sub output vs avr crossover

[al2fast]

OK, got a question and lost my first graph so I cannot show you. I have a Denon AVR890 and SS 18.2. I was having some grief trying to get REW working, think my skills or lack there of and hardware were giving me some inaccurate measurements.

So, I downloaded a test tones cd and played 15-120hz at -15 on my avr and took measurements with my radio shack meter and plugged them into excel. I had noticed a fairly steep drop off of like -15db at 80hz. I have all of my speakers set to small and crossed over at 80hz. My LFE channel is crossed at 120hz.

Would moving my speaker crossover up to say 100 or even 120 force my AVR to send more of the content to the LFE channel which would go to my SS and move that top end roll off up to 100 or 120? I know I can obviously play with it, but playing test tones and recording db with a meter sucks.

Just trying to get a better handle on what my AVR is doing. I could dig up my ghetto graph with those measurements, but then I have to tear my laptop apart and put my old hard drive back in and I'm more interested in the "how" on this question.

I am very happy with my purchase, just trying to learn more about it and then start messing around with the eq on the amp, but after reading that manual and messing with it a little bit I can hear the changes it makes, but it's back at 0 for now. Definitely no shortage of headroom below 80hz right now!

Thanks!

[fitzwaddle]

If your crossover is set for 80 (or higher), then it will start dropping off at 80, but shouldn't fall off a cliff. Does it dip at 80 and then come back up? If so, its more likely that you need to play with sub/seating location, you're getting some cancellation there due to room modes (my guess anyway).

[al2fast]

OK, thanks, that's kinda what I was hoping for. However, it is not a null per say at 80 hz, like everything just gets 10 - 15 db quieter 80hz and up and stayed relatively flat. I'll play around with it and my meter and if I get time later this week I'll re-install my old hard drive and get that graph off of it.

[rhui_bc]

audessey does a gradual roll off with the cross over, so it shouldn't be a steep drop off... but audessey is known to do funny things too.

a -15db sounds like a room null to me, maybe like a couch absorbing that wave length?
The best test is to do eliminate variables. For example, do all measurements with everything off except your sub at 1cm (at the cone), plot those into excel, it should be close to flat. If it is not flat, then something funny going on.

Next turn on the mains, return to listening position and redo the measurements. If you still get a null, either move your self or the sub to see if null changes. If it does, then you found your solution. If it does not help/change, you will have to be more drastic in the positioning.

A tip i got was put the sub where you sit, then walk/crawl around room with test tone playing to see where 80hz gives most db.

this is unrelated, but i notice you are manually plugging the measurements into excel, did you remember to plug in the mic calibration corrections as well?