My dedicated audio room build - QuadDiffusor's Big Dig

[MarkusBarkus]

...cool stuff @QuadDiffuser

Did you find a good source for the pellets? I dove into this a few years back and ran into a dead-end for a source. And shipping was brutal.

 

[adyc]

Bass Traps - many!

Between the reinforced concrete structural wall and the 27.5mm thick gypsum "sandwich" (12.5mm Sheetrock + 2.5mm damping sheet + 12.5mm Sheetrock), the air space/gap distance (partially filled, with 50mm Rockwool, to maximize frictional losses) will be the following:

Front/Back walls: 100mm
Left/Right walls: 50mm
Ceiling: 200mm

These structures will be one of many other ”bass traps", the others being suspended/damped metal plates, and (very likely) the floor slab below the seating area, as well as activated carbon pellets filling the voids inside the P-17 and P-23 QRDs.

Have you considered distributed bass arrays in addition to bass traps? With all bass traps, the bass response is still unknown unless you actually measure the room after construction. My point is you maybe wasting too much money on bass traps. Lots of bass traps are no guarantee to flat bass response.

 

[QuadDiffuser]

ROOM NODES - axial

The dimensions of the structural walls are being finalized, likely to be fixed into the dimensions entered into the AMROC calculator below; note that the primary axial modes (yellow highlights) are predicted to be 35Hz, 40Hz, and 48Hz. Hence, the room's bass treatment solutions will be targeting these three fundamental frequencies.



By successfully attenuating these fundamental room node frequencies, my guess is that the post-treatment room response will resemble that of an elongated/widened room dimension. Just for the sake of experimentation, I've entered into the AMROC calculator (artificial) room dimensions which have been increased by 10% in length, width, and height. The results are excellent in all parameters, suggesting that bass articulation and reproduction will be superb.

 

[QuadDiffuser]

Sub-bass Absorption, via gypsum "sandwich" wall treatments

Bass absorption of the L and R side walls, using a 50mm gap (0mm air + 50mm Rockwool) will be extremely effective for the (predicted) 48Hz axial room mode.


Bass absorption predicted for the front/back walls using a 150mm gap (100mm air + 50mm Rockwool) will be extremely effective for the 31.5Hz octave, and can be fine-tuned (with slightly less air gap?) to address the (predicted) 35-40Hz axial modes.

 

[QuadDiffuser]

Sub-bass Absorption, via metal plates

I've decided to skip the heavier 2mm and 3mm steel plates which will require very high corresponding SPLs to become energized, and instead, standardize to just the 1.5mm metal plate (green trace, below), predicted to have a broader "Q" to address peak frequencies between 30-60Hz. Also, the very good news is that the metal plate bass traps, due to their "freely suspended" spring-loaded L-brackets, will enjoy air-flow around/behind the plates, to extend absorption to 200Hz (and thereafter, smoothly diminishing), much like the RGP Modex plate (specs shown below).

 

[QuadDiffuser]

Have you considered distributed bass arrays in addition to bass traps? With all bass traps, the bass response is still unknown unless you actually measure the room after construction. My point is you maybe wasting too much money on bass traps. Lots of bass traps are no guarantee to flat bass response.

Hi ADYC,
I've started from the position of neutrality with as little bias as possible, and have been repeatedly reviewing the cost, rationale, and specifications for ALL of the proposed room treatments, sharing my research and journey with everyone here on WBF. As the world is so full of "maybes" (plural), I'm being deliberate, as it's my money and time. So far, the logic and science of my iterations have been holding up quite well, ie. the bass traps can be both broadband and specific, depending on their intended performance requirements. You're welcome to challenge my assumptions and conclusions - please help by being more specific with your suggestions. ;-)

 

[adyc]

Hi ADYC,
I've started from the position of neutrality with as little bias as possible, and have been repeatedly reviewing the cost, rationale, and specifications for ALL of the proposed room treatments, sharing my research and journey with everyone here on WBF. As the world is so full of "maybes" (plural), I'm being deliberate, as it's my money and time. So far, the logic and science of my iterations have been holding up quite well, ie. the bass traps can be both broadband and specific, depending on their intended performance requirements. You're welcome to challenge my assumptions and conclusions - please help by being more specific with your suggestions. ;-)

DEBRA – James Romeyn

jamesromeyn.com

 

[QuadDiffuser]

I'm working on optimizing room acoustics - the subject of loudspeaker choice, bass arrays, active bass equalization, etc. is another topic altogether, and I'm not there yet. BTW, I've browsed through the jamesromeyn.com website, and like many other audio component manufacturers, it's basically an informercial, citing many generic problems of bass reproduction in a typical room, then posturing their product as the "solution". Sorry, not for me.

 

[Lee]

Have you talked to Art Noxon at ASC? He did a fantastic job on Robert Harley's listening room.

 

[QuadDiffuser]

Hi Lee, I have not spoken with ASC's Art Noxon (yet), as my basement listen room already incorporates what's in Robert Harley's room (from 10+ years ago). But I have been very active in doing research, and reaching out to select room treatment module makers and acousticians to explore possibilities for their products/services.

