Headphone & Amp Impedance Questions? Find the answers here!
Sep 2, 2021 at 4:10 PM Post #361 of 400

theaudiologist1

100+ Head-Fier
Joined
Sep 23, 2019
Posts
223
Likes
26
Location
Uranus
If the amp can deliver 28mW into 300 ohms it means that the amp can reach at least ~2.9V into 300ohm. If anything, the voltage slightly goes up as the load's impedance increases so I would assume the amp would deliver around ~18mW into 470ohms which is enough for 111~112dB SPL if the efficiency is 99dB/mW.
Despite that my very dynamic classical music (specially the DSD ones which for some reason are quiter than the PCM ones) is quiet on my 470Ohm headphones, and can't pickup some of the quieter sounds that my 35Ohm headphone does. If it could reach 111dB SPL I don't know what the problem is. The max impedance my heapdhone has is around 900Ohm in the lowerend.
 
Sep 2, 2021 at 4:18 PM Post #362 of 400

VNandor

500+ Head-Fier
Joined
Oct 17, 2014
Posts
571
Likes
227
Despite that my very dynamic classical music (specially the DSD ones which for some reason are quiter than the PCM ones) is quiet on my 470Ohm headphones, and can't pickup some of the quieter sounds that my 35Ohm headphone does. If it could reach 111dB SPL I don't know what the problem is. The max impedance my heapdhone has is around 900Ohm in the lowerend.
I didn't mention that it would reach these levels only at the moments when the music you are listening to is peaking at 0dBFS. Classical music typically have huge differences between the average and the peak levels. 25dB is fairly typical in my experience, some can even go as far as -30dB below the peak. So in these cases, you would listen at an average of maybe 81-86dB SPL and only the loudest parts would get to 111dB SPL. I'm guessing the loud parts of classical music is still loud enough, right?

The impedance swing at the low end shouldn't be a problem but the explanation might be a bit counter intuitive. A bigger impedance always draws less current for a given voltage. This could also mean that the headphone could be quieter around the impedance peak since less power is drawn, however I would expect the efficiency to also peak there which would mean that the headphone does require less power anyways to reach the same SPL. If you had a frequency response graph as well as an impedance graph of the headphone, the power drawn for a constant SPL over the frequencies could be calculated but it's kind of pointless, at least it would show that the headphone most likely doesn't need more power where the impedance peaks.
 
Last edited:
Sep 2, 2021 at 6:17 PM Post #363 of 400

theaudiologist1

100+ Head-Fier
Joined
Sep 23, 2019
Posts
223
Likes
26
Location
Uranus
I didn't mention that it would reach these levels only at the moments when the music you are listening to is peaking at 0dBFS. Classical music typically have huge differences between the average and the peak levels. 25dB is fairly typical in my experience, some can even go as far as -30dB below the peak. So in these cases, you would listen at an average of maybe 81-86dB SPL and only the loudest parts would get to 111dB SPL. I'm guessing the loud parts of classical music is still loud enough, right?
Yes the loud parts are indeed very loud. I'm worried more about the quiet parts. I'm sure I listen to music at around 80dB average since 90dB would hurtmy ears. But assuming the peaks were 110dB and the dynamic range is 40dB (high even for classical) that means that the quietest parts of the music is at 70dB correct?

The impedance swing at the low end shouldn't be a problem but the explanation might be a bit counter intuitive. A bigger impedance always draws less current for a given voltage. This could also mean that the headphone could be quieter around the impedance peak since less power is drawn, however I would expect the efficiency to also peak there which would mean that the headphone does require less power anyways to reach the same SPL. If you had a frequency response graph as well as an impedance graph of the headphone, the power drawn for a constant SPL over the frequencies could be calculated but it's kind of pointless, at least it would show that the headphone most likely doesn't need more power where the impedance peaks.
I could not find a sensitivity graph for the R70x (my 470 Ohm headphones).
 
