# Hard knee house curve



## aellisdj69 (Aug 26, 2011)

Hi I've been trying to set my sub up using the guide minimal eq and hard knee house curve.
Having read the guide over and over I have a dilemma.
The guide says to have a steep slope between x over point, in my case 80hz, to the shelving freq, in my case 30hz. The dilemma I have is depending on how you set rew eq you get different results. If I set the eq to subwoofer and set my steep curve via that then when I run a full range sweep with my speakers enabled the overall response looks different. It no longer is a steep slope from 80hz to the shelving freq. however if I plot the settings on the full range eq setting I now have a steep curve from 80hz to 30hz, but I'm not sure which one is correct as they both sound very different.
Any help on this would be greatly appreciated.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hey aellisdj,

Welcome to the Forum!

Not sure I follow your dilemma exactly, but if the subwoofer’s slope “disappears” when you take a full range measurement, then you might need to turn up your subwoofer.

If that’s not the answer you’re looking for, can you post some graphs and your thoughts about them? It would be easier if we can “see” what you’re talking about. :T

Regards,
Wayne A. Pflughaupt


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## aellisdj69 (Aug 26, 2011)

Hi Wayne good to hear from you.
I have recently been reading your guide regarding setting up a hard knee house curve.
The dilemma I face is, I have set my house curve as per your instructions, with a x over of 80hz, to 30hz shelving freq.
when I eq using behringer fbq2496 I get this curve-








However once i run a fullband measurment with my mains in the picture my response looks like this-








Im not sure if this is how my response is supposed to look when run along with my main speakers.
If I change the eq settings to fullrange instead of subwoofer my curve now looks concave.
I can now plot my straight line with the eq target settings set to full range and after running a full range sweep again my plot shows this-







This now shows my sub response rising from 80hz . This is where the uncertainty lies.
I hope this is more understandable, and hope the pictures have been uploaded properly.
Thank you very much for your help.
Regards
Adam


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hey Adam,

It looks like perhaps your mains are set for “large,” and are overlapping down into the subwoofer’s territory and over-riding your sub’s house curve. Even large main speakers set for “small” can have enough low-frequency output to effectively push their response below the point where smaller speakers would roll out.

If none of this applies to your situation, then it simply looks like you need to turn the subwoofer up.

Regards, 
Wayne


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## aellisdj69 (Aug 26, 2011)

Cheers Wayne, 

I'm using small speakers which are definitely set to small with 80hz x over, perhaps I need to turn the sub up but that does result in a lot of bass output and it also seems that my sub is directional, not with music but big action films.
Thanks for your help ill keep tweaking as I can already hear the benefits of using your house curve.


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## aellisdj69 (Aug 26, 2011)

Sorry Wayne, one last question.

If I have my curve set correctly, when I run a full range measurement should it show my subs response rising steeply from 80hz up to 30hz, or would it still have the tendency to look more like my first pic I posted.
Many thanks


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hey Adam,

Once you have the proper house curve set up for your sub (meaning you have the lower frequencies in the ~30-Hz range sounding as loud as the upper frequencies in the 80-90 Hz range), then it’s just a matter of blending it with the main channel speakers so that it sounds right. You can’t really go by a graph. All things being equal and sounding correct, the graph will look much different in a large room compared to a small room.

Regards, 
Wayne


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## aellisdj69 (Aug 26, 2011)

Ah thanks, seems I was paying too much attention to the full range measurement. 
Thanks for the clarification.


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## Shinx (Mar 28, 2013)

Hi,

I will also try out this hard knee curve. But before I go into the PEQ of my DCX2496 or the subs PEQ with 3 filters in my UMC-200, I have a question.

To get a frequency curve fitting to the hard knee curve you need to adjust the sub filters. Lets say 3 are necessary for example. If you are running stereo mode now, the hard knee sub curve is used together with the front speakers separated by the crossover frequency.

So far so good.

But how does it affect the movie sub lfe channel. Without separate PEQs for the subs used in stereo mode and the sub used in the LFE, the filters which were applied to press down the curve to the hard knee style, these filters are also working on the LFE. But LFE will go to 120hz. If the filters are active, the frequency curve of LFE is not linear anymore.

So, how to implement a hard knee house curve for movies with 7.1 channels?

Thanks a lot

Shinx


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## aellisdj69 (Aug 26, 2011)

Hi, you are correct in what you are saying, firstly it is said that there is very little lfe content above about 80 hz, however I changed my settings in rew so that I equalised up to 120hz. I'm aware this uses more filters and is probably not needed however I went with it.
I would urge you to try out the hard knee curve though as I've not looked back since.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Shinx said:


> But LFE will go to 120hz. If the filters are active, the frequency curve of LFE is not linear anymore.


Perhaps someone more knowledgeable can correct me if I’m wrong, but I believe the LFE content / output is controlled by the receiver’s crossover, and anything generated above the crossover frequency is directed to the main speakers.




> Without separate PEQs for the subs used in stereo mode and the sub used in the LFE,...


You will need separate equalization for the LFE sub and the stereo subs.

Regards, 
Wayne


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## Shinx (Mar 28, 2013)

Hi,



> firstly it is said that there is very little lfe content above about 80 hz


Where so you read this? According to my experience and what I have read in Forums there is enough content above 80Hz, that you directly notice it, when you cut the LFE. In fact the limit of 120Hz for the LFE is a direct cut at 120hz, no slope. So content with 110hz has 100% level.



> Perhaps someone more knowledgeable can correct me if I’m wrong, but I believe the LFE content / output is controlled by the receiver’s crossover, and anything generated above the crossover frequency is directed to the main speakers.


As far as i know, it is different. The LFE-channel is without any crossover if using a mutlichannel system with seperate sub for th x.1 output. If you have small mains with a crossvover at 80hz, the signals of these channels are routed (based on the crossvover) to to subs to, additional to the LFE. Some AVRs offers an opposite way to route the LFE signal to the mains. I think the intention is to use bass potent main speakers to get a better LFE performance if you have no or small sub on the LFE channel. From my experience, this routing sounds not very good, precision is missing. So I have a crossover at 80Hz and a limit on the LFE at 120hz.

But unfortunatley, I do not have the option to PEQ the sub signal generated by the stereo with filters which are not activ on the LFE. 

But what I can try is to adjust some filters below 80Hz in the stereo channels. I will check if they have impact on the sub without affecting the LFE

Shinx


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