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Best Position of Shotgun Mic in Blimp

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Hi everyone. This is my first post.

 

Which is the best axial position for a shotgun mic in a blimp?

Center the middle of the slotted part with the middle of the main body of the blimp (at least where dimensions allow it)?

IIRC Rycote recommends to not place the front of the mic further than the main body of the blimp (i.e. before the end covers).

Can the maybe about 1" wide annular [non perforated] part where the front end cover connects to the main body of the blimp cause audible degradation?

Does it matter if tube slots are left and right OR at top and bottom (i.e. rotating by 90°)?

Is it correct to assume that the front lyre doesn't have any negative influence if covering a very few slots (the rear lyre being usually clipped beyond the slotted part)?

 

I did some searches but was unable to find a definitive answer. Also pictures from manufacturers don't illustrate any common practice.

 

Any help would be welcome. Thanks everyone.

 

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Manufacturer photos are typically done to highlight what a product looks like, and don't necessarily reflect the way something will be used (Proof: I used to be a manufacturer and have taken loads of product photos). 

 

The optimal location of a mic in a windshield is having it be in the exact center of the windshield. The effectiveness of a windshield is the amount of dead air around the microphone, so you don't want it really far up in the windshield or really far back or too much off to one side. You want it smack dab in the middle. Covering up some of the tube slots isn't going to have a real big negative effect on the mic. 

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Thanks a lot for your answer.

 

I agree that product photos don't necessarily reflect the way they'll be optimally used in real life though in user manuals they should pay more attention to such details.

 

Do I understand correctly that the slotted tube part should be centered referring to "front/rear" of the blimp or rather the whole mic even if the non-slotted part of the cylinder varies depending on the model, also there's the XLR connector which takes some space?

 

Due to possible space restrictions I'm not sure if it's even possible to center the slotted part, but centering the mic body (not considering the cable XLR connector) is usually possible. "Left/right" centering (seen from above) and "horizontality" can usually not be adjusted as those dimensions are typically given by the geometry of the installed lyres.

 

I also wonder if Rycote lyres can end slightly permanently deformed if for example the mic is left inside the blimp for longer durations and especially if the blimp is laying on the side like in protective case (though I intend to remove the mic for storage). To me the Rycote lyre material looks like some specially formulated polymer (not elastomer, excepted for the inner co-moulded part which touches the mic) but I can't see if there will be permanent deformations or not.

 

Interestingly there are no low temperature restrictions mentioned, I mean quite below freezing as typically some plastics can become brittle or at least stiffer.

 

Again thanks for your help.

 

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3 hours ago, Reva said:

Does it matter if tube slots are left and right OR at top and bottom (i.e. rotating by 90°)?

Is it correct to assume that the front lyre doesn't have any negative influence if covering a very few slots (the rear lyre being usually clipped beyond the slotted part)?

 

My guess is that slots should be left right i.e. both sides facing windshield

and not top bottom as that would have bottom slots facing the windshield slot and mount

 

mike

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4 hours ago, Reva said:

Does it matter if tube slots are left and right OR at top and bottom (i.e. rotating by 90°)?

 

I could be wrong, but my logic has been that the interference tube slots should face left and right, since most noise would be coming from the sides when the mic is angled. In that position, the top of the mic just faces the sky/ceiling and the bottom faces the mount.

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I can’t imagine any mic manufacturer would place the interference tube slots just haphazardly around the mic‘s body, so covering some of them with a lyre will likely have a detrimental effect. The question is how much of that will you ever notice. Best practice would be to not cover any slots, but that can be tricky 

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IIRC in some video (from Rode or Rycote?) it was mentioned that if the lyre covers a few slots it wouldn't be problem (the lyres are narrow anyway).

Maybe seasoned experts would be able to notice a very small influence on higher frequencies as a lyre still represents a small obstruction (even if not covering a slot), I don't know.

Due to technical limitations, positioning the lyres only on the non-slotted end of the shotgun mic body leads to a weight load difference on the lyres which make longer tubes somewhat dropping toward the front. Also there would be an increased risk that the tube collides with the blimp body due to the long unsupported length. So basically I assume that it's more important to keep the axis horizontal (and also centered) than keeping the front lyre away from the interference tube, this also allows a better weight repartition between both lyres.

 

Again thanks for your replies.

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6 hours ago, Reva said:

 

Does it matter if tube slots are left and right OR at top and bottom (i.e. rotating by 90°)?

 

 

I was quite surprised when chopping to bits a 805 to find the mesh / slots had a somewhat skewed relationship to the actual interference tube hidden within ... being a tube with holes along its length (widening toward the trumpet).

 

That said, the 805 was designed to have the holes upward, and I have no reason to suspect the 'LR' grilles should be twisted since they are all designed to work in a free field with the obvious close echoes coming from below and the sparse unwanted separate noises (to reject through interference) coming from left, right, and sometimes above.

 

Jez

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The orientation fo the tube slots (left, right, up, down, horizontal, vertical) has no affect not he characteristics of the microphone. The symmetrical design was just for ease of manufacture, and could have had just as well been three rows of slots with the same area. In fact, a three row design may have been better, as it would have removed the question about how to orient them.

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Thanks for all replies.

Interestingly manufacturers don't seem to mention much about how to position a shotgun mic inside a blimp and for the reasons mentioned by dfisk one shouldn't rely too much on published pictures.

So basically the overall conclusion would be that the precision of the positioning of he mic inside the blimp is not that critical as it will only have a minor (if any audible?) influence.

Overall it's probably more important to carefully route the cable and tighten correctly end caps, sliding lyres and the locking screws in order to prevent handling noise.

