Audeze iSine 20 Planar Magnetic In-Ear Earphone Page 2

The Fazor within the eartube is crucial to the extreme linearity and low distortion performance of the iSine 20.

The trick, for any IEM, is to be a good acoustic impedance matching coupler. An IEM is a completely enclosed system with no normally propagated sound. An IEM is bascally a sonic waveguide from driver to eardrum. As sound moves from the driver through the various spaces to the ear drum, the acoustic impedance in each area can stimulate reflections and resonances if not carefully designed.

Two major competing goals in the IEM design process are linearity and frequency response. Linearity, in this case, means lack of distortion; the reduction of harmonic byproducts and resonances; and good time alignment. Good frequency response is producing something like the Harman response curve at the ear drum. The problem is if you optimize for lowest distortion, you don't necessarily, or even usually, get a good frequency response. If you tweak things to get a good frequency response, you usually do so at the expense of added distortion and phase error.


It appears to me that Audeze chose to optimize strongly for high linearity and low distortion. The above THD+noise measurement is one of, if not the lowest distortion measurements I've taken. It's absolutely superb. Much of this is due the the acoustic impedance matching of the Fazor plug in the eartube of the iSine.


Exploded view of the iSine with parts labeled: A) The base of the Fazor plug; B) Openeing of the ear tube; C) Fluxor magnets; D) diaphragm.

In front of the iSine diaphragm is a circular opening for sound to enter the eartube (labeled B above). This opening is blocked in the center by the Fazor plug (A). This creates a ring shaped passage for sound that decreases in radius until it reaches the tip of the Fazor plug where the sound combines to exit the port into your ear canal.

I did get to talk with Sankar and Doc. C, their chief designer, during a factory visit about a year ago where we discussed the nature of this acoustic design. Suffice it to say it's an extremely complex gadget. In revisiting the Fazor plug this week I had a look at phase plugs and compression drivers as they appear similar in some ways. I asked Doc C. to explain the differences for me:

Let me start with compression drivers. Function is somewhat similar - transferring sound waves from large diaphragm to smaller area with minimum sound degradation. In compression drivers there is very small volume chamber where rigid diaphragm is installed. When diaphragm moves it creates high air pressure. Front side of the chamber (Phase Plug) has small openings or slots where air exits into a mouth of the horn. Openings are optimized to minimize phase anomalies and provide relatively smooth frequency response. Here we are dealing with high air pressure, very high air flow velocities and turbulent air flow behavior. Major benefits are very good acoustical impedance matching and very high efficiency. Downside - typically higher distortion and not very flat response. Compression drivers are limited bandwidth devices, mostly for high frequencies and sometimes for midrange. Near field listening is quite fatiguing with harsh sound.

Fazor - It is an acoustical structure placed within the sound port to properly manage sound waves propagation from large flexible diaphragm into small sound port exit. It works in conjunction with diaphragm, damping cloth (to manage the resonance of the diaphragm), ear canal and ear drum. Fazor has profound influence on the final frequency and phase response in the midrange and high frequencies creating spacious sound stage and great imaging. It is also responsible for acoustical impedance matching between diaphragm and air within sound port and ear canal resulting a very high efficiency (about 110dB/1mW).

After seeing the measurements and noting the very low distortion but significant (in my view) deviation from an ideal target response, I asked if the direction of optimization was towards high linearity and then use of DSP to tweak the target response.

iSine design was very complex. It took many months of acoustical simulations, prototyping and tweaking to get the best possible performance. This was ground breaking research of something that was not done previously. The main design goal was to make reliable, good sounding earphones with high power handling, very low distortion, great imaging, high sensitivity, and excellent sound quality. Due to the nature of the internal acoustics, like forcing large diaphragm to send sound through very small diameter hole we have ended up with not "perfect" response (still better than in most IEMs), but excellent behaving earphones. Along with our super-thin Uniforce Diaphragm, extremely strong magnetic induction created by our Fluxor magnets and open back design we have a unique product which is hard to beat.

Isine is primarily designed as a high-end portable solution for listening to the music. Since we have already developed Ligtning cable it was a natural solution for us to use its very powerful DSP to create even better sound signature. I am all along with your research on ideal target curve, as many others like Harman, ... Ligtning cable has given us a nice hardware solution to correct the earphones to sound as best as possible.

Here's the frequency response using the passive cable.


And here we see the corrected raw response with the Lightning cable.


In passive mode you can see in the raw response plots (gray) that the major peak is at about 1.7kHz and does not resemble a good target response. In the Lightning cable measurement you can see that the response is quite close to the Harman target with a modest bass boost below 100Hz, a gentle and ever increasing run-up to the peak at 3kHz, and subsequent roll-off in the treble. This is a very nice response profile; the Cipher Cable DSP does a very good job of correcting the natural response of the iSine 20.

