it’s something you read a lot on head-fi. the idea is that, say, you have a “bright" headphone and a “warm” amp so there’s “synergy” between the two providing a more balanced sound.
personally, I think it’s an overused and misused term. there’s too much over thinking in the community when people are spending way too much money on sources and amps.
That's what I assumed but wanted to be sure of before I posted.
Honestly, I STRONGLY disagree with the above posters who say synergy does not exist. (Bitmap Frog and to a lesser extent ElyrionX) I am 100% sure I could, blindfolded tell you differences between certain amps and headphones dependant on such synergy. I can say that because I have blind tested with my equipment, and a range of equipment, and found that certain amps, do indeed offer different sound signatures to different headphones.
Whilst there's no exact science to it (since all amps and headphones have unique sound signatures) combining different amps and headphones together does offer up different levels of 'synergy'.
I have several amps and portable amps for example, and do not use the best or most expensive with all of my headphones and earphones. Quite the contrary, I use whatever amp I personally find has the best synergy with it sonically.
For example, portably speaking. I use my ALO Continental with my Beyer T1, as this hybrid tube amp has a warmer tone, that mellows out the highs somewhat, and gives the overall sound more body. This is perfect for the T1, which is by default a bit more hot on the high frequencies, and absolutely adores tube amps. They truly smoothen out the sound somewhat, at least with the one's I've tried. My SR-71A by comparison, is a bit colder sounding and extenuates the highs a bit more than I'd like (can lead to sibilance here and there which I never get with the tube amps), and takes away some of the fullness of the bass. Add to that the soundstage is much smaller.
With my Westone 4's, even though I have 2-3 other top portable amps to choose from, I actually use it most with my JDS cMoyBB. It might not have the clarity or detail of the SR-71B, but it does have a bit more low end bloat, and a slightly wider soundstage, which is preferable to me personally when using the W4's.
The ALO Continental when paired with the W4's, does offer a huge soundstage, but warms the sound a bit too much and removes a bit more of a sparkle from the highs still. I value the middle ground the JDS cMoy offers (with the W4 anyway). Middle of the road detailing, softer (slightly less defined but more prominent) bass and medium high frequency extension (as oppose to SR-71A's more glaring detail, and the Continentals warmer, smoother signature). The soundstage also falls in-between that of the SR-71A and Continental.
Honestly, synergy is a huge deal. It can make a real, tangible and noticeable difference to the balance or marriage of devices such as an amp and headphone. I actually use my T1's with the SR-71A from time to time when I want a more confined, focused, studio esque sound, as oppose to the smoother more open and warm sound the Continental offers.