Mastering/Mix Room w/Vocal Booth

After being in a temporary Mastering space for 3 years we figured it was time to build a new room. My partner and I have been operating a dedicated mastering room for about 9 years. We decided to build the new room on the 2nd floor of my partners new house (he had left a space for it when he built the house). The space was about 15 ft wide by 14 ft wide. As my partner is a full time artist, he wanted to incorporate a vocal booth if at all possible. We knew that it would be tight and tried to come up with some plans. But we soon decided to enlist the help of John Sayers so I sent him this sketchup drawing before our first phone call: As you can see, the room has short side walls and a low ceiling at 7.5 ft. We knew it was going to be tough and expected John to tell us it was impossible. We talked to John over Skype...John in Australia, myself in North Carolina, and my partner on his tour bus traveling to singing date. Technology is so cool! Anyway, during our first phone call John presented us with 3 options for the room...1 for just a mastering room, 1 with a vocal booth & stand mounted speakers, and 1 with a vocal booth & soffit mounted speakers. After talking with John about many aspects of the design we chose to go with the soffit mounted speakers and vocal booth. Here is his design: We modified things a little here and there but stayed pretty true to his design. He is amazing with Sketchup! I sent him my sketchup model about 20 minutes before our call and he had 3 options for us when the call started! I know it looks tight, and it is. But it is perfect for us and what we do. We never plan on recording bands. The main function of the room needed to be mastering. Mixing and the vocal booth were secondary in priority. We had another 1 hour followup call a few weeks later to finalize some details on the acoustical treatments of the room, soffit design, etc. Then we began the construction. Pictures are coming soon! Scott Whitehead

John suggested that we remove the drywall on the ceiling at 7.5 ft and investigate turning the whole room into a cathedral ceiling. We had our carpenter look at the existing rafter ties and how the room was constructed. After careful consideration he decided it was safe to remove the rafter ties so we could sheetrock all the way to the peak. Here is an image of us just getting started. You can see our carpenter and my partners son working on some framing. And here is view looking back toward the main door. That is me holding the air duct back and my shy little girl beside me! We have finished the insulation and sheetrock all the way to the peak and re-installed rafter ties at 8 ft. Cloth will be attached to these rafter ties so in essence we will have a 9 foot peak in the vocal booth and mastering room:

Our next job was tackling the framing. This was tough but our carpenter did a great job. Everything was on an angle! Here is the front wall. We still have to frame up 2 walls to make a center cavity, separating each speaker cavity. The speaker holes are over sized to facilitate larger speakers later (our current set is Event 20/20 BAS with 12" Event powered subwoofer). We chose to go with John's vented soffit design. Here is the back wall which will be covered in cloth and filled with bass hangers. Here is the side wall where the window is located. This will be a slat resonator wall. The wall where the glass slider is going to be will also be a slat resonator but with a more shallow cavity.

Hi Scott - great to see you here. Your studio is an interesting addition to the site as the attic studio is a breed of it's own :) cheers john

John, We are almost complete! We have to finish the timber on the front wall and install some trimwork. We have someone building a custom desk for our equipment. After that is complete we can move in. I will upload other pictures of our progress over the past couple months as soon as I can. Thanks for all your help! Scott

Wanted to add some updates. We are actually finished with the construction of the room. But I don't want to put the finished pictures up yet. I thought it would be better to show the process. Here is the left wall with the glass slider and vocal booth. We actually made a mistake by sheetrocking the control room side of the wall and had to tear the sheetrock off. It needed to be a slot resonator like the wall on the right side. We also had to replace the glass in the slider with 3/8" solid glass. The thin insulated glass had a terrible pinging sound when you sang in the vocal booth. The sheets were very heavy and the door now weighs a ton! Here is 1 of the 2 bass traps in the vocal booth. They will be filled with bass hangers and covered in cloth. Rockwool Time!! :D Here we are in our hazmat suits cutting the rockwool for the bass hangers. An electric knife cuts it very well. The construction is a fiberboard core, with rockwool on both sides. The rockwool is held onto the core with ductape. This was not a fun job. We had a miserable couple of days working with this stuff! :)

We caulked every joint, seam, etc in the room. Here is my partner caulking in the bottom of the speaker platforms. Now its time to install all of those bass hangers. Once we got them all built outside it did not look like they would fit into the room, let alone into the wall cavities behind cloth. I don't remember an exact number but it was at least 30 - 40 of them.

