Please help me tame the bass beast

I agree with Plate. In my mind, you have 3 options:
1) Get a Tact room correction unit. It works exactly as advertised.
2) Try positioning the speakers along the opposite wall they are on now (ie if on short wall now, put them along the long wall).
3) If they are ported, try stuffing the ports with something like dacron, etc
As an aside, I am sure Mr Joseph could help you out as well. Best of luck.

Musicmannj

From your room dimensions it appears as though you might have a standing wave problem. This occurs when 2 dimensions of the room are equally divisible (usually the parallel walls in-front and behind your speakers). Standing waves create bass 'hotspots' where bass frequencies are in phase, and pockets where bass frequencies are out of phase.

If your listening position seats you 'in' or at the high point of in-phase standing wave you hear double the volume of the effected frequency(ies). Conversely if you were to seat yourself at the low point where the standing wave is out of phase you would likely hear very little or nothing.

Your room isn't that large, so its my guess that you're getting a 'sympathetic resonance' from the drywall in your listening environment - a singular bloated bass region. And that THIS is probably a product of an in-phase standing wave.

What height is your ceiling in the room? ...If this too is divisible by the same common number you are unfortunately trying to make music the acoustic environment from hell.

If I'm correct the only practical thing (that I'm aware of - aside from digital room correction) is to calculate the standing wave frequencies, and see if you can eliminate them with bass tubes or other similar absorbers. Another (although less desirable IMHO) is to find the offending frequencies and modify your crossovers to compensate for your room issues. This could be done by the speaker mnfr.

Any one else have a different diagnosis/suggestions...?

Good luck with it,
Mike

I suspect that you have a room resonance problem. To find the approximate frequency at which a room will resonate divide 565 by the room dimension or in your case 565/18 = 31.5Hz and 565/12 = 47Hz. By taking multiples of these fundamentals you get overlapping modes at about 94Hz and again at about 190Hz with several other close modes between these frequencies. This could account for what you are hearing in the mid bass. You can determine if this is the problem by placing a 1/3 octave band equalizer between the preamp and poweramp and notching out frequencies at the overlapping resonances. If you like the results you then know what frequencies you are trying to treat or you could leave the equalizer in place. Just remember that the least equalization is generally the best.

I agree you've probably got too much speaker for the room with your current setup since you can't alleviate the problem with placement(I'm assuming you've tried pulling the speakers out at least 5 feet into the room).

If it were me, my first step would be to plug the ports in varying degrees to see if that helps. After that I'd try some tube traps in the corners. I'd try these two ideas first because they're likely your least costly options and may work.

If that didn't work I'd seriously consider either a)new speakers(maybe trade for the new JA RM33?) or as Plato mentioned get the TacT room correction system. I have absolutely no doubt the TacT will completely alleviate any midbass hump you're experiencing(along with many other frequency and phase anomolies), and it will likely take your system to another level of enjoyment. I've heard what the TacT 2.0 has done for several systems and it is quite simply astonishing.

Personally I'd lean toward the TacT because the RM50s are incredible speakers you probably don't want to part with, but I'd also make sure I had a helpful dealer because optimizing the TacT can be very time consuming/frustrating for the uninitiated. Best of luck.

Tim

If you've tried other equipment exhibiting the same problems then that would point toward setup I believe. Are speakers placed along the long wall as should be, or are you incorrectly firing into the long dimension of the room? However there may be other factors at work; I'm wondering about your cabling? Interconnects, speaker cables, AC cords; many are not neutral & then when they work together the overall results can become even less so. You might already know about these techniques, but I'll briefly review just in case.
My own approach is to go for neutrality regarding interconnects & speaker cables, then do my tuning with upgrade AC cords. Every AC cord sounds different; you'd be surprised at the changes in tonal balance that can be accomplished by experimenting with different AC cords on different components. Others also like to tune with interconnects & speaker cables, which does work but also adds more variables into the mix which can be very confusing trying to figure out how everything is working together. Of course these cable issues also all interact with your specific equipment & the whole synergy issue then becomes even more clouded. That's why you can have a rig that's tuned up very nicely, & then changing any one of these variables really messes the whole thing up.
Mark above also mentions resonance control, which could be very important esp. in this case where a specific frequency band is really acting out. This resonance behavior could be related to floor movement, your equipment rack, the room, etc. Look into component isolation & vibration control which is a whole 'nother subject altogether. Cones coupling speakers to the floor or to a shelf could do a lot of good here. I really wouldn't be blaming the amp & speakers etc; you have some good stuff there.