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SE Electronics Reflexion Filter
Stand-mounted Acoustic Absorber

Paul White

SE Electronics portable screen is designed to turn any room into a vocal booth.
computer fans or spill from other performers. The Reflexion Filter can be fitted behind almost any microphone by means of the included stand clamp assembly, which also incorporates a support for your mic or shockmount. This means that you require only a single mic stand to hold both the Reflexion Filter and your microphone, but as the assembly can end up being quite heavy, it is important to set up the stand so that the weight is evenly distributed over its base. To achieve a worthwhile amount of acoustic absorption within a limited thickness, the Reflexion Filter comprises six main layers, contained within a punched-aluminium frame that allows sound waves to pass through it while adding some useful diffusion. Once it has passed through the holes in the aluminium, the sound encounters a layer of absorptive wool followed by a layer of aluminium foil, which absorbs more energy. Behind this is an air space, kept open by rods passing through the various layers, followed by a further layer of wool. Additionally, there are four pieces of specialist acoustic absorptive material attached to the inside face of the structure, which further absorb and diffuse sound. The stand assembly comprises a rather heavily engineered mic stand clamp that attaches by means of an adjustable block to the horizontal bar supporting the Reflexion Filter and the threaded post that holds the mic. This can be slid along the support and then clamped to provide plenty of flexibility for mic positioning. Although it does ensure a stable mounting, personally I felt this part of the design was slightly heavier than it needed to be.
he Reflexion Filter, from mic manufacturer SE Electronics, is a compact and portable acoustic absorber, designed primarily to reduce the amount of room ambience picked up by a microphone during recording. It may also assist a little in isolating the mic from other sound in the room, such as the noise from

An Absorbing Subject

If youve read any of our articles on recording in an untreated room, particularly vocals, youll probably know 38
www.soundonsound.com june 2006

SE REFLEXION FILTER

that we recommend always putting some absorbent material behind the singer. Most home-studio musicians record using cardioid-pattern mics, so most of what ends up in the mic is a combination of the direct sound from the singer plus whatever is reflected from the wall directly behind them. Why, then, would you want to put something like the Reflexion Filter behind the microphone? Firstly, if the singer works close to the Reflexion Filter, the sound will still be picked up as normal by the microphone but a lot less of the acoustic energy will be able to escape out into the room. This in turn reduces the energy of the reflected sound, which helps dry up the recording. Secondly, even cardioid mics pick up a significant amount of sound from the sides, so placing a cardioid mic within the curve of the Reflexion Filter will help keep out room reflections approaching from the side. Depending on how good, or otherwise, your room is, you may be able to make a perfectly acceptable vocal recording using just the Reflexion Filter to control the acoustic environment, but my own approach would be to combine the Reflexion Filter with some improvised absorption behind the singer which could be as simple as a suspended sleeping-bag or duvet. This would help absorb any of the voice that managed to reflect after getting past the filter and would also prevent sound sources elsewhere in the room reflecting from the wall into the live side of the microphone for example, computer fan and drive noise. With the Reflexion Filter screening off the rear and sides of the mic, this should lead to a significant improvement in both the acoustics and the amount of unwanted room
The Reflexion Filter is designed to attach to the same stand as your vocal mic.

SE Reflexion Filter 229

Impressive absorption capabilities. Affordable. Reduces off-axis sound pickup and may help reduce the amount of sound getting into the room to cause reflections in the first place.

