Most important fundamentals in your built/modded listening room?

Great idea! Gotta figure out where that might be.

Leaving the ceiling exposed is a good option. I like the industrial ceiling look you can Google industrial basement ceiling might give you some ideas. If you know where your speakers will set you can build some diffusion into the exposed joists. 

Thanks -- a combination of boxing in some things within the ceiling and leaving other things exposed would be fine, especially if all is covered by a homogenous screen of some kind (fabric).

A redivision of the room is possible but depends on many other factors. We’ll see.

Your new room’s fundamentals look great.

I saw a house in my neighborhood with a gambrel roof (#8) and wondered, "Is that the perfect roof for audio?"

Great tool. Has more information than I have been able to absorb in this short time. In the past I have plotted modes for my room, though not accessed this program. My room that I will be moving into is 8.3 x 11.5 x 16.5 having the ratio of 1, to 1.3, to 2.0. Lower bass nodes are well distributed.

I agree that to keep the room size as large as possible while keeping the most ideal ratios, it would be best to leave the joist exposed and box in whatever plumbing is exposed using acoustic adsorption materials.  Thereby considering the 9' ceiling as the reference. 

Would is possible to divide the basement into 2 more equally sized room and accommodate your dedicated A.V objectives?

  

@mesch  Thanks so much. Let me be clearer about the space.

• The overall basement is 27.5 ft x 28 ft.
  • The room I'm thinking through is 27.5 ft. x 17 ft.
  • Let's call that Section A.
• The overall basement is cut in half by a long staircase, creating a second rectangle we might call Section B.
• Section B section is 27.5 ft. x 7.6 ft.
• It contains the staircase, a main electric panel, a sump pump, too.
• Section B has plumbing for a bathroom not in use, yet.
• There is no hot water heater or HVAC making noise, though. Very quiet.

One nice thing about the main panel being downstairs is that (a) it has open slots on it, (b) has capacity for dedicated lines, and (c) the dedicated lines won't have to go far to power the gear.

In a larger renovation, a couple years from now, we will move the staircase and get it out of that room entirely.

So, this post is about working through what to do to improve Section A. Yesterday, I spent many hours thinking about room dimensions. Alas, it is very hard to build the perfect sized room (Bolt-area-wise) within the room without messing up the re-sale potential of the home. I suspect that we will create a large media room that contains both listening and TV in it. That will be easy to sell.

So, I appreciate and can use your suggestions. Because it is not feasible to create a listening room within the larger room (as a set-off box in a box, so to speaker) there is greater need to get the ceiling height as high as possible to make the other dimensions easier to work with. That ceiling does have pipes running through it but I assume many of them can be raised up a bit to accommodate a slightly higher ceiling. (I suppose the rafters might have to poke through? Unsure.) Because if I did put double drywall or whatever under the current rafters, I wind up with a ceiling that is probably 7' 9" or so. And 8' 6" ceiling is way more forgiving.

Here's something close to the best I could hope for with 8'6" ceilings. https://amcoustics.com/tools/amroc?l=24&w=15&h=8.5&ft=true&re=OeNorm%208115-3%20musi...

That said, what I CAN do NOW is deal with the fundamental construction elements so as to tee up good sound later. Thanks for your help with that. 

@hide45  Regarding the ceiling, I agree one could leave it open. Might consider incorporating bass traps where ceiling meets walls. Maybe insulate some sections and cover with fabric as per MCs suggestion. Also spray a thin layer of closed cell foam insulation to round out edges where joists meet subfloor above. Basically having diffusion and some absorption installed into ceiling. Allowing for the 9' ratio reference.

I would mount TV flush to wall behind speakers. Maybe elevate it above speaker height. Cover with absorption products when not in use. Might frame it in for this purpose. 

If video electronics are not in use when music system is used then one dedicated line could be used for both. In your case the position of the dedicated outlets will need to be well thought out regarding topology of A/V systems. 

Just some thoughts, I am enjoying thinking on your project. 

When we finished our family basement in the early 1960's my father did not enclose the ceiling in order to avoid additional property taxes on "liveable space".

In Des Moines, @ the time, this was how it worked.

We instead sprayed the ceiling and ductwork with flat black paint and the open ceiling was not very noticeable.

DeKay

I had multiple goals.  I have a 50/100 Hz resonance in the room that needed treatment so I added GIK's 7" thick bass traps with diffusion panels on top. You don't have to go that thick, unless you lack where to put bass traps, but the GIK Impression panels are very effective and very affordable compared to the prices I have seen on some QRD types.

