sweeps at about 15 kHz, but you really should run the all the way up to 20 kHz. In addition, then test for both your left and right speakers only goes to 4 kHz!, so you are missing the entire top two and a half octaves of the audio spectrum. Run all tests from 20 Hz to 20 kHz. You also seem to be running them at a level that is too low. Assuming you calibrated your setup correctly, right now you are running them at around 70 Hz, but you should really be doing them at around 80 Hz, to increase the SNR and also make sure you are testing the room at the typical level used for critical listening. That said, there are still some pretty clear points visible your REW graphs. First, the modal response is really obvious, and quite scary, so I'm guessing the room was absolutely empty when you did those tests, right? That's actually good, because the room response is pretty clear. Several modes are behaving exactly as expected, especially the first few axials. The frequencies are all a bit higher than predicted (based on your original dimensions that you mentioned in your first post), so I'm guessing that the room ended up a bit smaller than you expected, or that you did the angled side walls and ceiling? Got any photo's of the room as it is now? Also, please post the final inner dimensions of the room. One other thing I noticed; there's a fairly large difference between your left and right speakers: are you sure you had them set up perfectly sympathetically? Is there anything in the room that is not symmetric? Are the speakers themselves identical? There's probably a reason for the lack of symmetry, and you should try to figure it out. OK, about your treatment design: you seem to be planning to do slot walls on the angled front sections, between the speaker soffits and the side walls. Personally, I wouldn't do that, as you'd be changing the frequency response of the reflected sound, due to absorbing some energy at specific frequencies, or in a range of frequencies (depending on how the slats are tuned). In general, it's better to have either a simple reflective panel there, or absorption. The rest looks OK. but I wouldn't do those three side panels on each side until after you get the basic treatment in place. That make make the room too dead. I would put the initial treatment in, then test the room again to see how it is doing, and decide on what to do next. The window up front is fine, by the way. No problem with that. - Stuart -

Stuart, thanks for your in-depth reply. I truly look forward to your replies.

There are also some issues with the way you did the tests

I will adjust my settings accordingly for the next round of testing.

First, the modal response is really obvious, and quite scary, so I'm guessing the room was absolutely empty when you did those tests, right?

Yes, absolutely empty, the worst case scenario.

Got any photo's of the room as it is now?

Check the picture below of how the room looked during the initial test.

Also, please post the final inner dimensions of the room.

The room was originally 160" wide, 189" long, and 98" high on average. I say on average because the ceiling is higher in the center by 10". Also, the raised ceiling panel is asymmetric in the room and unavoidably so. Perhaps this accounts for some of the differences between the left and right measurements. There has been an additional sheet of 5/8 drywall added on all wall and ceiling surfaces, and an additional 3/4" subfloor with the 3/8" laminate flooring. This brings my "final" dimensions to 158 3/4" W, 187 3/4" L and 96 1/4" H.

Are the speakers themselves identical?

I believe so. I just had the crossovers re-capped and they seem to be improved.

There's probably a reason for the lack of symmetry, and you should try to figure it out.

Probably due to the asymmetric ceiling panels and also due to having a table near the center of the right side wall holding the computer and the small LCD monitor.

you seem to be planning to do slot walls on the angled front sections, between the speaker soffits and the side walls

The slot walls aft of the speaker soffits mimic a John Sayers design I have been basing this room upon (picture below). The end of the slat walls is just behind the seated listening position. I have planned to have these be the primary mode busters in the room, as the spacing between the slats comprises about 17% of the total panel area. Would it be better to increase this percentage to say 35%, in order to make the slat walls act as broadband absorbers rather than tuned ones?

I wouldn't do those three side panels on each side until after you get the basic treatment in place. That make make the room too dead.

Those three panels are there to eliminate flutter echoes between the otherwise parallel side walls behind the listing position. I am planning to put plastic film behind the burlap outer covers on at least half of them (if not all of them) to retain some of the highs in the room. Is this not a suitable solution to the expected flutter between those two walls? Also, as I am continuing with the construction, at what point(s) should I run additional measurements? Thanks very much for your input on all of this madness. -Jack (still crazy in Central Texas after all these years)

Anyone?