Mics with rectangular/triangular diaphragms

Discussion in 'Microphones (live or studio)' started by DonnyThompson, Apr 3, 2018.

  1. DonnyThompson

    DonnyThompson Distinguished Member

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    Hi guys...
    In this month's issue of ProSound News, two LDC mics were written about; one is AT's new 5047, and the other is the Ehrlund EHR.

    Both mics are cardioid only.

    The AT5047 uses four 2 micron thick diaphragms, the Ehrlund EHR uses one triangular diaphragm ( I did some research but couldn't find any info on the thickness of the diaphragm for this model).

    The AT5047 article is a review, written by Rob Tavaglione; the Ehrlund "review" isn't really a review, it's written by Goran Ehrlund, so it's more of a puff-piece, and not exactly what I would describe as "unbiased"... LOL.

    Ehrlund describes the reasoning behind the triangular shaped diaphragm - and I quote:

    "When sound impulses hit a round membrane with a long decay in rapid succession, the membrane cannot stabilize before the next impulse hits, and the impulses combine and build up, resulting in a "thick" or "muddy" sound. When those same impulses hit a triangular membrane, with a shorter decay, the membrane stabilizes four times faster, resulting in less build up of impulses. This produces a clearer sound and higher frequency response that is not possible with a round membrane."

    AT makes no mention of their design being based on this theory ( or fact?), instead saying that their 4 diaphragm design "sum together to create a very large surface area that accurately translates sound without the usual large diaphragm issues that include "sluggishness", poor transients, and harsh off-axis response...."

    FWIW, the AT 5047 retails at $3499 ( U.S.), while the Ehrlund's street price is around $1000, (give or take).
    I've never used a condenser mic (or any type of mic for that matter) that had a diaphragm shape other than circular - with the exception of ribbons or PZM's.
    I'd like to hear your thoughts on these manufacturer's descriptive claims. To be clear, I don't know what to believe; these claims could indeed be factual... I've no personal experience with them so I can't say either way.

    So, my learned colleagues... what do you think?

    ( sources: ProSound News, April 2018, AT review on page 28, Ehrlund "review" on page 27)
     
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  2. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    I'm no expert in microphone constructions but regardless of the shape and size of the capsule, they mostly all sound different. Many of them are not sounding well at all before the electric circuit does compensate for certain aspect of the capsule sound.

    For exemple, many U87 clone capsule are very bright and need some EQ circuit to make them silky smooth as they should sound.
    This was the case of my studio project C1.

    In the end, for my humble mind, what ever the shape, size and color, the sound the mic produce is far more important than how...
     
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  3. Boswell

    Boswell Moderator Distinguished Member

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    I've worked with the AT5040, which uses the same arrangement of four 12x21.2 mm elements, but they are connected a little differently in the AT5047. In the AT5040, the output of each element is buffered, with pairs of two elements connected in series, one pair being +ve connected and the other -ve connected to give nominal phase and antiphase outputs. These outputs directly feed the + and - outputs of the microphone, so the user's pre-amp does the summing of the two pairs of elements. In the AT5047, the first element of each pair is unbuffered, and the + and - pair outputs feed a transformer. The transformer effectively performs the summing, so the output is properly balanced (true phase and antiphase).

    The AT5040 is a very nice microphone for on-axis recording, and gives really excellent results for sources such as a single vocalist. However, sounds that are well off-axis hit the four diaphragms at different times, and these can sum to a phasey mess at high frequencies. Unlike a shotgun microphone, where there is a strong central lobe and high attenuation for off-lobe sounds, the AT5040 has a fairly conventional cardioid pattern for sensitivity. Experience shows that for constructive wave addition, you have to treat it as having a much tighter pattern and avoid off-axis sources, e.g. by using a vocal chamber. I haven't tried the AT5047, but I don't see it being any different in this respect.

    This is only a guess on my part, but it would not surprise me if customer and rep feedback to the AT development team was that the AT5040 was a great microphone, but performed better with some pre-amps than with others, these others being particularly those with no input transformer. The team may then have scratched their collective heads, and concluded that the best way to deal with the problem was to fit a transformer in the microphone - hence the AT5047.

    I have no experience with the Ehrlund microphone, but I can just about believe that a triangular diaphragm can sound different to a circular one.
     
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  4. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    Interesting !
     
  5. Davedog

    Davedog Distinguished Member

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    I also have a little experience with the AT 5040. But not the 5047. Interesting about the phasing. I was wondering about that but at that price it would seem to be a mic that would be chosen as a single source transducer. And this is what I have seen it used as. It is almost stunningly clear. The soundfield is huge and I could not differentiate the differences between the capture and the live sound off the floor. What you hear is what you get. I also have heard of the 5040 being a little persnickety with mic-pre choices but I cannot confirm nor deny this. I will say that every AT mic I have ever used/owned/heard seemed to have a particular mic pre topology that would be preferred....and not a general pattern by any means. An example would be my venerable first edition 4033. It seems to sound best through the Manley preamp. Not that it doesn't sound 'bad' through anything, but there comes out of it a bit more of a richness as well as fidelity.

    Of course it could just be the Manley......
     
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  6. audiokid

    audiokid Chris Staff

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    I have a 5047 in my locker but have not yet used it. When I do, I will be sure to respond to this post. :)
     
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  7. audiokid

    audiokid Chris Staff

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  8. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    WHAT ?? You spoiled little... Just kidding !! ;)
    I'd be curious to hear your super acoustic guitar through it...
     
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  9. audiokid

    audiokid Chris Staff

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    Lol!

    I’m working on that!
    I need new converters and time for myself so I can actually start working on my acoustic album. After my marriage dissolved I sold off a few things but kept the dream going. I’ve been acquiring mics which include the 5047. I can’t wait to sit down and start tracking that beautiful Taylor 914.
     
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  10. audiokid

    audiokid Chris Staff

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    This is kind of cool. Darryl Phinnessee Performs at the Audio Technica AT5047 Launch Party
    I would prefer a lot less poor sounding reverb though.

    He has amazing pitch control.

     
  11. audiokid

    audiokid Chris Staff

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    Wow... These sound glorious in this clip.
     
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  12. audiokid

    audiokid Chris Staff

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  13. audiokid

    audiokid Chris Staff

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  14. audiokid

    audiokid Chris Staff

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  15. rmburrow

    rmburrow Active Member

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    If you understand higher mathematics, get out the "Vibration and Sound" text by the late Philip Morse, or the Kinsler & Frye text, or any other physics text that analyses "modes of vibration" in detail. PML (Sweden) built a mic with a rectangular membrane. The movement of the membrane when subjected to incoming sound may be a few angstrom units at most, but the dynamics of each configuration (square, rectangular, triangular, circular) will probably differ somewhat...
     
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