Ron’s New System

[LL21]

I think that everybody who has visited my listening room hears the improvement in the room modes occasioned by the AVAA active bass absorbers.

A couple of days ago I got around to doing a formal test to see the observable measurable difference in room boom peaks at 45Hz and at 60Hz with the three AVAAs on versus the three AVAAs off.

Using my pro audio Earthworks QTC-4 on a stand at exactly the ears' listening position, broadband pink noise and a test tone at 63Hz to the real time analyzer on my iPad, there was no observable, measurable difference in attenuation of room modes whether the AVAAs were on or off. This is a anomalous result I do not understand.

I have a lot of trouble believing approximately 15 people psychosomatically subjectively heard mitigation of the room boom, and we all were deluding ourselves.

I think I am using the same frequency response measurement protocol I have always used. I can't figure out why I'm not seeing a measureable difference.

I am no techie...but I wonder if what people are hearing without your AVAAs is purely decibels. Is it overhang, thickness, something else which is not purely about decibels? And is the AVAA only about decibels? They certainly talk about reducing decibels...but I wonder if they do anything else in technical terms which assists in intelligibility of that frequency range.

Also, I have no idea how sensitive your db reader is, but i can tell you from experience having listened to the old X1/Grand SLAMMS before finetuning, the treble had been set up 2db higher by previous owner in their room, and it was so piercing that I actually told the dealer when I heard them in the store after they arrived that if that was how they were going to sound in our home, NOT to even bother bringing them to the house. It was so piercing, I did not want 4 guys to unload the whole thing just to know I was sending them back.

He assured me it would be perfect...and after reducing 2db in-situ during setup, it was sublime by comparison. We are more sensitive to treble than bass, but again not sure if you are sure the measurements are within less than 1db between with and without AVAA? Unless the room was significantly louder in bass without than with.

 

[exupgh12]

can the root of this be in the way that the AVVA C20 works?

In theory, the active drive unit generates a sound wave with an inverted polarity but at the same level as the reflected sound wave.

The AVVA absorbed by the controlled movement of the drive unit’s diaphragms (resistance membrane) maybe this is why you’re not seeing things in the measurement’s ?

 

[Carlos269]

can the root of this be in the way that the AVVA C20 works?

In theory, the active drive unit generates a sound wave with an inverted polarity but at the same level as the reflected sound wave.

The AVVA absorbed by the controlled movement of the drive unit’s diaphragms (resistance membrane) maybe this is way you’re not seeing things in the measurement’s ?

If the original sound reaches the ear/microphone that’s okay. These devices are intended to attenuate standing waves. A waterfall plot is what is needed to show the decays and how effective the AVA active tube traps really are.

 

[Johan K]

can the root of this be in the way that the AVVA C20 works?

In theory, the active drive unit generates a sound wave with an inverted polarity but at the same level as the reflected sound wave.

The AVVA absorbed by the controlled movement of the drive unit’s diaphragms (resistance membrane) maybe this is way you’re not seeing things in the measurement’s ?

Fully agree on this… Better to use a cd with bass test-tones going from at least 20 to 100Hz with 5Hz increments, and play these tones at the same volyme and LISTEN to the different frequences and determine if the volyme is the same over the frequency span. It should be quite easy to hear if the AVAA’s work or not, when they are on and off.

The frequences are easy to download on this somewhat weird looking site, save and copy to a USB stick or a CD:

Untitled Document

Untitled Document

www.diffusor.com

/ Jk

 

[Ron Resnick]

What to believe, what to believe...the measurements or what you are hearing?

I reported this to Jason Hanan, my PSI dealer who installed the AVAAs, along with all of the screenshots. I think I'll try to schedule him to visit at his convenience and try to figure this out on-site.

When he installed the first two AVAAs he and I and his assistant all clearly saw on the RTA the AVAAs shaving down the room mode peaks.

 

[exupgh12]

I reported this to Jason Hanan, my PSI dealer who installed the AVAAs, along with all of the screenshots. I think I'll try to schedule him to visit at his convenience and try to figure this out on-site.

When he installed the first two AVAAs he and I and his assistant all clearly saw on the RTA the AVAAs shaving down the room mode peaks.

Ron,

Just yesterday I attended a visit to friend who use the AVVA C214 modele (2 units), all ought we didn’t measure anything the audible difference between on and off mode was unquestioned by all attendees. with respect for measurement, its just a tool, important one but tool, not replacement for my ears.

 

[Ron Resnick]

Thank you for that interesting report. But even as much of a subjectivist as I am, it is baffling to me that I cannot objectively prove the efficacy of the AVAAs on what I think is a well thought through measurement protocol.

I must be missing something when I conducted the measurements experiment.

 

[Ron Resnick]

Using 63Hz test tone from Stereophile CD:

 

[LL21]

1. If anything, you've got something minor going on at 105-110hz and 300hz - 500hz
2. And again, it might well be that absolute decibels is not the issue nor what the AVAA is solving for?

from SoundonSound on the AVAA https://www.soundonsound.com/reviews/psi-audio-avaa-c20

"...the basic idea is that the microphone senses the arrival of a low-frequency sound wave and the electronics calculate the level and phase of that same sound wave after it’s reflected from the adjacent room boundary a few hundred microseconds later. This is not as easy as it sounds because of the speed-of-sound delays associated with the inherent physical spacing between the microphone, the boundary and the subwoofer.

