Front Wall Treatments

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jtsnead

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Front Wall Treatments
« on: 10 Nov 2017, 04:08 pm »
Looking to improve my small 13' x 15' listening room with back wall treatments, do not know if I should use diffusion or absorption
for best sound, see pics below. How about affordable stuff on Amazon.

https://www.amazon.com/ATS-Acoustic-24x48x2-Inches-Burgundy/dp/B002WLIY4O/ref=pd_ybh_a_6?_encoding=UTF8&psc=1&refRID=YEHS555GRR7XT3KMREB9


Also I have a bulkhead above my left speaker would it help to treat the
ceiling above it I think it messes with center image or my left ear is losing hearing so that the central image shifts to the right.









As you can see I have the old room tunes bass traps in the corners and flat panels traps the side walls
next to speakers, also the corner tunes. Open closet behind my seat. Thanks for any help.


« Last Edit: 22 Nov 2017, 02:44 pm by jtsnead »

Hipper

Re: Back Wall Treatments
« Reply #1 on: 11 Nov 2017, 11:24 am »
You can test if it's your ears that are causing issues by either facing the back wall and hearing if you still have left-right problems, or by playing test tones on headphones - or of course by going to a hearing specialist!

As for cheaper panels at Amazon, the price difference of these and a similar product at GIK is not far off:

http://www.gikacoustics.com/product/gik-acoustics-spot-panel/

and with GIK they give you test results - click 'Spot Panel Test Results' near the bottom of the page.

GIK can also offer advice. I've bought from them and they provide a good service.

Another option for advice and sales is RealTraps:

http://realtraps.com/

My (limited) experience in a small room (mine is 14' x 13') is that diffusion does not work because the distances are too small. I used GIK Q7d diffusers (perhaps other types behave differently) and when I put them on the side wall I could hear them and didn't like it. Good advice and experimentation are needed.

Concerning the bulkhead to your ceiling, it would surely affect the balance of the bass but how it affects higher frequencies depends on the sound distribution from your mid and high range drivers. The speaker makers could advise on that.

For solutions you could try moving the right speaker slightly leftwards to see if you can balance the image. Or, more radically, turn the set up round so the speakers are on the wall underneath the bulkhead - I assume it runs along the whole wall. Or lower the rest of the ceiling!

You might also try different speaker and listening positions. I use this - 'The Thirds' - and have got it to work well for me now:

http://www.barrydiamentaudio.com/monitoring.htm


JLM

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Re: Back Wall Treatments
« Reply #2 on: 11 Nov 2017, 11:56 am »
First, you have a nicely sized/shaped room, a huge plus.  Unbelievable how many heavily invest in horrible rooms.  And nice chair (similar to mine).

Second, is the room well acoustically isolated?  Suggest insulated staggered stud walls, lined/insulated ductwork, insulated exterior door with weather seals.

Third, what is your compliant?  How can we help you if we don't know what the problem is?  Have you taken measurements?

Fourth, play around with layout.  Suggest visiting http://www.cardas.com/room_setup_main.php as a start.  I do near-field in a Cardas Golden Cuboid and consider it very successful for 'taking the room out of the equation'.  In fact my six GIK 242 panels are all but useless here, but very effective elsewhere.  In your case the chair would be pulled into the middle of the room, helping greatly to reduce any back wall effects.

Fifth, read Floyd O'Toole's "Sound Reproduction" to learn about room acoustics.  He worked for decades at the Canadian Research Council and Harmon International and is a recognized expert in the field.

Sixth, replace the rack with something much smaller/lower, to allow the soundstage to fill in.  It's made a huge improvement here.

Seventh, replace the MTM speakers as you're getting phase errors from the off-center midrange drivers relative to the listening spot.

Eighth, forget about 99% of pre-made treatments (ineffective).  GIK is the exception in my experience.  Realize that diffusion requires acoustically opaque/non-absorbing materials and geometry that supports the laws of physics (a variety of depths), and that 99% can only be effective down to 1100 Hz.  The best DIY one I've seen is here: http://www.pmerecords.com/Diffusor.cfm

Ninth, only add DSP as a last step and use it judiciously, noting that narrow 30 dB dips can't be heard but flattened out would cause the amp to output 1,000 times the wattage, thus clipping and blowing out drivers.

jk@home

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Re: Back Wall Treatments
« Reply #3 on: 12 Nov 2017, 03:52 pm »
Wow, that's a lot of physical media you got there. Looks like you have a bookcase in the back closet opening? Is there space behind that? You could make the closet as a media storage "pantry", and use doors to close off the opening. Then mount absorption panels on the sections of the doors, and the wall next to the opening. The doors may even have to be mounted in a non-standard way, for the panels to clear when the doors are open. My motto is if there is a will there is a way. I have closets on the front wall, and built QRD diffusers on wheeled stands, placed in front of the doors, to make it work. :D

Certain diffusers will work nearfield, not QRDs, but polycylindrical diffusers may. But I found in my 12 x 15 room, if the poly diffuser is in the reflect free zone, I would get some unwanted glare. I now have diy BAD curved panels in the back wall corners, over corner bass traps, but out of the RFZ, that only add a touch of reflection and restored highs into the room.  The center of the back wall is a desk/bookcase unit, with diy a 4" absorption panel built in to the bookcase, directly behind the head/seat position.

