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Realistic Acoustic Guitar

Discussion in 'Guitars' started by IainDearg, Feb 7, 2005.

  1. IainDearg

    IainDearg Guest

    Great forum - spent a long while lurking and learning a lot. Especially how to spend a lot of money on top class audio recording software. :shock: I'll stick with Cubase in the interim, thanks :oops: Anyway, to my question:

    An acoustic guitar is about 3 feet wide with sound radiating from all points but loudest from the soundhole/bridge area and decreasing in volume from that point. Highest frequencies are at the furthest point from the soundhole, ie, the headstock, which is also the quietest. A project might be to emulate this image using a suitable recording technique to acheive believable reproduction from a quality (but not necessarily audiophile standard) hi-fi; loudspeakers notionally 6 feet apart, listener 6 feet away. Taking all this into account, how would you consider the following points if the purpose was to achieve a realistic, if not necessarily aescetically pleasing (or best), result?

    1. Would the guitar be considered a point source irrespective of the variance in the frequency distribution radiated?
    2. Would there be a de facto best mic placement strategy (preferably with two cardioid condensers) to achieve a 3 feet wide image from 6 feet apart speakers with realism?
    3. Would you equalise the left and right channels in terms of level, irrespective of the unequal loudness of the different 'ends' of the guitar, in order for the image to be centrally located between the speakers?

    Any thoughts on the above, or other hints, much appreciated.

    (BTW for my own purposes I'm restricted to a pair of KM 184s which I like a lot despite some opinions I've read!)

    Cheers, Dave
     
  2. FifthCircle

    FifthCircle Well-Known Member

    I usually co a classical guitar with a stereo pair. Think of it as a single instrument with a wide radiation pattern rather than something where you need zones of micing.

    My first choice for classical guitar is actually a mid-side pickup. These days, I will usually use a Royer SF-24 ribbon mic for this- the sound is glorious. I've also used Schoeps (both solid state and 221B tubes), and other mics as well.

    Obviously, you don't own any of these mics so that isn't an option (but I thought I'd throw it out as a suggestion as to what can sound good). With your 184's, I'd look at using an ORTF pickup. I actually mic differently for a session than I do for a live performance. In a live performance, I always use a little desk stand with a stereo bar (when needed) and have it below the instrument, but high enough to avoid floor reflections (sometimes a piece of foam beneath the mics helps here). For a session, I'll get the mics up off of the floor and on a larger stand usually level with or above the instrument.

    I place the pair starting about 2-1/2 feet out or so and adjust depending on what I hear. If it sounds too present, I move them back, too ambient, I move them forward... If it sounds too "woofy" and bass heavy, I move the pair towards the top end (neck) side of the instrument. If it is too "plucky" and harsh, I move it towards the low end.

    With those mics, you should be able to get a fine guitar sound. I wouldn't EQ each of them individually as you will end up doing more damage to the sound... Get the recording right out of the gate and you likely won't even need to touch the EQ. Another technique that you may see sometimes for recording guitar in a session situation comes from the pop world. Using the two mics seperated. One on the low end of the instrument and the other at about the 12th fret. Move them around to get the sound and pan hard left and right. It can be another very pleasing sound, but isn't very "classical" in nature.

    Experiment and let your ears be the guide.

    --Ben
     
  3. IainDearg

    IainDearg Guest

    Ben,

    Thanks for your advice. For the record, my experiences to date with the condensers are:

    X/Y: Has some realism but sounds constricted and feels uninvolving
    ORTF: Nice and airy with good width but maybe the image is a tad wide.
    Spaced pair: Non-starter for me: my guitar isn't 30' wide!

    I came across something called NOS which is apparantly capsules 30cm apart angled at 90 degrees. Also, DINN which is 23cm at 90 degrees. Well, I figured it was all up for grabs at that point, so I've found something with the capsules 17cm apart (my hat size :) ) angled at something like 75 degrees. I'll invent an acronym for it when I've got some time. :lol: . As for distance from the guitar, I lean towards (no pun intended) about a foot to 18" centred at the neck/body join.

