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An Exploration with the Theoretica Applied Physics BACCH-BM Pro Binaural In-Ear Microphones

  1. miceblue
    Hello fellow binaural-microphone lovers, or, welcome to those who are new to this type of recording. This is a long overdue post that I've been meaning to publish, but alas I kept getting delayed. I wanted to create this thread to give a nod of approval from me for the BACCH-BM Pro microphones that are made by Theoretica Applied Physics.

    Like with all binaural audio recordings, headphones or earphones are required. ^_^





    First of all, thank you to @jude and @AxelCloris for letting me use these microphones for a few weeks. It was interesting trying to come up with some tests to demonstrate the performance of these microphones compared to my Sound Professional SP-TFB-2 microphones, which I have been using for many years now for an assortment of purposes: ASMR videos on YouTube, sound tests at local meetups, general '3D Audio' examples.

    Frequency Range: 20 Hz - 30,000 Hz (+/- 1 dB, w/ EQ)
    S/N Ratio: re. 1 kHz @ 1 Pa (94 dB SPL) 67 dB
    Sensitivity: -35 dB re. 1 V/Pa (±3 dB); 17.8 mV/Pa
    Equivalent Noise Level: 27 dB(A)
    Phantom Power: +48 V

    Frequency Response: 20-20,000 Hz
    Signal To Noise Ratio: Standard Sensitivity 60dB/High Sensitivity 62dB
    Open Circuit Sensitivity: Standard Sensitivity -42dB/High Sensitivity -30dB
    Maximum Input Sound Level: 105dB/120dB
    Dynamic Range: 81dB/96dB
    Power Requirements: 2-12 VDC "plug in power", power from Battery Module, or phantom power with power converter adapter

    For all of my recordings below, I used a Zoom H4N Pro as my recorder. Unless otherwise stated, these were at 24-bit/96 kHz. Each file has an amplified waveform via Audacity such that it doesn't clip, and each file has ReplayGain tags in the metadata in case anyone wants to do an ABX test with Foobar or something similar.

    Honestly, I had never heard of Theoretica Applied Physics, nor the BACCH moniker in my search for binaural content. It was only until CanJam SoCal 2017 that I discovered them. The representative there gladly let me record a demonstration between the BACCH-BM Pro and the SP-TFB-2 at the CanJam showfloor right then and there. For both sets of the recording, I had the binaural in-ear microphones in my ear, sitting down on a chair, and the representative walked around me.

    Unfortunately I don't have the original audio files...
    ...but I think the YouTube video still demonstrates how effective the BACCH-BM Pro mics are at capturing the space of the large venue, as well as capturing the details of the people and sounds around me.

    As for the time I got to borrow the BACCH-BM Pro microphones from jude, I decided to visit The Source AV, also in SoCal, since they have a variety of nice and quiet theater rooms to do tests in. Thank you to @TSAVAlan for helping me set up the theater room for the test demos below.

    I first did a multi-channel movie test since this could help the listener understand what the room might sound like. Like the theater room was in-person, there is a lot of bass and bass rumble. I chose this scene from 'Guardians of the Galaxy 2' because it has a nice combination of loud and quiet moments, as well as sounds presented in the 5.1 channels. I know these microphones are meant to go inside of one's ear, sitting at the pinnae. However, I have always found recordings done in this way to sound a bit weird to me relative to how I perceived them in reality. A good example of this is when I use these microphones to capture sound from various headphones: the resulting audio ALWAYS sounds waaaay off. Because of that, I did two types of recordings for this first test: one with the microphones placed in a foam dummy head, and another with the microphones placed in my pinnae. If everything was theoretically correct, the recordings from the microphones placed in my pinnae should sound more accurate, to my ears at least since they were placed into my ears.

    This is what the room looked like:


    This is where the microphones were placed. If the microphones were in my ears, I slouched on the couch to a similar height as the foam dummy head.

    And here is the associated equipment in the room:


    BACCH-BM Pro in the foam dummy head (FLAC, 1:47 in length, 28 MB in size):

    BACCH-BM Pro in my pinnae (FLAC, 1:47 in length, 29 MB in size):

    SP-TFB-2 in the foam dummy head (FLAC, 1:47 in length, 30 MB in size):

    SP-TFB-2 in my pinnae (FLAC, 1:47 in length, 31 MB in size):

    At least for me, the BACCH-BM Pro microphones, again, captures the space of the room much more accurately than the SP-TFB-2 microphones. To me, the SP-TFB-2 has always seemed limited in its ability to present sound in front and behind me, as well as convey the sense of vertical space. The BACCH-BM Pro to me fills in those gaps much more. It's still not perfect, as Gamora's voice should sound more centered than it is in the recording, but it's still much better than the SP-TFB-2's center imaging.

