|
About our testing:
Our testing rig uses the same hardware and software that manufacturers use when tweaking their own headphones. On the hardware end of the spectrum is our head and torso simulator, or HATS for short. HATS looks like an armless torso with a robot face and anatomically correct ears. Inside those ears are high-sensitivity microphones. The software we use is called SoundCheck, and is developed by our friends over at Listen, Inc. If you'd like to know more about our tests, read this article.
Frequency Response (3.35) 
How the test works:
Once the headphones are fit inside HATS's magical ears our testing is ready to begin. The frequency response test measures how much emphasis the headphones are attributing to any given frequency. We do this by playing by a frequency sweep where all the frequencies are being played back at the same volume. We then have HATS listen to that output, who then informs what levels each frequency was actaully played back at. The graph below represents the roller coaster ride of added and subtracted emphasis that the headphones provides.
What we found:
We found that the Panasonic RP-HC55 performs ok overall, but has some issues with underemphasis. The curve starts out fine. The bass has an interesting curve, emphasizing the low end, dipping down a bit, then coming back up again. After that peak, which is somewhere around 700Hz, both channels decrease steadily past the bottom limit. Any of the frequencies that occur under the bottom limit could sound a bit soft. The left channel dips down a bit further than we'd like to see, but again, the difference won't be jarring. The left channel, overall, is ever so slightly louder than the right channel, but a uniform error like this one could be due to a minor fit issue.
How the Panasonic RP-HC55 compares:
Since the RP-HC55s are the second set of active-cancelling in-ear headphones we've reviewed, we can now say, with the confidence only sweeping generalization can bring, that all such headphones have a poor frequency response. Actually, although the RP-HC55s and ATH-ANC3s have similar scores, you an see that they have very different response curves. While the RP-HC55 tends to underemphasize the area between 1kHz and 10kHz, the ATH-ANC3 pumps it past the top limit.
The RP-HC55 Finds itself in the top half of the comparison phones in terms of a score. The two that did better, the SE420 and MM 50 iP, are both (currently) in the top five on our ratings table (being #5 and #1 respectively), so the RP-HC55 shouldn't feel too bad about falling a bit behind them.
Distortion (1.62)
How the test works:
To test distortion, we again play a series of frequences through the headphones and into HATS's awaiting ears. Each frequency in the series, which ranges from 100Hz to 10kHz, is played at the same decibel level. The below graph shows any difference between the original soundwave and what HATS ended up hearing. As before, the green line is the left channel, the red line is the right channel, and the frequencies tested are lined up along the bottom. The percentage of distortion is measured by the Y-axis. Keep in mind that anything over 3% distortion is noticeable and the closer the line is to zero, the better.
What we found:
If you take someone who's never bought headphones before, showed them this trend and only told them it was a graph of distortion, they'd point to the spike at the end and say, "so that's bad, right?" As we said in this test's intro, anything over 3% is noticeable. This line comes close to 4%, which is bad. Of course, the spike only encompasses a tiny range, but the distortion therein is significant. This being said, we were impressed with teh low levels of distortion elsewhere. This spike is likely an unfortunate side-effect of the active noise cancellation.
This result is the norm for active-cancellers. Out of all the headphones we test, active-cancellers generally have poor distortion tests. Of course, there are exceptions and some headphones actually have very little distortion when their noise cancellation is turned off (high-five, Denon AH-NC732). The reason for this is that active cancellation works by playing back sounds that aren't really there. Some will cancel out background noise as intended, but invariably some won't.
Since the RP-HC55s can't turn off their active cancellation, you're stuck with this distortion spike.
How the Panasonic RP-HC55 compares:
The RP-HC55 does about as well as the ATH-ANC3, a fellow active-canceller. The AH-NC732 is also an active-canceller, but it can switch its cancellation off, netting an absurdly low distortion score. A score like the RP-HC55s basically means you don't necessarily care all that much about distortion. This is likely to be the case, since both the in-ear form factor and active noise cancellation feature mean you're probably taking these headphones outside, where things are noisy. These headphones are not for audiophiles.
