Aston Microphones Shield GN by Arthur Stone
The Shield GN is a vocal popshield with gooseneck and stand clamp from Aston Microphones Ltd.
A popshield prevents the moving air (pressure) from a vocal adversely affecting the mic capsule e.g. unpleasant harsh sss's or 'violent' plosive sounds, heard as pops; the low-frequency energy of plosives can overload the mic's input and this is worse for directional mics with a bass proximity effect; also the shield protects the mic from saliva.
In mechanical terms, the aim is to prevent plosive energy from distorting the fragile membrane in the mic capsule or electrical components. With sibilance the aim is to physically interrupt the frequency phasing in the sibilant region of the audio spectrum, although sibilance can distort the membrane too.
In addition to the advantages of traditional design and manufacture, Aston have utilised the capabilities of 'smart materials' to further improve the performance and protection of the mic.
The only potential downside of any popshield or suspension would be if it adversely affected the sound or left some undesirable character or artifacts on the recording. Does the Aston variant do this? Generally, larger diameter popshields have less impact as the frame is further away. Another known characteristic of a pop shield is high-frequency roll-off: 'Hard shields' can also resonate, and air meeting a barrier will create vortices and white noise. Does the filter leave some detectable trace or unwanted artefact? For example, the wrap-around design might create a semi-cavity for resonance at specific frequencies; or reflections off the frame or surface.
Word Up: The Shield GN is one of two new products from Aston (three if you include the Swift - the shockmount - which is available solo). It's often helpful to define the key names of new products.
Shield GN – the popshield and gooseneck with clamp
Swift – a universal quick clamp shockmount for a mic
SwiftShield - the popshield (Shield) and mics suspension (SwiftShock)
ShockStar - high-end smart material 'rubber band' suspension system
HexTech - stainless-steel metal sheet with laser-etched hexagons cut-outs, used for the popshield.
Just the types of words one would want to use a pop shield for!
First Take: I once read that placing a pencil vertically in front of the capsule (secured by a rubber band) would alleviate sss's; this didn't work for my Rode NT1A but, as an experiment, it taught me that objects could be placed in front of the capsule but that, generally, they only affected the sound in a subtle way – by disrupting the airstream/frequency of that energy, in this case the high-frequency phasing sound of sss's.
It always seemed counter-intuitive to place an object between mic and vocalist, as if the object would adversely affect the recording by muffling, splitting or misdirecting it. Of course, sound moves in (semi-) mysterious ways and thankfully, science can explain sonic phenomena and that knowledge can be built on to improve gear and techniques.
How does it work? Concentrated plosive energy is re-distributed across the surface of the Shield; the high-frequency phasing of sibilance is interrupted.
The filter is constructed of solid stainless steel sheet, with precise acid-etched hexagonal filter holes, and a glass-nylon trim frame which connects to the gooseneck (a flexible snake-like extension arm to clamp onto the mic stand). It presents a large surface area and curves around the mic ergonomically, so vocalist movement is not such an issue.
We can use linguistics, in a scientific sense, to look at the mechanical function of the products: products designed to alleviate or counter unwanted by-products of speech or song. We can look at the basic component sounds (phonemes), how the body produces them, then how they affect the audio recording. From there we can look at the specifics of how the popshield and suspension is operating.
HexTech and it's roots: The regular hexagon is a common shape in nature: from natural quartz crystal to bee hive honeycomb to Saturn's north pole. Historically, the hexagon grid was recognised as the most efficient form of material construction, using the least amount of perimeter material and excellent strength-to-weight ratio under compression. Maximum honey storage using the least amount of beeswax.
Hexagons and hexagonal geometry is ubiquitous and universal from the small to the large: snowflakes accrete as crystalline hexagonal formations bonded by electrostatic charge; or as ginormous intergalactic bubbles, man. Hexagons appear in lots of modern gear: from graphene sheets to computer fan screens to wind tunnels and turbines to space telescopes.
The use of the hexagon or 'HexTech' has two advantages in it's Shield application: first, the honeycomb design adds strength and lightness to the Shield's physical form; second, the hexagon is the preferred shape for wind tunnel filter design, mainly due to it's ability to distribute the load (air pressure/wind) across it's surface evenly...like soft honey in the comb or Saturn's stormy pole.
Once again, Aston's design and engineering is pushing the envelope.
Shield surface area
158 x 135 mm / 6.22 x 5.31 in
392 mm / 15.4 in
Price: £39 UK; Euro 45; $59.99 US
Why use a pop shield? To make recordings sound better by preventing two common problems: plosives and sibilance. Effectively these are two separate sonic problems, with different causes, that can be fixed using one device.