    The second test I did was place both microphones in the foam dummy head, placed the head in the middle of the room, and walked around the room at various positions and at various distances. This kind of test is what one might expect for a binaural test recording, not unlike those of Chesky Records for the 'Dr. Chesky's Ultimate Headphone Demonstration Disc' album.

    Here was the setup in the room:
    ^ the random objects on the floor and table were markers for distances and angles

    My microphones' setup:

    The left-side of the foam dummy head:

    The right-side of the foam dummy head:

    BACCH-BM Pro in the foam dummy head (16-bit/44.1 kHz FLAC, 6:00 in length, 28 MB in size):

    SP-TFB-2 in the foam dummy head (16-bit/44.1 kHz FLAC, 6:00 in length, 31 MB in size):

    Again, I think the BACCH-BM Pro microphones sound crisper and more detailed, as well as being able to convey my positions much more accurately than the SP-TFB-2 microphones.

    I think from all of the tests I've heard with the BACCH-BM Pro, I'm convinced that they are a superior microphone to more accurately capture the environment they are recording. Rightfully so too since these microphones are 33+ times more expensive than the SP-TFB-2. Specification-wise, they may seem like they're on a much more level playing field, but as you can hear from the recordings, they are more different than alike. It has been an interesting experience getting to hear the two, literally, side-by-side in a controlled environment. This experiment has opened my eyes for a higher-fidelity in-ear binaural microphone that fills in the gaps that I always thought were missing from the SP-TFB-2 microphones. What's weird to me though is that the SP-TFB-2 files are all larger in size than the BACCH-BM Pro ones. Maybe it's because the SP-TFB-2 recordings have more noise?

    BACCH-BM Pro (foam dummy head)

    BACCH-BM Pro (my pinnae)

    SP-TFB-2 (foam dummy head)

    SP-TFB-2 (my pinnae)

    Walking Demos:
    BACCH-BM Pro


    Anyway, will I buy the BACCH-BM Pro microphones? Eeeeeeeeeeh.....maybe not. I don't use my current binaural microphones nearly enough to justify the price, even if that price means I get much better fidelity of sound. For what I use the microphones for, I would rather spend my money on a 3DIO binaural dummy ear microphone.

    Thank you again to jude for generously allowing me to test these microphones, I really appreciate it! I hope these binaural audio demos inspire some discussion as I think binaural microphones in general are underappreciated. I have always thought '3D' audio was fascinating and it all started with the infamous Cetera Virtual Barbershop.

    ^ wow that video is from nearly 12 years ago!
    Last edited: Feb 5, 2019
  2. Muinarc
    Awesome write-up @miceblue ! I wish we could get more content in the binaural space, some albums from popular acts and genres would be nice. I'd love it if someone could take these mics to a concert that has a great house mix.
  3. miceblue
    Albums outside of Chesky Records would be nice to hear. Something a little different than the typical Chesky sound.
  4. szore
    I listened to some of the Chesky recordings and was very impressed!
  5. misteral201103
    Interesting timing! I just got my Hooke verse and will be writing a review soon. Will give your recordings a listen to compare.

    Agree that more binaural albums would be great, looking forward to recording some concerts when I get the chance (though obviously I can't distribute!!)
  6. SHAMuuu
    I remember watching this dude's channel, mostly b/c he seems hardcore enough to go and sit through those RMAF conferences. Real hardcore.

    I was scratching my head wondering how he recorded th mysphere for his video

    now i know !

  7. miceblue
    Ooooh the Hooke Verse! They had a booth at the NAMM show! The Bluetooth transmission seems pretty interesting since going wire-free would make things a lot easier to manage.

    That was one of the issues I had with the BACCH-BM Pro mics: they required phantom power, which means they carried the insane bulk of XLR jacks (1x 4-pin XLR, and a 4-pin XLR to 2x 3-pin XLR jack adaptor). It's not practical at all to bring it to places even though the microphone capsules themselves are tiny. The SP-TFB-2 just uses a 3.5 mm jack, so it's much more portable in that regard.

    Yup yup, that's how I recorded the MYSPHERE audio! I had the binaural microphones placed in the same dummy head. I did try to have them in my ears, but as stated in the first post, the recorded audio ended up sounding way off from what they should sound more like.

