we've already made some big investments into our testing lab a new building new
talent and some crazy new equipment and we are finally ready to start talking
about it see these two heads they're called hats or head and torso simulators
they're for testing personal audio products and the ones in front of me
cost a combined 80 000 us dollars which is why we
definitely cannot afford to keep both of them what lies no please i'll do
anything anything uh
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link down in the description below the keynote among you might notice that our
hats happen to be missing the uh torso part but that's okay because that
only really matters for speaker testing and we're gonna be focused on headphones
and microphones for the time being also the torso is a plastic tub that adds
twenty thousand dollars to the cost so
i'll pass now understandably you might actually feel the same way about the has
part couldn't we just use any plastic head the answer is
no there is a method to the madness here this form of hearing simulator was first
created in the 1980s to accommodate the testing of phones and hearing aids you
see the thing about hearing devices is that depending on the conditions they
can perform dramatically differently you can try this for yourself lift your
headphones off your ear like this
sounds pretty different right so these state-of-the-art hats models from
just a couple of years ago both claim to better represent a headphones real world
performance by simulating not just the shape of a human head so you get a good
seal but also even the ear canal both of
them are also equipped with high performance microphones allowing us to
test the full range of human hearing with both of them costing about as much
as an actual human head don't ask me how i know so why not just hire trusted
listeners to evaluate headphones for us it's because listening is a subjective
experience that can be influenced by your mood your biases and even your um
state of mind man that means that any product review that relies solely on a
human evaluator will be inherently unreliable now we could look at the spec
sheet but a shocking number of audio manufacturers seem to be pretty much
copy pasting the same performance numbers alongside vague posting nonsense
like next level listening or we retain the emotion of the sound
so i guess we can't trust them either what do if you've ever read or watched
headphone reviews you might have seen something like this before it's called a
frequency response graph and it's meant to help us visualize the sound signature
of an audio device the left end of the x-axis represents the lowest bass sounds
that humans can hear about 20 hertz and the right end represents the highest
treble frequencies that humans can hear around 20 000 hertz with these we can
chew through manufacturer claims like a hot head chews through butter some might
claim to have a neutral sound for example but actually they have the base
cranked up so high it would wake up your neighbors to measure these numbers
though we need to start with the right gear let's get acquainted with our potential
suitors here then bachelor number one is the b k 5128 type b and aside from
having obviously better microphones it improves upon its 1981 predecessor in a
few ways for the ear canal bnk averaged
mri scans of 40 test subjects to give it
a longer more human-like shape and
instead of using purely soft rubber they added plastic components to the inner
parts to represent the acoustic effect of the bonier inner ear
now for bachelor number two sort of the hms 2.3 ln hec aka the super
hms comes from head acoustics and by their own admission it is
actually based on the b k 5128
but simplified it has a shorter ear canal and is made of just rubber
resulting in slightly looser tolerances for acoustic impedance both below 80
hertz and above 12 kilohertz not ideal but the larger diaphragm of
the super hms's microphone results in a lower noise floor which means slightly
improved performance in certain other tests like distortion now there was a
bachelor number three right here but our headphone test engineer has actually
worked with that model before and thinks that it is crap so we didn't even bother
renting one now at this point at least on paper it seems like the 5128 is the
obvious choice but a lot of that is based on manufacturer claims which
is not how our lab is supposed to work so we spent the last few weeks which
cost us thousands of dollars in rentals by the way validating those claims and
searching for potential flaws while looking fabulous of course wan
hoodies now in stock lttstore.com as for why it took so long
to test i'm really glad you asked we needed to run two sets of tests one
comparing the heads to each other head to head you might say and the other
comparing the heads to 25 of our own fleshy guinea pigs i mean excuse me
employees that's for a human to machine comparison now the demographics of our
company are not representative of the general public got a lot of default
character creation screen dudes here but after some adjustments to our
calculations to compensate we were ready to measure the base of eight different
headphones on each of our human subjects
why only bass okay we wanted to measure treble as well but
because treble sound waves are very short a 15 kilohertz wave is actually
less than an inch the microphone position needs to be very precise across
all of the test subjects which we didn't have time to deal with during our
short-term headlones bass waves on the other hand are very long a 20 hertz
sound wave is 55 feet in length so microphone placement doesn't require the
same level of precision across our human subjects to acquire comparable results
and besides in our head-to-head testing data we found only small differences in
the treble range between the two heads so we proceeded with our human testing
