Does port spacing simulate multiple subs?

That’s a great question.
I’m sure it would help spread the port sound on each side of the room, but won’t act like 3 subs like your expecting it would


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Personally I think you'd be better off with a pair of NSWs than buying a single HS24 (about the same price - contact Kevin at GSG for AVS pricing). I've modeled the HS24 ported with the NSWs in devastators and the HS24 is behing until you reach mid-lower teens. With lower tuned martys the NSWs would have the advantage even further down. Typically speaking in most cases with capable drivers 2 subs is going to be better than one.

I have thought about this alot as it relates to room modes. All of my reading, leads me to believe that the greatest affect will be around the tune frequency. It would not be uniform across the frequency range. But better than one single sub imo

clint357 said:

I am going to start working on a dedicated theater room this winter (hopefully), which will be 13ft x 23ft. I have been thinking about using the SI HS-24, but my $2k sub budget would only allow for one sub. I know that having one sub in the middle of an AT screen would not give a flat response across all seating locations as well as multiples but then I started thinking about where the ports are. If I were to build a box that is a little over 8ft long with the sub in the center and a slot port at each end, would it actually give a smoother room response because of the wide port placements? Would this be similar to having three subs up front that are four feet apart?

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Plug your room dimensions into REW's Room Simulator, then add your speaker and seating locations. Remember to put in ear height at seating locations and center of woofer height for speakers.

Fiddle with your sub location(s) and watch the frequency change at the seating positions. Spend some time doing this until you start to find the best locations (don't forget to try it with one sub's polarity reversed, as well).

Choose the location(s) that provide the best compromise for you. In my room, with two subs, the best location was 1/3 of the way across the front wall, and about 2/3 of the way down the left wall.

Many compromise for aesthetics, it turned out that those locations worked well in my room.

No. A port is a Helmholtz resonator and only operates in a fairly narrow band around tuning.

One large problem I see with this sort of large enclosure is you will get an internal resonance along it's length that will be in/near passband.

A9X-308 said:

A port is a Helmholtz resonator and only operates in a fairly narrow band around tuning.

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That doesn't change the principle of multiple sound source locations.

But its effect is limited to modes that may be in the ports' narrow operational range.

noah katz said:

That doesn't change the principle of multiple sound source locations.

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Never said it did, but I'd be surprised if more than 1 of a thousand rooms actually got a discernible performance difference from doing this. You would need to design the sub to the specific room and the location of it's modes that happened to be in the passband of the port.

I agree with everyone else, 2 grand would be much better spent on 21s or 18s. Putting 2 grand into some PA460s, GRS GPT18s, Krakens, Vortexes or something else in those sizes would yield a build that I'd gladly put up against an HS24 build.

bigjack7679 said:

I have thought about this alot as it relates to room modes. All of my reading, leads me to believe that the greatest affect will be around the tune frequency. It would not be uniform across the frequency range. But better than one single sub imo

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The only significant affect would be at the output of the port, which is predominantly at the tuned frequency.

If you're talking about a subwoofer big enough where the ports can be significantly spaced, it's probably tuned pretty darn low, like low 20s or in the teens, in which case, are you really getting room problems in those frequencies?

It's always nice to try things and see, but my guess is that it would be a waste of time.

Thank you for sharing your knowledge. I figured that I was not the first to think of this. I will probably go with a pair of diy subs for now and possibly add rears in the future if needed. I will surely start another "What subs should I get for $xxxx" because there hasn't been one in a couple weeks.

Port tune is typically very low where wavelengths are in the tens of feet; they are too close together to make a difference

Question: Could the ports be external to the box? For example, extend pipes out to the sides of a normal sized box instead of making an oversized box. If they are all behind a false wall and out of sight, then the appearance wouldn’t matter. I agree that it wouldn’t affect the modes as well as three separate subs. But this arrangement might allow for longer port lengths than would be feasible if they were entirely inside the box. Has anyone tried this?

Port area is port area. Whether you wrap it up neatly in the enclosure or extend it out beyond.

I wanted the best of both worlds with Project Smol Boi so I build a massive enclosure in a massive box with a crap ton of large drivers. However you make it happen is however you make it happen.

Most often, enthusiasts have to deal with WAF (or HAF) and it's hard to build whatever performs best without making compromises in that regard.

Charles Collins said:

Question: Could the ports be external to the box? For example, extend pipes out to the sides of a normal sized box instead of making an oversized box. If they are all behind a false wall and out of sight, then the appearance wouldn’t matter. I agree that it wouldn’t affect the modes as well as three separate subs. But this arrangement might allow for longer port lengths than would be feasible if they were entirely inside the box. Has anyone tried this?

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I guess that approach could also help users who can't get enough port length in a small box to tune low enough. Just have it extend out into the room, and blow directly your pant legs for that tactile feedback enhancement.

Charles Collins said:

Question: Could the ports be external to the box? For example, extend pipes out to the sides of a normal sized box instead of making an oversized box.

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Yes.
Long port options for subwoofers (subwoofer-builder.com)

Why ported? Can you build IB? I would opt for more drivers spread out over one Uber driver as long as spl is the same.

^^^ This

I would not spend that much on one driver with so many multiple options. I have owned so many subs and drivers and once I went cheap IB I am a believer. My regulars agree.

clint357 said:

I am going to start working on a dedicated theater room this winter (hopefully), which will be 13ft x 23ft. I have been thinking about using the SI HS-24, but my $2k sub budget would only allow for one sub.

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The best way to flatten your frequency response and QR-passport forehead-tattoo is to just passively wait 2 more weeks. 👁 All joking aside, you might be better off with a pair of pro 21inch woofers as most (90%) of the bass from music and movies is covered by the frequency range they are optimized for, that is to say: 30-300hz.
Which is a function of the total combined efficiency of the driver(s), their power handling, and to a lesser degree excursion. By the time my 16 PA-460's move even 2mm's one-way, the SPL is close to 140db. By the time they hit 5mm's it's like 147db. 16 x 99db/w/m & 16kW burst do that.
i.e. They spend most of their time not moving at all. Most normal humans can't tolerate watching a movie at the level that would actually strain them.