My dedicated audio room build - QuadDiffusor's Big Dig

[QuadDiffuser]

Very interesting.. have you tried it out.
Nice if pretty easy to get your head around ... quite expensive but may well be worth it.
At a simpler level I see the amroc guys are developing a more " pro version " for sale .. will also be interesting to see how deep it dives

Do you see yourself doing different diffusers as the location changes

Phil

Hi Phil, in my existing setup P17 QRDs cover the front wall, and P13 QRDs (in a 2D configuration) cover the first reflection points on the ceiling. And I love them!

In my future setup, I will be using P23 QRDs covering a sizeable area of approximately 3.5m (height) x 6m (width) on the exposed area of front wall [subtracting the L/R space (~30cm x 2) taken up by the double-damped gypsum sidewalls and damped-metal plate bass attenuation modules]. I'm still uncertain about how many/where/which QRDs to use on the sidewalls, however. As you can see, I'm still investigating and iterating.

 

[pjwd]

PJWD: in my current setup P17 QRDs cover the front wall, and P13 QRDs (in a 2D configuration) cover the first reflection point on the ceiling. And I love them!

In my future setup, I will be using P23 QRDs covering a sizeable area of approximately 3.5m (height) x 6m (width) on the exposed area of front wall (subtracting for the space needed for the double-damped gypsum sidewall construction and damped-metal plate bass attenuation modules). Still uncertain about how many/where/which QRDs to use on the sidewalls, however. As you can see, I'm still investigating and iterating.

QD, I would have thought varying them along side wall would alleviate lobing between the same diffusive patterns plus you could target them for the differing angle of incidence from speaker.
I must say I am very impressed at the depth of analysis you are applying.
I presume the dimensions on diffusers are cm ?

Cheers
Phil

 

[Cohnaudio]

Hi Phil, in my existing setup P17 QRDs cover the front wall, and P13 QRDs (in a 2D configuration) cover the first reflection points on the ceiling. And I love them!

In my future setup, I will be using P23 QRDs covering a sizeable area of approximately 3.5m (height) x 6m (width) on the exposed area of front wall (subtracting for the space taken by the double-damped gypsum sidewalls and damped-metal plate bass attenuation modules). I'm still uncertain about how many/where/which QRDs to use on the sidewalls, however. As you can see, I'm still investigating and iterating.

Have you thought about using hemispheric diffusers on the side.wall? Given the angle the sound strikes the diffusers on the side wall, I question how much more effective the QRDs will be. I have p23s on my front wall (3 periods, as more than that requires a different p to avoid too much reflection of particular frequencies), but don't have the ability to have the QRDs on my first reflections, as that is where the shelves for my albums are. I was thinking of either constructing a hemisphere or skylines on doors that cover the shelves and can be opened to access the albums. Any thoughts?

 

[MarkusBarkus]

...of the two, the hemispherical idea seems better. Won't much of the incoming waves hit the side of a skyline, rather than the different height blocks that comprise the "skyline" shape and cause the desired diffusion? You could choose to make the deflectors out of a thin wood which you could bend/arc and stain or paint for the desired look.

 

[Cohnaudio]

...of the two, the hemispherical idea seems better. Won't much of the incoming waves hit the side of a skyline, rather than the different height blocks that comprise the "skyline" shape and cause the desired diffusion? You could choose to make the deflectors out of a thin wood which you could bend/arc and stain or paint for the desired look.

That was kind of my thinking as well, though I believe (without any documentation on the matter) that the 2D QRDs are more effective at angles than 1D QRDs. The benefit of the QRDs over the hemispheres is that the QRDs are phase incoherent, so generally more diffuse sounding. Having said that, building skylines is an serious pain and they are heavy, so making doors out of them will be tricky. As you pointed out, the hemispheres can be made from bent plywood, which can be pretty light

 

[MarkusBarkus]

...this GIK product or the concept could be applied to a door/cab doors. I have a few of these in service on the walls, as well as Quads in back. Quads are not practical everywhere, as you know. And heavy! Mama-mia.

