[Bullitt5094]

I'm curious about the GR OB subs. I currently have dual opposed 15s in a 24"x24" sealed enclosure powered by two Crown xl-1000s. The are wired in-phase and have really worked well. What can I expect if I change the polarity where they are out of phase? Will they produce similar effects to the OB subs? Honestly I'm not completely sold on the OB theory. I was hoping this would be at least a reasonable experiment without having to jump in with both feet on an OB build. Thanks!

[Early B.]

The most important aspect of GR Research's OB subs is the servo technology. That's what makes them sound so good.

And, no, if you wired your drivers out of phase, you wouldn't produce similar effects to OB subs.

I would suggest doing some research on OB subs. Start here:   http://www.rythmikaudio.com/technology.html

[Bullitt5094]

That is very good reference material. Thanks! I really had most of that from other information from the RA and GR sites so I knew the theory prior to my first post. And I also pretty-much knew GR followers were likely to Poo-Poo the opposed driver box trial. I may yet try it though.

I'm sure a better controlled transducer using closed loop control will improve the sound. I don't doubt that at all. What I doubt is the OB sub thoughts. I get that the rear wave reflecting within the box as a bad thing. In an IB configuration I can see as a very good solution to this. But letting the rear wave loose in the room in an OB configuration? That's a stretch for me. At least a box will contain most of the rear wave energy. But I am open-minded and would love to experiment with this but with a reasonable investment until I know it is truly workable and superior to other solutions.

I have no problem with DIY enclosures and could build those easily. That isn't a problem. But I certainly don't want to spend the minimum $800 for the small GR OB kit and discover it doesn't sound any better than what I have now. Or if it's better than a servo controlled sealed enclosure system. Maybe if there was a GR trade-in/up policy I would order the OB system and try it. Then if I wasn't impressed I could return it for a sealed box system package. But I don't see that option being available. I know GR products are good. I built and still own a pair of XL-S speakers and really like them. I just can't get comfortable with the OB Sub concept enough to throw that much money at it without some monetary safety net or in-home trial.

[Danny Richie]

I'm curious about the GR OB subs. I currently have dual opposed 15s in a 24"x24" sealed enclosure powered by two Crown xl-1000s. The are wired in-phase and have really worked well. What can I expect if I change the polarity where they are out of phase? Will they produce similar effects to the OB subs? Honestly I'm not completely sold on the OB theory. I was hoping this would be at least a reasonable experiment without having to jump in with both feet on an OB build. Thanks!

What will happen is that you will have the output of one woofer but the motor structure of two woofers to move it. So your box volume has to get cut in half otherwise they bottom out easily.

But letting the rear wave loose in the room in an OB configuration? That's a stretch for me.

Your current subs already produce just as much energy to the front of the room. They are playing in an omnidirectional range. The sealed box doesn't contain any rear wave energy as per what is going on in the room. The OB design doesn't change that. But it cancels at 90 degrees off axis. And front room pressure is out of phase from back room pressure. And that dissipates quickly and doesn't load the room.

But I certainly don't want to spend the minimum $800 for the small GR OB kit and discover it doesn't sound any better than what I have now. Or if it's better than a servo controlled sealed enclosure system.

As anyone that owes the servo controlled OB woofers can attest, it will not only sound better than what you have, but better than anything else there is. There really is nothing else like it on the market.

[Bullitt5094]

And front room pressure is out of phase from back room pressure. And that dissipates quickly and doesn't load the room.

As anyone that owes the servo controlled OB woofers can attest, it will not only sound better than what you have, but better than anything else there is. There really is nothing else like it on the market.

Thanks for taking the time to reply Danny.
Noting your front/back room pressure comment... do the OBs have to be oriented with drivers facing the front and rear walls?
I'm also curious as to why Rhythmic doesn't offer the OB design if it's a superior application of their product. I see they offer a 45 day return plus return shipping policy for their enclosed units. But they don't offer an OB design to try.

[Early B.]

I'm also curious as to why Rhythmic doesn't offer the OB design if it's a superior application of their product. I see they offer a 45 day return plus return shipping policy for their enclosed units. But they don't offer an OB design to try.

