• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

A cloud is the single most important acoustic treatment. Change my mind.

Music1969

Major Contributor
Joined
Feb 19, 2018
Messages
4,548
Likes
2,759
My guess is, the OP refers to speakers like the KH120 II but you can find similar recommendations ("Absorb ceiling reflection") in many of Amir's reviews. The null in the ceiling reflection comes from a 180° phase difference between woofer and tweeter in this direction at crossover.
Thanks, would we see this same dip in anechoic measurement?

If so, how does ceiling absorption help with this particular speaker ?
 

fpitas

Master Contributor
Forum Donor
Joined
Jul 7, 2022
Messages
9,885
Likes
14,156
Location
Northern Virginia, USA
Thanks, would we see this same dip in anechoic measurement?

If so, how does ceiling absorption help with this particular speaker ?
You won't get a reflection of the faulty FR aimed at the ceiling.
 

JohnnyNG

Active Member
Joined
Dec 24, 2019
Messages
176
Likes
181
My guess is, the OP refers to speakers like the KH120 II but you can find similar recommendations ("Absorb ceiling reflection") in many of Amir's reviews. The null in the ceiling reflection comes from a 180° phase difference between woofer and tweeter in this direction at crossover.

Neumann KH120 II Professional Monitor Speaker Active DSP early window frequency response measu...png
Yes - this is exactly what I'm refering to with my "nearfield absorber" question above. My Revel M106 seem to have no issue with the ceiling bounce but looking at the KH120 II or KH150 it's much more severe.
 

Bjorn

Major Contributor
Audio Company
Forum Donor
Joined
Feb 22, 2017
Messages
1,268
Likes
2,512
Location
Norway
The idea that you should only treat effectively down to 1-2 kHz area because of the vertical lobing around the crossover isn't good. This is not only about minimizing a speaker flaw but also remove very audible and detrimental specular reflections in the time domain. And for that, treatment should ideally be effective to the Schroeder frequency or at least till 500 Hz. Only treating effectively down to 1 kHz or 800 Hz area never sounds right. That's typically one step forward and a step backwards.
 

fpitas

Master Contributor
Forum Donor
Joined
Jul 7, 2022
Messages
9,885
Likes
14,156
Location
Northern Virginia, USA
The idea that you should only treat effectively down to 1-2 kHz area because of the vertical lobing around the crossover isn't good. This is not only about minimizing a speaker flaw but also remove very audible and detrimental specular reflections in the time domain. And for that, treatment should ideally be effective to the Schroeder frequency or at least till 500 Hz. Only treating effectively down to 1 kHz or 800 Hz area never sounds right. That's typically one step forward and a step backwards.
I completely agree. I put up broadband absorbers.
 
OP
D

dfuller

Major Contributor
Joined
Apr 26, 2020
Messages
3,295
Likes
4,985
This part I quoted - what cancellations do you mean ? Can you give a specific example with a non coaxial speaker ?

Are you specifically talking about vertical directivity ?
Yes. Notice how the most different from on-axis is the ceiling bounce? That's what I'm talking about.
1695128657160.png


3-ways are not immune either. In fact, now there are 2 dips.
1695128832451.png



The idea that you should only treat effectively down to 1-2 kHz area because of the vertical lobing around the crossover isn't good. This is not only about minimizing a speaker flaw but also remove very audible and detrimental specular reflections in the time domain. And for that, treatment should ideally be effective to the Schroeder frequency or at least till 500 Hz. Only treating effectively down to 1 kHz or 800 Hz area never sounds right. That's typically one step forward and a step backwards.
This is also correct; I'm not saying just stick HF only foam absorbers up there and ignore anything going on below, rather that ceiling bounce is not good in general. Personally I'm using 4" thick broadband absorbers with a 4" air gap.
 

Bjorn

Major Contributor
Audio Company
Forum Donor
Joined
Feb 22, 2017
Messages
1,268
Likes
2,512
Location
Norway
4" is ok, but a 4" air gap is actually counter effective unless it's closed on all sides. The energy flows out and absorption is lost.
 
OP
D

dfuller

Major Contributor
Joined
Apr 26, 2020
Messages
3,295
Likes
4,985
4" is ok, but a 4" air gap is actually counter effective unless it's closed on all sides. The energy flows out and absorption is lost.
Yeah, I'd have liked to not have the air gap but the mounting brackets I have from GIK pretty much dictate it. Oh well.
 

fpitas

Master Contributor
Forum Donor
Joined
Jul 7, 2022
Messages
9,885
Likes
14,156
Location
Northern Virginia, USA
Yeah, I'd have liked to not have the air gap but the mounting brackets I have from GIK pretty much dictate it. Oh well.
I'm in a similar situation. 4" thick cotton waste batting is available cheaply enough. And I happen to have a few pieces laying around. I wonder if that would be superior to an air gap.
 

olieb

Active Member
Joined
Jul 1, 2023
Messages
241
Likes
327
The idea that you should only treat effectively down to 1-2 kHz area because of the vertical lobing around the crossover isn't good.
No, certainly not. This way the FR of the reflection would get even worse. Whatever one does it should be broadband.
• deflect the sound around the point of first reflection (to the speaker or the side or...)
• absorb the sound
• diffuse the sound
For the last option it is not easy to achieve a broadband effect from 200 (or 400 Hz) up.
 

IPunchCholla

Major Contributor
Forum Donor
Joined
Jan 15, 2022
Messages
1,098
Likes
1,373
For the graphs, what are the assumed room dimensions and far field listening position?
 

olieb

Active Member
Joined
Jul 1, 2023
Messages
241
Likes
327
For the graphs, what are the assumed room dimensions and far field listening position?
From the standard ANSI-CTA-2034-A:
The following composite response curves shall be calculated. In each instance a power average of the specified magnitude responses shall be calculated.

Listening Window
The listening window curve is a spatial average of the nine magnitude responses in the ±10° vertical and ±30° horizontal angular range.
• 0°
• ± 10° vertical
• ± 10°, ± 20°, ± 30° horizontal

Early Reflections
The early reflections curve is an estimate of all single-bounce, first-reflections, in a typical listening room.
  • Floor Bounce: 20°, 30°, 40° down
  • Ceiling Bounce: 40°, 50°, 60° up
  • Front Wall Bounce: 0°, ± 10°, ± 20°, ± 30° horizontal
  • Side Wall Bounces: ± 40°, ± 50°, ± 60°, ± 70°, ± 80° horizontal
  • Rear Wall Bounces: 180°, ± 90° horizontal
 

ernestcarl

Major Contributor
Joined
Sep 4, 2019
Messages
3,087
Likes
2,297
Location
Canada
A dead room isn't as accurate as many think due to psychoacoustics. Few have heard the combination of accurate and lively, and generally don't know how that sounds.

Perhaps... though "dead" room is simply a catch-all phrase generalization. Liveliness and envelopment can be artificially induced in said "dead" room, of course, via additional speakers and DSP. Yeah... I'm already aware that you think it's deeply flawed and merely a cheap imitation copy of the "real" thing.
 

Axo1989

Major Contributor
Joined
Jan 9, 2022
Messages
2,690
Likes
2,713
Location
Sydney
For the graphs, what are the assumed room dimensions and far field listening position?

I asked this question of the speaker test data also. Angle is one thing, but you would think the amplitude of the reflection arriving at LP would reduce normally according to distance. So "a typical listening room' would have some sort of dimension. Unless there is a different explanation.
 

ErVikingo

Active Member
Forum Donor
Joined
Dec 16, 2022
Messages
261
Likes
279
Location
FL USA
Look up!

IMG_4129.jpeg
 
Top Bottom