Sep 2, 2021 at 7:23 PM Post #364 of 400

bigshot

Headphoneus Supremus
Joined
Nov 16, 2004
Posts
23,126
Likes
4,758
Location
Hollywood USA
I don’t believe many commercial recordings have +30dB spikes above the normal peak level. I’ve found a couple like that. They were unlistenable. The normal volume was too low to listen to without turning the volume WAY up, and I spent the entire time turning the volume up and down so I could hear the quiet parts and avoid ripping the roof off the house. More is not better.

This sounds to me like an extrapolation of the common “fact” that orchestral peak levels reach 110dB. And yes they do if you stand directly in front of the brass section in a live performance. But no one listens to orchestral music like that. The front row might be 50 feet or more back from that. Volume level ten yards away isn’t the same as volume level an inch from your ear. Recordings are mixed to give a natural perspective from a theoretical best seat in the house. It isn’t mixed to sound like you’re sitting in the musician’s lap.

The most dynamic commercial recordings have a dynamic range of about 55dB. That reflects how it sounds in a concert hall. In fact, that is probably more dynamic than most concert halls. 110dB is past the flinch point and pushing the threshold of pain. When was the last time you attended a classical concert or listened to a symphony CD and experienced discomfort from volume spikes? That just doesn’t happen.

The peaks for very loud music are between 80 and 85 dB, not anywhere near 110.
 
Last edited:
Sep 2, 2021 at 10:31 PM Post #365 of 400

theaudiologist1

100+ Head-Fier
Joined
Sep 23, 2019
Posts
223
Likes
26
Location
Uranus
I don’t believe many commercial recordings have +30dB spikes above the normal peak level. I’ve found a couple like that. They were unlistenable. The normal volume was too low to listen to without turning the volume WAY up, and I spent the entire time turning the volume up and down so I could hear the quiet parts and avoid ripping the roof off the house. More is not better.

This sounds to me like an extrapolation of the common “fact” that orchestral peak levels reach 110dB. And yes they do if you stand directly in front of the brass section in a live performance. But no one listens to orchestral music like that. The front row might be 50 feet or more back from that. Volume level ten yards away isn’t the same as volume level an inch from your ear. Recordings are mixed to give a natural perspective from a theoretical best seat in the house. It isn’t mixed to sound like you’re sitting in the musician’s lap.

The most dynamic commercial recordings have a dynamic range of about 55dB. That reflects how it sounds in a concert hall. In fact, that is probably more dynamic than most concert halls. 110dB is past the flinch point and pushing the threshold of pain. When was the last time you attended a classical concert or listened to a symphony CD and experienced discomfort from volume spikes? That just doesn’t happen.

The peaks for very loud music are between 80 and 85 dB, not anywhere near 110.
That's the problem: when listening to classical, in order to hear the quiet parts I have to put my amp on hi gain, max volume to hear them, and then the loud parts hurts my ears and I have to turn down the volume. Don't know how many dB the peaks are.

In one of the reviews for my DAC/AMP it said it can drive the 89dB/mW 150Ohm headphone on low gain at half volume and it gets loud. I put it on high gain max volume and it's still quiet (only with classical though).

Another thing: my 32Ohm headphones are closed while my 470Ohm headphones are open. Maybe that's why it picks up the quieter sounds less?
 
Last edited:
Sep 3, 2021 at 2:14 AM Post #366 of 400

bigshot

Headphoneus Supremus
Joined
Nov 16, 2004
Posts
23,126
Likes
4,758
Location
Hollywood USA
Your headphones and amp are probably fine. The problem is bad engineering. More dynamics isn't automatically better. Too much dynamics is actually worse than too little. I find that BIS is the label that is the biggest offender at that.

Human hearing can only hear a dynamic range of about 40dB at a time. If there are immediate contrasts in volume that go beyond that, it either is irritatingly loud or you try to strain to hear it because it is too quiet to hear. It takes ears a minute or two to adjust to a lower or louder volume level. That's why the dynamics in commercially recorded music don't generally go much further than that.
 
