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Addressing mid-bass null by adding sealed sub to existing ported sub

Sceri13

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Dec 8, 2021
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If there is another thread discussing the successful use of mixing a ported sub (for low extension) and using a second sealed sub for mitigating a mid-bass null at the listening position with extreme room acoustics and placement issues, please direct me.

In short, I have a primary mid-bass frequency response issue with many variables and limitations I would like to address.

I currently have a single HSU VTF3 mk5 (15” ported) in the front right corner of the front stage wall (only placement option for a large ported subwoofer in the room). I have a ~6 db null in the 50 to 80 hz range, relatively strong output from 30 to 50 hz, and then a fairly steep progressive drop at 35 hz and below at the listening position. 30 hz may be the best I can ultimately hope for in terms of meaningful extended low frequency output.

I would like to address the 50 to 80 hz null to make music sound better, for now. I do not have the space to add a second VTF3. I would like to use a sealed subwoofer (such as the HSU ULS15 or SVS SB3000), with a high pass filter at 40 hz or so, to fill in the mid-bass region by utilizing strategic subwoofer placement of this second sub. Both listed sealed options have similar output to the ported VTF3 in the mid-bass region.

Room is huge given open floor plan and large opening to other areas. ~17,000+ cubic feet counting main and connected open areas. I know. My seating position is also the middle 40% of the room relative to the front stage wall. Nothing in this room is ideal and I accept the reality within the limitations.

I will only use two subwoofers total. I will use Audyssey XT32 Multi EQ (with Audyssey app) on a MARANTZ SR 8015 and any applicable subwoofer eq setting functionality for room correction.

I cannot utilize room treatments to any meaningful end given main living area aesthetics.

I know the common sentiment is that one should not mix ported and sealed subwoofers, but given I am only interested in addressing the mid-bass null, this seems a practical, if an imperfect approach at an attempt to retain the lower frequency response of the ported subwoofer in my problematic room.

Use is 50% music, 45% TV /movies, 5% gaming.

My goals are:

—Maximize subwoofer placement options via a smaller enclosure to achieve primary goals. 15” to 16” (18” max) width and depth.
—Mitigate the mid-bass null.
—Even bass frequency response. Yes, I know to properly pressurize my room and meaningfully increase frequency response down to 20 hz levels, I would likely need multiple Marty Subs. When I finish the basement….

Budget is $1200 to $1,500 for the second sub.

Given the above, would adding a second sealed sub-woofer such as the SB3000 (or ULS15) be worthwhile, in this scenario, to achieve my goals? I almost prefer the SB3000, only because it provides for the most placement options given its smaller dimensions. In the future, I may try dual sealed (and omit the ported) to see if the ability to strategically place both subs (instead of just one) improves anything in lower extension.
 
Disregard, the crossover switch on the back of my subwoofer somehow was flipped to in instead of out. That coupled with a 40 hz crossover setting on the sub vs 80 hz on my receiver was wrecking havoc on my frequency response.

I plan to stick with the one sub given I am now getting good enough results, all things considered.
 
Kudos for the posts. We learn, if we are first open to learning.

Glad you got it sorted :)
 
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