The Great Isolation Cabinet Project

Discussion in 'Amps & Cabs' started by smitty_p, Sep 2, 2013.

  1. smitty_p

    smitty_p Well-Known Member

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    And so...it begins.

    This is the first in an ongoing thread where I'll document the construction of an isolation cabinet for my small tube amps.

    To clarify, this is not for a speaker cabinet. I will be putting my whole amp in this. So, it will not be thoroughly sound-proof, as I'll need to provide ventilation. It will, however, greatly attenuate the external sound.

    So, here goes...

    This shot just shows the framing members after I cut them to length:

    [​IMG]

    I decided to join the members using lap joints. To make things go faster and improve consistency, I built this little rig to lap the end of four pieces at a time. You can see I already have the ends done on one side:

    [​IMG]

    Here are the frame members all lapped. You can see how much sawdust this creates. Sorry for the blurry pic.

    [​IMG]

    Here the frame is glued and nail-gunned together. It is sitting on the birch ply that I will use for the sides, top, and bottom. I'm getting ready to trace the floor in this pic.

    [​IMG]

    Finally, this is a shot of the rough-finished floor. The slot is to allow air to enter the cabinet from the bottom. I will be installing casters so the air can get to the slot. I'll put a slot like it in the lid when I get to it.

    [​IMG]

    So, that's all for now.

    Stay tuned!
     
    Jimmy Jacks likes this.
  2. Heket

    Heket Well-Known Member

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    Ooh, an isolation cabinet, useful! I'll stay tuned. I'm interested to know what sort of materials you would use for home-built soundproofing.
     
  3. smitty_p

    smitty_p Well-Known Member

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    Thanks, Heket. I suppose I should also give some specs.

    Unless I make some changes, the size of the cabinet will be as follows:

    Width: 26 inches (660.4 mm)

    Height: 26.75 inches (679.4 mm)

    Length 36 inches (914.4 mm)

    I will have enough room to afford quite a bit of flexibility with microphone placement inside the box.

    The ventilation slot is 16 inches by 2 inches (406.4 mm x 50.8mm). You can see I've already cut the slot for the floor. The lid will have one just like it. The goal is for heated air to escape from the lid and cool air to flow in from the bottom, setting up a cooling convection airflow.

    There will be two layers of sound treatment. First, I'll put a 2 inch layer of Owens Corning 703 fiberglass panels (or equivalent) on the sides, floor, and lid. The OC 703 is a very common acoustic absorption panel used to sound-proof walls of recording studios. Second, I'll put dense, fluted foam panels over the OC 703. Whereas they do provide some sound absorption, the main purpose of the the foam panels is to break up acoustic reflections within the box. The fiberglass panels actually do most of the absorption.

    With all the sound treatment and the density of the 3/4 inch (19mm) birch plywood, itself, I hope to really attenuate the acoustic energy of my amps.

    Of course, as I mentioned, the ventilation slots will allow some sound out, so it will not be sound-proof, per se. But, it should really cut down on the sound quite a bit. I have access to an SPL meter and I'll take readings when I'm done. Besides, in doing research for this project, some guys intentionally make an opening to provide pressure relief in the cabinet. Hopefully, the vent slots will provide this pressure relief and help keep the system from sounding too boxy.
     
  4. frankd

    frankd Well-Known Member

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    Now wre getting somewhere around here LOL,
    Seriously this is cool and something I have thought about
    myself but doubt I ever do Im very interested to see this and how you feel
    it all works out!
    frankd
     
  5. thinkgreen

    thinkgreen Active Member

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    I have heard about these in books, but not seen one or known anyone who has one. And it's the first project of this kind I've seen on forums. So this is very cool and different
     
  6. Sootio

    Sootio Well-Known Member

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    I love the concept. I'm pretty sure Angus has his old Marshall in a box under the stage and that's what you hear in the front of house p.a. when ac/dc plays.
     
  7. smitty_p

    smitty_p Well-Known Member

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    Thanks. I've actually seen a couple isolation cabinet builds on different forums, but they are just for speakers, not entire amps. So, this is a little different. I can't remember the website I found, but I had to do a little research to figure out how large I should make the ventilation slots. I don't want to add a fan, as that will add noise to the box that may be picked up by the microphone.

    I've got high hopes for it. The other benefit of an iso-cab is that not only does it contain your amp's sound from the rest of the stage, but it also keeps extraneous stage sound from being picked up by your amp mic. The mic is isolated in the box along with your amp.

    Unfortunately, I didn't get much done after work this evening. I just belt sanded the edges of the floor so that I'll have a nice flat surface when I attach the sides. Cutting out the sides will be the next step.
     
    Last edited: Sep 3, 2013
  8. Tony M

    Tony M Well-Known Member

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    Smitty, is this the offspring of your "For better sound, hide the cabinet" thread?
    When that thread was active I saw this thread coming down the pike.
    (Hmmmmm....He's headed for an isocab.)
    :)
     
  9. smitty_p

    smitty_p Well-Known Member

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    Quite right! You are exactly correct. It just seems to make so much sense for small to medium venues where stage volume may be a problem.
     
  10. Gemini75

    Gemini75 Active Member

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    Jet City had one, don't know if they're still making them, for $400. From the reviews I read they worked pretty darn good.
     
