[mrconfuse]

Etymotic sells the ER4S and the ER4P-T, the ER4S is 100 OHM while the ER4P-T is only 27OHM but it includes a P to S cable which is supposed to make the ER4P-T behave like the ER4S. Below is the exact wording from Etymotic in regards to the cable

 
Can't decide between the ER•4PT and the ER•4S? You have both with this adapter. Adapter is included with the ER•4PT.

 

The inline adapter converts the response accuracy of the ER•4PT from 86% to 92%.

 
Here's the problem, some in the forum have stated that you cannot add impedance to an IEM via an adapter. What you're really doing is adding more impedance to the source. Based on this there is no way the P to S adapter will make the ER4P-T behave like the ER4S. Then I called Etyomotic spoke to Support and they said that the P- S cable does add impedance to the IEM. 
 
So who's right? Is Eytomotic as a company completely wrong and the forum is correct or the 'experts' here wrong? 
 
To further confuse the issue, here is a comment from 2015 regarding these 2 headphones 
 

 
 

  Okay, but is the er4s a better choice ? I have been hearing that er4s has a more refined sound...
And does er4s = er4pt + adapter p to s ?

 
"Better" depends on your personal preference. "P" has more bass, some like the highs of the "S".
 
Yes, "4S" = "4P" + "P-to-S adapter". The only difference is the "S" has a 75 Ω resistor in the Y-pod (well, 2 resistors - 1 per channel). "4PT" just means that the adapter comes in the box.

 

 

[MindsMirror]

The er4p has a 27Ohm driver and 75Ohm resistor in its cable which can't be removed. The er4pt has the same 27Ohm driver with the 75Ohm resistor in a removable adapter instead of in the cable. Electrically they are the same if the adapter is connected.
 
It's a matter of perspective. From the source's perspective, the load that it is driving is higher impedance. From the perspective of the IEM's driver, it is being driven by a source with higher output impedance. If you say that the 75Ohm resistor belongs to the IEM, then yes, it's adding impedance to the IEM. If you say it belongs to the source, then it's added to the source. The er4s has the resistance built into its cable, so most would say it belongs to the IEM since it can't be physically separated from it, but otherwise electrically and functionally they're exactly the same.

 

[mrconfuse]

If you say that the 75Ohm resistor belongs to the IEM, then yes, it's adding impedance to the IEM

 
From this view everything works as intended. The impedance is higher than the source.  
 
 
Quote:

From the perspective of the IEM's driver, it is being driven by a source with higher output impedance

 
 From here, you going to have an impedance Mismatch because now whatever the source is it's going to be +75 OHMS more with the adapter added on. Aren't you? 

 

[ClieOS]

  Etymotic sells the ER4S and the ER4P-T, the ER4S is 100 OHM while the ER4P-T is only 27OHM but it includes a P to S cable which is supposed to make the ER4P-T behave like the ER4S. Below is the exact wording from Etymotic in regards to the cable
 
 
Here's the problem, some in the forum have stated that you cannot add impedance to an IEM via an adapter. What you're really doing is adding more impedance to the source. Based on this there is no way the P to S adapter will make the ER4P-T behave like the ER4S. Then I called Etyomotic spoke to Support and they said that the P- S cable does add impedance to the IEM. 
 
So who's right? Is Eytomotic as a company completely wrong and the forum is correct or the 'experts' here wrong? 
 
To further confuse the issue, here is a comment from 2015 regarding these 2 headphones 
 

 
That's like asking whether who is right - the first person who say the glass of water is half empty or the second person who say the glass is half filled with water. The physical fact itself doesn't change, though the prospective of description does.
 
So your question is more like - do you define 'the IEM' as purely the balanced armature driver itself while the cable (including the resistors inside or the added impedance adapter) is part of the extension of the source's headphone amp circuit, or do you define 'the IEM' as the BA driver with the cable / adapter where the source's headphone amp stops at the headphone jack? Neither way of definition really change how the setup as a whole or its resulting sound, thus whatever way of saying things is mostly just an argument of semantics - though I think most will probably say 'the IEM' is that whole thing that plug into the headphone jack, not just the transducer.

 

[mrconfuse]

That's like asking whether who is right - the first person who say the glass of water is half empty or the second person who say the glass is half filled with water. The physical fact itself doesn't change, though the prospective of description does.

So your question is more like - do you define 'the IEM' as purely the balanced armature driver itself while the cable (including the resistors inside or the added impedance adapter) is part of the extension of the source's headphone amp circuit, or do you define 'the IEM' as the BA driver with the cable / adapter where the source's headphone amp stops at the headphone jack? Neither way of definition really change how the setup as a whole or its resulting sound, thus whatever way of saying things is mostly just an argument of semantics - though I think most will probably say 'the IEM' is that whole thing that plug into the headphone jack, not just the transducer.

I guess the answer I'm really looking for is, does the adapter cause a mix match in impedance. Forgetting about semantics

 

[jfoxlim]

I always confuse with impedance, in my opinion is the adapter adds impedance like adding pressure in the hose.

 

[mrconfuse]

yeah, i'm confused that's why i'm hoping all the knowledgable folks can chime in on this. At the end of the day do the physics cause a mix match or not. 

 

[MindsMirror]

  yeah, i'm confused that's why i'm hoping all the knowledgable folks can chime in on this. At the end of the day do the physics cause a mix match or not. 

No. Typically companies intend for their headphone to be used with low output impedance, so they tune them to sound the way they want using a low output impedance source. Low output impedance is good because it avoids wasted power, you need almost twice the power to drive the er4pt with the adapter than without it. Otherwise there isn't much wrong with having that impedance there if they tuned it to sound good that way.

 

[mrconfuse]

  No. Typically companies intend for their headphone to be used with low output impedance, so they tune them to sound the way they want using a low output impedance source. Low output impedance is good because it avoids wasted power, you need almost twice the power to drive the er4pt with the adapter than without it. Otherwise there isn't much wrong with having that impedance there if they tuned it to sound good that way.

would the same results be the same if say your source output was 20 OHM (as an example) and now you're using the adapter with the IEM. 

 

[HiFlight]

I always confuse with impedance, in my opinion is the adapter adds impedance like adding pressure in the hose.

When pairing a multi BA IEM with a high impedance source, each of different drivers can have response curves that differ from that of the designers intent. By adding additional load impedance, the effects of the individual response curves can lessened. This will, of course, change the overall SQ of the earphone, making it closer to the design tuning which may or may not suit the preferences of the listener. While reducing the effects of the impedance mismatch, adding more load impedance is offset by the increasingly higher power requirements required from the source.

Too much load impedance will result in lower volume being delivered to the load (IEM) and if one tries to compensate by increasing the volume there will be less power available for transients and the likelihood of audible distortion will be greatly increased.

It is probably best to select a source with an output impedance that is appropriate for your desired phones or if you already have a high output impedance source, pick phones with an appropriate impedance to match. The generally accepted guideline to minimize unwanted coloration due to impedance mismatch is an 8 to 1 or greater ratio of load to source.