Down-firing, rear-ported Hsu VT3-3 Mk2 vs front-firing, front-ported replacement - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 2 Old 04-06-2020, 12:09 PM - Thread Starter
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Down-firing, rear-ported Hsu VT3-3 Mk2 vs front-firing, front-ported replacement

Hi All,

I'm reconsidering subs for my space, and would like some feedback on some thoughts I'm having.

I currently have a 5.1 setup with a Hsu VTF-3 Mk2 being run from a Denon AVR-S730H. For <too long a story> reasons, I'm replacing the AVR-S730H with an AVR-X3500H, which has Audyssey XT32, and independent sub calibration for room correction.
I'm happy with the VTF-3 Mk2, but I've been wanting to experiment with something involving dual subs, and I'm now in a position to try it if I want to.

My drawing skills with MS Paint are limited, so I'll try to describe the space:

The room is a finished section of the basement. It's a rectangle in shape, roughly 32.5' wide, 12.5' across, and 7' high (~2850 ft^3). It's set up so that the viewing area takes up about 40% of one end, across the 12.5' side. Seating is a sectional sofa in the corner where the right side and rear are directly against exterior walls. Listeners are about 11'-12' from the screen/speakers. L/R speakers are about 14'-15' apart.

The Main Listening Position (MLP) is centered to split 2 sections of the sofa, 5 total sections across the rear exterior wall. To the MLP's right is 2 more sections, then an exterior wall. To the MLPs left is one more section, then the open space of the rest of the room before drywall separating a small office. Behind the screen/speakers is drywall separating the finished area from a larger unfinished area behind it. This wall, and the unfinished area are the reasons for this post.

The office, the unfinished area, and the top of the stairs all have doors which are typically closed when watching, making the room pretty much a closed box. The room is carpeted, over cement, and has dropped ceiling tile.
Another way to describe the entire basement is to think of it as a shoebox, and inside that is another box representing the viewing area in the lower right corner that's half the short side "tall", and 80% of the long side "wide".

Noting that many subs have upper frequency ranges that may be localized by listeners, I've toyed with the idea of dedicating a sub to the left and right of the main channels, telling the AVR to treat the speakers as "large" and leaving the sub channels empty. With the AVR-X3500H, I could also use the independent sub channels though.

As I'm researching front-firing (so the potentially localizable sounds face the user), front-ported subs, a thought occurred to me: The VTF3-Mk2 has its dual ports (one's plugged for low extension, so I guess it's singular) in the rear, and firing against the large drywall separating the viewing area from the large unfinished part of the basement. Is the drywall behind the screen acting as a diaphragm for the VTF3 and making the unfinished part of the basement a very large box for the VTF3? If I go with dual front-firing front-ported subs, will it take away this effect, or is the room being pressurized regardless of the direction of the ports? If it is acting like a diaphragm, would another rear-ported sub hitting the same wall interfere with the effect?

Any thoughts appreciated.

Last edited by philpoe; 04-06-2020 at 01:44 PM.
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post #2 of 2 Old 04-06-2020, 12:24 PM
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Subs arent really very directional unless you cross over at very high frequencies so better to place them where they sound the best. Not where they would be closest to the main speakers. (Which often is a bad location for lower frequency response)

The dual independent sub outputs on the denon 3x00 series is still mono, the delay and volume settings are independent. Most stereo recordings have mono bass anyway and where you hear it from is dictated by the higher frequency parts of a “sound”.

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