Last edited:
Sep 3, 2021 at 9:39 AM Post #367 of 400

71 dB

Headphoneus Supremus
Joined
Sep 17, 2017
Posts
1,697
Likes
561
Location
Helsinki, Finland
This sounds to me like an extrapolation of the common “fact” that orchestral peak levels reach 110dB. And yes they do if you stand directly in front of the brass section in a live performance. But no one listens to orchestral music like that. The front row might be 50 feet or more back from that. Volume level ten yards away isn’t the same as volume level an inch from your ear. Recordings are mixed to give a natural perspective from a theoretical best seat in the house. It isn’t mixed to sound like you’re sitting in the musician’s lap.
An orchestra is not a small point source. When you stand "directly in front of the brass section", you might be 5 feet from the closest brass player, but some other brass players are much further away from you. You can't be 5 feet away from all players of the orchestra at the same time. That's why when you integrate the acoustical power at your ears, it gets "only" to 110 dB SPL. When you walk away to the "best seat in the house", your distance to those players who where originally furthest away from you increases much less relatively (relative distance matter in distance attenuation calculations). Your distance to the closest player perhaps 10-folds ( -20 dB), but your distance to the furthers players maybe only doubles ( -6 dB) or even less. That's why the integrated acoustical power at your ears doesn't drop 20 dB. Also, the hall has reverberation. It is far from a free-field situtation. The reverberation (without early reflections and direct sound) is the same level everywhere in the hall and increases the overall sound pressure level significantly.

Reverberation radius rH is the distance where the sound energy densities of the direct sound and the reverberation are equal. It can be calculated using the formula

rH = SQRT ( Q * R / 𝜋 ) / 4,

where SQRT is simply square root, Q is directivity index of the sound source and R is room constant related to total absortion area A:

R = A / (1 - ā),

where ā is the average absorption coefficient.

Let's assume a concert hall of the size 40 m x 30 m x 15 m (133' x 100' x 50' for Americans). Desirable value for reverberation RT for an orchestral music hall of this size is about 1.8 seconds. Reverberation time can be calculated using the simple formula (there are better formulas, but this will do for this example):

RT = 0,161 * V / A,

where V is the volume of the hall. So, from this formula we get that total arborption are A = 0,161 * 40 * 30 * 15 / 1.8 = 1610 m². Now we can calculate the needed average absorption coefficient ā for the hall: ā = A / S = 1610 / (2 * 40 * 30 + 2 * 30 * 15 + 2 * 30 * 15) = 1610 / 4500 = 0.36. Now we can calculate the room constant : R = 4500 / (1 - 0.36) = 7031 and finally the reverberation radius assuming Q = 1.5 (almost omnidirectional sound source): rH = SQRT ( 1.5 * 7031 / 3.14) / 4 = 14.5 meters (almost 50 feet).

This means that 50 feet away from the orchestra we are in the border of near field and free field. I'd say the peaks for the listeners are 90 - 95 dB.

The most dynamic commercial recordings have a dynamic range of about 55dB. That reflects how it sounds in a concert hall. In fact, that is probably more dynamic than most concert halls. 110dB is past the flinch point and pushing the threshold of pain. When was the last time you attended a classical concert or listened to a symphony CD and experienced discomfort from volume spikes? That just doesn’t happen.

The peaks for very loud music are between 80 and 85 dB, not anywhere near 110.
I wouldn't call music with peaks of 80 dB "very loud". Loud maybe. Peaks of 85 dB is perhaps "very loud", but yes, 110 dB is "damage your hearing in minutes" loud.
 
Sep 3, 2021 at 10:28 AM Post #368 of 400

71 dB

Headphoneus Supremus
Joined
Sep 17, 2017
Posts
1,697
Likes
561
Location
Helsinki, Finland
That's the problem: when listening to classical, in order to hear the quiet parts I have to put my amp on hi gain, max volume to hear them, and then the loud parts hurts my ears and I have to turn down the volume.
There is of course less dynamic types of classical music compared to romantic era and newer orchestral music.
 
