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In a Home Theater, Does Size Matter?

December, 2003

Brian Florian

 

THE ENVIRONMENT IS JUST AS IMPORTANT AS THE EQUIPMENT!!

Print that out and pin it above your bed.  The simple truth of it is all too often forgotten.   The best projector and screen in the world can't look good in a room where light is out of control.  A speaker which measures flat in an anechoic chamber will sound terrible when surrounded by nothing but bare walls.  The bottom line is that we pay too much attention to the equipment, and not enough attention on the room.

But how tight can we go?

I've never made any bones about my financial situation: I don't make a whole lot of green.  Just enough to have a modest mortgage and still squirrel away a little for a rainy day.  We buy generic ketchup, heat the house to no more than 650 F in winter, and drive an Echo.

So, this is a story of me making the only theater I could afford.

The largest contiguous space available to us in our basement was roughly 10' x 11'.  The task then was intellectually monumental: Make a pill box look and sound top grade.

The size of the room very quickly dictated some parameters:  We could accommodate no more than two people, fortuitous, as there is only my wife and I (so far).  In keeping our heads out from the back wall even just a little, the distance from our eyes to screen and speakers would be just 7 feet, which meant a 30"-  34" 16:9 direct view TV or 40" flat panel screen, and speakers that lend themselves to near field use.

Construction

The largest undertaking was to undo the slapstick superficial work performed by the house's previous owners.

We removed a little of the right wall, increasing the entrance opening in the hopes of letting a chunk of audio energy, particularly bass energy, escape out that way.  I will share a few photos of the progress, such as insulating the concrete with the TruWall system, dry wallin', and drop-ceiling install.

Insulating the basement wall

 

We be drywallin' !

 

First coat of paint Drop ceiling: a two person job!
Ceiling done, lights in place In goes the carpet

At the same time as this room (HT) was under construction, we had our ancient fuse box replaced with a 200amp breaker box and ran two dedicated lines to the HT room:  One was at the front for the equipment, another at the back for future use (such as a second sub) or what have you.  The lights were piggybacked onto the existing light circuit for the basement.

For the Love of Video

Inspired by Stacey Spears' effort to make his particular room 100% black, we started in that direction.  We got a shade of paint called 'Merlot' which was so dark that after two coats you could not see into the corners, even with broad daylight streaming in!  It made us uncomfortable, and I was concerned that such darkness during the day would eventually encourage mildew or mustiness should the basement ever get damp (ever hear the phrase "light kills germs"?) The compromise was to lighten the walls but keep our plan for a black ceiling.  The color we chose is just one step off of absolute gray into blue.  I can feel Joe Kane cringing right about now, but as I'll show, much of the wall behind the TV got covered in dark grey acoustic foam anyway, so on the whole, the slight blue doesn't mess with my vision to any extent I'd be concerned about.

For illumination, we put in a total of six track lights, three across the front aimed behind the TV and speakers, and three above the couch.  All are on a Lutron dimmer, chosen for its reputation for low noise.  We could not find any PAR20 style bulbs that were spec'ed at D6500 so we went with a "Full Spectrum" filtered bulb.  It wasn't 100% correct but definitely more neutral than a yellow incandescent or a blue halogen.  Again I can feel Joe Kane grinding his teeth.

The black ceiling is probably our favorite part of this room.  In addition to just looking cool, it significantly lowers light scatter and makes what little light we do use very easy to control.

With the blinds down and lights dimmed to just above the Lutron's minimum, we get just enough light behind the screen to reduce eyestrain, enough at the couch to see our popcorn bowl, but not so that any hits the TV screen.  No reflections, no hot spots, nothing.  In the above photo the lights are up to full power! Note how no light reaches the front of the speakers, the equipment, and most importantly the face of the TV.

The Auralex 3" Studio Wedge

For the Love of Audio

Now we get to the fun partmaking the room not sound like the small square box that it is. With construction finished and the paint dry, I began to lose faith.  There was a horrible sound in there.  I temporarily set up a couple speakers and hung my head.  It sounded like I was inside a tin can.

What was happening is that the speakers were being overpowered by reflections of their sound bouncing off the walls.  Our primary focus therefore was to absorb some of that extraneous sound.  This did not mean wall to wall coverings, turning the room into an anechoic chamber though.

