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New RF-7 IIIs; Room Null @ 100 Hz?


JFHSQT
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New RF-7 IIIs delivered yesterday, and I am going to be using them pretty exclusively for home theater. Over the past couple weeks I have demo'd both the RP-6000 and 820F before deciding to move up to the uncompromising performance of the RF-7 IIIs.

 

Thing is, with all 3 of these speakers I have been experiencing a big null at 100Hz, and I am having to set my crossover at 100Hz to avoid it. I have significant subwoofers (2 SB16 Ultras & 2 JL e112s) so lack of powerful bass up through 180 Hz is not a problem. But especially with the RF-7s I know they have great power and drive in that lower bass region between 40-100Hz and I'd like to take advantage of this.

 

I have tried pushing the speakers all the way against the wall to about 24" driver to wall and it has little effect. Because of the side walls and placement of a center console I am pretty limited with moving away from side walls etc. And 24" is about the limit that I can bring them out into the room due to the RC-64 sitting on the center console below the hung TV. 

 

I do have a large leather reclining couch placed 12' in front of the speakers. I have read that a 100Hz wave is 14' and I'm wondering if there are reflections from the placement of this couch that could be causing the problem. I could move the couch either forward or backward by about 1' but I doubt that will make much difference. 

 

The other option could be ceiling panels. I have large GIK panels behind the speakers and at 1st and 2nd reflection points in the room so the only thing left would be "cloud" panels on the ceiling. But that is a great big pain in the *** if it didn't really fix the problem.

 

Final note, I have had both Heresy IIIs (sealed) and Monitor Audio Gold 200s (dual rear ports) in this same position and not had this issue. It only seems to have come up with the larger Klipsch floor standers. 

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    Hard to say based on just a room description, but it could be that floor bounce is an issue.  This may be why you are only experiencing the problem after moving to floor-standers.  I am thinking that 12' distance from couch to speaker, when triangulated by floor bounce to 14', might just equal a null at 100hz at the LP?   Perhaps a thick rug/pad might help?  I know they are a major pain to install, but I found "cloud" type panels on the ceiling to be very beneficial, though I don't know if it would help your 100hz issue.  

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I assume you are using a microphone at the sitting position with REW or something similar.  As a simple test,  move the mic forward and backwards in the room and see if there is a better frequency response to be had.

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43 minutes ago, Tarheel TJ said:

    Hard to say based on just a room description, but it could be that floor bounce is an issue.  This may be why you are only experiencing the problem after moving to floor-standers.  I am thinking that 12' distance from couch to speaker, when triangulated by floor bounce to 14', might just equal a null at 100hz at the LP?   Perhaps a thick rug/pad might help?  I know they are a major pain to install, but I found "cloud" type panels on the ceiling to be very beneficial, though I don't know if it would help your 100hz issue.  

 

Thanks, yes I am thinking floor bounce could be an issue. I have a thick wall to wall shag carpet but I guess it is possible that it could be acting as a reflecting point. 

 

The leather sofa could be a more likely culprit... it is not a null at a listening position BTW it is measured across all of my measurement points when running Anthem Room Correction, which tells me it's not something from the listening position. If the 100Hz wave is bouncing back at 12' and cancelling itself out then there could be the issue. Another thing is I have the problem from both the left and right speakers. 

 

I am going to try a couple things with the sofa today, possibly measuring with a comforter across the back, and also moving it forward by about a foot. 

 

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2 minutes ago, Shiva said:

I assume you are using a microphone at the sitting position with REW or something similar.  As a simple test,  move the mic forward and backwards in the room and see if there is a better frequency response to be had.

 

Unfortunately it is not position dependent, I have this averaged across multiple measurements in ARC and I can measure it in any seating position. Seems to me it would likely be a null from a reflection canceling out the 100Hz wave versus something to do with listening position. 

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On 7/2/2020 at 8:37 AM, JFHSQT said:

 

Unfortunately it is not position dependent, I have this averaged across multiple measurements in ARC and I can measure it in any seating position. Seems to me it would likely be a null from a reflection canceling out the 100Hz wave versus something to do with listening position. 

Room nulls are hard to deal with.  Peaks can be EQ'd down but adding EQ to a null will just eat up amp power.  You might look into bass traps.  The frequency is high enough that you may be able to treat it to a certain extent.

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