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Taming Home Studio Acoustics
August 2007
A recent move to a new house also meant a new home recording studio – ooh boy! However there were no easy solutions like a shed right down the end of the garden and it was decided that the studio would have to go in the garage joined to the house. This article covers two aspects of the acoustics – first isolating the studio from the rest of the house and secondly getting the sound right inside the room.
Isolating The Studio
The new house is around 12 years old – two storey brick with concrete floors and aluminum joinery. The garage is joined to the house by a common side wall and also via the garage ceiling. It was advertised as a 4 car garage but you can imagine how useful a two wide two deep garage is so we decided to convert the back to a 5m x 3m studio.
The first challenge was to build the studio so that we could play and record reasonably loud music without disturbing the rest of the family. After researching the internet and discussing the project with the builder it was clear that there was no easy or quick solution. The only effective sound isolation is mass and mass is thick and heavy. We needed to line the room with as much mass as possible at a reasonable price and without compromising the space. We decided to build a new “quiet” wall and door to separate the studio from the rest of the garage, three new false walls inside the existing ones and a new false ceiling. Essentially we would build a quiet room inside the existing room. We chose an off-the-shelf solution from Winstone Wallboards Ltd, New Zealand’s largest manufacturer of “Gib” gypsum plasterboard and drywall systems – www.gib.co.nz.
Specifically we selected their Resilient Mount systems for the walls and ceiling. The walls comprise metal wall studs, two 10mm sheets of Gib Noiseline plasterboard on the inside of the walls and 1 layer of Gib Noiseline board on the outside. The double layer of Gib board is screwed to resilient metal mounting strips on the walls and with resilient rubber grommets to the ceiling. The wall cavities are filled with acoustic glass wool (“Silencer Batts” which are essentially compressed standard “Batts” with more sound absorption).
Wall Construction showing the two layers of 10mm plasterboard on the inside of the room attached via screws to the resilient metal rails.
Celing construction showing the two layers of 10mm plasterboard on the inside of the room attached via rubber grommets.
In this system the primary isolation is provided by the double layer of dense plasterboard on the inside of the room. The secondary isolation is provided by the resilient metal wall fixing strips and rubber ceiling mounts which significantly lower sound transmission. The rest of the effect is provided by the absorbent cavity filling, sound sealant used around the edges of all sheets of plasterboard and the single sheet of plasterboard on the outside of the wall.
We then installed a solid wood door with rubber airtight seals in the new wall between studio and garage and The concrete floor was covered with thick underlay and carpet.
Currently the only untreated areas of the Studio are two large windows and an aluminum glass door to the back garden. Double glazed acoustic glass panels have been ordered for these three areas.
So did it work? Did it what! Talking and moderate volume music cannot be heard at all in the house. What about loud volume music? This can only be heard a little in the bedroom right above the studio but not in the rest of the house. Yes but what about a live drummer or bassist at work? I have not tried this yet but suspect recording live drummers and bassists will have to be scheduled when no-one is in the house. Let’s face it – low notes on a bass can produce waves with a 7 metre cycle so nothing affordable will completely stop those giants traveling through your walls. My studio usage is primarily recording vocals, guitars, brass and keyboards plus mixing so I am absolutely thrilled at the outcome – mind you not nearly as thrilled as the rest of the family and neighbors.
Having now experienced this first hand I cannot understand why all new houses are not built with similar quiet walls and ceilings at least in sound critical rooms.
Getting the Sound Right
We placed a table at the end of the finished studio, setup the sound system and turned up the volume on one of my current mixes. Frankly the sound quality was awful. The lows were unclear and the mids were very boomy. There was virtually no stereo field and certainly no impression of depth at all. Worse still there was an area right in the middle of the room, just where you want to stand when doing a mix, where the bass almost completely disappeared. In the back corners of the room was a massive build up of very nasty standing waves at around 130 Hz.
