[hawkeyejw]

Looking for input from anyone that has switched from more classic sub designs to OB for home theater. What has your experience been? What did you switch from? How is the watching experience different?

Having recently switched from vented floor standing speakers to X-Statics/Voce I’m really impressed with how dynamic they sound. I’m enjoying the open baffle sound signature so much that I’m starting to think about OB subs to replace my vented PSA sub down the line. I’m a little hesitant though as I’ve seen people say they’re not as great at HT. My question is why? What do standard sealer or ported designs do better in the HT arena?

[Early B.]

Not exactly the same question; nevertheless, your answer lies here:  https://www.audiocircle.com/index.php?topic=171048.msg1811884#new

[Sonicjoy]

 The difference has to do with the way they interact with the air in the room. Sealed and ported subs actually pressurize the room where as open baffle's move the air in the room back and forth rapidly. Take a sealed sub. You have a sealed box with a driver, as the driver moves out with an impulse it is actually expanding in size like an inflating balloon. This causes a pressure increase in the room. OB drivers being open to the room simply move back and forth without creating pressure. They just move the air back and forth with the drivers. As an example think of an explosion as pressurizing a room like a sealed sub and then a kick drum being like an open baffle sub just moving the air back and forth. That is why sealed subs are great at reproducing explosions and why OB subs are better at music.

Hope that helps and is understandable.

[hawkeyejw]

Thanks guys. Conceptually I get what you’re saying but I’m still trying to figure out how the experience is different when listening. So for example, an explosion in a movie. Are you losing the couch shaking effect with open baffle? Chest slam? General feeling of weight to the boom? I love having real texture to the bass which is basically the hallmark of open baffle, but I’m just not sure how to imagine the difference from the perspective of actually listening to a movie soundtrack.

As another example, if you’re familiar with the movie Open Range, the gunshots are recorded in that movie in a way where a really good system with top notch dynamics produces a tremendous chest thump when the gunshot happens. Do open baffles have the ability to reproduce this?

Thanks for taking the time to answer and give some insight. At some point I’ll have to buy some and try for myself. I’m just very curious why something that reproduces the intricacies of music bass wouldn’t also reproduce the textures and variations of movie bass with the same satisfying effect.

[mlundy57]

Conceptually I get what you’re saying but I’m still trying to figure out how the experience is different when listening. So for example, an explosion in a movie. Are you losing the couch shaking effect with open baffle? Chest slam? General feeling of weight to the boom?

Yep, that's the difference. If you want to shake the couch, rattle the windows, and get punched in the chest/gut by the explosions, you need a sub designed for HT use, either sealed or ported. While you can use either type of sub for either use (music/HT), if you want to get the most out of an OB system that is used for both music and movies, you need both types of subs.

[Danny Richie]

It's really a matter of how much of a kick in the chest you want.

I measured a pair of dual open baffle servo subs hitting peaks of just over 115db on 25Hz notes in a room that was 23 by 17 with 9 foot ceilings. And they maintain a linear response to below 20Hz.

You get that same gut punch, but without the room boom that follows.

And if you want even more SPL then just use more woofers.

[Hobbsmeerkat]

It's really a matter of how much of a kick in the chest you want.

I measured a pair of dual open baffle servo subs hitting peaks of just over 115db on 25Hz notes in a room that was 23 by 17 with 9 foot ceilings. And they maintain a linear response to below 20Hz.

You get that same gut punch, but without the room boom that follows.

And if you want even more SPL then just use more woofers.

Is a monster 6-Woofer setup possible with a single plate amp, or would 2 be required for each set of triple subs?

[Danny Richie]

Is a monster 6-Woofer setup possible with a single plate amp, or would 2 be required for each set of triple subs?

The HX800 amp will drive 6 woofers but only in mono and all in one tower.

For stereo subs you have to use two amps.

[Hobbsmeerkat]

The HX800 amp will drive 6 woofers but only in mono and all in one tower.

For stereo subs you have to use two amps.

Yeah I guess i should have clarified that I meant 1 or 2 amps for each 6-woofer tower.
But imagine a pair of monster OB subs towers on either side of the NX-Tremes or LineForce.. you'd probably need a stand for each plate amp, just to keep the runs as short as possible. 

[hawkeyejw]

It's really a matter of how much of a kick in the chest you want.

I measured a pair of dual open baffle servo subs hitting peaks of just over 115db on 25Hz notes in a room that was 23 by 17 with 9 foot ceilings. And they maintain a linear response to below 20Hz.

You get that same gut punch, but without the room boom that follows.

And if you want even more SPL then just use more woofers.

Thanks Danny, this is really helpful. I’ve been wondering if at least part of it was just having the extra headroom to hit reference or near reference peaks at the lower frequencies or if there’s more at play.

My most memorable theater subwoofer experience to date was at a hifi shop a few years back that had a full top end Wisdom Audio setup including one of their STS subs which is a dual 15” horn sub about the size of a refrigerator. What stood out to me most was how much that subwoofer didn’t draw attention to itself. At one point my pant legs were flapping yet there was no obvious explosion rumble or other low bass harmonics that I was hearing. It was just so well integrated and accurate and detailed, I loved it. I have been wondering for a while if that same kind of experience (or even better) would be possible with OB subs assuming you have enough displacement and headroom to hit those SPL peaks. I’ve also been wondering what could be done with the right 15” or 18” driver in an OB alignment using Rythmik’s servo technology for those of us with one room to house both HT and 2 channel listening in the same place. I fully acknowledge that may not be a great idea, but I’m trying to learn more about how OB subs work and the differences in sound signature to other subs for different source material. I appreciate everyone’s input on their experiences.

