I need to build an Iso-Cab for a 1-12. Is there somewhere I can get the math to figure dimensions, amount of insulation, how much room to leave around the original speaker cab, DB reduction, ect?
I have found the prebuilt Randall and Grendalls, but I have all the stuff to build it already…
Thanks
Duff
Hi duffman:
I’m into this very same conundrum…
With these bass bins I’m building…
However, if your building this cabinet for guitar amplification applications, there are no critical dimensions for this cabinet… That’s what I’m led to believe… The important thing is…
as long as the air from the rear of the speaker is baffled…
so that the “Air” from the front of the speaker and rear of the speaker is not able to inter-mix at the same instance…
If the cabinet has a closed back then the Free Air Cone Resonance of the speaker is what the lowest frequency
is that the cabinet will produce…
I believe that to be correct…
For an Open Backed Cabinet, other conditions come into effect…
OR…
if the cabinet is sitting on the floor or a chair with a back or a stool or in the air with no back…
Well…
Bill…
Bill,
I found this: http://amptone.com/diyisobox.htm
This guys did what I had in mind. Something to stick my 1-12 cab into. I will probably make an additional exterior box of 2" extruded polystrene to slip over the Iso cab to quiet it even more.
Duff
I did a quick experiment in a home built Iso-cab. Does what I want but, I have a problem with lower Hz resonance and the cabinet rumbling across the floor. No matter what the volume, hit the right note and the whole cab resonates so badly you can feel it in you chest.
While looking for a better design I came across this: http://www.axetrak.com
Looks interesting.
Hi duffman:
Nice link…
That’s a beautiful cabinet/box…
It isn’t cheep…
I like the idea of a Bass cabinet, as well…
It appears as though they use a 6" speaker in the box…
Is that what you gather from reading the brochure?
Going into detail would go against what they are selling…
I have a suspicion that there is a baffle inside the box that the speaker is mounted on… Then there is some kind of microphone in the other part of the box, that can be adjusted to taste…
Is that how you perceive the ISO-cabinet, to be 
?
Bill…
Bill,
I looked over the whole site. I got that they use a 6 1/2" speaker. They also show an LED on the back that lights when you have a good signal, without external power…So I am guessing that:
They are using some type of voltage divider to drop/attenuate the incoming signal. Hence the LED lights via the incoming voltage from the guitar amp ouput. This has to be as they also show a switch to roll off high Hz, so the V divider doubles as the resistor in a RC filter. The box is sealed. They have, “a specially designed speaker and mic capsule in the the box.” …SPECIAL DESIGN… I think not…no-one is going to make the few speakers and mics that they would sell. It’s off the shelf hardware, has to be.
I can believe each one is handmade and to order. I think they are a bit pricey. They allow a 5 day no questions return and 3 year warranty on the speaker and mic capsule. The more I think about this the more I realize this is an encapsulated tuned attenuator with a speaker…Hmmmm I think I need to hit the old breadboard…
Wouldn’t a “box in a box” design with dampening devices or materials between the boxes keep unwanted resonances at bay? I think seen a cut-away drawing of somebody or others design and that’s what they did.
I’m following this with interest… I play pretty much exclusively at church and they don’t allow amps on stage. If I could build or buy an iso-box though… I WOULD be busting out the old valvulating toober amp. 
D
PS Was it Randall that seen? Didn’t they make an iso-cab with an integrated mic mount?
PPS Yep, it was Randall… That doesn’t look like a double box design though…
Quote:
If the cabinet has a closed back then the Free Air Cone Resonance of the speaker is what the lowest frequency
is that the cabinet will produce..
I believe that to be correct.
Not quite Bill; a speaker will produce usable frequencies at well below the speaker free cone resonance, well, with a properly designed cab it will.
One can either extend that resonance downwards by making the system resonance lower by means of a tuned port etc., (but you run the risk of blowing the cone at the system sub resonant f's),
or, you can just supress the free cone resonace, but then you're stuck with the 6dB per octave drop off.
So, at the end of the day, as always, it's a trade off, and you just have to suck it and see!
Anyone interested:
Some research shows using the Golden Ratio 0.6 : 1.0
or 1.0 : 1.618 should reduce interior standing waves and resonance. So if you frontload a baffle and make a cavity from the front of the baffle to the inside back 12", then the cavity in front of the speaker should be 19 1/2" deep.
Experimenting last night I also found de-coupling the cabinet from the floor reduced the resonance greatly. My first epxeriment was with a wooden crate I had sitting around my shop and dropping in a 1-12 open back cabinet faceup. I lined it with that 4" miracle foam, you know the stuff they make those expensive matteress out of. I just laid a piece of foam over the top to close it, nothing tight. Running the head full tilt in 1/2 power mode (50w) you could easily stand next to it and have a conversation.
