Hey guys!
Just recently, I was in the market for a portable headphone so decided to try out the Sennheiser HD238 which I was able to get brand new for $75.
Anyways, straight to the acoustics review:
My initial impressions of the headphone was that it was terrible. Simply terrible. The bass was uneven and muddy. The highs are almost non-existent. Both the bass and mid-range were distorted at high volume....well actually, it was strangely and annoyingly distorted throughout, didn't had to be at high volume. The vocals were horrible; they were unclear and soundstage was one of the worst I have ever heard.
However, after about 100 hours, the acoustics improved dramatically. The highs began to clear up and most of the distortion ceased. The bass also sharpened and overall, the HD238 became more balanced with better clarity.
I do should point out though; this was tested using only the digital amplifier on the Ipod Classic. But when I got my Corda Headsix, the acoustics improved once again. Despite that, the final review for the Sennheiser HD238 powered by the Corda Headsix and with lossless audio files on an Ipod Classic follows this set of pictures:
STOCK:
Strong response for bass but slightly muddy. However, bass is not very accurate; despite that, the mid-range great due to the range balance; also there is an extremely light distortion at high volume; and soundstage is just terrible and the high frequency sounds like its played through a brick wall.
So it begins my quest to improve the sound of the HD238:
Disassembling the headphone:
Note; the original cup foam has been taken out. In the next following set of pictures, I test out different materials as the back-material for the drivers of the headphone; hoping that finding the right material will improve the overall sound.
The materials tested:
1) Bandage Roll
2) Cotton Balls
3) Soft felt (blue or gray)
4) Medium felt (yellow)
5) Thick felt (black)
6) Aluminum foil
Songs of choice for testing:
1) Alive - Pearl Jam
2) Numb - Linkin Park
3) Gypsy - Fleetwood Mac
4) Layla (unplugged) - Eric Clapton
5) Angel - Massive Attack
Bandage Roll:
More impact on bass. slightly improved bass in terms of accuracy, soundstage still bad, vocals/high frequency has no change, distortion at high volume still exist, the mid-range doesn't seem to change.
Cotton Balls:
Bass is much more impactful. slightly more accurate and with less muddiness. vocals sound closer and more detailed and so the soundstage has improved. the mid-range seems to have no change, distortion at high volume still exist.
Soft Felt (Blue):
Impact of bass yields no difference to cotton balls. Mid-range and high-range sounds extremely close to cotton...I can't really tell the difference.
Medium Felt(Yellow):
Bass weakens; any difference in terms of accuracy and muddiness is unclear. the detail for vocals is an improvement over stock but not better than cotton. the mid-range seems to also have weakened. however, the distortion also seem to have disappeared. In essence, I feel this is more controlled than the bandage/cotton, more neutral in other words.
Thick Felt (Black)
The bass sounds somewhat close to the medium felt; however, its accurate and very well controlled. the best bass so far in the test. The vocals are more detailed and the soundstage has improved overall. Also, compared to the other materials so far, the sound here sounds the most forward, sounds great when playing rock.
Aluminum Foil:
Holy crap! A whole world of difference! Firstly, the highs have improved dramatically; much more detailed and forward but overall very very very balance. when playing rock, this was the most enjoyable of all the materials because of it's forwardness. seems like it gets you up and close to the singer. On a particular mention: around 3:40 of Gypsy, all of the other materials sound like the main solo guitar is slightly far away where the aluminum foil sound like its right in front of you, very forward like I was saying. Crystal clarity without losing focus on the bass and
mid-range....overall, the highs are extremely enjoyable.
Secondly, the bass's accuracy has improved significantly, much more controlled without any distortion at high volume. When playing Layla, the other materials didn't really didn't really allow the bass to shine whereas the aluminum foil; it was extremely noticeable...also during the vocals of the song, you lose focus on the bass with the other material but with the foil, the bass is even and can be heard/felt throughout the whole song.
Significant improvement; especially one of my goals for modding was to get better highs and clarity because I felt the stock was way too muddy and distorted. Definitely made the HD238 more fun to listen to.
Aluminum Foil Throughout The Whole Cup:
Hmm...this one is interesting. first of all, it's quite bright .... good and bad, good because the highs are better in detail compared to the first aluminum foil. when focusing on certain instruments, this setup really shines. And it
actually sounds much more forward than the first aluminum setup. But bad because it can become too bright and it develops harshness. Overall I would say that the aluminum 2 is an slight improvement over the aluminum 1 in the highs, simply because of the detail but can be rather harsh.
Secondly, I can't say that despite having better highs that I enjoy this setup; the bass's magnitude has dropped tremendously, in essence, the bass is hardly impactful even compared to stock. This definitely kills the fun whenlistening to rock or bassy music.
Thirdly, where has the mid-range gone?
Overall, this setup is too bright....you know, it kind of sounds like my k701 even the detail is similar....well slightly, k701 still has better detail and sound more balanced.
Aluminum Foil Throughout The Whole Cup With All 3 Types of Felt:
The intention with this one was to attempt to improve the bass while keeping the brightness. It worked but the bass still wasn't close enough to the detail and power of the first aluminum setup. Still a little too bright, I decide I won't bother with the
aluminum foil throughout the whole cup anymore.
So finally, this makes me think about how I can approach my goal which is to get the most out of the highs while improving the bass to make it more balanced and controlled. I determined that I should use the first setup of the aluminum foil to achieve the great highs and balanced bass. In addition to that, I should use the felts to smooth out the bass and make it more accurate. Another advantage to using the felt is that the mid-range and soundstage will improve as the individual felt tests show.
Anyways, this's the best sounding setup I found: in order of placement in the cup:
1) Aluminum Foil (cup size only)
2) Thick Felt (Black)
3) Medium Felt (Yellow)
4) Soft Felt (Blue)
In comparison to stock, this is a tremendous improvement. The whole range has become more accurate and detailed. The bass is impactful and shows smoothness and balance and the highs demonstrate great detail and sharpness in vocals and in instruments. The soundstage/forwardness makes the listening experience more enjoyable. Overall, I am extremely impressed with how this turned out.
Next time, HD238 recabling.