[Hobbsmeerkat]

Since I enjoy doodling random ideas for speakers I thought it’d be fun to design a quick 6-sub tower. Of course it’ll probably end up running 6.5’-7’ tall.. but there’s not much fun in being realistic.

[RonP]

but there’s not much fun in being realistic.

I say to myself.. This guy 'gets it'. 

[hawkeyejw]

Lol, MOAR bass is always the answer.

[Tyson]

I never run out of headroom in my 12 x 18 room in the basement using a pair of dual servo OB subs.  I cannot even fathom how much 6 would get you!

[Zarkoff500]

FWIW - I went from a sealed 12" SVS to a ported 12" SVS to a sealed 18" to a DIY ported 12" to a small ported 18", small ported 15", back to DIY 12" and finally a two manifolds of six 12" OB.

The point of the overshare is I have had a lot of different subs before going OB and the OB is significantly better in terms of sound quality and overall home theater experience vs the others. I have significantly more headroom and the tactile response from my attic mounted baffles is very immersive.

[mojave]

Most home theaters, at least ones I've been in and design, are a sealed room. The pressure zone in a room starts at the following formula:  speed of sound in ft/sec divided by 2x the longest room dimension. For a 14 foot long room, the pressure zone starts at 40 Hz (1125/(14*2) = 1125/28 = 40.18 Hz).

This frequency is also called the cut-off frequency. From Recording Studio Design by Phillip Newell, "Dipole radiators, including most electrostatic loudspeakers, cannot radiate sound below the room cut-off frequency, and only at very small distances from the front or rear of the diaphragm will any sound be perceived." Open baffle subs are dipole radiators and aren't the proper subwoofer to use in a sealed room. If your room isn't sealed, then you will have more success in reproducing bass below the cut-off frequency.

[Dynky]

FWIW - I went from a sealed 12" SVS to a ported 12" SVS to a sealed 18" to a DIY ported 12" to a small ported 18", small ported 15", back to DIY 12" and finally a two manifolds of six 12" OB.

The point of the overshare is I have had a lot of different subs before going OB and the OB is significantly better in terms of sound quality and overall home theater experience vs the others. I have significantly more headroom and the tactile response from my attic mounted baffles is very immersive.

That's a pretty large variation in sub-sizes you've experienced...may I ask how large the room is you currently use those 12 x 12" OB's in?

You say attic mounted, that sounds pretty unusual.
I'd think an attic is closed off from the actual listening space, so seems more an IB then OB by principle, no?
Do you have pictures from the OB's available?

@mojave: my room isn't sealed, so I'm still in doubt whether to try two stacks of triples...some say it won't work, others say it will 

[Tyson]

Most home theaters, at least ones I've been in and design, are a sealed room. The pressure zone in a room starts at the following formula:  speed of sound in ft/sec divided by 2x the longest room dimension. For a 14 foot long room, the pressure zone starts at 40 Hz (1125/(14*2) = 1125/28 = 40.18 Hz).

This frequency is also called the cut-off frequency. From Recording Studio Design by Phillip Newell, "Dipole radiators, including most electrostatic loudspeakers, cannot radiate sound below the room cut-off frequency, and only at very small distances from the front or rear of the diaphragm will any sound be perceived." Open baffle subs are dipole radiators and aren't the proper subwoofer to use in a sealed room. If your room isn't sealed, then you will have more success in reproducing bass below the cut-off frequency.

Yet when I measure bass in my basement with my dual OB subs it's flat to 20hz. 

[Zarkoff500]

That's a pretty large variation in sub-sizes you've experienced...may I ask how large the room is you currently use those 12 x 12" OB's in?

You say attic mounted, that sounds pretty unusual.
I'd think an attic is closed off from the actual listening space, so seems more an IB then OB by principle, no?
Do you have pictures from the OB's available?

@mojave: my room isn't sealed, so I'm still in doubt whether to try two stacks of triples...some say it won't work, others say it will 

You are correct it is an IB set up not OB. I got too excited to share and misread as IB.

For the IB, the room is an open design ~ 4000cft, living room with a fireplace in the middle flowing into the kitchen.

[Vince in TX]

Most home theaters, at least ones I've been in and design, are a sealed room. The pressure zone in a room starts at the following formula:  speed of sound in ft/sec divided by 2x the longest room dimension. For a 14 foot long room, the pressure zone starts at 40 Hz (1125/(14*2) = 1125/28 = 40.18 Hz).

This frequency is also called the cut-off frequency. From Recording Studio Design by Phillip Newell, "Dipole radiators, including most electrostatic loudspeakers, cannot radiate sound below the room cut-off frequency, and only at very small distances from the front or rear of the diaphragm will any sound be perceived." Open baffle subs are dipole radiators and aren't the proper subwoofer to use in a sealed room. If your room isn't sealed, then you will have more success in reproducing bass below the cut-off frequency.

Well, this just threw a monkey wrench into my thought process.    The room where I have my current setup isn't closed (upstairs game room open to the lower level), and it's running a single SVS PB-2000.   The new room I'm putting together will eventually be a dedicated media room, and it's sealed.   I was planning on stereo OB (duals), but now I may have to rethink that.   I saw Danny had a kit for an IB design with a single 12", but I'm not sure if those would move enough air in this size room.   Decisions, decisions.