To start any discussion about how to deal with resonance, we need to know which ones are the problem. A speaker driver has a free air resonance. It also has diaphragm resonances. In a small closed box, those factors can also change.
The easiest way to eliminate box resonances, is to eliminate the box OR make it so big or so small that the desired pass band is not affected. If the problem is the diaphragm or motor, nothing that you do to the box can fix that.
That all being said, I know of no real "no bullshit" study on the effect of back chamber resonance on sound. I know of a lot of audiophile BS about what they think that they hear, or by inaccurate measuring they extrapolate bad sonics.
What Romy mentioned with "half of the drivers energy" really has NOTHING to do with the resonance per say. It is merely saying: make the enclosure solid and inert. That would only prevent IT from vibrating, but not change the effects of internal box resonance going back through the driver and distorting the front wave.
So, to discuss resonance intelligently, we need to know what you hear, what you measured and how loudly you must be playing for enough energy at 600Hz to vibrate a box attached to a horn. I mean 200 Hz I could understand, but 600? If you are playing extremely loudly, the question is if that resonance is even coming from the driver/box.
Whenever I feel blue, I start breathing again.
Being a musician, I deal with constructive resonance every day. Tubes resonate as a function of length, boxes resonate as a function of the internal length, width, diagonals. Irregular shapes resonate as a function of volume, horns resonate as a function of taper and length.