The plosive problem is that sudden burst of air pressure energy from the vocalist (e.g. p or b) and this is stressing the thin diaphragm membrane beyond its comfort zone even 'shorting' the circuit by touching the backplate in a condenser mic. Electrical components further down the line might not cope with the sudden electrical energy coming from the diaphragm.
The recovery time of the membrane's oscillation (from the plosive shock) can also funk up the later signal, even cross-modulation can occur. That type of thing should be fixed pre-recording, not post. Another type of plosive issue is when spit/projectile-saliva directly hits the diaphragm or basket.
The sss's or sibilance (caused by sibilant phonemes or 'sound units') is a different problem both mechanically and sonically; less energy than the plosive so less danger of diaphragm stress but the main problem is in the signal itself – less so in it's interaction with the mic. The energy in sss's can create a high-frequency phasing (around the frequency of a baby crying) which is not generally liked by listeners of music or media. Audio Kryptonite. Nail on blackboard. Overuse of Aphex Exciter. The sss's are also quite directional so good that the Shield is curved then!
IME the sibilant frequencies can travel a considerable distance (4-5 ft with the wizard's fire trick!) and contain a lot of energy – a sort of continuous plosive (sustained fricative) so ideally the popshield design will take this into account.
What advantage does Aston's Shield GN offer over traditional 'black-stocking' pop shields? It's 3D rather than 2D. Whereas a 120mm diameter traditional popshield has a surface are of approx. 11,300mm (150mm=17,670mm) the SwiftShield has a surface area of 21,330mm allowing greater coverage of the mic and allows the SwiftShield to be used off-axis which can be an important part of the vocalists technique especially with directional mics e.g. cardioid.
Another advantage is the efficiency of the HexTech in distributing unwanted vocal energy across the surface of the Shield which helps attenuate those plosives.
The Shield GN is much more robust and stylish than trad designs.
Couldn't I just buy similar components at the hardware store? Large bulldog clip; a small Mechano set...Granny's stockings...Heath-Robinson, etc.
Er, No. Hacks aside. It might work to some degree, perhaps well, but the Aston Shield GN is offering something generally more stable, reliable, professional-looking, aesthetically-pleasing (YMMV), and, a product better-suited, acoustically, to modern music production.
This is a big boy's filter – not something that sounds like old socks.
Protection: The Shield is easier to clean and offers the mic protection from saliva particles (which will be aerosol too). Apart from the corrosive affect of the salts in saliva it's important to be able to prevent a build-up of bacteria or viruses on the Shield itself (which is more difficult with the complex microstructure of a cloth material of traditional popshields). Still gonna need a toothbrush to do it properly though...clean all them holes! With the addition of silver or copper, steel can become antibacterial (viruses are another matter) but the Shield should still be cleaned regularly to prevent nasties and present a fresh interface for the vocalist/client.
You got the Look: Visual acuity is something to consider with popshields: the vocalist may need to look at lyrics or score or at a DAW/info screen. In a group or ensemble, a good line of sight to other participants and instruments, meters, dials, etc. is important. No-one wants to have to look around the popshield between lines to check the lyrics. In terms of video or photography a traditional popshield can be problematic as it obscures the talent and can cast a shadow.
The Aston Shield's bright neutrality is a good new take on a traditional problem. Due to the Shield curvature light usually passes through whatever the angle. The company logo is visible and whilst this is quite discreet it would be nice to have some options e.g. plain or Celtic knotwork or Paisley, or custom-design even at extra cost. This might well be impractical for supply-chain logistics & in that event it's a reasonably unobtrusive design as is.
In Use: The SwiftShield GN simply clamps to the mic stand and provides enough mounting stability and rigidity to position the shield as desired via the solid but flexible gooseneck. The distribution of weight with it's centre biased towards the mic stand and the light shield at the periphery is balanced and reassuring. The gooseneck is easier to manipulate when warmed by hand contact.
The clamp is more difficult to position on the curved surface of a mic stand; I found I needed to hold the clamp area whilst moving the filter end as it was liable to snap off the stand if twisted. Flat surfaces are no problem at all. Once the Shield GN is clamped on it stays secure and stable.
Candle in the Wind: In the video review, I tested the resistance of the Shield to air pressure by using a candle flame and I noticed that the flame reacts to the Shield presence more dynamically than the trad popshield but less than the original without a filter. The energy is tamed but the original dynamic character is still intact and I see that in the flame's profile.
