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[Mike Yates]

I am considering stacking two projectors as a cost effective way of producing enough lumens for our projection system. Here's my reasoning: by doubling the projectors aren't the lumens doubled?  Besides the obvious (doubled noise level) what are the con's of stacking two projectors. I am considering the two projectors listed below.  I will install only two of the same model.  

ViewSonic

[Brad Weber]

I'll start by saying that I don't know much about these particular models or Viewsonic projectors in general and I couldn't really find out much about the Viewsonic PJ1158 as you have to enter a serial number to even get access to view the user guide online (they apparently don't offer any mounting or throw distance data online, not real helpful).

I am curious as to how you arrived at these two projectors.  The Viewsonic is apparently a just introduced LCD projector with a 1.5-1.8:1 zoom lens and manual zoom, focus and lens shift.  Your situation seems to require about a 2.25:1 throw ratio and while they show a "long throw" lens option for the PJ1158, it appears that it is still in development and there is no information or model number available.  While it may be a nice projector and a good value, the standard lens and minimal lens options, manual operation zoom/focus/lens shift, focus on the built-in speakers, unavailability of install information, etc. make it seem that this projector is really aimed at portable or desktop use rather than professional installs.  On the other hand, the Mistubishi is a DLP projector that seems to sell for about twice as much as the Viewsonic but has a more appropriate lens, power zoom, focus and lens shift, etc.  Basically a model that seems more aimed at permanent installs.  Just curious as to what led to these two options.

As far as the desired image brightness, if you have 7 f.c. on the screen and want to try to get the recommended minimum 10:1 contrast ratio, then that's 70 f.l. required on the screen from the projector, which is also plenty bright enough in general.  Remember that with front projection screen gain applies to the ambient light as well, the screen can't differentiate between the projector and other light sources, so while screen gain may make the image brighter it won't really change the contrast.  So, 70 f.l. x 12' x 16' = 13,4440 lumens, which is what you'd then want to have as a preferred minimum projector output.

Stacking projectors can help get more brightness but not without some tradeoffs.  The general consensus is that projector brightness is somewhat like audio and that doubling the brightness gives what would basically be a 3dB or noticeable difference.  So it doesn't double the perceived brightness, but the change will be noticeable.  Using two projectors also provides some redundancy, if one projector fails you simply have a less bright image but you still have an image.

Using multiple projectors will be louder, however your decibel math is off.  Two identical sources of the same level result in a 3dB increase so 39dB and 35dB respectively, some increase but not to the 72dB and 64dB levels you noted.  What may be more of a problem is if the two projectors have slightly different fan speeds or sounds in which case you can get beat frequencies between the two that can be louder and more noticeable.

The biggest problem with stacking projectors is getting the images aligned.  One part of this is mounting the projectors, both figuring out how to mount the multiple projectors and then making sure the mounts are stable.  Some projectors are designed to accommodate stacking, the cases are made for this and/or the manufacturers offer stacking mounts for the projectors.

If the projectors are ceiling hung mounting can often be more difficult.  The other aspect is actually getting the images aligned and keeping them there.  Projectors with advanced image geometry control provide more flexibility in aligning the image while projectors with basic keystone and image shift are more limited and may prove more difficult to get fully aligned images.  Also, alignment will drift.  Electronic alignment will change with time and heat while even optical alignment will change as the lenses heat up and cool down.  You'll probably end up needing to warm up both projectors for some time before alignment and then do the same warm-up before use.  Chances are you will never get them exactly right for any length of time and will probably never have as sharp an image as with a single projector.

At probably around $17k or so with appropriate lens, something like the Sanyo PLC-XF46N or Christie LX120 would likely be easier to integrate and at 12,000 lumens provide more appropriate brightness.  But budget is always a major factor.  If you can't afford the higher brightness projector you might want to try controlling the ambient light levels on the screen and also consider using a high contrast screen surface.

