A few GOBO questions

[The Scum]

Genrrally, you want some mass in a gobo, so sound doesn't just go right through. Plywood or drywall are obvious choices, perhaps layered in combination.

Solid-core door slabs are an alternative, especially if you've got a used building material place where you can scavenge them for peanuts. They're going to be tucked away inside the thing, so they don't have to be beautiful.

Insulation on one or both sides helps kill reflections...wood slats with gaps between can make a nice half-dead/half-live option.

One other trick that I've used for one-room recordings is figure-8 mics. Put what you want to reject in the null. I've used them on overheads, with the bass amp in the null. Not total isolation, but much more usable than a similar setup with cardioids.

[jhbrandt]

Gobos with a heavy plywood or mdf core will attenuate the lower frequencies more than ones without. Depends on the Schroeder frequency of the room in which they are used... AT Schroeder freq, LF waves will flank around the gobos, but up to that point they will help to give you some isolation.

I think in a live recording situation using these baffles, balance between what the players want to hear and what you need for the recording will determine the amount of bleed that you will get - LF wise. Trim out some of the bass on the guitar amp and keep the bass guitar amp at a reasonable level, then you won't have so much low frequency bleed into the drum mics.

Also, since you are recording the amps with microphones (good idea), I would also recommend recording a DI directly from the guitar and the bass (instrument only) so that you can 're-amp' later.

Cheers,
John

[kevin206]

So last year I built these gobo / baffle things (which were totally just me sort of spit-balling something together). these were 10" deep, with a closed back, an air gap MDF wall, insulation, fabric cover.

http://messageboard.tapeop.com/viewtopi ... ht=#656922

So I checked out your Gobos and the linked jpg of the Foo drums. I like those! Looks like 4'x4'. Can you tell me just a little more about your construction? What lumber size did you use? 1"x10"? Did you build it just a bit large to hold a full size 2'x4' piece of insulation or did you trim that down to use your lumber a bit more efficiently? How did you attach your fabric? It looks like yours and the FF stapled just inside the frame as opposed to the face of the frame.

And when you recorded, did you put the Gobo right up next to the amp?

[kevin206]

Gobos with a heavy plywood or mdf core will attenuate the lower frequencies more than ones without.
I think in a live recording situation using these baffles, balance between what the players want to hear and what you need for the recording will determine the amount of bleed that you will get - LF wise. Trim out some of the bass on the guitar amp and keep the bass guitar amp at a reasonable level, then you won't have so much low frequency bleed into the drum mics.

Also, since you are recording the amps with microphones (good idea), I would also recommend recording a DI directly from the guitar and the bass (instrument only) so that you can 're-amp' later.

Cheers,
John

Would it matter the thickness of the core? I understand that I won't get total isolation, but I don't want sound shooting right through these things!

I've got a few headphone amps (I just need some extensions!), so it would be very possible for me to keep the amp volume low. Of course, my preference would be to track without the need for headphones. I'll need to figure out something for a scratch vocal. My interface has a "mix" knob to balance the inputs with the computer sounds. This is supposed to help with latency issues. Unfortunately, it monitors ALL of the inputs, so the drum mics would get monitored as well as the instrument mics. This could be problematic...but years ago, with live gigs, I would sometimes double mic so I had my own mic to send to a monitor mix board. This gave me independent control of the FOH mix. Where there's a will, there's a way!

[kevin206]

Insulation on one or both sides helps kill reflections...wood slats with gaps between can make a nice half-dead/half-live option.

I'm thinking that two soft sides may work best for me. Luckily, slats could be added later very easily. Have you had some good experiences with a slatted absorber? My floors are concrete and my walls are covered with 7/16" OSB. I would think that wooden slats may provide a more musical reflection than just any old hard surface.

