When I was looking to buy these speakers awhile ago, I looked through a lot of threads without any good comparisons between the two. People simply recommended whatever they owned, without necessarily owning both for some period of time. I'm not going to do a very deep comparison, just a quick one.
I'm not going to go too deep into the sound but if I were to describe the BX5a, they sound more like grados and the A5 sounds more like my UM3x (except soundstage) in how the bass, smooth midrange and treble is presented. Keep in mind the BX5a is a monitor and the A5 is not, hence the frequency response is quite different . Note that I have the BX5a non-deluxe and the deluxe supposedly improves the bass and treble in some way.
First I'm going to compare the bass. This is instantly noticeable between the two. The A5 hands down has more bass, and I can see why someone would be fine without a subwoofer. The BX5a's bass is very light and I definitely recommend a subwoofer to pair with it. From 150hz-60hz, the A5 just has more impact and quantity that the BX5a cannot touch.
Soundstage: The A5 has a tad more depth, but the width is about the same as the BX5a. Nobody will really be missing much soundstage wise when choosing between the two, the difference here is very small.
Midrange/Treble: The A5 presents voices in a more realistic manner with weight where the BX5a sounds light. The A5 is very nice with vocals, very smooth and sibilance free. A5 is never harsh on my ears, for the BX5a it really depends if the recording was horrible or great. The BX5a sounds better with guitars, sounds more exciting and lively. Drums sound more snappy on the BX5a. I find the A5 more forgiving on lower bitrate files, where the BX5a can become edgy or sound a tad harsh but I believe it's simply because the BX5a is more revealing. High quality bitrate files sound excellent on both speaker sets of course. The A5 in general sounds more laid back compared to the BX5a. The tweeter on the BX5a is noticeably more detailed, and has more sparkle. Each time I switch from A5 to BX5a, everything just sounds more transparent and crisp, the only thing missing is the bass and sometimes notes sound light and body-less (almost sounds the same as me switching from my UM3X straight to Grados, so for those who have heard both of these headphones will know what I'm talking about). A5 sounds mellow in comparison while BX5a is more analytical. The BX5a is on the border of being shrill at times where the A5 never does. I didn't really hear anything in the mids on BX5a, that I didn't hear with the A5 but the BX5a makes it more noticeable in the way its presented forwardly. Instrument separation on both are quite equal, both do well.
Conclusion: I think both speaker sets are great, and are quite competitive with one another. It really depends what sort of sound signature interests the buyer. The A5 is probably less fatiguing listening to for a long period of time though I have no problems with the BX5a. I'll be keeping both around for awhile, relieved I wasn't disappointed with the A5 . A5 focuses on bass, BX5a focuses on treble would be the way to sum things up.
The BX5a really needs a subwoofer, can't stress this enough. I'm still going to be using a subwoofer with the A5 however, but not absolutely necessary.
I would gladly answer any questions. By the way does anyone know what would be the next step up from these speakers?
Added November 13th,2010.
I also want to note that if I were to put the sound signature of these speakers with a comparable headphone now that I've heard more headphones, it would be
BX5a = K701
A5 = HD650
Edited by kite7 - 11/13/10 at 3:17pm