Solving acoustics on a 17' x 13'8"x 10' room for two channel

Nuprin

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Jan 9, 2020
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So the attic idea was scratched and now I'm left with having the system in the office room of which the dimensions are 17' x 13'8" x 10'. I have a corner desk, bookcase, area rug chair and of course equipment rack.

First I tried placing the speakers on the 13'8" width wall and it sounded pretty awful. Lots of reverb the only bass was around a 3 foot parameter around the walls so basically nowhere in the seating area. Moving the system to the longer 17' wall and sitting my head about 2.5' from the backwall, it started sounding much better. However, there are some serious bass issues in the 40hz and 80hz-200hz range. Vocals still have too much reverb/RT and some searing high frequency nodes too.

I understand the room needs more diffusion/diffraction but one problem I'm not sure how to solve are the 4 windows and 2 glass French doors. Unfortunately 2 of them are directly behind where the speakers sit, 2 of them on the right side wall. One French glass door is on the left side wall and the other is on the rear wall opposite of the right speaker. Sure, I can place more bookshelves in the room and even add diffusion/diffraction panels on the walls but how do I solve the glass directly behind and to the side of the speakers? Heavy curtains?

Took some measurements and it's not looking great. As always any input is appreciated.
 

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MTB Vince

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Well what are you prepared to do? Substantial floor-to-ceiling bass traps in all 4 corners should help you get a handle on the 200Hz and down modal peaks and nulls. No doubt the proximity of your listening seat to the rear wall and a strong reflection is causing grief as well. A 4'x4'x6-8" deep broadband absorber immediately behind your seat will deal with that. If any of the primary reflection points fall in front of windows, companies like GIK, RealTraps, and ASC offer floor stands which adapt broadband traps for freestanding use rather than being mounted to the wall.
 

sbnx

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Mar 28, 2017
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Looking at your REW data...

On the frequency response graph it will help to better see the data if you apply some smoothing like 1/24 octave. to do this in REW go to the "graph" menu and click 1/24 smoothing.

You have a large peak at 40Hz that is ringing. This will be very hard (if not impossible) to solve with standard absorbers. There is a product that might help with it but it is pricey.

You do have quite a bit of ringing in the 100-200Hz range. This is what is muddying your vocals. As suggested Try putting some trapping in at least one of the corners and it should help this out. One idea here is to use the GIK soffit traps along the ceiling. This way it doesn't take up floor space.

I also see a steady ringing at 120 Hz at about 60dB. Do you hear a hum from coming from your speakers with no music playing? If so then this is likely a ground loop problem. If not then it is something like the ceiling fan.

For the RT60 data: it is too confusing to see everything on the same graph. Just click on the Topt (turn the others off). This is REW's way of calculating RT60. Ideally, you want this number below 0.5 and really more like 0.35. Some absorption will help with this. You also want the Topt graph to be as flat as you can get it. This graph will change rather dramatically as you move your speakers around. But looking at your pictures your room seems to have a lot of reflective surfaces.

Optimizing the listening position and speaker placement can help a lot.
 

Nuprin

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Thanks. Yes I believe there is a ground issue with the Cambridge streamer when I have it connected through my computer to run the program. It does go away when I run coax digital out to the DAC but I will be replacing the streamer in the near future. I have two dedicated 20amp lines run into the room, one for the amp and the other one for the source and preamp so it's probably not the ceiling fan.

You have a large peak at 40Hz that is ringing. This will be very hard (if not impossible) to solve with standard absorbers. There is a product that might help with it but it is pricey.
Would you be talking about the Acoustic Fields Carbon Absorber? I checked with them and they're recommending a minimum of (8) of their 60"x30" absorbers at $800 a piece and they are 12" deep so it will be hard to implement on opposing front and rear walls.

Still the question is what should I do about the glass French doors. Would you recommend heavy drapes?

Optimizing the listening position and speaker placement can help a lot.
Tried just about every position I could do for two days...but the set up now is currently where it sounds best or least worst.
 

sbnx

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I was not referring to the carbon absorber. I am referring to the "spring trap" by Anthony Grimani of dimension4 MSR acoustics. Here is a link. http://msracoustics.com/ They go in the corner and look highly effective. In fact you might give him a call as I am sure he could help with your room. According to his webpage for a room of your square footage you would need two of them and they are not very big.

