@SaintSovereign saw your post on the ‘Season 4: Into The Wonder’ thread concerning bone conduction, and thought I might as well share my thoughts/experiences on this thread, as you suggested.
So, for everyone reading, I’m an audiophile, meaning I basically love music, and as an extension of that passion, I try to find the best equipment with which to listen to that music, so that I can hear the music at its best, and notice loads of tiny details in the songs which make them come even more alive or intensify the feeling.
I’ve also been a semi-pro reviewer for such products for many years.
Some explanations first, which will hopefully assist any of the thoughts I share to make more sense, especially if you are new to or know little about the audiophile world or music technology.
Note: these explanations are mostly generalisations, may contain errors or oversights, and are designed as an aid to help people to understand and judge what lengths they might be willing to go to in order to get the best out of their subliminals here (and perhaps their own music collections too).
I don’t claim any deep expertise, and these are general rough summaries of quite deep areas of knowledge! There’s forums online if one wants to go into such fine details:slight_smile:
Some people have big Hi-Fi systems in their homes with speakers, some use headphones (with or without an amplifier).
Technology has enabled us to have portable systems with Hi-Fi levels of sound quality.
Think iPods and earphones, only with much much better sound quality. We call this ‘Portable Audio’
My focus has always been on portable audio.
As a side note, file quality can also make a difference, if you have both decent equipment and have trained yourself to hear the differences (or are naturally gifted in that area lol).
So a 320k mp3 file should sound notably better than a 128k mp3 file.
Now, mp3 is a ‘lossy’ format; the original digital data from the song are compressed to make a smaller file size, and in the process of doing so, the algorithm cuts out data that it judges as being unneeded.
But in fact, this might be tiny details in the song which are now lost.
I’d speculate that subliminal audio input is exactly the kind of thing that would get cut from a standard mp3, since it would be regarded as redundant file data, since the conscious mind can’t hear it.
It should go without saying that of course SubClub would not be doing that with their own mp3’s!
There’s also another format, FLAC (Free Lossless Audio Codec) which does a similar thing, but without any loss of original data. So again, a good FLAC file should - with good gear and practice - sound better than an mp3 file, and you should be able to notice more small details in songs you love.
Note that FLAC files are one of the options you can choose when selecting a custom sub in the Q store 
And the rabbit hole goes yet deeper, with ‘Hi-Res’ FLAC files (normal FLAC is CD quality, aka 16 Bit). But there’s Hi-Res FLAC files, which are 24 Bit and this basically means they cram even more detail and data into the audio file, so again, you may be able to hear even more details and everything may sound more clear.
So, using a comparison to video formats with which you will hopefully be familiar, you can think of 320k mp3 files as Standard Definition (SD), 16 Bit FLAC as HD, and 24 Bit FLAC files as 4k/UHD.
Some music players - think iPods, but in the audiophile world we call these DAPs (Digital Audio Players) - some of these contain software/hardware designed to upscale lower resolution music to sound like higher resolution music (the easy analogy would be using AI or other tech to upscale standard definition video into HD or 4K video).
I never use mobile phones to listen to music, but I imagine there might be apps for the phone that can do this. Just as with video tech, the results of this upscaling will depend on the original quality of the file being upscaled, as well as the quality/sophistication of the tech being used to do the upscaling.
So, with this preamble out the way,…
I personally use a DAP (think iPod, but better) to play the subs; usually my Sony WM1Z or a Lotoo LPGT (or my Sony ZX300 when on the go, as it’s super light and portable). Both Sony DAPs have been hardware and firmware modded for improved sound quality. All of these have a selectable option where it will upscale the audio to sound like Hi-Resolution (HD) audio. So an mp3 or FLAC file can be made to sound as if it’s a 24 Bit FLAC quality file.
For IEMs (In Ear Monitors; that’s just the pretentious audiophile way of saying ‘earphones’ lol) I have settled on the 64 Audio Volür, and Campfire Audio Dorado 2020 if I have to listen to subs whilst I’m on the go (e.g. in cafe’s, on public transport, etc. I try to do my listening in silence at home however).
I have also used Fir Audio Xe6 and iBasso MEST Mk III, the latter of which features BCD’s (Bone Conduction Drivers), i.e. bone conduction technology.
But there are earphones from $30 to $10’000 and any of the available price brackets should contain some earphones which will be able to enhance your music and subliminal listening to some degree.
So look, even as an audiophile, listening to music, it’s been a journey, gradually upgrading to better and better quality equipment, as well as learning to listen better, training my ears as a reviewer to listen to two different earphones back to back and pick out the differences in their sound quality and the way in which they affect the sound of the music.
