# Bass Response problem



## mdelhaj (Aug 16, 2010)

Hi 
Iam facing a challenge on how to solv and work my way around the big acoustic problem in my sweet spot, imagine just by moving the microphone as little as 5-cm either to the left or the right , than the response will change and where i had a dip in the first measurment now i have a peak and where i had a peak i have a dip specailly in the bass range of 40-60HZ and those dip/peak they measure about 8-14DB....5-cm that is even less than the distance from one ear to the another  so as you can see iam not even geting one decent sweet spot for my self  i have tried moving the subwoofer around but it didn,t help, i also tried moving my listening position alittle (as much as my room allow it) but it didn,t help either, Please if u have any hint or advice for me it would be much appreciated! Thanks


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

Some graphs would be helpful. Is it only in the subwoofer range where you’re seeing this problem? 

Regards,
Wayne


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## mdelhaj (Aug 16, 2010)

Hi 
It was only my subwoofer that i was aiming at , but today i did some test on my front speakers and i was seeing the same problem in the bass range at 80HZ and 125HZ , they keep changing from peak to dip and the other way round as soon as i move the mic just about 5-cm.
i took some graph of the subwoofer respone , ignore everything over 80HZ as thise is where my crossover for the sub. please have a look at it, THe yellow curve is the EQ i did to at achieve flat respone as close as possible at the listening postion , the other curves is the result just by moving the mic. 5-cm either left or right, i took also some RTA graph of the sub. the first one is at the sweet spot and the second is just 5-cm away.

Thank!

Hardware:
Pioneer LX-82
XTZ -99 W12 DSP
XTZ Room Analayzer Kit.


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

Well – such is the nature of low frequencies in a small room. The good news is that your ears are more forgiving than the mic is, so I doubt things sound as bad as they look. If you haven’t already, try putting the sub in or near a corner.

Regards,
Wayne


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## lsiberian (Mar 24, 2009)

Yeah I'm definitely in favor of moving the sub around to see if you can get a better response curve overall.


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## mdelhaj (Aug 16, 2010)

To be honest just as soon as i lean my self a little to the left or the right , i can clearly hear those changes in the bass response, the bass will become loose slower and heavier. 
infact the subwoofer is in the front right corner in the room right now , i have treid moving it around in the room but it didn,t realy help.
thanks


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## mdelhaj (Aug 16, 2010)

Low bass realy works in such a mysteriuos way, even though it was against my personal believe and against the subwoofer placement recommandation by most pro's and user's , well it turn out to be that the best place for the subwoofer for averaging a flat response over a large arial in my room, is just exaclty right behind the sofa, yes behind the listner's:dontknow: now i can move the microphone not only 5-cm but up to 1-meter either left or right and still get a decent response, in other word the whole sofa now it become more or less a sweetspot, and which's enough for 3 listner . 
have a look at the graph the first one is the curve's with the subwoofer placed in the front of the room right/left corner and middle it was all the same.
The second graph is the curve's with the subwoofer placed in the back of the room just behind the sofa.
The yellow curve is the sweetspot and the other 3 curve's is around the sweetspot

i have the low cut filter at 20HZ i will do some more tweaking down there so maybe i get alittle more spl deep down.


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## lsiberian (Mar 24, 2009)

It's not surprising to me. Every room is different and general guidelines aren't as good as doing the old fashioned crawl test.


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

I’d be interested to see what kind of measurements you get without the bass filter off, but it looks like you are sacrificing extension to 25 Hz or lower for “even” response that bottoms out at 33 Hz or even higher. Not sure I would find that acceptable, personally speaking.

There’s no reason to fret about what you get from mic movements of 5 cm. The distance between your two ears maybe, but 5 cm? Keep in mind that the mic doesn’t “hear” the way the your ears do. If you indeed get different response at different mic increments where you’ll be sitting, what you’re going to hear is an average of them. 

There’s no need to go overboard with all this. A single measurement at each of the seating locations on the couch is sufficient. Just make sure the mic is sufficiently away from boundaries, such as the back of the sofa itself.

BTW, what mic are you using?

Regards,
Wayne


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## mdelhaj (Aug 16, 2010)

Hi Wayne
Iam using XTZ Room Analyzer Microphone togther with the software bundle that came with it.
i have just been trying to tweak the bottom bass alittle bit , i tried removing the filters at 20-hz and make a small boost but it didn,t make much differnt's it seems the sub is bottoming around 30-hz, and i know thise sub. can go down flat to about 16-hz in sealed mode and placed in the front corner....so now iam confuse again , which one to go with , have it in the front of the room and get more bass extention or in the back of the room and get better bass averaging....


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## fitzwaddle (Aug 25, 2010)

(perhaps too late, but I'll post anyway)

What direction was the mic facing, towards the speakers? Might want to point it straight up, to keep directionality or the mic / orientation towards the speakers out of the equation.


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