[dongster]

1) Any earphone that shoots the sound directly into your ears would have to take HRTF into account. And it holds true for Custom IEMs as well. Say you are in an anechoic chamber with a set of stereo speakers that measure ruler flat. When you listen to music out of these speakers, certain frequencies are enhanced because of the interaction with your body, head and pinna. How do you recreate this enhancement of certain frequencies in an IEM? By tuning the IEM to inherently have these frequency bumps in its frequency response.

Regarding 'air movement to perceived loudness relationship'. You are heading into complex territory. dbSPL varies with distance and so when coming up with HRTFs, engineers try their best to eliminate as many variables as possible. One of the ways is; the dummy head is placed at a certain distance away from the speakers and a nominal loudness is chosen that is considered as moderate listening loudness for an average human. Now I do not know what is the right distance, because then you could start talking about Far-Field Monitors and Near-Field Monitors.

But rest assured, you can be confident that the engineers take utmost care when coming up with curves. You could google for Harmon Target curve and there is plenty of information out there.

2) The way things are recorded in studio is not simply done by 2 microphones in most cases. In a studio, there is a main floor and isolated chambers. Most of the band is placed in the main floor and multiple microphones are placed here optimally to record the timbral information of the instruments as well as the spatial, reverberation and decay cues. And the number of microphones and their arrangement is not anywhere close to replicating a human set of ears. The one exception to this is the binaural recordings.

Also keep in my mind, when it comes to stereo fidelity, IEMs lose to speakers by a huge margin because when you listen to speakers, your right ear gets the most of what comes from the right side and your left ear gets only a little and vice versa. But this is not present when listening to IEMs.

Perceived Spatial cues via Speakers = Spatial information in the recording + Spatial cues due to speaker distance and placement

Perceived Spatial cues in Earphones = Spatial information in the recording

Some DAPs and DACs try to compensate this by providing a feature called the cross-feed. Not sure how effective it is though.

My point being, saying that '2 membranes in your ear should have a direct synchronicity with the 2 diaphragm the microphone' is really oversimplification, except binaural recordings.

3) I am not sure if the recording engineer would consider the HRTF because the music they record will be played via all kind of sound systems such as mono speakers, stereo speakers, multi channel systems, headphones and earphones. I could be wrong though. Per my understanding HRTFs are predominantly used by headphone manufacturers and earphone manufacturers to tune their Headphones and Earphones to replicate what the eardrum perceives when listening to speakers.

But yes, you are right, IEMs have their limitations. Its just something we have to make peace with for the convenience and amount of micro-details they provide.

Forgot to address one point: "Say you are in an anechoic chamber with a set of stereo speakers that measure ruler flat. When you listen to music out of these speakers, certain frequencies are enhanced because of the interaction with your body, head and pinna. How do you recreate this enhancement of certain frequencies in an IEM?"

The "enhancements" are unintended mistakes, the goal of iem is to reproduce whats signals of the music file, but speakers.

 

[proedros]

hey guys , maybe this is a talk for the science forum ?

cheers

 

[dongster]

hey guys , maybe this is a talk for the science forum ?

cheers

Sorry bro, it stemmed from discussion about whether there are any flat CIEMs in the shoot out

 

[EagleWings]

I think comparing to speakers field of studies if not relevant. Because as you said yourself "engineers try their best to eliminate as many variables as possible".
All these factors such as HRTF, body, head and pinna, " dummy head is placed at a certain distance away from the speakers" room dont apply for IEMs. Lets forget recording for a moment, i have a computer generated frequency sine sweep, which has is just a pure signal, and let it drive a iem through the small pocket of air between iem tip to your ear drum, if you perceive (keyword) the whole course of the sweep to be even loudness, i would think its flat, and thus will reproduce (keyword) what ever signal that comes in in the purist definition of fidelity.
ofc, i get this doesn't mean its all enjoyable, but thats high fidelity, because in this scenario, the iem only reproduce what song contains, what the mixer/producer put in there.

