Microphone specs & equalization

Since obtaining my Flex-3000 transceiver months ago I've been using the supplied FHM-1 hand microphone.  Early reports from my ham friends said that my voice sounded muffled compared with how I sounded using the old desk microphone with my Heathkit SB-104A. Below is a copy of the microphone specs graph from FlexRadio.  A switch on the microphone has two positions for what they call "tone settings":

• Setting 1 has a flat frequency response of 60 Hz to 16 kHz.
• Setting 2 rolls off some of the low end frequencies (-6 dB at 300 Hz) and provides 3 dB of boost at 2 kHz for "optimum articulation needed for DX / communication quality audio".

On-air reports indicated no appreciable difference between these two settings.

I explored the transmit audio equalization settings in the Flex-3000 to compensate for the microphone's apparent poor high frequency response.  I tried several configurations to boost the treble, up to the available maximum of +15 dB. Although I thought I had all the right boxes checked and buttons clicked, the audio reports were still unsatisfactory. I began to test some quick and dirty arrangements to use either my Andrea NC-61 headset or my original dynamic desk microphone in place of the FHM-1 microphone. These efforts indicated a need for better impedance matching and better shielding to prevent hum. My most recent inclination was to build a microphone preamp circuit in a metal box to accomplish impedance matching, gain, and powering (for the Andrea's electret element). The Flex-3000 front panel jack has 5 V DC available along with PTT, ground, and a balanced microphone input. A rear panel line audio level input is also available.

While reviewing the transmit audio equalization settings early this week I observed the audio closely on the audio spectrum display of the PowerSDR program and listened to myself on the SB-104A. The saved audio profile that I created months ago was not doing what the equalizer curve said it should. I created a new profile from scratch and found that it really did improve the audio spectrum appearance and sound. On air tests the next day confirmed this.  Below is a screen shot of the equalizer settings I am now using.

Note that the audio is boosted 15 dB at the 2 kHz and 4 kHz bands of the equalizer, and is cut below 500 Hz. The little Enabled check box can toggle this equalization with one mouse click. I found that this box was unchecked on the profile I had previously created and saved. I don't know if I lost track of that box during multiple changes followed by multiple saves or if I toggled it off for working digital modes. For the latter, I am now using saved profiles that set frequencies, bandwidth, equalization and audio paths (virtual audio cables) to ensure correct operation while making it easy to return to voice modes.

Thanks to all for their helpful signal reports!

John