> then what kind of condenser-mics are not true?
Dunno, but MANY years ago my brother bought what looked like a good ribbon-style broadcast mike, and it was just a crystal mike. I think the box left it to your imagination.
> Just wondering, if electrets also qualify as true condensers
Sure. The blurb "true condenser" may have been picked to let your imagination run wild, but it is not false.
And what IS the difference? The mike does not care what made the charge it feels.
We can even argue that a good electret is a more steady quiet stable bias source than a 90V battery, a nasty little DC-DC converter, or stealing ~40V from the Phantom while also powering a hi-current transformerless output.
There are several types of electrets which is why we have different opinions.
The cheapest way is to put a charge on a thin film and use it as the diaphragm. Of course the ideal diaphragm has low mass and high strength, and most electret-chargeable films are second-rate in this area. But of course on a $25 mike, or even a $200 mikes, you are going to get a second-rate film: if you wanted the very best you would bring a lot more money.
An alternate is to put the electret on the back-plate. Now mass and strength are meaningless. Apparently this costs more; maybe not a lot more. However, if I did not need decade-to-decade calibration, I'd take back-electret any day. (Electrets decay: 10 dB a year in 1966, but my ~1980 electrets have not lost more than a few dB in 25+ years.)
The mess of $1 electrets found everywhere all include the FET, which simplifies integration but is almost never good for loud music, may be colored at medium-loud. But there are electret capsules without the internal amplifier, such as my Nakamichi/Teac interchangeable-head mikes.
> TSB-160A http://jlielectronics.com/transsound/electrets/tsb-160a.htm
That part says it has the FET inside. Note the suggested schematic and the 0.5mA current requirement. That conflicts with Svart's description of a 470pFd cap and a 680M resistor, which sure suggests external FET. But note that Transsound's own page is self-conflicted: the schematic shows a 3-terminal capsule, but the mechanical drawing sure suggests a 2-terminal capsule? It is possible some idiot webmaster (I been one myself) cut-pasted generic info without knowing that this model is a special. And of course when Uli calls and orders a million, Transsound will be happy to do it his way, and even happier if they can use tooled-up case and terminals from an existing model. (What this may really mean: Uli can buy cheaper FETs than Transsound can....)
The low-frequency noise is the barely big enough 680M resistor, a few Gig might be quieter, though I don't have a room with blower rumble so low that it matters. The high frequency hiss, if not just crappy FET, is the acoustic damping that controls the top-end resonance. Probably not the screen and shell, though maybe. Mainly the holes in the backplate, and also fairly small size and modest bias for a High Quality mike (but then, it's $25 and may be driving an $8 preamp).
If it is a too-cheap FET, then a swap might improve the noise.
Is this SMD? I hate modding SMD.
> Is it possible to add a bias to an electret capsule for better response?
I'm not sure how. The electret's "low" side is generally crimped into the shell or bonded to the backplate. I suppose jacking the backplate terminal around will shift the total bias.
But why? Small change in bias gives small change in sensitivity. That's why some of these models come in several sub-versions of different sensitivity: they sort-out sloppy electret and spacing tolerances. In commercial design, you should design your cellfone/whatever for the lowest-spec (cheapest!) grade, and if you were forced to take a higher grade then you would trim-down something in your preamp until the too-good lot was used-up. Other than that, there is no point in small bias change: you have a trimmer on your preamp.
Large increase of bias will increase sensitivity a bit, then the sound changes a bit as the diaphragm bows toward the backplate, then SLAM the diaphragm is sucked into the backplate and the mike goes dead. Sensitivity is good, so a mike-maker always gives all the bias that is safe, within production tolerances. The difference between sloppy commercial-tolerance bias and a maximum useful bias is not even a notch on your preamp gain knob. No response change will happen until it is on the jagged edge of collapse.