In theory, though, the active drive unit then generates a sound wave with an inverted polarity but the same level as the naturally reflected sound wave, and it is phased (or timed) precisely such that the two cancel each other out more or less completely. In some practical situations it may actually be more desirable not to kill the reflections completely...

...Another way of thinking of this kind of technology is that, in effect, the system works to maintain a zone around it of constant ambient atmospheric pressure, essentially preventing the pressure build-up that naturally occurs near a room boundary when sound waves arrive...."

 

[microstrip]

Thank you for that interesting report. But even as much of a subjectivist as I am, it is baffling to me that I cannot objectively prove the efficacy of the AVAAs on what I think is a well thought through measurement protocol.

I must be missing something when I conducted the measurements experiment.

You have to measure the time decay or use a waterfall type measurement to confirm the action of such device.

 

[morricab]

Using 63Hz test tone from Stereophile CD:


View attachment 115727

View attachment 115728

Are you SURE you had them turned on? Perhaps cleaning lady turned off the power strip??

 

[AudioGod]

Amazing system
Can we expect a full review of the Gryphon Speakers?

 

[Folsom]

I think that everybody who has visited my listening room hears the improvement in the room modes occasioned by the AVAA active bass absorbers.

A couple of days ago I got around to doing a formal test to see the observable measurable difference in room boom peaks at 45Hz and at 60Hz with the three AVAAs on versus the three AVAAs off.

Using my pro audio Earthworks QTC-4 on a stand at exactly the ears' listening position, broadband pink noise and a test tone at 63Hz to the real time analyzer on my iPad, there was no observable, measurable difference in attenuation of room modes whether the AVAAs were on or off. This is a anomalous result I do not understand.

I have a lot of trouble believing approximately 15 people psychosomatically subjectively heard mitigation of the room boom, and we all were deluding ourselves.

I think I am using the same frequency response measurement protocol I have always used. I can't figure out why I'm not seeing a measureable difference.

What is your time window for measurement? (gate)

 

[Ron Resnick]

What is your time window for measurement? (gate)

"Slow"

 

[heebrog]

Hi Ron. I believe @microstrip is correct in that you have to look at the "waterfall" plot.
I have x2 AVAA's in the front corner of my room.
I am no expert but here are some measurements that I took using REW before and after some room treatment + AVAA's
WRT to AVAA's just look at <150Hz on the plots.

 

[RCanelas]

I wouldn't expect much difference in terms of power response. And that's a good thing!

As @microstrip and @heebrog mentioned you should use measurements with a time component, either decay (RT60 is a nice and simple to use tool) or a waterfall plot (harder to get actionable data).

This is why every time people tell me 'look at this perfect straight power response, this sounds perfect, can't get any better than this' I typically zone out.

 

[Ron Resnick]

You have to measure the time decay or use a waterfall type measurement to confirm the action of such device.

Why is this, Francisco?

Why wouldn't the attenuation action of the AVAAs at specific frequencies be visible in the amplitude dimension?

 

[pjwd]

Why is this, Francisco?

Why wouldn't the attenuation action of the AVAAs at specific frequencies be visible in the amplitude dimension?

Ron
I suspect that the AVAA are reducing the reverberation time of the peak which is the improvement you are hearing .. but not reducing the actual peak.
Your measuring device , while handy, is not sophisticated enough to capture the time elements which is why folks are talking waterfall plots, gating, etc
You really need to get into REW or similar to go to the next level
Its worth the effort !
Phil

 

[Ron Resnick]

Ron
I suspect that the AVAA are reducing the reverberation time of the peak which is the improvement you are hearing .. but not reducing the actual peak.
Your measuring device , while handy, is not sophisticated enough to capture the time elements which is why folks are talking waterfall plots, gating, etc

Thank you for the explanation!

 

[microstrip]

Why is this, Francisco?

Why wouldn't the attenuation action of the AVAAs at specific frequencies be visible in the amplitude dimension?

Bass traps would need to be of enormous size and have extreme absolution to modify the frequency response significantly. Their action is usually more visible in the frequency response when they cancel dips than when they attack the peak frequencies.

However, one very critical parameter for bass quality is how fast the bass energy fades after a bass sound - this means it is not kept resonating in the room, blurring the bass. This can be easily measured with REW or similar software to get a measure of it. However, due to the FFT analysis, there are serious limitations to this method - we have to properly balance frequency resolution and time resolution - many waterfall measurements we see around are highly misleading.

Fortunately flat absolute frequency response in the bass is not too critical for great stereo sound - in most speakers and rooms the only way to approach it is using equalizers. I have seen the JLAudio subwoofer auto calibration feature improving significantly the bass of systems used with small speakers actively crossed around 120 Hz.