 

[Cohnaudio]

...this GIK product or the concept could be applied to a door/cab doors. I have a few of these in service on the walls, as well as Quads in back. Quads are not practical everywhere, as you know. And heavy! Mama-mia.

I have used those scatter plates as well - mostly as a way of keeping bass traps from being too absorbent of the mids and highs. Scattering is not the same as diffusion and to my ears they are not nearly as good sounding (i.e, it sounds more like direct reflections) the question I have is that for side wall diffusion, are hemispherical diffusers (which I have never tried) as, or more, effective than QRDs (2d or 1d)?

 

[QuadDiffuser]

UPDATE: new DC cables, and QuadStack DAC purchase

MSB Select Digital Director and Westminster Lab upgrade dc cables : The throne of MSB Select DAC secured!

The practice of replacing included accessories of hifi components with aftermarket ones is extremely common for audiophiles. How often are we using the included black colour generic powercords? How often are we using the icluded wallwart switching psu? ... etc There are many many more of...

www.whatsbestforum.com

 

[QuadDiffuser]

UPDATE: new DC cables, and QuadStack DAC purchase

MSB Select Digital Director and Westminster Lab upgrade dc cables : The throne of MSB Select DAC secured!

The practice of replacing included accessories of hifi components with aftermarket ones is extremely common for audiophiles. How often are we using the included black colour generic powercords? How often are we using the icluded wallwart switching psu? ... etc There are many many more of...

www.whatsbestforum.com

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Given the repeated and persistent delays resulting from a multitude of challenges for the construction and completion (now projected to take between 18-24 months from now) of our new house with its dedicated basement listening room, I've decided to delay my purchase of all "big ticket" components for my future system so that I can take my sweet time to research and audition a variety of cutting-edge equipment. Though inflation and price hikes will bite, on balance I believe I'll benefit from the option to choose from among many new products sporting new innovations and refinements of existing products, as the playing field is becoming even more competitive than ever.

 

[QuadDiffuser]

While browsing around the local Hi-Fi mall, I stumbled across these two second-hand units of PSI Audio's AVAAs; I bought them for my future basement listening room because there'll never be enough room-node mitigating devices, either active or passive!

 

[Argonaut]

I stumbled across these two second-hand units of PSI Audio's AVAAs while I was browsing around at the local Hi-Fi mall; I'll be buying them

Good work , a nice find

 

[QuadDiffuser]

Good work , a nice find

Thanks - I lucked out... its MSRP have been creeping up (+56% in seven years) so grab them while you can!

US$1,999 in 2016 (Stereophile's review: https://www.stereophile.com/content/psi-audio-avaa-c20-electronic-bass-trap)

US$3,115 currently (B&H: https://www.bhphotovideo.com/c/product/1352278-REG/psi_audio_avaa_b_active_velocity_acoustic_absorber.html?c3api=2572,138045322040&gclid=CjwKCAjw_aemBhBLEiwAT98FMhcHYsvEfNTkEc4pHguT1BSjveBu4bUrZr5R0PtJtMBR0-M9vRVihRoCFasQAvD_BwE)

 

[QuadDiffuser]

I've added four more (brand-new) PSI Audio AVAA C20s (analog circuitry, not DSP) to my "collection"... now I have ten of them, six in white, four in black! ;-)

 

[QuadDiffuser]

SUB-100Hz BASS

DEEP BASS is a hugely tough beast to slay because of its omnipresence and omnipotence in the listening room, creating modal augmentation and cancellation issues. To ascend, and scale to the peaks of this majestic mountain, huge boulders and slick ice faces are the metaphorical equivalent of the bass energy which us audiophiles are trying to conquer.

Below are some basic descriptions and diagrams of the hardware which I'm considering installing in my basement listening room. The exact design specifications and materials are proprietary; hence I'll need to describe them in generic terms.

