A Surprisingly Successful Dual Driver Headphone: The Enigmacoustics Dharma D1000 Measurements

Measurements
Click on graphs image to download .pdf for closer inspection.

Raw frequency response plots show the Dharma does fairly well matching the Harman response curve. It does fall short in not having a straight-line bass response below 100Hz, but this is quite common for an open dynamic driver headphone. The wide dip in the mid-range centered at 400Hz would be better if centered at 200Hz.

The climb from 400Hz to 3kHz has a fairly good profile, but should begin to fall off afterward rather than rising to a peak at 5-6kHz. It does seem to me that this peak may shift around depending on the size/shape/position of the ears in the cup. It does appear at 5.5 and 6kHz in a couple different measurements I made, but when I tuned it by ear it seemed centered more at 5kHz.

The response above 6kHz does fall off a bit, but remains at about the same level subsequently 10dB down from the peak. This area should see a downward and slowly increasing slope. The Dharma's frequency response seems to fluctuate more than normal above 6kHz; I suspect we might be seeing constructive and destructive interference from the acoustic signal emitted from the dual drivers.

30Hz response is good for a dynamic headphone. The top of the waveform is somewhat swayback, and echoes the falling response below the primary driver resonance at 700Hz (seen as the leftmost upward hump in the impedance curve). On the other hand, the bass distortion seen in the THD+noise plot below 400Hz on the 90dBspl plot is severe...though oddly doesn't sound nearly as bad as measurements might indicate.

The 300Hz square wave shows fast, but somewhat higher than desired leading edge spike, followed by a significant amount of noise. Noise like this is often seen with electrostatic headphones, but to my eye the magnitude is excessive. It probably results in some of the "tingy-zingy" sound I heard in listening. This noise and excessive ringing is also seen in the impulse response plots. Yet again, the sound I heard seemed somewhat better than the measurements would indicate.

As I mentioned, the bass distortion is quite high in the THD+noise plots, but above around 600Hz it's quite low.

Impedance and electrical phase plot shows a primary driver resonance at about 650Hz, and then a significant feature between 1kHz and 5kHz. I can only interpret this result as the reactance of the various components of the filter network and the electret driver itself. Enigmacoustics claims the electret turns on around 10kHz, but I have a very hard time believing that given this measurement.

This is an open headphone, so it does not provide much, but isolations measurements show it does attenuate outside noise more than most open headphones at roughly 6dB broadband attenuation.

At 91mVrms to achieve 90dBspl at the ear, the Dharma is slightly more efficient than most headphones of this type.

These measurements seem to me much worse than the sound I heard. Another example of measurements not telling the whole story.

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ARTICLE CONTENTS

COMMENTS
lukeap69's picture

I wonder why you have recommended HEX but not the HEK. Is it because of price?

Tyll Hertsens's picture
Yes.
lukeap69's picture

That makes sense Tyll. I will be waiting for your HEX review. I will be skipping the Dharma...

Rillion's picture

Concerning the THD+noise, this might be a case where looking at the spectrum generated by just a ~100 Hz input tone could provide more insight. It may be that the type of noise and distortion generated is just not very audible in music.

Cheepnis's picture

Could you clarify if this is the Darma from Big Sound 2015 or a final version? I heard there were some changes made.

Tyll Hertsens's picture
This is a production version I received right at the end of Big Sound.
Seth195208's picture

Placing an open back electrostatic driver closely in front of another driver will cause a lot of bizarre interference between the two. The rear of the electrostatic will fire into the rear driver, and the rear driver(including low frequencies)will fire into the back of the electrostatic. The could be the reason the impulse response has such a hard time settling down. On the other hand, if the electrostatic is sealed in the back, it would cause it's own problems.

Josuah's picture

The bass, though not particularly well extended, is nicely balanced in the mix with a slight emphasis centering around 90-100Hz. The weird thing is that measurements show that the bass has huge distortion, which starts to rise below 400Hz to reach nearly 10% at 100Hz. Looking at the distortion measurements would have me thinking the bass would be a wooly, murky mess, but it just ain't so to my ears—nor the ears of most folks who listened at Big Sound 2015.

