Comparison of MHDT Stockholm 2 DAC to Schiit Bifrost Multibit, Sennheiser HDVD800, and FiiO X3 with HiFiMAN HE1000, Sennheiser HD 800, and Grado PS1000 Headphones
This is my report on the one-week visit of the MHDT Stockholm 2 visit to my home. It was a great house guest, not leaving dirty dishes or unmade beds behind, it always picked up its dirty socks and underwear, and I thank
@Soundsgoodtome and others on this tour for making this possible
SUMMARY
I used three distinct signal chains (i.e., amp and headphone), for which the amp was provided by the headphone manufacturer as being presumably ideal for the headphone. For each chain, I compared the sound quality across 10 acoustic features with and without the Stockholm 2, using an alternative DAC in those cases. Here is what I found:
- Stockholm significantly improves quality through the HiFiMAN system as compared to the Schiit Bifrost Multibit Uber (Stockholm is faster and provides a better soundstage)
- Stockholm does NOT improve quality through the Sennheiser chain (in fact, Sennheiser chain with Sennheiser DAC sounds essentially the same, but has a larger soundstage)
- Stockholm does NOT significantly improve quality through the Grado chain (again, it sounds essentially the same, but it does improve the soundstage over that of the pure Grado chain).
One possible explanation of the clear improvement on the HiFiMAN chain and not the others is that the HiFiMAN chain was more discriminating. Separate tests performed using these methods on each of the three headphone chains (without the Stockholm 2) had ranked the HiFiMAN chain the highest, the Sennheiser chain next, and the Grado chain last. Perhaps only the HiFiMAN chain could discriminate the subtle effects of the Stockholm 2 DAC.
MY BACKGROUND
Since we were asked to provide our background to qualify for the tour, I am reiterating it here (and to provide more weight to what otherwise might be a fluffy review!)
It is with great humility and excitement that I applied to be a stop in the tour, and I promised that I would use the same 10-feature acoustic comparison for three-way rankings of components that I detail below. I promised to write a review in which I will spell nearly all the words correctly (though the MHDT website tells you that a color option is "sliver!")
I have the Schiit Bifrost Uber USB2 with Multibit upgrade, the Sennheiser HDVD800 DAC/amp (with means to bypass the output of the HDVD800 DAC with the Stockholm2 and go into the Sennehiser amp) and any number of portable DACs (VAMP VERZA, Sony PHA-1, CEntrance HiFiM8, and Beyerdynamic A p 200) to use as comparison, plus many of the best headphones (Sennheiser HD800, HiFiMAN HE1000, Grado PS1000, Ultrasone Ruthenium Edition 8) and nearly every Grado known to man or beast (PS1000, HP1000/HP1, GS1000, Bushmills X, GH-1, PS500, HF-1, RS1, RS1i, RS2i, RS2e, SR325e, SR3225is, SR325i, SR325, SR225i, SR125e, SR125, SR80e, SR80, SR60i, GR10e, iGrado).
I am a wannabe of the music industry. Though I have been playing and performing classical piano for 53 years, I am 6 months into learning jazz piano. However, I have worked with acoustics since joining Bell Laboratories in 1978, first working in the computer recognition and synthesis of speech, and then more generally in the underlying area of signal processing. I published a textbook in real time signal processing (its cover is my avatar), which peaked on amazon.com at Number One Million Two Hundred Thousand at the height of its popularity in about 1992 (i.e., over a million books sold more copies!)
TEST CONFIGURATION
My intent was to assess the effect of using the Stockholm 2 by comparing the sound, with the Stockholm 2 and with another DAC, through three top-of-the-line headphones, each powered by its companion amplifier bought from the same manufacturer as the headphone. The idea was that the manufacturer's own amp would be most carefully designed to maximize the quality of the headphone sound. In all cases, I used a FiiO X3 digital music player, outputting digital music at CD data rates, via its S/PDIF coaxial port. No use of USB was made in any of these tests. I used the AEG 5670 tube in the Stockholm 2 for all tests.
My three amp/headphone combinations were:
1) FiiO X3 S/PDIF digital out to (Schiit BiFrost Uber Multibit with USB 2 DAC, aka "Bimby" in other reviews here OR Stockholm 2 DAC) to HiFiMAN EF-6 amp to HiFiMAN HE1000 headphones;
2) FiiO X3 S/PDIF digital out to (Sennheiser HDVD800 DAC OR Stockholm 2 DAC) to Sennheiser HDVD800 amp (within the same box) to Sennheiser HD 800 headphones;
3) ( FiiO X3 DAC Line Out OR FiiO X3 S/PDIF digital out to Stockholm 2 DAC) to Joseph Grado HPA-1 amp to Grado PS1000 headphones.
