Why don't we see more bottom vents?

PretzelB · Post by **PretzelB** » Tue Mar 09, 2004 5:07 am

After seeing more of what Bluefront is doing with his cases I'm starting to wonder why we more people don't try adding a bottom vent to their case. Here are some random thoughts on the idea:

* Seems like it's easy to do since all cases give you easy access to the bottom.
* Allows you to add custom filters easily.
* Filters can be replaced / cleaned easily (no bezel to remove)
* Goes with the "natural" flow for case design (ie you're not trying to pull air down, the cool air is pulled up)
* Won't change the look of the case and if you scratch something it won't show.
* Should be (not sure) better for noise since the bottom of the case is further from you ear and it's not pointing towards you like the front bezel typically is.

Maybe I'm just getting bored and looking for mods to do on my Chenbro. My temps do drop when I take off the front bezel but I find a fair amount of dust in my case and the provided filter is a pain to clean.

aphonos · Post by **aphonos** » Tue Mar 09, 2004 7:58 am

Hmmmm. Thought I replied to this last night???

This is a great question and certainly worthy of discussion.

PretzelB wrote:* Should be (not sure) better for noise since the bottom of the case is further from you ear and it's not pointing towards you like the front bezel typically is.

I think that depends on the surface underneath the computer. Carpet or foam will serve as a dampener, but hardwood or vinyl flooring might reflect sound. Something to consider.

Another consideration is making sure that a bottom-mounted intake provides adequate airflow over the HDDs to keep them cool. IMO, this means either having the vent far enough forward to let air pass over the traditional HDD mounting/suspending location (having it this far forward may negate the sound advantages that come with moving the vent to the bottom???) or we need to come up with another way to mount HDDs that puts them in the airflow from a bottom vent.

sthayashi · Post by **sthayashi** » Tue Mar 09, 2004 9:33 am

A bottom vent would be absolutetly horrible if the case had small or no feet, and you put it on a shag carpet. Most of the cases I've seen had very little clearance under the computer, so you'd really be limiting your airflow if you're not careful.

The flip side is that if you put tall feet on there, you've effectively increased the height of your case, which can be a problem under some desks.

HammerSandwich · Post by **HammerSandwich** » Tue Mar 09, 2004 9:44 am

PretzelB, I've been playing with the design of a custom case for a while now, and a filtered bottom intake is key design point #1. I'll post when (if?) I get the design completed, but it will be no time soon. I encourage people to look at this themselves - it's really clarified my thinking about what I want in a case, what the manufacturers are doing poorly, and how difficult the compromises can become.

aphonos · Post by **aphonos** » Tue Mar 09, 2004 9:48 am

sthayashi wrote:A bottom vent would be absolutetly horrible if the case had small or no feet, and you put it on a shag carpet. Most of the cases I've seen had very little clearance under the computer, so you'd really be limiting your airflow if you're not careful.

True, but if you're gonna cut the bottom of your case to install a custom vent, we'd hope there'd be 'nough sense in yo' head to raise the case off the shag carpet, too.

The flip side is that if you put tall feet on there, you've effectively increased the height of your case, which can be a problem under some desks.

Good point....need to put feet on the desk to raise it up, too.

Seriously, that's a good point.

Another consideration: Unfiltered bottom intakes would make for a dirty PC even faster than a front intake does.

Bluefront · Post by **Bluefront** » Tue Mar 09, 2004 4:40 pm

There is at least one more important consideration here. Most tower cases are very top-heavy, what with the PSU, CPU heatsink, optical drives, on the top of the case. When you raise the case with feet or castors, it does really become easy to tip over, and particularly so when sitting on carpet.

Something to consider when doing this mod.....like we need more problems.

PretzelB · Post by **PretzelB** » Wed Mar 10, 2004 8:35 am

Case height is a problem for me. I have a desk which has an area for the case and it's about 18" tall. I suppose if you got something short like an Antec 635 or 660 you could raise it a bit without much trouble. The advantage of storing your case in your desk is no thick carpet so I probably wouldn't need that much room.

I hadn't considered the hard drives, which would be a problem if you had some kind of suspended hd method. If you could also mount a fan to the bottom of the case and have it just blow some air on the drives it might help, but that's more mounting required.

I would guess you would need to seal the rest of the case to make sure the air came in where you expected. I should probably just leave it alone!

Bluefront · Post by **Bluefront** » Wed Mar 10, 2004 7:20 pm

Ok.....thought about this for a while (keeps me from getting bored at work). Here's one of the solutions I came up with.

Ambient air to the front fan...

Quite a few cases have aprox 3/4" space between the left panel and the drive bay cages. You could construct a duct in this area going from the space next to the front fan, all the way through the case, with an opening at the rear of the case. This duct could be maybe 5" tall, 3/4" deep, and the lenght of the case deep.

This duct would enable the front fan to draw air from the rear outside of the computer, without going under the computer. The case could sit on the floor without being raised. I think the area of that sized duct would be ok for a 80mm fan....maybe bigger. This Black Knight case I'm working on, has enough space for ducting like this design. It would be a rather easy build.....hmmm. All the intake noise at the rear.