Shit! – what was a boy to do? I went back to the websites and spent a long time examining one in particular – Ethan Winers’ excellent site re studio acoustics www.ethanwiner.com. He has some very good advice on how to make your own bass traps. This looked just what I needed but the problem was that you need quite a few of these, they are very bulky and my studio is small. I saw another site about building bass traps out of tubes of compressed glass wool pipe lagging. I bought 4 of the largest Forman Insulation had in stock – 1 metre long and 300 mm in diameter. I sealed the ends with custom board and stacked them two high in the back corners of the room. They looked like Greek pillars and did absolutely nothing at all for the sound in the room. I haven’t told Ethan about this cock-up yet because he would tell me it serves me right for not following his advice. I’ll just quietly slip them into the trailer on my next visit to the dump.
Plan B – leave the room sound treatment until I have all the furniture, book cases, equipment and cable rack in place. In retrospect I should have done this on day one instead of going into a blind panic when I heard the empty room sound. I then cut down some ready made blinds from Bunnings and installed those over the two windows and set them at three quarter closed.
So how did the room sound? Better but not what I wanted. Back to the web sites – where most of the advice involved simply popping down to your local studio acoustics store and purchasing a few Auralex panels and sticking them on the walls until you got the right effect.
Well you can’t buy these ready made acoustic panels in new Zealand – you have to have them manufactured to order with a minimum quantity of four 1200mm x 1200mm panels @ NZ $165 plus GST per panel. It wasn’t just the cost it was the principal and the good ol’ Kiwi do it yourself mentality! Plus how did I know how many panels to order and whether they would even work or maybe they would completely deaden the sound altogether which I didn’t want either. I wanted something reasonably priced that came in sheets or ready made panels that I could “play with” until I got the right effect.
Back down to the Forman Insulation warehouse where the chaps were keen but not very experienced in taming home studio acoustics. So I asked if I could just hunt around their warehouse for a while until I found something. I finally came across a product called Novahush manufactured in New Zealand and used primarily for lining air conditioning ducts. It is made from white polyester threads woven and sealed together by heat into a mat. No glues to break down and no bloody glass wool fibres to make you itch. It is 20mm thick, comes in 2400mm by 1200mm sheets and a rather attractive (if you like black) Hessian style black fabric bonding on one side. I bought three sheets at a moderate price, got them home and started cutting them into smaller panels with scissors and placing them strategically around the room and on the ceiling. I wanted a pretty dead end for mixing and a slightly more live other end of the room for recording so I stacked the panels primarily in the mixing end. This product is very light so I glued the ceiling panels with contact adhesive. The panels around the mixing position are simply resting on the desk with the top edge fastened to the walls with Velcro dots. The side wall panels are hung like pictures using an aluminium moulding glued to the back of the panels with contact adhesive. Each of the vertical panels is placed at a slight angle to cut down on sound reflections. Then I played the same mix.
What a difference! At first the most noticeable improvement was more bass. Wait a minute – don’t you mean less bass! No more bass, more bass articulation and an almost even response throughout the room. I like to stand up and walk around the room often while mixing to get a different perspective and this was just perfect. The other benefits were a significantly enhanced stereo field and even better still an impression of depth which made it much easier to judge how much reverb to add or subtract to each part of the song. What I was now hearing was primarily the near field monitors (Alesis Monitor Ones) and not the room. I really like these monitors which I’ve had for about 12 years but I’ve always been slightly worried about their rear bass port and in my previous home studio I had to go out of the room to try and work out how much bass was in the mix i.e. I was just guessing.
The net result is that it now takes around 1 and 2 hours to mix a song where I used to be still slaving away at 2.00 in the morning and then stumped off to bed tired and discouraged.
Summary
Is it the perfect Home studio? Definitely not but I can record and mix any time I want without annoying the rest of the family and neighbors and the sound is such a dramatic improvement over the last studio - I’m over the moon.
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