Sep 3, 2021 at 10:48 AM Post #369 of 400

theaudiologist1

100+ Head-Fier
Joined
Sep 23, 2019
Posts
223
Likes
26
Location
Uranus
There is of course less dynamic types of classical music compared to romantic era and newer orchestral music.
If you're talking about periods, then I hardly listen to classical. I listen to Baroque and Romantic. I don't know any clssical composers outside the big 3 (Mozart,Beethoven,Haydn) besides J.C. Bach. And I did notice Romanic was a lot more dynamic than Baroque.
 
Sep 3, 2021 at 12:10 PM Post #370 of 400

71 dB

Headphoneus Supremus
Joined
Sep 17, 2017
Posts
1,697
Likes
561
Location
Helsinki, Finland
If you're talking about periods, then I hardly listen to classical. I listen to Baroque and Romantic. I don't know any clssical composers outside the big 3 (Mozart,Beethoven,Haydn) besides J.C. Bach. And I did notice Romanic was a lot more dynamic than Baroque.
1400 - 1600 Renaissance
1600 - 1750 Baroque
1750 - 1820 Classical
1820 - 1914 Romantic

Romantic era definitely is more dynamic. Hector Berlioz "invented" orchestration. Orchestras became bigger. The music became more turbulent and emotional.

However, I was talking about types of music: Instrumental / chamber / orchestra. If romantic era orchestral music is too dynamic, chamber music can be a nice option.
 
Last edited:
Sep 3, 2021 at 12:40 PM Post #371 of 400

theaudiologist1

100+ Head-Fier
Joined
Sep 23, 2019
Posts
223
Likes
26
Location
Uranus
1400 - 1600 Renaissance
1600 - 1750 Baroque
1750 - 1820 Classical
1820 - 1914 Romantic

Romantic era definitely is more dynamic. Hector Berlioz "invented" orchestration. Orchestras became bigger. The music became more turbulent and emotional.

However, I was talking about types of music: Instrumental / chamber / orchestra. If romantic era orchestral music is too dynamic, chamber music can be a nice option.
That's something I noticed too, all the concertos and symphonies tend to be the most dynamic and hard to drive. I myself like all the types of Baroque/Romantic, as long as they have no vocals (I HATE vocals), but my favorites are always the concertos and symphonies.
 
Sep 4, 2021 at 7:00 AM Post #372 of 400

gregorio

Headphoneus Supremus
Joined
Feb 14, 2008
Posts
4,127
Likes
2,245
[1] This means that 50 feet away from the orchestra we are in the border of near field and free field. I'd say the peaks for the listeners are 90 - 95 dB.
[2] I wouldn't call music with peaks of 80 dB "very loud". Loud maybe. Peaks of 85 dB is perhaps "very loud", but yes, 110 dB is "damage your hearing in minutes" loud.
1. You haven't accounted for absorption from the musicians, other audience members and carpets and chairs. Probably your figure isn't far wrong though, maybe a few dB less in most cases.

