# New room, new bass problems...



## NainoKami (Aug 4, 2009)

Hi,

I was wondering if anyone would look at my measurements, and let me know what they think...
The measurements are from my new theatre room, and the room is almost entirely untreated so far... I am planning to add superchunks to the four vertical corners, diffusors at the back, and ofc. first reflection panels.

Do you think the superchunks with a 24" facing will help with my issues? The bass is exactly the same in all listening positions up to 35 Hz, but between 35 Hz and 65 Hz things change... Would I be better off with membrane traps, and if so can you recommend some choices...? By the way, I know the results are bad so far, but remember this is with no treatment (to speak of), and no EQ at all...

I added the measurement data as well as a zip...

Cheers

Results follow:


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## bpape (Sep 14, 2006)

Can you post a little information as to room dimensions, seating locations, and sub placement?

Bryan


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## NainoKami (Aug 4, 2009)

Sure...

Subs are red, and LPs are green... This isn't 100% accurate, but pretty close... The LP is about 4 m from the front wall and about 1.7 from the back wall... the problem seems to get worse if I move the LP forward...

Thanks!


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## bpape (Sep 14, 2006)

Sorry. These eyes are too old. Can't see the dimensions to seated ear position, front of speakers, drivers on subs, room dimensions, etc.

It appears that you're getting some diagonal modal problems based on the symmetry of the seating to the width but the differences in the dips from left seat to right seat. What specifically gets worse if you move the mic forward? Everything, just one seat?

Bryan


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## NainoKami (Aug 4, 2009)

1 foot forward, and the valleys seem deeper... But the main problem area is still 35-60 Hz


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## NainoKami (Aug 4, 2009)

sorry about splitting the posts, but was posting the measurements from the laptop...

Here are some distances with larger type, and a photo of the setup...

Anything else?

I've had the same thought about the diagonal mode... Seems to be the first axial mode of the width...

P.S. the dish washer isn't staying in the theatre...  and the small couch is going somewhere else...


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## NainoKami (Aug 4, 2009)

Just realized... The superchunks I'm planning to make arent 24" facing, but 34" facing...  Should make a difference... I hope!


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## bpape (Sep 14, 2006)

NainoKami said:


> 1 foot forward, and the valleys seem deeper... But the main problem area is still 35-60 Hz



I don't know which is which but different positions now have different responses. Again, kind of pointing toward a diagonal problem which the corner treatments should help with. Tangentials are not all in the corners certainly though.

Bryan


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## SierraMikeBravo (Jul 1, 2007)

Part of the problem I see is that you have numerous cut-outs and openings into the room that lead to adjacent rooms. What happens is that you are taking on some of the modal elements of the differences in the room size as well as modal elements from adjacent rooms. This is one of the reasons it is so difficult to predict odd shaped rooms and openings to other spaces. Try moving the two subs to different locations in the room to see if that makes a difference. Good luck!


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## NainoKami (Aug 4, 2009)

SierraMikeBravo said:


> Part of the problem I see is that you have numerous cut-outs and openings into the room that lead to adjacent rooms. What happens is that you are taking on some of the modal elements of the differences in the room size as well as modal elements from adjacent rooms. This is one of the reasons it is so difficult to predict odd shaped rooms and openings to other spaces. Try moving the two subs to different locations in the room to see if that makes a difference. Good luck!


I see your point, but the openings don't actually go to other rooms and the doors are closed when I use the system. I know they'll still let some energy through, but I think I've narrowed the troublesome mode down to just the first axial width mode of room. If I measure across the room at the LP and adjacent seats it's the 43 Hz fundamental that changes. Actually it's 40 Hz, but I've found that all my calculated modes are a few Hz above the actual ones, but they line up really well otherwise. I think the reason they've shifted is because the walls are made from different materials. (the wall on the right is brickwork, and the rest of the walls are wooden.)

If I measure across the room about 3 feet in front of the LP the 43 Hz (40 Hz actual) axial and 53 Hz (50 Hz actual) tangential that show up. The tangential doesn't actually affect the LP in any significant way as far as I've worked out.

So the question is now. Can my planned superchunks (either 24" facing or more) help with that 40 Hz axial, or do I have to treat other places as well with bass traps (be it broadband or otherwise)? Centre of the sidewall for instance?

Kind regards,
Simon

Thanks for the help so far!


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## NainoKami (Aug 4, 2009)

Now as I look at the results again, it seems the mode IS actually quite close to the calculated 43 Hz, though the tangential at 53 Hz is still shifted a bit down. Have a look and let me know what you think...


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