# LFE + Bass Management Question



## BraveHeart123 (Oct 18, 2010)

I've been caught in this dilemma for quite a long time now but seems I'm chasing my own tail.

As I understand; Bass and LFE are two separate things.

I use my HT purely for movies. I cailbrate my sub in REW to dial a house curve, which pretty much rises by 6-7dB till 28hz starting from 80hz i.e. the SPL difference between 80hz and 28 Hz is 6-7dB. Let's say if my SPL is 75dB at 80hz; it is about 82dB at 28hz before the roll off occurs. After some manual tinkering with the REW filters; I insert the same filters in BFD-1124p.

*Problem*

As per my understanding, LFE is separate from normal bass content in DD and DTS and latest high def audio formats. At the same time, LFE is mixed 10dB higher than the higher frequency content in movies. My question is as follows;

Does the house curve dialed in REW to maintain the perceived loudness cater for redirected bass only or redirected bass + LFE? 

I am asking this coz I see signal clipping red lights in BFD turning on during sudden transient response scenes e.g. car crashes, explosions, war scenes. LFE gets to over power the mains coz it is already 10dB hotter + house curve makes it around 17dB hotter. 
If I try to reduce the slope of house curve; the LFE falls within range but it also kills the redirected bass and I get very thin sound.

My AVR is Onkyo 809, mains (Klipsch RF-82 II), center (RC-62 II), Surrounds (RS-52 II), Subwoofer (Klipsch SUB-12), BFD-1124p. My crossover is 90Hz on the receiver for all the speakers. Also, I eq the sub first and then run Audyssey.

Pls help me on this.


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## Jungle Jack (Jul 28, 2009)

BraveHeart123 said:


> I've been caught in this dilemma for quite a long time now but seems I'm chasing my own tail.
> 
> As I understand; Bass and LFE are two separate things.
> 
> ...


Hello,
Indeed LFE is separate from FL/CC/FR/SL/SR. I would try using an 80hz crossover as your Klipschs can certainly handle it and it will take some strain off the subwoofer. Hopefully, this will in turn stop your subwoofer from overloading.
Cheers,
JJ


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## BraveHeart123 (Oct 18, 2010)

I've tried lowering the crossover point; but it lowers the bass impact coz RF-82 IIs cant pull out enough current from AVR to give that famous chest thump. Can you pls answer my question about house curve in my post??

It's not the redirected bass casuing signal to clip; it's rather the LFE which has to go to sub from 120Hz and below. It's coz of the 6dB raise employed in ultra-low and low frequency spectrums for the house curve.


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## Jungle Jack (Jul 28, 2009)

BraveHeart123 said:


> I've tried lowering the crossover point; but it lowers the bass impact coz RF-82 IIs cant pull out enough current from AVR to give that famous chest thump. Can you pls answer my question about house curve in my post??
> 
> It's not the redirected bass casuing signal to clip; it's rather the LFE which has to go to sub from 120Hz and below. It's coz of the 6dB raise employed in ultra-low and low frequency spectrums for the house curve.


I think it is not so much the house curve than it is the limitation of the Sub-12 not being able to handle the added gain employed by REW. Also, the Klipschs are ridiculously efficient and the 809 should have no issues driving them down to 80hz. Moreover, ideally you would not want "chest thumping" bass at 80 or 90hz and rather have solid bass all the way down to ideally 20hz. It appears you are overloading the subwoofer.


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## BraveHeart123 (Oct 18, 2010)

SUB-12 comes into play in the end. BFD is there in the sound chain. The clipping occurs within the BFD itself before the signal goes to the sub. Also I am using BFD in professional +4dBV mode to avoid clipping as opposed to the home setting i.e. -10dBV. The clipping occurs at -10dBFS. 
My normal listening is at -20dBFS. Also the sub is located in the most suitable spot in my room with least peaks and dips. I've verfied with REW


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## Jungle Jack (Jul 28, 2009)

BraveHeart123 said:


> SUB-12 comes into play in the end. BFD is there in the sound chain. The clipping occurs within the BFD itself before the signal goes to the sub. Also I am using BFD in professional +4dBV mode to avoid clipping as opposed to the home setting i.e. -10dBV. The clipping occurs at -10dBFS.
> My normal listening is at -20dBFS. Also the sub is located in the most suitable spot in my room with least peaks and dips. I've verfied with REW


I truly do understand the signal chain and it is great that you have maximized the SUB-12. I did not realize that you were somewhere that purchasing a different Subwoofer like a HSU Research would be so much more difficult. I would still lower the crossover to 80hz to take strain off the subwoofer. However, provided that the current situation is what makes you happy, go with it.


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## BraveHeart123 (Oct 18, 2010)

I know what you mean  But Pakistan isn't that out-dated in terms of audio equipment. I have auditioned REL Gibralter G1, Focal JMLabs SW 1000 Be, was about to buy Velodyne DD-15 Plus but held on coz Velo was not made in US. Didn't like the REL Gibralter G1 and JMLab subs in HT mode.
I am in the process of deciding between Def Tech SuperCube Reference and Trinity models, which I will be getting in a month's time. So, it ain't that bad here 
Anyway, the signal clipping is occuring before it lands in the sub......that means even if I hookup SVS PB13 Plus or HSU or eD, the signal will still clip in the current situation. Why??


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## BraveHeart123 (Oct 18, 2010)

Let me rephrase my dilemma;

I adjust the target curve (House Curve Added) in REW to such a level that my sub response is (81dB) 6dB higher at 30hz and it linearly drops to 75dB at 80Hz and then it goes flat onwards.
All the speakers are at 75dB. Subwoofer is also level matched (75dB) with all the channels till 80-90hz. But the level starts rising linearly from 80hz and slopes up by 6dB down to about 30hz.
*My Question*
What will be the SPL level of redirected bass at 30Hz???
What will be the SPL level of LFE at 30Hz, which is by default recorded 10dB hotter (85dB) than all the other channels???
Is this 10dB difference between LFE and redirected bass causing clipping in BFD casue the summed up bass goes way up on the dB scale???


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## BraveHeart123 (Oct 18, 2010)

Anyone??


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## Jungle Jack (Jul 28, 2009)

Hello,
I recommend asking this question in the Subwoofer and or REW Subforums. That being said, your SPL at 30hz is about impossible to say due to variations in ones HT Room. Of course, you can use an SPL Meter to measure it, but with Room Nulls and Voids it makes it more difficult. Also, with LFE, AVR/SSP's take this into account and playback is automatically set 10db higher. 
Here is a good article about this:http://www.hometheaterhifi.com/volume_7_2/feature-article-misunderstood-lfe-channel-april-2000.html
Cheers,
JJ


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## BraveHeart123 (Oct 18, 2010)

Thanx JJ. The article you mentioned is an excellent one. It cleared my concepts on LFE levels. I figured out the problem now. The clipping occurs when I am past -10dB. The bass doesn't clip below -10dB. I completely forgot that DVD and BR are recorded at 85dB. The 0dB reference scale on Onkyo 809 master volume while playing DVD and BR is actually 85dB and LFE 95dB, so trying to play those at such volumes causes clipping. 

Excellent tutorial and thanx for your help and patience. Thanx


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