K6JRF's Page
formerly W6FZC
Audio Setup and Adjustment Page
(Updated: Oct 10, 2008)

This Adjustment Page discusses the techniques for achieving balanced transmit audio through your transceiver by use of adjustment techniques that quickly lead you to it.

How do adjust my audio equipment to get good transmit audio?
I suppose there are as many ways to do this as there are audio enthusiasts, but here's a general method that I employ to get balanced transmit audio. I personally use SpectraPlus in conjunction with my audio equipment to see where audio peaks and valleys are so that I may compensate those areas, if need be.

This is not to say that the audio should necessarily be ruler flat, but at least using this technique, you can see where improvement is needed if your ears confirm it!

Start with the highest frequencies first! This may be obvious but most do not because the bottom end is usually easier to obtain and, when listening in headphones, the high frequencies sound harsh, so they are toned down to where they sound pleasant. The high frequencies are those from 2Khz to 4Khz.

A rule of thumb says. . . if the headphone audio sounds a little bright and maybe even 'brittle, then it's probably about right when transmitted through the radio. This is because the high frequencies are literally lost in the radio, so extra boost is needed to get those 'fragile' frequencies out of the radio. It's the high frequencies that bring articulation and clarity to your audio. They are very, if not the most important part of the audio signal makeup.

So turn down (or better still, turn off) all low frequency enhancement devices such as Aphex 104, Behringer UltraFex, etc.. Also turn off any gating and compression devices for this test. You only want to hear high frequencies in order to hear subtle distortion and/or tearing. Tearing occurs when the audio signal 'flat-tops' which causes intermodulation products that were not there initially to be generated causing very bad distortion.

I do the following; turn up the Behringer Ultra FX Pro control fully clockwise and slowly sweep through the frequencies (say 700hz to 6Khz) while listening for a 'sweet spot'. What's a sweet spot?? To me, it's when the audio enhancement seems to disappear into your ears so you cannot distinguish the sound emanating from your mouth from that in your ears.

Now adjust the MIX control for a more effective level and work the myriad of controls that your AE has. This is very equipment dependent. When all else fails, don't forget to read the Owners Manual!

Now tackle the mid frequencies next! The frequencies between 250hz to 800 hz are almost as important as the high frequencies. To much of these frequencies make the audio sound like Broderick Crawford at his mic in the '60s TV show. Pretty bad sounding stuff. Personally, I never enhance these frequencies, only attenuate them.

I do the following: Using the high frequencies setup above, I now add my DDP's Parametric Equalizer set to Band 2. With the LEVEL set to -8dB and Q= 2.00, I sweep the frequency band from 150hz to 800hz, listening for a sweet spot. The sweet spot is different than before. Here you voice literally resonants when you get there. The 'flatness' disappears leaving the vibrant part of your voice. It will take some experimenting with this technique but it'll pay off. You may have to adjust the LEVEL and Q to achieve this but it will happen.

Lastly, adjust the low frequencies! Here we all at times have been carried away. What you want to effect is a balancing act with the mid and high frequencies. The trick is to make them all blend together and have the bass add balance to the high end. The bass should not boom like a drum, but have girth and heaviness to match your voice characteristics. Be careful about boosting 100hz thru 200hz! Do however add 50hz thru 80hz but the level should be reduced as the frequency increases. Too much bass adds muddiness to the audio and takes away from whatever clarity you may have.

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