Reflection filters which are sometimes referred to as portable vocal booths or microphone isolation shields are the go-to solution for podcasters, singers, and voiceover artists when recording in a room that lacks ideal acoustic treatment. There are budget models on the market as well as premium versions, but they all aim to do the same thing – stop reflected soundwaves behind the microphone from bouncing back into it and causing unacceptable audio quality.
Are they worth the money though? How much of an improvement do they make vs no reflection filter at all and can they outperform a much cheaper DIY version?
Well, we wanted to answer those questions and we did so by going out and buying what many consider to be the ultimate reflection filter – the sE Electronics SPACE. We made the purchase specifically for this article and although a significant expense, felt that if this premium model didn’t perform as well as expected, or that there wasn’t a significant improvement over our DIY version then it’s unlikely that any of the budget options on the market would do so either.
We wanted to make the tests as controlled as possible so came up with the following scenarios to give a complete overview of how it performs.
- With a dynamic mic in a small room with a low ceiling and lots of surfaces to absorb sound waves (soft furnishings, a carpeted floor etc…)
- In the same room above but with a condenser microphone
- With a dynamic mic in a large room with a high ceiling. There are a lot of reflective surfaces including a large window, a wooden table, wooden flooring and some tiling
- Using the same room as above but with a condenser mic
No specialist acoustic treatment was installed in either room and the mic placement in relation to the reflection filter was the same each time as was the positioning of the shield its self inside the room. We then swapped out the SPACE for our DIY version which was made using things that can be found around the house as opposed to assembling something from shop-bought acoustic foam or similar.
We recorded audio samples of each so you can hear how each one sounds.
Before we get into the test though, let’s explore a bit more about reflection filters and how they work. This will give the whole thing a bit more context.
Table of Contents
What is a Reflection Filter?
A reflection filter helps to absorb soundwaves that would otherwise reflect and hit the rear of a microphone which can cause reverberation issues. They are usually made with acoustic foam but some models feature a multi-layered design incorporating different types of diffusers and absorbers.
Because of their portability, they’re popular with people who have a need for more of a portable studio and with those who record at home in a room that isn’t acoustically treated.
Although not a substitute for proper acoustic treatment, they can be very effective if used correctly in a suitable room and with a complimentary microphone.
Prices can vary hugely with them generally starting at the $40 mark and going up to $300+. What you’re paying for with a premium model is build quality, the materials used, and the R&D that’s gone into developing the product.
The materials used are important because if not selected carefully, they can actually cause the opposite effect of what was intended and introduce comb filtering, allowing a lot of low and mid-frequency waves back into the microphone.
How Reflection Filters Work
Reflection filters come in two main design types – an open-top design with an integrated microphone mount and then a less common box type design which the microphone simply sits inside. Both are designed to do the same fundamental thing which is to reduce reverberation by absorbing unwanted sound waves from entering the microphone, therefore improving audio quality.
The box-type design works more as an isolation shield as there’s only one open side. This can lead to a more ‘dead’ sound which can either be a good or a bad thing depending on what you’re looking to achieve. The image below shows an example of this design.
The more common open-top design is normally a U shape and they sit behind the mic with the microphone’s capsule typically sitting level with the left and right side of the filter as shown in the image below.
Because of the open nature of this design, some of the acoustic properties of the room can still be present which can in some cases improve the sound. Ultimately the quality of the final sound will be determined by a combination of the reflection filter and microphone used plus the room in which the audio is being recorded. The properties of the voice of the person speaking into the mic will also have an impact on how pleasing the recorded sound is.
Reflection filters do tend to color the sound somewhat but that can sometimes be a good thing.
What are Reflection Filters Used For?
Primarily, reflection filters are used for voice work. This includes voiceover artists, singers, and of course podcasters. They are however also used for recording some musical instruments.
In the video below, an acoustic guitar is being recorded with a microphone mounted to the sE Electronics SPACE which we’ve used for the testing in this piece.
The most common reason for using a reflection filter is because the room in which the recording is taking place is less than ideal from an acoustic and sound treatment perspective. That said, they’re definitely not a silver bullet as they work better at absorbing higher frequencies than those on the lower end of the scale and they only absorb sound waves directly behind the microphone.
When podcasting or performing any other type of voice recording, a cardioid pattern mic is normally used which means that the majority of the pickup happens in front of the mic and not behind it. This means that even with a reflection filter, sound waves bouncing back towards the mic from behind the performer can still be an issue. This is why some sound treatment is always recommended where possible but where it’s not, a duvet or acoustic blanket hung behind the person speaking into the mic can massively improve the sound quality.
Are Reflection Filters Necessary?
As mentioned above, there are some real advantages to using a reflection filter, especially in a room with no acoustic treatment. That said, a low sensitivity dynamic microphone can produce good results in larger rooms that are susceptible to echo. See our piece on the best microphones for untreated rooms to learn more.
Even with treatment, they can contribute to good sound. If you’re looking to reduce the reflection of those mid-high frequencies further, they are worth looking into and testing.
Do Reflection Filters Really Work?
Now the fun part, let’s get into the testing. As mentioned earlier, we’ve chosen the sE Electronics SPACE because it’s a high-end, premium model. Here’s the spec at a glance:
- 10-layer filter system which includes the following layers:
- Vertical bass trap pillar
- Punched aluminum diffusor
- Isolating air gap
- Acoustic grade wool absorber
- Recycled paper film
- Tensioned aluminum foil membrane diffusor
- Acoustic grade wool absorber
- Polycarbonate diffusor
- Asymmetric isolating air gaps
- Patented polyester acoustic fiberboard
- U shaped design
- 7 Vertical Bass Pillars
- Dimensions (WxHxD): 450 x 330 x 250mm
- Adjustable and lockable horizontally and vertically
- Can also be tilted at any angle
The video below shows how it goes together.
