What frequency???

before you mess with EQ, mess with the room! try moving the cab to a different spot, or hanging curtains, or something else to change the actual acoustics in there.

a room cancellation won't be fixed by EQ no matter how much you boost it, those frequencies are just at the right length to cancel each other in that spot; in fact, the more you boost that "dead spot" with EQ the worse it will sound.

that's why RTAs are mostly no good for telling you how to EQ a room.

 

Walter is all over it. Try moving the cab around. Try different distances from the wall/corner. Try decoupling it from the floor (maybe set it on some foam or a couch cushion or something to see if it helps). But you probably won't EQ away that kind of problem.

 

Keep them stacked, and as close to a wall as you can. That way, the higher frequencies that you don't worry about so much will get cancelled and not low freqs that you need.

 

A couple of other things to consider. Tuning your E string to C, may be the primary cause IMO. The string and relation to your bass might not be producing much of anything in that range. It's not that the E, F etc aren't there, but the string that loose, might just be dead. Try listening to the bass unplugged, or better still, unplugged with your ear up against the bass body. What are you hearing now? On the other hand, if you do need to know, look here for frequencies. (http://www.contrabass.com/pages/frequency.html ) I will say I agree with the others, boosting those frequencies will most likely cause you more headaches.

 

like jimmy said, splitting up bass cabs is bad, but more to the point, why do you need two 4x10s for practice? you shouldn't be nearly that loud.

practicing at those levels just covers everything up so you don't notice the mistakes and weak spots, which the whole purpose of band practice is to find and fix.

 

Back in high school we used to practice in an empty warehouse with a corrugated steel roof. It echoed like no tomorrow and we thought we sounded so cool...

 

"Sweep" the center frequency on your parametric back & forth with a moderate bandwidth & a good amount of boost or cut. You'll find your frequency of interest in a few seconds. Once you've found it, tweak the bandwidth & boost/cut to "equalize" with the other frequencies.

Using boost to find a band that needs cutting, & vice versa, can help quickly find a band that isn't right by magnifying what's wrong. For instance, if you know there's too much of "something" boost a band & sweep the center frequency until you find noticeably more of that "something", then cut until it goes away.

 

In a small enough listenimg area ( small room ), boundry distances are vlose enough to where keeping all your lowend single-sourced isn't always the answer. The boundary's are close enough there will still be dead spots. In cases like that, sometimes splitting up/scattering yojr low frequency sources can help.

Unfortunately, there really no fixed methodology for this...whatever sounds best, works best.

The idea being, these closely spaced low frequency sources are undoubtedly going ro produce peaks and nulls. The idea being, when the listener moves into one subs weak spot, they are moving into another subs strong spot, thus still hearing even bass.

It wotks, but placement varies for every room you're in. So, your setup will vary as such.

 

+1

this is a good parametric trick; if something seems kind of annoying, boost a band hard, then sweep it through until you find the spot where it's really annoying (or even feeds back), then cut at that spot.

i don't know that the reverse is true though, cuts are always harder to pick out.

 

The "move the cab around" people are probably right but since no one has answered your question, I will. The 4th and 5th frets on a string tuned to C will be E and F, so the frequencies will be about 41.2 Hz and 43.7 Hz. So I'd fiddle around with 40 to 44 Hz on the EQ. It may not do you any good, so move the cab around.

 

Or 1 or more harmonics (multiples) of those frequencies (80 Hz, 160 Hz, 315 Hz, etc. A lot of times you don't actually hear much of those lower frequencies at all & your brain "interprets" them for you based on what you're actually hearing.