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blumlein two mkh 30 on a parabola
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FREITOJOS
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#1
22nd January 2012
Old 22nd January 2012
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blumlein two mkh 30 on a parabola

Hello,
I have been using ms stereo mkh 30/40 in a parabola made by me with fiber glass.
I think the results are not so bad: 20110627T0700Z RIBEIRA ABAIXO , ORIOLO, ERITHACUS RUBECULA AND OTHERS by freitojos on SoundCloud - Create, record and share your sounds for free
I have been reading about blumlein and two bidirectional microphones coincident.
I don't like to listen with eadphones, now I am listen stereo with two speakers in 90º triangle, I have benn listen some blumlein recordings from some lables and I want to record blumlein in the field and reproduce at home in my speakers, but there is a problem, in the field there is no stage ( I am a naturecordist) and of corse there is no room.
If I put two fig 8 in a parabola the reflected sound is the front ( as a stage) and the two other lobes are the ambience, is it ok?
Does anybody knows about this situation
Thank you,
José
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22nd January 2012
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Your invention sounds good. Love to hear an indoor live band recording.
How far distance can it be positioned to record a stage performance?
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22nd January 2012
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How big is the dish and how do you gag the 8s ?
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23rd January 2012
Old 23rd January 2012
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More key details needed - e.g. where are your capsules sited w.r.t. the focus of the parabola?
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23rd January 2012
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Surflonge, I think a good distance because of the amplification in the parabola, I have some examples of birds wo sing loud that distorts if the gain is not too low for the ambience, so, a good distance.
Rolo 46 The dish is 60cm and the focus is in the limiting line of the dish, I am using sennheiser mkh 30/40 I want another mkh 30 to experiment blumlein in the dish.
Tom McC The dish is 60cm the focus is in the limite line 15cm +- and the capsules are in the focus the sennehisers are one above the other pointing to the dish and they can move a litle if needed to reach focus.
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23rd January 2012
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Rolo 46, to fix the 8s I made the support and use the manfroto 323 male piece to fix it in the Manfrotto female piece in the parabola, as I have done with mkh 30/40 wich are in an horizontal position pointing to the parabola, the two 8s must be in a vertical position pointing each other.
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23rd January 2012
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Hi!

I don't really understand how you want to use a pair of fig 8 mic's with a reflective surface close up but I'm afraid the results will not be very good.

A fig 8 mic is bidirectional with the front and back lobes in opposite polarity. If one lobe points to a close up reflective surface you will get cancellation which I assume is the opposite of what you are actually looking for.


/Peter
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23rd January 2012
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Audiop,
My hope is that the lobes that receive the reflected sound receive the sound 8db amplified, so the rear lobes receive the amplified sound, do I get cancellation?
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23rd January 2012
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Hi!

Yes, if the front lobe is pointing towards the actual sound source and the back lobe points to a reflective surface behind the mic, then yes, you will get cancellation.

An omni or cardioid works with baffles and paraboles but I don't see how a fig 8 would benefit from such a solution.


/Peter
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24th January 2012
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José, an intriguing sound clip with a remarkable spatial L-R spread in the sounds.

I also fear that changing to Blumlein would only be counter-productive, giving a veritable dog's dinner. The extra input of direct sounds vs reflected would cause lots of phase interference and cancellations, but also wreak havoc with the soundstage imaging. Moreover swapping in a 2nd Fig-8 might bring an additional susceptibility to wind noise, requiring a bulkier, better-gagged array that could block off more of the sound traffic heading for the reflector :-)

Can you or anyone else help me to an understanding of what the imaging actually is, when using solely the reflected sound or light of a parabolic? I'm familiar with the general principles: parallel on-axis rays brought to a focus; good capture of faint or distant sights & sounds (photos of stars; action sounds from football field touchline...) etc.

A dumb question:
- smooth a sheet of shiny aluminium, kitchen-foil over your parabola, to make a sort of giant shaving mirror
- place a small camera or cell-phone at the parabola focus, facing the foil and take a photo

What does this photo look like? I honestly don't really know...but would that not give some insights into the soundstage being "photographed".

Sorry I'm asking more questions than supplying help .
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24th January 2012
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Rolo 46 is offline
8s can be troublesome in the damp, even MKH radio frequency capsules, because both sides of the capsule are exposed to the elements.
They are difficult to gag and the whole rig will be bulky imho
To achieve your aim a large dish might be sufficient
But 2 omnis with a Jeklin Wall might be better than spaced 8s
What's wrong with the 30/40 combo ?
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24th January 2012
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Tom,
I am going to make the aluminium experience and post here.
You can see here one experience from nature recordist harjog: Yahoo! Groups
Rolo,
I am please with mkh 30/40 ms with apogee mini mp as preamp in the focus of a 60cm parabola but I wont to experimente Blumlein coincident 8s with and withou a parabola.
8s coincident is bulky as is ms in a parabola but the suport is already made for mkh 30's and it is all right in the parabola, I think I am going to rent one mkh 30 to experimente somehow and after that decide.
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