REW FR measurement for IEM, help needed

[ori73]

Hi everyone,

I have read already starter guides about how to measure the FR for IEMs and ordered the equipment for that purpose.
However, many things remain unclear to me.
I succeeded (partially maybe...) with my first FR measurements in REW but somehow the lower end seems to be off when comparing
to other FR graphs from other sources.
The low end does not align with other graphs I have seen, rising from 20 db (and earlier) first up and then declining in this example from 100 db onwards.

I am using an IEC 318-4 coupler 711 clone. The coupler is connected to an external sound card.
Coupler is connected to the sound card's microphone jack and the IEMs to the headphone 3.5mm jack.
I am using the sellers calibration file (and I guess there is the problem...).
I have calibrated the mic to 85db SPL.

And my settings in REW:

How it is "supposed" to look:

I checked the tips I am using (foam tips now), changed to different types and sizes to ensure the seal.
Attaching as well the calibration file from the seller.

What am I missing here?

Any help / comments very welcome.

Many thanks in advance.

 

[Keith_W]

The low end of IEM's is highly dependent on the seal. You will find that different eartips will affect the frequency response. If you are having problems with the low end, try a different sized eartip.

 

[ori73]

The low end of IEM's is highly dependent on the seal. You will find that different eartips will affect the frequency response. If you are having problems with the low end, try a different sized eartip.

Thanks, did that already. Different foam tips and different silicon tips. I will try again with different sizes but I thought that is pretty straight forward imo. Will probably add a photo here how I insert the IEMs into the coupler.

 

[Keith_W]

Well it does look as if the measurement you took is fairly similar to published, with exception of the bass. There are notes from many people that IEM measurements are reliant on the seal. Are you sure that your test fixture was manufactured correctly and the mic is sealed to the canal? Maybe test it with another IEM?

 

[ori73]

Well it does look as if the measurement you took is fairly similar to published, with exception of the bass. There are notes from many people that IEM measurements are reliant on the seal. Are you sure that your test fixture was manufactured correctly and the mic is sealed to the canal? Maybe test it with another IEM?

Thanks for your feedback and things to consider.
I got the rig from a known Taobao seller so I think it is pretty reliable.
As I was searching again for a solution, I came across to connect the Qudelix 5k with the USB c port of my PC and use an audio split cable to connect the measurement rig and the IEMs then to the Qudelix 5k.
Took a while to configure the Qudelix as a pass thru but finally worked so under Windows 11 I was able to set mic and speakers to Qudelix.
Initially that didnt work cause you have to set the right parameters in the Chrome extension for Qudelix.

Now, new measurements look way better, actually fixed the issue.
I have not freakin clue why my PC and with even external USB sound cards connected, had this issue.
But I hope if someone has similar issues will find this thread.

Thanks again for your time.

I just need to work on consistency. Measurements are quite forward with foam tips but with silicon tips it is not that easy, got quite many deviations.