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Best effort room and audio system build

Bugal1998

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12/16/2022 Edit: Pics added
10/18/2023 Edit: Pics updated

Hello ASR Friends!

This thread is to consolidate information and share the outcome of my room build for those who’ve expressed interest along the way. There are headings so you can read only what you're interested in.

Notes
  • I hired Nyal Mellor, owner/founder of Acoustic Frontiers for the layout and engineering aspects, including room layout, sound isolation, room acoustics, treatment plan, and site-built treatment designs. Out of professional courtesy and contractual agreement, I will not be sharing key details of his solutions. Suffice it to say, despite reading and studying sound reproduction and room acoustics as a hobby for years, this project is superior to anything I would have designed myself thanks to Nyal’s consultative approach and expertise; I recommend his services to anyone embarking on a best effort project
  • This is a work in progress. The seating, lighting and wiring is temporary; wires will be hidden, fabric wrinkles fixed, lighting optimized, subwoofers covered, etc., etc.
  • The camera does not capture the lighting (at all). In person it’s welcoming, sets the mood for all types of music, and aids the immersion… in photos it just looks… bad. Please be kind ;)
The room’s location is a slightly irregularly shaped basement space with concrete floors, and three out of four concrete walls, with the main bedroom above. The fourth wall was built as a double-stud wall, and houses the dual 1.75” MDF slab communicating doors with seals (seals not yet installed). Other than the bedroom above, the only bordering rooms are a home gym and a mechanical room. Rough unfinished dimensions were approximately 32’Lx20’Wx9’H.

Project Priorities

In order of importance:
  1. Music performance using 2-channel w/subs (If needed, I would compromise anything else before sacrificing 2-channel performance)
  2. Video performance (Projector/retractable screen installation will be a future phase)
  3. Surround sound performance (surround speaker installation will be a future phase)
  4. Appearance (Room performance was to be maximized, and then I would figure out the aesthetics)

Due to the bedroom above and a desire for continued marital harmony, sound isolation was also a key design consideration; Nyal’s isolation recommendations have exceeded my expectations in real-world performance by a wide margin. I can listen to bass heavy music at any level I care to listen at for an entire song, and my wife’s sleep is not disturbed. Short but loud demos might be disturbing upstairs, but thus far she has never heard anything.

My priorities for audio system performance were:
  • Neutrality/accuracy
  • A lively dynamic presentation with practically unlimited output
  • Bass accuracy/output/extension
  • Precise stereo imaging and envelopment
  • And ultimately, No Mo’ FOMO!!!

Gear Selection
  • JBL M2s (Dual I-tech 5000HDs)
  • Four JBL 5628 subwoofers for the audible spectrum (I-tech 3500x4HD ~2500 watts/cab, 4000 watts peak)
  • Four Stereo Integrity IB-24s in an infinite baffle arrangement for infra-sonics (I-tech 5000HD producing ~1250 watts/driver)
  • JBL SDP-75 for processing
  • BluOS for streaming and a CD player (both connect to SDP-75 using digital outputs)
I've auditioned many different speakers over the past 10-12 years, and ultimately settled on the M2 as offering the most balanced set of traits compared to my preferences. I haven't heard the latest Genelec 'The Ones' series, Kiii Audio's offerings, Dutch & Dutch, Neuhmann, etc. No, I don't believe I have the best speakers in the world, they're simply my preference among speakers I've experienced, and I no longer feel any need to continue searching. Of course, my auditions weren't blind, not all rooms were equal, and not all speakers were optimally setup... and any one of those variables could have altered my choice.

All A/V equipment is located outside of the theater in a (yet to be installed) AV rack, so fan noise is a non-issue.

Room Construction

All walls and ceilings are floating via metal spring or rubber isolation mounts (per specifications provided by Nyal; See Acoustic Frontiers guide to bass e-book for more info) to reduce bass resonances and provide acoustic isolation. Concrete walls are a single layer of 5/8" Soundbreak Board, and other walls and ceilings are multiple layers with damping compound. Soundbreak board was a miscommunication with the contractor, but I appreciate the extra isolation.

