[rblnr]

I suspect that there is a problem w/the crossover in my processor, but wanted to run this by people here.  I recently purchased the RM40's for mains and the LRC for center

I own the Meridian 568.2 processor/598 DVD combo and it seems that the RM40's  output no more bass than the LRC.  Holding my hand up to an LRC woofer, I feel more air moving than if I do so at either of the 40's large drivers.  The speakers are calibrated for level and phase.  My processor is set for the 40s at large and the LRC at small, with its crossover set at 60hz.    


I realize the above 'hand test' isn't scientific and perhaps can be explained that the smaller driver require more excursion, so I used bass test tones on the AVIA disc -- basically it counts down from about 190hz to 20hz, and measured using a radio shack db meter.  I am inexperienced at this, so perhaps my methodology is wrong.  And the readings are by nature not 100% accurate; the meter needle was traveling around and I'd have to eyeball it vs. the frequency # on screen.

Some other details:  AVIA works in DD, which I ran as Discrete on the 568.2.  My room has some acoustic treatment, bass traps in the corners behind the speakers, some acoustic panels behind and on the side wall at the point of first reflection as well.  These panels are homemade w/blade foam on boards, they are probably more effective at high frequencies.   My speakers are along a nine foot wall, about 18" from the rear and 8" or so from the sides.  A 55" RPTV sits between them, about 8" behind their front plane.  They are angled to crossfire about a foot in front of my listening position which is 10' away.  The center channel sits atop the monitor and is angled down w/shims.  

Here are my results, Hz tone followed by #'s for Left, Center, Right.   Sorry I can't get it to format more cleanly.

                     L         C          R  

120             4         0         -0

110             1          2         -2

 90              3          0           4

 80              1          0          2

 70             -4        -8        -2

 60            -2         -3        -2

 50            -4          -2         0

 44             6           3           3

 40              0           2          1

 35            -1          -1        -2

 30           -4           -2        -2

 25           -2           -1          -2

Got some rattles in the next room at lower frequencies

Questions:  Do these #'s indicate that the crossover is perhaps not working?

Are these kind of 'all over the place' #'s typical for in-room measurement?

Any other thoughts here?

Any help appreciated as I try to determine what, if anything, is going on here.

[/list:u]

[Brian Cheney]

We measure the LRC flat to 42Hz with strong port output to 35Hz.  Since the port is much smaller than the PR slot the "wind" seems stronger.  Not a matter of consequence.

You can get a lot more oomph from the RM 40 bass section by undamping the PR (removing putty a fingernail full at a time).  Most people remove a mass the size of a large pea to the size of a small lima bean.  It is the most important adjustment you can make, as the system is supplied from the factory overdamped (bass output restricted).

[rblnr]

Brian,

Thanks for the reply.  So far I've removed about a small pea's worth, so I'll try some more.

My reason for the crossover concern is that I would expect the LRC to be rolling off at around 55 or so given my settings on the processor, and that bass being redirected to the mains.  The numbers don't indicated any rolloff to me, but I'm an amateur in this area.

[Brian Cheney]

Disconnect your processor and run a signal directly to the power amp.  If you hear a substantial change in bass response from the RM 40 your processor is doing something wrong.   It sounds like the LRC is getting a fullrange signal.

[flintstone]

Would also suggest that some reading on speaker/room interface may be of great help. If one were to place a spl meter at your listening spot and have someone move a sub around the room, the readings would change    (+/-) output for each spot.  I would try to find best bass output if you have some room to play with as far as speaker placement goes and then fine tune passive as Brian suggest's.

[rblnr]

Not sure whether or not the LRC is getting a full range signal, but did run the center lead to my left channel, and the left to the center.  Bass output did not change to the left vs. the correct setup, indicating to me that it is most likely receiving a full range signal from the processor so the bass shy feeling I get is from the speaker itself.  Removed some more putty which helped; I'd estimate I'm at a large pea by now, say a little over a quarter inch in diameter.

It occurs to me that in setting up processor levels using generated test tones, the setting of the mid level on the RM40 is extremely important as that is where the test tone primarily resides.  

Say I've got the mid-level set too high; wouldn't the test signal then be louder than it might otherwise be so I would follow through by lowering the level of that speaker which would reduce it's bass output relative to other speakers in the setup?

And, of course, raising the mid too high (or treble) will reduce the bass vs. the rest spectrum within that speaker.

I'm finding these adjustments a little tricky; what sounds right for one track is off for another.