THE HIDDEN ASSET OF FIGURE OF EIGHT MICS

Due to the inherent front to back ‘out of phase’ lobes of a figure of eight microphone, there is an ‘angle of placing’ advantage, in choosing to use a figure of eight mic in some circumstances. There is a ‘unique null’ between the two lobes, due to their inherent opposite phase.

Hence the mic can often be placed to favour some instruments and very effectively have the null avoiding the pickup of direct sound from instruments immediately below, or to the sides. For instance, over a choir at the back of an orchestra, and similarly where you have certain percussion instruments at the back of an orchestra and some focus is needed, without the upwards pointing euphoniums and tubas being added to the mix.

The writer finds that there is a further advantage in these circumstances, in that the rear lobe of the figure of eight adds to the ambience pickup from the focussed area, which is opposite to what a cardioid mic at the same spot, would be able to do!

It can sometimes be useful to use a figure of eight for a soloist out in front of an orchestra or a smaller ensemble. Without going in too close, you can often avoid getting too much pickup from the wider range of performers, to the sides of the soloist.

SHOT GUN MIC USES

The writer has this thing about ‘gobbing’ microphones in vocal situations. When overdubbing vocals to backing tracks, an Audio Technica 4073a short shot gun mic (Pic. One) is used for the vocalist. Set up around 12 inches from the singer, the capsule is obviously a little further away. You get a more natural sound than using the usual vocal cardioid right up close to the lips.

The usual variations in levels, with mic to mouth uses, do not occur, as the amount of change is such a small ratio of the distance to the shot gun’s capsule. However, an excellent Yamaha GC2020 compressor limiter is still used to ensure that the vocals do sit properly in the mix!

But it doesn’t end there. In the field of location Classical music recording, AT 4073a or their longer AT4071a shotguns are regularly used (Pic. Two). Interestingly the interference tube slots on these AT shotgun mics are not universally around the mics body. That then appears to be useful to angle them to make use of an apparent reduction of HF pickup from where the slots are.

The writer’s M&S activities have regularly involved the use of the shorter AT shotgun mentioned, as the Mid mic. It has certainly made it much easier to record duos, trios & quartets in the Wigmore Hall for instance, by just using the in-house height adjustable mic sling arrangement over the front row of the seats! In later times a Schoeps CMIT5U short shotgun had been used as the Mid mic (Pic. Three), with its greater uniformity of directionality, in the upper part of the audio frequency range.

In recording sessions for CD release with soloists involved with ensembles or orchestras, there is a lot to be said for having the vocal soloists agree to face the rest of the performers, from behind the conductor. With more than one soloist you space them apart and use separate shotguns at a distance of around 1.5 metres. The object is to be able to appropriately pan them and continually be able to balance them individually against the rest of the performers

For instance, at some Psappha sessions for a CD of ‘Mr Emmet Takes a Walk’ by Sir Peter Maxwell Davis, the three vital soloists were separately miked with AT4073a shotguns. The row of singers were facing the instrumentalists, around five metres back from behind the main M&S pair and the conductor, and able to see his arm waving!

The ‘psappha.com’ website has a ‘Watch & Listen’ section with two Video-ed Concerts in which the writer provided the mixed sound feeds to one of the camera’s operated by the Lancaster University team. There is ‘Trouble in Tahiti’ and ‘Light House’.

The latter one features a high tower, from where the singer soloists mainly performed. Sometimes the four AT shotgun mics can be seen ‘in shot!’. The shorter pair were aimed at the base area and the longer versions pointed up to the top of the tower. The voice balance and perspective seems to suit the sound from the un-miked Ensemble at the back of the stage, at this Lancaster University Concert Hall performance.

SPACED M&S PAIRS

If you have a wide orchestral layout, or a wide choir, not in the preferred semi-circle where a single pair would suit, or you are recording a wide staged drama production, try the use of two spaced apart M&S pairs of mics!

You have them at around 1/3rd and 2/3rd spacings along the front of the performance area. The crucial thing is that you angle them inwards to the front centre of the layout. For instance, with an orchestra or choir, you angle both pairs inwards symmetrically something like 10 to 30 degrees depending on the situation and how far back the pairs need to be.

Obviously, pointing them straight ahead would not work! What you get with this technique is the left half of the soundstage covered by the left output of the left pair and right half of the soundstage covered by the right output of the right pair. The ambience from behind the mic positions is also acquired.