Mounting hardware a little heavy and clunky.
noise entering the microphone. Another valuable application is to use the Reflexion Filter to de-sensitise the rear of a figure-of-eight microphone, such as one of the many ribbon mics now on the market. It could also be used to allow acoustic guitar recordings to be made more effectively using omni-pattern mics rather than cardioids, as these tend to produce a more open sound and they are less critical of positioning. According to the measurements made on behalf of the designers, the construction of the filter minimises any acoustic coloration, with variations of around only 1dB being typical. This is good, as the last thing you want is for an acoustic screen to significantly change the tonal character of your favourite microphone!
reduce room tone. For my money, it still produces the best results when used with some absorption behind the performer, which makes perfect sense as each tackles a different type of sound-leakage, so by combining them, you really can make great recordings in a typical bedroom studio. Whilst the Reflexion Filter scores in minimising the level of off-axis sound reaching the microphone, the duvet behind is most effective at preventing reflections reaching the front of the microphone. The optimum mic position relative to the filter is to get the capsule lined up with the centre of the filter and to have the mic

Alternatives

To date there are no direct alternatives to the Reflexion Filter. There are foam products available that clip behind the mic with a view to improving separation, but these arent really trying to do the same job, and their much lower mass makes them far less effective at low frequencies. In fact, the only real alternative is the improvised acoustic treatment we often recommend, where the singer is positioned with a V-shaped corner behind them made from two heavy duvets that absorb sound from the sides and reflections from the wall behind. Even then, the Reflexion Filter is likely to be better at reducing off-axis sound pickup, because of its proximity to the microphone.

Studio Trial

The Reflexion Filter absorbs acoustic energy with impressive effectiveness; you only have to stick your face up close to it and speak to hear that. On its own, it makes a valuable contribution to improving your recordings by reducing the amount of reflected sound getting into the microphone, and it can be used in different ways when recording instruments to improve separation and to

summary

Ironically, the Reflexion Filter makes the biggest difference in the worst rooms. And it can make a big difference, but any product like this can only achieve a certain amount; in my view, additional absorptive material (even if its only a duvet or heavy blanket) behind the singer should still be considered mandatory. If you combine the two approaches, you should be able to record adequately dry vocals in almost any environment.

sitting just within the curve of the filter, leaving plenty of space between it and the filter wall. If you place the mic further into the filter, the sound dries up more, but may change slightly in tonality. This can be used constructively when recording electric guitar cabs and suchlike, although in my experience, the amount of spill you get when close-miking guitar amps with a cardioid mic is negligible anyway. Perhaps if you were using a figure-of-eight mic, such as a ribbon model, at some distance from the cabinet, the use of the Reflexion Filter would make more sense. Exactly how much difference the filter makes rather depends on how well behaved your room is. If you already have some acoustic treatment in place or you have lots of soft furnishings, you may find that it makes less of a subjective difference than you might expect, but it becomes very obviously more effective in less friendly environments such as an untreated room or village hall. So long as you dont set back cardioid mics more than an inch or so from the mouth of the Reflexion Filter, the amount of coloration is minimal, but my tests with omni and figure-of-eight mics suggest that you need to take a little more care with the positioning of these. Putting
Second Opinion: Steve Levine
I took home a Reflexion Filter from this years Sounds Expo show, as I had been searching for just such a product for the last few months. I am in the middle of producing a new radio series about record producers for BBC Radio 2, and needed a way of turning my home-made vocal booth, which works really well for lead vocals, into a radio-style voiceover booth, to get that extra-close in your face radio voiceover sound. I was due to record the first of the voiceovers with Radio 2s Richard Allinson the next morning, as well as a few links from yours truly. The SE filter performed brilliantly if you move your head toward the filter panels whilst speaking, you can hear the immediate effect of drying out all of the room sound. The end result was exactly what I needed: dry, clean and in your face! My first lead vocal proved to be equally successful and the vocalist commented on how good he thought his voice sounded that day! Next up I thought I would try it on some guitar overdubs. I have one of the tiny Brian May Vox amps, which cuts really well in a track, especially if the other guitars all have a Marshall-based sound. Removing the screen from the standmount and placing it on the floor next to the front of amp, I used the Reflexion Filter as a mini-gobo, which made the guitar sound as if it was about half an inch from your face. Even when I added a touch of room reverb from one of my DM2000s plug-ins, the sound was exactly as you would imagine little amp, but now in a little room! In my view this product really makes it that bit easier to get a pro-studio sound at home. Steve Levine

the mic too far back will change the sound quite noticeably, although the reduction in spill and room tone is also far more significant. The figure-of-eight mic I used sounded best when placed a couple of inches in front of the filter opening. With cardioid mics, the Reflexion Filter seems able to achieve very little improvement in the rejection of fan noise from a computer at the other side of the
room, unless you have a further absorber of some kind directly behind the singer (to be fair, that isnt what it was designed to do), but with omnis and figure-of-eights, the drop in noise is quite noticeable.

