Trouble Playing High Frequency 20khz - 100khz - I'm a little stuck

[AceOverlord]

I recently started setting up a project where I'm trying to record and playback high frequency sounds. I went ahead and purchased the Taket Batpure super tweeter.

Edit:
Didn't realize there was so much hate against super tweeters. Admittedly, I was a little curious when I first heard about them. But rest assured, I don't buy into the hype and I'm trying to set this up for some animal based research. Perhaps they caught on because they look pretty cool on top of speakers

• Yamaha km-208 (Frequency response 200khz according to the manual)
• klipsche SB1 bookshelf speakers
• Behringer umc202hd - USB Preamp with 192khz
• Laptop
• Taket Batpure - (3D printed cat shaped mounts just so they look cooler)

I've run into a few issues with the setup and I was hoping someone here might be knowledgeable in high frequency playback and recording.For my microphone, I used a pair of Primo EM258 Mono module. I 3D printed a holder for these and used some softer flexible filament to help with vibrations.

For the most part, the microphone setup is working from what I can tell, the capsule is recording frequencies all the way up to 98khz. Allegedly, I've only got one digital preamp. Recording and playback at the same time has introduced noise from playback into the recording.

I went ahead and made a test sweep that goes from 0 to 100khz, and recorded the output. When I play it back through the speakers and record it, I notice I'm not getting much sound from the supertweeters. I followed the manually and connected them inline to the back terminals of the bookshelf speakers. Cranking the volume to max, I'm not registering really any sound from them. I'm definitely getting frequency data on the spectrograph up to 100khz, however there is no significant volume. (less than the ambient volume of the room, which admittedly is pretty bad)

I've come to the following conclusions. There is something I'm overlooking, for example, maybe the amplifier has a huge frequency falloff over 20khz, or maybe even a lowpass filter (the exact range the batpure chimes in) (It also says in the manual that its rated for 20,000khz)

Or maybe the batpure supertweeter can't produce any noteworthy audible sound being low efficiency at 70 dB @ 1m. Here is what the recording of only the batpure speaker at 1 inch away looks like at max volume.

Note: the sharp frequency line is partially noise from the preamp. I need to isolate them to get a true recording.


The official high frequency equipment is so darn expensive, but my end game goal is to properly replicate a high frequency recording up to around 60khz. I don't necessarily need hi-fi sound on the higher frequencies, but somewhat stable volume.

I would really appreciate it if anyone can point out where I may have gone wrong or what I can try next. Trying to keep my budget to around 500$, but that may not be possible.

Notes: if I edit this post, they will be here.

I used stainless steel screws as terminal screws, however I did try wiring it directly with no improvement.
I also tried shorter speaker wire, around 3 feet.

 

[Curvature]

Adult humans generally can't hear above 15kHz.

Super tweeters are in most cases pointless. They once had a use when tweeters could barely reach 10kHz.

 

[Chrispy]

Why above 20khz? You are testing with dogs or something?

 

[Philbo King]

Strictly speaking, audio above 20KHz is not audio, it is ultrasonic. I'm absolutely unsurprised you can't hear it.

 

[Curvature]

Super tweeters are in most cases pointless. They once had a use when tweeters could barely reach 10kHz.

For example, the EV T35, introduced in the 1950s. https://www.ln271828.net/T35_analysis_comparison.htm

These days super tweeters are used mostly for research. Regular tweeters often extend into ultrasonic territory anyway.

 

[Chrispy]

Either that or OP believes in the ultrasonic bs in audio....

 

[Curvature]

There's this well-known paper showing measured energy of musical instruments well into the ultrasonic. https://ttsetup.com/images/Theres_l...f_musical_instrument_spectra_to_102.4_kHz.pdf

It's interesting for academic or engineering purposes. I can't imagine what one would gain by trying to reproduce it.

 

[Chrispy]

OTOH playing a frequency in those ranges has little to do with transducers capable of such....just a jerkoff audio thing mostly.

 

[AceOverlord]

I probably came to the right forum then, because I also don't think there is any benefit in a super tweeter other than you can make them look cool on top of a speaker. Although If I did believe the super tweeter hype, even just out of curiosity I would be feeling pretty discouraged right now. Can't say I'm for that. I am doing some experiments with my animal friends and have a few use cases. For one I might be able to use high frequency sounds to train my cat more efficiently, but that is a ways out. I have some theories I want to explore. Honestly with how hyped super tweeters were, I actually thought this was going to be pretty easy to setup.

Thanks for the paper on ultrasonic, I'll check it out.

 

[Chrispy]

I probably came to the right forum then, because I also don't think there is any benefit in a super tweeter other than you can make them look cool on top of a speaker. Although If I did believe the super tweeter hype, even just out of curiosity I would be feeling pretty discouraged right now. Can't say I'm for that. I am doing some experiments with my animal friends and have a few use cases. For one I might be able to use high frequency sounds to train my cat more efficiently, but that is a ways out. I have some theories I want to explore. Honestly with how hyped super tweeters were, I actually thought this was going to be pretty easy to setup.

Thanks for the paper on ultrasonic, I'll check it out.

I'd just forget the plus 20k thing, much more important things to pay attention to than that fantasy....

 

[AceOverlord]

I'd just forget the plus 20k thing, much more important things to pay attention to than that fantasy....

Cats can hear up to 70khz, so there will be some benefit in this research. Going off the frequency sweep I tried, forget 20khz, I'm only at 17.5khz lol.

 

[JSmith]

Hi @AceOverlord and welcome to ASR.

This on the product page... all misleading and false;

■　The tone quality is improved when you attach it to your
　　 speaker cabinet and connect it to the + and - terminals.
■　Music sound becomes more natural and realistic.
■　In TV sound comes speaking more realistically
　　from the person’s mouth with 3D feeling.
■　Dull headphones are vividly revived.