2. We have to be careful here, it's not a fixed point, even for the same individual! There's a perceptual effect at work here that many don't consider. I don't believe it's fully understood yet (although there are various theories/suggestions of course) but for some reason our perception of loudness changes with room size and distance to the sound source. Cinemas are calibrated to 85dB at a listening position in about the middle of the cinema, 85dB in a cinema is loud but not very loud. However, 85dB at the listening position in a sitting room or an good sized sound editing room sounds significantly louder. Perceptually, the difference in loudness of 85dB at the listening position in a very large room (cinema or concert hall) and an average sitting room/editing room is typically about 6-7dB. EG. 78dB in your sitting room sounds roughly the same loudness as 85dB in a cinema/concert hall. This is very rough though, the difference can be as little as about 3dB and in the case of a smaller room and sitting just a couple of meters from the speakers, as much as about 11dB. Clearly then, to some people, 80dB in their home listening environment could indeed be perceived as "very loud", especially if they're are older.
Romantic era definitely is more dynamic. Hector Berlioz "invented" orchestration. Orchestras became bigger.
Berlioz didn't invent orchestration. Orchestration had been around for centuries before Berlioz was even born, however he did write the definitive book on the subject (including it's prior history), it became required reading for composer students and was therefore very influential. I agree though that orchestras gradually became bigger and more dynamic. In Mozart's day an orchestra was around 40 musicians, Bach's typically around 20 - 30 and by the early part of the C20th, it became it's current standard full symphony orchestra size of around 90. That's in addition to the more sudden/dramatic changes in dynamics often employed by the Romantic era and later composers and the fact that most modern orchestral instruments are significantly louder than their Baroque and even Romantic era ancestors.
That's something I noticed too, all the concertos and symphonies tend to be the most dynamic and hard to drive. I myself like all the types of Baroque/Romantic, as long as they have no vocals (I HATE vocals), but my favorites are always the concertos and symphonies.
Generally, symphony recordings have the largest dynamic ranges of all music genres, particularly the later romantic period symphonic composers such as Mahler, the post romantics such as R. Strauss and some of the impressionists and later composers, such as Ravel and Stravinsky.

G
 
Sep 4, 2021 at 7:50 AM Post #373 of 400

71 dB

Headphoneus Supremus
Joined
Sep 17, 2017
Posts
1,697
Likes
561
Location
Helsinki, Finland
1. You haven't accounted for absorption from the musicians, other audience members and carpets and chairs. Probably your figure isn't far wrong though, maybe a few dB less in most cases.
Yes, I didn't do that, because I just wanted to make a simplified calculation that is definitely a little bit off, but gives us the ballpark.

2. We have to be careful here, it's not a fixed point, even for the same individual! There's a perceptual effect at work here that many don't consider. I don't believe it's fully understood yet (although there are various theories/suggestions of course) but for some reason our perception of loudness changes with room size and distance to the sound source. Cinemas are calibrated to 85dB at a listening position in about the middle of the cinema, 85dB in a cinema is loud but not very loud. However, 85dB at the listening position in a sitting room or an good sized sound editing room sounds significantly louder. Perceptually, the difference in loudness of 85dB at the listening position in a very large room (cinema or concert hall) and an average sitting room/editing room is typically about 6-7dB. EG. 78dB in your sitting room sounds roughly the same loudness as 85dB in a cinema/concert hall. This is very rough though, the difference can be as little as about 3dB and in the case of a smaller room and sitting just a couple of meters from the speakers, as much as about 11dB. Clearly then, to some people, 80dB in their home listening environment could indeed be perceived as "very loud", especially if they're are older.
Music I hate at 85 dB is torturously loud to me while music I love at 85 dB is probably awesome level. Yeah, how loud something is to someone somewhere is subjective. Here we were talking about loudness in concert hall. When I did the mixing course last year, the teacher instructed to use 80-85 dB levels while mixing. Anyway, this discussion wasn't about how loud people find the sound. It was about how many decibels there is. For example cinemas are calibrated to 85 dB regardless of what an older person thinks about it. It is considered generally loud but not very loud = good level.

Berlioz didn't invent orchestration. Orchestration had been around for centuries before Berlioz was even born, however he did write the definitive book on the subject (including it's prior history), it became required reading for composer students and was therefore very influential. I agree though that orchestras gradually became bigger and more dynamic. In Mozart's day an orchestra was around 40 musicians, Bach's typically around 20 - 30 and by the early part of the C20th, it became it's current standard full symphony orchestra size of around 90. That's in addition to the more sudden/dramatic changes in dynamics often employed by the Romantic era and later composers and the fact that most modern orchestral instruments are significantly louder than their Baroque and even Romantic era ancestors.
That's why I wrote "invented". :relieved:

Generally, symphony recordings have the largest dynamic ranges of all music genres, particularly the later romantic period symphonic composers such as Mahler, the post romantics such as R. Strauss and some of the impressionists and later composers, such as Ravel and Stravinsky.

