Recording booth in the shed...

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OK, so I'm planning a bit of a home studio improvement project. Basically, our brick shed is currently split in two (the rabbit has one half), and it's separate from the house but fairly close. It's also shared with next door's shed.

My office is upstairs at the front of the house.

What I want to end up with is a soundproofed half of the shed (planning on using the room-in-a-room principle) where I can house my speaker cab(s) and mics while keeping external noise to a minimum, but keep the amp upstairs in my office, and run the mics into my interface - thus getting the best of all worlds.

So...problems I see with this:

1 - Interference in the mic leads (particularly since they'll be running in close proximity to the speaker leads).
2 - Looooong speaker leads (probably 20m) - is the extra resistance here going to be an issue with regard to the amp's output impedance?

Anything else I need to consider?
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  • ecc83ecc83 Frets: 1589

    "Anything else I need to consider?"

    ALMOST ANYTHING!

    TBH Digi' I can't really get my head around this? If the speakers are in the shed but the amp in the office, how do you control volume?

    Jusfort! Is the idea to use the shed as a giant "iso-cab"? Do you intend to sit in office with geetar and cans and widdle? If so, 20mtr speaker leads are not a problem. Bit naughty I know but I would use 2.5mm ring main cable and terminate in boxes with jacks. If you can find some cheap, "conduit" cable is available in various colours.

    Mic cables should not be a problem if the interface has good balanced inputs (good CMRR) but I certainly would not tie them to 20mtrs of high power speaker wire!

    Will/does the shed have any mains power in it?


    Dave.

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  • digitalscreamdigitalscream Frets: 26451
    ecc83 said:

    "Anything else I need to consider?"

    ALMOST ANYTHING!

    TBH Digi' I can't really get my head around this? If the speakers are in the shed but the amp in the office, how do you control volume?

    Jusfort! Is the idea to use the shed as a giant "iso-cab"? Do you intend to sit in office with geetar and cans and widdle? If so, 20mtr speaker leads are not a problem. Bit naughty I know but I would use 2.5mm ring main cable and terminate in boxes with jacks. If you can find some cheap, "conduit" cable is available in various colours.

    Mic cables should not be a problem if the interface has good balanced inputs (good CMRR) but I certainly would not tie them to 20mtrs of high power speaker wire!

    Will/does the shed have any mains power in it?


    Dave.

    Precisely - one big iso-cab, made of bricks ;) I'm going to be sitting in the office with the amp, my guitars, monitors, recording equipment etc.

    The rabbit's half of the shed has mains power, but the planned noisy end doesn't. Would be fairly trivial to put mains in that end too, but I can't see a reason to.

    So...do you think the mic cables are going to need a different route to the speaker cable, or is there a good way of shielding them within the same cable bundle?
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  • Drew_TNBDDrew_TNBD Frets: 22445
    Is it going to scare the rabbit into an early grave?
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  • digitalscreamdigitalscream Frets: 26451
    edited August 2014
    Drew_fx said:
    Is it going to scare the rabbit into an early grave?
    Not if the soundproofing's done right. However, it would mean one hell of a Christmas dinner...he's frickin' huge.
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  • GuyBodenGuyBoden Frets: 733
    edited August 2014
    So who will be listening to the speakers in the sound proofed shed, just the Rabbit or are they for recording?
    "Music makes the rules, music is not made from the rules."
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  • not_the_djnot_the_dj Frets: 7306
    GuyBoden said:
    So who will be listening to the speakers in the sound proofed shed, just the Rabbit or are they for recording?
    http://image.shutterstock.com/display_pic_with_logo/671002/671002,1312158150,1/stock-vector-rock-roll-rabbit-81991696.jpg
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  • digitalscreamdigitalscream Frets: 26451
    GuyBoden said:
    So who will be listening to the speakers in the sound proofed shed, just the Rabbit or are they for recording?
    Exactly - mics in front of the speaker cabs, running up to the recording interface in the office.
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  • randomhandclapsrandomhandclaps Frets: 20521
    edited August 2014

    TBH, unless it's a fairly large space it's going to be incredibly difficult to soundproof it (assuming that's part of the point), get your cabs in and get a decent sound.  The shed will already presumably have less inbuilt soundproofing than your house so volume becomes more of an issue unless you spend a fair bit righting it.  Also need to consider any damp issues, heating issues, which inside your house doesn't require.