In comparison the candle image is super-stable with the traditional filter. The conclusion then is that: no filter might overload the mic; the trad filter 'under-loads' it; and the Aston Shield strikes a balance.
Using the Shield made me aware of how the overload of no filter, and the muffling and inefficiency of a traditional filter, affects the mic adversely when under plosive energy – heard as a softening of the mid transient edge, like a sine tremolo as opposed to a choppy square wave. The Shield preserved the clear transient edge of the signal – sonic info that was lost without, either by the coupling and modulation of the diaphragm or the dynamic inefficiency and filtering of the trad popshield.
So the question is: when using a trad popshield what happens to the usable-level audio (vocal) that isn't excessively plosive or sibilant? It's filtered out by the inefficiency of the material. Particularly the good dynamics in the plosive regions.
Lost sonic info. It may never be heard but the Aston Shield assures it will be.
Audio tests: I repeated the phrase “I'm not a pheasant-plucker...” and a few key words containing plosives and fricatives, into a WeissKlang V13 cardioid mic with the Aston Shield, with the traditional popshield, and with none (as a control): I then repeated the test in another position in the room and added a 'sung vocal' – the Welsh national anthem. Unfortunately there is not enough room to include that audio here ; D
In the first test I preferred the sound of the traditional popshield as I heard a slightly-metallic sound in the sibilant region which was confirmed by the spectrogram analysis. I repeated this test due to the noise; I wanted to see if it was a fluke of positioning or a characteristic of the Aston Shield. I also wondered if the Aston logo (which is solid material marked out by the laser-etched 'hexacones') could be acting in a similar way to a pencil in front of the mic, in disrupting the airflow of unwanted sounds/sonic behaviour?
Looking at sound: In the first test the Aston Shield GN produced a 3.5 kHz peak not present in the original signal or the trad filter take. Sonically, to my ears, it didn't sound like an improvement over the original or trad filter; the Shield sounded slightly more metallic and the chart shows this as the 3.5 kHz peak (in faint blue).
I re-tested; same procedure, different position in room. The lower waveform is the average level and the upper the peaks. Not level-matched! Purple = Shield; Green=None.
Not much to say except the 3.5 kHz peak is less evident and, levels aside, the Shield appears to be smoothing the original signal but retaining the clarity and brightness.
To look at sibilance alone I focussed in on the word 'sis':
The same take with the RMS levels matched confirms this:
I've attached all the comparison charts below if you're interested in specifics and although the visuals are just a guide they do confirm the sonics in this case.
Mea Culpa: I made the mistake of comparing a traditional popshield with the Aston Shield when they are different: whereas the trad popshield filters out sound in the sibilant region it also colours the sound (cloth cap over ears) acting like a broadband EQ cut across the high mid frequencies...that's the sound I was used to. So when I first heard the Aston Shield (which doesn't filter but attenuates sibilance/plosives) I assumed it sounded awry and relatively metallic when, in fact, it was just representing the actual sound perfectly but without the plosives and sibilance of the source.
I made the mistake of judging the Aston Shield on what it was revealing about the source; the source being the vocal and room reflections/ambience and mic.
Some might accuse me of seeing the 'Emperors new clothes' - that really the Shield has a bright edge to it; but as anyone who progresses to 3-way high-end monitors or $1000 headphones notices, the increase in resolution and clarity reveals a faithful reproduction of the sound and that is what the Shield does. I think if you put this in front of a beautiful mic then you will hear that and not the filtering of a traditional popshield. The Shield is working more on the dynamics of plosives and sss's and not filtering them tonally.
So I think there is a cost to using the Aston Shield and that is it needs rear-protection from room echoes and a good quality mic and vocalist. If, like myself, you're looking for the Shield to filter out imperfections in mic/room or vocal then you'll be disappointed. This is pro gear.
An Inspector Calls: I may not be totally wrong in my insistence I can hear 'something' though. In the literature, wind scientists acknowledge the need for perfection in the honeycomb design, otherwise eddies and chaotic air turbulence can be created by the filter.
At first I considered the Aston logo on the Shield: it's form comes from the absence of hexagonal holes; could this be creating unwanted turbulence and sibilant artifacts? Earlier I mentioned the old-trick (or old wives tale) about placing a pencil in front of the mic; that didn't make much of a difference, but it helped. Perhaps Aston had added the logo to actually assist in improving the signal?
Attention then turned to the fine detail of the join between the Aston logo cut-out and where the hexagonal holes retained their grid pattern. I started with a magnifying glass and then a x20 field microscope.
Whilst at a macro (eye) level of resolution the acid-etched hexagonal holes appear smooth and neat, under magnification burrs and striations are clearly visible.
