prodo123
New Head-Fier
- Joined
- Nov 10, 2012
- Posts
- 25
- Likes
- 23
Update: See post #3 for download link to graphs and recordings.
**UPDATE 2: post #36 has even better data.**
There is no real difference in sound quality between balanced and unbalanced other than the elimination of crosstalk.
Introduction
I work as an audio engineer on the side. Having worked with numerous mics, I am very familiar with the concept of balanced signals. When I first heard of the concept of "balanced headphones" I thus immediately called it snake oil, as there is no return ground in its implementation. This is what we call a quasi-balanced line:
Sourced from Rane.com
What most "balanced headphones" do is snip the ground/shield from a true balanced cable, resulting in a cable as described in the diagram above as #17/18, except the RCA jack is connected to the headphone earpiece. The ramification of this implementation is a mere doubling of the voltage applied to the speakers, which leads to the claim of "double the slew rate." Most claims concerning this effect claims better bass response since the speakers are driven in push/pull.
This "slew rate" myth is somewhat unfounded, since headphones are already driven in push/pull in an unbalanced line. The signal itself is alternating voltages to create sound, and the amount of time it takes to form the charge in the coil necessary to move it is beyond what humans can perceive: ~3µs, or 3x10^-6 seconds. In practice, both sides of the coil are charged instantaneously by an unbalanced signal, and is electrically identical to a quasi-balanced signal being sent at half of the unbalanced signal's voltage.
Another claim being made for balanced headphones stem from the fact that balanced microphones are able to take advantage of circuitry to reject common-mode noise. This has more credibility in terms of theory. In a properly grounded but unbalanced system, any voltage applied to the ground is drawn to the ground and thus any interference in the signal line remains. In a closed system such as a PMP, however, the ground is simply a common return path to the battery, but this common ground is shared by all the components in the device, causing noise and crosstalk.
On a balanced headphone line, however, interference creates a voltage difference on both sides of the speaker. As long as the voltage induced by interference is equal on both the hot and cold lines of a balanced connection there should be no noticeable degradation in the signal. This is similar to the way that phantom power does not affect a mic signal. By isolating left and right channels and eliminating crosstalk, this noise rejection should theoretically provide some quality boosts. Just how much of a difference it makes depends on how long the cables are, though.
This brings another issue addressed by balanced headphones: crosstalk. This is the claim that in my opinion makes most sense, as not all of the power sent to the solenoid inside the headphone is not converted to mechanical energy. By separating left ground/cold from right ground/cold one eliminates any chance that the left channel might leak into the right and vice versa.
(If you find any errors in any of these, please let me know as I've only briefly thought about this)
Methodology
The project involves a recabled Sennseiher HD 25-1 II, using 26 AWG 19-strand SPC cable provided by navships, gold-plated connectors for the headphone, gold-plated 3.5mm TRRS plug, gold-plated 3.5mm TRRS-to-TRS adapter and gold-plated 3.5mm TRRS to dual 6.25mm TRS balanced breakout cable.
TRRS was chosen for the 4-conductor and slim profile. The conductors are configured so that left and right alternate:
T - Left +/Hot
R - Right +/Hot
R - Left -/Cold
S - Right -/Cold
The headphone was braided in a 4-strand Litz braid such that left hot/cold and right hot/cold form twisted pairs respectively. This twisted pair configuration was extended into dual TRS using the custom adapter.
The unbalanced 3.5mm TRS adapter simply shorts the left cold and right cold to form a common ground. As such, this only uses a 3-wire braid.
The audio source is a Focusrite Scarlett 2i2, which has balanced monitor outputs in the rear and unbalanced headphone output in the front, running at 24/96. All audio samples were 16/44.1 lossless to ensure maximum quality. Output volumes were subjectively matched using the Monitor and Headphone volume controls.
The choice of audio source may cause some issues with some readers, since it is not an "audiophile" source, but it is of note that it provides both unbalanced and balanced output. This is the main reason I chose this: it eliminates any variation caused by different audio sources.
Music files tested were:
Sweet Dreams (Are Made of This) by Eurythmics
Bach's Unaccompanied Cello Suite No.1, BWV 1007: Sarabande, performed by Yo-Yo Ma
Lateralus by Tool
Babe I'm Gonna Leave You by Led Zeppelin
Subjective Analysis
Sweet Dreams (Are Made of This) by Eurythmics
The intro to Sweet Dreams has heavy pan effects and quick bass beats that should bring out the main advantages of balanced lines. Unsurprisingly, the lack of crosstalk cleans up the presentation immensely and gives the impression of a wider soundstage. Bass notes are cleaner and smoother, but the response is identical between unbalanced and balanced. Note separation is also better.
