Step Five: Isolation and Mode Analysis

So it’s been a while 🙂 now we are going to look at our room from the perspective of increasing the isolation and doing the initial mode analysis of our room.

From an isolation perspective we can do several things: one – increase the mass of the room boundaries – walls, floors, ceiling and windows and doors; two – seal everything really well – doors, windows, electrical and other boundary penetrations; and three – decouple noise and sound creating elements from the surrounding boundaries to reduce the amount of transfer directly through the structure. And in our example room we really cannot do much else if we’re renting (for example and very commonly asked about) or even if we own it, it might not be within our budget.

Adding mass to the walls and ceiling is pretty straightforward – we add some more drywall layers. if we choose this, we probably need to strip out the trim and outlets etc so we can add the drywall, and maybe it’s just a single 5/8″ (16mm) layer, and replace the outlets, switches, fixtures, trim etc. if we have access under the floor because it’s joist and subflooring – we can add layers of drywall between the joists (sometimes we line this with “blueboard” foam insulation to even it out because of nails) and seal it all up.

Remember – check with a properly licensed structural engineer before adding this extra weight to your building and of course obtain any necessary building permits and inspections needed to correctly complete this work, maintain your certificate of occupancy and your insurance coverage.

Increasing the mass on the windows and doors can take several forms but in our example we simply create a window plug to cover the window (like heavy indoor shutters) and seal up the doors. we could add a layer of MDF to the doors to increase their mass, and if they are hollow doors, replace them with solid core doors first. Increasing the weight of the doors means we need to also look at the structure around the door to make sure it is sturdy enough and also we may need to replace the hinges as well. we can make our own stops and seals or buy them from companies like Zero International.

E.g. Increasing our room isolation

Once we finish sealing everything, adding mass where we can, then we need to consider the air flow – in our example room we only have supply vent and no return as it’s a common return for the house. in this case assuming we need some isolation on the ducting, we can build an in-room plenum to isolate the supply from the rest of the house, perhaps big enough to slow the air speed down, and advantageously direct the air flow in the room. for the return, we could build an in room or in hallway plenum which vents into the common space so the return operates as expected. this return plenum could include a fan to ensure positive air flow out to the common area or it could be passive.

With isolation design out of the way (and please don’t consider this a trivial step – good isolation like anything else can be difficult to achieve when you have limited options and budget) the next step is to consider what we need to do about acoustic treatment design. the purpose of the design effort here is really to identify your main options for the acoustic treatments and get them incorporated into your budget and planning. what you will do is measure the room response after you complete the isolation work so you K NOW what you’re really into. plus the testing will also help identify any remaining defects in the isolation.

From a design perspective, we know that small rooms have a smaller number of modes which have enough space between them to be problematic and the proximity of surfaces causing interference and reflections on our mixing activity which often results in less than ideal translation on other systems. on the other hand we also need to consider the lack of room volume and our need for other considerations in the use of the room – maybe we record acoustic instruments, or someone in the home uses it for painting and bookkeeping. so we want to make some educated guesses as to how the room may respond and also what type of treatments we can add to fit our room requirements and budget.

With the room laid out in SU, it’s easy enough to download my mode template (http://sketchup.google.com/3dwarehouse/details?mid=80c3a2c3b34f8cfc6d2f7f4796305f20) and scale it to fit the floor and two of the walls (long and short wall) and see not only the main axial modes but also first choice positions (like the 38% rule) so our subsequent design work can be checked.

E.g. Gullfo’s SU model template on the floor

With the main modes identified, we can also use several spreadsheet calculators (or Bob Gold’s online mode calculator) to verify our room characteristics such as tangential and oblique modes, first reflection points, etc. it can help to have some of the key equipment specifications handy when calculating reflections, lowest frequency response from your monitors, possible desk reflections, and speaker positioning etc.

