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Phase Alignment in Multi-Driver IEM’s

What about phase/time alignment and in-ears?

Allmost all serious in-ears contain more than 1 driver.

If you have a 3 way earpiece (for example with three drivers), the frequency spectrum is divided into three parts and you get two crossover points (the frequency where one driver takes over from the other): one speaker will do all the low frequencies, one the mid range and one the high range.

But if the sound of the different drivers does not reach your ears at the same time (because the driver responsible for the highs can be faster than the driver for the mid for example), you can get serious cancellations around the crossover points.

it seems that most manufacturers do not take this into account, often all drivers are in a row and time differences are not corrected.

In this image you can see this:

Jerry Harvey has fixed this and use their patented Freq Phase technology. With this he slows down/delays the fastest driver by putting longer tubes in between, so the sound from all speakers reaches your ears at the same time.

Read / see more about this here:

https://jhaudio.com//freqphase

https://www.youtube.com/watch?v=L3tyY1nRq5E

Now on to the measurements to prove that this works…

Here the measurement of the phase of three in-ears:

Pink: Jerry Harvey

Yellow and (dark)green: two other major worldwide in-ear manufacturers

As you can see, Jerry Harvey has nowhere a 360 degree phase flip or something like that. And the phase of the entire frequency spectrum stays nicely between the 360 degrees.

But what does this do with the sound?

Pink: Jerry Harvey

Yellow: competitor (the earpiece of the photo)

The phase change below 100hz is due to the low-cut in the headphone amp.

As you can see, the Jerry Harvey has much more highs above 8khz. In addition, you can see that the ear of the competitor has a serious dip around 8kHz.

According to Jerry Harvey (what he says in the video about FreqPhase), this is because the phase is not in order. That sounds logical to me.

I think this is why people say that Jerry Harvey in-ears sounds more enjoyable and serene. Because there are no time/phase problems!

I tried to capture the inside of a Jerry Harvey earpiece to see all the tubes, you can clearly see the drivers are offset from each other.

Chiel Streutjes – CS-Audio – www.cs-audio.nlwww.facebook.com/CSAudioNL

Chiel Streutjes used a 7mm MiEMi™ with an Isemcon EMX7150 mic to make these measurements.

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How Much Difference Do Headphone Amps Make?

During touring I discovered that my in-ears do not always have the same sound (which would be very nice, so I have always the same reference). Sometimes the in-ears sounded very muddy and far away.

Because of this I started to do a number of measurements and tests.

My in-ears sound good and give the same frequency response on a Schiit audio hi-fi phone amp, AudioQuest DragonFly Black/Red and FisherAmp in-ear amp2. Because of this I used the FisherAmp as a reference for all measurements.

First I measured a FisherAmp in-ear Amp 2, PSM300, PSM900 and PSM1000 as a line-out (without the load of an earpiece):

Belts.png

Green: FisherAmp

Yellow: PSM300

Red: PSM900

Blue: PSM1000

As you can see, all four are almost flat. However, the PSM900 and PSM1000 have a serious low-cut and high-cut and around these areas there is also a bump (probably because of the used crossover filter)

The next measurement is with the load of the in-ear:

2.png

As you can see, the high response is different. The PSM300 and PSM900 give less highs, around 10 kHz a db or 3-4 less (a quarter of the volume!)

The following measurement is the same earpiece on two mixing desks:

3.png

Green: reference (previous measurement on the FisherAmp)

Pink: Midas Pro serie

Yellow: Midas M32

As you can see there is a serious difference in the highs. This is exactly the problem I experienced live. This makes the earpiece sound muddy and far away.

Because of this shocking discovery, I have decided to test all-in-ear type’s on a good and bad phone-amp at the dealer of a large worldwide in-ear brand, here the results:

3-way – 4 driver 18 ohms:

4.png

Orange: FisherAmp (reference)

3 way – 8 driver 16 ohms:

Lola.png

Orange: FisherAmp (reference)

3 way – 12 driver 15ohms:

Roxanne.png

Orange: FisherAmp (reference)

3 way – 8 driver 28ohms:

13.png

Orange: FisherAmp (reference)

As you can see, the earphones at the two phone-amp’s give a completely different frequency response.

The conclusion: a good earpiece does not always sound good, it is the combination of earpiece and phone-amp. Even the phone-amps in beltpacks give different results, but especially the phone-amps in mixing desks are shocking!

The surprising thing is that the 8 driver 28 ohm earpiece is not bothered by anything. Probably because of the higher impedance, It looks like some phone-amps are not made for a mega low impedance, this is probably the cause of the problems.

Another thing is, the impedance in the specification of an earpiece is the impedance at 1khz, but what happens at other frequencies?!?

Many good/widely used in-ears have a low impedance:

UltimateEars UE6Pro: 12,5 Ohms

UltimateEars UE Live: 10 Ohms

Westone ES50: 20 Ohms

Jerry Harvey JH10x3Pro: 18 Ohms

Jerry Harvey JH16v2Pro: 18 Ohms

So be aware of the phone-amp you use in combination with your in-ears!

Chiel Streutjes – CS-Audio – www.facebook.com/CSAudioNLwww.cs-audio.nl