# EQ for a small dip help



## dondino (Feb 12, 2010)

Hi guys, check out my REW below. I have a 38hz dip there and would like to know if my bfd could fix that if I nudge it up with a filter. Is this considered a null where no amount of EQ will help it?

I really like the placement of where everything is now and would like to NOT move the speakers and/or listening position if this could be fixed with EQ. If not, I'll move things around some more.

One other noobish question: I have my xover set to 100hz on all channels. When I do my sweeps, I use the "Stereo" setting on my receiver so the sub plays with my mains. Am I supposed to be doing this or should I be disconnecting my mains?

Thanks! :bigsmile:


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## wackii (Jul 13, 2006)

You should measure the sub only first. Then measure the mains. Then measure the sub + mains to see how they are interact. You should run the sweep from 15hz to 200hz to have a better idea of how your sub and mains perform. That dip there looks like a null to me. Dont take my words for it, let the experts here chim in. Your FR looks pretty good as is. It sounds like you love to tweak things for perfection  Since you already have the bfd, give it a try. I wouldn't boost more than 6db. Good luck.

Al,

Regarding your question, using "Stereo" mode is the correct way for running REW. You're fine.


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## recruit (May 9, 2009)

I would be wary of boosting levels below 50hz especially if it is a null, as it will not improve much on it, have you tried adjusting the phase?


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## glaufman (Nov 25, 2007)

Wayne has a bit more experience with EQ than I do, and says the percentage of times boosting a dip actually helps is overwhelmingly in favor of giving it a try, despite most of the theory says. So, especially if you have the BFD already, give it a try. 
Do you have a regular rectangular room? You could calculate where the modes should be and see if on corresponds to a fundamental that would have a harmonic at 38Hz. 
That being said, even if EQ would help the dip, I'm a proponent of placement first, EQ last...


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## lsiberian (Mar 24, 2009)

It wouldn't hurt to try, but don't get carried away.


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

dondino said:


> I have a 38hz dip there and would like to know if my bfd could fix that if I nudge it up with a filter. Is this considered a null where no amount of EQ will help it?


 Usually an unequalizable null is characterized by being deep and narrow. Tough call with yours, it doesn’t seem to quite fit the bill. You probably won’t know unless you give it a try.

That said, it’s hard to make a definitive judgment call with your graph. It’s just too “pretty,” like some smoothing has been applied. If that’s the case, it’d be easier to tell something with a non-smoothed graph. Typically smoothing is only used for full-range graphs.

Regards,
Wayne


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## dondino (Feb 12, 2010)

Wayne A. Pflughaupt said:


> Usually an unequalizable null is characterized by being deep and narrow. Tough call with yours, it doesn’t seem to quite fit the bill. You probably won’t know unless you give it a try.
> 
> That said, it’s hard to make a definitive judgment call with your graph. It’s just too “pretty,” like some smoothing has been applied. If that’s the case, it’d be easier to tell something with a non-smoothed graph. Typically smoothing is only used for full-range graphs.
> 
> ...


No sir, no smoothing. That is with BFD EQ however as adjusted by REW. What I was stuck with was that dip. I wasn't sure if I would be able to EQ it up. I know I *can* I just wanted to know if it would make a difference. I guess I'll add another filter to bump it up a few and give it a try.

Btw, that FR is from a pair of Epik Empires stacked in the sweet spot corner of our LP. I'm especially happy with the REW from a corner placement. I can get almost a perfectly flat response by seperating them but the placement just sucked where I got the best REW FR. This was a good compromise except having to deal with that dip.

Thanks for all the help guys!

Don


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## gperkins_1973 (Aug 25, 2008)

Just thought I would mention that I had a null at 33hz. I did some spl measurements from the listening position and without my BFD filter I applied to boost it, it was saying 71db but when I turned the filter for that frequency back on it read almost the same as 30 and 40hz so I guess for me it worked. I did however boost by 8db to get it there but has made no difference at all to my performance as I watched Transformers 2 at almost reference today with no issues at all and I was only getting 5 bfd green lights. I still think I am running with input voltage problems though. It was funny though I have to say. The level of bass coming from my two FI Q18's was yum yum.

Basically have you tried boosting to see if makes a difference.

cheers

Graham


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## dondino (Feb 12, 2010)

gperkins_1973 said:


> Just thought I would mention that I had a null at 33hz. I did some spl measurements from the listening position and without my BFD filter I applied to boost it, it was saying 71db but when I turned the filter for that frequency back on it read almost the same as 30 and 40hz so I guess for me it worked. I did however boost by 8db to get it there but has made no difference at all to my performance as I watched Transformers 2 at almost reference today with no issues at all and I was only getting 5 bfd green lights. I still think I am running with input voltage problems though. It was funny though I have to say. The level of bass coming from my two FI Q18's was yum yum.
> 
> Basically have you tried boosting to see if makes a difference.
> 
> ...


I nudged it up with a bandwidth of 4 about +6 gain and it seemed to cut the dip in half. I'm happy with that. 

Thanks all!


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## glaufman (Nov 25, 2007)

Is that an audible improvement?


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## dondino (Feb 12, 2010)

glaufman said:


> Is that an audible improvement?


I have no idea! :rofl:

It was fine probably before I EQ'd it. It was nagging me that it was there though. :yikes:


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