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

[Music1969]

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]

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]

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.

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.

 

[Music1969]

You won't get a reflection of the faulty FR aimed at the ceiling.

But this faulty FR will still bounce off floor and reflect to your ears ?

 

[JohnnyNG]

But this faulty FR will still bounce off floor and reflect to your ears ?

The floor bounce is shown separately and is often much less severe (as with the KH120II). Do you see it in the plot?

 

[Bjorn]

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]

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.

 

[dfuller]

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.

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

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]

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.

 

[dfuller]

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]

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]

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]

For the graphs, what are the assumed room dimensions and far field listening position?

 

[olieb]

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

 

[ozzy9832001]

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.

Do you have a source for this?

 

[ernestcarl]

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.

 

[Bjorn]

Do you have a source for this?

It stems from Ron Sauro's and NWAA Labs' work and measurements. The site seems to be down now or not secure.
https://www.nwaalabs.com/

 

[onion]

My music room ceiling is plastered with this stuff - https://www.baswana.com/tech-data

Seems to work well with my music system

 

[Axo1989]

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]

Look up!