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[Samuel Rees]

Does anyone have the frequency response graphs for some Ultimate Ears IEMs? Looking for some info for an upcoming job using a variety of UE products. Specifically interested in the UE7 (what I have), the UE11, and the UE Reference monitors. To my disappointment, UE said it won't give out this information. This is disappointing to me as a customer. In the past I've found their service to be above and beyond great. Feel free to message me privately, or Samuel DOT rees AT gmail DOT com.

[Chris Johnson [UK]]

I'm actually working on a jig to take measurements of such things at the moment, If I get a bunch, I'll let you know.

The real answer is that its quite hard to tell, even if you got the response graphs of the armature drivers themselves. This is because the shell moulding, bore to the driver, and position within your ear canal all affect the response.

But needless to say, I'm also interested in the results.

[Samuel Rees]

I'm actually working on a jig to take measurements of such things at the moment, If I get a bunch, I'll let you know.

The real answer is that its quite hard to tell, even if you got the response graphs of the armature drivers themselves. This is because the shell moulding, bore to the driver, and position within your ear canal all affect the response.

But needless to say, I'm also interested in the results.

Sounds like a tough measurement Chris! Thanks for the offer, please do let me know. I've read that other manufactures like JH offer frequency response graphs. What's up with this? My rep seemed to indicates that they don't send them out "anymore" - that's why I was hoping someone around hear had them from some time back.

[Chris Johnson [UK]]

Sounds like a tough measurement Chris...

Right: So here it is. Round 1 of my IEM measuring.

Let me explain the setup:

So, I'm running Smaart v7.5 on my Macbook Air.
Audio interface is a MOTU Microbook II.
Mic is a Beyer MM1 (calibrated)

Ive basically got a small piece of 8mm I.D (9mm O.D) silicone tube that seals over the end of the mic. The Left IEM earpiece is then sealed onto the end of the tube. This setup leaves the tip of the IEM canal 15mm from the tip of the mic.

I'm using the headphone output of the Microbook II to drive the IEMs, and a loopback cable between line in and out to provide the reference input.

In order to make it a fair fight, I have adjusted the gain of the headphone amp each time to match the level reaching the mic. This is done very roughly by matching the levels on the Smaart meters.

It goes without saying that this is hardly a proper audiological setup. I post this merely as a comparison and also as a learning exercise for how we might look at comparing IEM products

The IEMs on test (actual product names redacted for the time being...):

• Purple Trace: A Dual Driver (2 way x-over) solid acrylic product
• Green Trace: A Dual Driver (2 way x-over) silicone product
• Brown Trace: A Triple Driver (3 way x-over) solid acrylic product

As far as I know, all 3 products use different armature drivers.

The data is attached below.

Issues & Observations:

• I'm sure that more needs to be done in the measurement setup to mimic the conditions of an occluded ear canal. I've read a few articles about the change in 'response' of your hearing when you have an IEM in the canal (as of course you're bypassing the normal effects of the outer part of the canal and earlobe). So on an absolute scale, I take these readings with a pinch of salt. If you look at the absolute magnitude response, they appear to sound not 'flat' at all. However, compared to the sound of a flat speaker (Genelec 8030), they sound more similar than the smaart trace would indicate. So there is clearly something more going on
• As above, I'd suggest that the low frequency rolloff below 125 Hz is not as pronounced as the trace suggests. Certainly all these IEMs look quite similar in that region, but to my ear sound very different in terms of both tonality and extension in the low frequencies
• Whats more interesting is the HF response. I'd say that the Smaart measurement here is accurate, in terms of the relative peaks and troughs of the mag response.
• the Impulse responses are interesting, as is the phase response. The shift at 400-500Hz in the UERM and ACS T2 is interesting. Is that the crossover point, (I would have thought the x-over is much higher, having seen response graphs of the armature drivers) or a filter?

I'll do some more tests when I get a chance. My next step is to improve the LF measurement, since this is pretty far from what I've seen in terms of response curves of the armature drivers in question.