PretzelB · Post by **PretzelB** » Thu Mar 11, 2004 3:45 pm

Great idea. I look forward to seeing pictures with detailed instructions showing me how it's done!!!

Bluefront wrote:Ok.....thought about this for a while (keeps me from getting bored at work). Here's one of the solutions I came up with.

Ambient air to the front fan...

Quite a few cases have aprox 3/4" space between the left panel and the drive bay cages. You could construct a duct in this area going from the space next to the front fan, all the way through the case, with an opening at the rear of the case. This duct could be maybe 5" tall, 3/4" deep, and the lenght of the case deep.

This duct would enable the front fan to draw air from the rear outside of the computer, without going under the computer. The case could sit on the floor without being raised. I think the area of that sized duct would be ok for a 80mm fan....maybe bigger. This Black Knight case I'm working on, has enough space for ducting like this design. It would be a rather easy build.....hmmm. All the intake noise at the rear.

Gooserider · Post by **Gooserider** » Sat Mar 13, 2004 7:46 pm

Bottom holes don't HAVE to be intakes either... In my case, I have a 'split' shroud that divides my 2-342 heater core rad into an upper and lower segment, each with it's own 120mm fan sucking through the rad. The rad is located in the front lower left face of my server cube case, and is the primary air intake for the system.

The upper segment blows air out into the rest of the PC case, where it will circulate over the non-WC'd components and cool them before getting sucked out the back by the PSU and 2 120mm x 25mm undervolted fans.

The lower segment forms a duct that runs down at an angle to a 120 x 38mm fan blowing down and out through a hole in the case floor, so the airflow is basically in, through the rad and back out again. I'll be putting a skirt around the base of the case (which is on casters) so that the hot air and noise will be directed out towards the back of the PC to avoid getting any air recirculation between the rad intake and the output. I might also put some sound absorber on the bottom of the case to reduce noise reflections (the floor is carpeted)

This is a bit of an unusual approach, but other folks doing water cooling might consider it.

Gooserider

Kalel83 · Post by **Kalel83** » Sat Mar 13, 2004 8:56 pm

Gooserider? I've read sereral times in this fourum it is best to work with the whole heat rises mo, why didn't you account for this if your setup, if it is blowing out toward the bottom? Perhaps for a space this small it isn't nessisary?

dexton · Post by **dexton** » Sun Mar 14, 2004 3:50 am

yeah the bottom vents idea has been in my head for a while too, since I saw the Verax case VX-1:
http://www.verax.de/catalog/detail5.jpg
http://www.verax.de/catalog/detail4.jpg (some kind of air filter)

it is also mentioned as the "chimney effect" (click the star in the bottom of the case)
http://www.verax.de/verax.php?SID=65964 ... entryid=48

I have a Chieftec super miditower right now. I am using the lower fan grill for cold air intake, the rest of the front is pretty air tight. Exhaust through a Seasonic SS-300FT PSU with a 120mm fan at maybe 800rpm. I do have a problem for making holes in the bottom of the case though... I have some noise damping material in there. Maybe Its still possible to drill through it? Ill think about it until the next weekend and see if I do it

http://aegd.cjb.net/dexton/osorterat/case_current.jpg

other changes that are pending: change the Zalman VGA Heatpipe cooler for a Arctic VGA Silencer, to get that hot air out. Maybe buy a Verax P14Cu, though VERY expensive. Im also very interested in getting a Raptor though that one will be a challenge to get quiet+cool.
hmm, maybe you can also see in my case picture that my PSU is modded...
http://aegd.cjb.net/dexton/osorterat/finished.jpg

// Johan

Bluefront · Post by **Bluefront** » Sun Mar 14, 2004 4:08 am

Here's a bottom vent I put in a Black Knight case. Made from a 4"x10" floor register vent....can be closed off from the outside, or adjusted partially open. The case temps went down dramatically when this was installed, allowing the two 120mm case fans to run at their slowest speed.

luminous · Post by **luminous** » Sun Mar 14, 2004 10:58 am

I'm all for fitting vents at the bottom of cases. I'm about to modify the front bezel of my old case for just this effect. The small problem that I have run into is that I don't know where I can buy some case feet that are at least 1 inch tall.

I know I could make some, but bought ones that are ready to mount into the standard size "foot holes" of cases sound like an easy solution. Anyone know where I can source some in the UK? All I have found so far are some blue LED ones (one wire to each corner plus power connections - just too many wires).

fmah · Post by **fmah** » Sun Mar 14, 2004 3:41 pm

One of the biggest problems I've seen is that people will put them on carpet or other places with lots of dust. Then the unit sucks in all the dust and messes up the fans. However, if the height were enough that would probably be less of a problem, but for the typical user it can be trouble.

luminous · Post by **luminous** » Sun Mar 14, 2004 3:57 pm

You need to have filters fitted to any inlet fans. With old machines you could get away with it as they did not disapate that much heat, and therefore did not have high case airflow

halcyon · Post by **halcyon** » Mon Mar 15, 2004 1:12 am

I think bottom intake vents along with feet to raise the case and exchangable filters are a great idea, that's been unused for too long.

