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Room Treatment: Diffusion

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Did you state somewhere what loudspeakers you're using?  The vertical/horizontal thing could be affected by that, especially if using a K-400-series midrange horn or something like that.

 

Additionally, there is usually nothing on the ceiling so diverting reflections vertically via diffusion will usually give you a lot more apparent change (that is, reflections back to the listening positions) than diverting the sound horizontally.  There is usually a lot more diffusion horizontally already present in the room.

 

Chris

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Did you state somewhere what loudspeakers you're using? 

 

Totally upgraded-modded KLF-30's.

 

 

 

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Yeah, adding the diffusors on the front wall was a surprise in added clarity, bigger soundstage etc.....but when I put the diffusors on the back wall it took all that away.

 

Removed the diffusors from the back wall and it all came back. It's really got me anxious to check out additional diffusion on the front wall.

 

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We used 2" of Roxul on our whole front wall, and we also got more clarity, and bigger soundstage. As far as the diffusers on the rear wall... I was always told you need 5' minimum from the diffuser to the seating. I do know that in my last room, treating the room made a bigger difference than buying more expensive equipment, and allowed me to hear things I never heard before from movies, and music.

 

 

 

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Exactly what I found when we treated our room! No need to spend more money on the newest amps...you just moved up several levels in audio by treating the room vs buying the latest gear, and not sounding as good as treated room with less expensive gear.

Well, after much experimenting and 16 diffusion panels later......I found the proper balance between using absorption and diffusion in my room.

Although my front stage is 90% diffusion, there is still some absorption behind the speakers at mid-tweet level. This has proven to be VERY beneficial. Even though the difference with/without it is very audible, I went back and forth several times. The absorption behind the mids-tweets adds focus to the imaging and most of all adds warmth to the sound. This is big in my book and have to believe any Klipsch would benefit from it.

The rear wall is 90% absorption (it is directly behind the listening position) and 10% diffusion. More absorption than diffusion (or nothing at all) on the back wall puts more attention...or focus...on the front stage. If I put more diffusion on the back wall, the sound gets bigger....more room filling....BUT robs overall sound quality. It's not quite as 'right'. I went back and forth on this and much preferred predominantly having absorption on the back wall with a minimal amount of diffusion up high.

Lately, I've been jammin my solid state equipment. Since I had my tube integrated restored, as good as it sounds I couldn't slightly boost the bass and treble like I normally did before.....until this morning. On my HH Scott 222c I would normally have the bass and treble slightly boosted to about 1:00. So now after all the treatments are in place to my liking, I decided to try the 222c again and I was blown away. The warmth, richness and detail is remarkable. I can honestly say the room treatments took it to another level. I was actually going to sell it because I just found myself listening to my solid state gear pretty much all the time. This tube amp ain't going anywhere. In fact I just ordered another quad of 7189 tubes 15 minutes ago. I've fallen in love with the sound of this amp all over again and it certainly was because of the improvement in the room's acoustics.

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Did you state somewhere what loudspeakers you're using?  The vertical/horizontal thing could be affected by that, especially if using a K-400-series midrange horn or something like that.
 
Additionally, there is usually nothing on the ceiling so diverting reflections vertically via diffusion will usually give you a lot more apparent change (that is, reflections back to the listening positions) than diverting the sound horizontally.  There is usually a lot more diffusion horizontally already present in the room.
 
Chris
Chris, what would you suggest I do with a 32' high boveda ceiling... I am thinking leave it alone since it is curved, and treat the walls below 15' to 20' only.

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Since the distance is 32 feet to the ceiling (57 ms round trip delay), you may not have to do very much.  Only the reflections near the fronts, the surrounds, and just around the listening chairs are important to control.  Directivity of the loudspeakers and absorption of the listening position chairs/furniture will control much of the offending ceiling reflections.

 

Chris

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On ‎10‎/‎6‎/‎2018 at 6:58 AM, SWL said:

More clarity and focus in the midrange and in return a cleaner bass.

 

I like what you have done with the diffusion and absorption panels in your listening room.

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I like what you have done with the diffusion and absorption panels in your listening room.
Thanks!

I highly recommend it and it was fun experimenting. Took a little work as far as the painting went. You gotta put two coats on this polystyrene for it to cover properly. Spray painting would be a breeze but you can only use water based paint otherwise the chemicals eat away at the polystyrene. Painting with a brush inside the channels is a little time consuming (especially when you're working 12 and 13 hour days......yeah, I made some boo boos).

Figuring out a balance between diffusion and absorption was fun and a little challenging. Especially which way to scatter be it horizontally or vertically.

