Chapter 5 - Getting It Wrong
Nov 1, 2016 at 9:19 AM Post #31 of 37

CraftyClown

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Thank you so much for these blogs Paul. I am just about to start down the road of headphone reviews and am determined to do it properly. I get frustrated by the amount of airy fairy subjective reviews out there and I'm sure I'm not the only one.
 
I'm going to have a crack at FR measurement and have just purchased all the bits you are currently using. I'm also thinking of using an Etymotic ER4 SR as my benchmark IEM, that I can also use to calibrate my Veritas results with. The reason I'm thinking this is it's famously as neutral as they come, so should be great to compare other IEMs against and it's FR is so well documented that it should make the Veritas calibration relatively straight forward. probably kidding myself there though :D
 
Does that sound at all sensible to you?
 
Nov 1, 2016 at 9:59 AM Post #32 of 37

CraftyClown

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Sorry, whilst I have you, I have another couple of quick questions;
 
I'm based in the UK and matching some of the same bits you are using isn't so simple. I can't find the Shure volume attenuator for example. Can you suggest an alternative?
 
I also can't find the same SPL meter. I'm happy to purchase a different one, but I was wondering how accurate the replacement I get should ideally be. They seem to range in price from about £10 to £300. Are there particular specs I should look out for?
 
Finally regarding the little coupler you were using; it was just a home made improvisation I'm guessing?
 
Apologies for all the questions, but you seem to have a solid and sensible system here that I'd love to use as a benchmark
 
Thanks again
 
Nov 3, 2016 at 4:45 AM Post #33 of 37
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  Thank you so much for these blogs Paul. I am just about to start down the road of headphone reviews and am determined to do it properly. I get frustrated by the amount of airy fairy subjective reviews out there and I'm sure I'm not the only one.
 
I'm going to have a crack at FR measurement and have just purchased all the bits you are currently using. I'm also thinking of using an Etymotic ER4 SR as my benchmark IEM, that I can also use to calibrate my Veritas results with. The reason I'm thinking this is it's famously as neutral as they come, so should be great to compare other IEMs against and it's FR is so well documented that it should make the Veritas calibration relatively straight forward. probably kidding myself there though :D
 
Does that sound at all sensible to you?

 
Hey no problems.  If you're going to use the Veritas system - just be aware that uncalibrated it has a tendency to understate from about 4-5 kHz up.  The only way to get closer to a true reading would be to find someone with a properly calibrated system, get them to measure the ETYs, send you the actual data, and then make a calibration adjustment.  Otherwise - if you are just after comparison data, the graphs will show you the relation between the target IEM and ETY uncalibrated (which is what I basically did up until about 4 months ago)
 
  Sorry, whilst I have you, I have another couple of quick questions;
 
I'm based in the UK and matching some of the same bits you are using isn't so simple. I can't find the Shure volume attenuator for example. Can you suggest an alternative?
 
I also can't find the same SPL meter. I'm happy to purchase a different one, but I was wondering how accurate the replacement I get should ideally be. They seem to range in price from about £10 to £300. Are there particular specs I should look out for?
 
Finally regarding the little coupler you were using; it was just a home made improvisation I'm guessing?
 
Apologies for all the questions, but you seem to have a solid and sensible system here that I'd love to use as a benchmark
 
Thanks again

 
Any attenuator should work - but Shure should have offices globally - try https://www.shure.co.uk/products/accessories/earphone-accessories/eaadpt
 
Here's the SPL meter I use from Amazon UK - https://www.amazon.co.uk/Mercury-Digital-Sound-Level-Meter/dp/B000LNJ0IO/ref=sr_1_7?ie=UTF8&qid=1478162602&sr=8-7&keywords=spl+meter
 
The coupler I use is home-made.  Best is to get some transparent semi-rigid tubing which will snuggly fit over the stem of the SPL meter.
 