    The thing is if you do not treat it then it isn't one big iso-cab made of bricks, it's one boxy, over reflective, too small a space which will not allow you to run anything any louder without disturbing the neighbourhood.  Also you have the issue of external noise leaking in - including the bunny.

    Have you ever used an ISO box before?  Personally I really do not like the sound they produce.  I do not know of anybody who records guitars regularly (or for a living) who has had one for more than a brief spell/fad.  There may be someone around here who does?

    Also how would you manage mic placement?  As you are recording original material and it's your own then no doubt you have a standard position, but I think once you surrender the ability to experiment with mic positions (especially with multiple guitar tracks) then you are both limiting yourself and making life harder come the mixing stage.

    I would borrow or hire an iso cab and compare it to your Eleven rack before spending out.

    My muse is not a horse and art is not a race.
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  • The rabbit is going to find a way to eat your amp.

    Or, you'll subject the rabbit to so much metal this will happen next time you open the doors to the shed.

    image
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  • ecc83ecc83 Frets: 1589

    Right. Well "shielding" is not the problem, the big, MFg magnetic field produced by the speaker current is!  No amount of copper shield or foil will stop that.

    One answer might be to use "start quad" mic cable but that is expensive, still depends how good the "balance" of the interface pres is and might not work anyway.

    Is it really a PITA to have two runs? Just 6inches would probably be enough spacing to avoid issues.

    One thought occurs. See if there is a local network rigger about and beg some foil shielded 4 pair network cable off him (FTP cable) . This stuff is cheap but has very tightly twisted pairs. The stuff is solid copper and you would need to terminate each end in a box with XLRs (standard 13A double outlet box takes 4 XLRs easily) . Cheap enough (might be free!) to bundle with the speakers and if it does not work, just leave in situ and do different. (could still use for a headphone link!)


    Dave.

    BTW, are the rabbits ok with this?!

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  • Danny1969Danny1969 Frets: 10356
    You don't need to worry about noise on a balanced mic cable, the common mode rejection on runs less than 50m is superb. 

    To record a guitar amp very loudly put it in a large dog crate covered in multiple layers of carpet, you can achieve about 70dB of attenuation between 120hz and 20Khz which should be plenty
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  • digitalscreamdigitalscream Frets: 26451
    Danny1969 said:
    You don't need to worry about noise on a balanced mic cable, the common mode rejection on runs less than 50m is superb. 

    To record a guitar amp very loudly put it in a large dog crate covered in multiple layers of carpet, you can achieve about 70dB of attenuation between 120hz and 20Khz which should be plenty
    Mate, you're a genius. I'd completely ignored the fact that we have a friggin' massive dog crate in the bedroom (the chihuahuas, apparently, need enough space for a great dane...). That reduces the whole problem to finding enough carpet/blankets to cover it, which is a much easier problem to solve. I can probably get a decent-sized bit of wood to put on the mattress on the bed and mount the whole thing on there too, so as to avoid floor vibrations.
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  • ecc83ecc83 Frets: 1589

    Noise on a mic line is one thing. An induced 20 amp mtrs when running alongside a speaker cable is quite another.

    The result will not be noise but at best crosstalk and at worse screaming instability.

    It is basic, studio techniques 101 to keep signal cables and high current AC cables as far apart as possible.


    Dave.

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  • Danny1969Danny1969 Frets: 10356
    ecc83 said:

    Noise on a mic line is one thing. An induced 20 amp mtrs when running alongside a speaker cable is quite another.

    The result will not be noise but at best crosstalk and at worse screaming instability.

    It is basic, studio techniques 101 to keep signal cables and high current AC cables as far apart as possible.


