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hz numbers on a 15" 2 driver (Read 39060 times)
Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #90 - 05/12/06 at 16:43:16
 
Video morpheous,
Front screen projector (PJ). Cooling fan internal in the unit can be loud in some units. Projectors are usually located above and behind the seating position.

This is my rig. Notice the PJ tangling from the ceiling...

http://community.webshots.com/myphotos?action=showPhoto&albumID=549522535&photoI...

Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #91 - 05/12/06 at 18:03:03
 
Bob,

Shorten that mounting pipe for the projector, which will reduce the wiggles tremendously, or do you have a beam between the PJ and screen like I do which requires a low mount?  If nothing is in the way then getting it up high will have other benefits;  less shooting in the eyes, less heads blocking the image when someone gets up, brighter image because more light reflects down to the viewing area, brighter image because less light reflecting to the ceiling, less chance of someone bumping into the PJ, and best of all, a better picture because you'd use less keystone correction, which distorts the image somewhat.
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #92 - 05/12/06 at 18:35:42
 
Yea, I've got "the beam" in the way.  >:(

Actually keystone is almost dead-on. It puts the lens VERY close to the vertical AND horizontal 1/2 way point of the screen.  ;D

Current location is as far BACK from the screen as I can get. Any closer to the screen, and the PJ will be directly over seating position. (don't want to smack it when I have one of those late-night over the head arm stretches, ya know.)

Here is a picture of the room with the "beam" (lower ceiling).... the "coffered" ceiling is drywall and is flanked by acustical tiles above and behind the seating position (shown in pic), and the same square footage of tiles is also in front of the screen. THAT area is several inches higher than the tiles you see in this pic. The reason was to get the screen higher off the ground. The reason for the lowered section of drywall, where the recessed lighting is, is the beams that hold up the house are inside the "coffer". (don't know how to spell that)

http://community.webshots.com/myphotos?action=showPhoto&albumID=549522535&photoI...

If you look in the far upper left corner of the picture, you can barely see the first ceiling tile. Notice it's higher than the tiles in the 'back' of the room.

Bob
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« Last Edit: 05/12/06 at 18:38:11 by Bob »  
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morpheous85
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Re: hz numbers on a 15" 2 driver
Reply #93 - 05/12/06 at 18:35:50
 
Ahh...it now makes sense. Thanks.

What about movie theater style where it's in a seperate room, shining through plexiglass or glass? Or, just build a plexiglass box around it (with ventilation of course).

Jason
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #94 - 05/12/06 at 19:16:48
 
morpheous, In another room would be a great idea, shining through glass. (logistics might be a bit of a challange, what to do in the other room to hide AND ventilate the rear of the PJ). Minimal video loss beaming through the glass, but probably acceptable.

Building a plexy box around it wouldn't be a good idea. The amount of holes drilled in it to get the needed airflow,... you'd end up hearing it anyway. Some guys have built "hush boxes" around the PJ. Simply a box with sound insulating lining, and an auxillary fan. But then the fan needs to be quieted also. Kind of an endless chain/dominoe effect if you ask me. PJ manufacturers are good about stating db output from fan noise, so you can be selective about the unit you buy. If it's going in another room, you have many more options on projectors to chose from since db's don't matter, see.

Now we're speaking my language. (feeling more confident talking about video than audio)  :D

Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #95 - 05/12/06 at 19:43:53
 
Shooting through a piece of glass will eat 6% of the light output and Bob is already giving up a lot more than that with the see-thru screen (I see your speakers now on the screen only pic).

Bob,
You can probably pick up some stability by bracing those supports up above the ceiling tile and maybe a glass right triangle brace on each of the 2 front supports.  It all looks kind of wiggley.  Paint the supports all the same color at your walls for the PJ floating in the air look (at least the pair in the front).

BTW, work was done early last night, so we watched Finding Nemo with the kids.  We did the Darla scene a few times and just running  a single 100L ported 12" Shiva that is tuned to 24hz, we were getting quite a nice effect and that's probably -12db or more in the teens where the tapping really hits.  It was enough to get a little eyeball jiggling, but not the strange chest compression like in a car.  

