[gundam91]

Hi all,

Been lurking here on and off reading posts to educate myself. I am actually building a dedicated listening room from the ground up as part of major house remodel. I am trying to figure out how to approach this project.My budget is around $20k for the interior of the listening room (to "decorate" the room, not including furniture and any AV equipment).

I had spoken to some local high end dealers, room acoustic treatment "specialists"/companies, and all they tell me is exactly what I don't want to do: sticking these ugly acoustic panels all over the room. I spoke to Rives Audio, and I don't think they quite get it either.

So I bought a stack of acoustic books and read through all of them on my own, to get some ideas of what I need to do. My background is in Architecture, so I am trying to design elements into the room to act as acoustic treatments. I had just spoken to an acoustic engineer through a mutual acqaintence. He does professional recording studios. I was hoping that he may point me out to the right direction. But he told me that my budget is too low, and that consulting fee would be at least $5k if not more.

I am not trying to build a professional studio or a listening room for professional reviewer. I've pretty much designed out the room aesthetically, and based on most of the basic acoustic principles that I had learned from those books. Are there ways to get some professional opinions and guidance without spending that kind of dough? I was thinking maybe $2k to $4k at most. Do I really need to get some engineers to spend hours doing calculations to get good results from the room? One thought I had was to build the room, and get an acoustician to do a measurement afterwards, and tweak the room if necessary.

At the moment, the room dimensions will follow Sepmeyer Ratio: 10ft (H) x 16ft (W) x 23.3ft (L)

Thanks in advance for any input/advice.

FrankC

[youngho]

One book you might particularly helpful is "Sound Reproduction" by Floyd Toole. He argues that normal furnishings are nearly adequate for most listening rooms, although you will still benefit from some broadband absorption directly behind the listening position, as well as on the front wall between the speakers (however, he and other audio luminaries like Siegfried Linkwitz and Tomlinson Holman seem to feel that lateral reflections can be beneficial, so the normal approach of first reflection absorption may not be suited for most home listeners, particularly when said absorption varies over the frequency spectrum, since preservation of the spectral content of these lateral reflections seems to be key). He discusses the role of drywall itself for bass trapping. In the end, you will do well to take some measurements after construction, particularly below 200-300 Hz, since pre-construction calculations will be changed by real-world variables like type of construction for the walls, ceiling, and floor (normal drywall construction will shift the amplitude and frequency of modes downward); location of loudspeakers and the listener(s) in terms of modes (calculated modes may not correspond to measured ones if they're not excited or perceived in the first place); the presence and location of fenestrations like doors and windows, particularly when asymmetric; the location and type of furniture (leather versus upholstered); the location and type of wall-hangings and floor coverings; etc. It gets complicated really quickly.

You can do quite a bit of measurement yourself using a microphone, computer, and software.

Sorry if this doesn't really answer your questions.

[bpape]

There are ways to do what you're trying to do.  What concerns me is that you say you've already designed the room aesthetically.  So if you've done that, how do you propose to have anything in or as part of the room that can impact the room acoustics other than furniture? 

Things that can be done to 'hide' treatment and improve acoustical performance:

- columns
- coffered ceilings
- soffiting
- Wainscoat
- 'furniture' designed as treatments

Bryan

[MaxCast]

Is it truly form the ground up?  Meaning can the size change?  Along with what Bryan has said, I'd look into angling the left/right walls and the ceiling if you can (no parallel surfaces).  Built in book cases, shelves, etc with varying depths can and some natural diffusion.  Built in soffits hiding acoustic material can look nice with lighting be hind them as well.

Bryan, how can one use wainescoating for a benefit?

[Ethan Winer]

all they tell me is exactly what I don't want to do: sticking these ugly acoustic panels all over the room.

The rule of acoustic treatment is you can have Effective, Attractive, or Affordable - pick any two. You can absolutely have highly effective acoustic treatment that looks good (or is totally invisible), but it costs more. The standard approach is to either build the treatment into the room, or apply commercial traps on the walls and ceiling then cover them with stretch fabric frames. The former also requires some sort of fabric coverings, but it will be flush and avoids losing six inches or whatever with the false walls.

--Ethan

[bpape]

If you're building from scratch, you can build out the bottom of the walls around 4" after the drywall and make wood faced membrane type bass absorbers out of them.  That also provides space on top to do the cloth to bring it flush and hide any and all treatments unless you have something thicker like diffusion, corner absorbers, etc.

Bryan

[gundam91]

Hi all,

Thanks for some great advices and ideas for further contemplation. Yes, the room will be build from the ground up. It's right now just a patch of grass in the backyard. We've just ironed out the preliminary layout with the architect last week. One of the ideas we are looking into is angling the wall and ceiling so we won't have parallel walls.

I've also read some paper discussing the importance, rather the "non"-importance of side wall reflections. Right now the design is all on sketch paper of how the room will look. There will be some features in the ceiling to break up the plane. For the front wall, probably some RPG skylines. For the sidewalls, I found this vinyl wallpaper that have 5/8" squares angling randomly at different directions that will act to refract the sound. We had used the material in a conference room at work, and it worked really well.

The only thing that I am not 100% sure of how to deal with is the bass traps. If I understand correctly, you want to apply these to the corners. The only idea I have at the moment is to apply the Auralex LENRD foams to the corners along the front wall. Anyone got some interesting ideas???

Right now, I am leaning towards building the room first, then get a friend who has some measuring equipment to do some measuring, then try to deal with any room nodes/issues from there.

