DIY Dummy Head?

Discussion in 'Location Recording' started by rfreez, Feb 15, 2007.

  1. rfreez

    rfreez Active Member

    Greetings!

    I wonder if anybody here has experimented with "Spaced Omni-HRTF-BAFFLED" microphone technique as demonstrated by http://www.sonicstudios.com

    i don't particularly like the sound samples on their site, but the idea of those mics on my spectacles for instant recording is very appealing. (Not for audiophile quality music recording of course, but it could work well for the acquisition of natural sounding sample content for experimental music).

    when i was checking out their stuff in this connection, i was surprised to find that their dummy head costs $1000 while the mics cost much less, and i'm thinking i could make this myself...

    lg_front.gif

    It really doesn't look like theres anything in there worth $1000! Can anyone offer me some tips on making my own dummy head?

    respect,
     
  2. Cucco

    Cucco Distinguished Member

    Hmmm... I agree. It doesn't look like a $1000 dummy head to me. In fact, it doesn't look like an effective dummy head.

    A true Binaural/HRTF function recording requires proper placement of the microphones within the ear canals/pinna to actually pick up the correct sound. What is in the picture above shows two (presumably) omni mics with a large, head-shaped baffle. This will most likely present an image with a pretty significant hole in the middle.

    I'm not sure what the material is, but if that's simply a soft covering over a hard head, I would also expect severe HF reflections to cause some pretty bad comb filtering.

    I have been thinking of making a dummy head using DPA 4061s mounted in (not on) a similar type of head. The head I was looking at is a ceramic/porcelain head with ears that are pretty close to anatomically correct. (Believe it or not, the head is available at Pier 1 Importers.)

    Good luck and keep us posted on your results.

    J.
     
  3. Cucco

    Cucco Distinguished Member

    :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

    Not quite what I had in mind...

    What I was looking at isn't on their web-page. It's a black porcelain head which is pretty accurately shaped and sized. The porcelain should be easy to drill. It's hollow inside (as is my head sometimes...) and is made up of roughly 3/4" porcelain around the outside. If I can take a picture of it, I will. (I have one, but it's currently being used in a scientific experiment to attempt to hack iris recognition systems).

    Cheers -

    J.
     
  4. BobRogers

    BobRogers Well-Known Member

    Yeah. Doing a search on "head" is probably a bad idea, especially if you are at work.

    I remember back in the the early '90's when my mother was trying to find a pair of pants for my 6'5" and very heavy father. I explained the wonders of internet search engines to her. She looked for "big men's pants." You can imagine the rest.
     
  5. Simmosonic

    Simmosonic Active Member

    I used to have a pair of their little mics, the sort that mount on the stems of a pair of glasses. I got them at least 10 years ago, so I am not sure what model they were, but they used PIP (Plug In Power), which is kind of like phantom power for kids.

    I made a few recordings with them; interesting...

    The best use of them I ever made was lending them to a friend who, in turn, used them with an MD recorder (it provided PIP) while travelling around Europe. He made quite an impressive recording on the French subway (I can't remember what they call it now, it is famous for always being on time, or never being on time, or something like that, perhaps it is famous for being famous?).

    When I actually needed them again to use for some stealth applications with my Sony WM-6DC Pro Walkman (a fantastic cassette recorder, by the way), he told me that his house had been broken into and they were one of the very few things stolen. VCR, DVD player, personal computers, mobile phones all seemed to remain in place.

    A few days later he left the country, apparently unable to cope with the loss. Baffling...


    Rather than a dummy head, how about a simple absorptive baffle a la Jecklin? There is some information about it here:

    http://www.josephson.com/tn5.html

    Apparently Jecklin himself updated the technique some time later. You can read about it here:

    http://en.wikipedia.org/wiki/Jecklin_Disk

    For a while now I've been contemplating building something like this using a pair of DPA 4061s (as Jeremy intends to use for his dummy head). I'd use the high sensitivity ones... I figure the whole thing could be built with those mics so that it can fold flat and be very easy to carry around - heck, I could roll it to my gigs. But seriously, I think it could be made so that the mic stems fold down and press into the absorption, then the whole thing could be slipped into a circular bag with a zipper to close it up. This would weigh very little and could easily be slipped into a daypack, taking up virtually no space, as a handy back-up pair.

    I could also detach the mics when required and use them for other things, including mounting them on the stems of glasses for stealth recording. This is very helpful if you're trying to record any environment that has people in it - in many cultures, people behave differently the moment they see a microphone, and that usually ruins it - they'll either go very quiet, or they'll start making noises near the microphone. (Yesterday I was trying to record the sounds of the thousands of people gathering at Pashupatinath, Nepal, to celebrate Shiva's birthday. Very frustrating, the recording is littered with numerous kids yelling "hello" or "testing" or bursting into song at the top of their voice as they pass the microphone.) The very presence of a visible microphone pollutes the purity you were trying to capture. This is where stealth comes in handy.

