# House Curve clarification



## Todd Anderson (Jul 24, 2009)

I read through Wayne's House Curve info... great stuff Wayne and very compelling.

I'm at the stage where I have, over the last several months, purchased a BFD and built my own acoustic panels. Everything - after seemingly forever - is finally in place.

I was able to get my FR for my sub relative flat... 

I just wanted to clarify 2 things (and these are probably relatively simple):

1) Assuming my set-up is calibrated at 75dBs... a house curve for my sub means that my sub will be equalized to 75 dBs at 20Hz... and between 20Hz and 80Hz this dB level should gradually go down about 6 or 7 dBs to 68dBs at 80Hz. Yes?

2) I'm not quite sure if I get the whole shelf concept as it applies to my set-up. My Elite AVR manages my speakers and sub. I have the BFG being fed the sub signal from the AVR (in other words the BFG is only receiving 80Hz). If I want to create a shelf using my BFG in this scenario, is it still possible? If so... I do this by setting a broad spectrum filter weight around 130Hz... and that will help pull down the flat response I have now????

Thanks... I might be a tad confused.:innocent:


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

Hey 27dnast,

Thanks for the kind words, and glad you liked the article! :T



> 1) Assuming my set-up is calibrated at 75dBs... a house curve for my sub means that my sub will be equalized to 75 dBs at 20Hz... and between 20Hz and 80Hz this dB level should gradually go down about 6 or 7 dBs to 68dBs at 80Hz. Yes?


Sort of. Basically, the slope of the curve (6 or 7 dB in your case) is merely for the purpose of accomplishing the equalizing with the BFD (or whatever EQ one is using). That’s entirely different from your system calibration. After the sub is equalized, then you re-adjust its blend with the main speakers, either manually using the receiver’s rotating test tone, or the receiver’s auto calibration system (Audyssey, YPAO, etc.). Once that’s done, you’re good to go. :T




> 2) I'm not quite sure if I get the whole shelf concept as it applies to my set-up. My Elite AVR manages my speakers and sub. I have the BFG being fed the sub signal from the AVR (in other words the BFG is only receiving 80Hz). If I want to create a shelf using my BFG in this scenario, is it still possible? If so... I do this by setting a broad spectrum filter weight around 130Hz... and that will help pull down the flat response I have now????


The shelving has nothing to do with the receiver’s speaker management process. Shelving merely means that you stop the house curve’s upward slop, typically somewhere between 25-30 Hz, and response is flat below that point.

There’s no set method for accomplishing the shelving. It all depends on what your sub’s specific in-room response looks like. For instance, I got lucky and my base response had a natural slope that “played into the hands” of a house curve with minimal equalizing. So I got most of my house curve for “free,” as it were. However, if someone’s response after EQing out the peaks ends up being relatively flat, then they’ll need additional equalizing to “create” the slope and shelf. The broad 130 Hz filter is one method for accomplishing that, but depending on the response it might need to be at a different frequency, a broader or tighter bandwidth, different dB cut value,etc.

So it’s going to be different for everyone. But ultimately, it’s all accomplished with the equalizer – shelf, slope, etc. – not the receiver’s bass management. You just generate a response graph with REW, drop in a house curve file to alter the Target, and then EQ to “chase” the Target. Make sense?

Regards,
Wayne


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## Todd Anderson (Jul 24, 2009)

Hi Wayne, thanks for the response. Really appreciate it.

I think I understand your answers... It would be so much easier to talk to someone face to face about these topics (especially when you have a newbie trying to learn it!!!

When my calibration is said and done... Assuming my target is to have my main speakers calibrated at 75dBs... Assuming my sub goes down to 20hz (for purposes of discussion), then my sub at 20hz will be at about 81-82 dBs.... Gradually sloping downward to somewhere in the range of 75 dBs at the crossover point )80 Hz?


In terms of the slope itself... I'm guessing not everyone is able to get a perfectly smooth line? I say that I've managed to get a flat response... But truthfully when I measure my room with the Radio Shack SPL hooked-up to REW (using the radio shack calibration file), the line still has some little humps and waves in it. Is that normal? Or do I need to take more time to get that line smoother?


Thanks again, Wayne. I *hope* I'm on the right track. This stuff is totally fun - and articles written for the enthusiast by someone such as yourself are really cool. Thanks!


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

> When my calibration is said and done... Assuming my target is to have my main speakers calibrated at 75dBs... Assuming my sub goes down to 20hz (for purposes of discussion), then my sub at 20hz will be at about 81-82 dBs.... Gradually sloping downward to somewhere in the range of 75 dBs at the crossover point )80 Hz?


That’s theoretically correct. However, I typically go with what sounds right for my subs/mains blend, not a pre-determined rigid value. 




> In terms of the slope itself... I'm guessing not everyone is able to get a perfectly smooth line? I say that I've managed to get a flat response... But truthfully when I measure my room with the Radio Shack SPL hooked-up to REW (using the radio shack calibration file), the line still has some little humps and waves in it. Is that normal? Or do I need to take more time to get that line smoother?


Generally all you need to do is eliminate the worst peaks and depressions. It’s best not to go overboard trying to EQ out every little ripple in response. Too much EQ can degrade the sub’s sound quality, and those little ripples aren’t audible anyway. (I suggest wading through my Minimal EQ article, at least Post #1 and the “How to recognize useless filters” section of Post #2.) For an example, here’s my before and after EQ charts w/ house curve.










*Before EQ









After EQ*​

Hope this helps. :T

Regards,
Wayne


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## Todd Anderson (Jul 24, 2009)

Completely helps! I think I've got it. Now I need a little time to make it happen! Thanks Wayne!


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