The things which effects the sound stage directly
1.annular nodes/ Undampness of driver
2. THD+N(total harmonic distortion)
3. IMD(inter modulated distortion)
4. TUHD(total inharmonic distortion)
5. Saturation current(voice coil saturation)
6. Phase (phase)...
1. Dampness of driver decide how tight the driver moves at specific frequency, thus reducing the range of dip( Q factor or widht of peak), so the peak area reduces, leading some clarity of instruments. It is like taking the veil off and good transient response. Damped driver dont show annular node.
2. THD+N is harmonic distortion or fundamental distortion happening when you play your music. That distortion is fundamental with the fundamental tone. This can warm up, or colour music. Clearing it up, cleanse the background image, and gives blackness or space to it.
3. Intermodulation (IM) or intermodulation distortion (IMD) is the amplitude modulation of signals containing two or more different frequencies, caused by nonlinearities or time variance in a system. The intermodulation between frequency components will form additional components at frequencies that are not just at harmonic frequencies (integer multiples) of either, like harmonic distortion, but also at the sum and difference frequencies of the original frequencies and at sums and differences of multiples of those frequencies. The same dipping effect also happens and is also a part of IMD. IMD is real reason of the staging issue.
the stage or resolution or rendering from single driver can be lower compared to multidriver is because of dipping of frequency in burst of signal
if 20kHz and 18KHz burst together in sample tone, it will compensate the sound at 20-18= 2kHz. It will dip that 2kHz slightly within the impulse. This happens to fast to notice, so change in frequency response become unnoticebale, but the lower dB can lower the render of stage and reality. That is physical nature of diaphragm to protect from rupture. Studies are still going on
For example, slow acoustic or classical song with vocal and few instrument sounds bigger than complex passage of song, which kinda gets compressed.
in multi driver, the tweeter when bursts 20kHz and 18kHz, doesnt play 2kHz. That is played by mid range driver, so no loss of signal . this leads to bigger presentation on multi driver. That may explain the crossover theory. multi driver helps in field diffusion, distortion figure too
4. TUHD is inharmonic distortion or over distortion happening due to overtones. Like PVC tubing vs titanium etc.
Driver produce some overtone depending to its material buildup. Thats what make them different sounding. TUHD also helps user to differentiate easily between loudspeaker driver. It can make a artificial stage or completely collapse it. If you remove TUHD factor, you get very clean overtone which supplements the fundamental tone, building up the echo nature and room size. Some soundstage have no walls is due to this.
5. Saturation threshold increase and total realtime saturation reduction gives driver more freedom to not limit within a freq spectrum, and crossing with this sort of nature reduce every distortion factor immensely.
6. Phase is final and most important. Phase shifts can cancel frequency, but quick phase shifts do nothing on response. What they do, is make the human brain compensate for it, thus leading to a brain information lag. A perfect phase IEM will always construct a proper instrument position in a space called sound image. This also reduces headaches due to longer listening period and reduces ear damage.
When brain trys to compensate, it tightens the eardrum more, creating fatigue sometimes.
Hope this may help
And now finally is the tuning of IEM.
After all this, a specific tuning always sounds larger than other. All the soundstage values lie in
Low end harmonics
20Hz to 40Hz(depth) subbass rumble
40Hz to 70Hz(intensity or reverse z axis, inside the ear...important as you have to build the same stage inside out, for a complete experience) ear licking bass..
Mid range harmonics
The 2k 3k peak. Hit and trial increment or decrement, prefer damped decrement as it space out thing and relax the vocal harmonic range.
Ear resonance(universal design iem only)
Ear canal length is in between 27mm to 32mm
Which gives an average of 6kHz and 11.2kHz resonance with normal earbuds.
Damp and notch these out somehow and enjoy the super stage.
Courtesy from Ocharaku (total respect)
Air
Lol.
From 8kHz to unknown Hz
Lower treble freq range decide grain and structure of air. Mid treble range decide the length of air. The time at which it is present after the tone is finished(gives the sound stage effect) and higher freq decides the echo of air( Sennheiser HD800)
Decay
This also do a lot of thing, but I am studying that factor. I will update it here
all the experience coming doing social service for old age home(making hearing aids for them free of charge)
I use comsol multi physics
With pipe module, and acoustic module with muffler addon
Hope my posting doesn't offend the diy community here with theory and lecture
And please correct me if my wrong at some point
I am still learning a lot(basically amps and driver)
