I usually do sound for loud rock and metal bands who almost always have 4x12 guitar cabinets. I've been thinking in my head for some time about an idea - Making a large wooden box that would encapsulate an entire 12" speaker. Making the box deep enough so that a large diaphragm microphone can be placed at distance to capture most (or the whole) of the entire speaker output instead of one point of the cone.
I was thinking the inside of the box should be heavily insulated with foam to deaden it.

I'll be buying a sE X1 this weekend and intend to build this box within the next few weeks or as free time permits!

Am I letting myself into a world of trouble or has anyone here ever done something like this?
I've seen and heard bands who isolate whole cabs off stage and it sounds amazing out front but that just isn't an option with most bands that I usually deal with (or the venues that I work in).

Thanks.

It's been done! See:

http://www.soundonsound.com/sos/jun10/articles/vbampbox.htm

http://www.soundonsound.com/sos/jun03/articles/hermitcab.asp

AFAIK you need to do a box-within-a-box type construction for it to be most effective (a bit like the room-within-room soundproofing idea).

Cheers!

Chris

One way of doing this without having to carry around another box is to use a flightcase trunk as the box that has the mic in it.
I've seen a case for two AC30s used like this.
One would go out onto the stage for monitoring and the other would be left in the case, plugged in and fed the output from the guitar rig. An XLR adapter was drilled into the side of the case and there was a fixed gooseneck mic stand inside with a SM57 on it.

Plug it in, crank it up, close the case and there's your sound.
At the end of the night, the on-stage cab gets put in the trunk and it's ready to go.

HTH.

Stu.

Some interesting articles there but I don't think they would be practical for live use for me. Some of the ideas you have are great if you're with one band but I'm talking about doing sound for different bands every time I engineer. So having 2 different cabs or combos per guitarist usually isn't an option for them.

I'm just looking for advice to make sure I'm not foreseeing some major problem from doing it. In my head it will be portable enough to carry around and will be constructed so as to attach to a small mic stand comfortably.

Hopefully I can draw up some plans soon and share them here. I'll let ya know how I get along!

The biggest problem you are going to have is that a lot of guitarists will not be amenable to the idea. The design of speaker cabinet and the type of drivers used are a big part of a guitarist's sound.

Before investing time and money in the project it might be worth talking to a bunch of the guitarists you work with and see whether or not they buy into the idea. Remember, you will need to plug your iso-cab into the speaker outputs of their guitar amps. And with valve heads you will need to get the loads right too. As most 4x12's are 16 Ohm, you would need to make your iso-cab the same AND the amp would need to have the option to connect both cabs in parallel at 8 Ohms. If other guitarists have 8 Ohm cabs, then you would need to build another box to match those.

And someone will have to accept responsibility for changing the output settings on the guitar amps AND putting them back again. I speak as someone who has lent a very good amp to different people and had it returned badly damaged by impedance mismatching because the output had been changed to work with different cabs and not returned to normal.

Yes, this does work very well on big tours. But that is because the guitarists buy in to the plan, there is pre-production work to get everything working properly, and there is a guitar tech who will be setting it up every night.

Andy

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When the going gets weird, the Weird turn Pro.

Maybe I haven't explained properly what I am actually looking to do.
I'm simply going to build an isolation box for a large diaphragm condenser microphone that will fit over the whole grille surface area of one of the four 12" speakers of a guitar cab.
I won't need to take outputs from amps or anything like that (until I get a red box!)

I had considered doing something similar for QC checking complete combos. A 5 sided box that you push the cab onto, probably need a bungee or two, and a small cap mic, probably an omni. The amp would be driven with band limited white noise and analysed...Age and illness intervened and I never got past thinking about it!
For 10sec' noise bursts noise egress would not have been a problem (the amp would have been 20mtrs away in another room anyway and balanced lines to and fro) but do not think that stopping the front radiation, even if you could 100%, will reduce the sound leakage that much from a 4x12. Try wearing some 20dB deffs and listening to a 4by whilst a guitarist goes total A.S.with a 100watter. Still quite a row! (and you will LOVE all the LF creaks and groans from the cab that you have never heard before!) That, is about as good as it will get.

And don't think that "foam" will do diddly to stop noise, mass is the only way to do that. You will need some way to kill internal reflections (hi fi speaker cab science here)but leakage can only be stopped by high density walls. Caste it in concrete!

Dave.

If I understand this correctly, you are trying to find a way of moving the mic further from the cab without spill from other instruments getting in the way. I suspect you will need a very long box to get far enough away to make any difference and you will end up with some kind of pipe which will have its own problems. I'd suggest that mic choice and positioning would be more fruitful avenues to look at. Moving a mic an inch or two to the side has a big effect on the sound from a guitar cab.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Just don't do this:



Love that image!

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Do you need real drum tracks? http://www.drumtracksdirect.co.uk/

Quote ConorKebab:

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Maybe I haven't explained properly what I am actually looking to do.
I'm simply going to build an isolation box for a large diaphragm condenser microphone that will fit over the whole grille surface area of one of the four 12" speakers of a guitar cab.
I won't need to take outputs from amps or anything like that (until I get a red box!)