The other way to fix the bass problem below 80Hz is with a crossover and a pair of subwoofers. I know it sounds counter intuitive to add subwoofers to fix the bass but as Earl Geddes said "smooth bass is fast bas". At that point you no longer need deep bass trapping. You just need some panels to deal with the resonances above 100Hz with is much easier to do.

For the French doors. Do the doors rattle when closed and you are playing music? If so then you need to secure them so that doesn't happen. Also you only need to treat the doors if it is a reflection point less than 10ms. However, you could deal with two problems at once by handing some 4" panels on the doors. This would help with the bass resonances and kill the reflections.
 

cjf

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Nov 19, 2012
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I see a sub in the one picture and mention of subs in the OP's signature but are they currently being used? Were they being used when the provided measurements were taken?

Not trying to be funny here but if the subs are hooked up and in use the measurements do not appear to really reflect that. At least not like I would expect to see when one or more correctly implemented subs are already in place.

Are you using any room correction today and if so which one? If not, how are you managing the subs (assuming they are being used at all)?

I don't think it would be a bad idea to buy some heavy drapes to cover the window/door areas as a lower cost first step.
 

Nuprin

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The French doors don't rattle, but I just realized I could replace them with solid core doors and then hang whatever works for diffuser/absorber product.

I do have another Submersive HP+ to run as stereo subs or a HP slave (but as two mono subs), however the powered sub has no crossover filter and blending them in with the Micro Ones has been difficult in the room.
 

Nuprin

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Not using any room correction crossovers or software currently. From talking with Acoustic Fields, I need serious absorption to fix the 20hz to 200hz of which they recommended their Carbon Panel which is 12" thick covering at least two opposing walls, if not all four - which would be near impossible practically. And that's before anything else to fix any remaining higher frequency issues.

The curve doesn't need to be perfect but damn, it's not close to looking good.
 

MTB Vince

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I do have another Submersive HP+ to run as stereo subs or a HP slave (but as two mono subs), however the powered sub has no crossover filter and blending them in with the Micro Ones has been difficult in the room.
You need a JL Audio CR-1 sub crossover @Nuprin. That's what I use to obtain a seamless crossover between my ATC SCM20's and quartet of Submersive HP subs when I have the system configured for stereo playback. And a DSP loudspeaker controller between the subs and the crossover to apply PEQ exclusively to the subwoofer channels. The surgical application of PEQ informed by your Room EQ Wizard measurements will allow you to address the deepest modal resonant peaks which passive room treatment has a tough time with.
 
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Nuprin

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You need a JL Audio CR-1 sub crossover @Nuprin. That's what I use to obtain a seamless crossover between my ATC SCM20's and quartet of Submersive HP subs when I have the system configured for stereo playback. And a DSP loudspeaker controller between the subs and the crossover to apply PEQ exclusively to the subwoofer channels. The surgical application of PEQ informed by your Room EQ Wizard measurements will allow you to address the deepest modal resonant peaks which passive room treatment has a tough time with.
I used to have all three subs in room that did both 2 channel and HT, but now they are in separate rooms. In my previous room odd room, for some reason they blended very well in two channel use and I couldn't justify a crossover to fix some minor issues.

Talking to the acoustics vendors, they make it sound like all or most issues can be solved with treatment but you're right, the crossover would help. Or I need to change from the idea of a sat/sub system to a full range speaker, possibly ones with built in subs/bass management. Something like MM2 or MM3 but that's a serious jump in cost and not sure how that would do in a room that's 17'x13'8"x10'.
 

StreamFidelity

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I think your room is very beautiful. But I notice a few things spontaneously. Behind you are several screens that reflect the sound unevenly. Put a blanket over it. The carpet is asymmetrical to the listening position. In my experience, strict symmetry is very helpful for coherence and 3D sound.

Did you use a calibrated microphone and the calibration file? Otherwise you measure the inaccuracies of the microphone. Was the microphone centered exactly between the speakers?

In my experience, the perfect integration of subs is a science in itself. This often creates more problems than it solves. A simple stereo configuration is the solution for me. Maybe it's better to use floorstanding speakers that can bass.

