Headphone measurment rig - recommendations
Sep 30, 2019 at 6:00 PM Thread Starter Post #1 of 11

Samk15

New Head-Fier
Joined
Sep 29, 2019
Posts
24
Likes
1
Location
Australia
Hi audiophiles,
I'm new to this forum and have many questions in mind but will start from fundamental questions first to have a better understanding of the audio engineering.
About myself and gears:
1- knowledge of audio engineering 1/10
2- speakers: M-Audio Av40
3- headphone: KRK 6400

You can see that I'm a beginner in audio field so please bear with me and my somewhat noob questions.

I was watching some videos on youtube about audio measurment and the gears being used by some individuals as well as the professionals.
I was wondering how sensible is the difference between lets say a GRAS 45CC gear vs minidsp EARS setup?

Besides mathematics, everything else in this world is relative. So if a headphone is measured by a more expensive GRAS gear, would the output results show more accurate results and how you tell if it has a more accurate result than a EARS setup.
From my understanding, everyone has a different interpretation of the sound quality as many factors such as ear canal, eardrum, bones, skull, etc create some sort of resonance in the audio.

So if I measure few headphones using EARS, the result is "relatively" true as all headphones are measured by the same gear and if I use GRAS then the same cqn be concluded.

So back to the questions:

1- how can you tell the difference between accuracy of the gear A vs B?

2- If I have to build a custom measuring gears, do I need a dedicted mic, amp, dsp, etc or I can just buy the mic and use my computer to do the measurment?
 
Last edited:
Oct 1, 2019 at 5:05 AM Post #3 of 11

GREQ

Headphoneus Supremus
Joined
Oct 11, 2009
Posts
5,714
Likes
3,237
Location
Frankfurt am Main
Hmm, looks like nobody is interested in this thread! Maybe I've posted it in the wrong forum!
Give people a chance to respond. Not everyone in the world lives in the same timezone as you.


1- how can you tell the difference between accuracy of the gear A vs B?

2- If I have to build a custom measuring gears, do I need a dedicted mic, amp, dsp, etc or I can just buy the mic and use my computer to do the measurment?
1 - Only sure way is to own and use both, measuring exactly the same headphones under the same conditions.
Then take the results from both and work out the differences.

2 - The absolute minimum needed to make measurements is a microphone and REW (room EQ wizard) (= free software).
But this will create problems because no microphone records sound with a perfectly 'flat' response curve, this is why each measuring 'rig' will come with it's own unique software calibration files to compensate for hardware differences.

I was watching some videos on youtube about audio measurment and the gears being used by some individuals as well as the professionals.
I was wondering how sensible is the difference between lets say a GRAS 45CC gear vs minidsp EARS setup?
The fundamental main differences are that a GRAS rig uses higher quality microphones and the rig itself has more axes the microphones/mounting plates can be angled/positioned.
This means that it's theoretically easier to mount more headphones properly on a GRAS rig, as the miniDSP rig's silicone 'ears' are mounted perfectly horizontally and cannot be angled to mimic the human head.
The difference in mounting and pressure between the 'incorrectly' flat mounting on a miniDSP and the 'correct' mounting on the GRAS should already make some difference to the measurements simply because the ear pads will be depressed differently.
This kind of problem can be overcome on the miniDSP ears by simply mounting the headphone one ear at a time in a sort of 'lop-sided' fashion, especially with some headphones that cannot be mounted anywhere close to 'correctly' on both ears at the same time.
This however will introduce inconsistencies between L and R channels, as it's very difficult to maintain consistent results with mounting positions and pressure changing with each new 'mount'.
The GRAS overcomes this problem by mounting both sides more closely to the 'correct' position with one mount by changing the plate angle.

So from a practical point of view, the GRAS is designed for professionals, and the miniDSP is designed for hobbyists looking to just have a bit of fun, who are content with reasonably decent graphs that at least are comparable to other measurements on the same rig.