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What will be gained by putting the mic in a box? You're giving yourself all the problems of padding the box so it doesn't SOUND like a box. And unless there's another sound source a few inches away, the inverse-square law will do more for isolation than any box could!

Quote Exalted Wombat:

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Quote ConorKebab:

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Maybe I haven't explained properly what I am actually looking to do.
I'm simply going to build an isolation box for a large diaphragm condenser microphone that will fit over the whole grille surface area of one of the four 12" speakers of a guitar cab.
I won't need to take outputs from amps or anything like that (until I get a red box!)

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What will be gained by putting the mic in a box? You're giving yourself all the problems of padding the box so it doesn't SOUND like a box. And unless there's another sound source a few inches away, the inverse-square law will do more for isolation than any box could!

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Wombat has hit it here.

What exactly are you trying to gain? Are you trying to gain a better sound form the cabinet? Mic position does most of that. Are you trying to gain more isolation in the mic? My experience is with guitar amps isolation is the least of my concerns with a directional mic on the cabinet on a stage. Isolating other things from the cabinet is a much larger issue. Which brings to the last thing you might be trying to gain, which is isolation for other mics from the guitar. In which case the box would be a good idea, but would need to enclose the entire cabinet, and address all the other issues that have been brought up(Properly building so it doesn't SOUND like a box, monitoring for the guitarist and ability to modify controls easily, etc.

More standard practice for this is to use a gobo on stage rather than a box. Either a plexi shield, or in better cases a gobo built for it with a combination of rockwool insulation and lead sheeting, which primarily removes some of the high end really, but can make a difference in a live situation.

Seablade

I usually use e906's or 57's for guitars but as a few here have mentioned an inch or two can make a lot of difference. So what I'm trying to achieve is to have a large diaphragm mic placed approx 6-8 inches away from one speaker so as to capture the entire sound of the cone.
As I said in the beginning I usually do sound for LOUD bands (cymbals mainly being a problem bleeding into mics) so the iso-box I will build is simply an attempt to cut out bleed from the rest of the stage. The reason I've brought it up here is because I don't know if I'll just be making life harder for myself. Will the box make the mic sound rubbish?
I also wanted to see if anyone here has done that before?

Quote ConorKebab:

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As I said in the beginning I usually do sound for LOUD bands (cymbals mainly being a problem bleeding into mics) so the iso-box I will build is simply an attempt to cut out bleed from the rest of the stage.

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Have you tried controlling the sound of the cymbals instead? Do you use a drum shield?

I have to be honest, I have mixed quite a few 'loud' bands in my time, and still mix rock and roll weekly essentially, and never have had a problem with bleed into my guitar mics.

Quote:

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The reason I've brought it up here is because I don't know if I'll just be making life harder for myself.

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This is a given. What you are likely really asking is, will it be worth the trouble.

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Will the box make the mic sound rubbish?

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Doing it correctly won't help the sound of the mic no. Doing it incorrectly will definitely hurt beyond a point you want to. Will it work in theory? Yes if done correctly with minimal damage to the sound, but still some. But if you are only covering 1 driver out of the 4, how are you attaching it? How are you keeping it from vibrating? etc. These are all things you have to think about and answer before I would even consider going down that road.

But again, I return to, if you are having problems with cymbals bleeding into your mics you ened to look at other things first. Either your drummer is way to loud and can't control his dynamics, or your guitarist is playing way to quiet (Believe it or not this does happen). You can also help with a low pass filter to cut out a lot of air that your cymbals are much stronger than your guitar in, not something I generally use but can help depending on the style played and how heavy the distortion is.

Honestly if a guitarist can't get loud enough with a 4x12 Marshall for a stage, you really need to look at your levels on the stage. The most common complaint I get from bands I mix with such a rig is that the rest of the band complains about the volume of the guitar and even forgets the drummer is there until that gets fixed.

Seablade

Putting it in a box changes the sound. Period.

Unless you are going for a room sized box that is...

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Daniel Davis
Edinburgh Recording Studio Windmill Sound

OK, I know this is a specific case and some of the caveats mentioned above apply, but check out this starting at 2.15:

Mick Huges - Metallica

Am I still not explaining this well enough? The reason I want to use a large diaphragm mic is to capture the sound from an entire speaker, some 6-8 inches away from the cone. I'm not having real cymbal bleed issues with my usual 57 or 906 close-mic set up. This box that I want to build is to keep out stage noise from my condenser mic that will be 6-8inches from the cone.
I plan to build it so it attaches to a regular mic stand. I don't need advice on my current 906/57 set up. I just want to see if this condenser-in-a-box enhances the guitar sound out front if I can capture the entire speaker instead of just one particular part of the cone with a 57 etc.
Capice?