The rear ~1/2 of the room floor is a 12" riser that functions as a bass trap, along with the entire front and rear walls serving as bass traps/mid-high frequency reflectors, with engineering and design provided by Nyal.

The final finished room dimensions are ~28'x19'x8.5', with a combined ~4' taken by the front and rear false walls, giving an apparent size of ~19'Wx24'D. The 4'Dx 13'Wx 8.5'H irregularity in the rear of the room became a very large subwoofer enclosure with 2x6 construction and multiple layers of 3/4" plywood and a vibration cancelling manifold to hold the four Stereo Integrity IB-24s for infrasonics.

The four JBL 5628 subs are built-in to each corner of the room for even seat-to-seat bass response. I plan to perform MSO in the coming weeks (implemented with the built-in Crown amp DSP). Once the covers are built, the only visible speakers will be the M2s up front.

FYI, Nyal asked if I was willing to dig out the front of the room floor instead of building a rear riser, which would also increase the ceiling height over the listening position... that was a bridge too far, and I believe the only significant suggestion he made that I declined to implement.

HVAC

HVAC has variable static pressure to avoid over/under conditioning the space based on occupancy; max flow was the design criteria for HVAC noise thresholds, and then the CFM can be decreased since I seldom have 8+ people in the room. HVAC inlet and outlet have muffler boxes, and the ducts/grills are large to avoid turbulent flow noise. HVAC is barely audible when running with an otherwise silent room; any sound (conversation or music) immediately masks the HVAC and you need a quiet room to tell if it's running or not... Not a Skywalker Ranch scoring stage, but wonderful for recreational listening.

Acoustics

Acoustic treatment is a mix of diffusion and absorbsion. Sidewall early reflections are diffused. RT60 (per Trinnov) of the untreated room (but with the rear riser and front and rear false wall bass traps in place) was 0.74 seconds, with treatments installed 0.51 seconds, and with two giant bean bags chairs 0.39 seconds. The rooms sounds great either way, but I prefer the sound without the bean bag chairs. Leather chairs in the future may bring the RT60 back up a bit.

Appearance

I wanted to capture the vibe of a live performance space or a small music hall to add to the atmosphere of the musical experience. I would say it was a success, because nearly every person who has entered the room has said or asked some variation of 'would you ever have a real band play in here?', 'do you have band? do you play in here?', or 'it looks like a band should be on the stage'. I'll call it a success.

The vibe was created with white oak hardwood floors with black stain, matte black ceiling, black brick veneer on the sidewalls, exposed vertical 1x6 boards (in cabinet finish black) forming the front and rear false walls and then extending them onto the sidewall of the stage; all exposed fabric is also black. The sidewall acoustic panels are framed in and will eventually be covered in fabric. The brick is lit in high relief by RGB tape lighting. The ceiling perimeter also has RGB tape lighting and I've added front and rear RGB wall wash lighting along with wash lighting for the L/R speakers. Without the RGB lighting the black is oppressive, with the lighting it's a total escape.

Oh, and the M2s have a custom candy apple electric blue automotive finish (they were damaged in shipping and this was the solution).

Pictures
JGPhoto-HellingsBldrs-Day-9901.jpg

(Top photo by Jay Greene Photography)

20230904_193715.jpg

(This photo most representative of what the eye sees)

Other photos attached show the acoustic treatments and early test lighting.