  11. smitty_p

    smitty_p Well-Known Member

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    So, today I got the sides cut out.

    Here's a pic of the cabinet mocked-up with the sides. They are not fastened into place, yet. I just have them held in place with a set of pipe clamps.

    [​IMG]

    To give a little perspective, here's what it looks like with my Fender Champ. Of course, the space will be filled up quite a bit when I add the acoustic treatment.

    [​IMG]

    So far, so good.
     
    Gemini75 likes this.
  12. Sootio

    Sootio Well-Known Member

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    I'd try without any foam and see what kind of "environment" you get. Might be some sweet noise with that nice wood.
     
  13. smitty_p

    smitty_p Well-Known Member

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    Oh, I think I'll definitely want some acoustic treatment. But, I was considering leaving a small area in the back bare to sort of replicate the effect of setting your amp near a wall. I'll have enough room in front to put the mic nearly a foot from the front of the amp.
     
  14. Tony M

    Tony M Well-Known Member

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    There is enough room in there to hang a thin sheet of metal.
    Then you would have genuine plate reverb built in.
    Use a mechanical damper on it to control the intensity.



    (Don't pay attention to Tony. He's crazy.)
    (No I'm not.)
    (Yes you are.)
    (No I'm NOT!)
    (Now you're being contrary.)
    (NO I'M NOT!)
    (Never mind....)
     
    Last edited: Sep 4, 2013
    58pit and smitty_p like this.
  15. smitty_p

    smitty_p Well-Known Member

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    I got quite a bit done today.

    First, I set about the business of attaching the sides. In this picture I've got the sides glued in place and I'm squaring things up:

    [​IMG]

    Next, I'm installing vertical inside corner pieces. I'll fasten the sides to these. In this shot, I've glued the corners into place and I've used my nail gun to attach the sides to the floor and to the inside corner pieces. As I fastened each corner, I used my corner clamp in the picture above.

    [​IMG]

    This next shot doesn't show much, except I've screwed the sides in. Using the nail gun was just to hold things together so I could drill and countersink pilot holes and then drive the screws in.

    During this time, I was working kind of fast because the glue was still wet.

    [​IMG]

    In this pic, the cabinet is upside down on a piece of birch ply. I've just traced out the lid in this shot.

    [​IMG]

    This picture is a little dark, but I've just cut the ventilation slot in the lid and have tested it for size.

    [​IMG]

    Finally, this is the completed lid. The lid is upside down in this shot. The vertical inset sides form a perimeter for the sound absorption that I'll be putting in the lid. The Owens Corning 703 will fit into this inset. The wood will protect it as I take the lid on and off. Also, there is an 1/8" gap. (roughly 2 mm) between the edge of this inset and the sides of the cabinet, itself. This to allow space for some insulating strip that I'll be installing later.

    [​IMG]

    At this point, the main construction is finished. As far as construction is concerned, I need to install the casters, round off the edges of the cabinet, fill screw holes, and paint.

    Lastly, I'll install the sound absorption.

    Things are moving right along!
     
  16. smitty_p

    smitty_p Well-Known Member

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    I've made some progress, though nothing earth-shattering.

    I've filled the screw and nail holes. I've used a 3/8" (approximately 9.5 mm) roundover bit in my router to round off all the corners. And, I've installed casters.

    This photo shows the underside of the box just after I installed the casters. I put two rigid casters at one end and two locking swivel casters at the other end.

    [​IMG]

    This is just a shot with the box right-side-up on its brand new wheels.

    [​IMG]

    The actual build of the box is now done. I have to drill for the audio interface jacks, paint, wire and install the jacks, and install the actual sound absorption.

    Once I get the rest of my parts, it will go pretty quickly from here.
     
  17. smitty_p

    smitty_p Well-Known Member

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    Well, today I did something on my cabinet that is probably pretty pointless, but I did it, anyway.

    I caulked the interior of the cabinet and lid.

    Here's the cabinet caulked:

    [​IMG]


    Here's the lid caulked:

    [​IMG]

    The thought to do this came from reading elsewhere on iso-cabs others have built. The guys who build cabinets that are for just speakers, hence, needing no ventilation, will do this to try to close off any possible escape points for sound. Also, there is the idea that the caulk helps dampen vibrations in the corners where pieces meet.

    Well, all the parts on my cabinet are joined with Titebond and screwed and/or nail-gunned into place, so there is minimal risk of vibrations.

    But, I had a half-used tube of caulk laying around and I don't have all my parts, yet. So, in the mean time I figured I'd finish off the tube of caulk just for kicks. If I hadn't already had this tube of caulk, I wouldn't have bothered with it. It certainly won't hurt, though.

    Sorry for not having anything more exciting to show.
     
  18. Gemini75

    Gemini75 Active Member

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    What speaker are you going to be putting in this?
     
  19. smitty_p

    smitty_p Well-Known Member

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    It's not for just a speaker. I will be using this for my small tube amps. I'll be using my Marshall Class 5, my Vox AC4TV, or my Fender Champ.
     
  20. Tony M

    Tony M Well-Known Member

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    .....and a hanging piece of sheet metal with a
    mechanical damper for a genuine plate reverb.
    :)
     

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