Since few audiophiles have built listening rooms of this caliber (and have shared all of the nitty gritty details on the art and science), in addition to my extremely competent and experienced "hired gun" acoustician, I've had to independently challenge, evolve, and iterate the final design, using numerous cross-references (audio forums, books on room acoustics / psychoacoustic, content providers on YouTube, contributions from fellow audiophiles, etc.) regarding the application, effectiveness and performance of the room's great many individual components, just to be doubly sure I wouldn't be accepting anything superfluous, or worse, end up regretting, because that would be even more costly to eviscerate and rebuild. The journey has been challenging, but fun and hugely educational!

THE FLOOR
Four meters will be allocated to the speaker area, equal to ~38% of the room length, and the remaining six meters will be allocated to the listening area. The two sections of the floor will be physically separated - constrained-layer dampened, decoupled, floated, and grounded - sandwiching dissimilar energy-absorbing materials.

The speaker-area floor will be constructed with the following, starting from the RC structural floor substrate:
- 4mm+ high-density recycled rubber granule underlayment for under-screed/floating floor constructions
- 90mm+ high-density screed, with BRC mesh in the center for mechanical integrity/strength
- high-durability leveling compound
- perimeter decoupled from adjacent structures via sponge rubber strips + caulking

The listening-area floor will be constructed with the following, starting from the RC structural floor substrate:
- high density foam isolation strips (tall, providing vertical clearance), covered with steel C-channel support
- 50% of the space will be filled with 100kg/m3 Rockwool insulation, 50% of the space left as an air gap
- structural steel decking (thin)
- 45mm+ high-density screed, with BRC mesh in the center
- high-durability leveling compound
- perimeter decoupled from adjacent structures via sponge rubber strips + caulking

The loudspeakers (and subwoofers) will have a more solid/stiffer floor foundation from which they will launch their acoustic energy, but energy propagating through the floor will decay rapidly before it reaches the listening area.

The wall treatment will be as follows, addressing different axial mode frequencies between the different distances between the structural slabs/walls. VPR is the German word for Verbundplattenresonator, which translates into "plate resonators". They are extremely effective!
(visit the following link):

https://gearspace.com/board/studio-building-acoustics/667929-my-experiment-metal-panel-absorber.html

THE FRONT/BACK WALLS (axial mode target frequency of 31.5Hz)
Starting from the RC structural wall, there will be a double-layer sandwich of gypsum drywall
- 100mm free air space
- 50mm Rockwool (100kg/m3 density)
- vibration absorbing isolation wall bracket
- 12mm+ thick gypsum board (550kg+/m3 density)
- acoustic damping sheet (self-adhesive) applied in the center of the double drywall sandwich
- 12mm+ thick gypsum board (550kg+/m3 density)
- VPR absorbers, with 3mm thick steel plates
- covered with perforated wood groove panels from floor to ceiling, for a wall-to-wall uniform look

THE SIDEWALLS (axial mode target frequency of 50Hz)
- 50mm Rockwool (100kg/m3 density)
- vibration absorbing isolation wall bracket
- 12mm+ thick gypsum board (550kg+/m3 density)
- acoustic damping sheet (self-adhesive) applied in the center of the double drywall sandwich
- 12mm+ thick gypsum board (550kg+/m3 density)
- VPR absorbers, with 1mm thick plates
- covered with perforated wood groove panels from floor to ceiling, for a wall-to-wall uniform look

THE CEILING (axial mode target frequency of 40-50Hz)
- 240mm+ free air space
- 50mm Rockwool (100kg/m3 density)
- 15mm+ plywood (600kg+/m3 density)
- acoustic damping sheet (self-adhesive) applied between plywood and gypsum board
- 12mm+ thick gypsum board (550kg+/m3 density)
- VPR absorbers, with 1.5mm thick plates
> additionally, suspended ceiling bracket system housing a large canopy of solid wood 2D diffusers

 

[Lee]

UPDATE: new DC cables, and QuadStack DAC purchase

MSB Select Digital Director and Westminster Lab upgrade dc cables : The throne of MSB Select DAC secured!