@erik_squires
I agree about diffusion. I’ve now gone the over-damped route and am seeing how to make my space "alive" without brightness. So...

I have two of these: https://images.app.goo.gl/rkE6t1jUgAMBoHCm7

QUESTION: How would you lay the GROUNDWORK for diffusion?

@mesch

Thanks for your reply. Some questions below. I will design the space for audio, once the kids leave. I’d probably just have a different amp for video, as I don’t want to run tubes for video all the time. I already own a Denon AVR and klipsch speakers for A/V. Maybe I’d ditch the speakers or put them on surround duty.

Insulate between joists with two layers of 6" insulation covered by 5/8’ drywall.

QUESTION: What kind of insulation? R38?

The 17’ dimension can be played with by furring out the concrete walls as desired. Insulate between wall material and concrete. Use 5/8" drywall for wall. Consider this the width. Frame in a cross wall to the desired length.

Given you are running Mono amps and a pre with digital source I would route 3 dedicated lines to the room for equipment, one to amps, one to pre, and one for digital front end.

QUESTION: If I had a separate set of components for A/V would you do 4 dedicated lines? That seems like a lot.

I would consider placing a equipment rack for sources and pre at one side of listening chair. Mono amps on stands where best suits.
Have nothing between speakers.

QUESTION: Makes it hard to have a TV, but I suppose if there’s a "false wall" it could hide the TV. Sound ok?

Room ratio is a tough one. If one looks at various ratios, some say 1 H x 1.67 W x 2.7 L (P.S. Audio) and that works out, with an 8 foot ceiling to 21.6 x 13.3 x 8. That amounts to reducing width by almost 4 feet and the length by 6 feet. Not sure how that will work for various purposes. This is why I was thinking to keep the ceiling open (without drywall) and have it at 9 feet. That way I could have a ratio of 9 x 15 x 24 as a target and just need to pull off the walls by a couple feet. Still, I guess once you start building out from concrete (one exterior wall) you can probably bump out pretty easily, eh?

So one thing I just discovered is the joy of diffusion.

I've heard well balanced rooms before, with a mix, but only recently have I been able to do A/B comparisons with and without them. 

If anything, incorporate diffusion into your planning as soon as you can.  They add air and shimmer without glare. 

Sounds like a great project and opportunity! You have been given much sage advice.

My approach would be to devote the space to audio, If wanting to add video, I would use my 2-channel system for it. Therefore devoting $$ to music as, I find that 2-channel can do wonders for video.  

Initially, I would pay attention to consideration of ideal ratios for a dedicated room. The Harley article discusses this. Consider the 8' ceiling to be 'fixed' and the reference. Insulate between joists with two layers of 6" insulation covered by 5/8' drywall. The 17' dimension can be played with by furring out the concrete walls as desired. Insulate between wall material and concrete. Use 5/8" drywall for wall.  Consider this the width. Frame in a cross wall to the desired length. Consider using the damping material between 2 sheets of drywall for this wall. Possibly only on the side of this wall interior to the audio room.

Given you are running Mono amps and a pre with digital source I would route 3 dedicated lines to the room for equipment, one to amps, one to pre, and one for digital front end. 

I would consider placing a equipment rack for sources and pre at one side of listening chair. Mono amps on stands where best suits. 
Have nothing between speakers. 

Enjoy!

Fantastic set of comments! I am copying these out into a list meant for a contractor. These ideas will be implemented. I hope there are more.

Some replies to you generous folks:

The room won’t have noise issues. Just master bedroom upstairs and my spouse is usually somewhere else in the house. No traffic to worry about.

Thus, regarding noise, my takeaway from the comments is that a modicum of noise reduction is in order, but no need to go crazy. I don’t think I need double walls, etc. Wall damp sounds great.

There are no moisture issues. Colorado is dry.

Electrical: dedicated lines for sure. Two should be enough, no? I have a fairly simple system but there’s a possibility of a home theater system down there, too. Perhaps put the stereo rig on one short wall and the home stereo on the other, with seating toward each in the center? So...three dedicated lines?

Regarding ceiling, this is a case where I might need to do something now and make a further decision later. Here’s why:

• The ceiling with drywall would be about 7’10" with the thicker sheetrock.
• The room is 27 feet long, but it could change when we continue a further basement and house renovation -- so, MC, for now, I suspect that leaving it at 9 feet with insulation and a fabric cover with sheetrock to be added later might make sense.
• Another person wrote to me that I might want to create a false wall at one end (shortening the length to about 25 feet) and have a place to put my electronics. That might help with the problem of "multiples" and also give a neatness to the space.
• I agree about not going crazy expensive.

