[Richter Di]

The Meier Audio Corda Soul gets more recognition. As Jan Meier states on his website.

These prototypes have been presented on the last event in Berlin and were received extremely well by all who gave them a listen. By Headfonia the SOUL was elected "best amp of the show".
Later some small modifications helped to improve sound quality even further, as could be heard on the two Audiovista-shows in Krefeld last year. Again, by the public this time, the SOUL was elected "best amplifier of the show"

If you like, I also have written a review about the Soul here: https://www.head-fi.org/showcase/corda-soul.23528/reviews

As some of you might know, the Soul has a 6dB, Q=2 notchfilter to help to get rid of tedious resonance frequencies of our favorite headphones. As Jan describes on his website:

Many (even high-end) headphones do have one or two distinct resonance frequencies in the 6..11 kHz range due to the entrapped air-volume between driver and ear. Proper application of the notch filter will lower the energy at the resonance frequency and our tests (using HD800, HE-500, T1, ...) have shown that this can result in a remarkable improvement of quality of sound.

As I am the lucky owner of one of the prototypes and shipment of the final product is just around the corner, I thought it would be great to have a list where we add over time the best notch filters for our headphones.

So here is the list.

Dial count from left - dial count from right - kHz of notch filter - recommended position for headphone
1 - 11 - 6 kHz -
2 - 10 - 6,4 kHz - Sennheiser HD 800 ( LLF +2, LF +1)
3 - 9 - 6,8 kHz -
4 - 8 - 7,2 kHz - Sennheiser HD58x (Hifi Forum user Codobor otherwise known as robodoc)
5 - 7 - 7,6 kHz -
6 - 6 - 8,1 kHz - Beyerdynamic T1 (2nd generation) (@MarkHe) / Stax LNC (Hifi Forum User Codobor otherwise known as robodoc)
7 - 5 - 8,6 kHz - Hifiman Ananda
8 - 4 - 9,2 kHz - Hifiman HE-500 with angled pads
9 - 3 - 9,7 kHz - Hifiman HE-500
10 - 2 - 10,4 kHz - Fostex Massdrop TH-X00 Ebony with deeper Dekoni pads- plus taming the area below 1 kHz with the tone controls.
11 - 1 - 11 kHz - Standard Fostex TH-X00 / Denon AH-D 5000 (Hifi Forum user712)

The way I came up with the recommendation is by looking the innerfidelity measurements and using information in the manual.

If you have the Corda Soul, please let me know what you are interested in and I will update the table accordingly.

 

[MRC001]

Wow, you got to buy one of the prototypes? Nice! Jan reports the set of 25 pre-ordered amps are complete, now undergoing final quality checks and about to ship. So I'll have mine soon, eagerly awaiting.

In case anyone wants to look up a particular headphone:
https://www.innerfidelity.com/headphone-measurements
Keep in mind, it's common to see different measurements from different sources, since they may be using different HRTF reference curves.

Regarding the headphone notch filter, it's worth pointing out this Soul feature is always a 6 dB cut, not a boost. This makes it cleaner to implement in DSP since it can never cause digital clipping. Yet this not applicable to some headphones (like the Audeze LCD) that don't have a resonance peak, but are mostly flat with a dip rather than a peak. For example to correct the LCD-2 you need a boost not a cut, and something like +3 dB @ 4500 Hz, Q=0.67 works nicely.

 

[Richter Di]

Wow, you got to buy one of the prototypes? Nice! Jan reports the set of 25 pre-ordered amps are complete, now undergoing final quality checks and about to ship. So I'll have mine soon, eagerly awaiting.

In case anyone wants to look up a particular headphone:
https://www.innerfidelity.com/headphone-measurements
Keep in mind, it's common to see different measurements from different sources, since they may be using different HRTF reference curves.

Regarding the headphone notch filter, it's worth pointing out this Soul feature is always a 6 dB cut, not a boost. This makes it cleaner to implement in DSP since it can never cause digital clipping. Yet this not applicable to some headphones (like the Audeze LCD) that don't have a resonance peak, but are mostly flat with a dip rather than a peak. For example to correct the LCD-2 you need a boost not a cut, and something like +3 dB @ 4500 Hz, Q=0.67 works nicely.

Thanks. Makes a lot of sense.

 

[Richter Di]

Fostex Massdrop TH-X00 Ebony with the deeper and angled Dekoni pads - Posiion 10 plus taming the area below 1 kHz with the tone controls.

 

[Richter Di]

Just added the Hifiman Ananda notch filter with 7 counts from the left or 5 counts from the right, taming the 8 to 9 kHz peak with the notch filter beeing set to 8,6 kHz.

 

[MRC001]

While you're at it, just for fun, you could expand this. The Soul's notch filter is designed specifically for acoustic resonances which are typically roughly 6 dB and Q around 2. But headphones may have other kinds of frequency response deviations that can be corrected by combining the Soul's notch filter with its 4 tone controls, which act cumulatively.

Ideally, for these corrections one would would a digital parametric multi-band EQ, which can be done in software on PCs or with products like the Behringer DEQ2496. But the Soul has the flexibility to handle some of them.

 

[Richter Di]

While you're at it, just for fun, you could expand this. The Soul's notch filter is designed specifically for acoustic resonances which are typically roughly 6 dB and Q around 2. But headphones may have other kinds of frequency response deviations that can be corrected by combining the Soul's notch filter with its 4 tone controls, which act cumulatively.

