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Samar TF10 review - shockmount question

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Samar TF10 review - shockmount question

Postby blinddrew » Tue Dec 03, 2019 12:01 am

Just got to this bit of the magazine today, and looking at the picture of the shockmount, it looks like it moves in the wrong plane?
Surely you want your shock mount to have movement/elasticity in the plane of the diaphragm rather than perpendicular to it? Or is the shock mount really not working in the way that it looks like it does? :?:
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Re: Samar TF10 review - shockmount question

Postby Hugh Robjohns » Tue Dec 03, 2019 11:16 am

blinddrew wrote:Just got to this bit of the magazine today, and looking at the picture of the shockmount, it looks like it moves in the wrong plane?

It would appear so, yes.

Surely you want your shock mount to have movement/elasticity in the plane of the diaphragm rather than perpendicular to it?

Oriented in the same plane as the diaphragm's natural movement, yes. Absolutely.

The Rycote Invision shockmounts for small-diaphragm pencil mics demonstrate the principle very clearly. The idea is to provide maximum compliance in the direction in which the diaphragm normally moves, so that vibrations through the mount don't cause the diaphragm to move (and thus generate an unwanted output). Vertical or side-to-side movements won't (directly) cause the diaphragm to move in and out, and so won't generate an output. So the lyres on the InVision mount allow easy fore-aft movement, but are relatively stiff in the other planes.

Image

In the case of large diaphragm mics, the mounting options aren't as obvious, but again, the Rycote Studio InVision demonstrates one effective solution, with multiple lyres to provide the right degree of compliance in the right plane.

It would appear that the Samar mount a provides some level of up-down isolation -- a direction which shouldn't generate an output from the mic at all -- but not fore-aft movement, which will.

Or is the shock mount really not working in the way that it looks like it does? :?:

Only vibration test-bed measurements would identify whether it works effectively or not. I haven't tested or used it myself, so I can't comment on its actual effectiveness.

But by way of discussion around the topic, the other issue to bear in mind is that vibration has a habit of crossing the planes as it passes through a capsule's mounting arrangements. So a vertical input can often translate into a horizontal component (and vice versa). So if a mic happens to be sensitive to that kind of translation, introducing a shockmount that reduces vertical vibration might well appear to improve the situation to some extent... even though it's only dealing with a part of the problem.

In my (somewhat limited) experience, very few generic shock mounts provide any effective vibration isolation at all. And of those that do work as intended, their isolation frequency range is inherently restricted. Shock-mounting is an extremely difficult thing to do and the perfect shock-mount doesn't -- and probably couldn't -- exist! But there are a few that really are designed, engineered, and genuinely tested to ensure they work as intended.

I have tested several shock mount designs myself, and been present to observe more elaborate testing of many others on bespoke vibration test beds. It's actually quite shocking -- pun intended -- to see how poor some are, and some actually amplify the vibrational input in the audio range to quite frightening degrees!

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Re: Samar TF10 review - shockmount question

Postby Sam Inglis » Tue Dec 03, 2019 12:06 pm

Unfortunately, as I said in the review, I didn't have the shockmount to test. Mark is a smart designer, though, and I'll be interested to see what he has come up with.
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Re: Samar TF10 review - shockmount question

Postby blinddrew » Tue Dec 03, 2019 3:27 pm

Thanks Hugh, that was my understanding as well. Presumably the ones that made things worse have a mechanically resonant frequency (excuse the poor terminology - my engineering days were a looong time ago) in the audio range?
I do remember trying the 'SDC in elastic bands under the bridge arc' on my double bass once but it was horribly phasey as the mic moved around all over the shop. Fortunately I'd tried a more conventional approach at the same time.

Sam Inglis wrote:Mark is a smart designer, though, and I'll be interested to see what he has come up with.

This is what made me question things. If we were looking at a mass produced mic with an off-the-shelf elastic mount then you'd shrug it off. But when someone's got that level of knowledge on the mic, then surely they've not just gone off on one when designing the (plainly heavily engineered) shockmount. :)
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Re: Samar TF10 review - shockmount question

Postby Hugh Robjohns » Tue Dec 03, 2019 5:07 pm

blinddrew wrote:Presumably the ones that made things worse have a mechanically resonant frequency (excuse the poor terminology - my engineering days were a looong time ago) in the audio range?

Yes. Every mass-spring-mass system has a resonant frequency, and at that point vibrations will be amplified rather than suppressed. The effective vibration damping range starts about three octaves above that resonant frequency, so if you want good damping through the audio range from 20Hz the suspension's resonance has to be around 5Hz or so, and that requires a pretty floppy suspension... which is difficult to achieve with large and heavy mics if they are to remain in the right place - -and especially so for mics being waved around on a boom pole for film and TV use!

The (award-winning) designer of the Rycote Lyre system (who is now developing mic mounting and windshielding systems for a well-known Australian manufacturer... apparently!) wrote a description of the issues involved in a magazine I used to edit here (second page):

https://drive.google.com/file/d/0B6t-QlBod0gkUWg3TGhyQ0VFNjQ/view

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Re: Samar TF10 review - shockmount question

Postby blinddrew » Tue Dec 03, 2019 11:10 pm

Those pesky laws of physics getting in the way again! :thumbup:
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