Some of your problem may be system related ( sonic combo of electronics ), but your speakers have very definite problems internally. Changing cabling and electronics may help to reduce how obvious this is, but short of re-designing or getting rid of the speakers, you're always going to have to deal with this type of situation to one extent or another. Been there, done that and you can read my comments about it in the archives.
Probably the easiest thing to do would be to seal the ports as best possible and fill the cabinet up internally with either polyester fiberfil, acousta-stuf, acoustic foam or fiberglass. Changing the quantity and density will vary the bass transient response and extension to your liking.
It may initially sound like the speakers have "no bass" to you after doing this, but that's because you are used to hearing a massive amount of bloated ringing. Careful listening should instantly tell you that bass definition is improved and that bass notes actually do have "pitch". After a while, the drivers will start to produce more bass as they break-in further.
I know that others will say that this is "impossible" if the speakers already have many hours on them, but guess again. Due to the vented alignment, the woofers never really moved much. As such, their suspension was never pushed very hard. Sealing the cabinet causes greater excursion of the driver, which will alter the suspension as compared to what it was prior to sealing and stuffing the cabinet. Once this takes place, and you get acclimated to what more accurate bass actually sounds like, i think that you'll be pretty happy with the results.
The reason why sealing this cabinet works better is that most of the bass extension that the ported Legacy speakers enjoy comes from producing a huge peak in the upper bass region. By the time the output has fallen to the -3 dB point coming off of that huge peak, the measured frequency is quite low. While this looks good on paper in terms of printed measurements, it sounds like hell.
The main problem is that the huge peak is based on a complete lack of control, no damping and the sound reflects that. That is, it is very slow, indistinct and rings uncontrollably. There is a GREAT quantity, but the quality is phenomenally low. As i've said in the past, sealed vs ports is a matter of quality vs quantity.
By flattening the peak via killing the ports, and sealing and stuffing the cabinet, which makes the box appear physically larger and restores internal damping characteristics to the drivers, not only is sound improved, but so is extension. That's because vents fall off at a much sharper rate below resonance than sealed cabinets do.
If you have questions on this, feel free to either drop me a line or post your questions here. I would prefer to do things publicly if at all possible though, as others can share & learn at the same time. Sean
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