SLE - Week 1

First off, I have to be honest: LDI was my first technology tradeshow.  I’m quite familiar with how these conventions work, though, as I’ve been to the Detroit International Auto Show for the past five years.  But let me be clear; LDI was the most impressive thing I have ever witnessed, hands down.

I think the most obviously captivating booth at the show was LaserNet, considering you could see their demonstration from anywhere in the hall, and the most impressive was the most talked about Chauvet exhibit.  I don’t believe I have ever seen more lights crammed per square foot in my life.

But enough about superficial aesthetics.  There were only three products that I was truly impressed with.  Clay Paky caught my eye first with their unique rotating truss.  But it was what was on the truss that I was blown away by: The Sharpy Moving Light.  It is the quickest moving yoke fixture with a 190 W discharge lamp that outputs a zero degree beam of light.  While it may not be of any use for lighting a subject, it definitely has it’s uses for moving effects on large rigs.  With such a narrow beam and rich color mixing, I would even use them for truss warmers.

Second in lighting was the GLP Impression Spot One – a moving yoke fixture containing only LED’s with a comparable light output of a 575W incandescent.  Complete with 2 rotatable gobo wheels, an animation wheel, RGB color mixing, focus, iris, and prism, I was truly impressed by the bright and crystal clear output of the fixture.  The halo-free and completely smooth pool of light made a very defined hard edge that could be nicely faded by using the focus parameter.  It also boasted very nice flicker-free electronic dimming and super quick electronic strobing.

Lastly, I was nearly completely sold after being introduced (for a whole hour) to the Compulite Vector series. The models on display where the violet (smallest) and red (largest) but several mid-sizes are offered as well.  The sleek and attractive work surface is complete with two (or three for the red) touch screens to make navigation and operation a breeze.  The intuitive software allows for quick and easy programming and flexible operation to move any function to any control on the surface.  Even the master AB faders can be moved to any one of the executable faders of your choice.  With the exception of the budget consoles (the violet and ultraviolet), the surface offers either 10 or 20 motorized playback faders which allow you to page through up to 200 fader playbacks and 200 executer-only playbacks.  All their consoles run Windows XP and can output 8 DMX universes either locally or over artNet.

I must conclude by also sharing that I had a wonderful time being part of the Full Sail exhibit and being able to share with other industry professionals about my time at the school and answer their questions about what we do.

SPS - Week 4

This week’s blog post comes from an article from DPAmicrophones talking about the process and specifications of measuring microphones.  Although the concept is fairly simple to go about taking measurements from a microphone, there are some discrepancies in how the measurements are taken, the accuracy of the data, and even how the measurements are listed according to the manufacturer.  

When charting a frequency response graph, manufacturers can actually use two methods to show better performance from their microphones than what a given actual product may be able to replicate.  Deception may evolve from two places: in measurement and in data representation.  There are two methods by which measurements can be taken: point-by-point and continuous sweep.  The point-by-point method measures a pure sine wave at several select frequencies and a graph is formed by the collected points.  Unless 20,000 measurements are taken, the accuracy of the chart is less than perfect, but peaks and valleys of the response are more detailed as opposed to the continuous sweep.  When measuring using a continuous sweep method, a sweeping sinusoidal wave through the audible spectrum is captured by the microphone.  The output is analyzed against the input and the resulting graph is printed in real time.  This method may seem more accurate, however it is required that a manufacturer lists the speed at which this method was performed on the resulting graph.  If the sweep moves too quickly, it is highly likely that a flatter response will be recorded since the diaphragm of the microphone does not have time to fully capture individual frequencies.  Deception may also come by the frequency response graph itself as manufacturers may show the actual measured frequency response, or a “typical” (averaged) response with a tolerance field (quality control).

The measurement standard for a microphone involves four things: The accuracy of the measurement equipment, the calibration of the measurement equipment, the laboratory’s acoustical environment, and the quality and calibration of the reference microphone.  However, finding a standard form of referencing measurements of different microphones has definitely been one major problem.  Different areas of the world adhere to different sets of rules and regulations set forth by their specific standards committee; the top three being the International Electrotechnical Commission (IEC), the Deutsche Industri Norm (German DIN), and the Audio Engineering Society (AES).  Right here from the get-go we can see a possible area for measurement discrepancy.  Some of the larger named microphone manufacturer’s are German and might be more likely to adhere to the DIN standard, while some other manufacturers from other countries might follow the regulations of the IEC.  Of course, this is just speculation, but nonetheless, defining an international ultimatum of standards is something that is still in the works.

It seems that there are still areas of questionable uncertainty when it comes to comparing the standards of multiple manufacturers.  For most of the measurement techniques, the results rely heavily on the comparison to a reference microphone, the measurement equipment, and most importantly: the anechoic room.  Setting aside the microphone preamps, power supplies, computers, analyzers, and etcetera, two very crucial problems remain: the reference microphone and the anechoic room.  No two microphones are exactly congruent, even if multiple manufacturers use the same make and model.  More importantly than that, however, is unless measurements are taken in a vacuum – which would defeat the purpose of measuring sound – all rooms are subject to noise of some kind.  Even the minutest sound would still be present in a measurement, which is still less than perfection.  Aside from nit picking, there are many uncertainties that still remain.  Perhaps either an ultimate international standard, or a single measurement company is the solution for ensuring that you get what you pay for.

