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PostPosted: Sat Apr 03, 2021 2:45 am 
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Joined: Fri Apr 02, 2021 11:16 am
Posts: 6
Location: Providence, RI
Overview

I’m building a basement studio in my 140 year old Victorian home. This studio is for personal enjoyment and I don’t have many aspirations about clients or making money. I play mostly rock and electronic music. My partner is also a musician and is understanding of noise. My neighbors are far enough away, and the walls thick enough that I can currently play drums in the room that will be the control room at 11pm and no one minds at all. The room used to have wood panel walls and a tile drop ceiling which have been removed.

Any and all critique is welcome. I'm planning on doing most of the work myself.

Goal

The goal is to make a room that can reproduce audio playback accurately for the purpose of songwriting, sound design, recording, and mixing. While some measures to mitigate sound transmission will happen (double doors, additional window glass panes), there is no goal of making this room “soundproof”. If it is possible to EQ a guitar amp or snare drum from the next room, then it is more than sufficient. I monitor at relatively typical levels, no louder than around 85dB on average.

Little consideration need be made in this plan for the live room at the moment. That is a separate project.

Room Measurements
At longest dimensions:

Length: 223”
Width: 167”
Height: 100”

Existing Construction Description

The outer walls are a mixture of fieldstone, brick and thick granite slabs. The inner walls are 4 inch thick brick, with a chimney section that offers 24 inches depth, and another 4 inches of brick on the other side. There is no vapor barrier on the wall as a modern home might have, and after stripping old fiberglass insulation some light can be seen around the windows frames.

The floor is concrete, and I suspect it also has a layer of brick below that from some ghosting in the shape of bricks I can see in a few places in the basement.

There is fortunately no history of water ingress. The drainage is well graded outside, and the home sits near the top of a hill. There are wool rugs on the floor down there that are undamaged by moisture.

The ceiling is lathe and plaster. In many sections the plaster is not in great condition. Above the lathe are the joists supporting the room above, and it is approximately 8 inches to the hardwood sub-flooring that then has more decorative facing flooring on top. The room above is a living room that is rarely walked though, and has a baby grand piano. Microphone lines run into this room for recording the piano.

The room is 100 inches tall. Its length runs a maximum of 223” (19’ 5”), and widest is 167” (13’ 9”). The width and length are slightly irregular due to three reasons:

The fieldstone wall comes is about 2” further in for the first 50” of height
The brick inner wall contains the foundation to a chimney, which comes into the room by a foot for 63” of the wall.
The far end wall is three segments, with two of them being at approximately 45-degrees.

The room contains one door, and three small windows that are approximately 19” tall, 32” wide each. There is currently a closet at the rear as well which will likely be removed.

Some actively used iron radiator heating and sewage pipes do go through the room close to the ceiling near the sides but are rarely the cause for noise. There currently is a radon mitigation system in place, but it is far too noisy and is being moved to another room where it can be better insulated and will not cause noise.

With the radon system off, average sound levels during the day are around 36dB-C weighted.

Potential Plan

Leave existing framing in place where possible. Spray exterior walls with 2” closed-cell insulation foam (R-value 14 total) for both insulation and vapor barrier.

Cover floors with DMX Air Gap underlayment to allow for air and moisture flow. Tape to seal with blue tuck tape to create vapor barrier. Cover with 23/32” tongue and groove OSB subfloor. Drill and secure to concrete floor with Tapcon screws. Final floor will be a waterproof vinyl plank flooring that resembles wood such as Lifeproof from Home Depot or similar.

Frame side and rear walls on top of the OSB, approximately 6-12” out from masonry walls with either 2x4 or 2x6. If 2x6, space 24”. These are not load-bearing walls! They will hold electrical wiring and outlets, and acoustic treatment.

Front wall will not be built on top of the OSB. Instead they will be built to hold the speaker in a flush/soffit mounting configuration. This will be done to practically eliminate SBIR, and reduce the need for speakers and listener position to be pushed so deeply into the room. Specific speakers have not been determined yet. Materials used will be heavy such as brick, concrete, cinder block, or heavy layered woods to prevent vibration and coupling.

Building another ceiling slightly below the existing one, suspended from the other inner frame. Inside this, more rock wool. Unclear how to create a flush and durable surface that will not sag and will have good acoustic properties. Another outstanding question is if it should be slightly lower in the front, and higher toward the back. With a 100” maximum height there isn’t much space to play with, but potentially having it 90” in the front, going up to 97” in the rear may be useful? Other options include a drop ceiling suspended from the existing ceiling, with acoustic tiles such as those from GIK acoustics. Additionally repairing the existing lathe and plaster ceiling, and putting in closed-cell insulation or rock wool between the floor joists is also an option.

Window usage will be maintained, and a second layer of thicker glass will be installed to provide additional loss of sound transmission.

Double doors will be hung, potentially filling otherwise hollow doors with sand. Weatherstripping will be added. Heavy duty hinges and hardware. An automatic lift door bottom will complete the seal.

One 15A GFCI/CAFCI breaker circuit will be used per outlet, reducing potential for ground loops and additional noise. 12 gauge romex copper wire will be used along with metal outlet boxes and high quality 15A industrial or better outlets.