E.g. Chris Whealy’s Control Room Calculator

Armed with this information, in the next post we’ll start to layout the room based on our assessment. we will start with standalone treatments which are typically commercial products such as those from GIK Acoustics or Real Traps, or they can be DIY treatments (we’ll start with POA (plain old absorbers) and think through more sophisticated units such as VPR or limp membrane absorbers). A subsequent post we’ll look at the use of integrated treatments and understand how they work together to go even further in shaping your room response.

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Getting Started

you know you want it. but you’re not a designer or acoustician. don’t know how much money you need or can get. and haven’t swung a hammer or cut some lumber. you’re a musician, producer, or just someone who wants a great place to listen to music or watch movies.

without some understanding of the basics of acoustics, video, and construction, you’ll be pretty limited in how much you can achieve without getting some help. and that help is often going to cost you. money, time, aggravation, promises to be kept, and other bartering. even so, getting started in the right way can go a long ways towards having the facility you want. i’ll be skipping the whole site selection bit as thats covered in another blog, but we’ll visit the design steps a bit more.

step one – do you really want to do this? are you really committed? if not, we can stop right here because you’re not going to pull it off so save yourself the frustration and find other means to get into the facility of your dreams – rent, lease, etc.

step two – plan. you must figure out your market, your needs, a proposed budget, skills of the people involved, and how you’re going to get paid or pay back (yes, even personal studios need to provide value). this should be put together into a plan so you can track your progress, and if need be, get investors on-board to help.

step three – if you need help and have limited (low) budget – consider exchange/barter for services, materials, recycled materials, reduction in scale/scope, etc. there are some excellent examples of people putting out advertisements for people to help build a studio in exchange for recording and mix time. one studio in LA, the owner got over 200 responses in a week. his studio was built by a handful of construction professionals (he paid for materials) in about a month.

if you’re looking for investors, work with your designer to get some basic comps, renderings, and ballpark estimates (usually by taking the high level construction per square area costs X your square area = rough approximation – add another 15-25% – and then price retail on your equipment – because you’re likely to be paying installation costs even if you do get discounts on the equipment later, then another 10% of the total – worst case you’re high but its often easier to be high then to have to go and ask for more money later).

step four – be there. show up everyday on site and see whats going on as your facility is built. ask questions, bring coffee or soft drinks (don’t get the crew drunk while they’re working ;-)) show enthusiasm for your project. keep your investors up to date on progress. if this is a commercial facility, start working on your marketing, you want projects lining up in anticipation of your opening. take lots of photos and keep a log of the activities. track costs and time to your plan to see where you guessed right or wrong. plan a party for the construction crew and a party for your clients/friends to celebrate opening day.

step five – get to work! this is the best job in the world! if its your home theater, go relax, you’ve earned it!

Recording Studio Design Guidelines

wow, this is tough because it really comes down to understanding what you are trying to do, your budget, and the location of your new studio. it really is a pain to hear “it all depends” but it does… it’s nice to dream about but in order to make it happen you need to get organized. there are a lot of Internet and book based resources for compiling a set of guidelines for your studio design, but in the end, there are a few key questions to answer to shape your design.

assuming you found the right location, then here’s a few guidelines to consider:

– isolation does make a difference — most people assume they can get by on little or no isolation, and in rare cases that is true, for most of us, getting a good level of isolation is going to keep things more organized in terms of odd sounds entering our recordings, or having disruptions because of neighbors concerned about noise levels. either one is distracting and can throw off those most excellent moments…

– good acoustics is essential — you need it, you want it, yes, really. always start with broadband bass treatments. this way, if somehow those treatments result in enough low, mid, and high frequency control, you’re done. nothing worse than starting with high frequency absorption and finding mud, then trying to correct for the mud, only to find you’ve taken every bit of life out the room. if the low frequency trapping is too much for the mids and highs – add some panels, slats, etc to get some of that life back – your recordings will love you for it.

– visibility is important — people like to communicate with one another directly – not through video and talk backs – try to get as much glass as you can into your walls so people can see it other. if you can make that glass open, then they can talk to each other and hear each others instruments, and generally bring life into your sessions that are just not nearly as fun as face-to-face productions.