 

[QuadDiffuser]

A very educational and important video on the physics of metal plate bass absorbers from RealAcoustix.com's Richard Lenz, presented by John Brandt.
My takeaways are:
1) its size should be as large as possible, to increase the probability of good coupling with the very long wavelengths of sub-bass frequencies
2) separation between units of at least 1m, to minimize edge-effect interactions (dictated by fluid dynamics)
3) room nodes are composed of primary, as well as secondary and tertiary frequencies (consisting of multiples of the primary frequency); treatment of any of them will benefit reduction of others, hence treating a diversity of frequencies can be beneficial
4) be very careful of corner installations - avoid coverage of triple boundary corners, and place the metal plate a few meters (if possible) away from the corners

 

[pjwd]

A very educational and important video on the physics of metal plate bass absorbers from RealAcoustix.com's Richard Lenz, presented by John Brandt.
My takeaways are:
1) its size should be as large as possible, to increase the probability of good coupling with the very long wavelengths of sub-bass frequencies
2) separation between units of at least 1m, to minimize edge-effect interactions (dictated by fluid dynamics)
3) room nodes are composed of primary, as well as secondary and tertiary frequencies (consisting of multiples of the primary frequency); treatment of any of them will benefit reduction of others, hence treating a diversity of frequencies can be beneficial
4) be very careful of corner installations - avoid coverage of triple boundary corners, and place the metal plate a few meters (if possible) away from the corners

I think this just proves they are the wrong traps to use in corners

 

[QuadDiffuser]

Phil, it’s not - there’s a wrong way, and a right way for corner placement.

 

[pjwd]

Phil, it’s not and absolute - there’s a wrong way, and a right way for corner placement.

Quite true .... although I am a big fan of targetting corners first and then see what else is needed.. it seems a more efficient method .. at least for cobtroling reverberation times

 

[QuadDiffuser]

SPEAKER CHOICES

Perhaps it's not too early to start daydreaming about component choices for my future basement listening room scheduled for completion in 24 months' time.

I'm a huge fan of linear, predictable, objectively measured (PROVEN) wide off-axis polar response, combining point-source approximation to create a deep/wide soundstage, dynamically scalable (from tiny, small, medium, large to off-to-the-side, depending on what the source) pin-point 3D imaging by WORKING with room acoustics (for the mid/highs) and floor/wall boundaries (for natural augmentation of sub-200Hz long bass wavelengths).

My preference is for vertically aligned dynamic drivers on an appropriately contoured and minimized baffle surface area, with tweeter(s) on top, ideally at ear-height or slightly higher to project a slightly elevated soundscape, and the midrange placed below at very close proximity to the tweeter, ideally within 1/2 the crossover frequency wavelength to minimize deleterious interactions.

I'm not a fan of M-T-M D'Appolito arrays, as I can easily hear driver nulls which among other undesirable polar inconsistencies, separate music into vertical layers of horizontalized donut "rings". I also don't care about "time alignment" through second-order crossovers or voice-coil alignment into a common horizontal plane and vertical line. Anyone who can read a step-response curve knows that propagated sound arrives at different times THROUGHOUT the frequency range, and that achieving perfect time alignment at the listening position is but a misguided dream, and more importantly, our listening ear/brain mechanism is not particularly sensitive to group delay.

Dipoles, and monopoles will not be on my list either, as I have found them to not localize sonic events sufficiently solidly in 3D, especially in the front-to-back Z axis.

Nope to line arrays too, as their hyper-tall cylindrical propagation pattern warp both micro and macro sonic events inside the soundstage in ambiguous and strange ways, including instances where instruments and voices become stretched vertically into the full floor-to-ceiling length of the line-arrayed drivers, morphing into wildly different heights depending on the listening height (between sitting straight-up and slumping down), reminding me of a scene in the movie "The Thing" where the dysmorphic monster towers up/down on its long neck, except that sonically, the ENTIRE neck becomes a vertically-stretched vocal source. I know... pretty bizarre and scary, right?

I prefer my vocals to be right-sized, but also able to size dynamically depending on the gender/vocalist, most of all emanating from a real-sized head as I move around up/down/L/R around the proverbial sweet spot.

View attachment 110498

Applying DSP correction to "time align" arrivals isn't my taste either, as it introduces off-axis anomalies which suck the life out of music, according to my experience experimenting with the one of the most sophisticated room correction equipment featuring a mic array with four microphone capsules (to capture vertical azimuth data).

As far as I know (and heard/seen), only offerings from Von Schweikert Audio provides the adjustability and flexibility to optimize its acoustic output to optimize various loudspeaker placement locations, and room size/volume - attributes which are unique in the marketplace... I'm a HUGE fan of VSA!