HVAC will be provided by a ductless mini split, professionally installed. That doesn’t exchange fresh air, but 99% of the time the doors will be left open.

A mixing console will eventually sit at the front of the room, likely an MCI JH-500 series. Some small speakers like NS-10s or Auratones will sit near the meter bridge as alternate speakers to check with.

Potential listening position is approximately 100 inches from the monitors, with speakers at 30 degrees to either side with approximately at 15-degree downward tilt.

Acoustic Treatment Ideas

Walls will generally be filled with rock wool, and have fire-retardant fabric stretched across as covering. Some sort of hard board with holes may be used near the bottom 24” to prevent tearing and damage from cats. No drywall usage is planned.

Given the amount of rock wool present in the covered walls, a large focus on broadband diffusion seems needed, and no additional absorption. Considerations include QRD / Skyline diffusers on a large portion of the walls.

Rear corners will have deep 45-degree bass traps.

Best treatment of the ceiling is unclear. Help!

Initial tests in REW show a large bump around 90hz, which aligns with the 3-0-0 and 0-2-0 modes having close overlap. Another likely pair exists at 135/137 and 177/179, given the room size and modes but I haven’t been able to re-test the room in REW properly yet to confirm.

Primary Questions

  • Soffit mounting. Is this room too small for it? What speakers under $5k should I be considering for this project? I cannot afford ATC110 or similar.
    There’s existing framing which is (almost certainly, will check with a structural engineer) non load bearing on ¾ of the walls. Can I leave this in place, or is there strong benefit from removing it?
  • Is my floor layering solution ok?
  • Will filling walls with rock wool dampen it too much? Hoping for them to act as giant bass traps all around, and I assume it’s best to put QRD/skyline diffusers covering a good portion of the rear/side walls?
  • What should I cover my walls with? If they are full of rock wool, and I just cloth cover them, will that make the room far too dead?
  • How do I build a wall in the front that holds the speakers and angles downward? Lots to read on this. I'm assuming to use heavy materials like brick, concrete, etc
  • What’s the best approach to a ceiling? Another drop-ceiling? Frame it on the walls and angle it? How to treat the surface and hold up that treatment?
  • How do inner framing and treatments impact room mode measurements? Are the modes, especially in the sub 200hz frequencies, really only impacted by the masonry walls, as they otherwise go through/around anything smaller?


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PostPosted: Sat Apr 03, 2021 6:07 am 
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Joined: Tue Mar 25, 2008 3:31 am
Posts: 523
Location: Cork Ireland
Soffit mounting. Is this room too small for it? What speakers under $5k should I be considering for this project? I cannot afford ATC110 or similar.

Soffit mounting is common in OB trucks....
Neumann KH310

There’s existing framing which is (almost certainly, will check with a structural engineer) non load bearing on ¾ of the walls. Can I leave this in place, or is there strong benefit from removing it?

I can't think of an acoustic benefit to removing it. Leave it unless it hampers whatever you are installing.

Is my floor layering solution ok?

Not my area, codes, damp, etc. Acoustically the safest floor is concrete on grade which will prevent any booming. This could be painted or wood glued to it for maximum solidity.

Will filling walls with rock wool dampen it too much? Hoping for them to act as giant bass traps all around, and I assume it’s best to put QRD/skyline diffusers covering a good portion of the rear/side walls?
What should I cover my walls with? If they are full of rock wool, and I just cloth cover them, will that make the room far too dead?

You won't trap bass unless you have quite a depth. Boggy, sadly RIP frequently used 2 feet of fibre on all walls. He and many others face this deep treatment with wooden laths.
You can see Boggy's work in progress pics on Facebook and Instagram. For more inspiration take a look at John's gallery here and Bunker Studios designed by Rod Gervais.

How do I build a wall in the front that holds the speakers and angles downward? Lots to read on this. I'm assuming to use heavy materials like brick, concrete, etc

I doubt if an angle is particularly useful.

What’s the best approach to a ceiling? Another drop-ceiling? Frame it on the walls and angle it? How to treat the surface and hold up that treatment?

Best value would be a drop ceiling using fully absorbent tiles. Autex and others do very nice looking Polyester ones. I would fill the void above the tile with light fibre.

How do inner framing and treatments impact room mode measurements? Are the modes, especially in the sub 200hz frequencies, really only impacted by the masonry walls, as they otherwise go through/around anything smaller?

Referring again to Boggy. He was asked about Modes in his studios. He replied 'what modes'

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DanDan FitzGerald MIOA MAES
http://www.irishacoustics.com
http://www.soundsound.ie


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PostPosted: Sun Apr 04, 2021 2:10 am 
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Joined: Wed Jul 13, 2005 3:55 am
Posts: 5024
Location: Old Tappan, NJ USA
agree with DanDan on those points.

re-do the radon venting to make it quiet and keep it on. as well as general ventilation - continuous operation while occupied.

you should probably think through the baffle mounting assembly as the one you show in your drawing is not a good one with a corner like that. definitely make the overall structure "flatter" across the space and use the internals for trapping. close off that window for isolation, or plan on building an isolated "duct" for allowing light in and keeping your sound in as well.

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Glenn


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