Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Late Ceiling Splash
Late Ceiling Splash
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th January 2019, 07:47 PM   #31
audiokinesis is offline audiokinesis  United States
diyAudio Member
 
Join Date: Oct 2007
Location: Princeton, Texas
One apparent effect of the additional late-onset reverberant energy for which I have no satisfactory explanation is the way it seems to let you hear more of the acoustic space that's on the recording. It seems to facilitate the ear/brain system getting a good fix on the reverberation in the recording, as opposed to the reverberation signature of your actual listening room.

At Axpona 2016, Andrew Quint of The Absolute Sound came into the room. I gave my schpiel and he listened politely, then pulled out a thumb drive and said, "I'd like to challenge that." So we played the recording on his thumb drive and I asked him how we did. He said, "It works, it's not a gimmick. I could hear the acoustic signature of the hall the recording was made in."

Quoting from an online post Andrew subsequently made:

"I'll elaborate a bit on the recording in question and what I heard in my brief audition of Duke's new speaker.

"The recording was a FLAC rip of the CD layer of an RCO Live SACD: Shostakovich—Symphony No. 15; Concertgebouw Orchestra/Bernard Haitink conductor. It's a live recording from March of 2010 (Haitink made a much earlier recording of the same piece with the London Philharmonic; he was the first person to record all the Shostakovich symphonies.) For a couple of years, this has been my go-to symphonic recording when I have just a short time to get a sense of an unfamiliar system. It's an excellent performance, something I can listen to repeatedly without going nuts, which is important at a show. In terms of audiophilia, it's an extremely detailed yet atmospheric representation of an orchestra, with excellent dynamics and fully characterized instrumental colors (bells, solo turns by violin, flute, piccolo, string bass, trumpet, etc.) And—with the right audio gear—it successfully renders the essence of (IMO) one of the greatest 3 or 4 concert halls on earth, the Concertgebouw (thus the orchestra's name) in Amsterdam. I've heard music there, and there's truly a sense of sound being present in the air around you.

"The multichannel program on the RCO Live SACDs (there are dozens) get this last aspect right; so did the Bienville Suite, nearly to the same degree, despite the presence of only two channels. My concern when Duke told me about the rear-firing drivers was that this would impart some generic, Bose-like spaciousness to the recording, but that wasn't the case—what I heard was the unique acoustic signature of the Concertgebouw.

"So, a splendidly realized design—a pleasure to listen to."

I wish I knew EXACTLY why this effect was happening, so I could then perhaps optimize further.

Last edited by audiokinesis; 16th January 2019 at 07:52 PM.
  Reply With Quote
Old 16th January 2019, 07:58 PM   #32
mmerrill99 is offline mmerrill99
diyAudio Member
 
Join Date: Aug 2014
Yes, Griesinger is the man when it comes to concert hall acoustics - he even points out in one of his presentations where he finds Toole is incorrect.

The decorrelated reverberation is an interesting phenomena
Gary S. Kendall has published research & book (1995) on the 5 perceptual effects of decorrelated reverberation:
- the timbral coloration and combing is avoided because the constructive & destructive interference of multiple delayed signals is perceptually eliminated
- the diffuse sound fields akin to the late field of reverberant concert halls
- the externalization in headphone reproduction
- the lack of image shift because :
- the precedence effect is defeated

Perceptual research has progressed a lot since 1995 particularly the area of Auditory Scene Analysis (Bregman 1990) which is concerned with how we analyze/categorize all the vibrations that belong to separate auditory objects & how we are able to similarly follow separate auditory streams.

The perceived naturalness of decorrelated reverberation has to do with how sounds in nature are reflected off many surfaces before reaching our ears - essentially decorrelating the reflections. This, as you say allows us to perceive the sound as foreground & background auditory streams allowing us to separately evaluate the sound making object & the environment in which the sound was made. Recent research (2016) suggests that we use statistical summaries of such background streams & evaluate them as natural if they conform to the statistical regularities found in nature
Quote:
We conducted a large-scale statistical analysis of real-world acoustics, revealing strong regularities of reverberation in natural scenes. We found that human listeners can estimate the contributions of the source and the environment from reverberant sound, but that they depend critically on whether environmental acoustics conform to the observed statistical regularities. The results suggest a separation process constrained by knowledge of environmental acoustics that is internalized over development or evolution.
You might find the above line of research of interest in your quest to get to the bottom of this & optimize it further in your speakers?

It strikes me that BMR (Bimodal Mode Radiator) drivers produce decorrelated signals by default but I wonder do they satisfy the above criteria? Have you experimented with these BMR drives in the role of your back/ceiling firing speaker?

Last edited by mmerrill99; 16th January 2019 at 08:18 PM.
  Reply With Quote
Old 16th January 2019, 09:03 PM   #33
bwaslo is offline bwaslo  United States
Old guy with soldering iron
diyAudio Member
 
bwaslo's Avatar
 
Join Date: May 2006
Location: Portland, Oregon!
Late Ceiling Splash
Quote:
Originally Posted by audiokinesis View Post
Ime it depends on the room - if you have a fair amount of space behind you then diffusion works well on the back wall. If you are very close to it, then you may have to resort to absorption.
Diffusors (at least the ones I've looked into) don't work well close up, need some distance from the ear and the source to really diffuse well.

