"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Carlos,

It's large but squareish (4.6 x 5.5 x 2.5 m)

As far as room acoustics is concerned that's a small room, and so it suffers
from the same problems of skewed low frequency response that are common to
all small rooms.

Well, I didn't make myself clear: it's largER than the one I had
before, where I didn't have problems like this. I know, I was just
lucky then.

there's always a big valley at the listening position, so I think the best
solution is the sub.

A big dip in the bass range in a room that size is ALWAYS caused by acoutic
interference due to reflections off the walls, floor, and ceiling.

Of course. That's exactly what LspCAD models and, from the looks of
it, quite accurately. But those reflections depend also on where the
loudspeaker is and where the listening position is, so a possible
solution is to move the source of the frequency band that gives
problems to a different location, provided you can't locate spatially
sounds in that band. I have made experiments in the past and, below
100 Hz, I can't.

It might
be fun to build a sub, but it's the wrong approach. (Unless your main
loudspeakers really are deficient in the bass range.) Not only will a
subwoofer not solve the real problem, it will likely make things even worse.
However, it will give you more "thump and boom" if that's all you care
about.

Well, my main speakers are actually really good in the bass range, but
their bass range gets seriously screwed up by the room acoustics below
100 Hz, and, as I said, I can't move them and/or the listening
position around to improve that; however, the subwoofer, placed in a
certain spot, results in a very flat response (no "thump and boom")
below 100 Hz at the current listening position, so if I design and
build it properly, which I know how to do, and also design and build
properly a crossover that removes the problem band from the main
speakers and feeds it to the sub, which I also know how to do, I will
solve the problem.

I'm not saying other approaches, like changing the room acoustics,
won't work (though I doubt a very deep valley in the frequency
response like the one I have can be solved without very seriously and
disruptively altering the room), I'm just saying there's no reason why
the sub must be "the wrong approach" and "make things worse".

Just to clarify: I'm not adding a boom-box to my system to get more
"thump". I'm adding a very fine Scan-Speak 25W/8565 bass driver in a
closed box with maximally flat alignment adequately crossed over
(Active 4th-order Linkwitz-Riley) to the main speakers and with its
location carefully chosen to have the flattest possible FR. Frankly I
don't see what could be wrong with that.

Carlos