Re-amping, Part III • Mixing with a Speaker & 2 x mics

by Nikolay Georgiev on December 26, 2010

IV. Mixing without faders or pan pots.

The idea of my experiment was that if done sucessfuly not additional mixing should be needed post-recording.The idea of mixing with a speaker and a pair of mics came after I went back to a track recorded more than 5 years ago. The subject to the experiment consisted mainly of acoustic instruments: two solo classical guitars, two acoustic and two classical rhythm guitars, two acoustic slide guitars, electric bass and an electric solo bass. I had to revive the composition, but there was a problem – the original recording was done in a typical procet studio style – amateur equipment and a room with dreadful acoustics. If I remember well, the recording chain consisted in a pair of SE4 mics and an M-box2 for all acoustic instruments, and a cheep passive DI for the bass. A setup like this one, in such space, couldn’t result in anything else but an unnatural, suffocated, small and harsh recording. As the track had great musical potential, I wanted to do it all over again. The only problem was that its player and composer – Stanislav Hvartchilkov – still has nightmares from the hours of painstaking work in which he overdubbed the rhythm guitars. Those were 8 minute long constant right hand tremolo parts, each one of which was playing  only a single note of the harmony at a time. They were not only physically very difficult to play, but the parts were full of rapid dynamic changes and tempo variations. I had to save them.

Trying all the usual tricks with some of the most advanced plug-ins didn’t help at all. Even the best chef won’t be able to cook a great meal out of rotten products!

The following sound example is, I believe, is a great illustration of how re-amping could be used not just as acoustic restoration tool, but as well, as a powerful mixing technique. No artificial reverb has been used for the mix. The only exception is a bit of stereo delay on two tracks of the psychedelic acoustic slide guitars. This delay effect was actually re-amped together with the dry sound of the slides (each channel individually with different speaker position for extra stereo width). For the recording I used a pair of the very linear DPA 4006 (nearfield grids) omnidirectional microphones mounted on a Jecklin disk going into Grace Design preamps and ADC. The single speaker used for the playback was an Adam A7. According to the manufacturer, it has a flat frequency response from 46Hz to 40KHz.

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

Speaker position for the differnt instruments.

This is approximately how the speaker was positioned for the re-amping of each instrument in the mix. Even a single speaker in enough to deliver a great and spacious stereo result.

The concept of the experiment was very simple and straight forward. The omni pair of DPAs in combination with a Jecklin Disk represents the listener head and ears. It delivers a very natural sound with no lost of low frequencies when recording sources at a greater distance. The localization within the stereo picture is improved by the shadowing effect of the disk. Keeping the mics at the same position and the preamps at the same gain level, but moving the speaker around, helped me to create the illusion of a single listener’s position-perspective and a whole room full of different sounds at various positions around it.

If you can imagine the desired place of the instruments in your mix, simply move the speaker at that position in the room. This will give you a result with a real stereo information for every track re-amped. Furthermore, the natural loss of high frequencies, the difference in the amount of reverberation and the realistic and coherent acoustical information in terms of early reflections for the various tracks will create a whole new dimension of depth in your mix. One of the main ideas of the experiment was that the best re-amping is achieved when all faders in the mixer for the re-recorded tracks remain at 0dB. This methodology can be justified as a more realistic one by the fact that every room will react to the re-amped sounds differently depending on the playback levels. This implies correct levels of playback in the room and a pair of good ears!

Front to back perspective

With this technique one could play a lot with the front to back image of the mix. The process introduces one big challenge though. It is quite tricky not to overdo/not get enough of the verb. Once the session is over, during the mixing process, it may turn out that some of the instruments have not been recorded in their ideal position. I have found a few ways to address such problems.