granted there are factors such as eardrum/body resonances and ear canal effects, but i think it would be reasonable to say that if i get my iem tip as close to the ear drum as possible, u can neglect it, and but resonance is a constant, which u can do reasearch on like a 1000 people and average, i cant imagine large variance in this respect.
you can even do a model tunnel identical to my ear canal see its effects on frequencies.

and you take frequency sensitivity into consideration, bam, flat response
TLDR flat response=HIFI should theoretically be possible since air between iem tip and ear drum very small


As for cross feed, I understand the reasoning being each of your ear would hear both speaker channels. But, if the recording if made with 2 channel microphone, the left side channel would have recorded sounds from both sides of the sound stage. I think cross feed is only good for if the mixer only put sounds such as a synthetic tone in one channel but does not the other. but in this case it doesnt make sense to have cross feed, because there is no pin pointing on the sound stage, as that synthetic sound doesnt oringinate from a instrument on the stage.

As for how music are recorded with microphone, i think it would make the most sense to have 2 channels of microphones mimicking your 2 ears.

Hope to think what you guys think my theories on this complex topic.

Alright I think I understand where you are coming from. This line over here clearly explains the point you are trying to make and why you initially shared the ear sensitivity curves:

"Lets forget recording for a moment, i have a computer generated frequency sine sweep, which has is just a pure signal, and let it drive a iem through the small pocket of air between iem tip to your ear drum, if you perceive (keyword) the whole course of the sweep to be even loudness, i would think its flat, and thus will reproduce (keyword) what ever signal that comes in in the purist definition of fidelity."

Per your logic, an IEM if its tuned like one of those sensitivity curves, then Yes. When you play a sine sweep, you would perceive/hear the entire sweep at the same dbSPL level. And per your logic, that would be an IEM with FLAT tuning.

But the entire industry would disagree with you regarding the definition of the FLAT when it comes to earphones and headphones.

Per the industry, a FLAT IEM is one that is tuned similar to how your eardrum perceives a sine sweep when played on a set of ruler flat stereo speakers. There is a reason behind this. Let's forget speakers for now. Let's say you are in a room with your friend playing an actual guitar in front of you. When the sound waves from the guitar hit you, certain frequencies get enhanced due to acoustic interaction with your body (head, torso and pinna). You may call these enhancements 'unintended mistake' or whatever you want. But it does not change the fact that we humans all though our life have been perceiving sound with enhancement in these frequencies whenever we heard sounds coming from a source that is not placed close to your ears.

Now, here are raw measurements of some of the neutral earphones/headphones in the industry:

Etymotic ER4:


Shure KSE1500:


HD800S:
(See bottom grey curves)


Stax SR-009:
(See bottom grey curves)


Here is the rough Harmon Target curve derived through HRTF:


Do you see the pattern in these raw measurements and the Harmon Target curve? If you are still unconvinced, I'd suggest you start reading this article by Tyll from InnerFidelity here
https://www.innerfidelity.com/content/headphone-measurements-explained-frequency-response-part-one


And regarding your statement: 'As for how music are recorded with microphone, i think it would make the most sense to have 2 channels of microphones mimicking your 2 ears.'

Its just your opinion based on your own logic. There are reasons why not everyone does binaural recordings or 2 channel microphones although it would be a dead easy setup. And the information can be found online.

 

[Deezel177]

Is the carrot module to buy or just a prototype? And is there a version of the A18 without the apex modules, like the Zeus without the Adele?

I can't find the carrot module on the 64Audio website, but when I was at Music Sanctuary yesterday, they received a plastic bag full of them from 64Audio. You may want to ask if they can sell you a pair.

