Patent for Isolation Cabinet

[chipdog]

Ran across this on Google today. Any opinions on whether the theory holds water?

http://www.patentstorm.us/patents/6434240-fulltext.html

[teleamp]

Sound cancellation is very real and more than a theory.

I think some of the high end cars employ it.

I wish I could find an "over powered sub woofer sound canceler".

MikeY

[chipdog]

Originally Posted by teleamp

Sound cancellation is very real and more than a theory.

I think some of the high end cars employ it.

I wish I could find an "over powered sub woofer sound canceler".

MikeY

Having owned Sound Cancellation headphones, I don't disagree with your statement. I'm curious whether the idea of reversing the polarity of one speaker in a dual speaker iso cab will eliminate the boxiness (he calls it "muffling effect") from the tone of the output. If so, I'm there.

[Randy]

That's very interesting. I'd be surprised if that completely solved the boxiness issue associated with iso cabs though. It sounds like their premise is that the air has no where to go in a sealed box and that's what creates the boxy tone, but from my experience that's not the only issue.

I built a couple myself based on the Randall and Demeter sizes - 18" X 18" X 30", and no matter how I tweaked mike placement I couldn't get them to sound natural. Interestingly though, I did get my best results using the phase reverse switch on one of 2 mikes in order to scoop out some of the boxy mids.

I tried an experiment once where I recorded a clip with the box sealed closed, and then did the same clip with the lid taken off (mine open and close from the end). I thought for sure the clip with the lid off would sound much better and less boxy, but in fact it sounded much worse and even more boxy. My conclusion was that it's not the lack of air movement but the 'tubular' design of my iso cab, where you've got 4 walls adjacent to a speaker which prevent the sound waves from dispersing radially and create a hollow tube effect. Removing the lid made this even worse since it eliminated the bounce back waves which must have reduced this effect somewhat.

I'd bet a single 12" speaker in a large box, say 6 ft cubed would sound very natural. I think it's a matter of volume and space much more then air movement. Here's a pic of mine;

[WahmBoomAh]

Originally Posted by Randy

I built a couple myself based on the Randall and Demeter sizes - 18" X 18" X 30", and no matter how I tweaked mike placement I couldn't get them to sound natural. Interestingly though, I did get my best results using the phase reverse switch on one of 2 mikes in order to scoop out some of the boxy mids.

I'd bet a single 12" speaker in a large box, say 6 ft cubed would sound very natural. I think it's a matter of volume and space much more then air movement. Here's a pic of mine;

Looks like a very well built cab . How silent is it ? Do you get keeper tracks after all or have you decided the end result isn`t up to your expectations ?
6ft cubed is too large for my apt ... How large before it opens up ?
maybe 4 ft ??? Would love to hear something on mp3 ... As you might have guessed , my neighbors are anxiously awaiting this info !!! thanks , Paul

[Randy]

Originally Posted by MooWahmBah

Looks like a very well built cab . How silent is it ? Do you get keeper tracks after all or have you decided the end result isn`t up to your expectations ?
6ft cubed is too large for my apt ... How large before it opens up ?
maybe 4 ft ??? Would love to hear something on mp3 ... As you might have guessed , my neighbors are anxiously awaiting this info !!! thanks , Paul

Thanks! It's a 3/4 plywood shell, then a layer of vinyl mass and 1/2 of sheetrock. You still get bass rumble through the cab, but you'll be able to get a good strong miked signal without disturbing anyone in the next room. If you plan on cranking a 50 or 100 watt head into power tube distortion though, it isn't going to happen.

Here's a few MP3's - these two were both done in the iso cab, with one of the mikes phase reversed. I have 2 of these cabs so I might have actually used 2 mikes straight and 1 reversed... I just can't remember. You can hear the weird artifacts from the phase reversal.

http://www.mp3lizard.com/download.cfm?id=13715

http://www.mp3lizard.com/download.cfm?id=6366

For reference, I did the lead track on this clip at TV levels, with an E609 and an SM57 pushed up to the grills and the mike preamp cranked to get a decent level. I think the sound is much better, and it wouldn't have disturbed anyone outside the room. You could always throw a moving blanket over the mike / cab to reduce the volume even more if you wanted. A cheaper and better solution to an iso cab IMO.

http://www.mp3lizard.com/download.cfm?id=13717

[Figher53]

If you're using it at home for recording and not for touring, I put together a DIY one that works great for very little money.

http://thegearpage.net/board/showthread.php?t=247840

I've already used it on around 10 projects and the guy I've sent tracks to is really happy with the tones. No boxiness at all. The iso cab also sits less than 5 feet away from me while I'm tracking. As long as I'm working around 80db while tracking the leakage from the cab (ALL is cabs will at least have some, I've tried several) is negligible.

As far as the cancellation patent is concerned, I'm very skeptical. Theoretically is possible to engineer the cab size and specs to cancel out some of the lower mid frequencies that contribute to the boxy sound, but you'd definitely be screwing with the other frequencies in the spectrum as well. And the lower-mid cancellation wouldn't occur as a broadband event, either. You'd be weeding out specific frequencies and leaving others either untouched or phased to hell. I'd have to see it and hear it to believe it.

