Both the K500 and the K501 share a very similar sound. They both have a fairly natural sound with a great frequency balance. Between the two, there are some fundamental differences. First, the K500 has less bass than the K501. Even with the K601 pads, which brings helps with the bass, the K500’s bass quantity still lacks behind the K501. It’s a shame, really, because I find the K500 to be better in other areas, but the bass deficiency makes it a hard headphone to live with. And I’m not looking for a bass monster either. None of my cans are bass heavy, but it’s hard for me to be satisfied with the K500’s bass amount.
In addition to the difference in bass quantity, the K501 also has more midrange body than the K500. Which again, makes the K501 a more musical headphone than the K500 is. I find that not only does the K501 has more midrange body, but it has a smoother midrange as well.
The difference in bass and midrange doesn’t make the K501 superior from the K500, and if the previous two paragraphs seems to lean in that direction, then I’ve to give the other side of the story. Whilst the K500 may have less bass and midrange body, it makes up with a clearer, more transparent sound than the K501. It does seem like a general rule of thumb, that thinner sounding headphones tend to sound clearer and more transparent, and that added midrange and low end body tends to obstruct clarity. There may be exceptions to this rule, but I’ve seen this phenomenon quite often that I may think it’s simply laws of physics being at work: Etymotics’ ER4S and ER4P, Grado’s SR60 and SR60i, and Alessandro’s MS1 and MS1i. The ER4P, the SR60i, and the MS1i, have more midrange and low end body than their counterparts, and at the same time, they have less clarity than their counterparts. Specifically, the trade off happens exactly at the midrange and the low end, the K501 seems to have less control and clarity than the K500 at those frequency range. But again, overall, both headphones fall more to the transparent category, than they are diffused or muffled.
So, we can’t say that the K501 is superior than the K500, simply because with the gain also come a trade off. While more people, me included, would be happier with the K501, some others, depending on the music and listening habits, may still prefer the K500.
One of most noticeable signature of the K500/K501 is its humongous soundstage. Truly, for the prices that they sell for (back when they’re brand new, or even today’s higher selling price), it’s hard to find a headphone with a soundstage that’s bigger than the K500/K501. Of course, they still fall short to the soundstage and the imaging performance of today’s best headphones like the HD800, but we’re talking a totally different price level here. Yet it’s still interesting to see that the K500/K501 has a soundstage that’s bigger than AKG’s own AKG701, though the K701 has a better instrument separation. I really cannot imagine what a great deal the AKG K501 was, when it was still available brand new a few years ago. It was selling for slightly above the $100 mark, but for that price, there is nothing that can come close to the soundstage performance of the K500/K501, even today. The big soundstage is also complimented with a good instrument separation that’s among the best in the $100+ price level. The K500/K501 is probably one of the most ideal Jazz and Classical headphone at that price level.
I do find that the K500 has a bigger soundstage than the K501. The K501 already comes with a big soundstage, but the improvement on the K500, when heard side by side, is quite apparent. Both headphones are fairly equal when it comes to imaging performance. When listening to classical recordings, both headphones are very good in portraying the ambience of an orchestra hall. When listening to accoustic instrumental recordings, both headphones feels very spacious and airy, with enough forwardness in the upper midrange to maintain intimacy.
Seeing how the K500 and the K501 was probably developed in the 90s, and there is no denying that older cans lack the bass and treble extension of more modern designs, and likewise the detail level also can’t match a lot of modern headphones in the similar price range, even portables. They are in no way muffled, and on the other hand, they do sound quite clear, but if you listen carefully, the detail is inferior to the newer headphones. However, no one seems to be bothered by these small “inferiorities”, simply because the sound signature of the K500/K501 is very pleasing to the ears.
I personally like the stock pads on the K500/K501. I do find that the K601 pads on both headphones do add bass quantity, but somehow I find the bass addition to be unnatural, and so I still prefer the sound of the stock pads. If the K500 are meant to be bass light, then so be it. Let me explain more. On the K501, I find that the bass amount with the stock pads to be just right. When you replace the pads with the K601 pads, the K501 becomes unbelievably boomy, and I really don’t think people have associated the K501 with the word boomy before, but it really does become boomy with the K601 pads. Simply afwul, and it’ll take the stock pads anyday over the K601 pads.
On the K500, the K601 pads does bring up enough bass, without making it boomy like what happened in the K501. But again, I find the bass addition to be unnatural. I do believe that AKG has tuned their driver to work best with the stock pads. Although the K500 with the K601 pads is still not boomy, but I find the low bass to have an unnatural bump that’s unpleasant to hear. If you really have got to have more bass, I’d advice you to trade the K500 to the K501, as you’ll get more bass amount without the unnatural low bass bump.
Unfortunately, if you’re asking how the sound changes with the K701 pads, I can’t answer that question, as I don’t have any K701 pads to try at the moment.
If there is another issue that I have to touch on, is that somewhat there is a noticeable glare phenomenon on the upper midrange of the K501. I’ve heard this problem on two different mint K501s, and so it may be safe to assume that this issue exists on all K501s. It seems that there is a strange reverberation happening somewhere in the housing that is causing this weird glare on the K501. I’ve never heard a problem like this in any other headphone, just like I’ve never heard the plasticky sound that the K701 suffers from other than in the K701. Well, good thing that this problem doesn’t come up all the time, and in fact, it’s quite seldom, but when it does come up, it’s fairly annoying and makes you want to skip to the next track.
The natural sound and the big soundstage of both headphones remains a fairly unique combination that I haven’t found on any other headphone. Especially at the $100+ price level, it’s quite hard to find another full size that plays Jazz and Classical better than the them. I really think that if AKG was to reintroduce the K500/K501s, they’ll be a better hit today than they did, simply because there are more people today looking for a natural sounding headphone than they did back then.
System for auditioning:
Headphones: AKG K500, K501
Source: MacPro via USB to Dr. DAC Prime, CEC TL51XZ
Amplifier: Grace m902, SPL Phonitor, Lisa 3, WooAudio 6, Dr. DAC Prime
Interconnect: Transparent Musiclink Plus XLR, Purist Audio Design Maximus XLR, DIY Copper with Eichman Bullet RCA