    Again thanks for your input, Ben.
     
  4. FifthCircle

    FifthCircle Well-Known Member

    Well, 17 cm is the true distance for an ORTF pair. The angle being 110 degrees, though. If you move the mic back a bit, you'll get an image of the instrument as a whole rather than a portion of the instrument. Therefore, you can have the width and it will still seem realistic. When all you are capturing is the direct sound (which is all you'll get at 12-18"), small movements and distances/angles become magnified. When I have to get that close, I will often use omnidirectional mics as it will capture the ambience of the room a lot better. You can space in proportion to the size of the instrument and capture the sound well that way. I still wouldn't recommend a widely spaced cardiod pair, though.

    Be careful when making any spaced pair of mics too narrow- you end up with a "mono-ish" sound with phase issues. While X-Y may sound less open, you'll find that it will have far better mono phase compatability.

    --Ben
     
  5. DavidSpearritt

    DavidSpearritt Well-Known Member

    This is a bit off the mark. The only thing that radiates useful acoustic energy is the table or top of the guitar. The soundhole does not radiate useful sound and neither does the headstock.

    The soundhole is a helmholtz resonator neck, where a column of air is elastically pumping in and out acting as a spring at a very narrow frequency. Its like the bass port on a loudspeaker, there to help lift the more inefficient radiation performance of the guitar top at LF.

    Most luthiers tune this resonance to the first low G# above the bottom E string, and you can confirm this by detecting a bit of a wolf note there when you play this note or around this note. If you stick a mic near the sound hole you get a big woofy bassy awful sound centred on this low note. Not a good idea.

    The frets and headstock are a mechanical necessity and also not worth micing.

    The top is where your interest should be for quality sound. If you want bass you need to concentrate on the lower bouts where the longer wavelength wood vibrations are found, the upper bouts and the lower bouts all radiate HF sound.

    With the guitar its best to be at least the long dimension ~800mm away where the moving air from the radiating modes can mix together instead of being in the very near field where only some modes will predominate and the resulting sound will be uneven in the frequency domain.

    Get back 1m or so and then go back even further from there. Air is the best mixer and you will get highs and lows without wolf notes or scratchy mechanical non musical sounds.

    Most important, find someone who can play and in tune and find a decent room.

    Its only a point source very very far from the instrument, like 10m, or more accurately, a few lowest freq wavelengths away. At around 1m its not a point source so you need a coincindent mic technique to accurately get the image. Spaced mics will be OK but not nearly as good.

    See the other exciting (argumentative) thread in this forum on the classical guitar.
     
  6. sdelsolray

    sdelsolray Active Member

    I record solo fngerstyle acoustic guitar and classical guitar. The player is myself (I have a degree in classical guitar performance), and I record in my own home studio.

    After much research and trial, I've pretty much settled on using three mics to record, a pair of SDCs and one LDC for a center channel. The mic configurations vary, of course. Most often, I'll set the SDCs to XY or ORTF with the LDC is the same spot, which I guess is some sort of modified Decca tree. Moving the LDC around can capture what I'm looking for too. I'm usually out 24"-30" in my 18'x14'x8' room. Usually, I'll set another (4th) mic up (another LDC) to capture the center from another location. On mixdown, one or the other LDCs gets dropped from the final mix.

    For mics, I'm using a pair of Schoeps CMC6/MK4s and plan to add a pair of Microtech Gefell M295s for variety. For LDCs, I'm using a Microtech Gefell UMT800, CAD VX2 or ADK A-48, and plan to add another LDC and ribbon, again for center channel variety.

    I think it's important that the SDC pair have excellent off axis response. For the LDCs, having different characters helps. That mic is generally pointed on axis.

    Pres used are a Pendulum Audio MDP-1a, a John Hardy M-2 and/or a Pendulum Audio SPS-1.
     