which oh apparently i'm next let's go
step one is our subject gets to place microphones into their ears like
how i don't know how so the first step would
be to sanitize your hands and also sanitize your ears that makes sense even
in not covered times when you're talking like ear goop
look at it go this is for the inside of your ears
now we have to place the microphones this is the left ear okay here you do
the left one then i'll do the right one okay it goes inside your ears like this
it does not necessarily fit everyone for some it's a bit too small and it just
keeps coming out something you might be familiar with this is cool there's a
microphone right here they look right and then this little guy sits in your
ear a little something like i guess it goes kind of like that
okay and then this goes here okay so then put the headphones on the
way you normally would okay then i'm going to play a noise
our headphone test engineer just played pink noise through the headphones for me
which you could think of kind of like pink noise is tuned more for human
hearing so it doesn't sound so harsh to us now i take them off i put them back
on yeah every time we put on our headphones we do it a little differently
maybe the band is here or maybe it's more like here or maybe our kids are
playing around with all the adjustments
and that's the second pass okay and we do that five times with every subject
yeah now these are open-backed headphones is it a problem that people are clicking their mouses and stuff
again we're not in a controlled lab environment so that's expected they will
not miss an opportunity to remind me that the current conditions are not
perfect i know over 1 000 measurements later the resulting average looked like
this so how does that match up to our heads
the quick and dirty version is that with open back headphones we found a
measurable but minor variance between the two units and between our human test
subjects but both of these are within what we'd consider to be an acceptable range
our engineer isn't ready for video appearances yet but he will be
publishing a more detailed write-up on flow plane for those of you who want to
dig a little bit deeper into why we consider that okay shifting gears to a
popular closed back headphone we see a much different story look at this
variance in humans at 40 hertz 14 decibels
that means that some people would be perceiving more than twice as much bass
compared to others completely changing the listening experience this is because
closed back headphones rely on a proper seal to create their base comparing our
heads however again they're pretty close
but the 5128 measured slightly closer to
our humans than the super hms so both heads get a pass here but the 5128 it
gets a gold star we also tested some in-ears that are
known to cause problems for hats in general and found that this issue was
present in both of our models meaning that these had struggled to get a good
seal on some larger iems two more passes
but this time with unhappy stickers because it means no matter which way we
go i'll eventually have to replace this darn thing really
anyhoo i guess it kind of makes sense that our results have been so close
given that both of these models are based on the same design and that both
are considered industry standard testing equipment
we do however have a winner
the bnk 5128 some may disagree with our assessment
some might not think it's worthwhile to get any head and torso simulator because
the greater body of academic headphone research has been done on older
simulators and is therefore less applicable to this new hardware but we
feel that we can take the current knowledge base and adapt it to the newer
models to get the best of both worlds the best research and the best tech to
be clear the super hms is still an excellent product and a major
improvement over its predecessor but the things that pushed us toward the bnk
where it's ease of use improved durability and better reputation i'm
happy with our choices but there's a big but here i want to make it
clear that our results here are not the be-all and end-all of audio testing at
all and the testing that we end up doing in the future with the bnk 5128 it's not
going to be the be all and end all either for one thing this simulator by design
represents the average person and no one
person is average especially not you as an LTT viewer you're decidedly above
average so what that means is that the response curves that we get from this
head will not directly reflect what you hear in your ears
it's just that by adding some objective knowledge to your toolkit you can become
a more informed consumer who can find the best headphones for your needs
faster also at our lab the goal is to never be satisfied with good enough
we're gonna spare no expense i mean really if i'm not putting my money where
my mouth is at this point come on guys but there is always going to be room for
improvement we know that our tests weren't perfect here for many reasons
and no one is more critical about our testing protocols than the very people
that we've hired to create them but our lab is still under construction and achieving our goal of industry-leading
testing is going to take some time there's also just much more that we'd
love to test outside of just the frequency response of headphones like
the microphones noise cancelling distortion testing even trying to find
ways to apply response curve data to the human perceptual system so if there are
tests you guys would like to see let us know in the comments because this
is just the beginning the beginning of this message
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for free today thanks for watching if you're interested in more headphone content check out our
video where we did some subjective testing of 35 knockoff airpods spoiler
um our staff by and large actually preferred them to the real thing