Looking to build HT room

[FredEmmerich]

I am fortunate enough to be able to construct a home theatre room from scracth, including all new construction. Does anybody have advice or know of resources where I can some regarding the design of the room (e.g. dimensions, materials, etc.)?

thanks
Fred

[Audiobeer]

If it's in the basement, build it on a raised wood floor. The difference in resonance for HT is like night and day! :D

[johnaec]

Just last week there was a 5 part series about building a home theater on the DIY TV network. Here's the info that was presented in the shows - go through them numerically in order, (101 - 105): http://web.diynet.com/diy/web/searchResults?Show=+&searchType=EpisodeTopic&searchString=home+theater&WeekNumber=+&x=15&y=12

I didn't watch all of them, but what I did see was very informative! There are also several good links to other information as you browse the info as posted there.

Several times during the TV version, they kept showing segments where you could see part of a JBL Synthesis system as part of the background. If they said anything about this system, it must have been in part I didn't see, ('channel surfing in and out...).

John

[JuniorJBL]

I will try and find the room calculator that I have. It was an excel spreadsheet that worked very well. two layers of drywall is also good or one layer of OSB (prefered, this way you can mount whatever wherever)and another of 5/8 or 3/4 drywall. put the first layer on some of the felt type carpet pad, there is a name for it but cant remember it. I put all of my wire runs in conduit so I could change wires if I wanted to. I also raised my floor (basement)
ran conduit to the ceiling for a projector. All conduit ran in the floor all power went in the ceiling. I also ran 4 separate 20 amp circuits from the panel for audio only and I have zero noise. There are a few pic of the theater on the fourm here:
http://www.audioheritage.org/vbulletin/showthread.php?t=5815&page=2&pp=15&highlight=b%26w

I tried to think of everything I may want to do in the future but I have still missed a few things not a big deal tho.
You can hire people to do it as well but it will cost you an arm and an ear (not good for listening afterwards)so do it yourself if you can.
You can pm me for more details or if others would prefer I can continue in this thread.
Shane:D

[Zilch]

http://www.asc-soundproof.com/wd-articles-soundboard.htm

http://www.asc-soundproof.com/wd-articles-soundproofing.htm

http://www.quietsolution.com/Products/Construction___Building/QuietRock/quietrock.html

[geowal3]

Here were some features I incorporated in the construction of my "media" room which helped a lot with the WAF while in use:

Double stud walls (2x4 and 2x6), ¼" space between, both filled with HD fiberglass. (24" O.C studs okay with 2x6 & nine foot ceilings, but 2x4 studs are too flimsy for 24" – go to 16").

"Acoustiblok" sound barrier over the inside studs on the media room side (www.acoustiblok.com) (http://www.acoustiblok.com)/).

Resilient channel strapped across studs over the acoustiblok. 5/8 drywall both sides.

Makes for a pretty thick wall - almost 11". (Floor joists are the weak link acoustically). If feasible, do not have floor joists run continuously under adjacent rooms. Use a rubberized caulk beneath floor plates. Better yet, build on a concrete slab - not feasible here in cold climate (Montana).

An exterior grade hardwood door (in this case oak) with an exterior type compression seal .

Dense felt carpet pad rather than foam.

The dimensions and seat positioning can be optimized using the "Roomsound" spread sheet, distributed by "Stereophile Guide to Home Theater" (now defunct?) in conjunction with their March 1999 issue. For some reason I cannot attach this spreadsheet to this post :banghead: , but I can attach it to a regular email. If you want it, please PM me with a regular email address and I will be glad to forward.

[tomp787]

Hello,

I found the following book helpful. The author includes some theory as well as practical information from his projects.

http://www.gedlee.com/Home_theatre.htm

I hope you enjoy your project.

Tom

[Steve Schell]

Fred, it sounds like you are going to be living my dream. Here are some thoughts...

First of all, find a copy of The Master Handbook of Acoustics by Everest. This book contains an easy to understand discussion of room modes, standing waves and other room evil meanies. Medium to small rooms are basically a big problem acoustically, but careful design from scratch should minimize most of the usual pitfalls.

Axial modes between parallel surfaces are the largest problem, causing the greatest disruption of the smooth distribution of sound through the space at low frequencies. You might have to fight with your carpenter; they all seem to want to keep their saws set on 90 degrees. If you can build the walls with a slight angle to avoid parallel surfaces, the axial modes will be converted to less harmful tangential or oblique modes. There are likely modern computer programs that can be used to design a room with the smoothest reponse in a given size. Optimizing the ratios of the distances between the walls to avoid overlapping of modes will also help.