FrankC

[bpape]

One design element you can build in (that I'm planning for my next house) will do two of the things you're looking for.  You have a 10' ceiling.  Now, imagine below that building an angled ceiling from wood slats that starts at 8' and slopes up to 10' in the rear.  Absorption behind it and variable gaps between the slats and variable slat widths will give you a variable tuning Helmholz absorber for the bottom end that will still act as a slanted surface for the mids and highs.

Bryan

[gundam91]

Bryan,

Thanks! That is pretty close to what I have in mind for the ceiling. But I did not realize that it would have benefits for the bottom end.

FrankC

[Ethan Winer]

One of the ideas we are looking into is angling the wall and ceiling so we won't have parallel walls.

The benefit of non-parallel walls is overrated IMO. It's not bad a thing! But unless you have substantial angles like 30 degrees it's probably not worth the effort.

I've also read some paper discussing the importance, rather the "non"-importance of side wall reflections.

I'm aware of that philosophy but I disagree with it strongly. You should find a room that has treatment on all the reflection points and listen for yourself.

For the front wall, probably some RPG skylines.

Diffusors do much more good on the rear wall behind you. Unless you have dipole speakers that send sound equally front and rear, putting diffusion on the front wall is mostly a waste.

For the sidewalls, I found this vinyl wallpaper that have 5/8" squares angling randomly at different directions that will act to refract the sound.

That stuff is not thick enough to diffuse to a usefully low frequency. If you're going to all the trouble to build a dedicated room you should do it properly with real diffusors.

The only idea I have at the moment is to apply the Auralex LENRD foams to the corners along the front wall. Anyone got some interesting ideas???

There are much better bass traps available. Those are simply too small to do much below a few hundred Hz.

--Ethan

[bpape]

General rule of thumb that I use is to get 1" taper per foot of length to be really effective.  This would have to be on both walls.  So, by that rule, if your room is 21' long, you'll have a room that's 42" narrower in the front than in the back.  Less can still work but mostly in the mids and highs - it's not going to prevent bass issues.

Bryan

[bpape]

Bryan,

Thanks! That is pretty close to what I have in mind for the ceiling. But I did not realize that it would have benefits for the bottom end.

FrankC

Do some research on slatted resonators.  You'll find that the gaps won't be terribly big given the depth of the cavity you have to work with.  Slat widths that I am planning would vary from around 2.5" to around 6".  Gaps between 1/8" and 3/8".  Vary things all along the taper and you can repeat patterns as you go since the depth of the cavity behind will also be constantly getting smaller (tuning is higher)

Bryan

[youngho]

I've also read some paper discussing the importance, rather the "non"-importance of side wall reflections.

I'm aware of that philosophy but I disagree with it strongly. You should find a room that has treatment on all the reflection points and listen for yourself.

For the front wall, probably some RPG skylines.

Diffusors do much more good on the rear wall behind you. Unless you have dipole speakers that send sound equally front and rear, putting diffusion on the front wall is mostly a waste.

The only idea I have at the moment is to apply the Auralex LENRD foams to the corners along the front wall. Anyone got some interesting ideas???

There are much better bass traps available. Those are simply too small to do much below a few hundred Hz.

From what I've read about lateral wall reflections, these will tend to increase Apparent Sound Width (ASW), which may correlate more with real concert experiences in older halls (I live in Boston). However, musicians seem to be particularly sensitive (ave. 7x so) to these lateral reflections, and those involved in the audio industry are probably also more sensitive, as well. Since Ethan and Brian are industry professionals, their sensitivity may be greater than Frank's in this regard. Many audiophiles particularly value pinpoint imaging, so these folks would probably be happiest with significant absorption of first reflections on sidewalls, which apparently is best if it is relatively constant across the frequency spectrum above the transition region (200-300 Hz for most listening rooms but dependent on room size) so that the reflections that do reach the listener resemble the original signal in spectral content, rather than degrading it because of the differences. Others particularly value the perception of spaciousness and prefer dipolar or omnipolar designs, where it would not make sense to apply absorption to the sidewalls. The possible desirability of lateral reflections as contributing to ASW and spaciousness is relevant primarily in two-channel systems; however, psychoacoustics suggest that listeners may be most sensitive to these close to 60 degrees off from center, so if the reflections are from significantly away from this angle, as when the speakers are either too close to or extremely far from the sidewalls, then absorption may be desirable. Incidentally, I speculate that speakers with uneven directivity like first-order crossover designs will tend to benefit more from sidewall reflection absorption because of the significant deviations in off-axis response. It's probably best to consider and identify one's own priorities in terms of the experience of audio reproduction, since this will ultimately be an individual decision. Toole and others before him have dissected and disposed of common oversimplifications about audio reproduction like "reproducing a live experience," "hearing what the microphone hears" or "hearing only what is on the recording," "transporting you to the original venue" or "transporting the musicians to your room," "all live music sources are essentially omnipolar," etc.

Bass traps are an interesting topic. Resistance absorbers are ideally placed in or near areas of maximal particle velocity, like in the middle of the room. Diaphragmatic or membrane absorbers are ideally placed in or near areas of maximal pressure gradients, like in the corners, particularly the trihedral ones. However, before embarking on the construction of Helmholtz resonators and slat absorbers, it might make sense to make some measurements first to identify which problems need the most treatment. There are other supplemental approaches to room modes, including the use of multiple subwoofers in various configurations, a la Welti versus Geddes, but all rooms will benefit from bass trapping.