    DPA sell them in a reasonably priced and cool little stereo kit (SMK4061) that includes numerous instrument attachments, two boundary layer mounts, and more:

    http://www.dpamicrophones.com/module.php?MID=101&itemid=SMK4061&PID=&function=pdescription

    I had the pleasure of using one of these kits (along with some other mics) to record and reinforce a live performance of the fabulous Spanish mass 'Misa Criolla'. Very nice...
     
  6. Cucco

    Cucco Distinguished Member

    It's somewhat twistedly reassuring to know that it's not just America's children who are rude and obnoxious!

    I recently (last weekend) did a recording for a school ensemble. I had set my gefells on some mic stands a little into the hall but didn't fly them yet as I was going to have the engineer at the desk listen and tell me when he felt that they were at the right height.

    So...I'm back at the preamps firing up phantom power and I have the cans on and I hear....

    "THUMP, THUMP, THUMP, THUMP...Is this thing on? ARE YOU READY TO ROCK?!?!?!?! " and then some unbearable screaming.

    I run out to the front from backstage and see some 12 year old kid doing this to my gefells!!!!!!!! If I had a tazer, his ass would have been on the ground in a puddle of his own waste!

    Anywho...

    Michael -
    You should be fined $50 for posting that picture here!
     
  7. DavidSpearritt

    DavidSpearritt Well-Known Member

    Its not just children. Years ago when I was doing traffic noise measurements, where you stand on the side of the road looking like a real dork, with a SLM on a tripod, and the huge round windsock on it, truckers would see it and blast their horns for the duration of the passby, screwing up the statistical averages of the sample.
     
  8. Simmosonic

    Simmosonic Active Member

    !!!!!!!!!!!!!!!!!!
     
  9. Simmosonic

    Simmosonic Active Member

    Yikes! We can't blame them for technical ignorance, but who's going to pay for the damage?

    Many years ago I was mixing a rock band live and, unbeknownst to me, between songs the drummer had poured a large amount of water from his jug into the top of his floor tom, turning it into a small swimming pool. He ended the song with a big flam hit on the floor tom from the other ends of his sticks, causing the water to fly up everywhere, drowning the close-mike MD421 and even reaching over to the SM57 on the snare. It looked pretty good with the stage lighting, I'll admit. The mics kept working (as you'd expect from those models) but I dried them out anyway, and was thankful he didn't try that trick in the studio.

    He got this lamebrained idea from a filmclip of some rock band where the drummer hits the tom and water sprays off everywhere, glimmering in the spotlight.

    Another thing we can blame filmclips for is when rappers grab your precious U87 or similar and start treating it like a handheld mic while singing into the top end of it. [expletive deleted]

    Which brings us right back on topic: rappers and (some) drummers must be the world's true dummy heads.
     
  10. GuySonic

    GuySonic Guest

    Your right!

    The LiteGUY baffle does look simple, at least on the surface, but replicates the complex acoustic properties of 'water saturated flesh/skin' that's no simple or cheap trick.

    Living flesh (as opposed to mannequin head or a dried-out deadguy) absorbs virtually all audio frequencies with little or no reflection.

    Anything less HRTF accurate colors the microphone response to become a bit more of an 'effects' microphone, and less of a neutral 'virtual reality' type mic. Then the microphone is less consistent working fine sometimes, and not sounding so well at other times.

    There are actually TWO pages of sound samples. The second page contains only music split into sessions and live performance sections.
    I find most seem to prefer the musical content recordings on the second page verses the 1st page containing nature/ambient sounds.

    At http://www.sonicstudios.com/mp3_2slp.htm
     
  11. Simmosonic

    Simmosonic Active Member

    I suppose that's a truckers only chance to achieve 15 minutes of fame...

    10-4 rubber ducky.
     
  12. Simmosonic

    Simmosonic Active Member

    This is very interesting. What about diffraction?
     
  13. drumist69

    drumist69 Active Member

    I bet he got the idea from the J Geils Band video for "Centerfold". Toward the end, the drummer does a snare roll, and there's milk on his snare, and he plays it with, well, fish...yeah, not sticks, two fish...go figure! But hey, I can't speak for the rappers, since I'm not one, but I'm a drummer, and I respect gear. So am I an anomaly, or is this a broad-brush generalization? Who knows...but the best producers are drummers (at least in rock)> ANDY
     
  14. Simmosonic

    Simmosonic Active Member

    Hmmm, fish and milk? Not a good combination. Reminds me of a sketch from The Aunty Jack Show (probably an Australian oddity) where they were promoting "Captain Curd's fish milkshakes, breaming with bay-brine goodness".

    Actually, it's a cliched and tired broad-brush generalisation; as a writer, I ought to be ashamed of myself. And you're right, some of the best producers I've ever worked with were drummers and none of them ever drummed with fish (catchy stuff with plenty of hooks, but the scales are all wrong). I've modified the original post now...
     
