# Trying to grasp Hard Knee House Curve



## cburbs (Mar 27, 2007)

OK so I read the "Minimal EQ, Target Levels, and a Hard-Knee House Curve" a few times.
Reason is I want to rerun my eq since I added my acoustic panels. They have been in for a while now but I feel like playing again.

If my crossover is at 60hz on my receiver how should I go about setting up a HKH Curve in my situation? 
Wayne responded with the following -

Hmm... Well, I guess you have no choice but to do it from 60 Hz down. You might experiment with different frequencies for the low frequency "hinge" - say, 30 Hz, 28 Hz, 25 Hz - to see what gets you the best results.

Since you probably want the curve to continue above 60 Hz, what you could do is go ahead and create the HK curve in REW all the way up to 90-100 Hz or so, just as if your crossover was set there, and take a reading with both the subs and mains on. That would let you know if the mains were kicking in enough to maintain the HK curve above the 60 Hz crossover point. 

*The last part confused me - any help on it would be appreciated.*

Also to make sure I am understanding his article and how to create a HK slope - 

Wayne mentions - I usually start with the upper frequency tone - *So 60hz in my case, and make a note of its SPL reading - say 75spl @ 40 volume on pre/pro*. Then play the lower-frequency tone *- say 30hz *and adjust the receiver’s volume so that it sounds as loud as the first tone did. This will be a higher SPL reading than the first; the difference between the two readings is your house curve slope - *so say I have to increase volume to 43 and the spl reads 80. This would be a 5db increase in spl or a 5db HK slope*. Am I correct on this?


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

Even though your crossover is set at 60 Hz, you probably want the house curve to go higher than that. Create your hard-knee curve using say, 90 or 100 Hz as your upper frequency (instead of 60 Hz) and load the file into REW. Set the crossover frequency in REW at the same frequency (90 or 100 Hz). It'll look something like this (90 Hz in this example):










Then take a measurement with both subs and mains running. This will tell you if your main channels are kicking in enough to continue the curve above 60 Hz, where your sub drops out.

Make sense? 

Regards,
Wayne


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## cburbs (Mar 27, 2007)

In reference to - set the crossover frequency in REW at the same frequency are you referring to the target settings and cutoff(hz)?

Am I right on how to create the HK slope?


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

Just set up and run both your house curve and REW as if your crossover were 90 or 100 Hz. Simple as that. :T

Regards,
Wayne


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## cburbs (Mar 27, 2007)

So this is what I am understanding - call me slow man this weekend. The first one is 60hz cutoff and your 6db HK curve and the second is 90hz/6db HKC.

So you are saying use the 90hz one.


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## cburbs (Mar 27, 2007)

Anyone else want to help me out to make sure I am understanding this?


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

Sorry, didn't notice that you'd gone back and edited the post (don't get e-mail notification when that happens!).



> So you are saying use the 90hz one.


Correct.

Regards,
Wayne


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## cburbs (Mar 27, 2007)

Am I assuming right on the following - When you want to run rew on both speakers and sub 
you select speaker cal -


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## brucek (Apr 11, 2006)

> Am I assuming right on the following - When you want to run rew on both speakers and sub
> you select speaker cal


Nope, not when you're only checking up to 200Hz - you use sub cal pink noise.

brucek


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## cburbs (Mar 27, 2007)

So when would one use the speaker cal pink noise?


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## brucek (Apr 11, 2006)

When measuring mains by themselves.

The sub cal pink noise is a band limited pink noise with a high cut of 80Hz and low cut of 30Hz. That energy range is quite suitable for measuring in the 0-200Hz region.

The speaker cal pink noise has a high cut of 2000Hz and a low cut of 500Hz, far more suited to testing mains speakers by themselves.

brucek


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## cburbs (Mar 27, 2007)

Cool thanks for the info - appreciate it.


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## cburbs (Mar 27, 2007)

OK here are some graphs then...

1 - 60 xover sub only light blue - mains and subs dark blue
2 - 70 xover sub only dark blue - mains and subs light blue
3 - 80 xover sub only dark blue - mains and subs light blue
4 - 90 xover sub only light blue - mains and subs dark blue


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

Where's the hard knee target curve? :scratch:

I assume you only took one "with mains" reading, and not a new one with each crossover setting? 'Cause it looks the same with each graph...

