Size & perforation question

Claude,


What did you decide?


I currently have a Vutec 103" diagonal screen and I sit about 11.5' away. Problem is that my speakers (l c and r) are about 6' behind the screen. With the screen down (even though the leader is perfed) I am getting fairly muffled audio.


I spoke with Dennis E about this and Dennis states that the issue is related to the fact that at 6' away the dispersion pattern of the speaker is such that the bulk of the audio output is hitting the main part of the screen (makes sense!)


This definitely puts me in the market for a completely perfed screen. I am also concerned as I have my direct view TV as well as audio/video equipment (with associated LED's) behind the screen.


Based on Dennis' strong recommendation I am also considering the Stewart 1.3 w/ a 103" diagonal (BTW Stewart will make any size you want at no additional cost).


Steve

Steve,


I haven't ordered it yet (next few days), but I'm strongly leaning to the 110" 1.3 Stewart with their "THX" perforations.


I called Stewart, and they maintain that the perforations start to disappear at about 10'. So, I'm hoping to be okay at about 14'. They also mentioned that they could perforate the black part of the screen; I hadn't thought about that.


My L/R speakers will be inches from the screen, the center will be maybe a foot or so. I don't think that dispersion will be a problem.


It sure makes me nervous, but I can't figure out a way not to have my speakers behind the screen in my small room.


Thanks,

Claude

Claude,


I hear you. It definitely concerns me to spend at least 4k and not be sure whether it will work well.


With your speaker to screen distances you should be fine. Dennis explained to me that the rolloff on the Stewart THX microperf is something like 2db versus other manufacturers at something like 45db.


You need to be carefull about reflectivity behind the screen, not just your direct view TV. Other glass items of LED's may be a problem.


You should definitely perf the leader part of the screen also.


My concern is the fact that my speaker to screen distance will still be 6'.


Why don't you email me and maybe we can get a "powerbuy" going.



Steve


[This message has been edited by gages (edited April 09, 2000).]

Steve, e-mail will be sent later today.


Ted, since I've encountered delays in building my dedicated home theater, this room is a family room serving double duty. Width is kind of hard to pin down, since the layout is that I'm on one end of a very long room (kitchen one end, family room other end). I guess that the family room "half" is about 18' wide by 19' long. The problem is that on one side there are built-in bookshelves (removal requires divorce), on the other side there are French doors to another part of the house. So, the workable area for speakers is only about 6' wide, right behind the screen. Putting the speakers under or to sides of the screen would be very inconvenient for the shelves and the door, and would really require moving them whenever they were going to be used (too much trouble).


I'm not bothered by the smaller soundstage this causes, I'm willing to believe that it will probably sound okay for movies (serious music listening will be with screen retracted), and I guess that I'll cross my fingers about the visibility of the perforations.


Thanks,

Claude


[This message has been edited by ClaudeD (edited April 10, 2000).]

I have both a Stewart 1.3 Gain and Silver 4.0 Gain perforated screen. NOT the THX screen but the regular perforated screen.


I just put on the Silver 400 as my projector is 2 years old and has lost some of its brightness (PRO900X)


The perforations on the regular perf Stewart are small enough that they dissappear from 14' away. The regular perf screen is much cheaper than the THX screen. My 60"x107 with both screen was $1,700.00.


My speakers are 3 inches from the back of the screen. I used a king size black bed sheet from JC Penny to cover the area behind the screen to remove reflections.


The speakers are Infinity Kappa 6's (3) each with 10" woofers.


I find the sound to be very natural and though the screen/bed sheet will stop some of the highs, I find it sounds more like a movie theater than a Home theater due to the fact that all DD 5.1 soundtracks are very "bright" to begin with.


Anyone in the Long Island area is welcome to come see the regular Stewart perf screen at Lee's Bijou.


Lee

JMartin,


I have all three "screen" channel speakers behind the screen. I also have four 12" subwoofers below the screen for the LFE channel.


The only way to put large speakers behind the screen is to use a bass cutoff of 100 KHZ. This will make sure that the screen will not vibrate from the low bass air that is being pushed by the driver. All DD processors have this cutoff feature.


CLAUDE:


I have seen the THX Stewart screen and to be honest, I do not like it at all for the following reasons:


1. A lot of light passes through the screen. When I saw it at the 1996 CES show in Vegas it was mounted about three feet away from a grey carpeted wall. When you looked behind the screen you could see the image!


2. The image takes on a very glossy look that I found to be very unnatural. The people that I was with also did not like it.


My suggestion to anyone who is considering a THX screen is to take the time and go see it, even if it means getting on an airplane.

They are expensive and as far as I know, once you buy one, you own it and cannot return it.