Does It Really Work?

Those recording in less-than-ideal recording environments have been looking for a magic bullet quick fix for recording vocals since the term home recording came into being, and the SE Reflexion Filter represents a serious step in that direction. It cant keep all reflected sound out of the mic, as some will end up bouncing into the mics frontal axis from the wall behind the singer, but it certainly reduces this by minimising the amount of voice making it out into the room and by attenuating off-axis sounds. This could be particularly useful in a typical studio vocal booth where there is often a glass door directly behind the microphone. If rear-wall reflections are still a problem for you, some thick blankets, duvets or similar behind the singer should bring about the desired degree of improvement, and in combination with the Reflexion Filter should allow anyone to record clean vocals that are free from damaging room coloration. The price of the Reflexion Filter could actually be said to represent extremely good value when you consider that it might well make more difference to the subjective quality of your recordings than blowing an extra grand or two on more sophisticated mics and preamps!

information

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229 including VAT. Sonic Distribution +44 (0)1582 470260. +44 (0)1582 470269. sales@sonic-distribution.com www.sonic-distribution.com www.seelectronics.com
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This article was originally published in Sound On Sound magazine, June 2006 edition.
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The Reflexion Filter

Manual

Electronics

SE Electronics Instrument Reflexion Filter Manual
Thank you for purchasing the Reflexion Filter portable vocal booth. The main idea behind this product is to facilitate dry vocal recordings, in other words to achieve a vocal recording which has greatly reduced room ambience. Of course, the same Reflexion Filter can be used to achieve similar results whilst recording various live instruments, for isolating vocals in rehearsal studios and probably a host of things we havent thought of yet too! Wed be very interested to hear about novel applications from you, so please do contact us with your ideas, we are always glad to listen as it helps us improve and develop the product, and the information we can supply to other sE users. Your Reflexion Filter carries a 2 year manufacturing warranty, with free replacement of parts in case of mechanical failure due to faulty components. This warranty does not cover failures deemed to be as a result of misuse or abuse of the Reflexion Filter. If properly used and looked after, it should last a lifetime of recording use. You can extend your free 2 year warranty to three years by registering your product at www.seelectronics. com, so please visit the site and leave your details. You can also subscribe to the sE newsletter which we email out once every few months (dont worry, we wont pass your details on to anyone else, and we wont bombard you with SPAM!) One last thing please read this assembly manual to get the best results from your Reflexion Filter mic positioning, and the stand clamp assembly are critical to getting best results. Thank you again, and we look forward to hearing from you, Siwei Zou CEO sE Electronics International
Reflexion Filter Technical Manual
About Your Reflexion Filter
What is the Reflexion Filter?
The Reflexion Filter is basically a portable device for recording live sound sources with reduced room ambience. It is an advanced composite wall which is positioned behind any microphone by means of a variable position stand clamp assembly which ships with the product. The main function is to help obtain a dry vocal or instrument recording. This is especially useful in studios without proper acoustic treatment, but can also be used to help record takes in control rooms, where the performer also has to operate the recording device, or in rehearsal studios to reduce ambient noise.