Before I continue I'll say that Aston gear is not different from other gear in this respect, in fact it's generally better with high-quality, engineering design and manufacture – at any price. Finish is generally functional with mass-produced goods: if it can't be seen by the eye (or felt by the finger) then why increase costs?
Hearing is different from sight as the scale of resolution is independent of a qualitative aesthetic decision (“it looks nice”). Does it sound nice? - whilst still being subjective, is independent of resolution.
Wind tunnel designers noted that the burrs and imperfections in the honeycomb grid can cause anomalies e.g. pressure differentials, eddies, turbulence, white noise, etc. (rather than the aim of a consistent distribution of sound as air pressure across surface area of the filter). I believe I can possibly hear imperfections caused by the join between the Aston logo and the hexagonal grid and the higher-resolution examination shows possible culprits – the rough details causing chaos.
I did consider further audio tests including shotgun-mic'ing different parts of the Shield (regular hexagonal grid, and imperfect join) and recording a test signal but that's beyond the scope of the review really. Still, I'd like to hear a design that left the hexagons intact.
My other concern was about the rear-reflections entering the internal arc of the Shield. Perhaps I shouldn't have rear-reflections in the first place? The Shield is just being honest in this sense, and with a halo-type filter to cover the rear there would be nothing to potentially (or philosophically) reflect; but without a halo I'm thinking that surely the internal arc of the filter will collect those rear room reflections and concentrate them directly into the mic like one of those death-ray mirror devices. I think I hear that anyway; just a bit too much emphasis in the sibilant region. In fairness, with time and experimentation, I think a sweet spot can be found.
Sound quality: 5/5 Finely-tuned professional instrument; needs careful set-up for optimum performance. Very good on plosives; OK with sss's. Non-colouring.
Ease-of-use 4/5 Care needed with placement and preventing rear reflections from entering the arc of the solid shield. Care needed when moving filter whilst the clamp is on a curved surface e.g. tubular mic stand.
Features: 5/5 The HexTech system, robustness and cleanable finish add to the value. The clamp is strong; the gooseneck has good balance between flexibility and stability. It looks pro (logo included) and I'm sure it's more inviting to a vocalist than granny's tights.
Bang-for-Buck: 5/5 It does what a popshield is supposed to do, very well...and it's pushing things a bit further. Forty quid for an effective, smart-looking popshield that'll last a lifetime probably? Perhaps not if you like the popshield to filter out stuff (although, in theory, you could put some material over the Shield if you like that sound) but the Shield will let you hear your vocals and gear as is.
Final thoughts: If there is harshness in your vocal, mic or gear you will be aware of it; the Shield does not muffle the signal.
The Aston Shield GN is an asset to recording (not a hindrance as traditional popshields can be); the difference being the stability with centre-of-gravity towards the stand and the HexTech performance. The Shield GN improved the recording by taming plosive/sibilant energy; the candle test confirms this. The audio test shows effectiveness in taming plosives; sibilance slightly less so but it is easier to fix post-recording.
Although the comparison chart shows that the Shield appeared to emphasize frequencies not present at source it didn't appear to affect the final sound adversely in further tests. This may have been due to a particular placement but it also could have been emphasized by the arc of the solid shield. Either way, as always, care with mic/source/room placement is advisable.
Apart from the 3D wrap-around design the Aston Shield doesn't innovate over traditional popshields but it does improve a classic design/function and make it robust & easy to maintain.
There's a lot of wisdom in buying once and buying well to last; this is what the Shield GN offers.
Links and credits:
Thanks to Voxengo for their wonderful SPAN analyser used in this review.
Phoneme - Wikipedia
Hexagon - Wikipedia
Honeycomb structure - Wikipedia
Photos used with permission of Aston Microphones Ltd; additional photos by Arthur Stone.
Wind Tunnel: NASA , Public Domain, File:Langley First Wind Tunnel - GPN-2000-001296.jpg - Wikimedia Commons
Computer fan: By DonES - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1088016
Honeycomb: By Merdal at Turkish Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=121469
Snowflake: By Thomas Bresson - Snow crystalsCC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=8805966
Snowflake (micrograph): By user:Brian0918 - Credit: Erbe, Pooley: USDA, ARS, EMU, Public Domain, https://commons.wikimedia.org/w/index.php?curid=493333
Saturn: By NASA/JPL-Caltech/Space Science Institute - http://www.nasa.gov/sites/default/fi...18274_full.jpg, Public Domain, https://commons.wikimedia.org/w/inde...curid=33952464