[ccomplete]

Curious what others with OB speakers are doing for treatment at the front wall first reflection point. Absorb, diffuse, none?

I’m getting my new room in order with my Super Vs, I have about 6 ft behind the speakers and without absorption at this point it’s a tad peaky and harsh at certain frequencies but either absorption or diffusion completely kills the depth of the soundstage it seems.. everything comes forward between the speakers.  I have diffusion in the center between speakers and bass traps and diffusion in the corners. My first reflection point lands right between these panels and I’m finding it best with nothing there and just deal with the bit of peaking.

What’s everyone else doing?

[BobM]

I saw these diffusers made from various sized wooden dowels at some audio show. I think it was made by some buddist monks because it cost the GDP of Tajikistan to buy them. So I made my own for about $100. Placed on the wall where the back wave comes out and they do the job nicely. For open baffle dipoles you want reflection on that wall and absorption on the wall behind where you sit. Other way round for typical cone speakers.

[mlundy57]

I use absorption in the front corners and on the back wall behind the listening position and diffusion on the front wall between the speakers and at the first reflection points. I also have carpet and a carpet pad on the floor.

Just because that’s what I have in my room doesn’t mean it is right for you in your room. You might want to ask GIK Acoustics (they also have a circle here).

[ccomplete]

Oh I wasn’t necessarily asking what to do, I have tons of panels to play around with and experiment with the room response I was just curious what other people were doing. I’ve never had the speakers out in the room this far and was surprised when the depth collapsed by putting diffusion at the first reflection point on front wall. Aside from that my best setup so far basically falls in line with what you’ve both said. Diffusion on front and pads on the back and ceiling with a combo of both in the corners and side walls. It’s just the first reflection point on the front that surprised me - went from huge depth to 2 dimensional. Same with toe in.. toed in with tweeters meeting the listening position shows the best measurements but the depth is gone, I assume because the rear is aimed at my corner bass traps at that point.. tweeters hitting back wall directly behind listening position reveals a deep soundstage and sounds drastically better and lets the speakers disappear. I’ve never had such huge changes with toe in or a single panel movement before and thought I’d start a conversation about it      

Those dowel diffusers look awesome!

[SoCalWJS]

If you already have the panels - Experiment!

If it sounds better w/o treatment, don't use them.

If you have (or have access to) EQ measurement tools, try them and see what you get. I personally have a variety that I use in room. GIK Tri traps in the front corners. A combo of GIK Impression Absorper/diffusors and PI Audio Diffusors on the front wall behind and between the speakers. GIK Absorption at the first side reflection points, and GIK Diffusors at the 2nd reflection point on the sidewalls. I've moved them around a LOT and taken measurements with OmniMic & REW. This seems to be the best balance of measurements and my own perception.

[emailtim]

I saw these diffusers made from various sized wooden dowels at some audio show. I think it was made by some buddist monks because it cost the GDP of Tajikistan to buy them. So I made my own for about $100. Placed on the wall where the back wave comes out and they do the job nicely. For open baffle dipoles you want reflection on that wall and absorption on the wall behind where you sit. Other way round for typical cone speakers.

The Acoustic Grove System is very cool and have always wondered about them.  They supposedly model them after a forest according to their writeups.  Unfortunately, thick wood dowels are not cheap anymore for DIY unless you turn your own out of cheaper wood.

https://www.noe.co.jp/en/business/own-products/ags/lineup/ankh-1.html

[Radarman]

  I wonder how much reflection your getting off that rack of equipment in the middle? Ever tried it without that rack?  I have Magnepan MGIIIa's that are 42" out from the highly  treated wall behind them with nothing between them but air.  Soundstage is very deep and open sounding. Listening position is far away from the wall behind me. I want to hear just what comes off the speakers without the reflection off the wall behind them or me. My amps are located behind the speakers low to the floor.
 

[twitch54]

to the Op, just so you know the 'first point of reflection' is the point along the side wall between your listening position and the speakers. With respect to di-poles and the wall behind them that is known as 'rear wave'. To that point and given your 6' spacing I agree diffusion of the rear wave is the way to go. When distance get under 3-4' absorption is quite often needed as well

[emailtim]

... just so you know the 'first point of reflection' is the point along the side wall between your listening position and the speakers. ...

FWIW, there are a few more 1st reflections points including the front wall, floor and ceiling bounces which are not pictured here.



This one depicts the ceiling and front wall bounce, but not the floor bounce.



Here is an example of floor bounce.  @3dB at 150Hz with an 8 foot ceiling.

[twitch54]

FWIW, there are a few more 1st reflections points including the front wall, floor and ceiling bounces which are not pictured here.

True, good points ! I just wanted to clarify that the back wall was not one of them and when one is dealing with di-poles the side wall locations are the most prominent.

[HAL]

Diffusion on the front wall and absorption on side walls reflection points with diffusion on the rear wall.

[emailtim]

...I just wanted to clarify that the back wall was not one of them ...

The back wall is a first reflection by definition.

As for the side-walls, it all depends on the room.  If you have a wide/shallow room, then no, the front and back walls are the major issues.  If you have a narrow/deep room then the converse is true.  There are a lot of factors that come into play including distance of speakers from surfaces, length/width/height ratios, symmetry, [non-]parallel surfaces, windows, partial walls, openings in walls, building materials, etc., etc., etc.  A basement with poured cement/rock walls has different issues than a stud and drywall room than a room with floor to ceiling glass windows.