G
I have a boxset of Ravel's orchestral works on Brilliant Classics (Eliahu Inbal) and the combination of how it has been recorded and Ravel's music makes it too dynamic to enjoy. That's the worst case of "too much dynamic variation" in my classical music collection. Other recordings of "very dynamic music" just work better.
 
Sep 4, 2021 at 9:31 AM Post #374 of 400

gregorio

Headphoneus Supremus
Joined
Feb 14, 2008
Posts
4,127
Likes
2,245
[1] Here we were talking about loudness in concert hall. When I did the mixing course last year, the teacher instructed to use 80-85 dB levels while mixing. Anyway, this discussion wasn't about how loud people find the sound. It was about how many decibels there is. For example cinemas are calibrated to 85 dB regardless of what an older person thinks about it. It is considered generally loud but not very loud = good level.

[2] That's why I wrote "invented". :relieved:
1. Firstly, you seem to have missed my point: In addition to the subjective opinion that everyone has about what is loud, there's also a perceptual difference regarding decibels in significantly larger rooms and I specifically mentioned it because obviously there's a very significant difference between the size of a concert hall and the size of a consumer's listening environment. Using the cinema analogy again, 85dB in a cinema is considered "loud but not very loud", while exactly the same 85dB in a home listening environment is significantly louder, EG. Very loud, and that's for the same person with the same subjective opinion on what is loud! Secondly, as a calibrated level, 80-85dB is too high a level for mixing, unless it's film mixing in a full sized dubbing theater. Even film mixing in a sitting room sized environment should be done at a lower level than that, and films are mixed much quieter than music! As a peak (rather than a calibrated) level, 80-85dB for music mixing is probably about right, depending on the music.

2. And that why I corrected you, because he didn't "invented" orchestration, he just wrote a book about it's prior history and current (at the time) usage!

G
 
Last edited:
Sep 4, 2021 at 10:18 AM Post #375 of 400

71 dB

Headphoneus Supremus
Joined
Sep 17, 2017
Posts
1,697
Likes
561
Location
Helsinki, Finland
1. Firstly, you seem to have missed my point: In addition to the subjective opinion that everyone has about what is loud, there's also a perceptual difference regarding decibels in significantly larger rooms and I specifically mentioned it because obviously there's a very significant difference between the size of a concert hall and the size of a consumer's listening environment. Using the cinema analogy again, 85dB in a cinema is considered "loud but not very loud", while exactly the same 85dB in a home listening environment is significantly louder, EG. Very loud, and that's for the same person with the same subjective opinion on what is loud! Secondly, as a calibrated level, 80-85dB is too high a level for mixing, unless it's film mixing in a full sized dubbing theater. Even film mixing in a sitting room sized environment should be done at a lower level than that, and films are mixed much quieter than music! As a peak (rather than a calibrated) level, 80-85dB for music mixing is probably about right, depending on the music.
I admit I missed your point of comparing concert halls and smaller rooms. In a concert the audience can't tell the orchestra to play quieter (only the conductor can do that) so the audience is at the mercy of what is happening or walk out. At home I can turn the volume down if the music is too loud for me. Or up if it is not loud enough. I kind of agree with you about the mixing levels. I felt that the overall volume levels used in the course were about 5 dB too high, but that's my opinion. Not only that, but I instantly noticed that the stereo image is way off to the left and mentioned about it to the teacher. The Genelec 8331A speakers they had should give very sharp and accurate soundstage in a studio room with proper acoustics, but that wasn't the case at all. Turned out the DAC had a glitch that made the right channel no less than 8 dB quieter! After fixing the issue the soundstage was as precise as expected.

2. And that why I corrected you, because he didn't "invented" orchestration, he just wrote a book about it's prior history and current (at the time) usage!

G
I am not a Berlioz expert, but I think his contributions were more than just writing a book. You do fine job at correcting people whenever needed, but there are situations where it becomes nitpicking.
 

Users who are viewing this thread

Top