The down side, in my view, is that the iSine really needs to be driven through the Cipher cable from an Apple product. There are currently no easy tuning/EQ solutions for PC and Android users, but progress is being made, and some plug-ins are soon to be available. Audeze has shared their compensation curve as a set of parametric-EQ values, you can learn about it starting with this Head-Fi post by Karthick Manivannan, Audeze Research Director - Signal Processing. Until all that gets sorted, I consider the iSine 20 a product best viewed as Apple centric, and in that roll it excels.

Lets talk about how it sounds...

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Cheepnis's picture

I'd like to know if the iSine 20 sounds better using the Std cable when running from and iphone to a DAC/Amp like the Mojo. I rarely use the iphone alone with iems, and prefer to use a lightning cable and adapter directly into the Mojo. This would mean I'd lose the advantage of the DSP in the iSine cable, but have a better quality sound using the Mojo's DAC and Amp.

It would be interesting to me if a comparison of iphone using the iSine Cipher Lightning cable vs. using a std lightning cable into a DAC/Amp. Thoughts?

dustdevil's picture

You find the answer to your question if you read the last 2 pages ;)

barun432's picture

Comparison of the cipher cable via an iOS device with a DAP or a DAC/AMP would've been helpful in order to understand the sonic capabilities of iSine20

Also in this open in ear category one of the best contenders is Ocharaku line of premium in ears (E.G. Flat 4 Line, Kaede, Nami, Kuro, Sakura, Akazakura). It would be very interesting to see them (Ocharaku) go head to head with the iSine line, as they are also good for home/office use.

jaredjcrandall84's picture

I have the mojo and decided to buy an ipod and lightning cable, i'll let you know how the two sounds against each other.

jaredjcrandall84's picture

At first I didn't like the sound from the cipher but after a bit I am loving it. The mojo has more resolution but I do realize after some time that the cipher is more EQ balanced resulting in the sound being more what I have heard from my expensive IEMs e.g. Layla, and a12.

GMP100's picture

I always wanted to look like a Tie Figther when listening to music ;)

steaxauce's picture

Hey Tyll, in your view, how do these fit into the heierarchy of other headphones and in-ear monitors? These are pretty unique, so I realize it's a bit apples-to-oranges, but it could still be useful to hear how you'd rank them against other gear. Are they the best in-ear monitors you've ever heard? What price point full-sized headphones would you take them over?

potterpastor's picture

Did you get a chance to compare the sound of these with the isine 10?

stalepie's picture

Why can't the DSP effects be applied in other software outside of the Cipher Lightning cable, such as on PC or Android? Is it just a trick to make it sound best with iPhones since it's sold in Apple stores?

brause's picture

Well, why not forking out more money for the earphones than for the fitting iPhone? Wonder how much the dac/amp combination in the iPhone costs? And if you elect to change to an Android device or any other device, you still get mediocre sound with the conventional cable.

Lots of money for a huge lack of flexibility.

Am I glad to have gotten the Focal Sphear on sale.

jaredjcrandall84's picture

A good argument, but I find that the isine 20, cipher cable, and a Dap (iphone) is more enjoyable than when I had a phone connected to a chord mojo, or other dac, plus 1300-2000 IEMs. I find that I use the iphone for a media device that isn't exclusive to the isine. Ultimately, an iphone se 128 gig (dap) for $380, plus isine 20 & cipher ~$60 - total less than $1000, is more enjoyable than my 2k Iems plus a dac. Trade-offs exist of course but overall I enjoy my current work setup than I did in the past.

potterpastor's picture

Don't know about the isine 20, but I have the 10 and even with the cipher cable, I don't like it because it lacks that bass impact I like with my M2 over ear and even the SE 215

crenca's picture

I am a bit conflicted over this review. On the one hand, Tyll made it more or less clear that this is an Apple ecosystem specific product. On the other hand, he reviewed it like any other product. This was intentional of course, but it does seem to give the impression that this product is useful outside of an Apple ecosystem. Sure, you can tweak it with DSP (something I do with all my HP & 2 channel gear) but this product is different in that it is clearly designed for the Apple universe...

jaredjcrandall84's picture

I have Isine 20 and mojo and do enjoy it greatly even though Tyll has claimed that the cipher cable really enhances the sound. I have only been into audio for about three years but get persuaded that I am missing out when I read these types of reviews. I'd save some money if I picked up what sounded best and then put on blinders, but that is only part of the experience albeit probably the best part? My ignorance is probably a little bit of bliss, but knowledge takes me on a bit of an experience journey.