The practice of replacing included accessories of hifi components with aftermarket ones is extremely common for audiophiles. How often are we using the included black colour generic powercords? How often are we using the icluded wallwart switching psu? ... etc There are many many more of...

www.whatsbestforum.com

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Congratulations!

 

[QuadDiffuser]

Congratulations!

Hey Lee, great hearing from you! How have you been since our April get-together in Alpharetta?

 

[Lee]

Hey Lee, great hearing from you! How have you been since our April get-together in Alpharetta?

Doing well thanks!

 

[QuadDiffuser]

Recently, I discovered that the suspended floor (in the rear 2/3 of the room) is NOT for isolating ground-borne vibrations from the loudspeaker cabinets, but rather for controlling and suppressing room nodes.

Well, gosh, darn it, am I being bamboozled?

Who here on WBF has ever heard of a 1/4 ton slab (estimated weight) "screed and steel mesh bass absorber", floating on the ground under the listening sofa? What sort of air pressure can possibly resonate this slab, and what might its resonance frequency be?

My guess is that something so massive cannot possibly be energized even the slightest bit by room node air pressure generated by a pair of loudspeakers playing at even insane volumes, as its resonance frequency must be in the single-digit range.

Thoughts?

Quoting a section of my post #74 (above):
[THE FLOOR
Four meters will be allocated to the speaker area, equal to ~38% of the room length, and the remaining six meters will be allocated to the listening area. The two sections of the floor will be physically separated - constrained-layer dampened, decoupled, floated, and grounded - sandwiching dissimilar energy-absorbing materials.

The speaker-area floor will be constructed with the following, starting from the RC structural floor substrate:
- 4mm+ high-density recycled rubber granule underlayment for under-screed/floating floor constructions
- 90mm+ high-density screed, with BRC mesh in the center for mechanical integrity/strength
- high-durability leveling compound
- perimeter decoupled from adjacent structures via sponge rubber strips + caulking

The listening-area floor will be constructed with the following, starting from the RC structural floor substrate:
- high density foam isolation strips (tall, providing vertical clearance), covered with steel C-channel support
- 50% of the space will be filled with 100kg/m3 Rockwool insulation, 50% of the space left as an air gap
- structural steel decking (thin)
- 45mm+ high-density screed, with BRC mesh in the center
- high-durability leveling compound
- perimeter decoupled from adjacent structures via sponge rubber strips + caulking

The loudspeakers (and subwoofers) will have a more solid/stiffer floor foundation from which they will launch their acoustic energy, but energy propagating through the floor will decay rapidly before it reaches the listening area.]

 

[MarkusBarkus]

@QuadDiffuser I do recall seeing plans/documentation regarding the isolation of a huge and elaborately engineered slab such as you describe. It was for a custom build. My take was it was to isolate and prevent outside vibration from entering the internal audio environment. I suppose it would impact vibrations generated by the audio system as well, but it does seem complicated. I am traveling, but will search my notes for the reference I noted above as post as possible. Cheers.

 

[QuadDiffuser]

This is by far the BEST YouTube video I've watched on the subject of optimizing room acoustics - Anthony Grimani's advice mirrors many of my own self-taught experiences from past decades!

While the design discussed on the video mostly optimizes requirements for multi-channel home theater, the takeaways for me (as it applies to two-channel audio) are:
0) The objective is to create an acoustic space which does not violate expectations of what's heard in nature
1) Bass CAN be over-damped; allow for some bass to slip into higher Rt territory, relative to the mids and highs
2) Sidewall treatment: can alternate between absorbers and 1D diffusors
3) The rear wall center should be absorptive, to attenuate L+R channel high-energy direct sound which typically subtracts from desirable rear ambience sound field
4) 15-20% coverage (of the 4 or 5 room surfaces) is adequate