Regards,
Wayne


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## cburbs (Mar 27, 2007)

Is there a way to show all measured with the house curve?

I am positive those are all different measurements 60 - 90 xover.

I can remeasure again....


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

> Is there a way to show all measured with the house curve?


Hmm... Doesn't look like it...

Regards,
Wayne


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## cburbs (Mar 27, 2007)

I used your 6db HK Slope. Here is an example after 90 xover on receiver after filters.

Quick though - If I am using your 6db HK slope and prefer my receiver at 60 xover what setting am I suppose to use in the cutoff under target settings -

Is this 60 because of my 60 xover on the receiver or is it 90 because of the housecurve I am using?


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## cburbs (Mar 27, 2007)

Second shot is before and after.


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## cburbs (Mar 27, 2007)

This is a pic of all subs only 60-90hz xover


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

Got anything showing the subs and mains, using the crossover point you intend to use, showing the Target curve?

Regards,
Wayne


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## cburbs (Mar 27, 2007)

Here are the subs/mains at 60hz xover on the prepro. I am using your 6db HKS.


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

Not bad. If you could deal with that bump at 60 Hz I think you'd have it nailed. That's the downside to dividing that low...

Regards,
Wayne


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## cburbs (Mar 27, 2007)

That is no EQ involved -


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

Yeah, it would be a toss up as to whether or not EQ would help there. Assuming that both the mains and subs are contributing to the peak, EQing down the sub might help, but probably not fully eliminate it.

But overall, it looks like the sub and mains are blending for a good house curve, which is what we were trying to determine to begin with.

Just for grins you might try changing the graph's axis from 45-105 to 20-130 and see what that looks like. I personally think the latter is a better visual representation of what response actually will sound like; the 60 Hz hump might be one of those "looks worse than it really is" deals. 

Regards,
Wayne


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## cburbs (Mar 27, 2007)

I will - I want to rerun some of subs & subs/mains at different crossovers again.


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## cburbs (Mar 27, 2007)

Another quick easy ? - do most people point there mic straight up and down? I always have pointed mine to the front where the front wall and ceiling meet - if I recall an article suggested this.


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## brucek (Apr 11, 2006)

An omni, such as the ECM8000 is straight up and down. A directional, such as the Radio Shack is up and forward at an angle.

brucek


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## Bob_99 (May 8, 2006)

brucek said:


> An omni, such as the ECM8000 is straight up and down. A directional, such as the Radio Shack is up and forward at an angle.
> 
> brucek


Would you mind elaborating on this a bit? I feel that straight up and down gives you reflections off the ceiling but obviously there's more to it and I'm not seeing it.

:huh:
:scratch:

Thanks.

Bob


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## cburbs (Mar 27, 2007)

brucek said:


> An omni, such as the ECM8000 is straight up and down. A directional, such as the Radio Shack is up and forward at an angle.
> 
> brucek


That is what I do up and then angle it....


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## brucek (Apr 11, 2006)

> Would you mind elaborating on this a bit?


You're going to get reflections from everywhere. An omni-directional mic allows you not to have to point it to any source - so, straight up and down at the listening position is fine. There may be specific rules with regard to near-field testing, but for home theater at the listening position, vertical is fine for the ECM....

burcek


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## cburbs (Mar 27, 2007)

I re did my eq again - ? on the two red areas - do I bring any of this up by doing a boost in the eq? This is before any eq at all.


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

Yikes, what happened? You were getting good extension out to 20 Hz before. Where the graphs on the first page with EQ?










The 80 Hz thing is probably doable with some boost. We can see from your previous graphs that the whole thing can be raised and lowered; that suggests it is not a null. Curious as to why, like the extension, that it looks worse now than it did before...

Regards,
Wayne


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## cburbs (Mar 27, 2007)

I may have to redo this again as I was playing around with an amp setting and not sure if the reading you just posted was before or after the change.


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## cburbs (Mar 27, 2007)

Well I had some time again today to play around with it again and this is what I got.The viewing window is 20-130 .


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## cburbs (Mar 27, 2007)

105-45 window.


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## cburbs (Mar 27, 2007)

latest graph....


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