    And yup, I bring the SP-TFB-2 microphones to the CanJam seminar sessions to make binaural recordings. I dunno, once you hear things in binaural, it's hard to go back to traditional stereo or mono recordings even if it's just a seminar in a medium-sized room.
  8. SHAMuuu
    Well from my experience, you can get that whole 360 with almost any headphone from 3d simulations on youtube so its defo the recordings. But the problem is all the music I like is older and were not recorded that way.
    I've heard some "audiophile" music, which are crystal clear and nice, but it also sucks at the same time relatively speaking.
    The Chesky stuff is kinda interesting to listen when testing headphones.

    The truth of headphones is at a certain point, its just better to listen to speakers or go to a live event :p
    Even if they get the 3D aspect right, they can never get the Bass immersion right via vibrotactile/bone conduction feedback from whole body due to limitations of surface area of electrodynamic transducers , or planar or electrostatics.
    Headphones can only blow another headphone out of the water, but i've never been blown away by a headphone or iem vs speakers 2.1 or car audio system.

    You bring some great content on your channel and i thank you very much for sharing. Your passion is infectious; which i'm not sure is a good or bad thing :p

    Keep it up buddy
  9. szore
    Don't mean to butt in, but I take issue with the car stereo. Your listening to speakers inside a rain barrel. I have AndromedaSS with A&K1000M, blows any car stereo out of the water.
  10. SHAMuuu

    Ofc you can butt in, the more the merrier.

    I think car audio is much more complex yes!
    I was fortunate enough when younger to spend sometime in car audio related work and have heard some good and bad in the exotic cars, which didn't have much SPL but more focused on SQ.
    I was more SPL when it comes to car audio, so you will have to keep that in mind.
    Also SQ and SPL aside, it is more immersive, and one doesn't really focus on all the tidbits like when using iems and/or headphones. Just music enjoyment.
    Its very difficult to beat the experience of being young, on a date, and cruising with a nice sound system. There are enough distractions than to focus on the timbre :p

    The best vehicle I personally found is a Ford Excursion as it is build like a tank and can be made into a little club :D

    I'm curious to know which car, and the components you listened to that cannot beat your iems.
  11. szore
    My first car was a 1978 Pontiac LeMans that I bought off my sister for $400 when I was 17 and working up at the Roy Rogers in the mall. I went up to the flea market up on Sunrise Hwy and got a pair of killer 3 way speakers and a 20 band GE for about $175! I wired them up with lamp cord, and twisted them onto the wires coming out of my Teac tape deck. Man, that was one sweeeet ride!
    Last edited: Feb 8, 2019
  12. SHAMuuu
    I can see your point on iem vs car stereo for something like timbre, imaging, vocal intimacy.
    I can appreciate headphones (i'm on head-fi after all) and it is sweet to hear Roy Orbison on stage with just his guitar or Jewel etc. etc.

    But the potential to reach high fidelity is not so farfetched. Sure a cheap setup in a Honda Accord or something will be pretty poor fidelity wise, but higher end cars with better road noise attentuation have greater potential should the body be solidly dampened. Good seals on windows and doors so there is a fixed air volume to work with.

    Some hardcore guys will move away from door speakers, and use strategically positioned component systems to mimic a 2.1 setup. Door panels and roof can be modified for reflective purposes to one's liking.

    Ofc these costs are astronomical when talking about a vehicle. And a lower end car with a high end system will sound like garbage due to poor attenuation of road noises, air seal issues, and weird geometric obstacles like land whales.

    But in a sense, good components are available, and its a matter of tweaking the fixed volume "box."

    I don't know if i've ever seen a LeMans, but they give me 80s Regal vibes , some gangsta dope slinging in the alley vibes. :D
  13. szore
    All kidding aside, my experience of high-end car stereo systems is limited to non-existent. There have been several times where someone had a nice car with an expensive stereo and they played it for me and all I heard was BOOM BOOM TWEET TWEET with a lot of distortion and zero soundstage and subtlety . If they actually have the technology nowadays to mimic a high end, 2 speaker or 2.1 speaker floor system that's impressive, but I highly doubt it. But my experience is limited, like I said. Between my player and my IEM's, it's about a $3,600 investment, and they sound amazing... I am constantly amazed at how good they sound.
  14. SHAMuuu
    Ha! You're absolutly right.

    It's possible, but you need to start with a Rolls Royce or something with a dead silent cabin/ drivetrain before even the components. Loud engine, cabin noise, air leakage most people will not spend the $$$ (most likely thousands for the custom work) to tune/fix, and not have speakers in doors etc.

    And in terms of accuracy, I would think IEM's skipping the ear reflections would most likely yield the most desired results in the midrange, treble anyway.

    I can absolutely see where you are coming from!

    IMO/YMMV etc etc :D

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