    Dave.

    Dave
    Where's the 20 amps coming from ? ..... he's gonna be tracking guitars not welding  a boat together :)
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  • octatonicoctatonic Frets: 33725
    edited August 2014
    It will work fine actually.
    Speaker cable can be really, really long with no tonal loss.
    Mic cables too.

    I used to have a speaker cab up in the loft and ran cables up there- this was pre Axe Fx though, no need for it now.

    You will need to treat the room, of course- you will get loads of ugly reflections with a brick building.
    Frame it up and put rockwool in the walls, double layer of plasterboard, treat the corners with bass traps etc.
    Will be great.

    And yes you do not want to run audio parallel to power.
    They should cross at 90 degrees only, ideally not at all.
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  • Danny1969Danny1969 Frets: 10356

    I have runs of 30 metres or more in my trunking of mains cable and balanced mic cable runs. Any noise as in 50hz hum is picked up equally on both the in phase and out phase .............. a balanced mic pre amplifies the difference between the 2 lines and any common mode signal (the hum) is rejected. 
    I used to design high quality mic pre amps, in the days when decent ones were unaffordable.  You can really take  liberties  with a low z balanced  cable run before any induced noise is actually greater than the pre amps own noise floor




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  • ecc83ecc83 Frets: 1589
    edited August 2014
    Danny1969 said:
    ecc83 said:

    Noise on a mic line is one thing. An induced 20 amp mtrs when running alongside a speaker cable is quite another.

    The result will not be noise but at best crosstalk and at worse screaming instability.

    It is basic, studio techniques 101 to keep signal cables and high current AC cables as far apart as possible.


    Dave.

    Dave
    Where's the 20 amps coming from ? ..... he's gonna be tracking guitars not welding  a boat together :)

    Speaker current 1 amp average? (and that's being conservative for an amp you WANT to overdrive but we don't know W or Z) .

    The 20 comes from the length of the cable. The term for transformers would be "Ampere Turns".

    Of course! It might well work! But the questions were mooted, I am just giving my best answer.

    Actually I am being very pessimistic. Because the speaker wires are not an open loop the radiated field will not be that strong. However, since the speaker wires are unlikely to be twisted they will radiate something (why we twist heater wires) and over that length of run I would expect trouble.

    Dave.

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  • digitalscreamdigitalscream Frets: 26451
    @Danny1969 - he means "amp metres", ie 20Am. I seem to recall that unit being something to do with magnetic field strength, which works in this context...
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  • Danny1969Danny1969 Frets: 10356
    edited August 2014
    Ah yes I get that now

    The thing is any induced hum would get transferred to both pins 2 and 3, the mic pre amp amplifies the difference between pins 2 and 3. If 20mv were to be transferred from cable to cable then the difference between 20mv and 20mv is 0V 

    That's the whole point of low z  balanced signals, being able to survive huge runs through noisy enviroments
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  • ecc83ecc83 Frets: 1589

    Yes Dan, I am fully aware of the theory and practice of balanced working.

    Indeed, we used to use twisted UNscreened table lamp chord for mics years ago. Mind you, there were no PMRs and only Batman had a mobile phone! Plus the mics were 15/30 Ohms.

    However, balanced amplifiers are not perfect, resistor tolerances mean you are unlikely to get a common mode rejection ratio of much better than 60dB and this will be worse for mic circuits because they are "low to lowish" impedance whereas the best figures are obtained when source Z is very low and sink Z very high.

    But a CMMR of 50-60dB (at LF) is more than good enough FOR ORDINARY SITUATIONS but tying a mic line to a speaker or power line is not ordinary and everybody and his uncle tells you not to do it!

    On the subject of "do not bother with this idea"? I cannot agree. We see FAR too few people having a go at DIY "studio" projects...Fork! The construction of a simple pot in tin attenuator is beyond the capability or "bother" of most of them!

    So, more power to the project Dig"! Just worried about dem rabbits!


    Dave.

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