If a track is too wet, mixing some of the dry non re-amped signal will bring it closer to the listener’s position. A good strategy is to use a sample delay as an insert plug-in on the dry channel and experiment with various times. Adding more delay to the track will make it less focused, but with some delay it will blend naturally with the re-amped signal and you will able to use more of it, without this being apparent. The less you delay the dry sound, the closer it will appear in the mix. This is as well a good way to find a setting for which there is no unpleasant comb filtering occurring. And if a desired time delay setting presents phase issues, phase reverse or a phase rotation plug-in could come in handy. There is a contra-argument to this theory that without the use of time delay a very small amount of the dry sound needs to be used to achieve more noticeable results (i.e. bring the instrument closer to the listener).

Another approach, which would introduce even more flexibility in the post-production phase, is to use an additional stereo pair at a greater distance within the diffuse field for a separate tracking of a wet signal only. In this case it makes sense to record with the main pair everything just a little bit drier than ideal, as more reverberation could be added later on. When doing this, one should take into consideration the stereo width of the wet signal. A safe bet would be to try to match the stereo width of the main pair. Because of the greater distance it would imply a greater spacing/angling of the mics. On the other hand, putting them far apart in a big room will give you a huge, very stereo, more delay/fx like result (which could be great, although it probably won’t result in as natural and realistic picture). From my experience, directional microphones like cardioids, even hyper-cardioids, could be equally useful as omnis. The reason for this is their better focus in the mix.

Talking a few impulse responses of the hall could be very useful too. You could even go further and have one for every speaker’s position. In this way you can always add a bit of reverb to each track with perfectly acoustically matched for the purpose preset. On top of this, no one has said that re-amping should be used for all tracks in your project. Maybe just a few instruments would benefit from this approach. Having all those various impulse responses of the room will give you the possibility to place other instruments in the same space, but in different positions, during the mixing, if needed.

The stereo image and stereo width

Choosing one single recording technique, and moving the speaker around, helped me to maintain consistency and have a straight forward method, which made the job easier. In this way it was easy to predict the outcome of a speaker’s placement. However, one might want to have more options and use multiple recording techniques for the same project. Here the possibilities are endless. We can design out own complex space. This includes not only the use of transducers with different polar patterns.

Instrument positioning in the mix.

It is very important to imagine the place of each instrument in the mix prior the re-amping.

For instance, here we have a case where the engineer could consciously choose to record some of the re-amped tracks with a “hole in the middle” of the stereo picture. Such distorted image would sound unnatural and even unpleasant, if listened by itself. But in the case of a crowded arrangement, it can actually be used as an advantage, leaving lots of unused space in the middle of the picture. On the contrary, sometimes too much stereo information could overcrowd the mix and having the option to use only one of the mics in mono might be exactly what you need. In this case spaced omnis have the advantage that at any time one of the channels could simply be muted and the other panned to the desired place in the stereo image. Doing the same with directional microphones might lead to high frequency loss due to the frequency-dependent directionality of the transducer. However, the use of near-coincident techniques (with directional microphones) would give you a much better localization and sharpness of the image. Again, this will leave more space around the recorded source for the rest of the tracks. A minus of those techniques is that sources recorded form a greater distance will lose low frequency information due to the equalization of the microphone (proximity effect).
A disadvantage of techniques relying on wide spacing is that it is rather difficult to change the panning of the so recorded source. All pan pots ideally must remain to the hard left and hard right in order to avoid phase issues. One way of solving the problem, which I have found, is to keep the left and right channels panned hard but to reduce the volume of one of them. This method delivers a result, which although not as natural, would still help you to move the source towards the extremes of the stereo image and will free more space on the contrary side of it. The problem, however, does not affect coincident pairs (XY, MS, Blumlein, etc.) because of the very close proximity between the two diaphragms.

What’s best is that the re-amping process gives us the ability to fully manipulate the stereo picture and the depth of out mix uncompromisingly and with a great amount of flexibility.

More about re-amping:

I. The common case. Re-amping electric guitar (Part I)
II. Re-amping in the time of low budget productions (Part I)
III. The uniqueness of every space. Re-amping vocals inside a washing machine (Part II)
IV. Mixing with no faders or pan pots. Multitrack re-amping of acoustic material pre-recorded in a dead room (Part III)

Leave a Reply