LOTREE asks;
“What are the best music mediums for best reproduction by super tweeters?
And the best microphones for capturing ultrasonics?”
These questions are good ones and deserve a hard look.
First, the CD format CANNOT record any signal information once above about 22KHz, yes there may be something coming out above that, but it is not the input signal.
The Old 4 channel LP’s took advantage that when everything was right, one could record a second set of tracks when modulated into the 20-40KHz range (brought back down on playback). Back then, even using a fancy strain gage cartridge, the hf content was damaged after a fairly low number of plays.
FM radio has a FCC brick wall at about 15KHz, open reel tape is super sensitive to bias and head alignment, getting good performance at 20Khz is really tough already.
This leaves the 24/96 and better formats except very often this equipment has a low pass filter in it as well since there usually isn’t any signal up that high.
While it may be very hard for a speaker to reproduce ultrasonic’s, impossible to have flat response that high, one faces dramatic air absorption up that high and the most popular mediums cannot sample or store information that high, that’s ok because it takes a really exotic microphone to pick up sound that high too.
I like to think of sound as something like a Russian doll, what I mean is that regardless of the frequency, 10, 200, 20,000Hz, a given phenomena in sound occupies the same acoustic space. Where the doll for 20Khz might only be 5/8 inch tall (one wavelength), the doll for 20 Hz is 1000 times larger in all three dimensions BUT is identical to the 20KHz doll except for scale.
For a condenser microphone (the most popular type in measurement or recording) the size of the diaphragm is tied o the noise level the microphone produces and the hf corner. The smaller the diaphragm, the higher the noise level but higher the cutoff the mic has, it has less area, is less sensitive than a larger diaphragm.
I have a pair of Earthworks M-55 measurement microphones which have about a 5mm element, meaning they are pretty small, these do a sharp noise dive at 60KHz and are starting to directional above about 18-20 KHz.
Usually for recording, a quieter mic is used, typically with a larger diaphragm like a B&K4007, again the larger the diaphragm (that one about a half inch dia) makes the mic noise level go down (all other things equal).
So, at every stage, ultrasonic’s present a difficult task, one often skipped because when you actually measure the sound and try with and without, it is not worth the uphill battle for something most adults can’t detect the presence of even against a silent background , unless they know its on.
At least some of what is marketed as a super tweeter, (after much pressing) the distributor of one admitted it wasn’t even a speaker (although it looked like a horn externally) and didn’t actually produce any airborne sound.
To me, if someone has to make up an exotic story and then have to back down totally when pressed on technical aspects, is not selling something based on what it does but on what he can make one thinks it does. Of course, my impression is that a number of the products like rocks & clocks were magical, not electronic / acoustics / physics / science based.
What we think it does is the key, what we know, what we see, over rides what our ears tell our brain, even when you are fully aware of it. As the McGurke effect demonstrates, what we know rules the day, the only time you hear the reality of what is reaching your ears, is when you don’t include the visual information and remove the prior knowledge.
http://www.youtube.com/watch?v=G-lN8vWm3m0
Blind testing can provide different very results than when prior knowledge is included. But, to be clear, we only hear the acoustic reality when our eyes can’t see / we don't know. What we know and see normally over rides what we hear and we are fully unaware of the process as it is the only thing we know..
Best,
Tom Danley
“What are the best music mediums for best reproduction by super tweeters?
And the best microphones for capturing ultrasonics?”
These questions are good ones and deserve a hard look.
First, the CD format CANNOT record any signal information once above about 22KHz, yes there may be something coming out above that, but it is not the input signal.
The Old 4 channel LP’s took advantage that when everything was right, one could record a second set of tracks when modulated into the 20-40KHz range (brought back down on playback). Back then, even using a fancy strain gage cartridge, the hf content was damaged after a fairly low number of plays.
FM radio has a FCC brick wall at about 15KHz, open reel tape is super sensitive to bias and head alignment, getting good performance at 20Khz is really tough already.
This leaves the 24/96 and better formats except very often this equipment has a low pass filter in it as well since there usually isn’t any signal up that high.
While it may be very hard for a speaker to reproduce ultrasonic’s, impossible to have flat response that high, one faces dramatic air absorption up that high and the most popular mediums cannot sample or store information that high, that’s ok because it takes a really exotic microphone to pick up sound that high too.
I like to think of sound as something like a Russian doll, what I mean is that regardless of the frequency, 10, 200, 20,000Hz, a given phenomena in sound occupies the same acoustic space. Where the doll for 20Khz might only be 5/8 inch tall (one wavelength), the doll for 20 Hz is 1000 times larger in all three dimensions BUT is identical to the 20KHz doll except for scale.
For a condenser microphone (the most popular type in measurement or recording) the size of the diaphragm is tied o the noise level the microphone produces and the hf corner. The smaller the diaphragm, the higher the noise level but higher the cutoff the mic has, it has less area, is less sensitive than a larger diaphragm.
I have a pair of Earthworks M-55 measurement microphones which have about a 5mm element, meaning they are pretty small, these do a sharp noise dive at 60KHz and are starting to directional above about 18-20 KHz.
Usually for recording, a quieter mic is used, typically with a larger diaphragm like a B&K4007, again the larger the diaphragm (that one about a half inch dia) makes the mic noise level go down (all other things equal).
So, at every stage, ultrasonic’s present a difficult task, one often skipped because when you actually measure the sound and try with and without, it is not worth the uphill battle for something most adults can’t detect the presence of even against a silent background , unless they know its on.
At least some of what is marketed as a super tweeter, (after much pressing) the distributor of one admitted it wasn’t even a speaker (although it looked like a horn externally) and didn’t actually produce any airborne sound.
To me, if someone has to make up an exotic story and then have to back down totally when pressed on technical aspects, is not selling something based on what it does but on what he can make one thinks it does. Of course, my impression is that a number of the products like rocks & clocks were magical, not electronic / acoustics / physics / science based.
What we think it does is the key, what we know, what we see, over rides what our ears tell our brain, even when you are fully aware of it. As the McGurke effect demonstrates, what we know rules the day, the only time you hear the reality of what is reaching your ears, is when you don’t include the visual information and remove the prior knowledge.
http://www.youtube.com/watch?v=G-lN8vWm3m0
Blind testing can provide different very results than when prior knowledge is included. But, to be clear, we only hear the acoustic reality when our eyes can’t see / we don't know. What we know and see normally over rides what we hear and we are fully unaware of the process as it is the only thing we know..
Best,
Tom Danley