Chain #1 - HiFiMAN EF-6 & HE1000 headphones driven by either Schiit Bifrost or MHDT Stockholm
Chain #2: Sennheiser HDVD 800 amp & HD 800 headphones driven by either HDVD 800 DAC or Stockholm 2
Chain #3: Joseph Grado HPA1 amp & PS1000 headphones, driven by FiiO X3 Line Out or Stockholm 2
TEST METHOD
I adapted the three-headphone comparison method that I have applied so far to over 50 headphones to make it suited for comparison of two choices (i.e., with or without Stockholm 2).
I used four songs, all encoded in Apple Lossless Format at CD quality (I actually bought the CDs and ripped them... no internet download involved) and played by my FiiO X3 digital audio player.
- "You're Going To Miss Me When I'm Gone," by Band of Heathens, from their album One Foot In The Ether (used for fidelity of drum sound, positional resolution of two vocalists, and ability to discern pitch of string bass passages);
- "Spanish Harlem," by Rebecca Pidgeon, on The Ultimate Demonstration Disc of Chesky records (used to assess female vocals, transparency, the attack of finger on bass string, and high resolution discrimination of differences in shaker shakes);
- "Symphony No. 3 in C Minor Op. 78 (Organ Symphony) - IV" by Camille Saint Saens played by Lorin Maazel and the Pittsburgh Symphony Orchestra (used to assess the "ripping" sound of well-rendered lower brass and organ reed pipes, and the ability to hear a very small entrance amidst a bombastic chord of orchestra and organ at full tilt);
- "Throwback" by B.o.B. on Underground Luxury (used to assess ability of a bass tone, specifically lowest C on piano at about 32 Hz, to pick me up by the throat and shake me!)
The 10 tests were as follows:
- Transparency: What is between me and the music? A felt cloth? A "Sennheiser veil?" A frosted window? Dirty window? Clear Saran wrap? or nothing? At its best, makes me forget I am listening on headphones and am in room with musicians. [I use the 12-second segment 0:00 - 0:12 of "You're Going To Miss Me," which is kick drum, guitar, piano, and cymbal for this test]
- Width of sound stage: How far to the left and to the right, (yes, AND up and down in best cases) does it seem the musical sources are arranged? [I use the same 0:00 - 0:12 segment of "You're Going To Miss Me," which starts with kick drum center, guitar #1 right of center piano far right, guitar #2 far left, to see 1) to what extent am I among rather than in front of the musicians, and 2) how wide an angle do those positional extremes of instruments form?]
- Positional resolution: Can I distinguish a difference in position of two singers in Song 1? [I use 0:30 to 0:38 of "You're Going To Miss Me," where one vocalist ends a verse and a second vocalist, standing next to him, takes up the next.]
- Bass visceral: Does the bass in third verse of Song 4 actually shake me? Or do I just hear it? [This test uses 0:31 through 0:33 of "Throwback, " where the bass drops to the lowest C on the piano.]
- Drum "twang": At start of Song 1, do the bass and tom tom drumhead have a tone and a pitch, rather than just a thump? ["You're Going to Miss Me" 0:00 - 0:12]
- Bass pitch perception: For the complicated bass runs in Song 1, do I hear a pitch with sufficient accuracy to sing or transcribe the part? ["You're Going to Miss Me," 1:02 - 1:23 to see if I can hear the pitch of not only the bass glides and accented notes, but also the grace notes]
- Bass finger pluck: Do I hear the actual impact of fingers on the bass string just before hearing its sound on Song 2? ["Spanish Harlem," 0:00 - 0:04, listening most carefully to the repeated 3-note pattern to see if I not only hear an initial attack but some structure immediately following, before the finger leaves the string and the sound just rings)
- Shaker variation: In Song 2, verse 3, do the various shaker shakes sound a bit different from each other, as they should? ["Spanish Harlem," 1:40 - 1:47: there are clearly loud and soft shakes, but how many more volume levels of shakes can I distinguish, and can I hear structure within each shake as the seeds hit the shaker wall?]
