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Natural Science Forum / Physics / Acoustics / September 2004BSWA microphones
Hello! I am thinking of using BSWA type1(MP201) and type2(MP206) microphones in my project. The URL to their site is http://www.bswa-tech.com/products-mp201.htm Does anybody here has some experience with this company and this microphones - good or bad. Any information would be gratefully appreciated. Best regards, Tomaz Kopac > I am thinking of using BSWA type1(MP201) and type2(MP206) microphones in my > project. The URL to their site is > http://www.bswa-tech.com/products-mp201.htm > Does anybody here has some experience with this company and this > microphones - good or bad. Any information would be gratefully appreciated. No experience with these, but they look like they are sized to be a standard 1/2" cartridge. They should fit standard preamps. Some notes: 1- 20 Hz lower cut-off is a bit high for measurement microphones, where below 10 Hz is more common. 2- It indicates a free field style; presenting a flat response only when the normal to the diaphragm disk is pointed at the sound source. (It's NOT a random incidence mic used so often in architectural acoustics). 3- The electret type microphone may be sensitive to moisture environment... the only way to tell how good these are is to buy one and use it in all field conditions where traditional condenser microphones work well. If it survives a year or so without calibration drift of more than 0.1 to 0.2 dB, then it is acceptable. 4- Examine the guarantee carefully. Being able to exchange a bad unit for a better unit is important. 5- Of course, exercise it with your existing preamps to be sure it mounts and dismounts without any snags. Angelo Campanella In article <531%c.560064$Gx4.214363@bgtnsc04-news.ops.worldnet.att.net>, > 3- The electret type microphone may be sensitive to moisture > environment... the only way to tell how good these are is to buy one and > use it in all field conditions where traditional condenser microphones > work well. If it survives a year or so without calibration drift of more > than 0.1 to 0.2 dB, then it is acceptable. Angelo, Are you implying that electret mics are more sensitive to moist environments that typical 200V polarized mics? I (and others) have had the exact opposite experience - we've found electrets are more stable high-humidity environments compared with polarized mics (or at least B&K polarized mics).  SignatureHerb Singleton usenet3@ross-specrtrum.com Sound & Vibration Measurements http://www.cross-spectrum.com Have to agree with Herb. > In article > <531%c.560064$Gx4.214363@bgtnsc04-news.ops.worldnet.att.net>, [quoted text clipped - 12 lines] > high-humidity environments compared with polarized mics (or at least B&K > polarized mics). > Are you implying that electret mics are more sensitive to moist > environments that typical 200V polarized mics? I (and others) have had > the exact opposite experience - we've found electrets are more stable > high-humidity environments compared with polarized mics (or at least B&K > polarized mics). It's all a matter of degree. I have LD 700's and 720's for 24 hr outdoor monitoring. Those fitted with electrets usually drift a bit downward when it rains. Those with ceramic mics are flawless (above about 10 degrees F.). I have not deployed condenser mics in that way, except for other extremely well designed condenser mic outdoor systems with desiccants. This experience has made me wary of electrets, though they may be slightly more immune to moisture than electrically polarized air condenser microphones. Fitting with desiccators is likely still required (for the 700-720, I do not use desiccators). It's just something to look for. Ang. > the exact opposite experience - we've found electrets are more stable > high-humidity environments compared with polarized mics (or at least B&K > polarized mics). There are two scenarios... one is with desiccants, and the other is without. The most troublesome precision (type 1) situation with air condenser microphones, without desiccants, is use on construction sites where outdoor conditions prevail all day. Here, I have had sensitivity drifts downward if I did not protect that mic. Are you saying that this situation is improved? The other is noise floor. Again, on construction sites, where high TL walls are to be tested, the noise floor of the mic is critical (good walls; stone silent receiver room conditions; moisture can ruin my day). The noise floor of a good 1/2" mic in the 1k, 1/3 octave band region is about 15 to 20 dB re 20 uPa. Where does the electret fall? (Put calibrator on mic, turned off, as a room noise shield, and read the 1/3 levels.).. I have occasionally had to resort to a 1" mic to get clean results, especially inside audiometric test booths. Ang. C. > Are you implying that electret mics are more sensitive to moist > environments that typical 200V polarized mics? I (and others) have had > the exact opposite experience - we've found electrets are more stable > high-humidity environments compared with polarized mics (or at least B&K > polarized mics). There are two scenarios... one is with desiccants, and the other is without. The most troublesome precision (type 1) situation with air condenser microphones, without desiccants, is use on construction sites where outdoor conditions prevail all day. Here, I have had sensitivity drifts downward if I did not protect that mic. Are you saying that this situation is improved? The other is noise floor. Again, on construction sites, where high TL walls are to be tested, the noise floor of the mic is critical (good walls; stone silent receiver room conditions; moisture can ruin my day). The noise floor of a good 1/2" mic in the 1k, 1/3 octave band region is about 15 to 20 dB re 20 uPa. Where does the electret fall? (Put calibrator on mic, turned off, as a room noise shield, and read the 1/3 levels.).. I have occasionally had to resort to a 1" mic to get clean results, especially inside audiometric test booths. Ang. C. > In article > <531%c.560064$Gx4.214363@bgtnsc04-news.ops.worldnet.att.net>, [quoted text clipped - 12 lines] > high-humidity environments compared with polarized mics (or at least B&K > polarized mics). When General Radio introduced in 1970's their 1933, the first precision sound level meter (with inbuilt 1/1-octave filters) using electret microphones, B&K people published some studies describing rather "dramatic" sensitivity drifts of GenRad's new microphone type. Expected reason was high sensitivity to humidity (RH) and temperature changes. Long term drifts reported were max. 3 dB, short term +-0,5 dB. Have a look, for example, Rasmussen G, Measurement microphones, Inter-Noise 1974 Proceedings, 55 - 60. This was 30 years ago. Kari Pesonen > When General Radio introduced in 1970's their 1933, the first precision > sound level [quoted text clipped - 8 lines] > 1974 > Proceedings, 55 - 60. I have seen problems with GenRad's electrets (when I was promoted to a supervisory at a lab a couple of years back, the lab manager & I quickly got rid of our GenRad mics ;), but B&K, LD and GRAS electrets have all been rock solid under a variety of conditions, especially compared with B&K polarized mics. Heck, even the generic Type 2 stock mic that came with my TerraSonde ATB Pro hasn't drifted more than 0.1 dB when operating outside in the rain for 72 hours. But the issue we've seen with 200V mics is spurious data (pops and crackles) caused by arcing between the diaphragm and back plate. Herb SignatureHerb Singleton usenet3@ross-specrtrum.com Sound & Vibration Measurements http://www.cross-spectrum.com |
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