While there is a wealth of Do-it-yourself ideas out there (such as the now famous Owens Corning 700 series insulation), for this project we wanted to try something commercially available.  These can be extraordinarily expensive though.  While treating a room with Auralex products still requires a financial commitment, they seemed more reasonable while still offering known performance specs, a professional look, and peace of mind (you don't get fire safety rating on generic egg crate foam).

We chose Auralex 3" StudioFoam wedges for this task, installing a 2'x3' peice behind each front speaker and on each side walls coincident with the primary reflection point from the front speakers (see floor plan, above).  I've seen many people make the blanket statement that you want absorptive material on the entire front wall, but in my opinion, it is possible to overdo it, especially considering my HT room's need for dipole surrounds, which we'll talk about later.  Such speakers actually need reflective surfaces to function properly, so our foam was not to be installed above 4 feet off the floor.

The 3" wedges in the positions shows in the floor plan above made the room remarkably dry and tight sonically. 

For those interested in a more "discreet" look, one can simply make a frame from 1"x4" wood to go around the perimeter of a sheet of wedges, and cover that with an acoustically transparent piece of cloth such as the now renowned Gilford's of Maine material.  Another option is to find solid foam sheets which look tidier and may even be more effective.  Acoustic guru Floyd Toole suggests avoiding any sort of "cut" foam because, in his research, a 3" thick wedge cut has less absorption than a 3" thick solid piece.  Nothing wrong with wedges (except that they may gather more dust over time), but his point is that wedges are more about "the studio look" than actual performance.

Foam products like the Auralex wedges are rated and/or measured down to about 125 Hz.  Their effectiveness below that drops off dramatically, and that's being polite.  So our attention now turned to bass and the subwoofer.

The data sheet put together by Harman International (available for free from their website) told us quite a bit about what to expect in terms of bass insofar as standing waves are concerned.  As far as major axial modes, all but the first would be well above the crossover range and of little concern. With the main left and right speakers placed at the null of the first odd-order mode in the room's width (coincidentally a good place for them anyway), we could effectively null out all but the first axial mode through the width.  This means even bass response when seated left or right within the speakers' range, assuming identical bass in the Left and Right channels.

Within the subwoofer range, there would be one nasty mode in the width and another very close to it in the length (52 Hz and 56 Hz).  Keep in mind though that we have no wall to our immediate right (see floor plan above), and to the right of the right speaker is a thin, flexible access panel leading to a crawl space under the stairs, so we're not really getting the full double whammy here, the single 52 Hz node in the length being our major concern.

When tried right in either corner, a sub would throb with excessive energy in that range. It might have been interesting to place one right between the front speakers, but unfortunately that just was not possible.  A pair of subwoofers would also have worked wonders, placed exactly where the front left and right speakers go.  We contemplated using a pair of subwoofers as "speaker stands", but my budget precludes us from acquiring a second unit at this time.

Being seated so close to the back wall, we knew we needed something there but were uncertain as to absorption vs. diffusion so we contacted Auralex for some advice.  Gavin Haverstick, Acoustical Engineer at Auralex, was adamant that diffusion was inappropriate because we were just to close to the back wall.  "I have an idea for your back wall", he said, "and at the same time we'll take care of the bass".

The Auralex Versatile

One of their newer foam products is the VersaTile.  As the name suggests, it is a tile of acoustical foam which has more than one use.  They are shaped to either go flat on a wall for broadband absorption or in a corner with a void of air behind them.  The VersaTile is much less expensive than Auralex's other corner products and Gavin feels only a little less effective as a corner absorber.

On the back wall we placed a row of VersaTiles flat.  While at CEDIA this past September, I attended Floyd Toole's workshop on acoustics.  It was gratifying to hear him show how when you are seated against the back wall, or close to it, you really want absorption directly behind you.  Nice to know we barked up the right tree.

The rest of the VersaTiles went into the three corners, the back corner getting a triple layer of them since it is the acoustical symmetry of the opening at rear right.  We fussed and fussed with subwoofer placement and finally found the position shown in the floor plan (out from the front left corner).  There is still just a bit of a swell at 50 Hz or so but it is not dramatic and could be zeroed out with a filter later on.

