Effect of isolation box on guitar tone

Silverjet89 · Post by **Silverjet89** » Sat Oct 28, 2006 6:42 pm

So I was reading that AC/DC uses a Marshall 4x12 in an isolation box for recording and live performances. I was wondering what effect the box would have on the actual tone of the amp when mic'd.
I've always been amazed at how punchy and clear their guitars sounded and wondered if the iso box might contribute to that.

I've tried dozens of different miking techniques but have never been able to get that punch and bite even if the amp sounds right.

Thanks,
Kirk

RustyBrooks · Post by **RustyBrooks** » Sun Oct 29, 2006 9:30 am

My experiences may not be typical since I was using a home-built ISO box. Also, instead of isolating and micing an existing (large) cabinet, I built a very small 2x10 cabinet and put that into my (probably too small) iso cabinet.

I found that there was not enough bass. I also found it to be a terrific pain in the ass to adjust the mics because it was hard to open things up, move the mic, and close it again. Working with that thing had me imagining making some kind of servo-driven mic positioner. Actually, I'd still like one. I was thinking recently it would be awesome to put my cabinet in the attic above my garage but going up and down to reposition mics would drive me batty and I have no one to help me.

GooberNumber9 · Post by **GooberNumber9** » Sun Oct 29, 2006 5:55 pm

I'm going to second that. I also built and isolation cabinet and it sounded terrible. AC/DCs cabinets are probably the size of vocal booths or larger. I was trying to build one for quiet recording in an apartment. I found a DMC Cab-Tone and a THD Hot Plate were the best combination for that.

I wish I knew how to get that AC/DC sound.

Todd Wilcox

Silverjet89 · Post by **Silverjet89** » Mon Oct 30, 2006 2:50 pm

I wish I knew how to get that AC/DC sound.

Yeah, anybody have any tips to get the AC/DC guitar tone on recordings?

Thanks for the response about the Iso boxes.

RodC · Post by **RodC** » Mon Oct 30, 2006 5:23 pm

AC/DC sound, My son says Angus said in an interview:

I never turn any knob past 5 except the Volume, he puts it on 8.

Most of the time he has an old marshall without a master vol.

Malcom never plays barre chords, but uses very big chords on a semi hollow with a gravely sound, not much distortion. His rhythm style lends a lot to their sound.

Silverjet89 · Post by **Silverjet89** » Mon Oct 30, 2006 5:39 pm

AC/DC sound, My son says Angus said in an interview:

I never turn any knob past 5 except the Volume, he puts it on 8.

Most of the time he has an old marshall without a master vol.

Malcom never plays barre chords, but uses very big chords on a semi hollow with a gravely sound, not much distortion. His rhythm style lends a lot to their sound.

I can get that sound out of my '70s Marshall with my Gretsch but I can't get it to translate when I record it. Any ideas how they mic the cabs?

drumsound · Post by **drumsound** » Mon Oct 30, 2006 5:46 pm

One thing I tend to do with guitar and bass cabs is to put a small piece of carpet on the floor in front of the cab. Early reflections from the floor can be quite problematic.

I always think of the AC/DC tone as really simple in your face sound. I'd jam a mic or two right up on the grill, if it needs to be brighter move it more towards the center if darker more towards the edge.

Silverjet89 · Post by **Silverjet89** » Mon Oct 30, 2006 6:14 pm

I always think of the AC/DC tone as really simple in your face sound. I'd jam a mic or two right up on the grill, if it needs to be brighter move it more towards the center if darker more towards the edge.

That was my first instinct. I've tried it with several mics and pres but it never has that punch and crispness they get. I'm sure technique has something to do with it but I should be able to get close.

RodC · Post by **RodC** » Mon Oct 30, 2006 6:14 pm

Yep and a lot of that would depend on the mic/pres you have access to. I always try the carpet on or off the floor, usually I like it on the floor. Also try rasing the amp and or mic the top speaker.

The crutial thing is usually position, if the amp sounds like what you want, have someone move the mic while you play and listen for the best position/angle.

I would guess streight on close to the center?? Also, make sure you are not distorting your mic or your preamp, this can be disguised by loud distorted guitar sounds. If you have to EQ a lot (Other than rolling some highs and lows off, and maybe a small dip to fit something in) then you prob need to try different positons on the mic.

I would try a dynamic right aginst the grill and a condensor about a foot back. Move the condensor around until it is reinforcing the sounds I like. ALSO try twisting it so that the diaphram is not streight on. I like some of them at about a 30 to 45 deg angle. The condensor would be about 10% of the total sound, and I would nudge that track until it was reinforcing the frequencies I like.

Also check out the thread running here on recording levels, if your pre is running out of headroom it may sound better at -18 to -12 instead of trying to slam the converters.

For their sound I bet you end up with both of them near center.

MoreSpaceEcho · Post by **MoreSpaceEcho** » Tue Oct 31, 2006 5:20 pm

RodC wrote: Malcom never plays barre chords, but uses very big chords on a semi hollow

the key! the key i tells ya.

Silverjet89 · Post by **Silverjet89** » Tue Oct 31, 2006 5:54 pm

RodC wrote:

Malcom never plays barre chords, but uses very big chords on a semi hollow

the key! the key i tells ya.

I'm playing a Gretsch Silver Jet with TV Jones pickups and a '77 50 watt Marshall 1/2 stack. Pretty close to Malcoms set-up.

After messing around for the last few days I got pretty close using an AKG D112 about 2" from the grill half way between the center and edge of the speaker. It still doesn't seem to have that bite but I might be able to get that by messing with the EQ. An SM57 through an LA-610 slightly off center is similar but was bit fuzzy and didn't have the definition.

I want to use this sound as the rhythm guitar in a power pop song with female vocals. An Ric 12 string for the other guitar. Basically putting a bit more power into power pop. So far it seems to be working.

Thanks for all the advice.

RodC · Post by **RodC** » Tue Oct 31, 2006 6:12 pm

Be careful with the D112 it has a pretty big smily face built in, a lot of stuff missing you may want for the guitar sound your going for. You might want to cut the highs and lows with a shelf and boost the mids. Use a Q of around 2.8 and sweep around between 1k and 3k (+3db or so) to see if you can make up what is missing.

Silverjet89 · Post by **Silverjet89** » Wed Nov 01, 2006 8:33 am

Yeah, I noticed the mid scoop. I think I'll try to mix in a bit of SM 57 too for the mids if I can't get it with the EQ.
The D112 just seemed to have the punch I was looking for. It's the first time I've tried it on guitar.

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Effect of isolation box on guitar tone

Effect of isolation box on guitar tone

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