I've noticed that Rode supplies some sort of "tooothed" spacing washer supposed to help reducing the mechanical play between the female XLR and the mic body but as I installed it it mainly pushed asymetrically the connector away (which ended with a slight angle) so I decided to remove that part as it seems to mainly stress the locking mechanism of the Neutrik cable connector. If required I'll rather try to wrap some gaffer tape but I couldn't hear noise specifically caused by the connector play.

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1 hour ago, Reva said:

Thanks for all replies.

Interestingly manufacturers don't seem to mention much about how to position a shotgun mic inside a blimp and for the reasons mentioned by dfisk one shouldn't rely too much on published pictures.

So basically the overall conclusion would be that the precision of the positioning of he mic inside the blimp is not that critical as it will only have a minor (if any audible?) influence.

Overall it's probably more important to carefully route the cable and tighten correctly end caps, sliding lyres and the locking screws in order to prevent handling noise.

I've noticed that Rode supplies some sort of "tooothed" spacing washer supposed to help reducing the mechanical play between the female XLR and the mic body but as I installed it it mainly pushed asymetrically the connector away (which ended with a slight angle) so I decided to remove that part as it seems to mainly stress the locking mechanism of the Neutrik cable connector. If required I'll rather try to wrap some gaffer tape but I couldn't hear noise specifically caused by the connector play.

 

I'll just add that not only is it not critical, it makes no difference. Position the mic so that it doesn't hit the front, back, or sides, is balanced in the suspension, and there is a good amount of slack in the internal cable.

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AFAIK, the Neutrik X series and the newer XX series female cable mount XLRs always came with an O-ring to keep out contaminants and to ensure a 'tight' mechanical fit, Unlike the old Switchcraft XLRs which were prone to rattle due to the loose fit... that and the (reversed thread) set screw and clamp retention screws would loosen and fall out.without some type of thread locking compound.. I still have a bunch of these with missing screws and no replacement parts are available AFAIK, For the past 20+ years I use Canare wtth Neutrik XLRs.

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I don't know the Switchcraft and Cannon XLR very well, as I'm in Switzerland Neutrik has always been quite popular (Neutrik is in Lichtenstein which is not Switzerland but they share the Swiss Franc, Swiss postal services and many other things, there are no customs nor border controls between those countries).

Referring to the female 3-pin XLR cable connector Neutrik NC3FXX-B of the Rode Blimp "Mk II" (with possibly an adapted cable gland as the short cable is very thin) and the Rode NTG3 which features a proprietary integrated male connector design (gold-plated pins in some insulation base, pin 1 (Ground) is slightly longer to always connect first and disconnect last), the outer part with the latching notch is machined in the body of the rear part of the mic) I tried with and without that blue "toothed" elastic spacer washer included with the NTG3 and didn't found it useful, it merely applies stress on the connector latch and tends to slightly harm axial alignement between the cable connector and the built-in mic connector. Also IMO there's not really a mechanical noise issue. As there's basically mainly the mass of the female XLR connector of the blimp, the friction of the connector parts seems sufficient to prevent mechanical noise.

Referrring to the male Switchcraft 3-pin XLR cable connector of the preinstalled (but easily replacable) cable assembly of the blimp, matching conditions with a Neutrik NC3FXX-B 3-pin female cable connector seem similar in terms of mechanical play. The issue is only that forces can be higher on the connector as this depends on how the cable is routed (for example at the top of the boom pole).
If directly holding the pistol grip by hand maybe it's worth using an elastic spacer (it's impossible to wrap gaffer tape around the connector because the male connector body ends nearly flush at the bottom of the grip) but if a boom pole is used, routing carefully the cable should allow to prevent mechanical noise at the connectors.
The comment about the spacer gasket is similar, I didn't notice a visible difference in mechanical play between the NTG3 - Neutrik XLR and between the Switchcraft XLR in the pistol grip and the Neutrik external cable XLR.

BTW The discussed female XLR Neutrik cable connector features a profiled annular EPDM gasket (it's not formally an O-ring as the cross-section isn't). As the groove for the gasket has a rectangular profile I suppose that the gasket could be replaced by some common O-ring of the right size, maybe also a combination of two O-rings or a anO-ring in addition to the existing gasket could be used to reduce mechanical play.
The corresponding male XLR connector has no sealing gasket. (There are also some protective caps for unused connectors but I never used them for XLR.)

Though I'm by far not experienced enough I believe that most handling noise comes from handling errors and possibly from the construction of the boom pole (specifically the absence of some sort of pre-loaded diameter tolerance compensation parts at the rear end of each tube of the telescope, I got the impression that while tube sections are locked without play, the rear of each section has as very slight radial play).

BTW I've no idea why Rode installed a Switchcraft cable XLR connector in the pistol grips and also one part of the pistol grip is designed in a way which makes the use of other connector types difficult because it is geometrically adapted to the profile of the cable gland.

That said, I didn't notice mechanical noise issues with the Rode Blimp "Mk II" if everything is assembled and tigthened carefully. Not tightening enough the lyre supports and/or the end screws of the rail assembly can easily lead to some mechanical noise.

If really required one could make a custom cable assembly with a regular mic cable ending with a very small highhly flexible shielded mic cable and remove the intermediate connector in the pistol grip. Doing so would be an advantage considering mechanical noise issues but OTOH there would be a fixed cable length requiring another intermediate XLR connector junction unless routing with a fixed length directly to the mixer/recorder.

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10 minutes ago, John Blankenship said:

I'm going to wait until the movie comes out.

 

 

Took me a moment to understand that comment, but now that I did: LOL!

 

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