Both pairs are conventionally decoded and mixed together. The Mid mic polar patterns probably need to be cardioid, soft cardioid or omni, as appropriate to venue characteristics. Soloists beside the conductor have been satisfactorily covered, however spot Shot Gun mics with are not ruled out! Possibly it can be helpful if the spaced out M&S pairs are moved a little in their positioning to result in a more appropriate near central placing of a front stage soloist’s sound?

Spaced M&S pairs have been used for sound feeds to camera for Black Swan Film & Video excellently filmed for DVDs of the National Children’s Orchestra concerts. It actually suits the visuals to not have a mic stand behind the conductor, albeit that the writers mic stands are still ‘annoyingly’ shiny silver and not non-reflective black!

Some stages are two restricted in space to get a mic stand directly behind the conductor, and slinging from above can be a nightmare! Covered in Paper No.2 is the hidden bonus available from this use of spaced apart pairs of M&S rigs, as it does also allow for 5.0 Surround play back! – see the comments in the earlier Paper No.2.

FIVE PIN XLR CONNECTORS

The writer has always made use of one cable for each stereo pair of mics in his inventory. So much easier to run just a single cable to the recorder, especially with the use of a M&S stereo pair. There is less chance of getting the Mid and Side feeds inverted, as on one occasion, for some amazing reason, and the writer did and not actually noticing it! None of us are infallible!

Overall screened, four core cabling is used with the essential use of the correct pair of wires in the twisted four, being chosen for each of the mics. A totally unacceptable amount of cross talk occurs, if the proper selection is not made.

You use the opposite pair of wires in the quad of four, for each of the mic feeds. The writer has not used what is specifically called a ‘Star Quad’ cable, and doesn’t seem to have found it to be really necessary, so far!

WIDENING NARROW CROSSED PAIR RECORDINGS

There is a processing system which can offer a stereo widening facility for a stereo feed, especially where a narrowness is noticed with closely spaced stereo pairs. The basis of it is to make use of the in-phase (Sum) and out-of-phase (Difference) components in the stereo they produce.

The writer noticed this when using a set of three shot gun mics to reach the back of the local Woburn Sands Band, which were augmented by a not very wide angled pair of cardioids in the same rig, pointing down at the front of the band. The rig was suspended over the front of the audience in MK’s Wavendon Theatre.

Its an well known old process, first of all obtaining the Sum and Difference signals from the initial ‘stereo’ obtained, and then treating it in the same way you decode the feeds from an M&S pair of mics! This way you have the ability to increase the stereo width you originally obtained.

In the writer’s case all five mics at the concert were mixed down to stereo at the concert. Possibly a greater choice might have been available had the five mics been separately recorded, in that the down ward facing pair of Sennheiser MKH40 mics, would be separately dealt with.

The panned mix of the three shotguns pointing towards the rear of the band, particularly for the soloists placed either stage right of left at the raised area occupied by the bands percussion section. Then the feeds, from the three rear-of-band facing long AT shotguns could have their mixed feed widened separately.

In the event dealing with the concert mix down obtained on the day did enhance the stereo result to the satisfaction of the Band members and especially that of Brass Band Conductor, Arranger and Composer, Len Jenkins, I am told …………….!

MICROPHONE STAND ISOLATION FROM WOOD FLOORS

On solid concrete floors or on the hard stone floors of older Churches, you don’t have a problem with mic stands relaying vibrations up the stand to sensitive microphones. There are numerous isolation mounts available for use in the Film and TV sound capture areas, but the writer has always used a means of initially isolating the mass of the mic stand from where its stands on many wooden floors venues..

Rectangular blocks of thick foam around at least seven inches square and two inches thick, with a central recess cut in it for the foot of the mic stand involved, are used in the writer’s case. The mass of the stand really isolates the mics at its top from floor induced vibrations. Many of the direct shock mount isolating mounts rely on the weight of the mics used and also there is usually a communication of the vibrations from the stand by the mic cabling itself.

In concert situations the foam blocks can be taped around their sides to physically relate them to the floor. If the audience seating arrangements use individually placed seating, as opposed to fixed pews in many churches, a space can be created around the mic stand area.

‘LINE SOURCE’ MICROPHONES?

There are ‘Line Source’ loudspeakers for PA use, where the vertical column array of transducers produces a wide horizontal spread of sound out towards the listening audience, with a significant reduction from above and below the direct feed, avoiding reflections from floors and ceilings.