Of course, Danny can provide better insight for this question, but one thing that comes to mind immediately is the market. Rythmik wants to sell what consumers will buy. Most people don't have the space or the wife acceptance factor for OB subs. Quite frankly, most OB subs aren't particularly attractive, either. Plus, you really need two dual OB servo subs to make them work well for 2-channel audio, so that becomes expensive and consumes a lot of real estate. Box subs will always be favored for these reasons.

[nickd]

The GR DYI servo sub kits are not what I would call “budget gear”. I would put them in the ultra high end at a $$$ extreme value category. There is really nothing like them out there for the price.

I have owned lots of subs over the years. Including GR O.B. Subs and GR sealed servo subs. You can’t go wrong with either. Depends on your room, taste and main speakers.

The O.B subs when pared with reference level O.B main channels that will play strong down to 150hz and can be placed 3’ or more from the back wall are very hard to beat. You might consider the Steinway Lyngdorf Model D in the same catagory if you have $150,000. of disposable audio funds. Many would argue the servos in the GR system would be cleaner.

I’m using 2 of the GR sealed servo 12’s in a stereo configuration with PEQ370 amps. They are close to the wall and down firing. Other than possibly a full Servo “swarm” I am convinced I couldn’t have better bass in my room.

If you want a 40hz PA style boom, pro 15” drivers in a good horn or ported box with 1000 watts might be the ticket.
If you want to hear a drum kit actually appear in your room, the O.B servos can’t be beat.

[Tyson]

I've been saying for years that the servo OB bass is the best you can get.  It's still true.  To get the best sound, you must use it in stereo, you must place them fairly close to your main speakers, you must have them 3 feet from the rear wall and you must point them firing forward toward the listening spot. 

What you will get is the cleanest, clearest bass you have ever heard.  And at the same time, bass that can punch you in the chest. 

As for why it's not more widely used, well most audiophiles are timid and tend to shy away from anything that's even a little different from their past experiences.  Servo OB subs, even though MUCH better than box subs, just don't have the history or marketing that boxed subs do.  Plus (because of placement requirements) have WAY lower spousal acceptance factors.  A box sub, even a big one, at least can be tucked away into a corner.  OB subs cannot. 

[mlundy57]

Something else to remember about Rythmik Audio is that their primary market is home theater. For the ultra low frequencies and dynamics in the low frequency effects (LFE) channel that rattle the windows and shakes the couch, you want a sealed or ported sub designed for this purpose. Brian Ding of Rythmik told me the OB subs are designed for music, not explosions and star destroyers.

I have my OB subs in the front of the room and connected to play with both music and movies. However, they are connected to the home theater AVR through the AVR's front left and right channel pre-amp outputs (via the HT by-pass setting in my main pre-amp). Additionally, I have a 12" sealed servo sub connected to the AVR's subwoofer out (LFE) channel. This sub only plays when watching movies and there is a signal in the LFE channel. This setup gives me the best of both worlds.

[Jaytor]

do the OBs have to be oriented with drivers facing the front and rear walls?

The OB subs have a null toward the sides due to the cancellation that occurs when the out-of-phase back wave interferes with the front wave. So you want to have them oriented front-to-back in the room to get the most output and least room interaction.

I'm also curious as to why Rhythmic doesn't offer the OB design if it's a superior application of their product.

The GR OB subs produce the best bass I've ever heard for music.  They are incredibly clean and detailed and go down very deep. But OB subs sacrifice some quantity in order to get better quality. You'll want multiple drivers per side to make up for this. If all you're looking for is thundering bass for movie sound effects, a sealed sub or two tucked in the corner(s) will get the job done for a lot less money and floor space, and don't have to be placed well out into the room.

As nickd pointed out, the GR/Rythmik OB subs are not a budget solution. A pair of dual subs would have to sell for $6K to $10K to make reasonable margins, and this prices them out of the market for all but serious audiophiles. So it's not at all surprising that Rythmik has decided to focus on the main stream market with less-expensive sealed box models.

[Early B.]

