# 135 bass null when both speakers play together?



## Ellisdj (Mar 16, 2012)

Hi Guys

I thought I would see if anyone can shed a bit of light of why they think this might be happening

When I run REW for my front L and front R I have nulls but nothing as drastic as below

However when I run the front L and R together with the sub - I get one big null of 40db @ 130hz.
The overall Null is approx 113 to 157hz mostly 20db or more. 

I am guessing they are cancelling each other out.

They are rear ported speakers if that matters - the sub is crossing over at 90hz and set with a hard knee curve.

All help appreciated


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## Peter Loeser (Aug 11, 2012)

Have you tried changing the location of the speakers or mic and re-doing the measurements? Are you able to post screenshots of your REW graphs? It might help to better understand the issue you're having.

edit: it might also help to know a little more about your equipment. Speakers, sub, receiver/processor and where the crossover is happening (i.e. on the sub itself or within your receiver/processor)


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## Ellisdj (Mar 16, 2012)

Kit 
Monitor Audio GX100 speakers
Sub - BK XLS400 - corner placed
Meridian G61R Processor - Crossover done inside processor

REW Graphs


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## bpape (Sep 14, 2006)

Are you not cutting the speakers off?


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## Ellisdj (Mar 16, 2012)

sorry that was full range.

Like an idiot I didnt measure the individual speakers after being crossed over and eq'd. I was a semi rush job

I have noticed my sub has a huge peak at 127 -150hz. I wondered if that was causing the null by interacting with the speakers?


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## bpape (Sep 14, 2006)

That high up the sub should not even be close to the xover point. I don't think that's it. I think you are getting a phase issue between sub and full range mains. Do you get the null down low with just the sub playing?


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## Ellisdj (Mar 16, 2012)

If you look at pic 3 above thats the sub on its own.
I get a massive peak with the sub only in a very similar range to the null with the 2 main and sub playing


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## bpape (Sep 14, 2006)

i think if you cut the mains off you'll be fine.


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## Ellisdj (Mar 16, 2012)

The last graph is with the mains cut off - thats with the null still


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## bpape (Sep 14, 2006)

but when you don't run the sub it goes away? Hmmmm. Shouldn't have any impact on it that high.


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## Ellisdj (Mar 16, 2012)

I haven't run the 2 speakers together without the sub to see if the speakers causing the issue

And I havent tried to eq that hump out and see if it effects the reponse.
I will be doing this though... Thanks for the help.


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