Ideally, for these corrections one would a digital parametric multi-band EQ, which can be done in software on PCs or with products like the Behringer DEQ2496. But the Soul has the flexibility to handle some of them.

Totally agree.

Fostex Massdrop TH-X00 Ebony with the deeper and angled Dekoni pads - Position 10 plus taming the area below 1 kHz with the tone controls.

I do this all the time.

 

[MarkHe]

Richter Di, I appreciate your collection of notch filter settings for different headphones. For my Beyerdynamic T1 (2nd generation) I have set it to 8,130 Hz, but the charts publicly available differ significantly (e.g. reference 1 or 2). The headphone is plugged into the 120-Ohm output. I’d be highly interested to know your adjustments.

I do enjoy the Corda Soul very much. The two devices offer a pleasant listening even at low volumes and for longer sessions. I neither need more bass, treble nor reverb. It feels like having got a very good seat in the concert hall. And thanks to crossfeed I am re-hearing old recordings like Pink Floyd's with growing pleasure.

 

[Richter Di]

Richter Di, I appreciate your collection of notch filter settings for different headphones. For my Beyerdynamic T1 (2nd generation) I have set it to 8,130 Hz, but the charts publicly available differ significantly (e.g. reference 1 or 2). The headphone is plugged into the 120-Ohm output. I’d be highly interested to know your adjustments.

Thank you.
Unfortunately I do not own a T1, so I have no possibility to add my own impressions.

 

[Richter Di]

Richter Di, I appreciate your collection of notch filter settings for different headphones. For my Beyerdynamic T1 (2nd generation) I have set it to 8,130 Hz, but the charts publicly available differ significantly (e.g. reference 1 or 2). The headphone is plugged into the 120-Ohm output. I’d be highly interested to know your adjustments.

PS: 8 is 9,2 kHz in my book. Why did you mean 6 which is 8,1 kHz

Germans use „ , “ instead of points. Maybe this is the confusion. So 1.000 is for me one thousand.

 

[MRC001]

Tyll Herstens measured the T1 resonance peak at 8,000 to 9,000 kHz.
Innerfidelity has a treasure trove of headphone measurements that will be useful for deciding whether to use a notch filter at all, and if so, at what frequency:
https://www.innerfidelity.com/headphone-measurements

The Soul notch filter is -6 dB, Q=2 which is about 1/3 octave on each side of the center frequency, a ratio of about 1.26:1. For example if centered at 8 kHz, the range would be from about 6.3 to 10 kHz.

 

[MarkHe]

Thank you both. At the moment my notch filter setting is 8130 Hz (6 - 6 - 8,1 kHz in the list). Tyll’s two measurements describe the T1 1st. gen, the PDFs date from 2011. I keep on listening, maybe I succeed in an adjustment by ear.

 

[Richter Di]

Thank you both. At the moment my notch filter setting is 8130 Hz (6 - 6 - 8,1 kHz in the list). Tyll’s two measurements describe the T1 1st. gen, the PDFs date from 2011. I keep on listening, maybe I succeed in an adjustment by ear.

Thanks just added to the list.

 

[Richter Di]

Two additions from Hifi Forum User Codobor
Dial count from left - dial count from right - kHz of notch filter - recommended position for headphone
1 - 11 - 6 kHz -
2 - 10 - 6,4 kHz - Sennheiser HD 800 ( LLF +2, LF +1)
3 - 9 - 6,8 kHz -
4 - 8 - 7,2 kHz - Sennheiser HD58x (Hifi Forum User Codobor)
5 - 7 - 7,6 kHz -
6 - 6 - 8,1 kHz - Beyerdynamic T1 (2nd generation) (@MarkHe) / Stax LNC (Hifi Forum User Codobor)
7 - 5 - 8,6 kHz - Hifiman Ananda
8 - 4 - 9,2 kHz - Hifiman HE-500 with angled pads
9 - 3 - 9,7 kHz - Hifiman HE-500
10 - 2 - 10,4 kHz - Fostex Massdrop TH-X00 Ebony with deeper Dekoni pads- plus taming the area below 1 kHz with the tone controls.
11 - 1 - 11 kHz - Standard Fostex TH-X00

 

[Richter Di]

Another update

Dial count from left - dial count from right - kHz of notch filter - recommended position for headphone
1 - 11 - 6 kHz -
2 - 10 - 6,4 kHz - Sennheiser HD 800 ( LLF +2, LF +1)
3 - 9 - 6,8 kHz -
4 - 8 - 7,2 kHz - Sennheiser HD58x (Hifi Forum user Codobor otherwise known as robodoc)
5 - 7 - 7,6 kHz -
6 - 6 - 8,1 kHz - Beyerdynamic T1 (2nd generation) (@MarkHe) / Stax LNC (Hifi Forum User Codobor otherwise known as robodoc)
7 - 5 - 8,6 kHz - Hifiman Ananda
8 - 4 - 9,2 kHz - Hifiman HE-500 with angled pads
9 - 3 - 9,7 kHz - Hifiman HE-500
10 - 2 - 10,4 kHz - Fostex Massdrop TH-X00 Ebony with deeper Dekoni pads- plus taming the area below 1 kHz with the tone controls.
11 - 1 - 11 kHz - Standard Fostex TH-X00 / Denon AH-D 5000 (Hifi Forum user712)