Lee

The Stewart, by itself, has a maximum 2dB rolloff at 20kHz. On the other hand, the difference between their MicroPerf and THX MicroPerf is nothing...except for the little black box they send with the screen and the logo. The black box compensates for the screen roll off characteristics ... you don't need to use it if you're using an equalizer.


The light loss ranges between 8% and 10% for a Stewart Microperf. I have not seen the numbers for any other manufacturer. 10% loss in brightness cannot be perceived by the human eye. When 100% bright is side by side with 90%, we perceive the difference as 1%.


Rather than being concerned, however, with the loss of light, I'd suggest a better metric would be to determine the actual Foot Lamberts of the screen. For example, if you're getting 20 foot lamberts with a standard screen and 18 with a microPerf, why'd you care? 18 is very @#$# bright (and exceeds the standards for a commercial theater). On the other hand, if you're at 7 (below standard for a home theater), I'd suggest no microperf if not a smaller screen.


------------------

D. Erskine

DEsign Cinema Privee
www.DEsignCinema.com

Imagine what you could do, if you could do all you imagine.

Claude,


You really have to make a decision as to what use your "system" will be; ie: movies, music or both.


I have a dedicated Home Theater that looks like a screening room. The room and equipment is designed around watching movies which is 99.9% of the time.


When soundtracks are transfered to a medium be it DVD, LD, VHS, DBS, etc they use something called an Aceademy (spell check) Curve. Everything above 14,000 kHz is rolled off. The human ear can go as high as 16,000 but no where near 20,000.


The soundtracks for real theaters are pumped up at the treble end for the loss that horns have going through the screen which is thicker than a HT screen. No one uses horns in a HT system. Horns are designed for big rooms like movie theaters. The idea is to have the people in the back of the theater hear clearly while not blowing the people in the front of the theater, out of their seats.


When you place speakers behind a screen you accoplish two very important things:


1. All speakers are on the same plane so when sound is panned from L to C to R the sound will be natural as opposed to having the sound on two different planes like a RPTV where the C Channel is above the screen.


2. The C Channel is located at "screen center" which is where directors place the actors faces. This allows the sound to come from the actors mouth, rather than above or below.


Both of these aspects will heighten your movie experience...like a subwoofer will with explosions and such.


Yes you will lose some of the highs and if this will disturb you than you can use a 3 channel EQ made by Rane Corp. to bring them as high as you want. Just make sure that any EQ is done after the processor and not before.


Personally, as I have said, I like the drop in treble as it is not great. Just enough to tame digital soundtracks. The sound is not muffeled in any way.


Claude, I live 17 miles from the Throggs Neck Bridge. If you live near the GW Bridge it would be less than an hour to my house. The same for the Staten Island Bridge.


Lee

The JBL Synthesis Home Theater system uses true horns (the horns are switched off and conventional drivers switched on for music modes). Just FYI.


Actually, if you place all three speakers (L/C/R) behind the screen, they will not be on the same plane from the listener's perspective. The channel delay circuits in the surround processor compensate for this.


In many cases, you cannot have all three front speakers behind the screen. For example, under optimal conditions with an 8' wide 16:9 formatted screen, and sitting at the recommended distance for a line doubled picture, your speakers need to be 9' feet apart ... just outside the width of the screen.


However, the effect of the center channel behind the center of the screen is memorable.


------------------

D. Erskine

DEsign Cinema Privee
www.DEsignCinema.com

Imagine what you could do, if you could do all you imagine.


[This message has been edited by Dennis Erskine (edited April 11, 2000).]

Dennis,


When I said "nobody uses horns" I meant the horn arrays that are found in commerical movie theaters. I know JBL uses them as does Klipsh.


I will not argue your point about having speakers all on the same plane. I do know that it is one of the requirements for commerical THX theaters and most good DD decoders have a Center Delay, but that is to make sure that the sound reaches the viewer at the same time as the L & R speakers which are further from the viewer than the C Channel.


It is almost a moot point as there are no real "directional" sound movies anymore. All the voices come from the center channel with the music and such from the L & R channels. Not like the old days then an actor walked across the screen and was talking, the sound would move from one channel to the next, depending on his/her movement.


To me....personally.....a home theater is just that...a personal movie theater and movie theaters have perforated screens. I have been using a perforated screen for 10 years.


Lee

Lee, scratch what I said about being reassuring.


Do you (or Panaramax) know how the screens differ in attenuation? I saw somewhere that the THX version rolls off 2db at 20KHz, is the regular Stewart screen similar?


I don't mind the light seeping through the screen (i.e., the Sony 10HT is very bright), but I don't like the image of unnatural and glossy.


Oh, if I only had that dedicated room ...


Thanks again,

Claude