The ATS stuff isn't bad, I am assuming they are using Owens Corning 703 for filler. When I built my diy panels (also with OC 703), I used their burlap as a covering. Not fancy (aka GOM), but nice enough, kinda crafty looking. But I would go for at least 4" thick panels, 6" if also using as bass traps. I agree you will get more support from GIK, so go there unless you need to buy from Amazon for other reasons, or you want to go diy for custom sizes.

Oh yeah and about that media. You could rip all your CDs to flac files and use a streamer and probably gain enough wall space to add "opposite wall" side absorption. Nowadays I use flac and Spotify premium, no physical media in sight.

jtsnead

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Re: Back Wall Treatments
« Reply #4 on: 12 Nov 2017, 03:57 pm »
Thanks for the responces probably should of said front wall meaning behind the speakers

jk@home

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Re: Back Wall Treatments
« Reply #5 on: 12 Nov 2017, 04:05 pm »
In that size room you could do (more) absorption or diffusers on the front wall, as it is all about distances and the speed of sound. Depending on how far the speakers and chair are located from the front wall. Set it up using a mirror. And more bass trapping always helps, can't have enough of that.

http://arqen.com/acoustics-101/reflection-free-zone/

I use QRDs across the front walls, so that I can sometimes substitute my monitors for a pair of small Maggies. Distance from the back of the speaker to the front wall/QRD, then back to the front of the speaker is around 9 feet.




JLM

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Re: Back Wall Treatments
« Reply #6 on: 15 Nov 2017, 01:30 pm »
Again, what is your sonic compliant(s) and have you done any measurements?

It appears from your existing treatments that you're trying to address bass boom.  Do they help?  Have you tried removing them to hear if they do help?

I see no first reflection treatments on the front walls and the side wall panel that is visible is apparently missing the reflection point.  I would expect lots of side wall reflections with the speakers being close to side walls and minimal toe in. 

With a single listening location this would be a good application for DSP. 

optimationman

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Re: Back Wall Treatments
« Reply #7 on: 21 Nov 2017, 10:38 pm »
I too have a small room and a right ear deficiency problem.  If it is not you ear, I would speculate reflection issues.  As a starting point, get some 3 inch batting material and make a panel and place it on the right hand wall at the first reflection point.  I have to agree with JLM, as the sound stage localizing is due to mid and high freq content.  That may move the stage back toward the middle and give a sample of steps to be taken.

optimationman

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Re: Back Wall Treatments
« Reply #8 on: 21 Nov 2017, 10:57 pm »
Also, it looks as though the sitting position is not in the physical center or the acoustic center due to the opening around the door.  I would move the chair forward ahead of the record shelf front edges(left  and right), and/or blank off the shelf/wall behind the chair as suggested by someone else with absorption.  Although subtle, the asymmetrical issue may contribute to the shift.  It is surprising how the sound stage can be distorted but recovered with some attention to detail.

mresseguie

Re: Back Wall Treatments
« Reply #9 on: 22 Nov 2017, 10:20 am »
jtsnead,

I am so envious of your listening room.  :thumb:

Sorry. I have no helpful suggestions.
« Last Edit: 22 Nov 2017, 02:39 pm by mresseguie »

jtsnead

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Re: Back Wall Treatments
« Reply #10 on: 22 Nov 2017, 02:43 pm »
Thanks all, my main issues are the shifting of the sound stage and trying to get the best depth of image by installing diffusors or absorption on the front wall behind the speakers.

I do not want to use DSP, do not want or can move my chair. I have looked at GIK website and will explore that further after the holidays. I probably will get new side reflection panels hopefully thinner than the old Michael Green ones I have now and maybe use the same type panels behind the speakers.

I did not think about the opening behind my chair by the door entering the room maybe I will try a thick blanket or something since I have to come in and out that way it would have to be movable.

I really need to clean up all the stuff on the floor lol

Thanks Again, I appreciate the all the suggestions

Shakeydeal

Re: Front Wall Treatments
« Reply #11 on: 22 Nov 2017, 04:03 pm »
Quote
narrow 30 dB dips can't be heard but flattened out would cause the amp to output 1,000 times the wattage, thus clipping and blowing out drivers.

I'm not sure I read that right. Or did you mean something else? I surely hope so.............. :duh:


Shakey

JLM

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Re: Front Wall Treatments
« Reply #12 on: 22 Nov 2017, 05:54 pm »
I'm not sure I read that right. Or did you mean something else? I surely hope so.............. :duh:


Shakey

Yep, that's right.  Every 10 dB = a 10 fold wattage increase.  So 30 dB = 10 x 10 x 10 times the wattage.  'Smart' DSP units ignore those narrow (frequency wise, such as a 50-55 Hz) dips to avoid needless demands on your amp that can easily cause it to clip and therefore send a nasty distorted signal to your speakers (which speakers don't tolerate very well).