AE 282: Spring 2004

INSTRUCTOR: Eddie Ciletti

WEEK-1:  Summary, Assignments, Reference Material and Links

SUMMARY
Preparation for the Final Exam starts now.  Each week you must submit a progress report, in week-2, all that's required is a paper and e-mail outline of your plans.  The rhythm tracks should be completed no later than week-5 so that you can deliver a rough mix by the Mid-Term Exam.  The Final Mix is the Final Exam and is due week-12.

In the first class, students were asked a range of questions to determine strengths and weeknesses both in the practical aspects of actual recording and mixing as well as general audio knowledge.  We pumped a 40Hz tone into the studio and walked around listening for nodes - places where the tone was lost or was loud - to emphasize one of the reasons that low frequencies can be so elusive.

One of the most common problems is the bass-heavy mix.  At the other end of the spectrum, it is important to act upon instinct - if a track or mix seems too bright, then immediately take action before the ear becomes accustomed to the problem.  While the term, "Bass Management" became an issue with the introduction of Surround Sound, it can be globally applied to all recording situations.

ASSIGNMENTS

  • Determine how the feed to the SSL's Channel Insert Patch Point changes with the various status options.
  • Submit an outline of your plans for the final project.
REFERENCE MATERIAL

The Equal Loudness Curve details the ear's non-linear sensitivity to the audible spectrum. 20Hz to 20kHz.  The ear is least sensitive to bass frequencies when the overal Sound Pressure Level (SPL) is low, the "curve" at the threshold of hearing being most severe.  While it never actually flattens out, the curve does get smoother as SPL increases.  For the audio control room, 85dB-SPL is considered a reference level.  All engineers should be aware of, and have access to, a sound pressure level meter.  It is important to limit exposure to excessive SPLs  to preserve hearing.  If your instinct and preference is to monitor at lower levels, keep the Equal Loudness Curve in mind as most control rooms and monitors are not compensated for lower level listening.  The "fix" would simply be to re-voice the room / monitors by increasing the low frequency response.  On a consumer audio system, you hope this is accomplished by a front panel switch, although it is sometimes integreted without the ability to be disabled. 

Links begin here.  More Links BELOW


The Proximity Effect of directional microphones (cardioid and figure-of-8) is the increase of low frequency amplitude as the microphone is placed closer to the sound source.  Relative to all that was explained about the Equal Loudness Curve, this can create the illusion of the sound being "right" when in reality there is a good chance that a bass-heavy foundation is being laid.  This may create problems in a rhythm track, for example, when overdubs are likely to be referenced, and possibly re-voiced, to "fit the track." 
 

Armed with these two bits of information, students are advised to skeptical about all Monitoring Systems until proven worthy.

WHERE DOES "THE SOUND" COME FROM?

It is important to understand the difference between sonically "neutral" equipment and gear that imparts "color."  In electronic terms, "neutral" best desribes the primary goal of the classically trained design engineer - Linear Amplfication.  Before the Integrated Circuit, gain was accomplished one stage at a time, using discrete components such as a vacuum tube or a single transistor. 

Discrete designs are generally capable of linear operation when used conservatively, in the nominal region with adequate headroom.  But, they also have a non-linear region between nominal and just before clipping.  Hard clipping is obvious and, unless going for an effect, is avoided.  However, the non-linear region has a way of "dealing" with transients in a way that is far less obvious. 

The effect is similar to a peak limiter - the signal is absorbed and somewhat reduced from peak-to-peak.  In its place are added harmonics, the "nice" way to say that a complimentary distortion is added to the equation.  This sound is often referred to as "warmth," a harmonic richness that adds to the RMS or average level even while diminishing the peak-to-peak or transient amplitude.  This is what  "classic" vintage gear is all about.  See Table-1 for examples of both types fo gear.


 
NEUTRAL
HYBRID
IN LIVING COLOR
 
Crane Song
Altec
 
Pendulum
API
Grace
 
Great River MP-2NV
Millenia Media
Manley
Neve (Class-A 1066 /1073)
SSL
Summit
Trident A range (Daking)
 
UA / UREI 1176
TABLE-1: From Left to right, examples of Audio Gear  with progressively more "color."


Link to WEEK-2

Last updated 14 April 2005.  This is a work in progress.

Eddie Ciletti can be reached after 2pm Monday and Wednesday and Friday until 1pm at: 651-554-0304.