Here is the rockwool in the slot resonators And we put insulation in between the joist hangers in the ceiling of the control room and vocal booth.

Here are the boxes we built to hold the speakers rigid. They are a very tight fit. The bottom part of the box is filled with concrete and everything is glued and screwed. There are vents up the back with about a 3" airspace for air to flow up from the bottom of the cavity and take the heat from the amps out a slot in the top of the front wall. Here are the vent holes in the top of the box Here is the custom vent tunnel to direct the heat to the front wall. You can see we have begun filling the cavity around the speaker box with rockwool and insulation cutoffs. We filled it all the way to the top and around the vent tunnel. Here is a testfit of the Event 20/20 BAS before we started filling up the cavities. We covered the backwall with plastic before covering it with cloth We have started covering the walls in blue cloth. This is the right slot resonator wall. To the left you can see the speaker cavity is completely filled and above you can see that the angled ceiling areas have been painted.

Slats on right slot resonator and cloth on back wall (taken with cellphone). Putting bamboo on the front wall that matches the bamboo flooring in the room (taken with cellphone. sorry for the bad quality) Removable cloth panels on bottom of front wall (cellphone again)

My father-in-law and I built a custom desk for the mastering room. This is during construction and does not show the 2 angled racks that were added to the top. We modeled it after an argosy but because our room dimensions were so small there was no way we could fit a real argosy in there. So we shaved as much off of the dimensions as we possibly could. These pictures do not do the desk justice. It is extremely sturdy (you can hop up on the front center of the desk and set with absolutely no sag in the desk. We had a guy finish the exposed rounded edges to match the bamboo flooring in the room. Its truly a 1 of a kind desk. There will be better pics of the desk later when it is finished. There were taken with a cellphone so please pardon the bad quality.

We finally finished the cosmetics of the room and were able to move in! :yahoo: Its almost impossible to believe we fit a mastering room AND a vocal booth into a space 14 foot x 15 foot. But it fits very nicely and there is plenty of room. When we first saw the design, it looked like all our room space was being ate up with bass traps! But those areas had very low headroom and would not have been unusable anyway. And without all the traps, an area this small would have never worked. We are very happy with the room and very excited to begin working in there. We had our first mastering session this evening and it went great. During the months of construction we never hooked the speakers up and "tested" the design. We just trusted that John's design and suggestions would work. And I have to say, the room sounds great! :D THANKS JOHN! Very even response when you move around the room...nice tight low end and crisp top end. And it looks great too! Here are a few quick pics. We still have some things to finish (blank plates in the left rack, tidy up cables, etc) and then we will have some professional shots taken. You can see the Event Powered Sub setting behind the desk in this image. *NOTE: The area with the pool table is not part of the mastering room/vocal booth. It is part of the residence where we built the room. But we did run mic lines and headphone runs into that room in case we ever need to use it. :wink:

My congratulations to you both - looks fantastic. :thu: Love the use of mdf.

Wow, that's great. Nice report. Have any details on the Argosy replica ;) ?

Thanks John & Ro! The argosy replica was kind of a "build it as you go" project. I had put together 2 argosy's before so I knew how they were constructed. The width was calculated by the width of 2 racks plus about 22" for the monitor in the middle. Height was based off of the argosy. Depth was a little more tricky. I basically took a side view scale drawing of an argosy and started moving lines around till I got something that would allow 13 rack spaces, provide room for a mouse on the flat area, allow a small armrest, and give plenty of knee room under the desk. The desk ended up being a little over 5 feet wide and 36" deep. We bought (2) 4' x 8' sheets of 3/4" MDF that were veneered with black laminate. We did not use the European "knock-down" fasteners like argosy. We glued and screwed most connections. That is why you can sit down on the arm rest in the middle of the desk with your feet off the floor and there is no sag. Legs are welded steel like argosy. We had to remove the racks from the top to get it up the stairs. Took 4 guys and it barely fit up the stairwell. All edges were rounded over with a router and finished to match the bamboo by a local furniture finisher. It took about 1 1/2 weeks to build. Then we had to wait a couple more weeks to have the edges finished. It was definitely worth it. No one makes a desk small enough for our room so we really didn't have a choice. And we came out quite a bit cheaper than buying a similar argosy. Scott