Before we even fitted any of the mics into the SPACE, we did some testing by talking in the middle of one of the test rooms away from the filter and then again with the filter in front of the face as if there was a microphone fitted. There was a noticeable difference between how ‘dead’ the sound was. An encouraging start. When performing the ‘clap test’ though to assess the natural reverberation of the room, we couldn’t hear a noticeable difference when stood away from the filter as opposed to performing the loud clap at the point at which the microphone would be fitted.
However, this test is about how it impacts the recorded voice so it was onto fitting the first microphone and recording in the first test room.
There’s just one audio track for each of the four scenarios and they all follow the same format:
- The bare microphone on a mic stand in the middle of the room
- The mic mounted to the sE SPACE
- The mic inside the DIY solution
The condenser mic used was the sE Electronics Z3300 A (as we were using an sE reflection filter, this seemed the most fitting of all the condensers we have….) and the dynamic mic used for the test was the Shure SM57. The image below shows them attached to the SPACE before plugging in the cables.
Here’s what the DIY version looks like – literally a couple of cushions stuffed inside a storage box. Please note that for the testing, a full-size microphone stand was used to match the SPACE which was on a stand. This ensured that all the recordings were made with the mic in the same position but it does mean that when using the DIY version, it sat just in front of the box as opposed to inside it as shown in this image.
As you’ll hear from the audio samples, the quality is less than perfect because we purposefully recorded them in rooms that were far from ideal for recording in to try and highlight the difference between a bare microphone and when a reflection filter is used.
No processing has been done to the audio clips other than normalizing them and a small amount of noise reduction applied. No compression has been added or EQ work has been done. As you can hear, the samples would certainly benefit from some de-essing work!
Test One – Dynamic Mic in a Small Room with More Absorptive Surfaces
As mentioned above, both rooms were far from ideal for recording in but of the two, this was much better as you might expect with it being smaller and containing more absorptive surfaces in the form of soft furnishings which will have helped to absorb some of the sound waves which were bouncing around the room.
In terms of reverberation, we expected the dynamic mic in this room to contain the least amount and that turned out to be the case. Did the reflection filter improve the sound? Yes, we think it did but it wasn’t hugely noticeable, again because reverberation was low anyway. The DIY version performed well too against the shop-bought version. The next scenario is more testing though – the same room but using a much more sensitive condenser mic.
Test Two – Condenser Mic in a Small Room with More Absorptive Surfaces
The reverberation levels in this turned out to be better than expected. Certainly more noticeable than when using the dynamic mic but not excessive.
The sE SPACE improved it slightly but in our opinion, the DIY version actually performed the best in this scenario.
Test Three – Dynamic Mic in a Large Room with Lots of Reflective Surfaces
If you were going to choose a room to record audio in, this definitely wouldn’t be it. It contains a wooden floor, a wooden table, cabinets, and some tiling (yes, it was a kitchen!) – reflective surfaces galore and it’s clear to hear from the audio samples that it’s much more echoey than the previous room.
In scenarios like this, we’d always choose a dynamic microphone over a condenser but as you can hear, it’s still not great. Both the shop-bought and DIY filters helped it out but it was far from perfect even with those in place.
Test Four – Condenser Mic in a Large Room with Lots of Reflective Surfaces
This was always going to be the most challenging setup in terms of the room and microphone combination. As you can hear, the sample just using the bare microphone contained a lot of reverberation. Interestingly though, this is where the shop-bought filter really shined – where it was needed the most. The DIY filter did improve things but the clear winner here is the sE SPACE.
With some other improvements such as a duvet hung behind the person who’s voice is being recorded, and finding the area of the room with the least echo, you could probably achieve usable audio when using the SPACE which is amazing considering how far away from ideal the room is for recording.
One thing we did notice in this test was the difference between the SPACE and the DIY filter when it came to midrange and upper mid frequencies. The SPACE seemed to reduce reverberation whilst retaining the natural sound of the microphone whereas the DIY solution seemed to almost amplify those mid and upper mid frequencies. This is likely to be down to the R&D that’s gone into the SPACE – the only R&D which went into our DIY version was finding the right sized box for the cushions we had!
With these tests, we aimed to answer the question are reflection filters worth it? We conclude that it depends. In scenario four where a sensitive condenser mic was being used in a large, echoey room then yes, if those are the conditions in which you’re recording then a reflection filter makes a lot of sense and in our opinion would be worth the investment.
When using a dynamic microphone in a room that is much better in terms of its size and the number of absorptive surfaces, the value you’d get from a reflection filter would be decreased.
We’ve proved that a DIY version is effective too. However, based on the frequency analysis above we’d say that if you did have the budget for a model like the SPACE then you will achieve a more natural sound from it at the same time as gaining the benefits of less reflection.
One final point to mention is that a reflection filter is not a silver bullet. One should always be used with other forms of treatment to achieve the best possible sound. Even if acoustically treating the room isn’t possible, hanging a duvet or acoustic blanket behind the person speaking into the microphone will absorb a lot of the soundwaves in front of the mic at the same time as the reflection filter deals with them from behind the mic.
So, will we be keeping the sE Electronics SPACE or will it be sold on to free up some budget for more products to test? In our case, we have a decent setup for recording already so it will be sold on. However, if we had less than ideal recording conditions then it would definitely be staying with us.