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October Issue Feature: Tech Today - Real World Tuning

10-18-2017, Mobile Electronics -- By now everyone has heard about the winners for the Mobile Electronics Magazine Industry Awards. If you haven’t by chance, they are in this edition! This year’s candidates were all great and all well deserving. I was excited to hear that Chris Pate had won the Installer of the Year award. I recently wrote about my trip to France last summer and the tour of the Focal factory. On that trip were many other dealers. One that I had the pleasure of spending time with was Chris Pate.

Since I was 14 I have had a strong love for car audio. Through the years that passion has remained and grown. There are times in my life when I cross paths with others that share that same passion, and meeting Chris was one of them. I enjoyed spending time with Chris and learning more about his facility and the advanced tools he used. I personally wear many hats, but the one I probably most enjoy is that of fabricator. Over the period of a few days I learned from Chris how my life would not be complete without a laser cutter and sheet-sized CNC. Chris shared with me how he incorporates both of these into every day life at his facility.   
A short period of time before the France trip I attended KnowledgeFest in Dallas. It was at that event that I first met Chris.  I had the pleasure of listening to his incredible single seat car.  We then talked a bit about sonics and tuning. I thought it would be fitting to have Chris, the 2017-2018 Installer of the Year walk us through basic tuning in a real-world setting. Follow along as Chris shares his procedures on a car recently completed at his facility, Mobile Toys, Inc.

Chris' Part

So you just finished up that amazing install in your customer’s car.  You have spent hours drawing, designing, fabricating and installing the bevy of audio equipment your salesman sold. All the hours building and constructing this automotive masterpiece will be for naught if you cannot make it sound amazing. Point blank, any installer can build an audio system and dress it up. But for you to take the next step as an installer you need to be able to tune that ride. That doesn’t mean you must have a pair of golden ears or a pile of IASCA sound quality championships to make your customer’s ride sound great.  All you need is a tape measure, an oscilloscope, an RTA (real time analyzer) and a test disc with a pink noise, test tracks, and sine waves. 

Let’s start off by describing the car and system that has been installed and is in need of tuning. The car we will be tuning is a 2014 Subaru Forrester with a front three-way speaker system as well as a rear sub.  All speakers are run to independent amplifier channels allowing for an active crossover design. The midrange and high frequencies are handled by a pair of Illusion Audio C3CX coincidence drivers that have been installed in the left and right sail panel windows. The mid bass frequencies are being reproduced by a pair of Illusion Audio C8 eight inch drivers installed in the factory door locations on a pair of custom built PVC, mounted into the factory mounting holes. The sub frequencies are being reproduced by a single Illusion Audio Carbon 12-inch sub in a sealed enclosure with 1.25 cubic feet of air space. Amplification is being produced by a pair of Mosconi Zero4 four-channel amplifiers. For our source unit we have a Sony RSX-G9 high resolution media player. Last but certainly not least is our processor, a Mosconi 8-12 Aerospace DSP. 

As installers, we don’t have days to tune a car. We generally only have a few hours to test, make adjustments and then deliver the sound system to our customer. So let’s begin by pulling out our oscilloscope and setting the gains on our source unit, processor, and amplifiers. The key to laying a solid foundation for any tune is correct gain adjustments. We will be using sine wave test tones from the Focal Tools disc. The sine waves we will be using are 60hz for subs, 200hz for mid bass, 2khz for our midrange, and 8Khz for the tweeters. Each of these tones creates a reference level sine wave that can easily be seen on your oscilloscope.

When the signal is clean, you get a nice smooth curve from valley to peak, and when your amplifier clips it sends out distortion which can be seen as flat plateau at the top of each wave. The first step is to connect the positive and negative probes of your scope to your receiver's RCA connections on the back of the receiver. Once connected, make sure all equalizer settings are set to flat, the bass boost and loudness functions are off.  We start off by playing the 60hz tone on our source unit. We turn the volume up until we see the wave peak and plateau. Make note of the level the source unit is at.

Now we repeat the process on each of the next three frequencies making note of the volume level at which the source unit clips. In our case, the 200hz tone clipped at the lowest volume setting. This was level 40 on our Sony RSX-G9. We now know the highest level we can play our source unit cleanly is 39.  This process can now be repeated on our processor inputs, and our amplifier channels.

The process is very similar when setting the DSP input gains, but a little different on the amplifier side.  In the case of the amplifiers you will want to use the corresponding sine wave frequency that is directly related to what that set of channels will be driving. The sine waves we will be using are 60hz for subs, 200hz for mid bass, 2khz for our midrange and 8khz for the tweeters. We start by connecting the leads to the sub amp output channels. Make sure again that the gain is set to zero. While playing the 60hz tone at level 39 on the Sony source unit, begin turning the amp gain up until you see the scope’s wave form plateau, indicating the output of distortion.

Once the peak level has been reached, back the gain down until the wave form becomes smooth again.  This process will need to be repeated on each of the other three pairs of channels using the correct frequencies. By taking the time to correctly set the system’s gain you will maximize its output and limit its distortions. This process is actually very quick and easy to do once you get it down.

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