SPS - Week 3

I was having a conversation with a friend the other day about the sound of a digital console.  While that does sound a bit crazy, and aside from the processing algorithms involved with dynamics and summing that can characterize and color the sound, the real sound of a digital all consoles comes from the input gain stage; the preamp.  Coincidently enough, I found this article from Rane Audio talking about the importance of matching microphones and preamplifiers.

This is actually something we take for granted.  When gathering specifications on a new system, we just think that the most math-heavy end will be the end of the signal chain: power amplifiers to speakers.  But that’s the easy part – amplifier and speaker manufacturers speak the same language when publishing specifications.  Microphone and preamp manufacturers do not.

Two things often not though about in the selection process is what are the impedances involved?  Many preamps allow high input impedances, but the one that matters is the actual impedance of the microphone, which is relatively low.  This scenario does not add any extra noise, but going in a reverse manner could.

A second thought concerns phantom power.  Do you need it and does a certain preamp provide it, and at what voltages?

And finally most importantly: headroom.  Is your mic’s dynamic range higher than what a preamp can handle?  This is where the math comes in since there is no one unit of measure that will clearly give a concise answer to this big question.  It starts with knowing the sensitivity of a microphone and its maximum source SPL.  The sensitivity is expressed as millivolts per pascal, which equates to a certain amount of voltage output when a microphone receives 1 kHz at 94 dB SPL (which is one pascal).  So through mathematical comparisons using logrithms, you can find what the maximum voltage output is for a microphone.  With that known voltage, you can convert backwards into dBu and compare apples to apples with the input specification for a preamp.

This method is the most straightforward answer to ensure that your microphone won’t clip the input of the preamp.  However, this figure comes by using a microphones maximum source SPL.  You may be content with accepting this number as the ultimate purchasing decision towards a preamp, but in the case of a vocal microphone, you can actually stretch out the truth.  For instance, say a certain microphone has a sensitivity of 20 mV/Pa and a maximum SPL of 150 dBSPL.  In the case of some (extremely cheap) preamp, 20 mV/Pa at 150 dBSPL might actually be too high.  But thinking realistically, 150 dBSPL is an outrageous sound-pressure level that the human voice is incapable of reproducing.  So you can actually get away with skewing the numbers in situations like this.  But just be sure you remember that for the next you go for the same setup when micing a kick drum.

One last thing that can be more annoying than problematic is noise.  Back to what I was saying earlier: different impedances can cause noise.  In the case of dynamic microphones, the higher the impedance, the louder the noise-floor.  However, condensers have active circuitry, which will induce noise into the signal.  As part of a condenser’s spec sheet, noise is listed as being equivalent to a certain dB SPL, A-weighted, which is usually shortened dB-A.  By using the same method as above, you can compare the millivolt output of a microphone to its noise-floor equivalent dB SPL to find the actual noise floor expressed in dBu.

SPS - Week 2

What many people do not know about me is that I am a pianist.  I am self-taught and have been practicing for 14 years.  I can tell you from personal experience that the piano is one of the most complicated and expressive instruments ever created.  Even more so, as most sound engineers have come to find, it is one of the most difficult instruments to mic.  Most people default to the mindset that a complex instrument needs several microphones.  But is there a possibility that less is more?  This week’s blog post talks about single-microphone techniques used by Pro Sound Web writer Jack Alexander.

Alexander makes a good point of why multi-micing a piano is a norm.  One microphone just can’t bring about the SPL the way a dozen mics can.  It also depends on if monitors are involved too.  One hypersensitive mic would just be more trouble than it’s worth.  But say for example you have a soloist; what better way to mic the piano than with a minimalist approach?

The first method is called the “high hole” method.  Inside the piano on the side furthest from the keys is the bulk of the brass frame with several holes in it.  Different pianos have a different number of holes, but usually the best one to go with is the second or third one counting away from the hammers.  While someone plays, listen to each hole.  One will sound fuller than the rest of them.  That’s the winner.  Take a piece of foam and tap it close to the hole.  Take a microphone and tape it to the foam with the capsule over the center of the whole, off axis by 90º.  Surprisingly, an SM57 works great for this technique.

The second method comes from John Lewis of the Modern Jazz Quartet.  With the lid of the piano fully opened (that is, on a high stick), place a Sennheiser 421 on a boom.  Place the capsule, parallel to the floor, aimed directly into the lid of the piano, 1/8” off, mid way of the body, three-quarters of the way vertical. The result is a flat piano sound without non-linearities.

The third method is one that is usually attempted, and despised, by most engineers at some point or another.  Simply stick a microphone under the piano aimed at the soundboard.  This technique usually gets a bad reputation because it is too biased on the high or low side or just overall too muddy.  But this only comes at lack of understanding how to properly employ the technique.  To find the correct position, get under the piano and tap the soundboard on the high side until you find a place where the upper and lower tones are balanced.  Place the mic on a short boom and get it as close as you can without touching.  The result is very dark and rich tone.  The draw back is a bit of less linearity as compared to the lid technique, but this method is beneficial when sight lines are of importance.  The suggested microphone to use is a Neumann 105, but any condenser (should probably be a high SPL) should do the trick.