Tracking (5.99)
How the test works:
Like the two previous tests, our tracking test examines a frequency sweep, as filtered through the headphones and collected by HATS and its robotic ears. This time we're measuring how loud each channel is compared to the other. If the headphones had perfect tracking, the graph below would be a horizontal line at the zero mark. Since this is unrealistic, we should probably inform you that anything above the zero line means the left channel is louder and anything below the zero line means the left channel is louder.
What we found:
As we saw on the frequency response graph, the right channel is a bit louder than the left. Again, this could be a small fit issue; in any case, small changes like this don't really affect the score. The troubling bit is towards the high end, where the response gets crazy a bit faster than it should have.
One thing we should mention is that, while the emphasis on the right channel could be a fit issue (the change is pretty uniformly skewed towards one side), we did notice that, throughout our tests, the right channel tended to be louder than the left. The graph pictured at right represents the best score we were able to achieve, despite it being a bit off-kilter. The take-away from this score probably isn't that the right channel is louder, but rather that positioning the ear buds matters.
How the Panasonic RP-HC55 compares:
The RP-HC55 didn't do half bad on this test. It did better than the AH-NC732, which is our current poster child for active-cancellation done right. It didn't fare well compared to other headphones, however, since its jumps from left to right were a bit more severe than other headphoens pictured below. If you'll notice, most headphones tend ot have a relatively straight line up until about 10kHz, at which point the graph gets all jumbly.
Maximum Usable Volume (9.66)
How the test works:
This test is like a series of distortion tests, each one performed at an ever-increasing volume level. What we're looking for is when the overall distortion level passes 3%. At that point, distortion is noticeable and pumping the volume up further will only exacerbate things.
What we found:
The RP-HC55 was actually capable of an impressive volume level given its poor distortion score. We were able to squeeze 118.58 decibels out of it, which is less than 2 dB from the max level we award points for. Anything past 120dB is just going to be harmful, and we here at HeadphoneInfo.com care about your health. Unless you have difficulties hearing to begin with, 120dB should be plenty.
Isolation (8.10)
How the test works:
Isolation refers to your headphones' ability to shield you from outside noise. To test this, we fit the headphones onto HATS, then blast the area with pink noise. Pink noise, for those too lazy to Wikipedia it and those that did but found the wording overly obtuse, is when all frequencies are being played back at an equal power level. This means that lower frequencies are played at a higher decibel level than high frequencies. Yes, Wikipedia, it is inversely proportional, but you could throw less equally obtuse jargon in the definition. Jeez. On this graph, blue is active cancellation, green is passive cancellation (block out sound by virtue of physically obstructing the path between external sound and your ear drum).
What we found:
The RP-HC55s actually performed quite well here. The active cancellation blocked out a big chunk of bass noise, which is typically all that active cancellation is good for. It also managed to block out a bit of the mid-to-high sounds as well, which was a nice bonus. Further, it appears the active cancellation never added more noise than it reduced. We could definitely hear a high-pitched whine when we turned on cancellation in a quiet room, which is why we were a bit surprised to see the blue line didn't dip below the green one towards the high end. Although that whine might annoy you under ideal listening conditions, we never noticed it when we hit the streets, which is where you're supposed to be wearing these things anway.
How the Panasonic RP-HC55 compares:
Our ATH-ANC3 hypothesis has been destroyed: it seems like active cancellation can succeed to some extent in a pair of in-ears. This didn't score as well as a great pair of in-ears, like the SE420, so the technology probably could've been obviated for a nice pair of foam plugs. The ATH-ANC3 does block out more bass sound than the SE420s do, but only by a bit.
Leakage (6.00)
How the test works:
We test leakage by playing pink noise through the headphones at a set level. We have a microphone stationed a set distance away to pick up on any noise leaking out of the headphone-ear seal.
What we found:
As expected, these headphones weren't the best at controlling leakage. They weren't bad compared to all headphones, but for a set of in-ears they weren't good. The performance has to do with how active cancellation works. Since it requires a microphone to listen to outside noise, the headphones require tiny holes to be punched in their plastic casing. This lets sound trainsfer in and out of the headphones more easily (as evidenced by the poor passive isolation score above). Of course, since you'll feel isolated from your surroundings due to the active cancellation, it's hard to gauge how much sound is leaking out of your headphones. The RP-HC55s didn't leak as much as Audio-Technica's ATH-ANC3s, but they weren't nearly as good as a set of regular in-ear headphones.
|