In building, one of the factors that will influence your enjoyment of the room is the sound isolation you build into it -- assuming there is noise in adjacent areas. That was mentioned by others, with possible solutions. I’ll add a +1 to that. People talk about "noise floor" dropping after adding some gizmo that others can’t hear, but every dB of HVAC or traffic noise you keep out of the room is a REAL improvement.

I used solid-core wood doors with weatherstripping, then added seals from this company: https://www.soundproofingcompany.com/

The other side of the coin is that a room that is soundproofed will retain bass, so have strong peaks and nodes. Be prepared to add plenty of bass trapping and spend time positioning speakers and subs. Consider using multiple subwoofers and/or DSP in the deep bass.

Yes, install many outlets, with acoustic putty pads around the boxes so they don’t let noise through. As few wall penetrations as possible. I’d recommend skipping ceiling lighting, and use floor lamps.

Consider what to do about the HVAC. Can you run an oversized vent to minimize whooshing noise? If your system is noisy, would you be better with a "dead vent" not connected to the main system?

If you have a choice, face away from the windows. It is more relaxing. If not, and there is glare, you can have them tinted.

If you live in a damp climate, make sure you are taking adequate care about water vapor (and possibly water) that might seep through the concrete. Basement floors are a specialty. After some trouble, I wound up using needle-punched (synthetic felt) pad with synthetic carpet over it, which lets water vapor pass from the slab into the room air. In wet months, I run a dehumidifier.

Have the door to the room open OUT, in case the best listening position happens to be near the door. Shouldn’t happen with 27 ft length, but still....

I hope you wind up with a great room!

It could become very involved and expensive quick. You say 8 foot ceilings is there anything attached to the joists that can make it less? Wiring, plumbing, HVAC? You can double sheetrock or use something like quiet rock. Decoupling the sheetrock or quietrock from the studs and concrete with resilient channel. Insulate all walls and ceiling. Depends on how much soundproofing you want to do or can afford.

"...the garage as 18 outlets in it..."

Grow house.

8ft is fine. At 9ft the other dimensions are exact or very close multiples of 9. It is best to avoid dimensions that are the same or multiples of each other. There are always room modes but they are much worse when dimensions are exact multiples. 8x16x24 for example, if you could make it 9 that would be better. In your case making it 9 would make it worse.

If you want to spend money the sky's the limit. If you want to save money for where it will really matter, the single most cost-effective thing you can do by far is use 5/8" instead of 1/2" sheetrock. This costs almost nothing more, but blocks sound an additional 16dB. Walls framed with different studs to inner and outer walls can get you down around -20dB. 

You can go all-out and bring it down to recording studio levels. If you want to spend as much on this one room as the rest of your house. Or you can do the super effective but inexpensive. Highly recommend super cheap. Because what happens, there is a background level when you get quiet enough any tiny little thing you notice- and it doesn't blend into the background any more because there is no background any more. So it stands out. You would never notice the noise coming around the tiny little e gap under your solid core door until the weather-stripping leaves only that tiny little place for noise to come in.

You definitely want the solid core door. With weather-stripping. Either an exterior door, or an acoustic door which will be basically the same only maybe have the seal at the bottom which could be nice. Run one 20A line for the system. Run another for lights and spare outlets.

Sheetrock is well-known to be fairly resonant, behaving like a struck drumhead. Go to the website of Acoustic Sciences Corp, and check out their wall-damping and isolation products, particularly Wall Damp.

I've been in a room constructed with the ASC products (the Portland, Oregon music room of Audiogon member folkfreak), and was mighty impressed. Rapping the sheetrock walls with my knuckles produced a faint "tick" sound; a regular sheetrock wall makes a "tonnnk" sound.

Wall Damp installed between two sheetrock panels creates constrained layer damping, greatly reducing the sonic signature of the panels.

Electrical outlets, lots of electrical outlets. 

There was a recent article in Stereophile from Kongens Lyngby of Denmark where ceiling height wasn't the biggest concern regarding room modes.  That being said, I would focus on wall, floor and ceiling construction as being as stout as possible including double walls of sheetrock and sealing all cracks and voids.  Electrical should be pretty straightforward with dedicated electrical runs.  I helped my brother build his recording studio and it sounds very good with double wall construction and concrete floors with a floating wood floor above. 
https://www.gossardstudios.com/