Bach's Unaccompanied Cello Suite No.1, BWV 1007: Sarabande, performed by Yo-Yo Ma
This piece is much quieter than the others; as such, it tests for fine control of the diaphragm. Instead what I got from the balanced mode was, again, wider soundstage and better note separation. Notes sounded slightly smoother, but not by much. Unbalanced mode gave a harsher quality of sound.
Lateralus by Tool
This song is laden with intricate drumming that really benefits from a balanced headphone signal. Wider soundstage and cleaner notes are again present, but what really stood out was the impact of the drum beats. The introduction and the heavy guitar riffs also have much more impact with the balanced mode. However, bass response was the same.
Babe I'm Gonna Leave You by Led Zeppelin
The beginning measures of this song has weird panning from right to left which is made extremely apparent by balanced mode. Separation of left and right does some good for note response, but not much as the channels carry very different sounds already. What I did notice with balanced mode here was the ability to pick out minute details that are harder to distinguish with an unbalanced connection. For example, the small sample of "I can hear it calling me" at 1:40 is much, much cleaner with balanced mode.
Conclusion
Better Soundstage and Note Separation
I attribute this to the channel isolation that arises as a consequence of balanced mode. Without crosstalk, the left and right channels do not interfere with each other. This interference may also be caused by a slight mismatch of clocks between the channels, which again electrical isolation solves. The result is a cleaner sound which "widens" the soundstage and improves note response.
Detailed, Smoother Presentation, but Identical Bass Response
I still think this is a consequence of channel isolation, but it may also be some proof of this "slew rate" myth. The testing largely disproved the claimed improved bass response, but the amount of detail and smooth sound that results from balanced mode leads me to believe that this claim of "slew rate" should be investigated further and with better equipment than my ears.
Noise Rejection?
Short length cables are not privy to noise as much as longer ones. Thus it was natural that I experienced no problems with noise on both balanced and unbalanced cables. Mind you, this is in a place with over 300 wireless devices within 50 feet of me; if there should be any noise, this is the place.
Whether It's Worth It
I really wish it was.The difference in audio quality is absolutely there. They are tangible enough that I always prefer the balanced sound over the unbalanced, and this is coming from someone who completely did not believe in this. But the amount of trouble I had to go through to make this setup took months and months to source the right parts. And even then you are left with a headphone that cannot play on regular devices without an adapter.
But for the hardcore audiophile, balanced mode undoubtedly provides better sound than unbalanced. This may be because of the inherent channel isolation that comes with balanced mode, or it might also be the "slew rate" that people talk about; I do not know for sure and am not able to test for such at the moment. If you're willing to make the compromises that follow such a setup, go for it. The difference was so significant that it unwarranted my consideration of going for further ABX testing. Your experiences may vary.
-prodo123
**UPDATE 2: post #36 has even better data.**
There is no real difference in sound quality between balanced and unbalanced other than the elimination of crosstalk.
Introduction
I work as an audio engineer on the side. Having worked with numerous mics, I am very familiar with the concept of balanced signals. When I first heard of the concept of "balanced headphones" I thus immediately called it snake oil, as there is no return ground in its implementation. This is what we call a quasi-balanced line:
Sourced from Rane.com
What most "balanced headphones" do is snip the ground/shield from a true balanced cable, resulting in a cable as described in the diagram above as #17/18, except the RCA jack is connected to the headphone earpiece. The ramification of this implementation is a mere doubling of the voltage applied to the speakers, which leads to the claim of "double the slew rate." Most claims concerning this effect claims better bass response since the speakers are driven in push/pull.
This "slew rate" myth is somewhat unfounded, since headphones are already driven in push/pull in an unbalanced line. The signal itself is alternating voltages to create sound, and the amount of time it takes to form the charge in the coil necessary to move it is beyond what humans can perceive: ~3µs, or 3x10^-6 seconds. In practice, both sides of the coil are charged instantaneously by an unbalanced signal, and is electrically identical to a quasi-balanced signal being sent at half of the unbalanced signal's voltage.
Another claim being made for balanced headphones stem from the fact that balanced microphones are able to take advantage of circuitry to reject common-mode noise. This has more credibility in terms of theory. In a properly grounded but unbalanced system, any voltage applied to the ground is drawn to the ground and thus any interference in the signal line remains. In a closed system such as a PMP, however, the ground is simply a common return path to the battery, but this common ground is shared by all the components in the device, causing noise and crosstalk.
On a balanced headphone line, however, interference creates a voltage difference on both sides of the speaker. As long as the voltage induced by interference is equal on both the hot and cold lines of a balanced connection there should be no noticeable degradation in the signal. This is similar to the way that phantom power does not affect a mic signal. By isolating left and right channels and eliminating crosstalk, this noise rejection should theoretically provide some quality boosts. Just how much of a difference it makes depends on how long the cables are, though.
