Under Garage Home Theater Build

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ecut1
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Re: Under Garage Home Theater Build

#46 Post by ecut1 »

Thanks Bill, I was hoping corners would work but I'll try some other options. Do you think a sub crawl would work with this pair? And to do a sub crawl, which direction would I fire the horns (from the seating position) during the sub crawl?

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Bill Fitzmaurice
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Re: Under Garage Home Theater Build

#47 Post by Bill Fitzmaurice »

It doesn't matter which way they fire, the output is omni-directional.

ecut1
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Re: Under Garage Home Theater Build

#48 Post by ecut1 »

Ok, cool. I'll place them side by side where the couch will be and try to find the best spot for them. Hopefully it's not where the door to the room is. Lol.

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Re: Under Garage Home Theater Build

#49 Post by ecut1 »

Well, my son and I spent a couple hours last night finding the best spot for the table tubas. They ended up in the right rear corner of the room side by side. There is one dead spot in the middle of the room between the couch and the screen. Pretty much everywhere else in the room is pretty nice. I think the manufacturer of the projector screen I bought designed it to rattle. :? Also, the exterior door we installed slaps the weatherstripping when it vibrates and makes a pretty loud rattling sound. Lots of work to do there! When I stand on the other side of the theater I can feel the sheet rock slightly vibrating. So from the inside out you have... 5/8 sheetrock, 2x4 wall insulated with fiberglass, one inch gap, 8 inch poured concrete foundation, one inch gap, 2x4 wall insulated with fiberglass, 1/2 inch sheetrock (which is vibrating). So I give up on sound isolation! At least now things don't fall off shelves on the main floor above the theater room.
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ecut1
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Re: Under Garage Home Theater Build

#50 Post by ecut1 »

I have added a row of seats to my theater and I'm planning to add a riser with a third row in the back. The riser will be 13' (width of the room) by 13' deep. The rear section 13'x6' will be around 20" off the concrete floor and the front section 13'x7' will be around 12" off the concrete floor. I'll fill it 75% full of rock wool insulation, drill 3-4 inch holes in the front face between each joist, add holes in the rear subfloor with HVAC grills, etc. My question is about sub placement... Currently I have placed one table tuba in the front right corner of the room under the screen. The other one is in the back of the room in the opposite corner. The room sounds very nice with this setup (this is after a couple years of use and many different trial and error placements). Once the riser is built, the rear sub would most likely end up in the same place, the rear center, or the opposite rear corner. When they are both placed in the front it sounds pretty weak. Is there anything I should be planning other than the items I listed to maximize the sound of that sub? On the other hand, is putting the sub on top of a hollow (stuffed with rockwool) riser going to completely change the sound (maybe for the better or worse)?

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Bill Fitzmaurice
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Re: Under Garage Home Theater Build

#51 Post by Bill Fitzmaurice »

Weak bass when both are in front usually means you've got a null from the reflection off the wall in the back of the room. The cure is to not have both in front.

ecut1
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Re: Under Garage Home Theater Build

#52 Post by ecut1 »

Another thought I've had is to build a THTLP to go inside the riser at the back of the room. I could cover it and access it via a hatch in the floor like a crawlspace. Seating would be right on top of it. Then I could put both table tubas in the front. Only issue is I'd have to know the placement pretty much at the beginning of the riser build. Is this worth looking into?

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Bill Fitzmaurice
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Re: Under Garage Home Theater Build

#53 Post by Bill Fitzmaurice »

I'd forget about having two subs in the front. It's a bad idea, period.

ecut1
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Re: Under Garage Home Theater Build

#54 Post by ecut1 »

I've been wanting to try a THT for a long time. I couldn't fit it in my last house but this new room is the perfect place to try it. Do you think the best plan would be 1 TT and 1 THTLP? There's room for both TT's if I put the THTLP under the riser. The second TT could go on the floor of the riser right above the THTLP or it could go in the opposite rear corner. Other option is the THTLP on the floor of the riser (not under the riser) and put the other TT in a different room in the basement.

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Re: Under Garage Home Theater Build

#55 Post by Bill Fitzmaurice »

TT and THTLP have different phase response. While you may be able to mix them it's best not to use different subs, as the outcome is unpredictable.

ecut1
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Re: Under Garage Home Theater Build

#56 Post by ecut1 »

THTLP is done. I think it sounds very good with the TT's but I do plan to do some measuring soon (mic is in the mail). As far as placing the THTLP under a riser in the back of the room. Does the mouth of the horn need to be directly connected to the airspace in the room? Basically, if there is some perforated (several two inch holes) subfloor covered with carpet and pad will it have an adverse impact to the sound? Do I need to keep the mouth completely free of obstructions to the airspace inside the room?

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Re: Under Garage Home Theater Build

#57 Post by Bill Fitzmaurice »

You may not need any direct connection to the airspace, but one can't say without trying it.

ecut1
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Re: Under Garage Home Theater Build

#58 Post by ecut1 »

I guess I should measure without the riser... then start building the riser in phases and if I start to see problems I can leave a corner of the riser open to the room. Would you recommend adding holes in the riser rim board and all the insulation, etc. to make the riser a bass trap? There's all sorts of info about this online. Seems like an experiment to me... building a bass trap to correct something that can't be measured until the bass trap is built. :confused:

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Re: Under Garage Home Theater Build

#59 Post by Bill Fitzmaurice »

It is an experiment. What's critical is that it will have to be very solid or it will vibrate like mad.

ecut1
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Re: Under Garage Home Theater Build

#60 Post by ecut1 »

Good thing my home depot sells PL premium in 28 oz tubes. :lol:

Is there any point in trying to use the vibration to my advantage? I've seen plans for resonators but most of them are very specific designs tuned to reduce certain frequencies. Could the riser be built air tight and ported in a way to increase bass frequencies where my room is lacking?

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