Tag Archives: sweet q

Surround recording techniques: Double M/S and IRT Cross

17 Jan

As part of the tasks to complete for our Digital Studio Production module at the Master in Audio Production in Salford University, we were asked to do two surround location recordings with portable equipment if possible. These recordings would be later mixed into 5.1 Surround format in the studios as part of our assessment… and it’s also good fun too!

The first recording I did in this fashion was not properly “on location” but in our University’s recording studios instead, using their equipment in full. It all happened before the Christmas break, when some of us Master fellows joined there to make a “jam session” (some noise with instruments  such as guitars, bongos, a battered drumset) and record the resulting soundscape. The goal was to set ourselves as far in the corners of the live room as possible so as to create a wide soundscape to recreate via surround recording techniques.

My setup of choice for this surround recording was the Double M/S technique. But not the usual one with two Mid microphones and one Side microphone for both of them, all sharing the same space in place. Instead of that, I decided to use Curt Wittig’s techniquue, shown in ‘Spatial Audio’ book by Francis Rumsey. In this one, two separated MS pairs of mics are used: one of them will give the front signal and the other one will record the rear signal.  According to Mr. Wittig, the rear MS pair should be placed back in the room at a distance from the front pair further than the room’s Critical Distance (DC).

Double MS Diagram

Double MS setup diagram (taken from “Spatial Audio” by Francis Rumsey)

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Do It Yourself audio: Jecklin/Schneider disc!

11 Jan

First of all, happy new year for everyone! Hope everything’s going fine for you. It has been hectic back in Spain for holidays those last weeks, seeing friends and enjoying time as much as I could but also working my ass off to prepare University assignments for the next 2 weeks. I guess it’s time to get to it…

One of the things that I had left for when I was back home was recording my fellow friends and bandmembers of Sweet Q playing in our rehearsal room. And not recording them in the usual way, but in Surround! I’ll have to bring that tracks back to Salford University’s studios and produce a 5.1 mix where I can recreate the room so a listener can feel like he or she is just there listening them play. More technical details on the recording process and technique will come in the next post, in a few days.

While I was doodling about which microphone technique to use for the surround recording, I came to remember something that I always wanted to try and do myself: construct a Jecklin disc with my own materials! Let’s go to the first stop: what’s a Jecklin disc?

As it name says, it is just a disc that is placed between two separated microphones to recreate a natural stereo image that is convincing both when listening in headphones and in loudspeakers. It does so because it is a baffle, made of acoustically absorbent material that creates a shadow area at high frequencies between those microphones, such in a way that recreates more or less accurately the amplitude, time-difference and frequency response between the ears. Low frequencies don’t represent an obstacle to the disc due to their large wavelengths so they reach both microphones more or less at the same time. Difference comes with high frequencies: the disc is an obstacle to them, so that the sound source becomes directional at that point and one of the pair of microphones will capture it before the sound wave arrives to the other one, giving us the idea of localization of the source. Continue reading