As an owner of the miniDSP E.A.R.S. I'm pretty sure it's almost useless for waterfall graphs, and not great at distortion graphs either, but frequency response graphs are where it shines.
It does have a pretty steep learning curve to overcome the design problems and get more consistent graphs, but it's become an important and useful tool for my headphone modding projects.
 
Oct 1, 2019 at 6:59 AM Post #4 of 11

Samk15

New Head-Fier
Joined
Sep 29, 2019
Posts
24
Likes
1
Location
Australia
As an owner of the miniDSP E.A.R.S. I'm pretty sure it's almost useless for waterfall graphs, and not great at distortion graphs either, but frequency response graphs are where it shines.
Nice to hear from someone who actually owns the gear.
To compensate for the flat ear design of the minidsp E.A.R.S and gain more accurate reaults, can a rubber band help to add some pressure on the headphone?
 
Oct 1, 2019 at 8:06 AM Post #5 of 11

castleofargh

Sound Science Forum Moderator
Joined
Jul 2, 2011
Posts
9,512
Likes
4,907
mostly what he said. if the concern is FR, then almost anything will work fine and some choices will simply be more convenient or offer closer repeatability. a FR is about measuring a fairly loud signal, that you can rapidly learn to set according to your mic and room noise. and once that is done, you compare 2 of your headphones by measuring their relative FR on your rig. that will almost always work fine and give you a pretty accurate data on the relative variation between the 2 headphones at a given frequency. a 5$ mic and a cardboard box can give you similar and valuable informations. @GREQ mentioning modding is a very good example of something you can really benefit with pretty much any measurement rig.

now, if you expect any given rig to tell you what is neutral, forget it, that won't happen. the first hurdle being that there is no neutral for a headphone. on your head, you're getting something different from the same headphone on my head. and in the event that our eardrums get the same FR, chances are that we will still interpret them differently based on our own HRTF. even the guys making the most expensive dummy heads understand that, so at best what they can aim for is a curve that's close to an average of many humans. and some such dummy heads are so famous and massively used in the industry and in research that their calibration has kind of become the de facto idea of neutral. so others(like me sometimes), try to copy that and their various compensation curves, but objectively speaking, it's both bad and fine. bad because those references usually mean nothing to our rig acoustically speaking. and fine because measurements are arbitrary stuff by nature, even the choice of a unit was an arbitrary decision made for convenience or whatever. my point isn't to judge, only to point out the reality of the situation so that you are conscious that just because we end up with a graph and apply some compensation to it, we do not suddenly become the holders of the truth about neutral.

if you aim for other measurements, THD for example is going to manifest some 40dB or lower(hopefully lower), below the test signal on most headphones. so already we need something to accurately capture air pressures that much smaller compared to the initial signal that would be captured for a FR graph. obviously some expensive stuff might be more sensitive, have lower self noise, etc. really cheap stuff won't give very significant graphs unless the distos are really loud. we also have to deal with ambient noises, which is a real issue for me but has nothing to do with money(well in a way it does, I could do with a little isolation box like they have at Head-fi's headquarters ^_^).
I mostly fool around with IEMs and the E.A.R.S turned out to be a pile of crap for that purpose(half my IEMs simply won't fit on that BS pinna, the IEMs like etymotic used with deep insertion can't be measured in situation because there isn't enough "ear canal", etc). so I haven't used the E.A.R.S a lot beyond enjoying a new toy when I got it and testing stuff out of pure curiosity with my headphone. for most stuff, I get better results with a sub 100$ mic. but certainly the E.A.R.S are very convenient compared to trying to use books, cardboard, sponges, and really anything I can put my hands on to try and have a mic hold in place in front of a headphone in a stable and repeatable way:sweat:. different uses will bring up the qualities and flaws of each solutions IMO. and to get back to "neutral", out of 4 cheapo makeshift rigs(one being the E.A.R.S), I get 4 different FR graphs. once I apply a compensation to make them all show the same one for a given headphone, I do get more consistency with other headphones, but they still had a tendency to show inherent differences(caused I guess by placement, pressure on the pads, difference in the fake ear canal length, etc). and with IEMs it's much much worst and I can't get any pretend consistency between my crap rigs for more than maybe one out of 3 IEM at best. the variations in the coupler changing how much resonance and at which frequency it will occur, cause obvious and hard to avoid variations.
but as I said at the beginning, if we put aside that fantasy of having a copy of some professional rig for a hundred bucks, FR graphs work fine for me even on the crappiest and cheapest stuff. I don't mod much but I EQ a lot, and I can clearly know how much the FR really changed when applying some EQ to the test signals. the amplitude variations are accurate from one measurement to the next, it is objectively good. just not good for everything.

