>>Demeter makes the only mass-produced full-scale speaker isolation cabinet.
>>Other companies could custom manufacture these. I built my own, but I would
>>rather buy a mass-produced unit. Guitarists shouldn't waste time building
>>their own. My materials cost some $300. I made a large box out of 3/4"
>>fiberboard. That was still too loud. I made a larger box out of 3/4"
>>fiberboard. You can only hear the lowest bass leaking through.


>Would you post your box dimensions and a few construction details so I
>can get a fix on your loudness comments? Were these both double-layer
>boxes, for example?


A small open-back box for the speaker.
A large box for the speaker isolation cabinet.
A very large box for the 2nd speaker isolation cabinet to mute the first.

If you use 1" or thicker pressboard, rather than 3/4" plywood, and make a smaller cabinet, you'll have less of a boom/thud problem than my original, inner cabinet. A single box could mute your sound almost as much as both of my boxes, if you get serious about it. Portability is a concern. My inner box is light and more portable. But it's not clear whether you want an iso cab when you're not at home.


I made a box with 3 different dimensions, about the usual dimensions of a speaker cabinet. You see a rectangle when viewing it from the end, top, or side. I made it fairly big, to give room for bass waves. But it's inconveniently large.

Demeter custom-manufactures cabinets, as well as offering their iso cab for $500. I might order their iso cab, which is very ergonomic, and have them build an even bigger box to put around the iso cab. The outer box which would stay at home.


My inner box is 1/2 or 3/4" plywood, which is bad. It resonates slightly, at a high-bass frequency, when you strike it. Pressboard has a dull thud and is preferred.

Thicker wood is heavier but blocks sound more. The choices are yours.

Build a box with no two dimensions the same. Use 3/4 or 1" thick pressboard. Line it with fluffy material from a fabric store.

Design a speaker mounting surface. I made a simple open-back box for a 12" speaker. I chose to let it float on top of the fluffy material, to avoid transferring vibrations to the cabinet.

That system leaked too much low bass when driven by my 15 watt tube amp. I want silence. I don't want people to hear my long hours of experimentation. So I built a larger box around the first, and lined it with fluffy material. There is a 1" gap around the inner box, to enable it to slide out. The inner box should be portable. Demeter uses professional handles, mic holder, and a nice door. My box is crude and amateur next to theirs, and I need to spend much more time putting on the corner protectors and so on.

I used real amp wheels on the outer box. I was to cover both boxes with a rich tapestry. Tweed covering is incredibly expensive.

You'll need to somehow fasten the mic holder to the cabinet in a way that doesn't shake the mic. I just floated a mic stand on top of the fluffy material, which is bad -- unless you have a plexiglass window to verify that the mic is still positioned.

Opening and closing the box is a major problem. You need a door of some sort. I have to unscrew the whole end of the outer box and the inner box. The other sides are glued and screwed together.


Again, I encourage people to support Demeter and buy their $500 speaker isolation cabinet, because it's the only one available (other than the Micro Room). We need mass-produced gear for all guitarists to have easy access to genuine cranked tube-amp tone at low room noise levels.

My iso cab is certainly not roadworthy. It wants lots more work and more money. At least it works perfectly. I'd like to experiment with different speakers other than the Greenback: 15", 10", 8", and Fender speakers.

_____

av245 at lafn.org (J.R. Elswick) wrote:


>There are 3 common types of material which people may find when they go
>looking for "pressboard". One is common fiberboard, one is chipboard,
>distinguished by large wood chips visible on the surface, and the third,
>preferable for this application, is Medium Density Fiberboard (MDF),
>which is actually the highest density of the 3, and the densest stuff
>that is commonly available in 3/4" or greater thickness. None of these
>are as durable as plywood, which can be important for portable
>applications, and their added mass can work against them there too. In a
>multi-layer design with the inner designed to be removed and carried
>about, plywood might be a good choice for the inner box.

>>
>>I made a box with 3 different dimensions, about the usual dimensions of a
>>speaker cabinet. You see a rectangle when viewing it from the end, top, or
>>side. I made it fairly big, to give room for bass waves. But it's
>>inconveniently large.