Doing this for subliminal audio files is a rather different matter, but fortunately, the existing knowledge can be used to make this easier.
In the world of audiophile earphones, you could make a (very) broad generalisation and classify earphones into two categories: ‘Neutral/Reference’ and ‘Musical’ (in the sense of being engaging and fun, rather than in the sense of musical theatre lol).
Note that when reviewing this gear, we tend to focus on 3 parts of the audio spectrum; the bass, the mids, and the treble.
A ‘musical’ earphone is one where the sound is coloured; the bass may be cranked up a bit (or a LOT), the treble might also be emphasised more, in order to balance out the bass increases and make it all sound more airy or detailed.
Some have an emphasis on upper mids, which can accentuate female vocals, to make them sound beautiful, and others might emphasise the lower mids, adding gravel and grit and depth to male vocals, guitars and musical instruments generally.
So even within the classification of ‘Musical’, there are IEMs (earphones) that may emphasise bass and lower mids, whilst others might be more delicate and ethereal sounding, emphasising upper mids and treble. Which one you prefer will probably depend on which genres of music you most commonly listen to.
With ‘Neutral/Reference’ earphones, the idea is just to aim for pure musical fidelity; letting the sound be as high quality as possible, with minimal ‘colouring’ of the sound. The goal is to just hear the music as it is presented on the CD/mp3/FLAC.
So tying all this together, what I’m trying to say here is that there’s a difference - to some extent - between selecting audio equipment for music listening and selecting it for listening to subliminal audio.
With music, I listen to all kinds of earphones, and tend to favour (most of the time at least) ones that are more ‘musical’.
However, when it comes to subs, especially given that I have only limited knowledge about how they work, I will tend to focus on earphones that are more ‘Neutral/Reference’ in sound signature.
Why? Because I have no idea what effect (if any) it might have on listening to a subliminal audio file if I were to use an earphone that cranked up the bass and reduced the treble, for example.
A Neutral/Reference earphone on the other hand, has a stated goal which matches the intention when listening to subliminal technology, namely to hear the file exactly as it was originally recorded (or as close to that as we can get).
Most of my earphones would be classed as musical (with a variety of different tunings and emphases within that category). My 64 Audio Volür is probably the most (comparatively) neutral/reference of the best earphones that I frequently use.
Also, it has some emphasis on faithfully reproducing high frequencies with clarity and detail, so again, it seemed like a good choice.
Generally, if you’re looking to buy good earphones or headphones for listening to subliminal audio files, I’d look out for descriptions such as ‘neutral’, ‘reference’, ‘clarity’, ‘crystalline’, ‘balanced’… stuff like that.
Further, whilst I use the ‘upscaling’ tech in my music players for listening to music (especially for songs where I’ve only been able to buy them in mp3 or standard FLAC format), I choose not to use that for subliminal audio files, again because I have no idea what the upscaling algorithms would make of the ultrasonic parts embedded in the masked file.
Finally, regarding bone conduction technology, I’ve used it with subliminal audio files, but not enough to really know whether it was making any difference.
Note that with conventional music files, I noticed that it seemed to help separate out details and aspects of the music (e.g. bass lines would be more distinct, there’d be more space between the instruments, just as you’d find on a live stage). It also increased the tactility of the music; you could literally feel the thunk of piano keys being struck, or guitar strings being plucked etc.
But what effect would this have on subliminal audio? I have no idea.
The answer might be ‘none whatsoever’; note that there are various manufacturers and models of BCDs (Bone Conduction Drivers). When an earphone includes bone conduction tech, note that some of the BCD’s on the market only cover specific areas of the frequency spectrum, e.g. just bass, or bass and lower mids. Some cover the upper parts, and some are ‘full spectrum’.
But whilst some earphones explicitly state that they cover the ultrasonic frequencies and represent them faithfully, I don’t know if any of the bone conduction drivers on the market currently do this.
And I’m currently too busy to research that right now lol.
So you might have an IEM (earphone) with bone conduction technology included in it, which covers the full audio spectrum (and ultrasonic) with its regular drivers (e.g. ones like dynamic drivers, balanced armatures, planar magnetic drivers etc), but where the bone conduction drivers only cover the bass frequencies, or just the audible frequencies but not ultrasonic.
So I’d say this is an important thing to consider if you’re wondering about using bone conduction tech with subliminals
Ok, that’s more than enough for now lol. Just let me know if you have any questions or whatnot