[Mike Yates]

Thanks for your reply Brad...I was hoping you would.  I've posted here a couple times and your reponses to my post's always provide excellent thourough advice.  I won't get into details of why I chose these projectors for fear of expounding my ignorance suffice to say price and amount of lumens were high on the list.

I actually have a projection package pretty much put together and was exploring avenues to increase lumens without having to increase the budget significantly.  I've heavily researched projection technology and systems for four months in preparation for my introduction to pro A/V through this purchase.  This will be my first system and as I said in my thread intro I am a sound dude who is begining to delve into the A/V world.

My most recent discovery was exactly how many lumens I would need to project on the 12'x16' screen we will be using.  I've had several consutants/contractors come out to provide advice and proposals and none pulled out a light meter to measure the ambient light that will be hitting the screen.  Through my research I know this is very important in determining the amount of lumens necessary, so recently I borrowed a freinds light meter and measured the ambient light and converted the EV readings to foot candles and determined that the projectors they were approving didn't come close to the lumens necessary.

I have been looking at three projectors up to this point.  The Panasonic PT-D5600 5000 lumen, 2000:1 CR, DLP Darkchip 3;  The Sanyo PLC-XP57L 5500 lumen, 1000:1 CR, LCD; and the Sanyo PLC-XF60A 6500 lumen, 1300:1 CR LCD.

Our budget is not going to allow the purchase of a projector with the proper amount lumens for the current ambient lighting.  The Sanyo PLC-XF46N you suggected is probably the optimum projector for this application unfortunately a $20k budget does not leave much for the peripherals if that projector were purchased.

Here is the system as it has evolved to at this point:

BUDGET:
$20,000

SCOPE:

Worship presentations including: Power Point, still images, film clips

SANCTUARY DIMENSIONS:

•65’ wide by 90’ long
•~32’ from Sanctuary floor to ceiling peak

PROJECTION SCREEN MEASUREMENTS:

•12’ x 16’ (4:3) Projection Screen
•Projector throw distance ~36’
•Projector mount ~14’ from ceiling peak
•Bottom of screen 14’ off Sanctuary floor
•36’ to closest seat
•90’ to farthest seat
•Angle of view maximum ~35 degrees
•Ambient light measured at screen-7.25 foot candles

PROJECTION EQUIPMENT:

Option 1: Panasonic PT-D5600U 5000 lumen DLP XGA projector with a standard zoom lens (1.8 - 2.5:1) which comes supplied with the projector

Option 2: Sanyo PLC-XP57L 5500 lumen LCD, with the standard LNS-S30 (1.8 - 2.3:1) lens.

Option 3: Sanyo PLC-XF60A 6500 lumen projector with the LNSW04 lens

•Kramer VP-724XL switcher/scaler
•Da-Lite Cinema Contour 4:3 fixed screen w/Pearlescent or Cinema vision or Video Spectra fabric & ProTrim option
•Altinex DA1907SX VGA splitter/amplifier
•JVC DR-MV7S DVD/VHS video recorder
•(2) 6ft high bandwidth VGA cables M-M
•200ft West Penn WP8255 shielded coax VGA cable
•200ft CAT5 ethernet crossover cable for remote projector control

COMPUTER:

•Quiet Antec NSK6500 case, NeoHE 430W power supply
•Operating System Windows XP Pro
•2GB DDR2-800 RAM, dual channel
•640GB RAID 5 hard disk array
•BFG nVidia GeForce 7950GT 512MB PCI Express Graphics
(overclocked)
•Integrated Sound
•Gigabit LAN
•Linksys WMP54GX4 Wireless-G PCI adapter w/SRX400
•USB 2.0, IEEE 1394 Firewire connection
•Osprey 210 digital/analog video capture card
•(2) ViewSonic VA912B 19” LCD Monitors w/speakers
•Western Digital MyBook Premium Pro II 1TB external HDD USB Firewire

SOFTWARE:

•OpenOffice.org 2.0
•EasyWorship 2006
•CyberLink PowerDVD 6
•Nero 7 Ultra Edition

Here is a link to some pictures of our Sanctuary and a projection screen (approximate size) I crudely added in using MS Paint:            http://pg.photos.yahoo.com/ph/tootallll/slideshow?.dir=/51f9 &.src=ph

Guess I'll look at ways to reduce ambient lighting.  Which high contrast screen would you recomend?