Anyway, at least they didn't cost you too much. You're on the right forum now.


JSmith

 

[Curvature]

I probably came to the right forum then, because I also don't think there is any benefit in a super tweeter other than you can make them look cool on top of a speaker. Although If I did believe the super tweeter hype, even just out of curiosity I would be feeling pretty discouraged right now. Can't say I'm for that. I am doing some experiments with my animal friends and have a few use cases. For one I might be able to use high frequency sounds to train my cat more efficiently, but that is a ways out. I have some theories I want to explore. Honestly with how hyped super tweeters were, I actually thought this was going to be pretty easy to setup.

Thanks for the paper on ultrasonic, I'll check it out.

I'm honestly not sure what's necessary to get this kind of HF response. Multiple devices in the electrical source chain need flat ultrasonic response, which is uncommon. The super tweeter directivity also tends be very narrow and beamlike.

Measuring this stuff is fraught with error for similar reason, since few microphones and their chain have flat response way up there.

Certainly none of the gear that comes to mind is cheap.

 

[sq225917]

Firstly, fine a true supertweeter that provides graphs of its measured output, the BatPur is not one of these. It's a gimmick for stupid Japanese audiophile.

 

[Speedskater]

There's this well-known paper showing measured energy of musical instruments well into the ultrasonic.

Those measurements were made very near the musical instrument.
Measurements made at a typical listener position, will show a very different picture.

 

[AceOverlord]

That paper on ultrasonics was very interesting. I've been recording a variety of high frequency sounds and was also wondering if the ultrasonics I was seeing were related to room acoustics or rattles. Thanks again for sharing, this answered quite a few questions I've had.

I can see why there is so much debate on the super tweeters now as well. I'm curious about your thoughts on these two remarks.

He quoted a study that the subjects brainwaves are altered due to the presence of ultrasonic sound and that participants rated the sound as better even though they couldn't say why. I would really have to look into that more to see if it was a less biased perhaps randomized blind a-b testing. (Oohashi et al)

Also the second study that it might alter your sense of gravity,( or I'm interpreting as balance) depending on the presence of ultrasound is interesting, not sure if that is a good thing or a bad thing. (. Lenhardt et al.)


Are high end dacs also a scam? I noticed a section for these on the forum. I tried a 100 dollar one a few years ago and couldn't blind test it, so I sold it.



Well perhaps I'm getting a bit off topic.


Firstly, fine a true supertweeter that provides graphs of its measured output

I think I'll go ahead and start here for now. I wasn't expecting everyone here to call out the taket batpure as a scam company, so I may as well trust that the documentation on my amplifier is correct, and that at 200khz it only loses 3db of sound. (Honestly not positive I'm reading it correctly)

I found this supertweeter from the 70s I believe. https://www.ebay.com/itm/116710382792 Its the Pioneer PT-R7

Here is the frequency chart, seems like a decent budget solution. It drops off pretty harshly after 50khz when off axis, but somewhat flat, especially compared to some alternatives I've found.

 

[Curvature]

(Oohashi et al)

A strange, insular group of researchers from Japan that are not taken seriously, as far as I've read.

 

[RDoc]

Be a bit cautious with all this. You may not be able to hear it, but the energy is still there. I was doing frequency sweeps with REM with a pair of Neumann KH120s where I couldn't hear anything in the high frequencies, but one of our cats was in the room and started crying and ran out of the room.

 

[raindance]

I would be inclined to test with a cheap piezo tweeter instead of a so-called super tweeter. However, I do suspect that the preamp portion of the amp will truncate the frequency response to 20KHz to avoid interference; the power amp might work up to 200KHz but it is unlikely they allowed this throughout.

 

[DVDdoug]

A couple more things...

I assume you are aware of the Nyquist Theory which says that the signal can't go over half the sample rate. And even though your interface might go to 192kHz, that doesn't guarantee that that the "audio" can go to 96kHz. Usually it can, but audio interfaces are intended for audio and they sometimes have additional filtering.

Obviously, it's "easy" to make analog electronics that goes way beyond the audio range and I believe your amplifier's specs. But frequently there's a DC blocking filter (and sometimes it's easier to build it that way) and often there is a low-pass filter to block-out RF and avoid any bad side-effects.

...This isn't a problem for you since you have a "good" audio interface, but any-old cheap soundcard can seemingly record and play at high sample rates even if the hardware isn't capable of it, because the drivers will up-sample or down-sample without telling you. (And sometimes the manufacturer isn't honest about it.)

You also have to be careful with power ratings. Speakers are rated for "normal program material" so a "100W" speaker is supposed to be safe with an amplifier hitting 100W on the musical peaks, with maybe 20W average. If you play 100W continuous test tones into it, you can burn it out! Even worse.... A "100" tweeter is rated only for the high-frequency part from a 100W amplifier which is much weaker than the midrange and bass. If you open a regular music file in Audacity and apply a high-pass filter, you'll notice the wave gets "smaller". the higher you go, the weaker the signal. It might seem misleading but a tweeter or super-tweeter manufacturer can legitimately specify a higher power rating by simply specifying a higher crossover frequency.

One thing that might help to protect the tweeter at extremely high frequencies is that the speaker/tweeter will probably become inductive (higher impedance at higher frequencies). That means less power with the same voltage.

Also, high frequencies are attenuated/absorbed in the air more than lower frequencies. Over short distances it shouldn't be a problem but from what I've read, with the distances in a movie theater there is a few of dB attenuation at the highest audio frequencies. (Of course they don't care about ultrasonics in theaters but it would be worse.)