Thoughts and comments appreciated!

[Samuel Rees]

Really great Chris, thanks for digging into this! The graphs look similar to a few graphs floating around the internet, so I think you are getting there. Perhaps the low freq issue has to do with the "seal" phenomenon where we experience a strong LF roll off when we loose the seal of the ear. Perhaps something about this experiment doesn't replicate this.

[Chris Johnson [UK]]

Perhaps the low freq issue has to do with the "seal" phenomenon where we experience a strong LF roll off when we loose the seal of the ear. Perhaps something about this experiment doesn't replicate this.

Yeah, its interesting.

Here is the same Brown set of IEMs but this time with 30mm between IEM and Mic.

On this trace their is a 6.4k spike, whereas on the previous trace there was a dip. This suggests that this is a function of the distance from the mic, or the effects of the tube, or both.

So as you can see, if you take that HF spikyness with a pinch of salt, this product is indeed very flat from 100Hz to ~13k, at which point it drops off quite steeply. I'd say this correlates with my impression of them better than the previous trace

[drew gandy]

Right: So here it is. Round 1 of my IEM measuring.

Interesting project Chris.  Do you have any pictures of the setup? 

The phase response 'flip' around 500hz is simply the phase wrapping around the 180 degree point.  It actually looks quite smooth overall.  I'm not a SMAART guy so I don't know if you can set phase to 'unwrap' or not.  If you can then it might be easier to understand what is happening. 

Here's the Etymotic graph I think I referenced earlier.  It's actually on the front page for the ER-4 earphones.  It shows us the target that they shoot for in order to arrive at a flat end response in your brain. 

[Chris Johnson [UK]]

Hi Drew,

The phase flip is not a wrap. The phase trace is unwrapped there. However, I noticed that the difference between the first screen grab and the second (where the phase is smooth) is exactly 360 degrees, so I suspect Smaart is getting confused as to whether the measured signal is a cycle out or not.

That sort of correlates with what I have read. I know that in the ear, very high frequencies (say ~8k and up) are accentuated. This is presumably because under normal circumstances, these frequencies are attenuated as they bounce down our ear canals from the outside world.

The hump between ~3k and 6k is interesting though. I would have expected the opposite, what with fletcher-munson curves etc...

The thing thats throwing me a bit is the LF response. Either my measurement techniques lack something, or the graphs published by manufacturers are all lies :-)

[drew gandy]

Hi Drew,

The phase flip is not a wrap. The phase trace is unwrapped there. However, I noticed that the difference between the first screen grab and the second (where the phase is smooth) is exactly 360 degrees, so I suspect Smaart is getting confused as to whether the measured signal is a cycle out or not.

This is what I think of when I use the term "unwrapped phase". (see below)
Smaart is showing a maximum of 720 degrees of phase.  But it seems to me that there is some kind of limit within that 720 which is exceeded when showing all 4 of your measurements (the top graph), and it is wrapping.  But, when you show only the one trace it fits within the limit so, no wrap. 

That sort of correlates with what I have read. I know that in the ear, very high frequencies (say ~8k and up) are accentuated. This is presumably because under normal circumstances, these frequencies are attenuated as they bounce down our ear canals from the outside world.

The hump between ~3k and 6k is interesting though. I would have expected the opposite, what with fletcher-munson curves etc...

If you think about the ear canal as a booster of sorts for the upper midrange... When you put the speaker into the signal chain after the ear canal, it will come up short in the upper mids.  Therefore the boost is necessary.  The fletcher-munson curves kind of make sense too when you think about the ear canal boosting those frequencies critical to human communication (and especially baby sounds). 

The thing thats throwing me a bit is the LF response. Either my measurement techniques lack something, or the graphs published by manufacturers are all lies :-)

 
I too wonder about the seal you're getting on your test jig. That seems like the easiest culprit.  But there may be something else going on as well. 

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