# Why is a flat target response, curved in REW?



## mpompey (Jan 5, 2007)

I've recently purchased a Behringer DSP1124 BFD and am using it with Room EQ Wizard to tame some bass peaks in my room. Unfortunately due to the size and shape of my room, my sub can only go into one of three places. I must say after a week of playing with it, the difference is amazing. It has actually cleared up some of the boomy muddiness that plauged some of my DVDs. King Kong, Sky Captain, and Matrix Revolutions just had boomy bass all over it. Now it has really tighten up, I wish I would have done this earlier. However, I do miss some of the oomph! in those scenes. I figured I would try experimenting with House curves to reclaim some of that.

In Room EQ Wizard, the Target Response curve has a slope to it, that's without adding a House curve to it. Shouldn't it be flat from 20Hz out? Am I confused in my thinking? The Target Response curve starts around 30 Hz and slopes downward. But in various articles and help files that refer to getting a room's response to flat; each shows a picture of a Target Response that is curved. Why is that?

I think I understand the psycho-acoustic effect of a higher bass note sounding louder than a lower one. But if I EQ my room to follow the target response curve, it looks like there is already a built in curve for those lower frequencies. Am I missing something?


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## JohnM (Apr 11, 2006)

The target response is following the bass management curve of your processor, which is typically set to be -3dB at 80Hz and rolls off at 24dB/octave above that. When measuring the sub with the test signal fed via a processor that is the shape the response should have. You can set up REW to yur processor's actual settings using the cutoff control. If you measure with the sub and a main speaker playing, the overall response should then ideally be flat, and you should set the speaker type in REW to "full range".


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## brucek (Apr 11, 2006)

The REW target response of a subwoofer corresponds to a standard crossover filtering that your receiver provides. If the crossover is set to 80Hz, then the subwoofer output gets lower and lower as the frequency increases.

When the mains speakers are set to small, their output will also be filtered by a crossover in your receiver. Their output gets lower and lower as the frequency decreases.

When the sub and mains are added together the result will be a flat frequency response.

brucek


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## cyberbri (Apr 27, 2006)

Lower frequencies are harder to hear. I have my sub pretty flat to around 30Hz, with "house curve" below that letting the room gain boost the frequencies in the 20s for plenty of that oomph. So the main bass frequencies for music are flat, with the deeper stuff found mostly in movies getting the room gain boost.

Also, there is more audible "oomph" in the mid-bass region of 50~80Hz, like for kick drums, so if the response is uneven and that range is lower than the rest it may feel lacking.

Here's how I have mine, although I tweaked a few filters after taking this.


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## Chrisbee (Apr 20, 2006)

Going off on a bit of a tangent (as usual): 

It should not be forgotten that house curves are age-related. 

If you have your ears tested regularly your will find as you grow older that you lose sensitivity to the bottom end as well as the top. (pardon?)

One man's meat is another's poison. 

Even one higher frequency peak on a sub's in-room response will ruin any efforts to make a house curve work.

Whenever you hear "music lovers" saying they couldn't possibly live with a subwoofer in their system you can immediately tick off their "system room response has bad peaks" box. 

A smoothly rising response to overcome the ear's natural falling response in the bass should actually sound more real. Many subwoofer owners prefer a house curve over a flat response to bring more "life" to the music.

The better the subwoofer the more tolerant one can be of steeper house curves. Simply because they do not introduce heavy harmonic distortion further up the frequency scale when pushed hard. This completely removes the need to constantly adjust your subwoofer to match the material being played.

The Thigpen fan subwoofer is an interesting case. As a contra-subwoofer it provides high levels at very low frequencies with low distortion. This is providing reality on a scale not seen before outside the auditorium, cathedral or any street in town. Ideally it should allow a house curve to further extend the main subwoofer's own house curve. Or in other words: A response curve to closely match the sensitivity of the ears of the owner in their own AV room. The older you get the more IB drivers and/or fan subs you probably need just to enjoy the same perceived response as the years that went before.


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