The Technical Bit:

The Reflexion Filter has 6 main layers. Firstly, a strong layer of punched Aluminium which allows sound waves to pass through it, diffused, to a layer of absorptive wool. The sound waves then hit a layer of Aluminium foil which helps dissipate energy and break up the lower frequency wave-forms, and from here they hit an air space kept open by rods passing through the various layers. The air gap acts as an acoustic barrier. The sound waves then pass to a further layer of wool and then through an outer, punched, Aluminium wall which further serve to absorb then diffuse the remaining acoustic energy. The main absorber has 4 formed pieces of state-of-the-art specialist acoustic absorptive material attached to its face via the extended separation rods, which further serve to absorb and then diffuse the sound waves as they pass to the main filter. The stand assembly comprises a mic stand clamp fitting, which attaches by means of a vertical joint to the horizontal bar assembly onto which both the Reflexion Filter, and any standard fitting shock mount can be fixed. The microphone (in its shock mount) can then be moved both vertically and horizontally along the bar, and the Reflexion Filter itself can be moved vertically to obtain the optimum working position.

How does it work?

The various layers both absorb and diffuse the sound waves hitting them, so progressively less of the original source acoustic energy passes through each layer. This reduces the amount of energy hitting un-treated walls and other surfaces so there is less of the original source reflected back as unwanted room ambience to the mic. The Reflexion Filter also helps prevent any reflected sound reaching the back and sides of the mic. Its shape and size have been carefully tested to maximize absorption while keeping coloration down to only around 1dB, and leaving the microphones polar pattern unaffected.

In summary:

All in all, its a very clever and desirable piece of kit. It allows you to record vocals, guitars etc with a drier sound without having to have an acoustically treated room. Its portable. It uses state of the art materials. It works and its a fraction of the price of acoustically treating your studio environment!
Assembling Your Reflexion Filter

1.

Remove the Reflexion Filter and stand assembly unit from the packaging. Please keep the packaging safe to store the Reflexion Filter when not in use, or for transportation. It is robust, but parts may get damaged or lost in transit if not packaged properly. You should have the following parts Reflexion Filter (curved wall), stand assembly, support rod and spanner to fit support rod.
2. Fix the stand clamp assembly in place on the neck of your microphone stand a few inches below the point where the shock mount is usually fixed, or on the main vertical support strut of the stand. Youll see the assembly has a metal block with two large screws and a handle on it (one of the screws has a spring to help lock the assembly firmly onto the mic stand. Mic stand booms vary in diameter so youll need to experiment to get the clamp just right, but basically you need to set the screw with the spring so the two parts of the clamp sit parallel to each other, and then tighten the clamp using the larger screw.
Fix the support rod to the Reflexion Filter by screwing it into the socket on the bottom edge. Tighten the nut using the spanner supplied in the box.

4. 5.

Fix the support rod, with the attached Reflexion Filter, by pushing the support rod down into the socket on the stand clamp and tighten it in place with the metal handle on the block. You can now play with the positioning of the mic (both vertically and horizontally), and the height of the Reflexion Filter to get the optimum position for recording.

The Perfect Position For Your Reflexion Filter

The Perfect Position

The perfect position to achieve a dry recording is to place of the microphone so that the mic capsule sits centrally (both vertically and horizontally) in relation to the face of the Reflexion Filter (the face is the convex side with coloured panels). It is also important to have the mic capsule of the correct distance from the face of the Reflexion Filter. The mic capsule should sit roughly level with the front edges of the filter where the curved wall ends.
Having said all that, you CAN use the Reflexion Filter to achieve different effects by experimenting with positioning. Moving the mic into the face of the Reflexion Filter will give a darker and more dead sounding recording, but it will also affect the polar pattern response of the mic, so the mic will perform slightly differently. Again, in most cases this would be undesirable, but this method of use can create some cool results try micing an electric guitar cab this way, it can sound great! Moving the mic further away will mean there is more room ambience recorded with the dry source. Again, this is not usually desirable but can be used to get a specific room sound without the room taking over completely! The Reflexion Filter can be used not only for recording vocals and acoustic guitars etc, but as outlined above, you can experiment to find new applications like the guitar cab micing we suggested above. Wed love to hear from you with your own novel applications, so please contact us via the main web site, www.seelectronics.com, to let us know what you think of the product, and how you are using it. Thanks again, and we hope you enjoy the results of your new toy!

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