Jump to content

Home Theater Geeks Talk Acoustics


twk123

Recommended Posts

Thanks for posting the videos.... twk123

Anthony Grimani comments about the need for diffusion and cautions about over absorption were spot on. Over use of absorption as well as misplacement especially with horn type loudspeakers can lead to much worse problems than what one might have began with and often leads to listener fatigue rather quickly.

Also some form of modal control/compensation is a must in the majority of all listening rooms if one wants to experience the full capability of their system.

The equipment marry-go-round that so many find themselves on can be traced back to the lack of attention to the room's acoustical weaknesses and the proper corrective actions often needed.

Seems most listeners are intent on spending their money and time chasing the annoying fly while ignoring the elephant in the room..... :-)

miketn

  • Like 4
Link to comment
Share on other sites

The 20% absorption rule-of-thumb is something that I arrived at independently of this presentation.  But not all reflections and absorption surfaces are created equal--with nearfield reflections of less than 2ms being the most important to control through absorption or placement of loudspeakers. 

 

Corner horns and corner-located loudspeakers usually require some absorption on the walls immediately adjacent to the midrange horn mouths.  Most folks get this one wrong and decide to abandon corner-located placements due to these early midrange reflections, but the wind up losing about 1/2 to one octave of good bass (and correspondingly higher bass distortion) when they move their speakers out onto the floor away from the corners.  PWK wrote on corner placement of loudspeakers fairly extensively, showing the advantages of smoothness and extension of bass by this simple method, but he didn't talk about controlling early midrange reflections very much, which I've found to work almost like magic.

 

The 25% diffusion is also probably around what that I've got (by default) due to room boundary irregularities and other objects in the room, but not the least of which is the length of the room of ~40 feet. But certainly there is a lot of diffusion in the room down to low frequencies as evidenced by in-room measurement waterfall plots with REW.

 

Here is an interesting article in pdf format that I like a lot from Dr. Peter D'Antonio, the originator of the RFZ--the reflection-free zone concept and Reflection-Phase Grating (RPG) and plate resonator designs as well as the Ambechoic concept: https://community.klipsch.com/forums/storage/3/1654955/Mono2Surround.pdf

 

Another relevant thread on the subject: https://community.klipsch.com/index.php?/topic/135869-small-room-acoustics-and-diffusers/

 

Chris

Edited by Chris A
Link to comment
Share on other sites

The 20% absorption rule-of-thumb is something that I arrived at independently of this presentation.  But not all reflections and absorption surfaces are created equal--with nearfield reflections of less than 2ms being the most important to control through absorption or placement of loudspeakers. 

 

Corner horns and corner-located loudspeakers usually require some absorption on the walls immediately adjacent to the midrange horn mouths.  Most folks get the one wrong, and decide to abandon corner-located placements due to these early midrange reflections, but the wind up losing about 1/2 to one octave of good bass when they move their speakers out onto the floor away from the corners.  PWK wrote on corner placement of loudspeakers fairly extensively, showing the advantages of smoothness and extension of bass by this simple method, but he didn't talk about controlling early midrange reflections very much, which I've found to work almost like magic.

 

The 25% diffusion is also probably around what that I've got (by default) due to room boundary irregularities and other objects in the room, but not the least of which is the length of the room of ~40 feet. But certainly there is a lot of diffusion in the room down to low frequencies as evidenced by in-room measurement waterfall plots with REW.

 

Here is an interesting article in pdf format that I like a lot from Dr. Peter D'Antonio, the originator of the RFZ--the reflection-free zone concept and Reflection-Phase Grating (RPG) and plate resonator designs as well as the Ambechoic concept: https://community.klipsch.com/forums/storage/3/1654955/Mono2Surround.pdf

 

Another relevant thread on the subject: https://community.klipsch.com/index.php?/topic/135869-small-room-acoustics-and-diffusers/

 

Chris

 

Interesting writeup, thank you for sending. As a general rule I like to absorb the primary reflection points from the L/R channels and someday will do the center as well to keep the voices clear during movies. I think from that point you would want to do bass management in the corners then use diffusion for the surround and rear reflection points to keep the room 'alive'.

Link to comment
Share on other sites

Thanks for posting the videos.... twk123

Anthony Grimani comments about the need for diffusion and cautions about over absorption were spot on. Over use of absorption as well as misplacement especially with horn type loudspeakers can lead to much worse problems than what one might have began with and often leads to listener fatigue rather quickly.

Also some form of modal control/compensation is a must in the majority of all listening rooms if one wants to experience the full capability of their system.

The equipment marry-go-round that so many find themselves on can be traced back to the lack of attention to the room's acoustical weaknesses and the proper corrective actions often needed.

Seems most listeners are intent on spending their money and time chasing the annoying fly while ignoring the elephant in the room..... :-)

miketn

 

This is so true. My Uncle spent a ton of money on his HT system but paid no attention to room acoustics. They professional installers ran all the EQ but someone got into the settings on accident and messed it up and he had no idea how to fix it. The other problem with EQ is that it may sounds great for you in the sweet spot but your buddies will wonder why there is no/way too much bass because the EQ amplified the wrong settings for other seats because the sweet spot was in a bass null etc. 

Link to comment
Share on other sites

 

Thanks for posting the videos.... twk123

Anthony Grimani comments about the need for diffusion and cautions about over absorption were spot on. Over use of absorption as well as misplacement especially with horn type loudspeakers can lead to much worse problems than what one might have began with and often leads to listener fatigue rather quickly.

Also some form of modal control/compensation is a must in the majority of all listening rooms if one wants to experience the full capability of their system.

The equipment marry-go-round that so many find themselves on can be traced back to the lack of attention to the room's acoustical weaknesses and the proper corrective actions often needed.

Seems most listeners are intent on spending their money and time chasing the annoying fly while ignoring the elephant in the room..... :-)

miketn

 

This is so true. My Uncle spent a ton of money on his HT system but paid no attention to room acoustics. They professional installers ran all the EQ but someone got into the settings on accident and messed it up and he had no idea how to fix it. The other problem with EQ is that it may sounds great for you in the sweet spot but your buddies will wonder why there is no/way too much bass because the EQ amplified the wrong settings for other seats because the sweet spot was in a bass null etc. 

 

You don't have to have EQ in the equation for that problem to exist.  Getting the treatment right will make it better for everybody though but the person in the sweet spot is still going to have the best sound.  The ROOM is certainly my biggest project now but I've been spending too much on music lately.  That isn't really a bad thing though!   I must be getting closer to good sound if I find myself listening more and tweaking less.

  • Like 1
Link to comment
Share on other sites

The other problem with EQ is that it may sounds great for you in the sweet spot but your buddies will wonder why there is no/way too much bass because the EQ amplified the wrong settings for other seats because the sweet spot was in a bass null etc.

 

Audyssey and the like normally EQ 5 to 7 seating positions.

  • Like 1
Link to comment
Share on other sites

  • 6 months later...
  • 2 months later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...