If you have your seating against the back wall, diffusion won't help because diffusion needs distance to work.  Rule of thumb is 1 foot of space for each inch depth of the diffusion wells.  You have to take everything into account, one rule does not apply to all venues.

My room has 3 different back wall depths which causes asymmetry problems.

[emailtim]

... when one is dealing with di-poles the side wall locations are the most prominent.

FWIW, strong reflections arriving within the first 20ms (irrespective of which room boundary) after the of the arrival of the direct sound are perceived by the brain as part of the original signal and not as echos.  Thus, they "smear" the original sound (constructive, destructive, latent combination of the 2). 

Another rule of thumb that I have seen bandied about is from the following article, "Spikes within 0 (the initial transient) out to 20-40ms or so should be down by 10-20dB."

Sound travels @ 1,129 feet/second or @ 13.5 inches/ms.

https://www.gikacoustics.com/unpacking-etc-time-domain-measurements-early-reflections/

[opnly bafld]

FWIW, strong reflections arriving within the first 20ms (irrespective of which room boundary) after the of the arrival of the direct sound are perceived by the brain as part of the original signal and not as echos.  Thus, they "smear" the original sound (constructive, destructive, latent combination of the 2). 

Another rule of thumb that I have seen bandied about is from the following article, "Spikes within 0 (the initial transient) out to 20-40ms or so should be down by 10-20dB."

Sound travels @ 1,129 feet/second or @ 13.5 inches/ms.

https://www.gikacoustics.com/unpacking-etc-time-domain-measurements-early-reflections/

That is not completely correct according to information from other sources, a path length difference of 11' or more is easy for our brains to identify as a reflected sound. IME this is indeed a benefit of OB speakers well away from the front wall even without treatment.

[emailtim]

That is not completely correct according to information from other sources, a path length difference of 11' or more is easy for our brains to identify as a reflected sound. IME this is indeed a benefit of OB speakers well away from the front wall even without treatment.

What source were you referencing ???

"... The "Haas effect" derives from a 1951 paper by Helmut Haas.  ... A single reflection arriving within 5 to 30 ms can be up to 10 dB louder than the direct sound without being perceived as a secondary auditory event (echo).  ..."

https://en.wikipedia.org/wiki/Precedence_effect

[opnly bafld]

Geddes, Toole, Greene, Greisinger.
Greater than 10ms adds to spaciousness.

[Tyson]

I put absorption on which ever wall is closest to the speakers.  And diffusion on which ever wall is farthest from the speakers.

[emailtim]

Geddes, Toole, Greene, Greisinger.
Greater than 10ms adds to spaciousness.

There seems to be some disagreements as referenced in GIK Acoustics link or a difference in goals (accurate reproduction vs flavoring to taste).  Could you please post links to the actual quotes on the specific topic or articles so I can read them ?

The term "adds to spaciousness" can be interpreted as adding "color" not in the original content (e.g. up to 10dB gains) or overlaying the playback venue's signature onto every piece of recorded content.  It also doesn't address the perception of echos threshold.

I would like read specifically what they are saying.  Are they saying accurate reproduction, flavoring to taste or something else.

Thanks much.

[opnly bafld]

I don't have anything bookmarked, probably not too hard to find.

Here is some interesting information; see Acoustics: Cracking the Early/Late Arrival Conundrum
http://jamesromeyn.com/audiokinesis-speaker-design/#philosophy

[emailtim]

I don't have anything bookmarked, probably not too hard to find.

Here is some interesting information; see Acoustics: Cracking the Early/Late Arrival Conundrum
http://jamesromeyn.com/audiokinesis-speaker-design/#philosophy

Thanks for the link.  I gave it a quick read and it comes off as a sales pitch for their "house sound".  Granted, any manufacturer will pick and choose opinions that favorably promote the sales of their products, including room treatment products.

I am trying to use the accurate reproduction of sound as a baseline which is not always the same as personal preferences and house curves which vary and are many. 

When Danny mods speakers and XO's, he appears to aim for a baseline which is a relatively flat frequency response (Danny correct me if I am wrong).  This may or may not be everyone's preferential cup of tea as many people, including Toole who promote a tipped frequency response or some other shape.  REW's default curve is flat in the middle with slopes on each side.  I fall in the flat response camp because I can always tweak it if desired.

This quote seems to support the attempt to reduce early latency smearing.

"... David Greisinger proposes that the less early arriving reflected energy the better.  ..."

Then this quote appears to be a sales pitch of their "house sound" (which appears to add a slight artificial reverb).

"... If we compare sound patterns to light, think of the early arriving, constant-directivity signal as a focused light beam, followed about 10 ms later (11.25 feet path length difference) by a flood lamp with its spectrum modified for certain desirable attributes known to maximize performance. The results are pleasing and addictive.  ..."

They didn't use the term accurate reproduction.

If I want DSP effects (such as reverb, cathedral or stadium effects), I want to be able to selectively enable and disable them at will.  If it is built into a system, it is much harder to revert back to a neutral baseline, not to mention this added delay is on top of the existing playback venue's reflection delays (so now you have delays on the delays).

Again, I would like to read the articles directly from the sound engineer(s), not a vendor's spin on their interpretations.

My 2 cents.