You may remember that back at the beginning of December last year we posted a story about helping to Kickstarter Project for a new low cost Ambisonics microphone from Brahma.  We promised to review the microphone and I recently received a package from India with a Brahma mic to review.

The microphone comes in a padded zip up case and then when you open it you see a lovely wooden box with the brand name inset into the lid in brass letters, a nice touch.

Ambisonics Is not New

Ambisonics has been around for a long time and the most well known name in Ambisonics is The Soundfield. Many years ago I recorded a demo CD for AMS, then owners of the Soundfield brand. The final recording we made was a choir singing an African song whilst dancing around the mic. At that time (1991) there was only one place where you could play it back and experience the full Ambisonic experience with height and that was the demo room in the AMS factory in Burnley, not 20 minutes drive for me from Manchester.

It is only now with the introduction of immersive sound formats like Auro 3D and Dolby Atmos that we can experience the full 3D audio that is in the Ambisonics format and so I am looking forward to a resurgance of Ambisonics as one native format to record immersive sound in.

A or B Format

A Format is essentially the output from each of the 4 microphones when they are arranged in a tetrahedral array like the Soundfield microphone. The 4 channels are often labelled LF (Left Front) RB ( Right Front), LB (Left Back) and RB (Right Back). This native A format is often converted into B Format labelled W, X, Y & Z as it becomes easier to manipulate the B Format to produce a wide range of mic layouts and the option to steer and zoom in post production. More recently Soundfield and others have produced lower cost solutions like the Soundfield SPS200 which produces an A Format output and they use the now free SurroundZone2 software plug-in to do away with the need to have an expensive hardware control box.

What do you get with the Brahma Mic?

The Brahma mic, like the Soundfield SPS200, is an A format microphone. The kit is made up of 3 parts.

1. The mic head in a spherical ball with an integral shock mount which connects to the Power box via a 5 pin XLR lead which isn’t supplied
2. The Power box which can power the mic with a PP3 battery or from phantom power from the mixer or recorder it is plugged into.
3. The breakout box which has 4 XLR tails labelled 1 to 4 and is connected to the Power box via an EtherCon connector and they do provide a lead for this in the kit.

When I first tried the Brahma mic I used my 5 pin XLR lead that I use for location recordings with my MS mice and is wired conventionally with pin 1 as the screen as XLRs are designed to connect pin 1 first. However when I tried it with the Brahma mic I got  a lot of hum, mainly on one channel but also on the other 3 channels too. The hum reduced slightly when I touched the power ox and that could me thinking and after some investigation it transpires that the 5 pin XLR on the review model has the screen on pin 3 of the 5 pin XLR which would explain the problem as the audio at this point is unbalanced. Once I plugged the power box directly into the microphone the hum went away so I continued the rest of my tests in this configuration. Of course having the power box connected direct to the mic reduces the effectiveness of the shock mount. That said it is only a basic shock mount and there is a lot of transmission through the stand into the mic even without the power box connected direct to the mic.  If I was going to buy a Brahma mic then I would look at replacing the shock mount with a Rycote Lyre mount.

Brahma do offer a version of the mic with a modified Zoom H2 recorder which makes for a very compact portable solution and well wrath considering if you plan to do a lot of location recording work with the Brahma mic.

The Test Kit

Brahma recommend that with the stand alone version, as they supplied for my review, you should use a recording system with digitally controlled mice preamps so that you can be sure that the mic preamp gains are matched accurately. Unfortunately I don’t own such a device so I used my Focusrite Octopre into my Apollo Twin interface and matched the gains as best I could. I then configured my laptop Pro Tools system to record the four A format outputs onto separate tracks.

The Tests

I set up the mic outside in our back garden and recorded 30 minutes of the coming and going at around 7:30am including a jumbo jet flying low overhead on its final approach into Manchester Airport as well as the bird life that enjoys our back garden. I also did a walk round test to identify the the different sides of the microphone. Brahma put a red mark on the ring of the basket to denote the front, and so in the tests I described this as north. I wanted to see how accurate the recording would play out on my 5.1 monitoring system in the studio. I used the fluffy cover that came with the mic, as you will see in the photos, but even though it was a very still day I could tell that it wasn’t going to be very good at handling the wind as I could hear some low end wind noise.

Convolving

Back in the studio I transferred the session onto my audio system and set about converting the A format files into a B format poly wav. Brahma provide tools to achieve this in two parts. 

1. BrahmaVolver Application
2. Unique Filter matrixes for each individual mic.

I downloaded the software and then installed the unique filter matrix files into the Filters folder so that the software would be able to compensate for the differences in this individual mic when undertaking the conversion from A Format to B Format using what they describe as a 4x4 filtering matrix. The BrahmaVolver software allows you to produce either a B Format file or a 5.1 file and offers some basic controls to configure the 5.1 version. 

I first tried the 5.1 output and then loaded it into my Pro Tools session but the results were disappointing, there was very little coming out of the surround channels.  So I reverted to my original plan to use the BrahmaVolver to produce a B Format poly wav and then use the excellent free Soundfield SurroundZone2 software to manipulate the B format into 5.1 in the Pro Tools session.

However I noticed that the SurroundZone2 software can handle both A and B format signals, so I routed the A format tracks through the SurroundZone2 plug-in and wow I had a great sounding surround experience. My walk round tests worked perfectly with my North ident coming firmly out of the centre channel and then as I turned to the right the East ident came nicely as a phantom image between the Front Right and Surround Right speakers, and the same experience was repeated as I walked around the mic. Next I played some of my back garden recording and it sounded brilliant, a lovely enveloping surround experience.

However I realised that in doing this A format direct to Surround using the Soundfield SurroundZone2 plug-in, I had bypassed the unique filter matrix field that the BrahmaVolver uses.  So I used the BrahmaVolver to process my 30 minute recording into a B format file, imported that onto a Quad track in Pro Tools and routed that through another instance of the free SuroundZone2 plug-in and compared the sound between the A format to 5.1 using just the SurroundZone2 plug-in and the A Format to B Format with the BrahmaVolver stand alone software, into the SurroundZone2 plug-in and the signal that had been through the BrahmaVolver was a much better, fuller sound with more low end and the top end was smoother too.

Conclusions

It is clearly a very good and cost effective solution and as a very early production model is a very usable mic for surround, ambisonics and immersive recording. It would be great to see how my recordings would play over an Auro 3D system but that would involve another trip to Belgium so that experience with have to wait for another day.

There are some shortcomings which I hope that they can resolve on the later production models and they are..

• The wiring configuration of the 5 pin XLR lead between the mic and power box
• The basic shock mount
• The poor performing wind gag cover.

If I were buying this I would consider using Rycote Lyre shock mount and a proper Rycote basket and fluffy cover for exterior recordings.

Update

on 2014-08-25 11:40 by Mike Thornton

Where Can I Buy The Brahma Ambisonics Microphone From?

Several people have ben asking where you can get the Brahma ambisonics mic from. So I asked Brahma and you can buy it from Embrace Cinema Gear.

The price for the stand alone mic as I used in the review is $899.

The “In Zoom” version will be available shortly but we don’t have a release date for it currently.