hapnermw's picture

I enjoy InnerFidelity and appreciate all the work that Tyll puts into it. I’m presenting what I’ve personally experienced as another datapoint in the iSine20 discussion.
I’ve been listening to an iSine20+Mojo with a Mac Laptop and iPhone for the last year and have been very satisfied with the inner fidelity of this combo.
Recently, curiosity got the better of me and I decided to buy a Cipher Cable to see if its improved EQ was the critical element in sound quality this review has stated.
In my evaluation of the Mojo vs the Cipher Cable, I hear a significant difference between them.
I use the term ‘emotion’ a bit in what follows. I expect this translates to the ability of an earphone/headphone to fully reproduce the quality of the signal its fed which includes its ability to reproduce its detail/dynamics/microsonics/etc.
To make this difference as specific as I can I’ll focus on one cut of an album that illustrates it.
This is St. James Infirmary on Allen Toussaint’s CD, The Bright Mississippi. I selected this CD because it is an example the current state-of-the-redbook-art. I selected this cut because it has emotional weight and power and expert musicianship. I’ve imported this CD as an Apple lossless file to iTunes and loaded it on my iPhone.
I’ve listened to this file’s bits served by my iPhone to two DAC/Amps - my Audeze Cipher Cable and my Mojo (via USB/USB camera adapter/Audeze regular cable) - connected to my iSine20s.
I’ve also listened to this file on my Focal Utopias through a Mac iTunes/BitPerfect/USB/Yggy/Rag/Balanced Q Cable (i.e. I’ve heard the full emotional impact its bits can deliver).
If you listen to this cut via the Cipher Cable it sounds pretty good. Likely better than what most people expect an iPhone to sound. When you listen to this cut via the Mojo the emotional content of this music opens up in a way that is missing through the Cipher Cable.
Clearly there is something beyond the simple ‘EQ’ dimension that produces this - the quality of DACs and Amps do make a difference. It’s clear that this difference transcends whatever impact the difference in headphone EQ is between these two cases.
I don’t dispute that there is some difference in EQ; however, to my ear it pales in comparison with the quality of inner fidelity produced by the Mojo/iSine20.
The iSine/Mojo captures something quite comparable to my home Utopia system. They are not equal but they both present the music with the detail/dynamics/microsonics that are capable of delivering the music’s emotional experience.
The Cipher Cable simply does not meet this bar. This is not that surprising given its level of DAC/Amp sophistication/cost vs the Mojo.
The fact the quality of the signal produced by the Mojo overrides (IMHO) the iSine EQ issues Tyll documented implies that InnerFidelity is a bit over-rotated on head EQ curves as the arbiter of headphone listenability/quality. It has damned the iSine 20 to Cipher Cable ‘hell’ without a proper understanding of the impact on music quality a high quality DAC/Amp can make.

Augustus's picture

The HifiMan RE400 have about the same THD (90db) and other characteristics like the iSine, but offers better sealing and frequency response (vs the iSine without the cipher cable) and cost about 1/8 of the iSine 20...

If Audeze will release (or you, Tyll, wink wink) EQ plots to get the iSine to the Harman target without the cipher cable, that would be great.
(tried in the past to tweak the headphones based on 2 FR measurements on the site, but it didn't work)

Audeze_R's picture

We have published Cipher EQ and many use it with android or PC/Mac platforms. Tyll also links to it in his review:

Augustus's picture

It was nice of you to post it

Augustus's picture

I think now that Audeze has released 'Reveal' (DSP plugin), it has changed the picture dramatically. Now I can apply the DSP pluging when I convert the music for my portable player\smartphone so I don't need the cipher cable. It was a very good decision by Audeze.

frankmccullar's picture

I own and use Aeons from MrSpeaker and love them. Recently I bought some Airpods from
Apple and they sound pretty good; good enough that I think they deserve a formal review, in spite of their lowly origins. They are certainly pleasant and easy to use and they sound much better than I expected. Give us you expertise on this consumer product please.

Max_Minimum's picture

Do the first and second versions of the Cipher cable use identical equalization curves? I have just bought and received the iSine 20 and it appears I have the v2 cable while Tyll had the v1. I'm wondering if his take on tonality and eq settings apply to the v2 cable. Usually, my preference in tonality very closely matches his. But this time I find I scale back the top end a little while Tyll attenuates the high mids/low treble.

Matt Rowen's picture

The looks of them are weird, but I must say they sound amazing. Most of the I use them in my office. Initially, I thought they will attract many eyes because of their weird looks but they seem pretty much fine as of now. One thing that I don't like about them is their bulkiness and I really have to think twice before putting them on my apple earpods. I will add them to my good gaming earbuds guide very soon.