Published on
August 23, 2009 by
Tim
One of the first assignments I was tasked with as a graduate student was learning how to design printed circuit boards or PCBs for short. There are many different pieces of software which allow you to design PCBs but in my case Number One Systems EasyPC was the software of choice.
There are two different ways to design a PCB in EasyPC. The first approach is with schematic files. Schematic files allow a user to create a circuit schematic and then translate that schematic to a PCB design. Alternatively, circuits can be designed directly in the PCB editor. The first method is most often the method of choice for medium to large designs. Small designs can often be done directly in the PCB editor.
Circuits are designed in both schematic and PCB mode by using components. Components in EasyPC are made up of two distinct parts. The first part is a schematic symbol which is used in schematic design mode. The second part is a PCB footprint which is used in PCB design mode. By using components, translation between schematic and PCB designs can be easily accomplished.
Once you have learned the navigational structure of the program and designed a few components, it is relatively simple to design a simple PCB. The board pictured above is my first design and will host a computer which will be incorporated into a shoe. It is approximately 1.5 inches square. We soon hope to design a new version of this board which is about one quarter of the current size.
Published on
June 18, 2009 by
Tim
Two low end audio compressors, the Alesis 3630 and the Behringer MDX2600 both run for about $100. We decided to match these two compressors up next to each other and see which one came out on top.
The Alesis 3630 is a unit which does what it claims to. It sports all the necessary features of a compressor as well as including a gate with threshold and rate control. As connections go, it supplies a 1/4″ TRS connection for each channel as well as a 1/4″ TRS connection on each channel to allow the unit to be side chained with another processing device. An external “wall wart” supplies power to the unit.
The Behringer MDX2600, on top of the compressor, adds a basic gate with slow or fast release time selection. It also boasts a single knob de-esser with selectable male or female modes of operation, and a one knob peak limiter. The MDX2600 offers a host of external connections. Each channel has an XLR input and output as well as balanced 1/4″ inputs and outputs. An unbalanced input and output are featured on each channel for side chaining other devices. The device also features a IEC C14 power connector, mitigating the need for a pesky wall wart.
Both of the units worked well in our tests. The Behringer unit seemed to have a slightly better sound quality while the Alesis unit appeared to color the sound slightly. The Behringer unit had positional knobs, making adjustments jerky and often noticeable during live operation. The largest downside to the Alesis unit is that it peaks out with signal levels at +6dB where as the Behringer unit offers much more headroom, allowing signals up to +18dB.
So in the end, which device comes out on top? By my vote, neither. The low headroom on the 3630 and the positional knobs on the MDX2600 make both units almost impossible to use for any live sound application. My vote goes to investing $50 more in a quality unit like the DBX266XL. If though under duress I had to pick one unit, I would pick the Behringer unit. The added features and the better sound quality give it the overall advantage.
Published on
June 16, 2009 by
Tim
How much program is really in those rear speakers you spent so much money to buy? What is that super subwoofer you have accomplishing? The answers to those questions; maybe not much.
Before everyone starts throwing stones, let me explain.
Lets start with the subwoofer. What is the point of a subwoofer? No, the point is not to gyrate the popcorn you are stuffing down. Different size speakers naturally lend themselves to producing different frequencies better. Small “tweeters” are specially designed to reproduce the highest frequencies in the audio spectrum. Larger speakers lend themselves better to producing lower frequencies. A set of 2-way main speakers should be pretty hefty with at least eight inch woofers in my opinion. A good eight inch speaker should have no trouble handling frequencies all the way down to 20Hz. If your main speakers can handle frequencies all the way down to 20Hz, a subwoofer is no longer needed.
Next, lets talk about the center speaker. Maybe someone can set me straight on this, but I can not think of a good purpose for the center speaker. It seems to me, that if your system includes a good set of main speakers, the center speaker is close to worthless. If you want a sound positioned in the center of the sound field, it can be panned evenly left and right to achieve the same effect as putting it solely in the center speaker.
Now since we have eliminated the center speaker and the subwoofer by adding a great set of main speakers, the rear speakers are all that is left to get rid of. Depending on the setup, 5.1 or 7.1, a surround system could include 2 or 4 different rear speakers. These speakers really complete the ultimate theater experience by immersing the viewer in the sound. Dolby 7.1 is really overkill and most movies do not even support it, so we can automatically reduce our system to just two rear speakers. Now many people will say that they must have their rear speakers for the full theater effect. For the rest, remember first of all, almost any movie made before 1990 does not have surround. Also, any other material which you shove through your system, over 95% of it is going to have material located in the front speakers only. So for those of you who want to have their rear speakers for the 5% of material that uses the rear speakers 5% of the time, go ahead, get yourself a set of rear speakers. For everyone else, realize its just not worth it.
All this is to say that cheep surround sound is really a lie that has been brought into. Investing in a great set of main speakers will yield a much better result than buying a full surround system set.
Published on
June 2, 2009 by
Tim
Arguably one of the best tools available to a sound engineer is the compressor. A compressor is a device that reduces the dynamic range of program material. In a perfect world, there would be little need for compressors. Alas, we live in an unperfect world and due to the varied talent of the musicians we work with, compression is often required to make things sit correctly in the mix.
So how do you actually use a compressor? Well I was prepared to write an entire article on the subject until I found an excelent article written by John Mills. You can find the article here.
Published on
April 29, 2009 by
Tim
Acoustic guitars are used in all types of music; from rock to a solo classical guitarist. Depending on the type of music, the method for mixing an acoustic guitar can vary.
The notes an acoustic guitar is tuned to range from about 80Hz for an open 6th string to about 660Hz on the 12th fret on the first string. There is a lot more to a guitars sound than just the actual notes its strings are tuned to though. Vibrations from the body and noise from fingering or the pick also add to the overall sound of a guitar.
So what is a good starting point? In many mixes, the first place to start is by rolling off the low end. This can be anywhere from 60Hz for an accoustic set to 100Hz for a rock mix. Next, the boominess can be tackled. The boominess of an acoustic guitar usually lies somewhere between 150Hz for an accoustic mix and 700Hz for a rock mix. Finally, giving a little boost around 2kHz and another in the 15kHz range can add some zing and sparkle to the guitar.
That is about all there is to it. Some people might like to add some very light compression, in the 2:1 range, but I usually just prefer to leave well enough alone.