Miscellaneous
  • Front LCR locations each have two extra runs of 12g speaker wire, RCA cable, and XLR cable to allow easy in-room testing or demoing of other speakers. Is double-blind, level matched, ABX speaker testing in my future, just for fun? Maaaaaaybeeee...
  • In the future, the L/R speakers will be on rails to slide between the 2-channel and theater positions
  • A pass-through port is installed from the A/V Rack to front-side wall to allow pass through of calibration microphone wires (Omnimic and Trinnov); capped off when not in use. Allows room measurements and noise floor measurements without the door open or laptop noise in the room
  • In-ceiling speaker boxes and surround sound speaker wiring is pre-installed/pre-run, projector hushbox and ventilation is pre-installed, HDMI and fiberoptic cable runs pre-installed to hushbox and front-of room for future expansion. Conduit access is pre-installed to hushbox, rear wall, front wall, and side soffit for future expansion. Cat6 runs all over the room for future expansion. Retractable screen wiring pre-installed. Low voltage wiring for final RGB lighting is pre-installed

In-Room Measurements

Coming soon... [what measurements would anyone like to see?]

Note that I prefer to use Omnimic due to ease of use. That said, I could possibly be persuaded to reengage with REW since I'll need it for Multi-Sub Optimization

Bass is flat to ~6.5hz. I don't know how much output is available, but there was no change in frequency response even at 117db with pink noise... I didn't care to push it any louder.

Subjective Results

I'm happy. Very happy. The low noise floor of the room has allowed the reverb and ambiance of tracks to really shine. Even with only a rough calibration (no MSO), the bass is tight, deep, and articulate... it's almost like it isn't there, even though it's there in abundance! Stereo sounds are wide and enveloping on many tracks, coming out to nearly the 180 degree position. Some tracks have reverb that comes from the sides, up high, and even behind the listening position. Stereo placement of sounds is precise all across the front sound-stage including well beyond the speakers, and yet the sound can be enveloping at the same time. There are even height and depth sensations; family and friends generally report the same shared spatial perceptions when asked--with no leading suggestion--what they're hearing and where.

One guest said it best, 'the walls and ceiling of the room don't exist, the speakers don't exist, sound just originates from nowhere and extends without limits until fading out, except for the singer, or certain sounds, or key instruments, which all have very precise locations'.

I do NOT like Harman's new curve supplied with the SDP-75; I find it dull, lacking in spaciousness, and lacking in vocal clarity. I don't know what the target room acoustic conditions are for their new curve, but my room isn't it.

The transition to the infra-sub is perceptually seamless, and most of the time it does very little... but the tracks that use the infra-sub just wouldn't be the same without it.

I wouldn't change the overall set of trade-offs I have now with the more lively room for the overdamped rooms I'm used to, however, it is a trade-off. The over damped rooms have an extra level of clarity that would be appealing for content creation, the sound seems bigger and closer and more imposing (in a good way!) due to the lack of early reflections, and good recordings with intentional spatial cues can be a tad more impressive with more depth coming out into the room or behind the speakers. However... The exceptional studio recordings are very nearly as impressive in the more lively space, yet many other recordings become much more impressive. And poor recordings are more listenable in the lively space. The damped room exposed every facet of each recording's acoustic space, and each track has it's own sonic fingerprint... the more lively room adds just a touch of 'sameness' to all tracks. But overall, I much prefer the more lively listening space for overall enjoyment. Much to my personal surprise, I'm finding I agree with the conclusions of the research shared by Floyd Toole when it comes to the impact of early reflections. :)

I'm also finding that some of the M2s positive uniqueness is reduced in the more lively space... I certainly don't like them any less, but I also don't find them as distinguished as before; how much of a role did room liveliness (or lack thereof) play in my speaker selection process? I'll probably never know (and don't really care), but I do wonder.

I'll share other random subjective observations in the reserved second post over time.

Thanks for reading... happy to answer questions if there are any!
 

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Bugal1998

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Reserved
 

sarumbear

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Hello ASR Friends!

This thread is to consolidate information and share the outcome of my room build for those who’ve expressed interest along the way. There are headings so you can read only what you're interested in.

Notes
  • I hired Nyal Mellor, owner/founder of Acoustic Frontiers for the layout and engineering aspects, including room layout, sound isolation, room acoustics, treatment plan, and site-built treatment designs. Out of professional courtesy and contractual agreement, I will not be sharing key details of his solutions. Suffice it to say, despite reading and studying sound reproduction and room acoustics as a hobby for years, this project is superior to anything I would have designed myself thanks to Nyal’s consultative approach and expertise; I recommend his services to anyone embarking on a best effort project
Well done for hiring a professional acoustician!

