#### RayDunzl

##### Major Contributor
Central Scrutinizer
Depends on the track I'd think. Here's a snippet from one of my future bass songs. Sub-20hz bass hit.

Wow. 60db above the general level.

#### nhatlam96

##### Active Member
Forum Donor
pick an amplifier with output impedance below 1.5 ohm and you are golden. The general rule is that the output impedance of an amplifier should not be more than 10% of the headphone you are going to drive.

Otherwise with a high impedance headphone amp, you have to do some math and figure out how the frequency response gets modified.
How was that 10% rule made? Sorry for being annoying

This and sensitivity are the most abused specs in headphones and speakers.
A good example could be dt880, which has different impedance models, like 250ohm and 600ohm. With a closer look on these headphone models, we can then find out how they determine those headphone ohm values?

With higher output impedance (flat across the frequency assuming) more voltage share will be at the peak frequencies hence the peak frequencies get louder.
Is this related to Voltage = Current * Resistance?

For example: there is high resistance on a specific frequency, which will result in high output voltage for that frequency. Output voltage also determines the output volume level for that frequency.

#### solderdude

##### Major Contributor
how do I know, what headphone is more sensitive to output impedance than others? Focal Clear has 55ohms, which is quite low, does this has any relation to amp output impedance? Solderdude said everything under 10ohm for the Clear is fine, but I do not know the math behind this
This is what happens when the clear is driven by a 120 Ohm source:

With 10 Ohms there will be a very small 'boost' in the lows. With close to 0 Ohm no boost at all.

There is NO impedance matching with any headphone... regardless what people or even manufacturers say.

OP

#### amirm

Staff Member
CFO (Chief Fun Officer)
Hi @amirm

Why the hell are you aggressive ?
I was not responding to you. I was quoting your helpful response to @Artaois. As to being aggressive, I think I got asked 10 times if the headphone was defective or I didn't really hear this problem.

OP

#### amirm

Staff Member
CFO (Chief Fun Officer)
Accoustic Compression is a real think, not just a marketing invention.
I measured it before. Could not get anything useful to report and it stresses the headphones mightily.

OP

#### amirm

Staff Member
CFO (Chief Fun Officer)
How was that 10% rule made? Sorry for being annoying
It is a simplified rule of thumb that says the frequency response error will be less than 1 dB. Research actually indicates as low at 0.5 dB in some cases (broad resonances). So maybe you want 20:1.

#### imagidominc

##### Member
Forum Donor
I don't understand the critics of this review. The truth is the headphone is exceptional sound quality wise but has one major flaw. In Amir's review he said it sounded good before it started clipping on him. I don't think anyone has to take an all or nothing approach on this. There are many people, myself included, that own Focal headphones and enjoy them. However, this is audio SCIENCE review, and I think mechanically this headphone is just not up to snuff with Amir's standard of quality, which includes design, not just sound. In the end Focal headphones are a "buy at your own risk" situation. It is not confirmed by anybody that this is a quality control issue, and in fact we have evidence from the company itself that this is intentional. Whether your specific pair clips or not, is besides the point. I think every customer should have confidence that they are buying a non clipping unit (especially at this price range), instead of leaving it up to a coin toss.

#### nhatlam96

##### Active Member
Forum Donor
This is what happens when the clear is driven by a 120 Ohm source:

With 10 Ohms there will be a very small 'boost' in the lows. With close to 0 Ohm no boost at all.
What amplifier has been used here or did you emulate those 120ohms by software? Can a beginner like myself recreate this graph?

It is a simplified rule of thumb that says the frequency response error will be less than 1 dB. Research actually indicates as low at 0.5 dB in some cases (broad resonances).
Do you have a link for that research lying somewhere by chance?

#### solderdude

##### Major Contributor
I thought the Arche had built in EQ profiles for the different models?
See some measurements.
Not very inspiring and hinting towards a small increase in output resistance but not EQ.

Here is the Utopia (used in the article) on 0 and 120 Ohm.

judging from the plots in the article it seems to be a 0.6 dB boost = means the output resistance in Utopia mode = 10 Ohms
Myself I would not go higher than that.

This is NOT impedance matching by the way.

#### solderdude

##### Major Contributor
What amplifier has been used here or did you emulate those 120ohms by software? Can a beginner like myself recreate this graph?
It's an amplifier with 0.2 Ohm output resistance (own design/build) where a 120 Ohm resistor is connected in series with for this test.
Recently I began measuring with 10 and 33 Ohm as well as these are found in some amps and people worry about this.
Below and example of this

and below the HD800S

#### Colonel Bogey

##### Member
Adding to the anecdotal evidence: I have heard the cracking noise *once* only, while playing Also sprach Zarathustra very loud. I was trying out the Oratory settings for the RME Adi-2 and had increased volume a lot to hear (experience?) the 16 Hz organ note at the very begining.

