This is a review and detailed measurements of the Panasonic RP-TCM-125-A in-ear monitor. I purchased this from Amazon and costs US $15.10 including prime shipping (retail $19.99). I picked this because it was used in Olive et al. research (see below). Yes, folks, we are getting into measurements of IEMs! 
I have a bunch which have come for review and I constantly get offers to test more. So I finally allocated a bit of time to see how my GRAS 45CA fixture can measure them and to my delight, it was dead easy, far more than any headphone I have measured! Time will tell however as I measure more whether this is typical or not.
To that end, this is also an introductory thread on IEM measurements. So go ahead and say your peace now and here instead of polluting future review threads.
One "problem" with IEMs is how to take pictures of them so I apologize for the crappy nature of this one:
The dual panther rating means no-EQ on the left, and with EQ on the right.
Panasonic RP-TCM-125 Measurements
Good bit of work was involved in creating the target for IEMs which is different than over or on ear headphones I have tested before. So do note this as you look at the frequency response graph:
Synchronization point of the measurement and preferred reference is around 425 Hz as usual. I was puzzled by this response thinking I was doing something wrong seeing how the bass response is well above reference and the rest well below. Fortunately as mentioned, the non-A revision of this headphone was part of the research from Harman. They don't associate the graphs with the headphones in the paper but man, did I get close to the IEM indicated as "HP4:"
The top graph shows the deviation. Compare that to mine:
Darn close to about 10 kHz, yes?
Distortion is very low at 94 and 104 dBSPL:
The only point to note is something around 2 to 3 kHz:
The fact that we already have plenty of bass and indeed, will be turn down some of that in EQ, we should be in excellent shape with respect to distortion, outperforming many headphones and just about any speaker!
Group delay is almost perfect:
There is a kink between 200 and 300 Hz which also shows up in frequency response measurements. I found the same in another IEM I measured. This may be a measurement artifact so ignore that for now.
Impedance is very low by headphone standards at 16 ohm:
Fortunately most phones and portable headphone dongles are deficient in voltage and not as much current so they should be able to drive this IEM easily. Here is its sensitivity:
As I get more IEMs tested, I will create a bar graph dedicated to them.
Panasonic RP-TCM-125 Listening Tests
For measurements I had used the middle sized silicone tip that came preinstalled. They fit perfectly in the measurement fixture. On my ears though, even though they stayed put, there was no bass at all. In that regard, it didn't sound too horrible. Since I usually wear larger tips, I swapped out the larger size. Oh man, I was not prepared for how horrid these sounded now! Bass became overwhelming like I have not heard before. The rest of the spectrum almost got buried. As much as I like bass, this was just wrong on many levels. So out came the EQ tool in Roon player I use:
The errors are large so I eyeballed pretty large corrections. The transformation was incredible! I am listening to them as I type this. The sound is so detailed, clean and with incredible sub-bass capability that puts a smile on my face on every track! On the ones with high dynamics, the result is startling on tracks like Games from Hans Zimmer Wonder Woman 1984 soundtrack:
It is stunning what fidelity you get! More fine tuning is needed to tame a bit of brightness that exists post EQ but man, what is there is so satisfying I can't wipe off the smile from my face!
Yes, there is no spatial qualities like you get with some headphones. And bass is not tactile like it is on speaker. But high fidelity it is. This bodes well for overall correctness of the target response.
Conclusions
So we enter a new chapter in ASR by testing IEMs. I use mine for a few hours in bed to watch youtube videos in bed so they are essential component to test and review. With respect to this Panasonic, clearly this is tuned to go after bass which they think sells. Maybe this is because they know most people wear these loose so need that extra punch. Result is quite bad given the deficiency above 500 Hz. But apply equalization and this thing pretties up like nobody's business. I look forward to testing more IEMs but for now, I can't stop being impressed with the sound I am getting out of this $15 IEM!
Without EQ, you want to avoid this headphone at all cost. With EQ, the Panasonic RP-TCM125 easily lands in my recommended list.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
I have a bunch which have come for review and I constantly get offers to test more. So I finally allocated a bit of time to see how my GRAS 45CA fixture can measure them and to my delight, it was dead easy, far more than any headphone I have measured! Time will tell however as I measure more whether this is typical or not.To that end, this is also an introductory thread on IEM measurements. So go ahead and say your peace now and here instead of polluting future review threads.
One "problem" with IEMs is how to take pictures of them so I apologize for the crappy nature of this one:
The dual panther rating means no-EQ on the left, and with EQ on the right.
Panasonic RP-TCM-125 Measurements
Good bit of work was involved in creating the target for IEMs which is different than over or on ear headphones I have tested before. So do note this as you look at the frequency response graph:
Synchronization point of the measurement and preferred reference is around 425 Hz as usual. I was puzzled by this response thinking I was doing something wrong seeing how the bass response is well above reference and the rest well below. Fortunately as mentioned, the non-A revision of this headphone was part of the research from Harman. They don't associate the graphs with the headphones in the paper but man, did I get close to the IEM indicated as "HP4:"
The top graph shows the deviation. Compare that to mine:
Darn close to about 10 kHz, yes?
Distortion is very low at 94 and 104 dBSPL:
The only point to note is something around 2 to 3 kHz:
The fact that we already have plenty of bass and indeed, will be turn down some of that in EQ, we should be in excellent shape with respect to distortion, outperforming many headphones and just about any speaker!
Group delay is almost perfect:
There is a kink between 200 and 300 Hz which also shows up in frequency response measurements. I found the same in another IEM I measured. This may be a measurement artifact so ignore that for now.
Impedance is very low by headphone standards at 16 ohm:
Fortunately most phones and portable headphone dongles are deficient in voltage and not as much current so they should be able to drive this IEM easily. Here is its sensitivity:
As I get more IEMs tested, I will create a bar graph dedicated to them.
Panasonic RP-TCM-125 Listening Tests
For measurements I had used the middle sized silicone tip that came preinstalled. They fit perfectly in the measurement fixture. On my ears though, even though they stayed put, there was no bass at all. In that regard, it didn't sound too horrible. Since I usually wear larger tips, I swapped out the larger size. Oh man, I was not prepared for how horrid these sounded now! Bass became overwhelming like I have not heard before. The rest of the spectrum almost got buried. As much as I like bass, this was just wrong on many levels. So out came the EQ tool in Roon player I use:
The errors are large so I eyeballed pretty large corrections. The transformation was incredible! I am listening to them as I type this. The sound is so detailed, clean and with incredible sub-bass capability that puts a smile on my face on every track! On the ones with high dynamics, the result is startling on tracks like Games from Hans Zimmer Wonder Woman 1984 soundtrack:
It is stunning what fidelity you get! More fine tuning is needed to tame a bit of brightness that exists post EQ but man, what is there is so satisfying I can't wipe off the smile from my face!
Yes, there is no spatial qualities like you get with some headphones. And bass is not tactile like it is on speaker. But high fidelity it is. This bodes well for overall correctness of the target response.
Conclusions
So we enter a new chapter in ASR by testing IEMs. I use mine for a few hours in bed to watch youtube videos in bed so they are essential component to test and review. With respect to this Panasonic, clearly this is tuned to go after bass which they think sells. Maybe this is because they know most people wear these loose so need that extra punch. Result is quite bad given the deficiency above 500 Hz. But apply equalization and this thing pretties up like nobody's business. I look forward to testing more IEMs but for now, I can't stop being impressed with the sound I am getting out of this $15 IEM!
Without EQ, you want to avoid this headphone at all cost. With EQ, the Panasonic RP-TCM125 easily lands in my recommended list.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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