  7. foldedpath

    foldedpath Guest

    Hi Ben,

    Are you able to use the SF-24 on classical guitar without EQ, or are you using some EQ boost in the upper frequencies to compensate for the mic’s upper end roll-off?

    I’ve been interested in the SF-12 and SF-24 (also the new AEA R88), but I’ve been afraid of losing too much high end… especially with an instrument like nylon string guitar, which can sound a bit dark to begin with (compared to steel string guitars and other acoustic instruments). On the other hand, the midrange on the demos I've heard sounds wonderful. I'm strongly tempted to try one of these mics. I'm not sure I have the room acoustics for it, but that's a separate issue. I was mainly curious about whether or not you find the mic needs any EQ boost in the highs, for something like classical guitar.

    Mike
     
  8. FifthCircle

    FifthCircle Well-Known Member

    I add a little bit to the top end, but really not much. I think the last time I used it, I added a couple dB at about 6 or 8KHz with a shelving EQ.

    --Ben
     
  9. Sunhill

    Sunhill Guest

    Hey!
    Im new to this forum, but I think this thread is just what I need :D
    I have read through all the above, but I must admitt that I didn't understand it all....

    So; here is my question;

    I have a Røde K2 tube, and two SM pro audio MC02 cardioid kondensers. The K2 is amped by a focusrite Voicemaster pro and sendt through my Motu 828mk2 to the PC (cubase sx2). The two MC02 goes direktly to the pc via the Motu....I also have the full waves diamond bundle.... My booth is small, but I have 30% covered with aralex panels! The floor is hard wood...
    So, in your opinion, what would be the best use of this equipment when recording acoustic guitar? I want a smooth, warm singer songwriter sound, with a natural hi fi 'ish touch....

    Any suggestions?

    I'll be most gratefull!

    Sunhill
     
  10. Midlandmorgan

    Midlandmorgan Active Member

    I suppose the most "realistic" sounds I've done guitar wise was by using a human Jecklin disc...

    Really...had a normal sized person sitting in front of the guitarist, facing them, 4-5 ft away, much like what you would find in an intimate setting....then took two small condensors at listener's ear level (both X and Y axes) aimed at the the 5th fret and the bridge of the guitar...

    Played back, no panning needed - no real EQ - it was recorded from a true listener's perspective. What I should have done was to suspend a ribbon over the listener's head with the null pointing at the instrument, to get the ambience of the room without any additional processing (M/S)...but that's another story.

    Or...place an omni at the listener's ear level...if you have a good one.

    I try to remember that the most realistic approach is often times not the best approach, though.

    (This seems like a pretty silly way to do things...but it did work well for me...)
     
  11. Sunhill

    Sunhill Guest

    Anyone?? I don't want to be a pain....but Im going to record very soon and Im looking to get all the best info I can get!

    Please help! :oops:



    Best regards Sunhill
     
  12. DavidSpearritt

    DavidSpearritt Well-Known Member

    I would set up your cardioids in ORTF about 1.5m from the guitar at soundhole height above the floor. Set up the tube on a stand above this at a height favouring the mouth of the singer but start with the same distance away, mixed centre and just "in" enough to fill in the centre of the ORTF image.
     
  13. Sunhill

    Sunhill Guest

    Thanx D!
    I'll try that... Any thoughts on panning, eq and reverbs for the later stages? My earlier recordings of acoustic guitar sound a bit hard and pickish... Mabye its my room, but honestly I cant afford any more auralex... :oops: Would a thick carpet on the floor help?

    Regards, Sunhill
     
  14. FifthCircle

    FifthCircle Well-Known Member

    If your recording is "hard and pickish," then try moving the microphones back a bit... As you move mics around (including out), one of the things you'll notice is the amount of production sound that you pick up.

    --Ben
     
  15. Sunhill

    Sunhill Guest

    I've tried to move mics around, but if I go to far away with the K2 I pick up too much of the room... and the room doesn't sound very nice! Hmmm... I guess somewhere in between then :lol:

    Thanx
    Sunhill
     
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