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Author Topic: Better Blumlein Technique?  (Read 114 times)

klaus

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Better Blumlein Technique?
« on: March 12, 2019, 02:10:29 am »

I received this as an email, but, while the sender did not wish to post in a forum, he gave me permission to do so:

I have configured a Blumlein array with four KM84 mics.
As you can imagine, a figure 8 can be created with 2 cardioid mics with their axis oriented at 180 degrees to one another, their diaphragms aligned on the same plane, stacked one above the other, and the phase of the rearward facing mic flipped 180 degrees from the forward facing mic. Two such figure 8 pairs of KM84 mics are oriented 90 degrees from each other with the flipped phase facing rearward on both figure 8 pairs.

I would be grateful for your comments, and kindly correct my understanding of this mic arrangement where I may be mistaken:

1. I found that there is no audible effect due to shadowing as a result of stacking the mics participating in each figure 8 arrangement vertically, and oriented 180 degrees to each other, as one might believe would occur. Double blind listening trials of stacked and non stacked mic positions are not distinguishable.

2. The major advantages of this Blumlein array, as compared to a Blumlein array created from two figure 8 mics, is the choice of mics participating in the Blumlein array now includes stock cardioid mics, and control of volume and pan of each of the four lobes of the Blumlein sound field.
The trade-off when gain is unbalanced in the figure 8 members is a reduction of the null in the figure 8 component proportional to the gain delta in each figure 8 component. This trade-off results in a more omni sound field as the affected lobes become more cardioid as the gain delta increases within each figure figure 8 component.

3. If the phase of the rearward and forward facing mics are configured to be 0 degrees from each other (all four mics in phase with each other), then one is left with two pairs of XY coincident arrays, each array facing 180 degrees from one another. The in-phase sound field of each array is wider to capture a wider angle of sound in-phase at the expense of rejecting more sound from the sides of the Blumlein sound field.

The author asked me to add this link to a Blumlein patent: https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=394325A&KC=A&FT=D&ND=1&date=19330614&DB=&locale=en_EP
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com
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