Wondering whether you have tried running your LCS speaker from another amp, fed with a delayed version of the main signal? 10msec is about all the delay that can be had in most rooms by reflecting off the ceiling. In my (very limited!) playing with ambience tweeters fed through DSP and delay, it seems that it works better with more delay up to near 20msec or so (in addition to the added delay of most of that signal from walls and ceiling).
__________________
[W9MJE] Horn spreadsheet SynergyCalc/; SmallSyns SmallSyns;
Crossover design Xsim; Depot diffusor super-easy diffusors
  Reply With Quote
Old 17th January 2019, 05:35 AM   #34
audiokinesis is offline audiokinesis  United States
diyAudio Member
 
Join Date: Oct 2007
Location: Princeton, Texas
Quote:
Originally Posted by mmerrill99 View Post
Yes, Griesinger is the man when it comes to concert hall acoustics - he even points out in one of his presentations where he finds Toole is incorrect.

The decorrelated reverberation is an interesting phenomena
Gary S. Kendall has published research & book (1995) on the 5 perceptual effects of decorrelated reverberation:
- the timbral coloration and combing is avoided because the constructive & destructive interference of multiple delayed signals is perceptually eliminated
- the diffuse sound fields akin to the late field of reverberant concert halls
- the externalization in headphone reproduction
- the lack of image shift because :
- the precedence effect is defeated

Perceptual research has progressed a lot since 1995 particularly the area of Auditory Scene Analysis (Bregman 1990) which is concerned with how we analyze/categorize all the vibrations that belong to separate auditory objects & how we are able to similarly follow separate auditory streams.

The perceived naturalness of decorrelated reverberation has to do with how sounds in nature are reflected off many surfaces before reaching our ears - essentially decorrelating the reflections. This, as you say allows us to perceive the sound as foreground & background auditory streams allowing us to separately evaluate the sound making object & the environment in which the sound was made. Recent research (2016) suggests that we use statistical summaries of such background streams & evaluate them as natural if they conform to the statistical regularities found in nature

You might find the above line of research of interest in your quest to get to the bottom of this & optimize it further in your speakers?
YESSSS! Thank you VERY MUCH for this information and the links!!

One of the "trade secrets" I alluded to earlier has to do with decorrelation.

Quote:
Originally Posted by mmerrill99 View Post
It strikes me that BMR (Bimodal Mode Radiator) drivers produce decorrelated signals by default but I wonder do they satisfy the above criteria? Have you experimented with these BMR drives in the role of your back/ceiling firing speaker?
My understanding is the bending-wave radiators have very wide radiation patterns, and that would make it difficult at best to avoid relatively early-arrival contributions. Please correct me if I am wrong, as I really don't know much about them.
  Reply With Quote
Old 17th January 2019, 05:45 AM   #35
audiokinesis is offline audiokinesis  United States
diyAudio Member
 
Join Date: Oct 2007
Location: Princeton, Texas
Quote:
Originally Posted by bwaslo View Post
Wondering whether you have tried running your LCS speaker from another amp, fed with a delayed version of the main signal? 10msec is about all the delay that can be had in most rooms by reflecting off the ceiling. In my (very limited!) playing with ambience tweeters fed through DSP and delay, it seems that it works better with more delay up to near 20msec or so (in addition to the added delay of most of that signal from walls and ceiling).
I have not tried delaying the LCS signal, but that totally makes sense, and there's no reason why it shouldn't be done. Your 20 millisecond target figure sounds right to me too.

I've been focused on a passive solution with a high enough impedance to be safely run in parallel with the main speaker in most cases, but the "next level up" would probably be what you describe.

Did we meet at Lone Star Audio Fest many years ago?
  Reply With Quote
Old 17th January 2019, 06:37 AM   #36
celef is offline celef
diyAudio Member
 
Join Date: Nov 2012
To get 20ms delayed reflections, then how large listening rooms should we strive for?
  Reply With Quote
Old 17th January 2019, 09:24 AM   #37
Adhoc1 is offline Adhoc1
diyAudio Member
 
Join Date: Apr 2012
Extra path length of about 20 ms means about 6 m. So, if the wall behind you is about 2-3 m away you should be fine. Direct reflection from back wall: 2 x 3 m. A reflection from backwall to sidewall to LP means the distance behind you can be decreased to under 3 m. If possible, it should be advantageuos if sound from left speaker could be steered / reflected from the backwall to sidewall and end up at you right ear. -To get that decorrelated sound mentioned in previous posts. A reflection from straight behind is of "less value" than those coming in at an angle to your ears, as side reflections are more easliy heard and can be of lower stregth.

