Building an amp isolation cabinet

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Andrew707
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Building an amp isolation cabinet

Post by Andrew707 » Wed Apr 01, 2015 3:14 pm

So, I'm embarking on building an amp iso cab and since it's technically a space, I figured this is probably the best place for the thread.

My main question is about angling the walls of the cabinet so that none are parallel. I'm just trying to avoid any boxy sound and from that standpoint angling the walls seems a good idea. That said, will it really matter? The interior will probably be mostly lined with 703, or the equivalent, but then if I have the angled walls, I might not need to line the whole thing to deaden it; possibly leaving it a little lively sounding. Then again, with the walls in closer proximity, I may end up with comb filtering, so maybe I want to eliminate reflections anyway, right?

Hopefully making sense here and any thoughts on it will be appreciated.

Thanks,
Andy

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A.David.MacKinnon
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Post by A.David.MacKinnon » Wed Apr 01, 2015 6:26 pm

I've never done it but with a space that small anything you can do to cut down on comb filtering and reflections should be done.

Good advice and pics here - http://messageboard.tapeop.com/viewtopi ... ght=fridge

and here - http://messageboard.tapeop.com/viewtopi ... ht=amp+iso

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Post by kslight » Wed Apr 01, 2015 7:08 pm

Not as an ISO cab builder, but owner of a commercial example..I think it sounds best dead (I added quite a bit of extra foam to mine) and with a tight mic pattern. Unless you were making a rather large ISO cab, I don't think you would want reflections, and I don't know whether angled walls would help significantly. Considering you're talking about normally a loud amp being played in a very small space, I think you'll just end up with a boxy/phasey sound the less dead it is. I would think that if it did help, commercial ISO cabs would have angled walls too?

Andrew707
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Post by Andrew707 » Wed Apr 01, 2015 7:59 pm

Thanks both. Doesn't sound like angling things will make a difference, aside from complicating construction.

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Post by norton » Thu Apr 02, 2015 6:41 am

Too small a space for the angled walls to matter. The key to avoiding "woof" will be the internal dimensions and sufficient internal treatment ( 703 etc).

Acoustically speaking, square spaces reinforce modes and will not sound pleasant. Avoiding That will be very helpful.

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Post by Andrew707 » Thu Apr 02, 2015 9:57 am

I'm thinking about building it with dimensions based on the Golden Ration, so hopefully that will help. Probably going to get pretty big, though.

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Post by floid » Thu Apr 02, 2015 5:19 pm

Don't I remember reading the golden ratio isn't that hot for this? Gervais lists several, including 1 : 1.4 : 1.9 and 1 : 1.14 : 1.39
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Andrew707
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Post by Andrew707 » Thu Apr 02, 2015 9:24 pm

So, could I just pick one of those ratios and be fine, or is one better than the others? I'll be glad not to use the golden ratio if I don't need to; box size will be at least 2x3x5, which is doable, but will take some considering afa studio arrangement.

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Post by DrummerMan » Fri Apr 03, 2015 4:31 pm

I built a speaker iso-box out of an old broken fridge. Here's the thread about it.


My opinion based on my personal non-scientific experience is this: Don't worry about dimensions too much or reflections and just absorb as best as you can from all sides. You're nowhere near the size I'd personally want a room to be for it's sound to compliment the sound coming out of the speaker. I don't know what that minimum size would be (depends on personal taste and ratios and angles and stuff), but for me it's bigger than a bathroom or small bedroom.

You know, don't make it a perfect "cube" and all, but then just put a bunch of insulation in it and accept that there's not going to be any real sense of space that you'd want, and use it for what it's good for, which is allowing you to record loud shit in place where that's not normally possible. That in itself is very cool. I've gotten a lot of great use from mine, but when I want a room sound that doesn't involve reverb room emulation I've got to use an actual room.

Not trying to be a bummer, this is just my experience and YMMV...

Good luck!
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Post by vvv » Sat Apr 04, 2015 9:59 am

And don't forget to re-amp! (What could mean just playing the original ISO track over monitor(s) into a room and recording that and mixing it in parallel ...)
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Post by losthighway » Sat Apr 04, 2015 11:44 am

vvv wrote:And don't forget to re-amp! (What could mean just playing the original ISO track over monitor(s) into a room and recording that and mixing it in parallel ...)
Following that reasoning, I'd rather just DI the guitar and reamp it in a regular room later if your pressed for space/isolation.

I imagine ISO cabinets get really hot with tube amps.

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Post by vvv » Sat Apr 04, 2015 3:29 pm

Three things:

1. You are better off with a extension speaker in the ISO and the amp outta the box;

2. Even tho' the speaker is iso'd, you still get a different feel and may play different with the amp gained-up, as opposed to the guitar DI'd - at least, I do;

3. I called it "re-amp", but really it's more like playback using the distorted track to excite the room, which can usually be done quieter than when the amp is gained-up to record, and at a more convenient time, mebbe, then when you play the track.
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losthighway
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Post by losthighway » Sun Apr 05, 2015 6:14 am

Yeah, I always figured if I had a space issue that forced me to do guitars DI, I would get some kind of POD or amp simulator to feed whoever's playing guitars headphones. I would probably play differently too. A clean DI track is pretty hard to "rock" to.

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Post by Andrew707 » Sun Apr 05, 2015 9:14 am

Thanks Drummerman. Actually, it simplifies things, which helps.

-----

Anyway, I've decided to go with the extension cabinet approach. That will make the box smaller, plus it will be easier to make amp adjustments.

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Post by roscoenyc » Mon Apr 06, 2015 1:48 pm

I've been using ISO cabs for over 15 years. I have the Demeter and also the Randall.
Best tip I could give you is to also get a good quality amp attenuator. I started getting a lot better sounds out of the ISO cab when I wasn't driving the speaker in that small space so hard. I use the Dr Z Airbrake which is handy because it's not ohm specific like some of the others.

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