An ongoing problem we have is noise from the drop ceiling.  Every so often one will buzz with a deep note, not from the sub but from the surrounds (even though they are high passed).  Tapping the offending tile makes it stop buzzing but a few days later another will start up.  One solution I've read about is to cut pieces of dry wall slightly smaller than the ceiling tiles and place them on top of each one to weigh things down.  I've yet to work up the gumption to undo all my other efforts and try it.

Our Reference Equipment

While this room is designed to allow apt evaluation of any equipment, a few words on our choice of reference gear, at least those pieces which relate directly to the room, is in order.

At the present time, our screen consists of a trusty Sony 27" Trinitron.  This one is a real gem because it does not include any of the useless "features" that are now so prevalent, such as SVM, "auto" color, or other such nonsense.  D6500 calibrated and meticulously tweaked, many friends and family have asked if it is HD.  Of course it is interlaced and decidedly not 16:9, but the only direct view monitor I'd be truly satisfied with is the now discontinued Princeton AF3.0.  My search for a screen goes on.

The M&K MX-105 sealed subwoofer turned out to be a perfect fit for this room.  We hooked it up, and everything snapped into shape!  With the VersaTiles three-deep in the back corner opposite the opening, we have very tight bass, without ridiculous humps.  Our couch is so narrow that there is virtually no difference in bass when seated left or right.  The left seat sounds just a little fatter and the right a little leaner.  In practice though, the variance is small enough that I let my wife decide where to sit.  Left or right seating does not affect my movie watching enough to be preoccupied with it.

For surrounds, the choice was extremely critical.  Shoved up onto the ceiling, as far apart as possible, they are only six feet from the center seat.  I don't mind seeing direct radiating speakers used as surrounds, but to "get it right" they have to be relatively far away from you.  If not, as would be the case in this room, sitting even slightly off center would get you a collapsed surround sound field.  We chose a pair of early Paradigm ADP-170 V2 speakers as our reference.  These are a "classic" dipole in that the front and back drivers are really at 1800 to one another (as opposed to designs which put them at as little as 900).

Paradigm knows a thing or two about dipole design.  Although not THX per sť, these are made with the same mandate of flat power response, that is, a flat response as a sum of its sound, as opposed to on axis.  As such, we get a full spectrum sound on either side, discrete enough to impart direction and "image" with the corresponding front speaker, all the while working well for both people on the couch.

For fronts, we've settled on a trio of M&K MPS2510 THX PM3 speakers.  These pro models have controlled vertical directivity, but it is not quite as tight as the standard S150THX.  This is important because, again, as we are so close to the speakers (as is the case in most mixing rooms), slouching in my seat can change my vertical angle from the speaker by 10+ degrees.

The seats are actually a pretty important choice.  You'll be spending at least two hours at a time in them so you want something that will be comfortable in the long term, not just the 1-2 minutes you spend in them at the store.  I recommend shopping for furniture like this in a gallery that will let you bring a book and spend quite a bit of time sitting in a piece before buying.  Have you ever felt comfortable at the start of a movie but by the half way point are twisting and turning to get rid of that pain in your back?  We chose a La-Z-Boy "Motion Loveseat", basically two recliners stuck together.  We considered two recliners but felt that the adjacent arms would waste prime real-estate at center.  The loveseat puts us both immediately adjacent to center, and it's extremely comfortable.

Decor

Just a few notes on decor.  We've been buying movie posters from movieposter.com and have found the prices very reasonable and the selection second to none, but mounting posters so that they will stay nice for years can cost a fortune.  We've found that black foamcore, at $10 a sheet, works perfectly.  We use a spray adhesive, carefully lay the poster on the foamcore, trim the foamcore, and seal the poster with a matt art fixative.  We get all this at a decent art supply store because they stock "acid free" foam core and archival quality adhesives and coatings.  These are things you will want if your posters are to stay around for while.

Some of the curiosities in the room come from bugging the local cinema.  A 20min 35mm film real and various non-functional projector lenses pepper the room.  Cost:  Free.

Summary

At the end here, I hope I have inspired some of you with limited space and/or limited finances.  Don't be afraid of "going small".  A properly set up TV and audio system in an accommodating room can deliver a high quality and immersive movie watching experience, easily besting state of the art equipment placed in a poor AV environment.

 

- Brian Florian -

© Copyright 2003 Secrets of Home Theater & High Fidelity
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