I use Acourate's digital room correction for my bass problems. At the same time, the phase and step response are adjusted to the acoustic ideal. The sound is great. You can handle computers. Using convolution in Roon, for example, is inexpensive.
 
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Al M.

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I used to have all three subs in room that did both 2 channel and HT, but now they are in separate rooms. In my previous room odd room, for some reason they blended very well in two channel use and I couldn't justify a crossover to fix some minor issues.

Talking to the acoustics vendors, they make it sound like all or most issues can be solved with treatment but you're right, the crossover would help. Or I need to change from the idea of a sat/sub system to a full range speaker, possibly ones with built in subs/bass management. Something like MM2 or MM3 but that's a serious jump in cost and not sure how that would do in a room that's 17'x13'8"x10'.

"Full range" speakers (I put that in quotes because they are rarely full range) can have their own bass integration issues, especially in a problematic room like yours. They might work perfectly well, but they also might give you unexpected additional headaches. Those may or may not be solved by experimenting with placement in the room. I would make sure, if you want such speakers, that you can audition them in your room prior to purchase.
 

Cellcbern

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So the attic idea was scratched and now I'm left with having the system in the office room of which the dimensions are 17' x 13'8" x 10'. I have a corner desk, bookcase, area rug chair and of course equipment rack.

First I tried placing the speakers on the 13'8" width wall and it sounded pretty awful. Lots of reverb the only bass was around a 3 foot parameter around the walls so basically nowhere in the seating area. Moving the system to the longer 17' wall and sitting my head about 2.5' from the backwall, it started sounding much better. However, there are some serious bass issues in the 40hz and 80hz-200hz range. Vocals still have too much reverb/RT and some searing high frequency nodes too.

I understand the room needs more diffusion/diffraction but one problem I'm not sure how to solve are the 4 windows and 2 glass French doors. Unfortunately 2 of them are directly behind where the speakers sit, 2 of them on the right side wall. One French glass door is on the left side wall and the other is on the rear wall opposite of the right speaker. Sure, I can place more bookshelves in the room and even add diffusion/diffraction panels on the walls but how do I solve the glass directly behind and to the side of the speakers? Heavy curtains?

Took some measurements and it's not looking great. As always any input is appreciated.
Looking at your first photo, if that's where the speakers sound best now then the most important step is to reduce/eliminate reflections off the walls behind the speakers by treating the walls between and on either side of the two windows. Moveable acoustic panels on stands can be used directly in front of windows. Do that first
and then look at the side wall first reflection points and other reflective surfaces. Note that it is possible to mount acoustic panels on doors. My wife insisted on sliding "barn doors" with glass at the entry to my dedicated listening room. I hung absorber panels on them which move with the doors because they were at a first reflection point. Also take a look at my forum posts on the ZR Acoustics panels I've been testing. I'm sold on them as a disruptive technology in room acoustics since my ears have confirmed their claims for me. They are relatively expensive but they eliminate reflections and obviate the need for bass traps.
 
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Nuprin

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Did you use a calibrated microphone and the calibration file? Otherwise you measure the inaccuracies of the microphone. Was the microphone centered exactly between the speakers?
Yes, I used a MiniDSP calibrated mic centered where my ears would be seated.
 
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Nuprin

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You need a JL Audio CR-1 sub crossover @Nuprin. That's what I use to obtain a seamless crossover between my ATC SCM20's and quartet of Submersive HP subs when I have the system configured for stereo playback. And a DSP loudspeaker controller between the subs and the crossover to apply PEQ exclusively to the subwoofer channels. The surgical application of PEQ informed by your Room EQ Wizard measurements will allow you to address the deepest modal resonant peaks which passive room treatment has a tough time with.
What about using something like the MiniDSP SHD with DIRAC Live and using it to actively crossover the speakers and sub? Please correct me if I'm wrong but I think this is possible from what I'm seeing? - Running my source/streamer(I like using Airplay for Apply Music and Qobuz for casual listening and when searching for new content) to the SHD, have DIRAC do it's correction, then to my own DAC, onto the preamp, amp and crossover the speakers/powered sub?

It can be limited to filtering only certain frequency ranges so I could, say limit DIRAC to all frequencies below 500hz if I don't like what it does the the rest of the spectrum as my major issues are below 200hz.


