Making measurements with external headphone amplifier on diy artificial pinna testrig.

jesperlykke

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Hi all...

I'm prototyping my diy artificial pinna headphone/IEM testrig.
So far it's just a prototype, a rig with 2 silicone ears munted on rund plates as can be seen on pictures.
The mic. is an IEC711 clone (Phantom powered)
I'm waiting for some coupler attachment to glue into the measurement mic. holes on the inner side of the ears; making it possible to screw the mic. into them instead of just putting it in.
(this will also completely make it airtight)
But I'm trying to have as good as possible measurement's before I will finish the proto ofcause. -More to come.

My measurement setup is as this.

FiiO headphone amplifier for driving the headphones, IEM etc... (Both SE and balanced)
IEC711 mic. ---> phantompower adaptor (Røde VXLR+) ---> Cosmos APU (+34dB) ---> Cosmos ADC (The soundcard)

I'm saving the sweeps (L. and R. seperate) from REW@ -25dB and play them through the FiiO amp. @ full volume.
The sweeps are saved with acoustic ref. for the correct channel (L. or R.)
I'm also setting a copy of the sweep into REW as stated in the documentation.
A Measurement Sweep file must be generated and saved from the REW signal generator. The sweep file must include the acoustic timing reference signal, REW uses that to synchronise input capture to playback on the system being measured. A copy of the file is placed on the system being measured and the file is also loaded into REW so that it can configure the correct measurement frequency range, sweep settings and sample rate, which are retrieved from the file.

The "calibration" for the measurement is as this.
It's not possible to make a soundcard (Cosmos ADC) calibration, as it's an ADC only. But the freq. responce is flat. - So no soundcard calibration.
I calibrate the mic. with an external 94/104/114dB tester as described in the documentation also.

I will try to post some measurements here, but I would like to have some input's.
Maybee I should do something else, or maybe on another way. Please comment :)
What do you think?

Jesper.

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The mic. is an IEC711 clone
It looks like you"re doing everything right. I have my doubts that the self characteristic of this microphone is flat. Did you calibrate it in the sound lab? Or did you compare the measurements with it and the calibrated microphone?
 
Hey @sm52

I did not do any calibration of the mic. (not yet anyway)
There is a calibration file in a .zip file I recieved from the seller, but I did not try this yet.
I read over at ASR that those cal. files was nogo, but sure I will try it out anyway.
 
So I did some measurements.

I tried to create a calibrationfile for the IEC711 Clone, with an UMIK-1 as ref.
Also I tried the calibrationfile provided by the seller.

But I think the results are more accurate without any calibration at all. -Compared to FR on them Hifiman on different web site's.

I tried both with and without AutoEQ FIR's for this headphone.

The reason for the small difference between right & left, is the microphone insert, which are not finished yet.

Jesper.


HIFIMAN HE400SE 1. test.jpg



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