Well worth the time and relatively cheap expense when you look at the big picture. I spent a lot less money this way vs buying a nice new amp, preamp or speakers etc.

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I added bass traps to my front stage... I am not really sure they made ANY improvement, and I tend to think they degraded the mid bass region of the 2-channel set up.

I'm going to listen for a while but something seems to have changed... again with the mid bass region of the LS bass.

I was slightly skeptical before adding them as bass traps have some controversial effects in the modern system.

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10 hours ago, Schu said:

I added bass traps to my front stage... I am not really sure they made ANY improvement, and I tend to think they degraded the mid bass region of the 2-channel set up.

It's difficult to know what you've got without some form of acoustic measurement.  REW does these calculations automatically when you record an upsweep with a calibrated microphone.

 

I have found with Jubs in the corners and center MEH in my room that I need some bass trapping, but not as much as I could get from the two corner-located (i.e., across the corner) bass traps just behind the Jubs on top of the TH subs.  So I moved them slightly toward the center asymmetrically across the corner but still touching the corner walls to squash the air volume entrapped behind each bass trap, thus reducing the volume of air behind them and therefore their effectiveness--to taste.  The resulting reverberation times are shown below (generally look below 300 Hz for the effects of bass traps):

 

Chris A's Listening Room RT60 - 1 Metre Center.jpg

 

I certainly wouldn't remove the traps from my room, but some adjustment as indicated is needed.  Too much trap effectiveness overdoes the midbass absorption, as you have stated.

 

I suppose that having loudspeakers with such good directivity control vs. frequency (down to ~110 Hz) really precludes the need for a room full of bass traps, such as Ethan Winer shows in his listening room with direct-radiating woofers and subwoofers:

 

120real.4.jpg

 

Chris

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thanks chris... My suspicions are confirmed.

 

The death of mid-bass were NOT exaggerated.

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I added bass traps to my front stage... I am not really sure they made ANY improvement, and I tend to think they degraded the mid bass region of the 2-channel set up.
I'm going to listen for a while but something seems to have changed... again with the mid bass region of the LS bass.
I was slightly skeptical before adding them as bass traps have some controversial effects in the modern system.
That's interesting because in the past, adding bass traps on my front wall always degraded the sound in my room as well.

It's also interesting because a couple weeks ago I was just watching a video by an acoustics company (can't remember their name off hand) and the guy was saying that he recommended bass traps to be put on the front wall instead of the back wall because that's where most of the bass 'energy' is. He referred to a couple of Ethan Winers' pics and he had the bass traps on the front wall in the corner where it meets the ceiling. I might have to try that someday but really don't see it happening.....

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'Acoustic Fields' was the name of the company.

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42 minutes ago, SWL said:

the guy was saying that he recommended bass traps to be put on the front wall instead of the back wall because that's where most of the bass 'energy' is.

 

Every room is different, but I have found that bass traps often function best in the far opposite upper corners from the bass speakers.

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Some ranging discussions on this issue of bass trapping with respect to loudspeaker types, room treatments, and mastering practices....

 

If you own Khorns, their midbass polars aren't terribly spectacular due to the dual mouth bass bin phenomenon, causing lobing and a narrowing beam of on-axis acoustic energy.  To a lesser degree, the other horn-loaded bass bins like the Jubilee bass bin and MWMs, etc. have the same issue although it's not nearly as pronounced, while Belle bass bins have the issue at a somewhat higher frequency than 300 Hz due to the two-mouth bass bin issue.  So in these instances, some people might be sensitive to hearing those narrow polars and might have accommodated to the sound of midbass boominess to some degree.  So they might not like the effects of midbass control using bass traps, when the real issue is the narrow midbass polars--which are camouflaged by having a longer reverberation time in-room at those frequencies.

 

However, direct radiating bass bins, like Cornwalls, Heresies, and the balance of the Klipsch home theater and bookshelf product lines will experience the same issue as all other loudspeakers having direct radiating woofers: too much midbass due to the woofers splashing acoustic energy almost equally in a 360 degree azimuth, resulting in too many early reflections below 300 Hz, and the perception of too much "tubbiness" and boomy sound. That's why I believe a lot of people place their loudspeakers away from the room boundaries.  In reality, they should be placing them closer to the room corners and using absorption (including bass traps) and EQ to bring the perception of midbass boominess back down, along with controlling midrange early reflections that affect the stereo imaging. 