Apart from that, I listen a lot to music with the Oratory EQ and have no issues.

##### Member
I don't understand the critics of this review. The truth is the headphone is exceptional sound quality wise but has one major flaw. In Amir's review he said it sounded good before it started clipping on him. I don't think anyone has to take an all or nothing approach on this. There are many people, myself included, that own Focal headphones and enjoy them. However, this is audio SCIENCE review, and I think mechanically this headphone is just not up to snuff with Amir's standard of quality, which includes design, not just sound. In the end Focal headphones are a "buy at your own risk" situation. It is not confirmed by anybody that this is a quality control issue, and in fact we have evidence from the company itself that this is intentional. Whether your specific pair clips or not, is besides the point. I think every customer should have confidence that they are buying a non clipping unit (especially at this price range), instead of leaving it up to a coin toss.
You are completely right.
I am disappointed by the situation, french company producing high quality audio equipment, as I am French also, I feel sorry for them to have to deal with these kind of troubles. They put themselves in a very disturbing situation with these clipping driver issue.

#### bidn

##### Member
Searching online, I see references to Clear "clipping." I suspect this is what they are talking about. If so, it is real flaw in this headphone.
The clipping is indeed a known protection feature of Focal headphone, they stated several times that it is designed to kick in when the SPL reach ear-deafening levels. I bought the Elear, Utopia, Elegia and Stellia after they became available and have been following the related threads at Head-Fi: on these threads a few persons mentioned experiencing this on a given track, but the vast majority (incl. me) couldn't as this would require turning the volume way to loud, for me far beyond my threshold of pain. I can't remember anyone saying this was a frequent phenomenon.
I find Focal TOTL headphones globally the best among the "big" trademarks, but they are indeed not for people listening at extreme loudness levels.

#### RayDunzl

##### Major Contributor
Central Scrutinizer
The clipping is indeed a known protection feature of Focal headphone,
How is this protection feature implemented?

(Sorry if I missed it, many posts)

#### solderdude

##### Major Contributor
It's the cone hitting the magnet assembly or perhaps the maximum stretch of the rubber roll ring ?
Given the sound it makes I would think its the cone hitting the magnet.

#### Joachim Herbert

##### Active Member
Forum Donor
I do not buy into that protection argument. The clipping results from the very soft suspension of the driver, which is a deliberate design decision. You usually use that kind of suspension in non-ported (closed) speakers, not in open baffle designs as we find here. Its physics (see Thiele-Small parameters, also explains rise in impedance at a certain frequency).

Focal coming from chassis design must have been up to something to make that decision, and I believe they choose wisely. While the headphone may be at fault with extreme signals in the lower registers it is just brilliant with the stuff I listen to (jazz of all kinds, classical and 70s to 80s pop mostly, but not limited to this). I rarely let the dark knight rise.

This only goes to show that you should know your use case. Speaker (and headphone design) will always be a compromise.

As a boomboom complement to my focals I have an audioquest nighthawk, should I care for a bassy treat. But this did not leave its box for more than two years now.

#### Rock Rabbit

##### Active Member
I don't understand the graph
A 1khz tone is being played for a 60ohm headphone (focal clear).
In this graph, the 60hz frequency would be then perceived louder than other frequencies, so I hear more bass or thickness.
What is the cause for this 60hz resonance peak?
What is the relation between the 342 ohm and the 60hz?
What amp has been used here?
No peak in audio response due to low amp impedance output with constant voltage output even with that peak in hp impedance. Indeed there's only 1/6th the power at resonance...no peak in SPL

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#### HDavidson

##### Member
Maybe try for those who use equalization, you can put a high-pass filter that will get rid of parasitic noise at low frequencies.

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#### nhatlam96

##### Active Member
Forum Donor
I began measuring with 10 and 33 Ohm as well as these are found in some amps and people worry about this.
If it isnt too much work, could you make a graph especially for the focal clear with 0.2ohm, 10ohm, 33ohm and 120ohm?
So then I would have three examples at hand: Focal Clear, HD 559 and HD800.
The Focal Clear changes at around 60hz, HD559 changes at around 100hz and HD800 doesnt change at all. It would help me with here and here. Ive been researching topics like "do all amps or dacs sound the same" all the time and I finally got the money to buy myself various equipment to get to the bottom of this, like the Focal Clear, THX amp, vioectric V200 and many other amps. I would like to share my findings in a structured article with explanations, so any beginner can understand. In this week or the other, I will add a volume matching guide for beginners and output impedance explanation to my articles.

#### Helicopter

##### Major Contributor
Forum Donor
Three examples of music with extreme low bass of different genres:

Bass below 40 Hz with no overtones, so you won't hear it on a standard loudspeaker setup, is pretty normal these days. But with the right headphones and EQ you can.