I'm afraid this comment makes me think you need to get a better understanding of harmonic distortion and different types of distortion. THD is not necessarily going to come with a loss of separation between notes or inability to clearly hear what you are expecting to hear—there can still be a very distinct start and stop to sounds and overall focus on the primary tone. Harmonics can instead add pleasing or unpleasant "richness" to the sound, and in low frequencies often makes listeners happy because it adds weight and pressure to bass.

To use an analogy you might not like being used in reference to your listening tests, this is the difference between a car enthusiast's subwoofer and an audiophile's subwoofer.

This may in fact be why you felt the bass was more extended and the headphone tonally flat. Not because it was actually providing clean bass at the correct SPL, but because the increased distortion as the frequency dropped provided additional acoustic energy to boost the SPL while the pure tone that should have been present was lower in amplitude. Or it is the cause of the frequency response rise in lower frequencies. This is precisely what Rillion is alluding to when he suggests running an FFT frequency analysis for a pure tone.

A "wooly, murky mess" of bass is more likely to be a result of high group delay coupled with high reverb / decay.

(Also, after hitting preview I don't see any way to submit the post. I have to hit back.)

zobel's picture

You are spot on in these thoughts.

Tyll Hertsens's picture
....but when I see distortion this high on headphones, it usually is a murky mess.
Josuah's picture

Harmonic distortion and a smeared, incoherent sound could be two symptoms with the same root cause. Such as poor control of the driver. However harmonic distortion should be not be considered the cause of smeared, incoherent sound or a measurement of smeared, incoherent sound.

But that association seems to be what you were stating with:

Looking at the distortion measurements would have me thinking the bass would be a wooly, murky mess....

followed by:

Many times after eliciting opinions of the bass performance and getting word back that it seemed okay, I would show the listener the distortion curves.

After reading that, someone is likely to come away with an incorrect understanding of THD+N measurements and how to interpret them. I don't think that's good.

Valhallatier's picture

After all this time, i knew there's something wrong with many of tyll's review, and i'm right. He doesn't know that much about how sound travels, though he know the electronics.

GNagus's picture

I'm not expecting to find a teeny tiny crossover with inductors and capacitors in the headphones, but with no filters present wouldn't there be some cancellation with the drivers overlapping frequencies? Also, bass and treble extension aren't as good as I would expect, assuming that is a key benefit of multiple drivers

zobel's picture

It seems that if the drivers summed in phase at the eardrum the overlapping frequencies would be strengthened, and not cancelling. Who knows in these cans of worms though? Your point that this design, employing two drivers for the frequency extremes, should at least have a decent bass response is well taken.

Seth195208's picture
zobel's picture

What do you think is significant and of interest to us from these white papers, Seth? What light has been shed here concerning Tyll's distortion measurements ?
I have the same questions that you raised above about driver placement. Could that arrangement have something to do with the distortion measurements? (Yes it could, he said.) Thanks for your thoughts!

Seth195208's picture

...explaining his findings on the audibility of non linear distortions..
https://community.klipsch.com/forums/storage/3/1326617/earlgeddesintervi...

zobel's picture

I have Dickason's books, and every copy of speaker builder magazine they printed, but never followed Vance Dickason and crew when they started doing voice coil mag. I have been reading others though, and I'm still building systems, so the wave guide stuff is something I've been following. It was interesting to see his findings on the subjective audibility of non linear distortion being directly related to SPL. Is it true then that equal amounts of measured THD (as a percentage of SPL) are perceived to increase with volume? Does it matter where these distortions are in frequency, and in bandwidth (Q)?

About the THD subject; as Einstein said, "We can't measure everything that counts, and not everything we can measure counts." I think, as Geddes states, THD and IMD are too broad and ill-defined to be factors useful in determining subjective quality in transducer response. That is not news. We already have known that the spectrum and Qs of the peaks are the determining factors in the audibility of these distortions. Plots of IMD showing the location of the non linear distortion in relation to frequency are a good tool to show audible spectral distortion. Waterfall plots, and though somewhat less readable, step response and square waves, effectively show frequency response in the time domain. Good tools, those.