 

The La Scala and Belle also have a separate issue of losing horizontal pattern control at about 100 Hz, which then transition the bulk of their bass response to the nearby walls, floor, and ceiling.  If you move these two loudspeakers away from the walls, you disproportionately lose low midbass control (due to the wall mirror images not being close enough to the walls) but you wind up controlling the boominess and midrange imaging issues.  But this only happens because the proper amount of acoustic treatments on the nearby walls is not there to soak up the nearfield early reflections.  Typically in these same instances, the user isn't conscientiously re-EQing the midbass and bass response flat again (unless using "room correction software"),

 

There are some offsetting factors that you will see if you inspect many of your music tracks using Audacity.  A lot of tracks are pre-attenuated in the 100-200 Hz region (usually by 3 dB...half amplitude) to control the typical muddy sound of untreated home-sized listening rooms.  This creates a problem when you actually find recordings that don't pre-attenuate, because they will sound muddy but are actually accurate to the original recording venues.  It also creates a problem for systems that are setup with accurate response in the 100-200 Hz band, and are then over-attenuated by the mastering engineers--these recordings sound thin and somewhat bass shy.  My solution to this is to demaster the recordings to remove that midbass attenuation placed there during mastering (i.e., on the stereo downmix tracks). 

 

Bottom line: virtually all rooms need bass trapping to control 70-300 Hz reverberation times (T20, T30, etc.)--which is below the frequency where typical absorption panels are most effective.,  But due to other issues with placement of loudspeakers and inadequate acoustic room treatments, in-room acoustic issues show up at bass trapping frequencies--and the bass traps get blamed...unfairly.

 

Chris

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1 hour ago, SWL said:

That's interesting because in the past, adding bass traps on my front wall always degraded the sound in my room as well.

It's also interesting because a couple weeks ago I was just watching a video by an acoustics company (can't remember their name off hand) and the guy was saying that he recommended bass traps to be put on the front wall instead of the back wall because that's where most of the bass 'energy' is. He referred to a couple of Ethan Winers' pics and he had the bass traps on the front wall in the corner where it meets the ceiling. I might have to try that someday but really don't see it happening.....

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Bass traps are most effective in room corners but work anywhere.  

I have them in corners, at the junction of floor and front wall, hanging as ceiling clouds, leaning agaist a wall etc.

Placement of thinner absorbers, such as 1" or 2" thick needs to be placed more carefully and in some cases in limited amounts

 

chris aludes to the real key.  its hard to grasp absorbing bass and making it sound better.

bass decays slower in a room and by absorbing the critical midbass region it cleans up how it sounds

down low in HT frequencies the longer decay works fine, but midbass is where clarity improves with absorption

 

if we throw 200 rolls of insulation in your basement we could absorb the midbass in that concrete monster lol

upstairs much better and already treated....why it sounds so dxxx good!

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if we throw 200 rolls of insulation in your basement we could absorb the midbass in that concrete monster lol
upstairs much better and already treated....why it sounds so dxxx good!


Of the eight 2x4 broadband absorption panels I had, six of them got replaced with diffusion. So in the basement they went.....distributed throughout the unfinished concrete dungeon....some in corners, some not. A week or so went by and it kinda slipped my mind that I put them down there. Flicked on the tunes and right away I noticed an improvement in sound quality, then I realized the panels throughout the basement.

This is how observant I am when working a lot of hours LOL.


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On ‎10‎/‎27‎/‎2018 at 12:01 PM, Chris A said:

Bottom line: virtually all rooms need bass trapping to control 70-300 Hz reverberation times (T20, T30, etc.)--which is below the frequency where typical absorption panels are most effective.,  But due to other issues with placement of loudspeakers and inadequate acoustic room treatments, in-room acoustic issues show up at bass trapping frequencies--and the bass traps get blamed...unfairly.

 

Viewing pictures of many installations, I see that most home bass traps are not thick enough to be effective.

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Yes, the bass traps themselves are not thick enough, but used as "bass traps" with an enclosed airspace behind them and the wall, especially when doubled up to two Owens-Corning 703 panel thicknesses per bass trap (as mine are), they perform quite well across two room boundaries with enclosed end--like a Helmholtz resonator without a throat constriction.

 

There are also "tube absorbers" that essentially do the same thing, except that they are conversation pieces, i.e., they take up a lot more floor space and present a much greater visual signature than corner bass traps (IMHO).

 

Chris

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7 hours ago, Chris A said:

There are also "tube absorbers" that essentially do the same thing, except that they are conversation pieces, i.e., they take up a lot more floor space and present a much greater visual signature than corner bass traps (IMHO).

 

Depends on what you mean by "tube absorbers"..? 

 

ASC Tube Traps in their basic form uses sealed chambers to take advantage of the pressure differential between the sound pressure developed in the corner boundary (for example) relative to the internal pressure of the tube trap which absorbs/converts the energy as it is forced through the fiberglass tube.

 

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