  • Four JBL 5628 subwoofers for the audible spectrum (I-tech 3500x4HD ~2500 watts/cab, 4000 watts peak)
  • Four Stereo Integrity IB-24s in an infinite baffle arrangement for infra-sonics (I-tech 5000HD producing ~1250 watts/driver)
This is serious low frequency capability! By simple piston displacement to SPL calculation you get 140dBSPL at 20Hz and 120dBSPL at 10Hz. Enough to produce brown notes :D

Acoustics

Acoustic treatment is a mix of diffusion and absorbsion. Sidewall early reflections are diffused. RT60 (per Trinnov) of the untreated room (but with the rear riser and front and rear false wall bass traps in place) was 0.74 seconds, with treatments installed 0.51 seconds, and with two giant bean bags chairs 0.39 seconds. The rooms sounds great either way, but I prefer the sound without the bean bag chairs. Leather chairs in the future may bring the RT60 back up a bit.
Excellent figures...

You have a great place, enjoy it. Just make sure that you do not get carried away and listen at unhealthy levels too long.
 

Adi777

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  • Four JBL 5628 subwoofers for the audible spectrum (I-tech 3500x4HD ~2500 watts/cab, 4000 watts peak)
  • Four Stereo Integrity IB-24s in an infinite baffle arrangement for infra-sonics (I-tech 5000HD producing ~1250 watts/driver)
I wonder if I could do the same for myself.
 
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Bugal1998

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I wonder if I could do the same for myself.
Perhaps!

What are your room dimensions?

Would you do a true infinite baffle sub? Or a psuedo IB setup (like mine) that doesn't vent to atmosphere but provides a large box volume per sub?

And how would you manage the crossover and integration?
 
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Bugal1998

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Well done for hiring a professional acoustician!


This is serious low frequency capability! By simple piston displacement to SPL calculation you get 140dBSPL at 20Hz and 120dBSPL at 10Hz. Enough to produce brown notes :D


Excellent figures...

You have a great place, enjoy it. Just make sure that you do not get carried away and listen at unhealthy levels too long.
Thanks for the comments and observations!

Indeed, hiring an acoustician was well worth it (music to your ears I suspect :cool:). I'm smart enough to know when I'm not... you know... smart enough. The bass output is impressive (overkill for what I intended), but I'm even more struck by the transparency of the bass; I never imagined bass could be 'transparent', but that's how I perceive it.

That's good advice on the listening levels... I take hearing preservation seriously, and I don't usually listen at elevated levels. I periodically use Omnimic to track my "A weighted sound exposure" which treats exposure to 85db beyond 8 hours as harmful; I was pleased to see that my accumulated exposure during a 30 minute session was typically under 5 minutes. Thanks to a very quiet room, I find much of the music I listen to sounds best in the 75-82 dbA range, and often the lower-end of that range.
 
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Adi777

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Would you do a true infinite baffle sub? Or a psuedo IB setup (like mine) that doesn't vent to atmosphere but provides a large box volume per sub?

And how would you manage the crossover and integration?
I don't have idea.
When you have 2 systems with subwoofers, one for the lowest frequency and one for higher frequency, that is better? Better quality?
I think, the easiest way is buy or make DIY subwoofers - 4 pieces, and put then in the best place and that's it.
The question is, what's the best.
 
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Bugal1998

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I don't have idea.
When you have 2 systems with subwoofers, one for the lowest frequency and one for higher frequency, that is better? Better quality?
I think, the easiest way is buy or make DIY subwoofers - 4 pieces, and put then in the best place and that's it.
The question is, what's the best.

I implemented the crossover between the infra-sub and the main subs in the crown amps. I haven't dug into phase response at the crossover point, but the amplitude summing is great and sounds seamless.