[WahmBoomAh]

Yeah Randy ! Thanks for the quick info .... Nice feel and ideas in your playing !!! ... I do hear some off kilter type mid factor to the samples but unless I was there to dial in the desired tone ...I couldn`t say if it`s a part of what the player is going after or an "artifact" ..My impression is that I like the result better than software or cab sim stuff .
BUT ... the tone you`re going for is much more saturated (i.e amp compressed) than what I`m hearing ... I would imagine a "clean" sound (i.e. Knofpler) would reveal much more deviation from a flat amp sound .

The last sample was kind of washed in behind the second guitar distortion ....but i thought it sounded a little more full frequency ...

anyway ...Thanks again ....nice playing !

I would consider this a positive vote for an isocab

[Randy]

Originally Posted by Figher53

If you're using it at home for recording and not for touring, I put together a DIY one that works great for very little money.

http://thegearpage.net/board/showthread.php?t=247840

I've already used it on around 10 projects and the guy I've sent tracks to is really happy with the tones. No boxiness at all. The iso cab also sits less than 5 feet away from me while I'm tracking. As long as I'm working around 80db while tracking the leakage from the cab (ALL is cabs will at least have some, I've tried several) is negligible.

That's a great idea - sure would have saved me a lot of time and effort. I'm convinced the bigger the box the better. The fact that you have an actual speaker cabinet inside the box, instead of the box itself being the cabinet probably doesn't hurt either.

[chipdog]

Originally Posted by Randy

That's very interesting. I'd be surprised if that completely solved the boxiness issue associated with iso cabs though. It sounds like their premise is that the air has no where to go in a sealed box and that's what creates the boxy tone, but from my experience that's not the only issue.

He claims that it offsets it, but doesn't eliminate it. Not sure if he believes that the air movement alone is the prime factor. Perhaps it's the 'coordinated' air movement, i.e. the synchronous actions of the reverse polarity speakers that impacts the tone. Or perhaps it's some audible element ala a wave cancelling effect. I want to build one in a 4x12 sized enclosure to test it out. Worst case scenario is I end up with an expensive 4x12 with two speakers in it.

[Figher53]

Originally Posted by Randy

That's a great idea - sure would have saved me a lot of time and effort. I'm convinced the bigger the box the better. The fact that you have an actual speaker cabinet inside the box, instead of the box itself being the cabinet probably doesn't hurt either.

I also think the bigger the better, and that the amount of absorption going on is the key. If you're only stopping the sound from going out and keeping it all in the cab with little absorption, you're going to get a skewed tone. But if you absorb as much as possible you're in better shape.

I never thought about the cab inside a cab thing being a big factor. I think you're right. Less resonance.

I also reread my last post and wanted to clarify that the 80db I referred to is the monitoring level from my speakers, not the volume the cab is putting out. I'm playing at a level loud enough to get some nice speaker coil movement. The power scaling in the Suhr Badger I just picked up doesn't hurt the tone, either. :AOK

[chipdog]

Any other opinions on whether this patent will or won't affect the tone of an iso cab signal?

[chipdog]

Well, I just finished designing a custom Isolation Cabinet to try out this patent. Bob Burt is building it for me and it will be a good test to see if wiring 2 speakers in reverse polarity will have any affect at all on the "boxiness" of the tone. It's going to be a heavy sucker, though, with all of the sound insulation I'm planning (2 lb/sqft GK Soundblocker II vinyl lining, 2" GK foam, carpeted exterior). I'll post a tone report and pictures after it's complete.

[Randy]

Originally Posted by chipdog

Well, I just finished designing a custom Isolation Cabinet to try out this patent. Bob Burt is building it for me and it will be a good test to see if wiring 2 speakers in reverse polarity will have any affect at all on the "boxiness" of the tone. It's going to be a heavy sucker, though, with all of the sound insulation I'm planning (2 lb/sqft GK Soundblocker II vinyl lining, 2" GK foam, carpeted exterior). I'll post a tone report and pictures after it's complete.

Let us know how it turns out! I guess the ultimate test of how well it works would be to first wire both speakers normally and make a clip, then wire one in reverse and see how much of a difference it makes.

This has me wondering though.... will a speaker really move as much when wired in reverse polarity as it will when wired normally? Can it physically travel as far in the reverse direction, and will it damage it to do so? I would think they are made to move forward and return, not backwards, but I know nothing about speaker design.

[sethmeister]

I too am skeptical about the patent. In theory it is sound but I think there's more to the equation in real life.

I agree with the sentiment that a larger interior volume will yield best results.

The box I built and use is more than 6 cu ft interior volume and the sound quality is very good. I built it using 3/4" MDF screwed and glued and sealed w/ caulking. I have jacks for 1/4" speaker and 2 XLR mic connections. Inside is covered with OC703 wrapped in fabric. a 1x12 cab sits on an auralex gramma pad inside with 2 mic stands. This inner box sits on 4 rubber pucks inside a larger outer box with about 2" of space all around it. The outer box is same MDF construction. The idea is a mass - air - mass construction with dead air space between the boxes. When I want to use it I just plug my amp head's speaker out into the 1/4" jack on the side of the box and hook one or two mic cables up to the XLR jacks and away we go.

The downside of course is that it is very large and completely non portable but since its only used in my studio thats not a problem. I'll see if I can take some pics and post them.