I once heard a performance at a small performing hall in a Yamaha music school. The room sounded very smooth with little or no slap echo dispite being fairly live. As I sat there I noticed that the entire room looked a bit out of kilter; all the walls were angled slightly from 90 degrees.

Rooms with a high ceiling have always sounded good to me, especially if they have a peaked ceiling with a low rise, or an angled ceiling that becomes higher from front to back. I also favor a lot of room damping and a highly directional horn speaker system to maximize the ratio of direct to reflected sound at the listening position. You will want to allow for some flexibility in the installation of room surface treatments, as inevitably you will need to tune the room a bit for best results as you finish the job.

Speaking of horns, you have the unique opportunity to build an awe inspiring front loaded horn subwoofer into the structure of the building, and have the mouth(s) exhaust into the front of the room in a non obvious manner. Such a sub will offer frequency extension, low distortion and dynamic range that cannot be achieved any other way. I will be happy to help you with this; just drop me a line at [email protected].

Please keep us up to date on your progress, and post lots of pictures!

[FredEmmerich]

Thanks to everybody for their input and advice, its just what I need! I have a lot of reading and research to do.

One question (hope it doesn't sound dumb): do all these acoustic principles hold for a regular 2 channel stereo setup as well as for HT?

Fred

[JuniorJBL]

Yes:)

[Akira]

while i have never built an HT room, as a pro sound & recording engineer i have constructed 3 recording studios and the same rules apply.
*if this is your basement you're limited but, you can't beat height...10' clearance is ideal.
*18' is the minimum distance to properly reproduce 60Hz. this does not mean you cannot hear 30Hz, but you want to reproduce a full 60Hz unimpeded wave length, as opposed to harmonics and reflextions of the fundamental. for this reason there is no such thing as a professional recording studio shallower than 18'.
*the greatest improvement you can make to speakers, expecially JBL's is to flush mount them into the wall, approximately 1" proud of the surface. the boxes dissappear and the room becomes your speaker.
*you can have a symetrical room (almost all studios are) but they incorporate a "reflextion free Zone" in their design archeticture. meaning, all surfaces are gradually sloped with 90 degree corners taken out, or rather sloped out. for example the front wall gradually opens up, similar to a baseball diamond but with at least 2 pairs of slanted angles. this includes the ceiling, very important and while extra work, it is not hard to do.
*it is absolutely imparitive that your opposing rear wall be solid (not just dry wall) or the your stereo image will not be equal as phase shifting results...i found this out the hard way. really only concrete can fix this...
*in a recording studio the rear wall usually has a baffel design to create an "infinite" space simulation, cancel nodes and in some cases act as a bass trap.
*finally, your acoustic ideal is neutral, not sound dead. one simple and esthetically pleasing way to do this is to make several (10-12) rectangular 2" thick baffels incorporating a nice wood frame some insulation and a nice cloth material cover. put a grooved strip of wood along your walls and hang these baffels at different intervals and heights. THIS WILL ALLOW YOU TO TAILOR AND FINE TUNE YOUR ACOUSTICS TO AN IDEAL AND YOU WILL BE AMAZED AND LEARN A LOT ABOUT ACOUSTICS. if you do this you need only paint your drywall as the combination of reflective and absorbative surfaces create your room acoustics and if done right it can also look great. (there is a picture of this...sorry lousy pic...on my website under the heading ADR/foley.
Akira, Soundchaser Pro Audio http://soundchaser.ca

[FredEmmerich]

Why would you want to flush mount JBL's? (as opposed to other types?) I would assume the cabinet would have to have a front port??

Fred

[Akira]

all conventional box speakers which fire forward benefit from flush mounting. JBL often used to refer to their products as musical instruments. for example, if you tap your finger on all 3 drivers of my L100's, the chambers are tuned in perfect octaves. the reason i said JBL in particular benefit from flush mounting is because, they more than anyone tend to lean toward studio monitor design. that is after all their "heritage" and the reason this site exsists. i use tannoy system 12DMT's in my studio (not my choice!) and they give specific flush mounting instructions. A MUST! they even go so far to say that the surface the speakers sit on should be hard point???
i think infinity and B&W make some great products but, they tend to lean toward home audio in their designs and thus are meant to work in that type of environment, yes (bite my tongue) in some cases better than JBL. for similar reasons electrostats would loose all of their benefit if resessed in a wall. so yes, any port would have to face forward.
if you've ever heard a world class studio the sound is unf__ken believeable!
it sounds as if you're right inside the singers throat. you can hear the sound of a drum stick hitting a white coated head followed by an instantaneous explosion. the reverb floats in the distance as if miles away and you can hear the decay even though it sits 40db under the main program. the sound can be so loud that you can't even look at it...yet it is effortless on the ears. and most of all, you hear NO BOX!
Akira