I already have hard time cutting my case, but this would be the next mod I'd do if I had proper tools.

Of course, some noise is bound to escapre through that hole, but as instructed it is always possible to place the case on a piece of carpet (if you have high enough feet for the case).

regards,
halcyon

PretzelB · Post by **PretzelB** » Mon Mar 15, 2004 4:48 pm

Bluefront wrote:Here's a bottom vent I put in a Black Knight case. Made from a 4"x10" floor register vent....can be closed off from the outside, or adjusted partially open. The case temps went down dramatically when this was installed, allowing the two 120mm case fans to run at their slowest speed.

Hey Bluefront,

Is there no filter on this bottom intake? I seem to remember you used a filter on your other bottom vent. Maybe this is just a picture without the filter attached?

Trip · Post by **Trip** » Mon Mar 15, 2004 5:35 pm

check out the next picture.

Bluefront, is the case fan an intake or exhaust (can't remember)?

Bluefront · Post by **Bluefront** » Mon Mar 15, 2004 5:45 pm

Since that's only a passive vent, you couldn't put a restrictive filter there. I put a common thin vent filter there....it's the exact size. The rear case fan blows out, and draws air through that vent. Seems to work very well.

Gooserider · Post by **Gooserider** » Fri Mar 19, 2004 10:40 pm

Kalel83:
Gooserider? I've read sereral times in this fourum it is best to work with the whole heat rises mo, why didn't you account for this if your setup, if it is blowing out toward the bottom? Perhaps for a space this small it isn't nessisary?

It is always better to work with the natural convection aircurrents when you can, but it isn't essential. Those natural currents are pretty low volume, so it doesn't hurt all that much to over-ride them with a fan, as even a low volume undervolted fan moves much more air than would otherwise flow.

OTOH, a blowhole in the top or side would have let more noise out and directed it towards me. Not that a top blowhole was even possible since there are drive cages above where I put the rad. I also think top blowholes are a bad thing since that nasty gravity stuff makes things fall into them

Side blowholes also let noise out, plus they restrict where you can put the case since you can't push that side of the case up against a desk or wall that might block them.

The bottom exhaust solves lots of problems for me. Since the bottom half of the rad will be slightly hotter than the top half (single pass rad, with the flow entering at the bottom) I'll be directing the hottest air out of the case. The noise skirt around the bottom front of the case will also give me good seperation between the intake and exhaust airstreams, and give me freedom about where I put the case. Lastly, the height difference is only about 5" max as the air simply enters the case, goes through the rad (sideways) and then gets blown right back out of the case again.

Gooserider

will0957 · Post by **will0957** » Thu Apr 15, 2004 7:47 pm

This is just a thought that popped into my head.

You could cut out 2 bottom vents on your case. Put a grill underneath the case. Mount 2 hard drives over them. Then on the inside of the case, enclose the hard drives in their own little box or something.

That way the drives are always getting fresh air. There are no fans making noise. The drives aren't increasing the overall case temp because they are enclosed.

Just a thought...

Bluefront · Post by **Bluefront** » Fri Apr 16, 2004 2:17 am

Wait a second....if the drives are inside the case, and you have either passive or active airflow over the drives, heat from those drives goes somewhere. If your PSU and rear case fan are blowing out, the hard drive heat gets sucked through the case.

If your drives are in front of a fan blowing right out of the case, the heat has little effect on case temps....but few cases are designed this way. Of course you could mount the drives externally, and cool them with their own fan.

External hard drive enclosure

sthayashi · Post by **sthayashi** » Fri Apr 16, 2004 5:12 am

will0957 wrote:You could cut out 2 bottom vents on your case. Put a grill underneath the case. Mount 2 hard drives over them. Then on the inside of the case, enclose the hard drives in their own little box or something.

That way the drives are always getting fresh air. There are no fans making noise. The drives aren't increasing the overall case temp because they are enclosed.

If I didn't know better, I'd say you stole that idea from BlueFront's article. But his idea is more refined.

Genesis · Post by **Genesis** » Tue May 04, 2004 1:59 am

I am assuming that most people have their cases on top of desks - now my idea is a bit more radical - but why not cut a hole in the desk under the hole in the case and put a pipe through so that it takes the cold air from under the desk reducing noise and getting cold air - of course you are still gonna need a filter if it is a low to the ground draw that you have the case in

Trip · Post by **Trip** » Tue May 04, 2004 2:54 am

Sounds like a great idea, take that a step further and build a computer in your desk.

Rusty has a really good example of a desk case, though you can always improve these things.

ashtray_head · Post by **ashtray_head** » Tue May 04, 2004 3:28 am

Am pleased with the bottom vent I put in my case...made a big difference
Not sure it would make such a difference on a case with good airflow, mine's a 6070

Steve Rosenthal · Post by **Steve Rosenthal** » Tue May 25, 2004 10:36 am

My case has a bottom vent but very little clearance. Here's what I did about it (based on reading this thread

).

http://forums.silentpcreview.com/viewtopic.php?t=12780

--Steve

Why don't we see more bottom vents?

Why don't we see more bottom vents?

Re: Why don't we see more bottom vents?