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Building riser, looking for advice on moving HVAC vent.

1003 Views 14 Replies 9 Participants Last post by SRSG, Jul 21, 2021

SRSG

Discussion Starter · Jul 19, 2021

I'm planning to build a riser for my HT, that would have a height of 1' but I have an HVAC vent right in the middle of it. Not sure how to move it. Should this be moved high up the wall or somehow extended so that the new vent is on the riser floor. Any ideas are welcome.

Thanks

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Charles Collins

· #2 · Jul 19, 2021

Assuming that it is a supply outlet (air blows out of it when the system fan is on) you could either move it up higher in the wall, or locate a floor register in the new floor of the riser. The floor registers are narrower and made of heavier gauge metal. Either way, just try not to block the airflow with furniture, etc. My thoughts are that it would be simpler to just move it up higher on the wall.

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markmon1

· #3 · Jul 19, 2021

SRSG said:
I'm planning to build a riser for my HT, that would have a height of 1' but I have an HVAC vent right in the middle of it. Not sure how to move it. Should this be moved high up the wall or somehow extended so that the new vent is on the riser floor. Any ideas are welcome.

Thanks

View attachment 3155941

I'd just extend it to the front of the riser. We did this on one of the installs. You can see the air vent facing front. (The holes are where 18" IB subs went)

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jaminkid

· #4 · Jul 19, 2021

Keep it low and extend the duct through the riser, you'll be glad you did.

SRSG

Discussion Starter · #5 · Jul 19, 2021

Assuming I want to keep the new vent on the floor riser, should I remove the existing register and replace it with something like this? (this might not extend enough)

Or remove the existing register, add a flexible duct and then add a new register?

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humanpersondude1

· #6 · Jul 19, 2021

markmon1 said:
I'd just extend it to the front of the riser. We did this on one of the installs. You can see the air vent facing front. (The holes are where 18" IB subs went) View attachment 3155975

Subwoofers below the seats on the Riser! W00! that is pretty awesome.

Charles Collins

· #7 · Jul 20, 2021

SRSG said:
Assuming I want to keep the new vent on the floor riser, should I remove the existing register and replace it with something like this? (this might not extend enough)

View attachment 3156036

Or remove the existing register, add a flexible duct and then add a new register?

What are the dimensions of the existing register (the opening in the wall)?

squared80

· #8 · Jul 20, 2021

Just extend it through your riser. Good opportunity to build some acoustical treatments into it, too.

SRSG

Discussion Starter · #9 · Jul 20, 2021

Charles Collins said:
What are the dimensions of the existing register (the opening in the wall)?

It's 10" x 4".

markmon1

· #10 · Jul 20, 2021

humanpersondude1 said:
Subwoofers below the seats on the Riser! W00! that is pretty awesome.

Yes, the riser was large enough for 2 18 inch subs in an infinite baffle install firing directly into the main seating. It turned out awesome.

Charles Collins

· #11 · Jul 20, 2021 (Edited)

SRSG said:
It's 10" x 4".

Here’s a link to a floor register that is 10”x4”:

Floor Register

Here is a link to a 90-degree flanged boot (the flange would make it easy to attach to the floor, but it is optional if you want to do it another way):

90-degree flanged boot

Here is a link to a straight flanged boot:

Straight flanged boot

The straight flanged boot could be fastened to the wall over the existing opening. Seal the joint with the wall airtight. If needed, run 6” round duct between the stackboot and the other boot to the location in the floor that you want to place the floor register. Insulate all ductwork. (Note, if this is the only supply air outlet in the theater, it might not be enough to offset the heat generated by the people and equipment.) I hope that helps, good luck.

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sirjaymz

· #12 · Jul 20, 2021

I would extend the venting into the riser, creating a heat/cooling vent up against the wall, about 4 to 6" way from the wall, depending how large the heat register you are going to use to make it 'look right' along with the kickboard trim installed on the wall. Additionally, instead of using the riser as a subwoofer box per se, I would use it as a bass absorption chamber, as designed by Dennis Erskine years ago. You would then cut holes into the riser, again, along the edge, replicating the heat register, and make them look like the heat register, but providing a different function for the room.

IMHO, this will make it look right, and have dual functions.

Here is a the link to the article. Post 36 of this thread.

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BIGmouthinDC

· #13 · Jul 20, 2021

I had the same thought of bringing it up through the top of the riser near the back wall assuming your back row chairs have some separation from the wall. Make the register bigger than the current one to slow down the air and make it quieter.

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DougUSMC

· #14 · Jul 21, 2021

Why don't you just put a 90 degree angle on it, and blow it up the back of the riser?

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SRSG

Discussion Starter · #15 · Jul 21, 2021

Thanks all for the guidance. I really like @Charles Collins idea of using the straight flanged boot that could be fastened to the wall over the existing opening. That way I don't have to cut the drywall and take out the existing flange. I would use a flexible duct and as others suggested install a register around the back wall along with some more vent for bass absorption.

I have around 3-4 feet behind the back row chairs and also have one more vent in the room, so hopefully, it would be enough to cool/heat the room.

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