The OB subs have a null toward the sides due to the cancellation that occurs when the out-of-phase back wave interferes with the front wave. So you want to have them oriented front-to-back in the room to get the most output and least room interaction.

How does this null work for a sub in the rear?

I have a third dual servo sub in the rear behind the seating position and the drivers are facing the side walls, not front to back. The sub seems to sound better that way instead of front to back. However, I haven't done a lot of experimentation with placement yet. 

[Jaytor]

I think you will get less output directly toward the listening position, but you'll get strong reflections from the rear sidewalls which will help to fill-in the bass and reduce peaks and valleys from room modes. This might be preferable for a rear sub since at the upper range of the sub, the direct signal may have an adverse affect on the image specificity. I'm just speculating here since I have never tried this.

[Bullitt5094]

Thanks for the feedback from the folks that actually own these.
A bit more info on my system. These subs will be specifically used in a two channel system. They will be in a HT, but the only components the HT system uses from the 2-channel system is the Lyngdorf 2170 amp in Theater (passthrough) mode and the two Tekton Ulfberht mains. My dual opposed Dayton 15" 390-HO subs do an excellent job on LFE with the HT. And a pretty darn good job in music mode also. But I'm looking for improvement in the 2-Channel music system. So if the OBs don't rock the house, that's OK. The 15s/Crowns will more than handle that.
And my wife is very accepting of this hobby and enjoys it with me. Note, the Tektons are about 7ft high. After that, I don't think these will be a problem.

[emailtim]

... And my wife is very accepting of this hobby and enjoys it with me. Note, the Tektons are about 7ft high. After that, I don't think these will be a problem.

You need a set of stereo 6's to match your 7' mains.  That should, rock-the-house.   

[Bullitt5094]

You need a set of stereo 6's to match your 7' mains.  That should, rock-the-house.   

What the hell does that mean?

[Early B.]

What the hell does that mean?

I believe he means two stacks of these OB servo subs built by Hollis Audio Labs....these subs will test your wife's acceptance of your insanity.

[Sonicjoy]

With Danny's design you can add as many drivers as you want. If you go the modular single driver enclosure rout you can add more as you can afford as time goes on. (In fact the ones in the above photo look to be the modular singles stacked to get six high.)That needs to be planned ahead of time to allow for proper wiring with the amps. See this thread for more info: https://www.audiocircle.com/index.php?topic=139480.340

[HAL]

Since I have a dedicated listening room, there is no testing of the wife's tolerance. 

I highly recommend a dedicated listening space.

[Bullitt5094]

I've communicated with the Rythmic Audio folks several times over my application and the use of the OB sub design. They do not recommend the OB sub unless used exclusively with OB mains and only in a 2 channel configuration. They state they are inefficient and do not have the low end extension a conventional sub is able to, and should, attain. They state the best configuration for great sound reproduction and good bass extension would be the dual opposed 12s or 15s. Seems that is their preferred design. I figure they know their product and I've decided to take their recommendations. I really get the impression they sell the OB systems only to the diehard OB believers. Which they are not. That would certainly explain why they don't offer an OB sub as a product offering. I've decided on the dual opposed configuration RA is recommending. 

Don't kill me. I'm just the messenger.

[DeeJayBump]

The overwhelming majority of Rythmik Audio's customers are Home-Theater oriented, with 2-channel enthusiasts being a small if not miniscule percentage of that. GR Research's customer base is the opposite. So what [Rythmik] said makes sense from that perspective.

OB sub setups are primarily for those who desire the best 2-channel and occasionally multi-channel bass reproduction there is for music rather than home theater. When OB owners want to match or exceed the bass slam, SPL and low frequency extension of sealed or ported servo setups, they simply do so with more drivers like Triple, Quad or 6 driver per side OB setups.

There's also the cost factor to consider as well. Rythmik's highest Servo Sub offerings are ~$2500. A 2x12" stereo pair of OB H-frames start around that price and go up from there as more amps/drivers are desired. There are many more folks who are willing to spend $600-2500 for subs than are willing to purchase stereo OB setups for $2300-2500 or more.