[Zilch]

We'll all thump our L100's and report the findings here.... :p

[Don Mascali]

We'll all thump our L100's and report the findings here.... :p


Kinky...
The mental imagery is staggering.:D

[Ken Pachkowsky]

if you've ever heard a world class studio the sound is unf__ken believeable!
it sounds as if you're right inside the singers throat. you can hear the sound of a drum stick hitting a white coated head followed by an instantaneous explosion. the reverb floats in the distance as if miles away and you can hear the decay even though it sits 40db under the main program. the sound can be so loud that you can't even look at it...yet it is effortless on the ears. and most of all, you hear NO BOX!
Akira

Akira

Widget recently asked me "what exactly is missing in your system".

Your reply has slapped me in the face. I spent a few years in the studio business back in my youth. The first time I heard a pair of Westlake Mains was at Century 21 Studios in the spring of 1976. I ended up working there and could only dream of one day owning a pair.

Your description is spot on. I have spent 30 years trying to make my living room sound like a control room. %^%$:banghead:

I hate you:)

Ken

[MJC]

*the greatest improvement you can make to speakers, expecially JBL's is to flush mount them into the wall, approximately 1" proud of the surface. the boxes dissappear and the room becomes your speaker.

That is then an infinite baffle, something of which I'm familar with, the 16" wide baffle of the L212 presents an infinite baffle to the 066 tweeter. But when those boxes are changed to mirror imaged(the driver centers are shifted 2" off the center of the baffle, toward the middle of the room) a better, wider soundstage develops.
Likewise, the JBLs that would be considered to the next steps up from the L212, the 250Ti, for example, the baffle is tappered so the tweeters aren't shown an infinite baffle.
I do have four L212s mounted to the walls(5" proud), but they are only the surround speakers in a 7 channel setup.
The main L/R mirror image pair are over 3' forward of the end wall and over 5' from the side walls and with most recordings produce a soundstage that seems wider then the room. And being they are over 5' from the side walls eliminates most, if not all, early reflections.

Maybe the best speakers I've ever heard, as far as producing a wide, deep soundstage, were designed be an electrical engineer, in Reno, that had a xover card mounted right at each driver(MTM design), with all the wiring in the xovers measured to exact lengths. He called it grouped delayed.
He had those speakers setup in a very large room, with the speakers at least 8' from the end wall at at least that far from the side walls. When I asked about the speakers being so far from the walls, his answer was the walls never did speakers any good. I would have to agree. Have you ever heard a concert in an outdoor ampitheater? There are no walls there.
The depth of the soundstage was just amazing, it was as if you could just see the stage full of instruments right in front of you.

[Zilch]

A 15" wide baffle would be a "finite" baffle for a tweeter, with concomitant diffraction effects.

Outdoors without boundries is actually about the WORST environment for listening to recorded music. :)

Please, read Toole in the June AES Journal.

[They need your $75....]

[Tom Brennan]

This works for me.

Thank you Rich.;)

[MJC]

A 15" wide baffle would be a "finite" baffle for a tweeter, with concomitant diffraction effects.

Outdoors without boundries is actually about the WORST environment for listening to recorded music. :)

Please, read Toole in the June AES Journal.

[They need your $75....]

Actually its 16" wide, not 15". A quote from the L212 manual: "The width of the cabinet is designed to create a front baffle surface that is effectively infinite for the high frequency radiator."

And I was talking about live outdoor music. Who ever heard of listening to recorded music in an ampitheater.

[Zilch]

And I was talking about live outdoor music. Who ever heard of listening to recorded music in an ampitheater.
Amphitheater works because of its boundries, of course.


The depth of the soundstage was just amazing, it was as if you could just see the stage full of instruments right in front of you.The rationale for which playback setup was concert, outdoors, without boundaries.

Zilch stupid. :banghead:

[MJC]

Amphitheater works because of its boundries, of course.
Ya, the boundries behind the band, there were no boundries where we were sitting.


The depth of the soundstage was just amazing, it was as if you could just see the stage full of instruments right in front of you.
Just in case that statement was unclear, I was referring to the speakers the guy in Reno designed and how far away from the walls he had them.