Nov 3, 2016 at 6:06 AM Post #34 of 37

CraftyClown

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Hey no problems.  If you're going to use the Veritas system - just be aware that uncalibrated it has a tendency to understate from about 4-5 kHz up.  The only way to get closer to a true reading would be to find someone with a properly calibrated system, get them to measure the ETYs, send you the actual data, and then make a calibration adjustment.  Otherwise - if you are just after comparison data, the graphs will show you the relation between the target IEM and ETY uncalibrated (which is what I basically did up until about 4 months ago)


Could I not use the data from the graphs Ety always provide with their ER4s to make my calibration adjustments? Or is it more complicated than that?
 
Nov 3, 2016 at 6:20 AM Post #35 of 37
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Could I not use the data from the graphs Ety always provide with their ER4s to make my calibration adjustments? Or is it more complicated than that?

 
The way I did it was to measure the IEM on my equipment, and then compare same IEMs on another piece of properly calibrated equipment.  Then write a file for the difference.  The measurements show in tables - a freq followed by a vol measurement in dB.  The calibration file I got had about 2-3000 entries.  Yes you could do it manually - but I don't know how accurate you'd get it.
 
Nov 3, 2016 at 6:35 AM Post #36 of 37

CraftyClown

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The way I did it was to measure the IEM on my equipment, and then compare same IEMs on another piece of properly calibrated equipment.  Then write a file for the difference.  The measurements show in tables - a freq followed by a vol measurement in dB.  The calibration file I got had about 2-3000 entries.  Yes you could do it manually - but I don't know how accurate you'd get it.


Ah got you. So I could do it my way but it would be far more accurate to get the exact figures. I suppose I could ask Etymotic if they'd send me their numbers.

Thanks again for your help Paul. I'm just waiting for all my bits to arrive now :)
 
Nov 3, 2016 at 7:03 AM Post #37 of 37

castleofargh

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Hey no problems.  If you're going to use the Veritas system - just be aware that uncalibrated it has a tendency to understate from about 4-5 kHz up.  The only way to get closer to a true reading would be to find someone with a properly calibrated system, get them to measure the ETYs, send you the actual data, and then make a calibration adjustment.  Otherwise - if you are just after comparison data, the graphs will show you the relation between the target IEM and ETY uncalibrated (which is what I basically did up until about 4 months ago)


Could I not use the data from the graphs Ety always provide with their ER4s to make my calibration adjustments? Or is it more complicated than that?


as long as you don't have exaggerated expectations. to be clear, your rig will not behave totally like ety's system, or like your own ears once you have inserted the IEM the way you prefer with the tips you prefer. so you're still making your own reference that happens to look like ety's graph for that IEM.
because the er4sr has the +/-1db accuracy over a good part of the audible range, using it as your reference does add a bonus over any other random choice. other people with this IEM will be able to relate to your reference with that same accuracy in that frequency range.  when using other IEMs you usually can expect bigger variations from pair to pair so if you have to pick one IEM, this is a good choice.
and if you really don't want to bother too much with compensations and calibrations, the shortest road is to simply plug your er4sr in the veritas(or whatever you'll decide to use), consider the insertion depth as well as you can(not that easy for me),  and use autocalibration and use that as you calibration from now on. so when you measure the the ER4sr, you get a flat line, and anything with more bass will simply show more bass. that way the er4 is really your flat reference and you don't need to be an excel spreadsheet master. ^_^
 
or you can decide to imitate the curve seen on the er4 certificate, so that ety's raw is now your base for calibration. here are 3 readings of the same measurement, they all really say the same thing:

what matters is to pick one and stick to it when you later go and make all your measurements. calibration, smoothing, scales. all that needs to stay the same so that people can compare one of your measurement to the next(I still have a hard time doing it but don't tell anybody), which is the only really informative bit we provide in the end. even the super expensive dummy head manufacturers don't claim to have the neutral reference(because it does not exist for more than 1 ear), so it would be silly of us lowfi graph makers to claim that we have such a reference. repeatability is what we can do, the rest is for readability or convenience.
PS: having to boost some parts of the trebles by more than 30db to go from my raw to ety's raw, shows why the veritas doesn't cost 10k$ and why it's healthy not to take results in those areas for granted.
 

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