Hello. My first post here!.... the room looks great. Very tasteful. I have a question regarding the slat resonators. Did you use a formula to decide the width of your slats and the width of the gaps? I am sort of confused to how that works with the Helmholz calculator. This is really more of a general question about the Helmholz I guess (but was curious about your decision), but in thinking about the helmholz effect and how it is compared to a soda bottle and blowing over the top of it to hear a tone... if the bottle had other holes in it (or multiple openings at the top let's say) wouldn't that affect the sound? And if there were different sized openings on the bottle .... etc. The calculator says to just plug in a slat and gap width and it will tell you the freq that it is effective at absorbing. But when you have different slat and width gaps, won't they all affect each other? The calculator doesn't take the other slat and gap widths into consideration, or how many there are for that matter. I guess I've always thought a Helmholz resonator worked with a cavity and a single slot/opening. Either way the slat resonator makes sense as an effective diffusor/absorber but I'm just wondering how useful it is to try and calculate the slat and gap widths. I'm getting ready to design a new control room and I feel myself pulling in the direction of just trying to make the slats somewhat random and aesthetically appealing. As long as the cavity is packed with absorption it will achieve the low freq absorption and with the slats reflect (and somewhat diffuse) the high freqs.

Been covered a lot please read the forum

if the bottle had other holes in it (or multiple openings at the top let's say) wouldn't that affect the sound?

That's not really the acoustic equivalent of a slot resonator. It would be more like lining up several bottles of different sizes next to each other, and blowing across all of them. each will resonate at its own frequency.

But when you have different slat and width gaps, won't they all affect each other?

Not really. It is the volume of space directly behind the slot that acts as the resonator. Don't forget that air is very stiff, as far as sound is concerned: At a speed of 340 m/s, air is very solid. Ever drive at 100 km/h, and stick your hand out the car window? Imagine doing that at ten times the speed, and you get an idea of how solid air "feels" to a sound wave. So it only really "sees" the zone directly behind the slot itself, not the other zones above and below. It would be kind of like if you cut holes in the sides of adjacent bottles, and linked them together. It wouldn't change things much. In reality, a helmholtz resonator is a "mass/spring" resonator. The air in the gap between the slats acts as the mass, and the air in the cavity behind it acts as the spring. The CORRECT equation for calculating the resonant frequency is: F = 2160 * sqrt (r / ((d*1.2*D) * (r+w)) ) Where: r = slot width d = slat thickness 1.2 = mouth correction D = cavity depth, w = slat width 2160 = c/(2*PI) but rounded c = speed of sound in inch/sec. Notice that the only dimension regarding the cavity, is the depth of the cavity. It doesn't really matter how long the cavity (slot) is, and the effective volume is limited by the slot width plus the slat width. Since you normally use slats that are the same width for all of the slots, the only cavity dimension that changes the resonant frequency is the cavity depth: If you angle the slat away from the wall behind it, such that the depth changes along the slot (deeper cavity at one end of the slot, shallower at the other), then you make a broadband resonator. In effect, you can think of it as a series of several separate resonators, each with its own depth, as if you had actually made your slat into a kind of "sideways staircase", except on an infinite scale. So each tiny section of the resonator has it's own individual sharp frequency, governed only by the cavity depth immediately behind it, but when you consider all of the "steps" together, then you get a broadband resonant curve with a flat top, instead of a bell shape. I'm not sure if I'm explaining this very well! But basically it is only the depth that governs the frequency at any give point on a slot resonator, since all of the other factors are fixed, and each portion of the sound wave only "sees" the slot and cavity right in front of it. It can't see, and is not affected by, adjacent "steps" on the resonator.

