# Applying House/Hard Knee Curve



## jlafrenz (Jun 6, 2010)

I have been reading up on how to apply a house curve to my subs to improve the sound after flattening the response with REW and the BFD. I thought I had the basics covered and was ready to give it a try. Once I tried it and became a bit confused as to weather I was doing it correctly. I am hoping for some clarification so here are a few of my questions.

1.Let me start off by stating that I used REW and the BFD to calibrate the subs only. My mains were not used and are not represented in my graphs or filters. That being said, when determining a house/hard knee curve, do I want to include my mains or just the subs to figure out the slope?

2:When measuring the test tones, what is the best way to do it between the 2 following options:

A: Set the processor at a particular volume, play each test tone and measure the difference between them via the SPL meter while keeping the volume the same. My initial thought is that this is incorrect because they should play at a similar volume because of the applied filters. But, I did notice that there was some change in doing it this way. 

B: Play the first test tone and take note of the SPL reading. Then play the next tone and adjust the volume of the processor until it sounds like it is at the same volume and then take note of the SPL reading. I believe this to be correct per the House Curve readings. The issue I am facing is that it is quite difficult to hear the difference in volume change because of the difference in frequency. When I did it this way, the volumes sounded almost the same and did not get that much of a difference on the SPL meter when adjusting the volume. 

3: Once I decide on my measurements and make the .txt file, I assume that I pull up REW and apply it to the filter file that I used to flatten my subs and then resend it to the BFD?


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

> That being said, when determining a house/hard knee curve, do I want to include my mains or just the subs to figure out the slope?


You can include the mains. After all, at the upper frequency evaluated (at or near the crossover frequency), the mains are typically overlapping the sub, and that’s the way you’ll be listening to your system after it’s all said and done.




> 2:When measuring the test tones, what is the best way to do it between the 2 following options:


Option B is the best.




> The issue I am facing is that it is quite difficult to hear the difference in volume change because of the difference in frequency.


Surely you can. Are you telling me that running the volume control up or down, or flat-out muting, you can’t tell a difference? 




> When I did it this way, the volumes sounded almost the same and did not get that much of a difference on the SPL meter when adjusting the volume.


How much of a difference was there? It might be that your room doesn’t require a drastic house curve. :T




> 3: Once I decide on my measurements and make the .txt file, I assume that I pull up REW and apply it to the filter file that I used to flatten my subs and then resend it to the BFD?


 Look for the “House Curve” tab in the Settings window. That’s where the house curve loaded. After it’s loaded you’ll see a change in the Target Curve on your screen.

Regards,
Wayne


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## jlafrenz (Jun 6, 2010)

I did notice that there is more of a difference in volume between the 30Hz tone and 20Hz tone so I might give 80Hz and 20Hz a try to determine a slope.

I think I still need just a bit more clarification on the last part. I realize that it will change the target curve, but my question is to I use that in conjunction with the filters I already have in place that have flattened out my response or do I need to make a new target curve and then rerun the test to get new filters?


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## laser188139 (Sep 19, 2009)

As Wayne wrote, configuring a House Curve itself changes the target curve. 



jlafrenz said:


> ... to I use that in conjunction with the filters I already have in place that have flattened out my response ...


Obviously, the current filters give a fit to the previous target. As the target curve has changed, new filters must be defined. Without defining new filters, the result is unchanged. 



jlafrenz said:


> ... or do I need to make a new target curve and then rerun the test to get new filters?


There is no need to rerun the sweep to generate the data sample, except to reflect any changes in the room environment. You can generate new filters using the same data sample you already measured. 

Bill


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## jlafrenz (Jun 6, 2010)

I finally took the time to apply the house curve. Here is the graph.










It does sound a lot better than with just a flat curve. I am still not sure I like as compared to no EQing at all though. It is really tough to say. Some movie scenes sounded pretty good, but a music Blu-ray still sounded bloated towards the top end. Is this because my mains are starting to take over the handling of these frequencies with the house curve and the sub dropping off? I also noticed when I was working on the house curve, I have a dip of a couple of db at 80Hz with the mains on so there is some interaction there. I also noticed that there is a slight dip with the sub EQed (without mains). I might look into correcting that. I also need to switch back and forth with EQed vs. non-EQed to see what I like best.


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## jlafrenz (Jun 6, 2010)

Not sure how I missed it originally, but after reviewing my graph, I notice a significant drop at the 30Hz range (which I used to determine my house curve). I would think that it would obviously be ideal it it was up at the target line which has been set by the house curve. My question is should I add a filter at 30 to bring up the dip or should I add one at 20Hz to bring the whole bottom end up to the target line?


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

Yeah, you have the curve shelved at ~48 Hz, which is pretty high. It will probably sound better shelved at 30 Hz or a bit lower.







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> My question is should I add a filter at 30 to bring up the dip or should I add one at 20Hz to bring the whole bottom end up to the target line?


Doesn’t really matter. You could also just adjust the volume (or Target Curve) to get the area 30 Hz and below at the Target, then cut everything else to meet the Target. Either way, you’re going to end up with 30 Hz and below boosted.

P.S. you have the graph set for linear mode. Change it to LOG.

Regards,
Wayne


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## jlafrenz (Jun 6, 2010)

Can you expand a bit more on "shelved at 30Hz"? Your red line looks to have the same slope as mine. I notice that it is lower in the graph. The reason for why mine is set so high is because of the 10db drop in LFE from my player. So readings on the graph would actually play 10db lower when I am watching a movie. 

Where do I need to change to LOG mode?


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

> Where do I need to change to LOG mode?


Look for a control or icon that says “Freq Axis.”




> Can you expand a bit more on "shelved at 30Hz"?


”Shelving” is the frequency where response stops rising and flattens out.




> Your red line looks to have the same slope as mine.


Look at your _actual_ response, not the Target. It levels off to flat at 48 Hz, not 30. You need to track the Target better, especially at the bottom end.







​


Regards,
Wayne


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## jlafrenz (Jun 6, 2010)

After I posted last night, I noticed too that 30Hz and below was not at the target line. I did go back and manually add some filters to boost it. I didn't have time to post the graph this morning, but here is the latest one.


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

Well, you’re still shelving at 48 Hz, not 30. And where did that big hump at 80 Hz come from? It wasn’t there before...

Looks like you used 2-3 “notch filters” (i.e. ultra-narrow) to get the 20-30 Hz boost. So I’ll bet you’re using a whole slew of filters by this point. Can you post a picture of your original baseline response look like? With the graph set for LOG, please. Maybe I can recommend a new plan of attack. 

Regards,
Wayne


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## jlafrenz (Jun 6, 2010)

Your right. I am now using a few more filters and the ones for 20-30Hz were pretty sharp in order to bring the levels up. I should have mentioned that I also removed the filter at 80Hz because it was a bit low and there was some cancellation with the mains present causing there to be an even larger dip. Once I get a chance to, I will switch my graph to LOG and repost.


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