As for your second question, all I can say without a bullet to the head is... no, not yet

I think comparing to speakers field of studies if not relevant. Because as you said yourself "engineers try their best to eliminate as many variables as possible".
All these factors such as HRTF, body, head and pinna, " dummy head is placed at a certain distance away from the speakers" room dont apply for IEMs. Lets forget recording for a moment, i have a computer generated frequency sine sweep, which has is just a pure signal, and let it drive a iem through the small pocket of air between iem tip to your ear drum, if you perceive (keyword) the whole course of the sweep to be even loudness, i would think its flat, and thus will reproduce (keyword) what ever signal that comes in in the purist definition of fidelity.
ofc, i get this doesn't mean its all enjoyable, but thats high fidelity, because in this scenario, the iem only reproduce what song contains, what the mixer/producer put in there.

granted there are factors such as eardrum/body resonances and ear canal effects, but i think it would be reasonable to say that if i get my iem tip as close to the ear drum as possible, u can neglect it, and but resonance is a constant, which u can do reasearch on like a 1000 people and average, i cant imagine large variance in this respect.
you can even do a model tunnel identical to my ear canal see its effects on frequencies.

and you take frequency sensitivity into consideration, bam, flat response
TLDR flat response=HIFI should theoretically be possible since air between iem tip and ear drum very small


As for cross feed, I understand the reasoning being each of your ear would hear both speaker channels. But, if the recording if made with 2 channel microphone, the left side channel would have recorded sounds from both sides of the sound stage. I think cross feed is only good for if the mixer only put sounds such as a synthetic tone in one channel but does not the other. but in this case it doesnt make sense to have cross feed, because there is no pin pointing on the sound stage, as that synthetic sound doesnt oringinate from a instrument on the stage.

As for how music are recorded with microphone, i think it would make the most sense to have 2 channels of microphones mimicking your 2 ears.

Hope to think what you guys think my theories on this complex topic.

As someone's who's done quite a few studio recordings, individual mic-ing (i.e. Mic-ing up each instrument individually) may seem like it takes more time to set up, but it gives you the utmost control during the recording process and especially when mixing.

When you're recording the whole band together merely with two mics, each musician has to be spaced from the mics perfectly, and the instruments have to be tuned and performed such that no level balancing, EQ, reverb, compression, quantization, etc. need to be applied as any post-processing would apply to the entire ensemble. Basically, you have to "mix" before you even start recording.

Your point about the left microphone capturing some sound from the right side of the stage, and vice versa, is highly dependent on the mic's polar/pick-up patterns and any isolation the dummy head would provide (if you're going the Chesky route of binaural recordings). If the mic's pick-up patterns are small enough, and you take into account the isolation gained from being buried deep inside a rubber head (which is one of the best sound-absorbing materials by the way), then signals captured from the opposite side of the stage would be small enough to be negligible.

Of course, I don't mean to shut down any of your points, this is just my take as someone who's spent some time in the studio. Binaural recordings are fantastic for headphones/IEMs, but they're harder to get right than a twice-baked souffle au chocolat, and that's before you add the tempered chocolate shavings... creme patissiere on the side... strawberry flowerettes... wine to pair with... heated...

 

[subguy812]

They blinded me with science...

 

[Wyville]

Hey buddy, I've drawn a graph of UE18+ as it sounds to my ears. I say this bc there was a discussion on crincacle's thread about the universal version, and there are some graphs there. It seems to have some treble peakiness which is not present in the custom. So I emailed UE's director and asked if they were tuned differently, bc there is no harsness, sibilance, or even sparkle in the custom. It is one of the warmest and smoothest ciems I have. But he replied that with the custom they take the distance between the treble drivers and inner ear into account, so they can eliminate harshness.

That's surprising because I remember reading @twister6 review of the universal UERR where he felt the sound was very close to the custom version (if I remember correctly). Will check out the thread.

 

[LouisArmstrong]

How does the Tia Fourte rank against all these?

 

[jmills8]

How does the Tia Fourte rank against all these?

#21

 

[bvng3540]

#21

Do you mean #11 because this is for top 10 IEM

 

[13candles]

How does the Tia Fourte rank against all these?

Sublime. Simply Sublime ... Truly the best of the best of the best....

 

[ezekiel77]

Sublime. Simply Sublime ... Truly the best of the best of the best....

!!!!

So if I talk about Kate Upton in this thread will she appear too??

 

[jmills8]

.

 

[ranfan]

Scary science-y stuff there

 

[Kerouac]

They blinded me with science...

Haha, good ol' Thomas Dolby (She blinded me with science)

But hey, where would we be without some science afterall?