I saw a YouTube video a few years ago in which a metal band was tracking drums for an album in their rehearsal space...looked like a large basement. I think that most of the drums were triggered and had mesh heads, but they were capturing a live snare and cymbals. They had hung wooden pallets on the walls all around the room. They claimed that it really made a noticeable improvement in the sound.

[jhbrandt]

Kevin,

Its all to do with density. 3/4" MDF would probably get you the 'max'.

Cheers,
John

[digitaldrummer]

Those are pretty nice looking. How well do they work? They look like they could work really well around a drum kit or a vocalist. I'll be using Roxul and it's not as rigid as 703. How did you get your cloth covering to look nice? I'll leave ratty stapled edges if I have to, but I would prefer that it look neat and clean.

they work pretty well for isolating the drums (cymbals), or to make the room sound smaller.... I have also put guitar amps behind them or can wrap them around a singer to get a little less room sound.

I like the idea of putting some mdf in the middle or even on one side, but I did not do that with these. I did build another one before these that was shorter but thicker, and did have plywood on one side, but I then attached 2" of OC703 to one side as well. The other side has chicken wire/wire fence inside with cloth over it. Inside I have rockwool. it's about 10" thick total and isolates pretty well too. I've used it around guitar and bass amps.

My studio is private (not commercial) so I went the cheap route and used black bed sheet cloth (cheaper than bulk cloth at Wally World). I'm not sure if these were flame retardant or not (have to check the labels...). I stapled it to one side, then flipped it over and put the OC703 in there. then I wrapped the cloth around and stapled the other side. Then I sandwiched another layer of the 1x6 on the outside. This gave it a more finished look, added some sturdiness, and I was able to stain the outer layer to make it look nicer (and it hides the staples).

Mike

[hunterchristy]

Can you tell me just a little more about your construction? What lumber size did you use? 1"x10"? Did you build it just a bit large to hold a full size 2'x4' piece of insulation or did you trim that down to use your lumber a bit more efficiently?

the outer frame pieces were 1x10. the back was, i believe 1" or maybe 3/4"...I honestly cannot remember. if looking at an xray from the side, its back, air gap, MDF, and then insulation. I made mine for ease of sawing, rather than sparring wood or insulation

How did you attach your fabric? It looks like yours and the FF stapled just inside the frame as opposed to the face of the frame.

Yeah, i just used a stable gun and went along the inside, rather than the face.

And when you recorded, did you put the Gobo right up next to the amp?

i did not. i had about a foot air gap between the amp and the gobo.

[JWL]

Agreed with JHBrandt on all his posts.... though regarding the comment about tiny rooms my take is that recording in a small room can be done, but will create technical problems likely to reveal themselves downstream in the mix (various peaks and nulls from comb filtering and a boxy sound, that is exaggerated once normal track compression is applied), such that some "repair work" will likely need to be done later.

Put another way, which problems do you want to deal with down the road? Bleed between instruments, or boxy, resonant tracks that need fixing?

In general, if you build a gobo that is absorptive, has a barrier inside to block sound, and are careful with mic technique (use the mic nulls to your advantage) you can get surprisingly good isolation when recording in one big room.

For more detail on my take on recording in tiny rooms, see:
http://realtraps.com/art_booth.htm

[jhbrandt]

....Put another way, which problems do you want to deal with down the road? Bleed between instruments, or boxy, resonant tracks that need fixing?
http://realtraps.com/art_booth.htm

+1
- John

[kevin206]

For more detail on my take on recording in tiny rooms, see:
http://realtraps.com/art_booth.htm

Thanks for that link. I've read it before, but it's been a while and my memory isn't as good as it could be! I think that I've made the right decision by keeping a large room. I've got a few ideas now about what I may be looking for. I think that I may want to build some large panels for around the drums with only insulation to tame down some reflections. I'm thinking about some taller, possibly stand mounted, insulation only panels to surround the vocalist to keep out some room sound. My original Gobo idea to surround the amps has changed a bit. I'm still planning on a gobo, but I think I can get by with a little less than what I originally thought.