Budget Strategies forTightening up Bass?

"The most important thing in a system is the room and speaker placement."

Also match between amp and speakers.

The rest may help but cannot substitute for getting these two things both right first.

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I don't post here much because of the large variety of opinions, all of which cannot be right. But this one is so obvious to anyone who has successfully voiced large numbers of systems.

The single most important thing does have everything to with the room. It's locating the best place for the listening seat.

The "best place" is where the bass is smoothest, so that you are not unduly at the mercy of room resonances. All else (such as moving the speakers, changing amps, etc) is of lesser significance. Not that they aren't important, but working with the standing waves in the room - rather than against them - is foundational to the OP's quest.
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I'm not familiar with the Silverline 17.5. If it uses a ported box, you might try lowering the tuning frequency by lengthening the port and/or reducing its cross-sectional area. Or tightly stuff open-cell foam into it, transforming the system into a pressure-relief type of cabinet. Or seal the port entirely.

Duke
dealer/manufacturer

OK... I did move the speakers; I didn't have alot of room to play with, but now, at a distance of 30" from the wall, rather than 10", the bass is much more defined. In fact, it sounds pretty darned good on well-recorded cds. The sounds-stage is deeper and imaging is better. Could it be better? Probably, but I don't have the luxury of a dedicated listening room. I contacted silverline and Alan Yun asserted the speakers are "desiged to be ported" and that plugging the ports "could damage the woofers". Perhaps this is his standard fine-print disclaimer and does not so much represent an actual risk, but even so, I'm not inclined to start stuffing anything into the 17.5's. For me, they were an expensive purchase. I'm still going to try what others have suggested, in addition to speaker placement.I don't think it has to be a black and white, "this" or "that" approach.

Plugging the ports will reduce the excursion-limited power handling above and around the tuning frequency, and increase it below (where it falls rapidly with a vented design). You're not pushing them with a big amp to begin with so I think you would be fine. However re-positioning speakers and/or listening position is the preferred approach; I had been under the impression that wasn't feasible in your situation, and am glad that you were able to try it.

Duke