FAQ

Simply put, ambisonics is a way of representing sound in full three dimensions. It captures audio as one omnidirectional signal and three figure of eight signals, with the microphones facing left/right, front/back and up/down.

It was a process invented in the 1970s, but has really become practical with low cost, simple digital systems like the Brahma microphone. It is more complex than using a single-point stereo microphone, but the results are very much more rewarding.

In conventional recordings, much of the quality of the recording is determined by what microphones you choose (Omni, cardioid, hypercardioid) and how and where you place them. This gets frozen once you record.

In an ambisonic recording, much of this is still in your control after the recording. You can create virtual microphones of different patterns, angle and rotate them.

You can set up with eight or more loudspeakers and accurately recreate the sound you heard at the performance. Set up four and hear it without the height element. If you already have a 5.1 system, you can synthesise a 5.1 recording that is actually better than you would get with a multimicrophone system.

 

There are actually two answers.

1) If you have purchased the Brahma-in-Zoom, or Large diaphragm version of Brahma and Zoom. You place the recorder/mic where you think the sound is good, check with headphones for the quality of the sound coming into the recorder, and press the record button.

You should first selected sampling rate and bit depth (48 k and 24 bit preferred) select the four channel mode. Make sure the M/S rear pair is set for equal gain. Just remember that ‘front’ of the recorder faces away from you when you can see the meters.

You will get two stereo recordings, called **XY and **MS. The XY is your top pair and MS is bottom. Together they make up the A-format recording. To convert to B-format you can use one of two free programs Brahmavolver or X-volver we provide. There is also the excellent VVencode, but you have to purchase it from VVmic.

2) If you have purchased the free-standing microphone, you first connect the DIN 12 to XLR splitter, and the four XLR connectors to your recorder. If you need longer distance you connect the extension cable first, and the splitter last.  Details are in the booklet we provide, but make sure the correct channels are connected, and the levels of the four channels are matched. (Zoom F8 and F4 make this easy, and the both have an ambisonic mode which allows monitoring in stereo while recording four channels of A-format.) 

• Remember
• 1) Raw recordings are called A-Format.
• 2) A-format files have to be encoded to B-Format using special “filters”
• and software like Brahmavolver, X volver and VVencode.
• 3) Ambisonic recordings are level sensitive and require all four channels to be recorded within 1/10th of a dB of each other.
• 4) Ambisonic recordings are, by nature “isotropic” or spherical. You can rotate your recording if you did it facing the wrong way.
• 5) Orientation of the microphone must be known to properly decode. How have you mounted the microphone ? Upright, facing the performance,  or even hanging downwards ? Your processing software needs to know to produce a correct B format file.
• 6) A good shockmount, and in outdoors a good windshield, are essential for good recordings

 

• Emmanuele Constantini, (www.ecsound.net) an early user of Brahma-in-Zoom, has published a set of how to articles on processing the recordings. Here they are:
• for Nuendo users 
• for Protools users 
• Reaper, using VVencode 
• Reaper, using X-Volver
• These have been written for Mac users, but they can be adapted for using with Windows computers

Yes you can. We  will store these files on the cloud, organised by microphone number, and will send them by email – the files are small. We provide a set on a small micro SD card, which contains software as well.

Initially ambisonic microphones – made by Calrec, called Soundfield microphones – were expensive because they were analog, which meant each microphone had to be trimmed to create  a B format signal.

In the last ten years, the technology has changed. The calibration is done in software, and the microphones themselves have become simple and light.

Apart from that, the pricing of each make of Ambisonic microphone is determined by the manufacturer. I built my first ambisonic microphones because I could not afford to buy the ones in the market. I want to keep the price as low as I can, so many people can buy these microphones and do these recordings.

There are currently three microphones with this level of quality and technology. In terms of price, Brahma comes out at the bottom , with Core Sound Tetramic in the middle and Sennheiser Ambeo on top. Brahma always comes with a calibration file – you don’t have to ask for it.

One way this has been possible is because we do not have a factory to make the parts. In Bangalore, it is possible to find small scale machine tool operators who will make the parts we need. The part that need the greatest precision – the tetrahedral frame for the four capsules, is printed in a  new high strength nylon, in a factory in the Netherlands.

Calibration of the microphones has also become easier, thanks to techniques that rely on quasi-anechoic methods. You need a high quality calibration standard, but do not require an anechoic chamber any more.

Precise calibration is the real secret of Brahma microphone quality. The process creates four virtual microphones of B format. It also aligns the frequency response of these four virtual microphones with the high quality measurement microphone used as reference.

Calibration method for Brahma microphones was developed in collaboration with Prof Angelo Farina and his team at the University of Parma. He has measured the prototypes at an anechoic chamber before developing the processes we are using, and has compared the results. This is an ongoing collaboration and future designs will also be submitted to Parma for evaluation.

The process of calibration generates a set of 2d and 3d graphics of the frequency response and directional properties of the four synthesised microphones. Errors in calibration are caught at this stage. If there are errors in these graphics the microphone is calibrated again.

Of the currently produced Ambisonic microphones, only CoreSound Tetramic and Brahma provide these calibration files. Several big name microphones are providing microphones without individual calibration, even when it has been clearly shown to be  an unsatisfactory method.

Brahma has been the name we have used for my ambisonic microphones for ten years now. A play on the fact that in Hinduism  Brahma is a four-headed god.

These microphones are hand produced, with a great deal of assistance from Meena. I design the microphones, the 3d parts needed for each microphone, the PCBs and the cabling systems. Meena does the soldering, from smt chips on the PCBs to capsules, and makes up the cables and connectors. There is a computer controlled infrared soldering station for the SMD assemblies.

The metal bodies are manufactured in small machine shops in Bangalore. The printed circuit boards are printed in a very modern facility in Gandhinagar, Gujarat. The tetrahedral frames are 3d printed in the Netherlands using a new and very strong nylon.  Microphone capsules, DIN and XLR connectors and high quality four channel cables are sourced from the US and China,

We match the capsules as sets of four. We check printed circuit boards as they are assembled. We then listen to each channel as it is wired up from capsule to the DIN connector. We then do a further test to verify that the right capsules are connecting to the right channels. It is only after this  that we calibrate the microphone, first measuring in quasi anechoic conditions in eight directions, and processing these measurements to create a set of FilterMatrix files that are unique to each microphone.

Brahma microphones are sold exclusively online. They are made to order, and very often, to meet specific customer needs. Which is why we usually require up to two week delivery time after payment.

Click here to order and tell us which microphone you want. Once you are satisfied with your choice of microphone and it’s availability is confirmed we’ll discuss payment modes and ship your mic to you anywhere in the world.

Our preferred payment method is Paypal. We will create a Paypal invoice for the price of the microphone plus shipping costs as soon we receive your request. We can also accept bank transfer, by arrangement.