  15. GuySonic

    GuySonic Guest

    Bound to be some diffraction as directional acoustic energy is being absorbed by shape and volume, but expect a whole lot less and of different characteristic than a less absorptive hard-head OR more transparent baffle of same size.

    Obviously real-person head acoustic interaction with sound is a complex mechanism considering frequency bandwidth and 3-D directions of propagation.

    Less obvious is the pressure signature of head's acoustic effect needs be miked with as small a low distortion, extended bandwidth capsule as practical (~.25 inch diaphragm, ~10-40,000 cycle bandwidth) avoiding the typical large mic body distortions on the HRTF sound-field and tonal coloration (non-flat & limited bandwidth) inherent with larger mics.

    Two known suitable mics for this type of HRTF recording are my own (Sonic Studios DSM) and Earthworks long time produced matched 30K/40K omni models.

    DPA 4060 series mics have very small size, but have proven NOT so suitable with very uneven frequency/phase characteristics mostly due to the capsule being buried inside and facing the wall of a brass tube for protection against actor's sweat and makeup.

    4060 models are excellent for their primary purpose as durable body/headworn dialog, and for recording special effects sounds for compositional-film work, but I found them way too colored sounding for HRTF accurate sound recording purposes where mic imposed 'effects' are undesirable.
     
  16. Simmosonic

    Simmosonic Active Member

    Thanks GuySonic, that is very interesting food for thought, but are you sure the DPA's capsule is facing the wall of the brass tube? That implies that all sound impinging upon the diaphragm is off-axis, but it appears as though the diaphragm can be seen directly from the end.

    I have some DPA4060s in my room, there are about seven of them flush-mounted around the perimeter of the Holophone H2 Pro that I'm currently using to make 5.1 surround recordings in the Himalayas. I'll have to take a close look tonight...

    P.S. Are we related? I'm Simmosonic, from the Australian branch of the 'sonic' family tree...
     
  17. GuySonic

    GuySonic Guest

    Yes, the rectangular capsule is INSIDE the mic tube body facing the wall!!

    Get a strong light and magnifying lens to look into the tube with screen cap removed to see the top edge of the capsule.

    Bought a whole bunch of these directly from DPA about 8 years ago to use for HRTF purpose. Quickly found need to REMOVE the tube from around the capsule to get excellent not-colored sound performance. Proved too much work for production, and with some wasted capsules. I was rather sad to have to pass on using these altogether for HRTF mics.

    I know Holophone uses 4060 series in a NON HRTF design. They seem most successful with this product through very smart persistent marketing, its ease of use, and suspect most users have more or less lack of discrimination ability for hearing mic coloration and inconsistent imaging.
     
  18. rfreez

    rfreez Active Member

    thanks GuySonic for joining in the discussion.

    I wonder if the sonic studios dsm mics use the famous panaasonic .25" capsule. I have a pair of Avensons which (i think) use the the panasonics and i can hear similarities in character, although the stereo separation in your samples is far better than what i've managed with the avensons in an approx 9" AB config... (maybe a jecklin disc as suggested will get me better separation?)

    as for the samples on your site, frankly, i prefer the outdoor/sfx samples to the music samples... in my limited experience, ultra sdc omnis tend to muddle up the low end in anything less than the most sympathetic (indoor) recording venues... perhaps the recordings were true to the event they captured, but the results were not engaging for me... i hope you are not offended by my candidness on this, its only my opinion, and i feel more musical results can be obtained from your mics than what is evident from the samples on your site.

    in any case i am strongly considering a pair of your dsms for my glasses, and will contact you soon through your site, regarding the same.

    respect,
     
  19. GuySonic

    GuySonic Guest

    Yes, I 'start' with several models of Panasonic capsules, but like Earthworks and maybe a few scarce others, there is a particular formula of modifications that make these something else entirely different.

    Most others who use these DO NOT MODIFY THEM IN ANY WAY, just mount the OEM capsule AS-IS in some manner which doesn't sound very good in my opinion. While most use a 6-12 step manufacturing process using these capsules, I use a process with over 30 steps usually taking several months to complete a run. Capsule matching is most precision available and most important for this type of stereo and multichannel mic.

    Sort of like Shelby using a stock Mustang to make the Mustang Cobra formula car. Knowing what it's like driving a the Ford Mustang will not aid in knowing much about the Cobra.

    Best music samples are usually in the 'sessions' section where conditions are more optimized verses limitations of recording positions/sound imposed during a live performance. However, there are exceptions in both cases.

    Outdoor recording is possible with simple 'eyeglasses' mounting, but only if slightest breezes are avoided, maybe using large 'quiet' golf-size umbrella to block air movement. Most find this less than satisfactory tact and use the windscreen headband configuration for most practical outdoor ambient recording in any conditions.
     

Share This Page