My subwoofer seems to be missing some frequencies

So I've noticed since I've moved my room around that my sub woofer doesn't seem to be putting out bass at an even distribution, and i'm guessing that it's somewhere around the 50-35hz mark.

Any ideas on why?

It's probably standing waves or some other kind of interference. Try moving it to another position and see if ti helps. A good way to figure out the best subwoofer placement is to put the subwoofer in the listening position and then walk around the room until you find the spot which sounds best, then put the subwoofer there.

Ditto what Dexter Kane said. Just because you can put a sub just about anywhere and still hear it, doesn't mean it sounds good anywhere. 

Thanks! It more or less is in a reasonably good position (it's under a desk with a hollow out, so it naturally amplifies the bass) but it;s almost like some of the frequencies are getting lost in the room, like they are hearable, but not from the general listening position, more like in some random corners and behind things.

There also isn't a main listening position as the system is used for parties mainly.

Yeah, that sounds like standing waves. Subwoofers really shouldn't be put in positions like that, they need to have a good distance from walls and other surfaces as it causes distortion. It's called the boundary effect. The distance from surfaces depends on the size and power of the subwoofer but atleast 1 or 2 feet would be a good start.

Is that the entire subwoofer? Or just the direction of the hole?

Some frequencies are boosted in subwoofers due to the ported and tuned design. If such a frequency coincides with the resonant frequency of a body affected by the transversal waves emitted by the subwoofer, this causes that body to emit these same frequencies "out of phase" with the emissions of the subwoofer, which cancels those frequencies out.

You need to reposition your subwoofer, that's all.

Best is not near a corner or close to a wall. Free standing (at least 1-2 m from large solid bodies) usually gives the best results.

Something that might also help is to rotate the subwoofer. Down firing subwoofers usually suffer less from out-of-phase resonance than side or front-firing subwoofers.

Another thing to mind is that the port fires the out-of-phase signal of the cone. If the air volume affected by the cone become coupled to the air volume affected by the port, both will cancel each other out.

Sounds like someone needs to do a old fashion sub crawl! temporarily Place the sub near the primary sitting position, play something with bass tones (test CD would be best), Crawl around the room (yeah you might look a little crazy) until the bass sounds even between frequencies. Once you find that spot place the sub there. Done... You just found the optimum spot for your sub

Haha I decided to give up in the end because it's in my bedroom and there isn't anywhere else it could go. Plus it's mainly for parties, so there wouldn't be any seating position :/ Well hopefully not, otherwise that'd be a pretty lame party hahaha.

If you can change your crossover on your sub and experiment with the same clip and songs to see what works. Crossovers are normally a nob on the back normally 80hz is where you want it for normal woofers some can get down to 40hz but those are kinda rare.

If you have a Home theater in a box you may not have the knob. You may be able to find it in the receiver GUI under speaker setting if not you may be not able to change it.

I wish, It's the Logitech Z906 system I believe and i'm pretty sure the crossover is somewhere around 150-200Hz because that's the only place bass frequencies are coming from because the sattelite's are doing highs and mids and they're only like 5 inch haha.

What is your Receiver and Sub?

It's the Logitech Z906 all in one thing (sorry bout the late reply, blew a fuse haha)

http://reviews.logitech.com/7061/7929/logitech-speaker-system-z906-reviews/reviews.htm?sort=reviewTextLength

The second review shows how to change the crossover.

As long as you have a sound card that supports it

If you ever  what to upgrade I have a Pioneer system I am willing to part with.

:O

Is that really possible? How can the unrelated sound card etc actually control Logitech's own mini receiver?

Looks like it is in the multi channel settings

Hmm interesting, i almost don't believe it, but maybe it is with the right sound card and a direct input because right now I have quite a confusing setup.. S the setup is:

 

PC> 4 Screens, 3 of which are my desktop ones, and the other one is the TV, and for the TV I have a 5m HDMI cable going to it and then an optical cable from the TV to the Logitech system. Now that's the first problem isn't it? I need a direct cable from an (external sound card with a decent driver and software packaged with it??) to be able to control the frequencies properly?

 

If you are quite good with audio then I have a few more challenging questions if your up for it? :)