If you cannot get rid of audible reflections from ahead / side of you before about 15-20 ms has passed I see little use to try to fix up something behind you. Serious designers for control rooms often strive for 20 ms (ideal) silence between direct sound and reflected sound, -an Initial Time Delay Gap (ITD or ITDG). Depending on room conditions one may have to accept 15 ms = OK, 10 ms not so good anymore, passable ?. Ideal strength for reflections during the "silent stage": -20 dB and weaker, -20 to -15 dB or so = OK.

If you can avoid early audible reflections but get fairly strong ones later on, say 15-30 ms, you fool your brain into beliving your room is larger and more spacious than it actually is. -The walls / ceiling seem to be further away as audible reflections are late in time corresponinding to further away.

If one succeds with that ITD, the soundstage will narrow in width but you should hear more of what is actually recorded, the room where recording took place, position of persons / instruments. Widening of the sound stage can be seen as a "false width". That doesn't mean it is unpleasant to get that "false width. Pick your poison.

Last edited by Adhoc1; 17th January 2019 at 09:44 AM.
  Reply With Quote
Old 18th January 2019, 06:16 AM   #38
audiokinesis is offline audiokinesis  United States
diyAudio Member
 
Join Date: Oct 2007
Location: Princeton, Texas
Quote:
Originally Posted by celef View Post
To get 20ms delayed reflections, then how large listening rooms should we strive for?
20 milliseconds roughly corresponds to a 22 foot path length difference between the first-arrival sound and the reflections. So you'd either need VERY tall ceilings if using late ceiling splash, or a very large room if using a bipole or dipole system (with the added reflections now in the horizontal plane instead of going vertical), OR a delayed signal as bwaslo suggests.

Quote:
Originally Posted by Adhoc1 View Post
If you can avoid early audible reflections but get fairly strong ones later on, say 15-30 ms, you fool your brain into beliving your room is larger and more spacious than it actually is. -The walls / ceiling seem to be further away as audible reflections are late in time corresponinding to further away.
The first time I experienced this was in a recording studio control room designed by Jeff Hedback. When I closed my eyes, it sounded like the room was about twice as big as its physical dimensions. It was a bit disorienting.

Quote:
Originally Posted by Adhoc1 View Post
If one succeeds with that ITD, the soundstage will narrow in width but you should hear more of what is actually recorded, the room where recording took place, position of persons / instruments. Widening of the sound stage can be seen as a "false width". That doesn't mean it is unpleasant to get that "false width. Pick your poison.
Yesss!!! The early sidewall reflections "broaden" the image, so when we remove them the soundstage correspondingly narrows, but then we can re-position the speakers accordingly.

I'm an advocate of Geddes' approach, using speakers with a 90 degree pattern (-6 dB limits) in the horizontal plane, then toeing them in by 45 degrees, which results in negligible early same-sidewall reflections. In fact the first significant sidewall reflection of the left speaker will be the long across-the-room bounce off the right side wall, and vice versa. This also introduces de-correlation, as the first sidewall reflection of the left speaker's direct sound arrives at the right ear, and vice-versa.

A bit of creativity is called for if we also want to suppress the floor and ceiling bounces. Fortunately these are of less audible consequence than the first sidewall bounces, but those who have addressed them usually say it's worth doing.
  Reply With Quote
Old 18th January 2019, 08:43 AM   #39
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Quote:
Originally Posted by audiokinesis View Post
it seems to let you hear more of the acoustic space that's on the recording. It seems to facilitate the ear/brain system getting a good fix on the reverberation in the recording, as opposed to the reverberation signature of your actual listening room.
This is well achieved by reducing early reflections.

Last edited by AllenB; 18th January 2019 at 08:49 AM.
  Reply With Quote
Old 18th January 2019, 06:18 PM   #40
audiokinesis is offline audiokinesis  United States
diyAudio Member
 
Join Date: Oct 2007
Location: Princeton, Texas
Quote:
Originally Posted by AllenB View Post
This is well achieved by reducing early reflections.
That's a vital part of it, but in my experience the additional late-onset reflections do make a significant improvement.

At RMAF 2018, Kal Rubinson of Stereophile came by our room. He listened to a bit and then asked us to turn the LCS section off and play the same thing again. Literally within the first two seconds he was saying something like, "oh, I see what you mean."

(Kal made it clear to us that he was not at the show to do a show report. He usually covers multichannel systems, but occasionally reviews particularly interesting two-channel, like the Bang & Olufsen Beolab 90.)

Last edited by audiokinesis; 18th January 2019 at 06:22 PM.
  Reply With Quote

Reply


Late Ceiling SplashHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Better late than never mythless Introductions 4 11th November 2013 04:23 PM
<mid>woofer "splash" pski Construction Tips 0 8th November 2011 11:27 PM
Late Hi RCruz Introductions 6 25th November 2008 01:10 PM
Better late than never... rjon17469 Introductions 2 22nd August 2005 04:01 PM


New To Site? Need Help?

All times are GMT. The time now is 10:39 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki