# REW room response curves. Will I hear a benefit from using BFD?



## gizzykid (Mar 27, 2012)

Hi Guys

My system comprises of:
JTR Triple8LP for LCR
JTR slant8 for surrounds
Seaton submersive sub
Onkyo 809b for processing
Pro-amps for LCR and surrounds

I have just bought mic and BFD and have measured the response of the sub at all seating positions at two different sub locations (these are the only two positions available).
See graphs below.

Plot with sub located in front right corner of room








Plot with sub located at third of right hand wall








I assume the corner position gives a better overall response.
Is this correct?

I am unsure as to whether I will gain much from the BFD as all problems seem to be dips which I know shouldn't be managed with EQ.
Can anyone see any real problems that could be treated with filters?
Is the response bad enough to use filters at all?



I dont mind not using the BFD for EQ'ing the sub as it has come in handy for creating a low-pass for my buttkickers anyway (and has introduced a hum into my system).

I appreciate any feeback.

Cheers


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## gizzykid (Mar 27, 2012)

Also, if I do use the BFD to EQ the sub is there any way to get REW to average the response of all seating positions into one plot that I can apply filters to?

Or is it better to just pick a certain seating position to EQ?

Forgot to mention I had a filter set during measurements to reduce a hum in the system (the hum was caused by the BFD and the filter was at 150hz, -40db and width of 1/60). This is just a temporary measure.


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## Phillips (Aug 12, 2011)

gizzykid said:


> Also, if I do use the BFD to EQ the sub is there any way to get REW to average the response of all seating positions into one plot that I can apply filters to?
> 
> Or is it better to just pick a certain seating position to EQ?
> 
> Forgot to mention I had a filter set during measurements to reduce a hum in the system (the hum was caused by the BFD and the filter was at 150hz, -40db and width of 1/60). This is just a temporary measure.



Yep down the bottom of the graph click *average the responses* on the all spl tab, i think you were on the correct tab with the above graphs . You can pick which responses you want to average by unticking the responses you don't want to be included. This placed the average graph amongst the measurements labeled average.


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## gizzykid (Mar 27, 2012)

Thanks for that phillips.

OK so I have averaged the responses at the corner sub position and have shown the average response before EQ and after automatic EQ below:


Average before EQ:









Average after EQ:








What is this looking like?

I measured these at a random volume and have adjusted the target volume so I can achieve a good curve without having to boost any frequencies excessively. However, I didn't realise you can't apply filters below 20hz and so my graph is off in this range. 
Is this a concern?

Is my target curve right or should I be looking at targeting a House Curve? 
I still dont fully understand how to determine this house curve.

There does not appear to be a huge difference between before and after.
Is it worth using the EQ?



.


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

There are a couple of articles on house curves that you can find linked in my signature. 

The “averaged” curve really doesn’t need any equalizing. Typically what people do is EQ for the “sweet spot.” However, if you want to average I’d throw out the worst curves and write those locations off as a “lost cause,” and average the rest.

Seeing as you have such excellent extension, you don't want to equalize in a way that's going to leave the bottom octave extremely boosted, as shown in your bottom graph.

Feel free to ignore the common advice not to apply any boosted filters. You can read a bit more about that here and  here . The “idea” is that cutting filters conserve headroom, while boosted filters tax headroom, but think about it: In the bottom graph you’ve cut everything severely. This means your sub is now going to be out of balanced compared to the main speakers – i.e., too quiet. So you’re going to have to turn your sub back up to compensate, but look at that honkin’ boost you now have below 20 Hz. Anyone think _that’s_ not going to chew up a lot of headroom???

Regards, 
Wayne


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## gizzykid (Mar 27, 2012)

Thanks for that response Wayne, good links and info.

I think I will try a flat EQ for a while and see how it sounds. If I don't like how it sounds I will try a house curve.

Definitely makes sense what you say about cutting vs boosting and I can see that leaving that boost below 20hz is not great for headroom.

I have re-eq'd to try to bring the rest of the response in line with the below 20hz extension.

The graphs are below. 

Average response after EQ:









Sweet spot before EQ:









Sweet spot after EQ:









I wonder if I have now gone too far the other way.
Am I now boosting too much?


.


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

Hey gizzy,

Cutting or boosting is academic. Virtually any EQ is going to place additional demand on both the amp and driver. You have to have headroom to spare going in.

There’s no real reason to apply any equalization above 70 Hz or so, at least not at this time. In this range you also have the main speakers overlapping, and they can have an effect on response. Best to wait and equalize that range after you add the main speakers to the mix.

Regards, 
Wayne


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