On Wed, 2008-02-13 at 12:12 -0800, Ron D'Eau Claire wrote: > There were some microphones produced for the "communications" market back > then such as the famous Astatic D-104 which had a microphone element with a > shaped response showing a distinct hump around 3 kHz, rolling off slowly at > lower frequencies and somewhat faster at higher frequencies. That hump > helped with "articulation" by emphasizing the mid-range speech frequencies.
This is a presence peak. > I don't know if anyone is doing that today for mainstream communications > microphones. Today Paging Microphones are still specifically designed to have this pronounced mid range presence peak and also usually include Quite a bit of low frequency Roll off Shure have a range of dynamic elements available for this market, that have response curves that look remarkably similar to the HC4 and HC5 elements. take a look at the response curve of the Shure 450 http://www.shure.com/ProAudio/Products/WiredMicrophones/us_pro_450SeriesII_content a direct link to just the curve http://www.shure.com/groups/public/@gms_gmi_web_us/documents/web_resource/site_img_us_rc_450series2_larg.gif the 522 has a broader presence peak http://www.shure.com/ProAudio/Products/WiredMicrophones/us_pro_522_content Direct to curve http://www.shure.com/stellent/groups/public/@gms_gmi_web_us/documents/web_resource/site_img_us_rc_522_large.gif elements for these mics (and many others) are available at low cost as replacement parts. Heil sound plot their curves on a different log scale but after accounting for that the similarities are remarkable. http://www.heilsound.com/amateur/products/hc4/index.htm The needs of paging systems which include efficient use of limited power and maximum intelligibility in noisy environments are pretty much identical to our requirements for effective SSB modulation. Any well made paging/ Dispatch mic (or element..) is ideal for amateur radio use, most are far more durable and cost effective than 'the made for ham radio' stuff that is popular these days. > Even the "high end" Ham mics only offer general and > uninformative comments about "shaping" and "clarity" that say much and > convey little. These words (in ham radio use anyway) have become marketing speak and now mean nothing. As a former audio professional I cannot understand why all the hype about Audio in ham radio and to my ears there's a lot of money wasted on trying to make SSB into something it isn't. > Interestingly, one of the big exceptions is the inexpensive > little Radio Shack electret element. It comes with a frequency response > chart showing a very flat response across the audio spectrum. If you are looking for flat then these are a great place to start, however the design of the housing may have quite an impact on how things sound, this can be used to your advantage to create a presence peak or LF roll off. My own headset is based on a salvaged electret condenser mic with some audio tailoring done by means of a simple R/C filter, being lazy I copied the circuit of an Icom handmic. It works great and cost me almost nothing. 73's Brendan EI6IZ -- Don‘t complain. Nobody will understand. Or care. And certainly don‘t try to fix the situation yourself. It‘s dangerous. Leave it to a highly untrained, unqualified, expendable professional. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