And of course the all important SPL/frequency graph! Some day we will be able to present that data as a flat line for flat headphone response. Now there are too many factors that we haven't been able to include in the measurement process. Among these are the individual's ears acoustic interaction with the cans, and that alone is huge. Then there is the realm of the individual's ear/brain interpretation of the same SPLs, which includes hearing acuity and sensitivity, and other factors we don't know about yet, so we can't measure. Hearing, as with all the senses, actually occurs in the brain ultimately. We are just learning about the brain, which is, by far, the most complex thing we are aware of in the entire known universe. Will it be possible in the foreseeable future to connect directly with the brain electrically, via the auditory nerve, replicating and bypassing the ears organs? A wireless implant, not bluetooth ;-) that can be switched into your auditory system (post ear), and switched out for biological hearing would be pretty nifty. That would be the ultimate "headphone" don't you think? Just don't lose your remote.

barun432's picture

Nice Review, Tyll. Please try to review one of the Final Headphones, a company from Japan. They make this awesome headphone called Pandora Hope VI, which incorporates Dynamic driver and balanced armature driver technology. They go for around $600 nowadays and will knock a lot of headphones from your Wall of Fame (All Closed backs in fact) if you listen to it. Hope you review one of their headphones if not the one mentioned above, cause they all have this hybrid driver technology.

Seth195208's picture
barun432's picture

Am talking about a full fledged review of the PH6 and 4 is not a hi-fi audiophile grade headphone like the PH6. He did a measurement earlier this year but not a review. PH6 from a mobile phone scales as good as an un-modded Sony MDR CD-3000 from a high-end desktop rig and in todays headphone market that is unheard of. Hope Tyl will review it so that more people get to know about it.

http://www.head-fi.org/t/696821/reviews-impressions-thread-final-audio-d...

zobel's picture

Some people will not have comfort problems with these; those with mid to small ears that don't stick out from the head much. Leaves me out.

Shalow's picture

Tyll, I tried to correlate distorsion measurements and what I hear for sometime. I hadn't figured it out completly, but I found a very interesting paper here :
http://www.gedlee.com/downloads/AES06Gedlee_ll.pdf
The paper is pretty old, but what they found is pretty interesting. Did you ever had a look ?

Beagle's picture

...is that it never seems to integrate with the rest. It stands on it's own, away from the proceedings, like a kid at recess who's too shy to play with the others.

Mr.TAD91's picture

Cool headphone. It's nice to see how the two driver technologies can work together. Hey Tyll, have you got any impressions on the Pioneer Master 1 headphone? I am really looking forward to your review of them.

I am worried however, about the "fine tuning" the AIR studios technical director did, as I have read some reviews on previous Pioneer + AIR studios products (amplifiers and speakers) that were less than satisfactory in my eyes. As I see it, the engineers and designers should get most of the play time when bringing a new product to the market. This should especially be the case for the Master 1, as they are very costly for a headphone.

Thanks,

Mr.TAD91

zobel's picture

Health and happiness to you, and thanks for hosting this forum! Looking forward to another fine year of music and the gear to enjoy it on at home. You are appreciated, and would be greatly missed if you weren't doing what you do.

Mr.TAD91's picture

I'll ditto what zobel said. And happy holidays/Merry Christmas to all. This time of year I've been rewarding myself for hard work with long listening sessions. We're all very fortunate to have innerfidelity as a solid resource and Tyll as a reviewer. I am anticipating what the future holds for headphione and speaker technology in the new year!

m8o's picture

Yes, I'm very happy I bought them on a Massdrop drop.

Still waiting for Tyll to get his hands on a McIntosh MHA-100, especially to couple with the HE-1000; as almost every person to a rule who has heard the combination says it's the best they ever heard the HE-1000. Now I have to wait for a Sonorous VI review too? -lol

m8o's picture

p.s. this is in response to barun432 above.

lunaswav3's picture

Hi Tyll, happy almost new years! lol. Your reviews are truly in-depth & awesome! I had a small question regarding 2 particular headphones I was interested in acquiring. Have you done a review on the AKG K 142 HD yet? For the price and it's label as Studio headphones, I was interested in your opinion regarding them. Also, I wanted to get the cult-classic SONY MDR-CD900ST, and was just wondering what you'd think of them? Keep up the amazing work you do for us techie audio geeks, lol. Thanks! ♪

Also, I found IF through YT, lol. Cheers!

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