Post your Dead Vent and HVAC Pics - Page 2

This is a simpler and more efficient design.


There's really no benefit, per say. However when I built my room with two Dead Vents one of them has a 15' flex running to another corner of the room just as you've described.

The essential realization is that (except for the very high frequencies) sound waves will not follow the route of the flex. The low mass flex will not contain a sound wave. The sound wave will immediately pass through the acoustically transparent flex and start interacting with the insulation. This is why the DV is short and wide, while the soffit muffler is long and thin. Both have a great deal of absorptive volume.

So, the portion I've colored red between the Dead Vent and the wall...

Is there really drywall between the Dead Vent and the wall, or is the drywall / green glue shown there intended to show the drywall elsewhere on the other side of the wall where the dead vent isn't? If it's the former, I don't see how you could build the Dead Vent until you already put drywall + GG on both sides of the wall since you would lose access to that area due to the framing of the dead vent.

would there be any issues with installing a couple of these? i don't want my HT to get stuffy and I think two is better than one! One at the front of the room and one at the back... Now that we have a vent design, how about a cold air intake from outside (literally outside, not just the room)?

[engineer hat on]Changing the diameter of the pipe changes the impedance. The pipe is a transmission line for the sound, since the length of the pipe is more than the wavelength of the sound (except for very low bass). Creating an impedance mismatch in the transmission line causes some of the sound energy to be reflected back to the source rather than propagating through. That means less furnace fan noise in the HT and less HT noise leaking to the rest of the house.[engineer hat off]

Also a 12" duct has twice the internal surface area of a 6" one so, more absorption can occur over a given length.

You're building the wall, drywalling inside and out. hen inserting the 6" dia pipe through the wall.

Then you build the DV on that outside wall. The DV is completely outside the double wall.

Ok, I didn't understand that initially. That might complicate my plan to build one of them tipped horizontally up against the ceiling outside the room, but it still should be doable. I guess that also means you need to leave studs inside the wall at the right locations to connect the dead vent's studs on the other side of the drywall to later.

For the vertical one, since I'm building on concrete in the basement can I use PT lumber on the floor like normal for an outer frame and then use the inner framing on top of Delta FL + a plywood / GG / plywood sandwich as shown?

Yes. You don't want the pipe to contact the studs.


Yes, absolutely.

Since heat rises wouldn't you want to flip the orientation vertically so that the intake (HT side) is at the top, thus pulling from the warmest part of the room?

I think that depends if the DV shown is an intake or exhaust.

Hi Macboy - thanks for that, I get that but the important part from my perspective is ensuring the vent velocity is low so I dont hear the air moving in and out of the room i.e. basic fluid mechanics - narrowing increases velocity = bad

The one in the diagram is exhaust...

Hey Ted.. quick question...

I will be building a dead vent in a few weeks for a return vent that will be placed above the projector in the ceiling. Would this new design work in this scenario?...


Thanks..


HT Soul

HTSM, You can build a DV in the joist cavity, but it's a lot trickier.

Currently, I have the 6inch flex already routed between the ceiling joists from where the vent will be located to the outside of the room (around 4-5ft of flex). I can use your design to build the DV outside of the room. Another DV will be created to bow in outside air as well. This particular vent will be placed at the rear of the room, making the 6inch flex run even shorter.

P.S. - I will be contacting you guys soon to order more clips for hat channel installation..

The sound will leave the flex and enter your joists and subfloor. The flex has NO ability to contain sound.

Not sure if I would place a dead vent directly above the projector as this would draw warmed air from the room toward the projector. Instead, I would place a supply register at the projector and a dead vent someone along the perimeter. Of course, this assumes the intention is to cool the projector and not the occupants.

Since heat rises, there will be a somewhat draw of warm air initially. The purpose is to also draw the warm/hot air from the projector out of the room. I don't think placing a supply above the projector is a good idea. Warm air from your furnace during the winter would most likely make the project overheat. Closing the vent during the winter defeats the purpose of using that supply vent year round...


Ted,

I will green glue around the ceiling joists and pack with insulation if I have too. There is room to do this..

Hey guys, I have a question before the guys frame up and build dead vent. Does the fan get constant power or should it be on a switch? On a reostatic switch? They'll be here in the morning and I wanna be able to tell them.

At the very least I would put it on a 3 speed fan controller with an off position.

I'd hope to integrate mine into a system that can be temperature controlled (with on and off and variable speed controlled by temp) though I'm not sure how exactly I might accomplish that yet.

+1

Thank you for the prompt help, as always.

Here is a Lutron that can power up to 4 fans in case you need a supply and exhaust fan.
http://www.dimndimmer.com/ma-fq4fm.html

Cool. Thanks for the link.

Keep in mind that's only good for 4 1A fans. I'm not sure what the current rating on your dead vent fans is.

Ah, good point. I'll check it out.

Room air won't be more than 90 degrees (better not). While the air in the room may be warm to you, it isn't warm to the projector. You do want to pull hot air out of the room and a great place to do that is right next to a big heat generator (like the projector). The hot air from the projector doesn't have the opportunity to further heat the room (except by radiation ... for the panties in a knot obsessive/compulsive crowd).

I was thinking to pair something like this cooling line voltage thermostat with an infinitely variable rotary fan speed controller. I wish I could get an integrated product that would automatically control the fan speed based on temperature, but at this point I'm not ready to spend the money for a Phason unit and I haven't found anything else that will do the same for less.

I Went down that road also. I did not wind up with a temperature controlled fan system. However i installed two variable speed controllers. They are from lowe's and they control ceiling fans. Cheap

I'll be making an order from the Soundproofing Company for GG and clips. They provide much more detail on Dead Vents than this thread! Recommended.

Ted, if the room outside your theater is not noise sensitive, couldn't you locate the fan unit just outside of the dead vent? At the top of the drawing you posted? Seems like it would be better for maintenance and a slightly easier install.

Yes, you sure could.