Look:
1) you may have a 600w handling cabinet and a 200w handling cabinet; as long as you do not exceed the max handling rating of each one you're just fine. Take it as two glasses: one is capable of 0,5 litres and the other is capable of 1 litre; you will not try to put 0,8 litres of liquid in the 0,5 glass, obviously, otherwise you will spill it out (translated: you will blow the cab). But both cabs will serve you good if you apply power within the specs. Mind you: it is not smart buying a 1000 w handling cab and use it with a 100w head (now stressing the concept, obviously) but you are absolute safe. Normally the cab power holds the head power. Different philosopies: somebody prefer to stay on the safe side, therefoe the cab power slightly bigger than the head; somebody thinks 180 degrees, because in this way if you don't "strangle" the head (undistorted power) you will have more clean power but be careful not to blow the speakers. Others swear about equal power. Go figure.
2) the main factor in general is the efficiency: if a cab is 3 dB more efficient than the other, this means that it will produce the same amount of sound pressure to your ear than the other cab but with half the power applied. (On one you will rotate the volume knob to deliver, say, 10w while on the other cab you need 20w to have the same sound level). End result: if you have an external speaker that is more efficient than the one in the combo (in general) you will "feel" that the only speaker that is actually working (generating sound) is the external one and you will end up with something not balanced (or viceversa). On the other hand I can imagine that if Markbass Marco De Virgiliis self says that the 604 is "the ideal companion..." he knows what he's talking about
: very possibly they gigged with the Traveler plus the 604 and therefore saw that together they are a very good couple. (Checked on the site: both have 8 ohm impedence and the Minimark cab has 101 dB spl while the NY 604 has 100; so they should work ok anyway...)
3) about the cab to be paired, it is a common, reknown and well accepted thing on TB that if you get a "matching" cab (read "perfectly equal to the one of the combo" as for manufacturer, efficiency, speaker-s and volume) you will have the best possible, undistorted sound option. Otherwise (mixing a 2x6 with 1x10 or 1x12 etc.) you might end up in some disastrous phase cancellation effects that are generated when the speakers are not equal. In addition, you MUST stack the cab one on top of the other (you might be fined!), to avoid extremely bad, unfair and terrible horizontal dispersion effects. If you want to dig deeper on the subject and trigger a headache by yourself, please feel free:
Pairing cabs
Said the above, the points 1) and 2) are sacred; but personally point 3) for me only is... a bunch of crap! But I just say once, because the matching cab police is already after me and now I just have to run for my life...
P.S.: Sorry I forgot that! You are very welcome
V.
