BK Monolith problem

JazAV

Standard Member
I have a BK Monolith Plus and something strange is happening. I use it in 5.2 setup and always felt it sounded odd. I have it level matched with the other sub, but as the frequency contour is set to max LFE I thought everything is set perfectly. But it sounds nowhere near as deep as my much smaller Klipsch R-12SW. And that's just it - it sounds tight but not deep. When I switch the frequency on the back of the Monolith to max 120hz without clicking to LFE mode, it all sounds perfect. Bass is rich, deep and powerful. I currently have it left in this configuration but I know it's not the correct setting.

AVR is a Denon x2400h and crossover settings are fronts 80hz, center 120hz, rear 100hz.

Why does it sound like a proper Monolith only when not set at LFE?

Whats's wrong with the subwoofer?
 
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andym81

Active Member
Sounds like your subs are cancelling each other out, denon 2400 wont eq two subs .

Have your tried changing the phase ?
 

JazAV

Standard Member
Yes I have adjusted the phase already and have the best results with the Mono at 180 and the Klipsch at 0. Could this still be the problem?

Both subs at back opposing the fronts so adjustments had to be made. Also why does setting the crossover from LFE to 120hz fix the Mono? This should not affect phase. But it does?
 
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andym81

Active Member
You need to leave the LFP of LFE at 120hz.
This is completely separate to your speaker crossover.

If you have both subs at the rear the both need to be set to 0
 

JazAV

Standard Member
I have both subs at the rear but not symmetrically at the same position. The mono is about 70cm (27.5") closer than the Klipsch to the listening position. The mono sounded completely nulled at 0 degrees hence the change. These are the only 2 subwoofer positions in my room and I have already swapped them around to get the best, smoothest frequency response to my ears and measuring. I tried 90 degrees and all in between too and 180 sounded best and also measured best. Also i tried 180 on the klipsch and all sorts before coming to the klipsch at 0 and mono at 180 conclusion.

I still don't understand why LFE mode on the mono does not work very well as the monolith is being used for LFE and why 120hz sounds a lot better.

Comparing the two subs in LFE mode, the Klipsch sounds perfectly fine.

Is there anyone out there who can help me figure this one out?
 
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Dolus

Active Member
My first Mono+ bought in 2013 and used with an Onkyo 809 AVR sounded OK in both 120 Hz and LFE mode, On a few films that went really low there was distortion in LFE mode, not unlike the driver reaching the limit of it's travel. I found out the distortion was not present when switched 120 Hz so used it like that. I emailed BK about it and received a reply from Tom at BK who could not explain it.

Fast forward to 2016 and a second Mono+ which did the same thing switched to LFE so was also used at 120 Hz. At this point I figured it was not the Mono+ as there would be more people noticing it.

Fast forward to 2018 when my Onkyo AVR gave up and died and was replaced with a Denon 6400.Now both Mono plus's work perfectly in LFE mode, so the mystery still remains.

I assume you get the same thing happen if exclude the Klipsh and use the Monolith on it's own. I would use it at 120 Hz or if it bothers you contact BK and see what they have to say. Maybe 5 years on from when I asked there might be an answer.
 

JazAV

Standard Member
Thanks for your input. I will call BK and ask them.

I'm a little surprised that you had the same problem on both Monoliths. I'm having my trouble with a Denon connected to it - so I suppose I can't fix mine by buying an Onkyo!

I'll see what they say when I call them and let you know.
 

Ultrasonic

Well-known Member
Both subs at back opposing the fronts so adjustments had to be made. Also why does setting the crossover from LFE to 120hz fix the Mono? This should not affect phase. But it does?
Going to LFE probably bypasses the filter entirely so this certainly could affect phase (delay). In fact I'd be surprised it if didn't.
 

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