>It's a good idea to use all the space one has available for something
>like this, although the material costs rise quickly with added volume. An
>isolation room should really be at least 1500 cubic feet, actually more
>to handle low bass, but that's inconveniently large for most people.


>>Demeter custom-manufactures cabinets, as well as offering their iso cab for
>>$500. I might order their iso cab, which is very ergonomic, and have them
>>build an even bigger box to put around the iso cab. The outer box which
>>would stay at home.

>I'm planning to check with them for hardware. I have a bit more room for
>the larger box, and I'll have to build in place since the entrance to the
>area is not large. I suppose using one of their boxes inside my largish
>box is an alternative, but it will sound better if I use the entire
>available space for a 2-walled box.

>> >
>>My inner box is 1/2 or 3/4" plywood, which is bad. It resonates slightly,
>>at a high-bass frequency, when you strike it. Pressboard has a dull thud
>>and is preferred.

>Bracing can be useful...the tighter you jam them in, the better, up to
>the limits of the materials.

>>
>>Thicker wood is heavier but blocks sound more. The choices are yours.
>>
>>Build a box with no two dimensions the same. Use 3/4 or 1" thick
>>pressboard. Line it with fluffy material from a fabric store.

>The various polyesters battings seem like good choices. The cheaper way
>is fiberglass, but it can be a bitch to deal with. Foam can be good, but
>is more expensive than the batting. The Micro Room uses foam....you may
>want to look at the review of this one in the 11/96 Electronic Musician,
>page 192-3.

>>
>>Design a speaker mounting surface. I made a simple open-back box for a 12"
>>speaker. I chose to let it float on top of the fluffy material, to avoid
>>transferring vibrations to the cabinet.

>Floating can add quite a bit of isolation, but other resilient materials
>may be preferable to the ones we've discusses, especially for weightier
>objects which will compress the fluffy stuff. Foam will work for lighter
>objects, and the next step after the common lightweight foams might be
>neoprene foam, going yet denser if one wants to float ceilings, rooms and
>the like. Neoprene would seem to be about right for floating a speaker cabinet.

>>
>>That system leaked too much low bass when driven by my 15 watt tube amp. I
>>want silence. I don't want people to hear my long hours of experimentation.
>>So I built a larger box around the first, and lined it with fluffy material.
>>There is a 1" gap around the inner box, to enable it to slide out.

>If you were to float the inner box on a pedastal isolated by one or more
>resilient layers, and surrounded it all with the fluffy stuff, you'd
>avoid the coupling that would likely be caused by compression of the
>fluffy stuff in the design you describe.

> The
>>inner box should be portable. Demeter uses professional handles, mic
>>holder, and a nice door. My box is crude and amateur next to theirs, and I
>>need to spend much more time putting on the corner protectors and so on.
>>
>>I used real amp wheels on the outer box. I was to cover both boxes with a
>>rich tapestry. Tweed covering is incredibly expensive.
>>
>>You'll need to somehow fasten the mic holder to the cabinet in a way that
>>doesn't shake the mic. I just floated a mic stand on top of the fluffy
>>material, which is bad -- unless you have a plexiglass window to verify that
>>the mic is still positioned.

>A simple way is to isolate the stand from the box with neoprene or the
>like. Microphone isomounts would be worth a try here too, either the
>cheap compact ones, or the spider-webs of elastic bands normally used to
>isolate some of the more vibration-sensitive mikes.

>>
>>Opening and closing the box is a major problem. You need a door of some
>>sort. I have to unscrew the whole end of the outer box and the inner box.
>>The other sides are glued and screwed together.
>>
>If you build one end in a "cap" configuration, so it would hold water if
>upended, and have this cap mate over a male protuberance from the main
>isolation cabinet, you can use simple spring-type latches of the type
>found on steamer-trunks and the like. Use resilient material at the
>mating surfaces as a seal...there are other good alternatives, but this
>is a good-sealing way to do it with cheap, readily-available hardware.


>J.R. Elswick av245 at lafn.org
> Santa Monica, CA, USA

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