for headphones on the E.A.R.S, I tried to add a layer of stuff between the ear blocks and the metal, to increase the ear canal length, but also to get a bigger "head" as I find the original spacing a little small compared to how a headphone holds on my own head. but I couldn't achieve a good enough seal between the surfaces in a way that was reversible, so I gave that up. then I thought that maybe I could at least move the mic capsules back inside and use some plastic tube or whatever, that's when I pulled out a contact on one of the capsules(the soldering job is almost as bad as what I can do, and I'm crap at it). so after those 2 failures, I lost my motivation to turn that device into something more practical for myself. maybe I'll get back to it someday.

2- If I have to build a custom measuring gears, do I need a dedicted mic, amp, dsp, etc or I can just buy the mic and use my computer to do the measurment?
again, for FR graphs, DAC and AMP choices are pretty much irrelevant. for other stuff, usually it still doesn't matter, but if you start using a 4%THD tube amp to measure headphone distortions, that might not go great ^_^. so I'd say it usually isn't important. again if you fall into IEM measurements at some points, then the amp becomes a little more important as its output impedance or maybe some protective caps could significantly affect the FR of some IEMs. with headphones, they tend to have more even impedance response and higher impedance values, so any potential impact is minimized.
 
Oct 1, 2019 at 9:12 AM Post #6 of 11

GREQ

Headphoneus Supremus
Joined
Oct 11, 2009
Posts
5,714
Likes
3,237
Location
Frankfurt am Main
Nice to hear from someone who actually owns the gear.
To compensate for the flat ear design of the minidsp E.A.R.S and gain more accurate reaults, can a rubber band help to add some pressure on the headphone?
Absolutely.
This is pretty much exactly what I do to get consistent results.
There will be the occasional odd-ball headphone that can't sit on both ears at the same time, so rubber bands and measuring one side at a time is the only option.

Also, I forgot to mention - the GRAS doesn't have a silicone dummy ear, so it should be theoretically easier to get a consistent seal with on-ear headphones.
The miniDSP EARS is extremely difficult to get consistent seal with on-ears because the silicone is much stiffer than human skin + cartilage and hardly moves about at all.
Over ears and IEMs are pretty easy to measure.

Ear buds are the most difficult, and it doesn't even come with suitable compensation graphs for ear buds because it seems to be quite a niche.
You can measure the same bud in incrementally different positions and the bass can change by about 20 decibels.... it's almost maddening.
Even between ear bud users, there are already wildly contrasting opinions on tonality of the same bud because they don't fit all ears, and some people use foams, some don't, etc... so... that actually kinda matches my experience trying to measure buds.
 
Oct 1, 2019 at 10:08 PM Post #7 of 11

Samk15

New Head-Fier
Joined
Sep 29, 2019
Posts
24
Likes
1
Location
Australia
Over ears and IEMs are pretty easy to measure.

