Film-Tech Forum ARCHIVE: Open Rack

This is topic Open Rack - Closed Rack in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mike Rendall (Member # 1499) on 02-18-2003, 11:21 AM:

Looking through the photo archive I see many american installations have open sound racks, i.e. all the rears of the devices are easily accessible. This I can see is good for certain maintenance applications, but don't you worry about cables getting snagged by accident? or dust etc? I prefer closed racks mainly because it keeps the cabling hidden out of view. What are other users preferences?

Posted by Richard Fowler (Member # 893) on 02-18-2003, 02:24 PM:

Open vs closed racking depends on many factors. Open racks are usually less than 1/2 the cost of a closed rack system. Most of the racks we manufactured in the past where closed style with about 10 - 15% open style. In some areas insurance cost was less to the cinema owner if the rack was a closed type.
Richard Fowler
Kinoton America Inc.

Posted by Joe Redifer (Member # 3) on 02-18-2003, 02:47 PM:

Moving to FHF.

Posted by Randy Stankey (Member # 64) on 02-18-2003, 04:43 PM:

If I was running a both solo, or with a group of trusted, experienced workers I would much prefer having the backs of the racks open for better troubleshooting, maintainence and cleaning. I would contend that, because racks need ventillation, they would get just as dusty inside whether they have open backs or closed backs. Cleaning an open rack would be much easier... and since the dirt is more visible they would get cleaned more often.

On the other hand, if the booth is full of inexperienced people, leaving the rack open is just begging for trouble. Being able to lock the backs of those racks keeps many an "idle hand" from causing trouble. I have worked in both kinds of booths and have seen booths with no backs on the sound racks have few, if any, trouble due to tinkering. The common thread was the quality of the personnel.

Another good reason to have the backs on the equipment racks is aesthetics. If your booth is viewable from the outside, it might be nice to have a "clean-looking" appearence.

Then again, there's a lot to be said for the "coolness factor" of having a booth where the backs of the racks are visible with wires neatly bundled and routed for maximum visual appeal! (And hopefully functionality as well!) [Big Grin]

Posted by Richard Fowler (Member # 893) on 02-18-2003, 05:09 PM:

Our closed rack systems we did in 2001 - 2002 we had our rack vendor supply us with full vent perforated rear door for ventilation since most amplifiers where equipped with fans. I personally hate the rack systems equipped with the 10 inch fan at the top since most of these suck the dirt into the cabinet and fight the fan equipped amplifiers air flow.
Richard Fowler
Kinoton America Inc.

Posted by Adam Martin (Member # 641) on 02-18-2003, 05:56 PM:

Mmmm ... Filtered rack fans. You'll note that the one on the left is hideously filthy. [Embarrassed]

Obviously, the one on the right has been taken apart to show the filter.

Posted by Steve Guttag (Member # 268) on 02-18-2003, 07:52 PM:

Open (relay) racks are definately the inferior way to go. A closed rack with a proper filtered blower (in the bottom) to pressurize the rack is the proper way. You won't have a dust problem and your equipment will run nice and cool.

As to the 10" fan in the top...you mean the "dirt pump"...that is about all they are good for.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 02-18-2003, 10:11 PM:

"Open (relay) racks are definately the inferior way to go. A closed rack with a proper filtered blower (in the bottom) to pressurize the rack is the proper way. You won't have a dust problem and your equipment will run nice and cool."

Steve,
What do you do with the power amps that take in air(and dirt) from the front? Do you reverse the flow of the fan on the rack to cover this and then just use a static intake filter?
More and more power amps seem to be going to that airflow route lately.... Crown is the only one I know that has any filters in place to cover that problem. Pressurizing the rack is fine as long as the power amps are taking in air from the INSIDE of the rack. Too much pressure in the cabinet will also impede these type power amps from being able to cool properly as the static output pressure(which is usually very small) would be fighting the racks much higher static air pressure.

P.S. I too vote for all enclosed racks. Almost all rack manufacturers make an inexpensive line of enclosed racks that list for way under $500.00....
Mark

Posted by Gordon McLeod (Member # 33) on 02-18-2003, 11:03 PM:

In some locations an open rack is illegal since the possible voltage on the speaker terminals exposed) exceeds class B wireing

Posted by Steve Guttag (Member # 268) on 02-19-2003, 07:43 AM:

Mark, whereas I only use QSC amps with proper "inside-out" cooling, that isn't a problem.

Any amp manufacturer that blows air into the rack is simply foolish. Think about it...you take cool air, heat it up with the amplifier, then send it into the rack to heat up other equipment? Just how stupid can you be?

As to Crown amps...watch out on their "grounds" on some models they aren't necessarily grounds and what you think your shield is connecting to isn't going to do much good. But they do have pretty blue LEDs on their CL line.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 02-19-2003, 08:54 AM:

Actually just flipping the fans around inside these amps will also take care of that problem. There are others out there other than Crown that cool from the outside to the inside as well....
Comming from a TV background where the entire stations rack system was force fed cooled air via the ceiling and the return was via the raised flooring. This was really a nice way to do things. I like any blue LED's...they seem to automatically draw atention to what ever one is mounted on. I'd have to credit Nelson Pass as being the first to use them in power ampliflers.

Having done alot of listening tests with different amps over the years on a high resolution home system I can honestly say that there are many commercial type amplifiers that are much better sounding overall than the QSC stuff, but I have found them adaquate and reliable and have pretty much given in to the QSC thing....QSC as a company also blows almost every other amp company out of the water.
Mark

Posted by Barry Floyd (Member # 385) on 02-19-2003, 11:26 AM:

quote:
P.S. I too vote for all enclosed racks. Almost all rack manufacturers make an inexpensive line of enclosed racks that list for way under $500.00....
Mark

OK, I need two of them.

Preferably wall mounted. Since I only have about 6 pieces of equipment to put in a rack, I don't really need anything big. I've seen some from Hubbel (sp?) that were like 24" tall, mounted on the wall, and hinge at the rear - so the whole cabinet swings out to access the wiring. They were listed as being for computer stuff, but I think they'd work in my application.

Posted by Ken Layton (Member # 133) on 02-19-2003, 03:12 PM:

Me, I'm cheap. I like open racks 'cause you can buy them for $100. brand new.

Barry:
Some wall mount cabinets don't have much depth for mounting sound equipment. Be sure to measure the equipment depth of what you'll be putting in the rack so you'll know if it will fit. Also, check out Mark's drive-in screen towers for sale on the Equipment forum here.

Posted by Adam Martin (Member # 641) on 02-19-2003, 05:42 PM:

Yeah, what Ken said. Those wallmount racks are pretty shallow.

They're pretty okay, though, if you're not trying to shove an amplifier in it.

Posted by Barry Floyd (Member # 385) on 02-19-2003, 06:16 PM:

I am looking for something like this

or a larger version like this...

I've found these particular models on the web for around $400.00 for the smaller one and $500.00 for the larger model.

Ken, I saw those screens Mark posted this morning and posted them over on the Drive-In Owners Forum. That post came about two weeks too late for me, as I've already ordered my screen from Selby, signed the contract and sent the check for a 30% deposit. The screen should be here in Tennessee in about 9 weeks.

Everyone told me Jerry knows how to build the best screens... and he sells them pretty good too! He and his wife offered to take us to dinner while we were in Florida and they even offered to babysit our boys so we could go out on the town! We turned him down on the babysitting job as I was afraid it would've made the cost of the screen go UP!... my boys are monsters!!