– good vibes — no one likes to play in a dungeon (well, not many :-)) so good aesthetics do play a role. if you are running a commercial facility its important to consider flexibility in the aesthetics so they can be adjusted to accommodate the mood of the client and the session in general.

– ease of use — make it easy to get set up, rehearse, record, mix, party (if allowed ;-)) so consider layout carefully, try to design it so people can move large or heavy equipment in and out without risking damage to other equipment or people (do you really want someone carrying that B-3 in its road case over your new SSL console?) if you know you’re going to have long sessions – plan on a lounge with bathroom, kitchen, and some recreation. make sure that lounge is isolated from the recording space to avoid things like loud shrieks from the winners at the pool table from disrupting the 12th vocal take…

so that’s my short list – isolation, acoustics, visibility, aesthetics, and ease of use. there more technical details like electric, security, and so on but from a guideline view these are the main ones to think a lot about.

Home Theater Design

it’s an interesting thing doing this type of design. much of the design tactics you would use in a control room or live room isn’t always applicable to a home theater (HT) design. in addition, the HT needs to have video considerations that are different than video monitoring or windows in recording studio.

one trend i’m seeing is a lot of people recommending “dead” rooms as the best solution for most HT layouts. i have to disagree with that position because a HT needs to have spaciousness as well as the usual timbre/coloration and spectral content controls. a dead room is definitely not spacious… i also see a lot of recommendations for a completely blacked out (and black painted/trimmed) room. yikes!

no doubt the room needs to have the ambient light (as well as reflected light from the presentation itself)  under control, but there are definitely better ways to handle this that is tasteful and less dungeon like. yes, you definitely want black-out drapes to close off windows, but you shouldn’t deprive yourself of natural daylight when the room isn’t in use as a theater, or when you’re cleaning etc.

so folks, there are definitely better ways to make your HT a spectacular place for family and friends to enjoy a “near-theater” experience, without subjecting yourselves to dungeon like rooms that make your ears ring from the deadness.

first off, pick an interior designer to help with color selections if you’re not comfortable with the task of working with dark(er) and flat(er) colors – remember the colors should complement your home as well as be neutral to ensure the colors don’t interfere with your viewing. windows can be treated with hinged “plugs” to block light as well as provide some isolation, or heavy blackout drapes used. the room should have bass trapping installed, low noise air handling, noisy equipment put somewhere it can be isolated, and the bare minimum of absorption to keep the room under control without making it dead.

and of course, contact me for expert help with your home theater project.

Do I need a designer?

Of course you do! but that doesn’t mean the designer isn’t you! without wanting to use “it depends”, sorry, it depends. to be an effective designer of a complex studio construct where isolation, treatment, layout, aesthetics all play important roles, it will take a lot of study and practice to create a proper design. and if physics and acoustics and construction engineering are not your primary skill set, then its an uphill road. on the other hand, if you are simply looking to treat an existing room using DIY or commerically available acoustic treatment products (such as GIK Acoustics, Real Traps, etc), you can probably learn what you need to know in just a few weeks of self-study on the product sites and main acoustic forums.

You might need to learn a bit of math and some terminology but the essentials are learning to accept room modes as the primary problem area for small spaces, and getting the RT60 adjusted for your space. a room mode is simply the result of sound waves being trapped within a set of walls, floor, and ceiling. RT60 is the reverberation time. usually, once you add the treatments for room modes using broad band treatments (broad band meaning wide number of frequencies) you can often find that RT60 and miscellaneous echoes also come under control. in “dry rooms “(low RT60) you might need to add some panels (like plywood or boards) to get some life back into the room. in “wet rooms” (large RT60 or lots of echoes) you will want to add absorption to get all the energy (sound is energy) from bouncing around for too long a time. It depends…

Did that sound alien? possibly. but in a short time you can review product sites for examples of solving common room problems, some reading up on the acoustics forums, you can learn what all this means to you and prepare you to make the decisions needed to shape your space.