I won't pretend to know what's "best", and yes, four subs in optimal locations would be easier. But I will share what led me to this path. I...
  • Didn't want to compromise one part of the bass spectrum for another
    • Didn't want a pipe organ sound from my subs
      • My first large subs had a pipe organ resonance on every note that couldn't be unheard once you recognized it
    • Didn't want a thick or heavy sound in the audible range (by some reports this would rule out JTR)
    • Wanted tight punchy mid-bass and authoritative and deep sub-bass (by some accounts these can be at odds)
    • Wanted effortlessness
  • Wanted passive subs with amps in the rack
    • Didn't want to have to ship an entire sub, or disassemble a sub if something broke, or be stuck with a paper weight if a proprietary amp was no longer available, etc.
    • Didn't want to run electrical circuits to every sub location
    • Didn't want to move subwoofers around to access phase/crossover/level controls
  • Wanted the fewest platforms for controlling amp settings and DSP
    • Harman Audio Architect and Trinnov fit the bill
  • Wanted to control my expenditure and didn't have the time (full-time job, new baby, etc.) or space for a DIY build
Other factors...
  • The cove in the rear of the room was getting blocked off with a wall anyway, so it was minimal effort and expense to turn it into a large subwoofer enclosure... and the Stereo Integrity IB-24s offered excellent infra-sonic performance for the price (especially with a multi-unit discount)
  • I found the 5628s from an online wholesaler for less than 50% of retail... shipped!
    • Ordered a test unit to audition before taking the plunge on all four units
  • All of my Crown amps were purchased used as low hour units for 20-30 cents on the dollar (Crown has a fixed price repair cost of ~$500, so the savings was well worth any risk when distributed across multiple units)
  • The 5628s would still have meaningful output at the lowest room mode to even out the frequency response across seats
  • Splitting the amplifier load and cone excursion demands between different amps/subs was also a possible benefit for amp/speaker headroom and fidelity
Probably no right or wrong approach; but given the factors above, this was the path I chose... and it worked!
 
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Dan

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Awesome. I love how well thought out it is instead of some of these audiophile rooms with 100,000 dollar speakers stuffed into corners but they have cable risers so everything's awesome.
 
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Bugal1998

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Awesome. I love how well thought out it is instead of some of these audiophile rooms with 100,000 dollar speakers stuffed into corners but they have cable risers so everything's awesome.
:eek: I totally forgot to budget for cable risers!

Haha thanks, @Dan!
 
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kemmler3D

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This is badass, you love to see it.

Bass is flat to ~6.5hz.

That sounds like victory to me.

I would love to see it with normal lighting though. It's hard to make out the details with the high-contrast low-lighting you have in the pics.

The diffusers (?) look really interesting, not your 70s era QRDs for sure. Do you know the technical basis for their shapes? I have seen similar here and there, but I don't claim to understand how they work.
 
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Bugal1998

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Very Cool! Where are these IB-24s in the pictures?
They're hidden behind the rear false wall. The area between the rear wall diffusors is the primary path for the IB sound to enter the room.

I've attached pics from behind the false wall during construction.
 

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Bugal1998

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This is badass, you love to see it.



That sounds like victory to me.

I would love to see it with normal lighting though. It's hard to make out the details with the high-contrast low-lighting you have in the pics.

The diffusers (?) look really interesting, not your 70s era QRDs for sure. Do you know the technical basis for their shapes? I have seen similar here and there, but I don't claim to understand how they work.
Thanks!

Pics attached (pardon the dust). Still very much in progress with temp lighting, seating, exposed wires & acoustic treatments, etc., etc., etc...
  • Info on the white diffusors (Art diffusor Model D) can be found here; there are some technical writeups on the mathematical processes applied to create the shapes, along with test results available on their website.
  • The black wave diffusors are from Acoustic Frontiers, though they appear to the eye to be a 12"x12" version of the Aeolian Diffuser
  • Info on the curved diffusers in the front of the room (Acoustic Geometry Medium Curve Diffusor) can be found here

I don't know what modeling and magic led to the placement of each product type in the room, but the results are outstanding.
 

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