Thanks!
Mike

[Brad Weber]

Wow, you really have done your research!

Sticking with your Da-Lite selection, I would suggest high-contrast Cinema Vision.  The high-contrast Da-Mat would also work but with less gain and since you're needing all the brightness you can get I'd probably go with the Cinema Vision.

Do be aware that high contrast screens have a gray surface finish.  Some people, especially churches, prefer a white screen because of how it looks when the screen is not in use, so perhaps an aesthetic versus technical issue to also consider in deciding whether to use the normal or high contrast version of the screen surface.

[Langston Holland]

Mike wrote on Sun, 05 November 2006:

The ambient light hitting our screen can be controlled to a minimum of ~7 foot candles. I don't know if this is correct but from My calculation I need about 7-8,000 lumens and a 1.3 gain screen to project in this amount of ambient light. Perhaps my calculations are flawed...I dunno......

Hi Mike - your church is blessed to have you - marvelous attention to detail. Per your question, I have two EIKI 4,500 lumen projectors that I spent several hours with in my living room some time ago attempting to stack them in various ways just as an experiment. I found it impossible to get them to line up perfectly with small text everywhere around the screen. When I'd get the text right on the lower right, it would be off slightly on the lower left, for instance. Change the distance between projector and screen, and it would be wrong again, but different. My applications are portable systems for rental, thus this ended my interest in stacking. Maybe an install situation like yours will make it possible, but I have my doubts.

My original thought was to use something like this if I could get it to work in my living room temporarily:

http://www.chiefmfg.com/store/detail/?product_id=80725

It did make things quite a bit brighter - but the compromised image was unworkable for me.

Hopefully you don't need as much power as you have calculated. As always, I'd demo a projector that fits in your budget and see if it works.

[Mike Yates]

Langston Holland wrote on Wed, 08 November 2006 14:10

...I have two EIKI 4,500 lumen projectors that I spent several hours with in my living room some time ago attempting to stack them in various ways just as an experiment. I found it impossible to get them to line up perfectly with small text everywhere around the screen. When I'd get the text right on the lower right, it would be off slightly on the lower left, for instance. Change the distance between projector and screen, and it would be wrong again, but different...

After reading your post the complexity of such an arrangement became apparent.  Having to adjust and perfectly align two H-V lens shifts and zooms must be extremely difficult.  As far as the ambient light...I've learned the amount of lumens required drops quite a bit in proportion to a small drop in foot candles of ambient light.  I think our ambient light can be reduced by applying window treatments...so that should help quite a bit.

Blessings!
Mike

[Don Boone]

Not meaning to engage in brand bashing but I’ve seen instances where getting all four corners in focus wasn’t possible with just one Eiki/Sanyo projector.

We've done a few installs stacking Sony or NEC projectors with ease. And our rental dept does it all the time. You just need lens shift, zoom, and good projectors.

Don

[Brian K Tennyson, CTS-D]

Never Ever EVER EVER EVER!!!!!

EVER!!!!!!

Try to stack two LCD projectors. EVER!!!!

It is almost impossible to color match LCD projectors and even if you do in a week they will have drifted enough to notice. Either do one bright LCD or stack two DLPs.

Don't do it. You will live with it, and you will hate yourself.

Peace.

[Mike Yates]

  Thanks Brian!  Looks like we'll be using the Sanyo PLC-XF60A...on a Da-lite High Contrast Cinema Vision Screen.  Low on lumens (6500) for our application, but the most we could afford...we'll have to work on the ambient light.  Hopefully the HCCV screen will help offset some of the ambient light.
Blessings
my