I really think the iso loaded Dayton 15's in the box you already have and the single port making it a low tuned BR should hold you over until you're ready to get radical.  Plus the finish work is already done.  A tube for a port, bolts to clamshell the drivers, a small piece of wood to block the 2nd port, and something to seal is all you need.  Worry about HWKenstein later.
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« Last Edit: 05/12/06 at 19:45:47 by John in CR »  
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #96 - 05/12/06 at 21:09:43
 
John, The 3 speaker hole silouettes you see are no longer. Of the original 7.1 set-up, you obviously see the 2 front main surround. The system is now 5.1. The side surrounds are now the fronts. I had very little channel seperation with the fronts 9' apart, sitting about 17' feet back. Speakers behind cloth, well.... you guys don't need any more explanation there. Now the fronts are 12' apart, and 5' in front of the seating "plane". MAN, talk about stereo/surround seperation. 100% better.
The center is now sitting on top of a stand 1/2" below the bottom of the screen. Originally I wanted a 'clean' look, hiding 3 speakers would be idea,  but didn't stay that way for long.

I like the glass triangle idea John. Also may use extensive rubber for the feet of the PJ.

Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #97 - 05/12/06 at 22:28:26
 
The center could go behind the screen.  Just turn the volume up for it to match.  You can also mount the PJ upside down, which can shorten the mount length by 4" and make it that much more stable.
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #98 - 05/12/06 at 22:52:50
 
As far as the center behind the screen goes, if it's not 'right' then I'd rather not do it. Without spending a bunch on "acustically transparent" screen material, I've not found a way to get enough 'regular' material in the cut out to adequitly [sp] hide the fact there's a hole there without severely muffling the drivers. I've played with center channel volume but in the end it just sounds like a pillow over a speaker, just louder. For the throw distance and screen size I've got, I really need a screen material with about a 1.5 increase in gain.

Don't think flipping the PJ upside down will give anymore vertical hieght. The lens is placed directly in the center (top to bottom).

Well, gotta go, 6:00pm Friday night. Leaving work. Chat with ya' Monday.  ;)

Bob

p.s. weather may be clearing for the weekend.  :( Angry Sad Angry
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John in CR
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Re: hz numbers on a 15" 2 driver
Reply #99 - 05/12/06 at 23:35:32
 
[quote author=Bob  link=1145573673/90#99 date=1147470770]Don't think flipping the PJ upside down will give anymore vertical hieght. The lens is placed directly in the center (top to bottom). [/quote]

You did need the weekend.  You mount the PJ to the bottom of that platform and shorten the supports for same overall height of lense, but shorter supports will be more stable.

BTW,  It's good to get away from the speakers behind the screen.

With a new screen, if you can lower the top of it, then you can raise the projector.

I want to see smileys on Monday.  Do that conversion on your HWK this weekend.
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morpheous85
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Re: hz numbers on a 15" 2 driver
Reply #100 - 05/12/06 at 23:46:22
 
When I was talking about a box around the projector, I was thinking that to be practical heat wise (and to be an improvement sound wise), it'd basically need it's own ventilation duct. Might just be easier to do the separate room thing.

Jason
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J_Rock
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #101 - 05/13/06 at 00:41:19
 
With the lowered ceiling above your PJjust throw another fan in parralel with the fan on the projector.  The place that fan in the ceilign tile.  Build a box with a cut out for you lens, so just the tip sticks out.

Fan sucks heat from projector into lowered ceiling.  Movie goers are totally isolated from sound of fans.  And Pj is better braced against vibrations.

Heres a pick: (minus the walls, so you can see)



Notice the awesome fan I drew up?
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« Last Edit: 05/13/06 at 00:41:41 by j_rock777 »  
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #102 - 05/13/06 at 02:33:11
 
That's not enough ventilation.  The only way I'd box up a projector is if I was sure the projector was getting more fresh air flow than the projector got naturally.  You would need some kind of ductwork going to the intake.  Most projectors have multiple fans front and back, plus another one to force air through the bulb housing.
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gexter
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #103 - 05/13/06 at 06:25:35
 
Anything I have to keep cool I keep it cooler.
I tend to replace anything with a fast moving loud fan with a larger slow moving one. preferably with twice the CFM.
Nasty habit left over from Being a PC modder and overclocker.
I also undervolt the oversized fan and then add or subtract resistors to find the temp I am comfortable with.
this applies to 12 v fans. you also have to watch for keeping the voltage higher than start up voltage.
if it don't spin at 7V you need another fan to use with a lower startup voltage, as an example.

I know you can build a circuit to solve this but I am too lazy.

Blowing air in and in bigger quanitities leads to more dust unless your filtering and then you have filters to check.
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« Last Edit: 05/14/06 at 14:33:20 by gexter »  
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #104 - 05/15/06 at 11:56:16
 
[quote author=John in CR  link=1145573673/90#100 date=1147473332]
I want to see smileys on Monday. [/quote]


Ok John, here's the smiley after the mods......  :(   Cry

I've got numbers, I'll be 'organizing' them today. Will post when they're in a 'readable form'

Bob
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