- "Ripping" of organ / brass: In Song 3, is there the sensation of hearing each vibration of the French horn and low organ reed tones (sort of the tonal counterpart to hearing a "pitch" from a drumhead in Test 5); ["Organ Symphony," initial chord from 0:00 - 0:04 and French horn passage 0:06 - 0:12]
- Discern added chord: About 1:38 into Song 3, after the full orchestra and organ hold a chord at the top of a passage, can I hear a small number of orchestra instruments join in, as sort of an echo, in the second measure of that chord? ["Organ Symphony," in the passage starting at 1:08, how well can I hear the small additional chord added at 1:16 on top of the full strength organ/orchestra chord in progress? Clearly enough to have noticed it if I weren't already listening for it?]
These tests generally emphasize what I find most pleasing in a headphone, namely high-frequency-related features including transparency, upper harmonics of sounds from drum-head, brass, organ pipe, and string bass, and high-resolution effects such as fine detail of each shaker sound and the finger on the bass string.
For each of the three headphone chains above, I compared each of the 10 tests by comparing the case of "with Stockholm 2" to "without Stockholm 2" (using the alternative DAC as described above). If I did not hear enough of a difference that though I could hear it in a blind test, I rated the two cases as a tie.
TEST RESULTS
In the tables below, the combination (i.e. without vs. with Stockholm 2) that sounded the better for each of the 10 tests is given a score of 3 and colored blue, with the poorer combination being scored at 1 and colored red. In many cases, no change in sound of a particular of the 10 acoustic tests was noted... these ties were scored at 2 points each and colored purple.
HiFiMAN Chain
The Stockholm DAC provided a wider soundstage, better pitch perception of subbass, and more of the high-harmonic "ripping" sound of organ reed stops and French horns, than did the Schiit Bifrost. The Bifrost provided more of the high-frequency content that gives a bass (kick) drum a "twang" that keeps it from being simply a "thud." Though it does not show up in the table, the Schitt Bifrost put the instruments that were in the center of the soundstage closer to the listener than did the Stockholm 2. As a result, the Stockholm 2 seemed to provide a concave sound surface, with instruments arranged on a semicircle around the listener, while the Bifrost pushed the center musicians closer to the listener, resulting in a "U" shaped sound stage bulging in toward the listener at the center.
Sennheiser Chain
For the Sennheiser HD 800, the sound was almost identical whether using the Sennheiser HDVD 800 as the DAC or using the Stockholm 2 as the DAC. The only difference was that soundstage actually decreased a bit by using the Stockholm. Hence, all tests above except soundstage are tied, with two points each. I was surprised by this conclusion, as folks have complained that the DAC that was chosen for the Sennheiser HDVD 800 DAC/amp is of only modest quality, while the amp is excellent with the HD 800 headphone. For example, the price of the HDVD 800 is $400 than that of the HDVA 600, which has the amp but not the DAC. Folks have said that the Sennheiser DAC sounds about like a (modest0 $400 DAC, so it is surprising that the Stockholm DAC did not improve sound more significantly. Perhaps the Sennheiser DAC is particularly well paired with the amp in the HDVD 800.
Grado Chain
As with the Sennheiser chain, the Grado chain does not highlight major differences between the Stockholm 2 and the other DAC used, which was the DAC of the FiiO X3 digital music player that was captured by using its Line Out. In this case the Stockholm 2 improved the soundstage, which in retrospect may be expected, since most Grados are not known for large soundstage. As with the HiFiMAN chain, the Stockholm 2 pushed the middle instruments out from the listener, resulting in a more circular, less inward-bending U shaped soundstage. Though not shown in the scores, the Stockholm 2 also rendered the female vocalist, Rebecca Pidgeon, less "hooty" in the test tune "Spanish Harlem."
CONCLUSIONS
I believe that the ability of each chain to benefit from the Stockholm 2 may be in proportion to the overall sound quality of each chain. In a test several months ago, I had used this test method to compare the HiFiMAN EF-6 to HE1000, Sennheiser HDVD 800 To HD 800, and Grado HPA1 to PS1000. Here are the tabular results:
The HE1000 scored significantly above the HD 800 and PS1000, which in turn were rather similar. It may be that the extra discrimination power of the EF-6 / HE1000 is needed to benefit from the capability of the Stockholm 2. However, it could just be that the particular nature of the HiFiMAN chain has aspects that are helped more by the Stockholm 2 DAC.