Dedicated listening room design


I've been searching this site for how to create a decent listening room, but there's so much it's difficult to whittle down what's really useful and/or correct from what's not. I say decent because I don't believe I have the time or $$$ to create a balls-out perfect room, so I'm trying to at the very least avoid making any major mistakes that would be hard to correct.

As per recommedations I ordered Get Better Sound and Everest's Master Handbook of Acoustics to get some ideas and learn some of the fundamentals, but any further resources you guys could recommend would be much appreciated. Also, any specific materials/products you used for walls, ceilings, floors, lighting, etc. that work particularly well would be very helpful, as well as any installation techniques/materials to optimize their performance (sound absorption, soundproofing, noise/rattle avoidance, etc.). My room is in a medium-sized, open basement that will also be serving as a laundry room and exercise room, and I'm basically starting from scratch as I'm installing french drains (damned hurricane) and re-doing heat pipes so all the walls will be coming down in the process. I already have two dedicated lines (with the help of some folks on this site) and will likely add a third, so that part is pretty much covered.

Anyway, I hope that's enough to go on, and any thoughts or hard-won experience you could share would be most appreciated.
soix

Showing 3 responses by kevinzoe

Soix - I was in your shoes about 5 years ago. Exciting times and certainly enought to learn that will take some time to digest and internalize.

Using my basement 2-channel room as an example, here are some of my learnings:
* use a solid core exterior door to keep sound inside the room
* HVAC: I used a round flexible tube with sound insulation on the inside. You want to install it in such a way that there are several near-90 degree bends in it to prevent sound from traveling back to the furnace and up through the rest of the house. Also, baseboard heaters are dead quiet as another option.
* Lighting: don't use dimmers! They hum and your stereo system will pick it up. Instead use lights that work on 120volts (assuming you're in North America) and that don't use a transformer which can introduce humm.
* use J-molding and an acoustic sealant between the ceiling and walls so that if the walls move they don't transfer energy to the ceiling and vice versa.
* your wall-to-wall carpet will absorb much high end energy so you will need to pay attention to how you treat your room's surfaces so as not to create a dead sounding room with low reverb time for middle and high frequencies. Try using reflection (i.e. bare wall) and diffusion for middle and upper frequencies and absorption for bass frequencies.
* get a Dayton Audio Omnimic or XTZ or similar product to take in room measurements so you can do before and after measurements to gauge how effective your treatments are.
* buy Toole's book.
* not all reflections are created equally. Address reflections from the back and front wall as they are the least beneficial.
* experiment with reflection vs absorption vs diffusion at the side wall's 1st reflection points. Reflection provides the widest apparent sound source and maintains the mid/high freq energy whereas absorption narrows the sound source and attenuates the mid/high freq energy but usually allows for the best retrival of musical details. Diffusion is like the best of both - it widens the apparent sound source to something more akin to a live performance while preserving the mid/high freq energy and allows nearly as much musical detail retrival as absorption. Personal taste prevails.
* If you're considering diffusion within your room and if the sitting distance to the side and rear walls is short, then use diffusion that either is two dimensional (e.g. RPG Skylines) so that only about 50% of the sound is scattered back to you latterally, or a diffuser that doesn't provide temporal effects (e.g. phase) such as geometrical shapes like round surfaces.

Pictures in my 'System' will show what I speak of.

And have fun as it's an itterative trial and error kind of experience.
Streetdaddy - if you have GIK D1s laying around then sure go ahead and place them at your side wall 1st reflection points to see if it makes it 'less dead' sounding. If you don't have them, then try a sheet of plywood angled so that lateral reflections are sent upwards to the ceiling or sent behind you to preserve the mid/high freq energy.

Summitav - I would agree with you that any indirect reflection is a corruption (e.g. temporal or spectral) of the original direct signal, so as such, may be labeled a distortion. If your mindset and taste is for purity of sound reproduction then you ought to consider listening through headphones. Even in a well damped room such as you enjoy you cannot absorb the low bass frequencies unless it's a huge room where the first modal frequency is below auditory threshold levels. So even an absorbent domestic room will only be absorbent across a limited set of frequencies skewing the reflections you wish to absorb fully. Reflections at glancing angles won't be absorbed so yet again indirect reflections persist.

I like to think in terms of limiting the bad sonic effects of a room while leveraging the positive sonic effects. Get the room working for you not against you, so to speak. Hence the suggestion that not all reflections are bad and those that are should be absorbed or diffused and those that are good should be left alone.

Like I mentioned previously, sonics are as personal as your taste in music. There is no one right way.
Six,
It has been about 3 months since you posted your thread. Care to give us an update on where your construction project stands and the acoustical treatment decisions you've made?