@castleofargh found it difficult to measure IEMs due to badly designed ear canal. So it seems that the user experience is inconsistent with the EARS gear. I believe it's better to omit the EARS altogether and go with a custom-made gear instead.
I was looking into both, Behringer ECM8000 and Dayton Audio UMM-6. Not sure which one produces better output. UMM-6 comes with calibration file and can be measured/powered up via USB port connected to a computer. (Easier to measure I guess!).
ECM8000 on the other hand requires a dedicated hardware to operate it (difficult to operate and calibrate!).
I can buy a dummy head and use two mics for L & R measurement and resigned the ear canal.
What are your thoughts on that?
 
Oct 1, 2019 at 10:30 PM Post #8 of 11

buke9

Headphoneus Supremus
Help and Recommendation Contributor
Joined
Feb 21, 2015
Posts
9,143
Likes
1,825
Location
Kentucky
@castleofargh found it difficult to measure IEMs due to badly designed ear canal. So it seems that the user experience is inconsistent with the EARS gear. I believe it's better to omit the EARS altogether and go with a custom-made gear instead.
I was looking into both, Behringer ECM8000 and Dayton Audio UMM-6. Not sure which one produces better output. UMM-6 comes with calibration file and can be measured/powered up via USB port connected to a computer. (Easier to measure I guess!).
ECM8000 on the other hand requires a dedicated hardware to operate it (difficult to operate and calibrate!).
I can buy a dummy head and use two mics for L & R measurement and resigned the ear canal.
What are your thoughts on that?
My first question is why. There are several people that give measurements so I guess you don’t trust them. The other is again why? I mean I really don’t care but do you think what you are going to measure is going to be better than the others ? Just asking.
 
Oct 1, 2019 at 10:49 PM Post #9 of 11

Samk15

New Head-Fier
Joined
Sep 29, 2019
Posts
24
Likes
1
Location
Australia
The other is again why? I mean I really don’t care but do you think what you are going to measure is going to be better than the others ?
Well, you answered your own question. You don't care!
I don't remember I said what other people measuring is incorrect or my results would be better or i don't trust them!
 
Oct 2, 2019 at 1:01 AM Post #10 of 11

castleofargh

Sound Science Forum Moderator
Joined
Jul 2, 2011
Posts
9,512
Likes
4,907
@castleofargh found it difficult to measure IEMs due to badly designed ear canal. So it seems that the user experience is inconsistent with the EARS gear. I believe it's better to omit the EARS altogether and go with a custom-made gear instead.
I was looking into both, Behringer ECM8000 and Dayton Audio UMM-6. Not sure which one produces better output. UMM-6 comes with calibration file and can be measured/powered up via USB port connected to a computer. (Easier to measure I guess!).
ECM8000 on the other hand requires a dedicated hardware to operate it (difficult to operate and calibrate!).
I can buy a dummy head and use two mics for L & R measurement and resigned the ear canal.
What are your thoughts on that?
it really really depends on what you're aiming for and what you're going to do the most. as a ready and overall practical solution, it's really hard to beat the E.A.R.S because it's the only cheap solution that was made for the purpose of measuring headphone and why not IEMs. and as I said for simple FR graph where you check variations between the stuff you measure yourself, pretty much any solution is fine, including the E.A.R.S.
now if you plan to try and align or directly compare your measurements to somebody else online(pro or not), well it's not a very good idea in general, but if that's what you want, the best solution is to go for the same gear that person is using. many people have an ECM8000(I always want to write EMC for some reason^_^) or a Dayton(the USB or the XLR version), because they're famously pretty flat and cheap. so of the few amateur headphone rigs out there, this isn't a bad idea to get that and ask the person you want to mimic, how he made his box and what trick he uses for the part that the headphone pads are facing(material for a given amount of seal, or attenuating some reflections at high freqs or whatever). but getting close to pro gear that way is... let's say, unlikely. so you have to be pretty clear on what you're aspiring for from the start as it might be too late later on once you have settle on some gear. for example, if you plan to do IEM measurements, the main standards for amateur stuff are the Dayton IMM6(the tiny stuff you typically plug on a cellphone or a tablet) and a plastic tube as "coupler", and using an actual coupler, although usually some fake Chinese copies for pricing reasons. if you get yourself an UMM-6 for example, it going to be complicated to adapt it to those 2 options and still get similar results. strangely enough I haven't seen many people taking coupler for IEMs and doing headphone measurements with them, but I guess that's yet another of many many options available. the limit isn't what you can try, but what you're trying to achieve. that's really what will force you toward a given type of setup IMO.