This brings another issue addressed by balanced headphones: crosstalk. This is the claim that in my opinion makes most sense, as not all of the power sent to the solenoid inside the headphone is not converted to mechanical energy. By separating left ground/cold from right ground/cold one eliminates any chance that the left channel might leak into the right and vice versa.
(If you find any errors in any of these, please let me know as I've only briefly thought about this)
Methodology
The project involves a recabled Sennseiher HD 25-1 II, using 26 AWG 19-strand SPC cable provided by navships, gold-plated connectors for the headphone, gold-plated 3.5mm TRRS plug, gold-plated 3.5mm TRRS-to-TRS adapter and gold-plated 3.5mm TRRS to dual 6.25mm TRS balanced breakout cable.
TRRS was chosen for the 4-conductor and slim profile. The conductors are configured so that left and right alternate:
T - Left +/Hot
R - Right +/Hot
R - Left -/Cold
S - Right -/Cold
The headphone was braided in a 4-strand Litz braid such that left hot/cold and right hot/cold form twisted pairs respectively. This twisted pair configuration was extended into dual TRS using the custom adapter.
The unbalanced 3.5mm TRS adapter simply shorts the left cold and right cold to form a common ground. As such, this only uses a 3-wire braid.
The audio source is a Focusrite Scarlett 2i2, which has balanced monitor outputs in the rear and unbalanced headphone output in the front, running at 24/96. All audio samples were 16/44.1 lossless to ensure maximum quality. Output volumes were subjectively matched using the Monitor and Headphone volume controls.
The choice of audio source may cause some issues with some readers, since it is not an "audiophile" source, but it is of note that it provides both unbalanced and balanced output. This is the main reason I chose this: it eliminates any variation caused by different audio sources.
Music files tested were:
Sweet Dreams (Are Made of This) by Eurythmics
Bach's Unaccompanied Cello Suite No.1, BWV 1007: Sarabande, performed by Yo-Yo Ma
Lateralus by Tool
Babe I'm Gonna Leave You by Led Zeppelin
Subjective Analysis
Sweet Dreams (Are Made of This) by Eurythmics
The intro to Sweet Dreams has heavy pan effects and quick bass beats that should bring out the main advantages of balanced lines. Unsurprisingly, the lack of crosstalk cleans up the presentation immensely and gives the impression of a wider soundstage. Bass notes are cleaner and smoother, but the response is identical between unbalanced and balanced. Note separation is also better.
Bach's Unaccompanied Cello Suite No.1, BWV 1007: Sarabande, performed by Yo-Yo Ma
This piece is much quieter than the others; as such, it tests for fine control of the diaphragm. Instead what I got from the balanced mode was, again, wider soundstage and better note separation. Notes sounded slightly smoother, but not by much. Unbalanced mode gave a harsher quality of sound.
Lateralus by Tool
This song is laden with intricate drumming that really benefits from a balanced headphone signal. Wider soundstage and cleaner notes are again present, but what really stood out was the impact of the drum beats. The introduction and the heavy guitar riffs also have much more impact with the balanced mode. However, bass response was the same.
Babe I'm Gonna Leave You by Led Zeppelin
The beginning measures of this song has weird panning from right to left which is made extremely apparent by balanced mode. Separation of left and right does some good for note response, but not much as the channels carry very different sounds already. What I did notice with balanced mode here was the ability to pick out minute details that are harder to distinguish with an unbalanced connection. For example, the small sample of "I can hear it calling me" at 1:40 is much, much cleaner with balanced mode.
Conclusion
Better Soundstage and Note Separation
I attribute this to the channel isolation that arises as a consequence of balanced mode. Without crosstalk, the left and right channels do not interfere with each other. This interference may also be caused by a slight mismatch of clocks between the channels, which again electrical isolation solves. The result is a cleaner sound which "widens" the soundstage and improves note response.
Detailed, Smoother Presentation, but Identical Bass Response
I still think this is a consequence of channel isolation, but it may also be some proof of this "slew rate" myth. The testing largely disproved the claimed improved bass response, but the amount of detail and smooth sound that results from balanced mode leads me to believe that this claim of "slew rate" should be investigated further and with better equipment than my ears.
Noise Rejection?
Short length cables are not privy to noise as much as longer ones. Thus it was natural that I experienced no problems with noise on both balanced and unbalanced cables. Mind you, this is in a place with over 300 wireless devices within 50 feet of me; if there should be any noise, this is the place.
Whether It's Worth It
I really wish it was.
But for the hardcore audiophile, balanced mode undoubtedly provides better sound than unbalanced. This may be because of the inherent channel isolation that comes with balanced mode, or it might also be the "slew rate" that people talk about; I do not know for sure and am not able to test for such at the moment. If you're willing to make the compromises that follow such a setup, go for it.
-prodo123