WM-61A mic

Discussion in 'Microphones, Speakers & Audio Processing' started by N3DT, Feb 7, 2020.

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  1. N3DT

    N3DT Ham Member QRZ Page

    I got a bunch of these things a couple years ago after reading about their response. I finally got around to making one as a source follower circuit (it's about half way down this page http://www.linkwitzlab.com/sys_test.htm#Mic) and used it with my sound card to measure the freq response of some items I have around, a very old Panasonic bookshelf speaker, a Grado 80 headphone, eGrado headphones, an Anker bluetooth $30 speaker, and an old set of Pioneer HPM-100's. Here's a spreadsheet of the results. I've been thinking about getting one of the programs that sweep these things automatically, I'll get to it. But what I find interesting is the rising rate of audio levels in the headphones. The HPM of course have the best bass response, but seem a bit erratic in the overall levels. The Grado 80's seem to have the best 'presence' of the lot. I can hear things in them that don't even exist in speakers or other headphones.

    I drove the headphones directly with the 'tone generator' output of my Moto 2005HC service monitor and the speakers through a small 15W class D amp I use for the computer. The Anker BT I drove right from my computer's BT, it has it's own amp. I'm surprised how high they respond, I really can't hear much of anything past about 12KHz.

    I need to make up a TL072 or 074 preamp for the thing. This was just using the line/mic input on my Zonar 192KHz soundcard, which has a much better frequency response than the RealTech that came with this HP W10 computer.

    I just thought it was interesting, I've seen some old articles here about using these mic elements. I may make one just to try over the air. The holes in the lines are where I didn't take data.

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