about the ear canal of the E.A.R.S, it's just a short tube, so it doesn't behave like an IEC711 coupler would. which is still to this day a famous reference for measurements and liked by many guys doing amateur IEM measurements(I have a super cheap one that I mounted on an ECM8000 with some destructive DIY, so I wouldn't really advise that road(also I'm pretty much the only guy using that consistently, and I know of 2 others who tried something similar but still added their own salsa or moved on to more typical rigs. so not the popular reference of anything).
what annoys me most about the E.A.R.S is how the ... not sure how it's called... concha area? is too small for me to even stick a small shure SE215 in/on it. and it's usually the same problem with IEM that have that slightly ergonomic shell for the outer part instead of being mostly just a long tube. I read somewhere when they started selling it that they were going to offer different ear models and maybe they have one that's cool? IDK. but the default stuff that shipped with mine isn't a typical ear, even my mother with especially small ear, can fit the SE215 inside her concha area(whatever the correct name is, sorry if I'm wrong about that).

a warning about the calibration for the UMM-6 or similar products, that calibration is for for stuff in free air. the moment you get a more or less effective seal with a headphone or some IEMs and whatever material around that headphone, the compensation curve stops having meaning as the rig and headphone are creating their own reflections and resonances. again, if you're going to try and copy someone else with specific setup, then that calibration might offer a reference for the headphone itself and let you then tweak the rest to try and match the results from that person. but otherwise it's not that helpful(sadly).




some stuff you might be interested in reading:
https://www.head-fi.org/threads/headphone-measurements-different-setups-different-results.751100/
this is more IEM focused. https://www.head-fi.org/threads/audio-measurements-on-a-headfi-budget.893084/
maybe this one, where the plan is to have a tour with some IEMs so we can all see and use our own measurements to compare to what other people got on the very same pairs. https://www.head-fi.org/threads/ety...phone-for-your-ears-and-your-couplers.908512/ it's still going on right now and will probably start the mini European part, then loop back to the US again unless you or someone else ask for a detour. so depending on when you plan to get something and if you care about IEMs, you might be interested in joining our merry band of curious amateurs. we're more like noobs sharing our problems and thoughts as we go along, than really knowledgeable dudes. but as a starting point that might be exactly the type of stuff one might want. I certainly wish I had more people to talk to when I started measuring stuff and having to discover all the issues by myself.
for headphone and amateur DIY stuff, I feel that Purrin and his long time buddies, are the reference that everybody has been trying to imitate on the web, so while I mustn't give links toward big bad wolves, I feel that they are the ones to talk to or at least read about if you plan to do a good deal of headphone measurements. again, not because they're doing it "right", but because his various iterations of a rig have been providing a fair amount of graph and many audiophiles will consciously or not, compare your graphs to that. so again in the spirit of finding the most practical reference for whatever you care about most, for cheap amateur rigs, @purrin is it IMO. just like for IEMs, @crinacle is probably the most famous reference. before he was using an IMM6 out of a phone and a silicone tube, now I believe he has one of the fake IEC couplers I mentioned before. I have critics about both, but because of the sheer number or graphs he provides and his fame, he's made a well deserved reference of himself. you take one of his graphs and can compare it to a multitude of other IEMs he measured with the same rig. the value of that clearly overcomes any play pretend idea of objectively more accurate measurement if we're not going to also have a huge library of measured IEMs done on that "better" rig.

alright, I wrote too much unnecessary stuff and will stop now that I notice it.^_^ hopefully some of it can help a little.
 
Last edited:

Users who are viewing this thread

Top