But I'm casting a wide net out of an abundance of curiosity, and earmarking flagship models from multiple manufacturers (listed below in alphabetical order) for auditioning in an optimized-room-acoustics listening room to properly showcase the capabilities of the loudspeaker. Given the excitement and media coverage at High End Munich 2023, some European brands which I have not auditioned extensively have been added below.

Have I missed any others, which broadly deliver on the performance characteristics I'm looking for?

* * * * *

Magico (upcoming M7/M8 incorporating trickle-down technologies from the M9)
Marten (audition pending)
Rockport (Lyra - audition pending)
Von Schweikert Audio (Ultra 7 or 9 + pair of high-level input bass-management subwoofers)
TAD (co-axial drivers, ie. Reference 1-TX)
Vimberg/TIDAL (auditions pending)
Vivid (upcoming flagship model, one slot above the Giya G1 Spirit)
Zellaton (audition pending)

I've added the Monitor Audio Hyphn to my list of potential loudspeakers to audition and purchase, as it incorporates many of the attributes I'm seeking (co-axial drivers approximating a point-source, constant/linear hemispheric directivity, crossover absence in the critical broad midrange octaves, design and execution congruent with psychoacoustics, temporal coherency via driver/time alignment, etc.). A pair will soon become available for audition in my town, so I'm very excited! ;-)

Apart from the worrisome resonance at 2.8kHz, the rest of the frequency spectrum looks good. I'm also curious about the linearity of the off-axis response, especially in the rear hemisphere, but I guess the proof is in the listening.

Monitor Audio Hyphn Loudspeaker

They started out as a Concept, and have become a reality combining a skeletal form and novel engineering solutions – but do they sound as other-worldly as they look? As safe bets go, that you've never seen anything quite like the £70k Monitor Audio Hyphn speaker is pretty much a dead cert. Yet...

www.hifinews.com

All new Monitor Audio Concept 50 Time-Aligned Loudspeakers : Sound Of The Highest Fidelity

These Concept 50's will be coming to market sometime in 2023 priced at around $50K a pair https://www.monitoraudio.com/concept-50/ https://essentialinstall.com/news/home-cinema/audio-av/monitor-audio-high-end-munich-loudspeaker/ More info here

www.whatsbestforum.com

 

[QuadDiffuser]

It’s been a while. The concrete for the basement walls are (finally) being poured/casted during the next week.

 

[QuadDiffuser]

I've added the Monitor Audio Hyphn to my list of potential loudspeakers to audition and purchase, as it incorporates many of the attributes I'm seeking (co-axial drivers approximating a point-source, constant/linear hemispheric directivity, crossover absence in the critical broad midrange octaves, design and execution congruent with psychoacoustics, temporal coherency via driver/time alignment, etc.). A pair will soon become available for audition in my town, so I'm very excited! ;-)

Apart from the worrisome resonance at 2.8kHz, the rest of the frequency spectrum looks good. I'm also curious about the linearity of the off-axis response, especially in the rear hemisphere, but I guess the proof is in the listening.

Monitor Audio Hyphn Loudspeaker

They started out as a Concept, and have become a reality combining a skeletal form and novel engineering solutions – but do they sound as other-worldly as they look? As safe bets go, that you've never seen anything quite like the £70k Monitor Audio Hyphn speaker is pretty much a dead cert. Yet...

www.hifinews.com

All new Monitor Audio Concept 50 Time-Aligned Loudspeakers : Sound Of The Highest Fidelity

These Concept 50's will be coming to market sometime in 2023 priced at around $50K a pair https://www.monitoraudio.com/concept-50/ https://essentialinstall.com/news/home-cinema/audio-av/monitor-audio-high-end-munich-loudspeaker/ More info here

www.whatsbestforum.com

Auditioned a pair in white at Dynamic Audio (Akihabara, Tokyo) in early March. Very novel aesthetic, but its prominent on-axis emphasis right at the ear’s most sensitive 3k region added a persistently excitable layer of grit, and their off-axis cliff-dive in high frequency response, have taken them out of contention.

Onto Munich High End 2024 in May to audition other prospects!

 

[QuadDiffuser]

SPEAKER CHOICES

Revisiting my speaker audition list!
Lurkers - any others which I should be adding? ;-)

NEW/updated (listed alphabetically):
Magico M7
Marten (audition in Munich)
Rockport (Lyra - still unable to audition properly, grrr)
Von Schweikert Audio Ultra9 (mk2?) + pair of high-level input bass-management subwoofers
TAD Reference 1-TX
Vimberg/TIDAL (audition in Munich)
Vivid Moya 2 (trickle-down from the M1?)
Zellaton (audition in Munich)

OLD (from 2023-May):
Magico (upcoming M7/M8 incorporating trickle-down technologies from the M9)
Marten (audition pending)
Rockport (Lyra - audition pending)
Von Schweikert Audio (Ultra 7 or 9 + pair of high-level input bass-management subwoofers)
TAD (co-axial drivers, ie. Reference 1-TX)
Vimberg/TIDAL (auditions pending)
Vivid (upcoming flagship model, one slot above the Giya G1 Spirit)
Zellaton (audition pending)