I've never entertained the idea of using something like DIRAC for a 2 channel system since it works well for the HT in the family room with the Lexicon but I wonder if it will make the system sound worse in certain areas while "correcting" my bass issues. Then the question is how much room acoustic treatment do I need and is it a combination of both "active" and "passive" room correction to achieve the best results?
 

MTB Vince

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If you intend to place the DSP processor between your digital source and DAC, and use it to perform DEQ, no problem @Nuprin. But if you intend to use a DSP processor to perform x-over duties as well as modal room correction, that is an entirely different can of worms that tends to treat analog sources less well.

In my experience running the full range signal of my phonostage through an analog-to-digital conversion --> performing DSP processing --> and then digital-to-analog conversion tends to throw away much of the sonic benefits which keen vinyl spinners most highly prize. I found this to be the case even with high-end audiophile electronics from digital specialist brands, Meridian and DEQX. Spaciousness and transparency from analog sources took a major hit. I pretty much gave up on vinyl playback during the decade period in which my big-rig was based upon a Meridian pre-pro and their DSP based active loudspeakers. My brief subsequent experience with the DEQX PreMate wasn't meaningfully different and I sold it on rapidly. Digital source material sounded great but the key benefits of high-end vinyl replay failed to translate through the digital signal chain.

This is why for stereo listening today, I've chosen a very high quality analog subwoofer crossover and then only apply ADC-->DSP PEQ and delay-->DAC to the bandwidth limited sub-80Hz low-pass subwoofer output. Sub bass frequencies appear to be largely immune to the negative sonic consequences of the additional ADC/DSP/DAC cycle. Vinyl replay is a joy once again and despite the additional effort compared to CD, LPs once again account for at least half my listening sessions.
 
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Nuprin

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Just found this from from a previous post by Cellbern

And found this video. Would love to hear opinions on if you guys think this technology really works.

 

Nuprin

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Jan 9, 2020
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Vince,

Vinyl for me now is not a priority as I don't have a great set-up or anything. The analog playback components are now over 20 years old including a $200 phono stage. It's a path that I may explore further when I have the time and patience for it. I hate to admit it but the convenience and access to practically any music I want from streaming services and digital files on my computer are just too easy so that's why I was looking into DSP correction.
 

Dennis Foley

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Sep 11, 2019
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www.acousticfields.com
So the attic idea was scratched and now I'm left with having the system in the office room of which the dimensions are 17' x 13'8" x 10'. I have a corner desk, bookcase, area rug chair and of course equipment rack.

First I tried placing the speakers on the 13'8" width wall and it sounded pretty awful. Lots of reverb the only bass was around a 3 foot parameter around the walls so basically nowhere in the seating area. Moving the system to the longer 17' wall and sitting my head about 2.5' from the backwall, it started sounding much better. However, there are some serious bass issues in the 40hz and 80hz-200hz range. Vocals still have too much reverb/RT and some searing high frequency nodes too.

I understand the room needs more diffusion/diffraction but one problem I'm not sure how to solve are the 4 windows and 2 glass French doors. Unfortunately 2 of them are directly behind where the speakers sit, 2 of them on the right side wall. One French glass door is on the left side wall and the other is on the rear wall opposite of the right speaker. Sure, I can place more bookshelves in the room and even add diffusion/diffraction panels on the walls but how do I solve the glass directly behind and to the side of the speakers? Heavy curtains?

Took some measurements and it's not looking great. As always any input is appreciated.
In small room acoustics, you must treat the low frequency issues first and foremost. The fundamental low frequency issues produce harmonics that extend through the middle and higher range frequencies. If you treat the fundamentals, you minimize the impact at the middle and high frequencies. In a room this size and volume, you have major treatment issues starting at 33 Hz. and going through 225 Hz. Moving speakers around in a room this size and usage will not have the effect you desire. Treat the room fist and then set up within the treated room.
 

Addicted to hifi

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In small room acoustics, you must treat the low frequency issues first and foremost. The fundamental low frequency issues produce harmonics that extend through the middle and higher range frequencies. If you treat the fundamentals, you minimize the impact at the middle and high frequencies. In a room this size and volume, you have major treatment issues starting at 33 Hz. and going through 225 Hz. Moving speakers around in a room this size and usage will not have the effect you desire. Treat the room fist and then set up within the treated room.
Agree with you on this one.
 

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