So with this info in hand, this weekend and as time premits I will do a blueprint, cut list, and part list. I will be making the cab out of 1" MDF. Hopefully assembly to start by end of next week. Once done & tested, if it works, I will be glad to share the design with anyone interested.
Boy…
I am fascinated…
I sort ta like R-&-D…
till I get antsy…
Then I want to get it up-and-running…
The isobox that they make is nice… BUT…
they want a lot of coin for it…
Bill…
Here are some quick drawings with dimens for downloading. Unfortunately one of the ends has to be pieced together to get everything from one sheet. I will put that one behind the speaker as I will need to make cut outs for mounting plate for 1/4" & XLR ins anyway. Baffle size & hole based on Celestion 70/80.
http://home.mchsi.com/~duffman123/IsoCab1.jpg
http://home.mchsi.com/~duffman123/IsoCab2.jpg
http://home.mchsi.com/~duffman123/IsoSheetCut.jpg
Hardware, where to put the foam on the inside of the top, rubber feet, ect…I figured you guys would know where to put that stuff…
Duff
Hi duffman:
There’s some nice design and effort into this project…
Do you have your cabinet up-and-running yet?
Will you have your mic and mic mount adjustable?
What mic are you gonna be using in your design… ??
and… well… some other details…
What would prohibit this cabinet for say a “Keys” or “Bass” application ? OR… any other instrument… Fiddle or Mandolin or Harp or Flute or Sax… ?
Bill…
I can envision one of these cabinets for the wox Studio… 
2 short clips done with what has been dubbed the “Muffler”. I mounted an Eminence Man O War 16 in the cab. I’m really diggin this speaker. In clip #2 not only is it dirty but you can hear the guitar chiming as well. Mic is an SM57.
http://home.mchsi.com/~duffman123/muffler1.mp3
http://home.mchsi.com/~duffman123/muffler2.mp3
This cab has worked out well.
Duff
That sounds good. Is there much sound in the room (outside the box) when
you crank it to spinal tap 11?
And Ive seen guitar players on stage with their amp/speakers mounted inside
plexi glass boxes (miced in the box). Sounds good as part of the loud live
mixes, but wonder what the non-padded plexi-glass does to ovrall tone. The
sound board operator might need to do special EQ, or maybe not if close miced.
Do you find you need to make any EQ adjustments using the box (at guitar/amp/mixer)?
I would highly recommend that you not use studio foam. You will spend much less money and be much better served using OC703/705 or something of that nature. However, what it your goal? Isolation to the point of being able to crank it and not pissing off the world? Or do you want more or less dead silence? If the latter, you are going to have a rough way to go. Essentially you will have to build a cinder block BBQ to put the thing in… cinder block has VERY low resonance frequencies and is cheap… but we know all the down sides. Heavy, ugly, not conducive to opening a closing. I guess I would do a best of both world and build a mini closet out of 2x4s and 5/8 Type X drywall and Green Glue. You can then do a two door air lock with weather stripping.
For myself, I am just interested in knocking some of the sound down in a small shared
living space, I am not looking for total silence.
But thinking about the box thing, probably not what I want.
Wouldn’t you lose
some extra sustain that you normally get when guitar and speaker share the same air
space?
With line 6 I can play thru the monitors and keep the volume somewhat controlled,
but still pick up some of the feedback.
The head I am using has 1/2 & 1/4 power settings. At 1/4 or 25 watts dimed I get a loud whisper, at 1/2 or 50 watts a loud talking voice. I haven’t tried it at full power…whats the point. I did change my design by splitting & hinging the lid, adding a compression gasket under the lid, and adding a hinge to the end the speaker points to. I can open it up to be a 120 Watt, closed back, front mounted, 1x12 cab.
A few other things I found, dont use reverb or short delay, long delays or echo work fine, as does chorus.
If I did this again I would make the sides, lid, & bottom out of 1/2" MDF doulbed,
more of a box within a box design.
PingCat,
I have not changed EQ settings on the mixer, I did back off the bass on both overdrive channels 2 indents each. I would like to try a Beta57A, Beta58A, and a couple of other mics. But that will have to wait…spent my allowance. BTW with the speaker and a new 30ft mic cable this project cost me about $150.
Bubba,
I piss-off most of the world in my daily life as it is, so that’s not a concern. Being able to lay down tracks at 3:00am without waking the wife…NOW THATS A CONCERN!
As for the foam, I used 2" medium density miracle/memory/isotonic foam. You know the stuff they make those fancy matteress, pads, and pillows out of. Works reall well.
As for cinder blocks, I dont think I will be building a panic room/bomb shelter in the basement anytime soon…walk in beer cooler maybe…
Duff
Quote: (duffman @ Aug. 28 2009, 6:24 AM)
If I did this again I would make the sides, lid, & bottom out of 1/2" MDF doulbed,
more of a box within a box design.
If I hear you correctly, the box within a box idea would mean you'd put the foam/insulation between the two boxes
? Bill..