The calculator doesn't take the other slat and gap widths into consideration,

It does not need to. Each one acts on its own.

or how many there are for that matter.

Once again, It does not need to. Each slot acts on its own, independent of the others, since that portion of the sound wave that gets through the slot, only "sees" that specific width/depth of slot, and only that specific depth of cavity. You are looking at the slot wall as an entire forest. You need to get closer, and see it as a large set of individual trees, each of which has its own characteristics. Al together they make up the forest, but each tree acts alone.

I guess I've always thought a Helmholz resonator worked with a cavity and a single slot/opening.

That's correct. But there is nothing to prevent you from putting a whole bunch of them next to each other! And you can tune them all to the same frequency if you want, or all to different frequencies, since each acts independently of the others.

I'm just wondering how useful it is to try and calculate the slat and gap widths.

Very useful! But John already did that for you with his design for a slot wall. If you stick to those dimensions, you will have a good broadband absorber that covers a wide range. If you angle it slightly, you get an even broader bandwidth, but at the expense of efficiency. You cover more frequencies, but get a lower amount of absorption for each individual frequency.

just trying to make the slats somewhat random and aesthetically appealing.

Probably not a good idea! You might end up duplicating or triplicating your coverage of certain ranges, and totally missing others.... Far better to just go with John's standard slot wall, since he has already done all the math for you, and oodles of those walls have already been built, very successfully. You might get luck with a random arrangement.. but then again, you might not. And your chances or randomly hitting on a BETTER design than John's, are about the same as your chances of winning all fifty State lotteries on the same day, then getting struck by lightning, shot, drowned and suffocated all at once, by accident! :) - Stuart -

Hey Stuart... thank you for the response. The analogy of the forest of trees helps a bundle. Apologies if a post such as mine has already been covered... I thought I had scanned good and hard for some answers, but it is probably my stubbornness to accept certain bits of science now and then. I think what confuses me is that there is an importance placed on the box to be sealed airtight. I picture all of the additional slats as air leaks in the sealed box and it kind of messes with my head. And I will take into consideration the math for my slot gaps and widths. It makes more sense to at least try the math. I think any combination of widths, calculated or not, will look nice. cheers wil

i saw the photos it is amazing

euphioq, In response to your question on whether we calculated the slat resonator, we did not. I talked with John about board and gap widths and we just made them random within those ranges. Scott

severecritic, Thanks! We really like the room. Scott

What about the costs? How much were your costs for the whole constrution? Greez

Soundman2020 wrote:

The CORRECT equation for calculating the resonant frequency is: F = 2160 * sqrt (r / ((d*1.2*D) * (r+w)) ) Where: r = slot width d = slat thickness 1.2 = mouth correction D = cavity depth, w = slat width 2160 = c/(2*PI) but rounded c = speed of sound in inch/sec. Notice that the only dimension regarding the cavity, is the depth of the cavity. It doesn't really matter how long the cavity (slot) is, and the effective volume is limited by the slot width plus the slat width. Since you normally use slats that are the same width for all of the slots, the only cavity dimension that changes the resonant frequency is the cavity depth: If you angle the slat away from the wall behind it, such that the depth changes along the slot (deeper cavity at one end of the slot, shallower at the other), then you make a broadband resonator. In effect, you can think of it as a series of several separate resonators, each with its own depth, as if you had actually made your slat into a kind of "sideways staircase", except on an infinite scale. So each tiny section of the resonator has it's own individual sharp frequency, governed only by the cavity depth immediately behind it, but when you consider all of the "steps" together, then you get a broadband resonant curve with a flat top, instead of a bell shape. - Stuart -

So basically on an angled slat resonator, given the slot and slot width is the same, the largest cavity (left side in this case) will be the start frequency and the smallest cavity the end frequency, while covering all frequencies between those start and end frequency? Is there a link to John's standard slat resonator? Can't seem to find it.

Really sharp looking space. It is pretty incredible that you could squeeze so much into such a limited space. Very impressive.