Lets now imagine a microphone with a number of capsules in a column, which you use vertically and get a wide horizontal range of sound acquisition, with a very useful reduction of room sound from ceilings and floors.

They do exist and the writer knows of two such products. There is a Microtech Gefell KEM970 and a Pearl ELM, which the writer used a number of years ago. The Microtech Gefell uses eight cardioid capsules in its vertical column. The Pearl mic used their ‘unique’ rectangular cardioid capsules for its vertical line of capsules.

An assumed use is that these microphone arrays are just used in situations where you need to get a coverage from a wide layout of contributions from public speakers at conferences, etc. However the writer did use the Pearl product, very successfully in a M&S rig for three singers in a room, where it was essential to really reduce the pickup from the reflections from the room’s floor and ceiling. Another useful addition to possible recording techniques, for your thinking armoury?

BACKING TRACK MIXING

There was a school recording situation where a small choir of eight children, needed to be recorded singing to backing tracks. On another unrelated occasion, two soprano singers had backing tracks to be used for a demo recording.

Certainly for the first case, eight headphones were not available, apart from the Health & Safety aspect of having the performers tripping over the leads! So with the children in a semi circle in front of a M&S pair in a large room at their school, two small Dyer Cube powered speakers were placed together under the raised up mics.

As covered at the start of this paper, an asset of the figure of eight mic is the ‘null’, between the inherently ‘out of phase’ sound pickup lobes. So the close together speakers, placed below the mics, will be greatly ignored by the Side figure of eight and similarly by the use of a figure of eight Mid mic. In both of the writer’s sessions, it wasn’t necessary to go as far as using a Mid figure of eight, as the cardioid in use acquired the voice level balance adequately.

The four channels on an Edirol R44 recorder (Pic. Four) were used at the sessions, to separately recorded the decoded M&S mic feeds on tracks 1 & 2, with the stereo backing track feeds put down raw on to tracks 3 & 4, for post production mixing later.

The later church recording for the two sopranos with their backing tracks, the same setup and post production mixings were used, the standing distance from the mics determining the amount of overall ambience capture from the church acoustic. A degree of stereo church ambience also became added to the backing track, with the speakers angled outwards, the final backing track balance determined by the later mixing in for the raw feeds on 3 & 4 with the mainly voice feeds on 1 & 2.

MICS IN YOUR EARS

There can be occasions when you are asked to record in a situation where there is no choice but to be seated in the audience! Depending on if you can get a suitable sited seat and hopefully have no one bored and snoring near to you, apart from the nearby clapping definitely being unlikely controllable in level, you can operate in Binaural mode with a pair of electret mics in, or immediately near your ears, and powered by the Plug In power facility in SD recorders like the Olympus LS10 (Pic. Five).

Ages ago in the early Mini Disc days the writer used a pair of DPA4060 electrets mounted on a fold up head band originally made for ear phones. The ear phone units were removed and the same cabling used to feed the mics, unbalanced of course, to the recorder. These were the Sharp MDs which unusually have manual mic input control, unlike a certain other well known make!

A DIY box was made to hold the recorder on one’s knees, so that the metering could be easily seen and levels adjusted. To avoid any chance of the 3 pin mini jack input being moved, its input went to the back of the box to allow the use of a 3 pin ‘mini XLR’ socket, for the mic’s cable fitted with the male version.

The Olympus LS10 has now taken over this Binaural Stereo capture with a similar DIY box which also has a built-in battery powered headphone feed for subsequent listening. The low outputs of these recorders do not directly suit a couple of Sennheiser HD650 headphones used to judge the result in the concert interval. Great also to impress audience members during the interval!

The DPA mics, on the headband, are not fully in one’s ears, but the other mics the writer has also used are the Soundman OKM-11 pair of electrets, which do fit in ones ears, as they are inside some suitably shaped comfortable foam. The trick is to bring each cable feed out in front of your ears and go back over the top of the ears, and then down to the recorder. This greatly reduces the chance of having the mics ‘pop’ out from one’s ears.

At a concert where different performers had to take up various different positions you find you have a built-in facility, with the use of in-ear mics. You become a seated ‘mic stand’ which can be silently turned towards the changed sound source to balance the stereo acquired!

The word Binaural was used earlier, as the recordings do particularly suit listening on headphones. However loudspeaker playback is not seriously upset, especially if you angle the speakers inwards and then go and sit more in between them. Permission from the ‘Home Manager’ depending …....!