I suspect the box will do peculiar things to the sound (but they just might be INTERESTING peculiar things!) Maybe it will mess up the directionality of the mic in the same way cupping hands round a SM58 does - you think you're masking it from feedback but actually increasing it by turning the mic into an omni! So you might get MORE drum spillage :-) Give it a try and let us know.

Will do. I'm getting the X1 tomorrow so hopefully start building this box next week.

It's a great idea but has its place.

Bands using IEM monitors are all heading this way to get the on stage volume to nothing. I see this allot of the time with bigger bands. the scrims on stage dont have amps behind and the amps/cabs are in Iso cabs behind them or at the side of the stage with the techs guitar world built on top to save space on stage. it also gives you allot more control over the FOH sound when you only have a drumkit to contend with. you don't have the backline interacting with the FOH sound at all! Usually these cases are big. and have in speaker and XLR out on the side so they dont have to be opened unless there is an issue.

On smaller shows thing 50 - 500 capacity where the PA systems are inadequate allot of the bands sound actually comes form the backline itself, to give the room a fuller sound where the PA system is lacking.

Kim Watson

Edited by Polaris (15/05/12 12:31 PM)

Quote ConorKebab:

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The reason I want to use a large diaphragm mic is to capture the sound from an entire speaker, some 6-8 inches away from the cone.

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The diaphragm size has no bearing whatsoever on the polar pattern of the mic. A large diaphgram design has a slower transient response, lower HF roll-off, stronger HF resonances, more off-axis coluration, and lower self-noise than a small diaphragm mic -- and is chosen for situations where such characteristics are desirable, like recording vocals.

By all means use a LDC in this application if it gives you the sound you require... but don't fool yourself into thinking it somehow 'hears' more of the speaker cone than any other size of microphone. Only a wider polar pattern and/or greater distance between speaker cone and mic can achieve that.

Quote:

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This box that I want to build is to keep out stage noise from my condenser mic that will be 6-8inches from the cone.

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It sounds to me like you are planning to build a resonant cavity and stick a mic inside it, and that's never a good idea! If you heavily damp the internal surfaces of the box with foam or some other acoustic absorber you'll just have a heavily damped resonant cavity... which is still not a great idea! The resonance peak will depend on the dimensions of the box, obviously, but anything practical is inevitably going to have a nasty midrange peak that won't do the guitar tone any favours without serious EQ.

Live sound always involves compromises because of the inherent spill issues, and while a greater distance between mic and speaker cone might be desirable in the studio, it just isn't a practical option on stage in most cases, because minimising spill and maximising gain before feedback always trumps subtle tonal preferences.

Instead, The combination of placing mics with appropriate polar patterns, angled appropriately, and possibly with simple gobo screens is usually enough to achieve adequate separation from other instruments with acceptable tonality.

By all means build your box and try it... but I don't hold out much hope for an improvement in tonal quality. What you gain with greater speaker-mic distance will be completely overwhelmed by boxy colurations!

Hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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It sounds to me like you are planning to build a resonant cavity and stick a mic inside it, and that's never a good idea!

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Not in this application, no, but it *can* give some very interesting results with a room mic on drums in the studio, particularly if the cone is metal (I've used a waste paper basket for this! But I digress...

Hey Seablade, I am surprised that you say you haven't had spill problems with guitar mics. We obviously have different definitions of a loud guitarist. When there I have 4 vocal mics I find spill a big issue, when the player steps out of being in front of the mic. Recently taken to using Beta 57's (Tight pickup pattern)for this reason. Still this whole box idea seems a little crazy.
Had a win with a guitarist in his 50's last week, finally convinced him its better not to have your 2X12 combo on the ground firing into the back of his legs-and it only took 8 months!

Quote Falconhell:

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Hey Seablade, I am surprised that you say you haven't had spill problems with guitar mics. We obviously have different definitions of a loud guitarist. When there I have 4 vocal mics I find spill a big issue, when the player steps out of being in front of the mic. Recently taken to using Beta 57's (Tight pickup pattern)for this reason. Still this whole box idea seems a little crazy.

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You misunderstood. I don't have problems of spill into the GUITAR mics. Spill of guitars into vocal mics is almost always an issue, but generally lately I have worked with guitarists that are quite talented and know when to control their own levels so I haven't had to worry much except when I do the odd freelance one off gig for new bands.

Seablade

Ahhha gotcha Seablade, I always tell people the best way to get a good reputation as a sound guys is to only mix good bands on good PA's.

In a way its why its so hard to get a start at pro level.(most musos/punters cant tell if its the band or the PA or the engineer that sounds bad, so they blame the engineer-I never listen to their opinions, all that really counts IMHO is the bands girlfriends opinion, that usually who they ask....<sigh> )

I distinctly remember the night I realised this when doing a 4 band gig as a young engineer 30 years ago and the first 3 bands sounded crap and I was working my ass off to get a sound. Band four came on and WHAM instant sound goodness, with hardly anything changed!

Really good bands listen to each other and virtually mix themselves. There's not too many of those though! (:

Edited by Falconhell (23/05/12 02:05 AM)