GR Research NX-Otica and Servo OB Subs


I am amazed that these speakers (and other models from GR Research) have not garnered more attention on Audiogon. For about $6K, and 40-50 hours of work, I now have a set of speakers that is, by far, the best speakers I've ever owned. And I have owned some fairly good speakers including Tympani IVs with Entec servo subs, Duntech Sovereigns, Revel Ultima Gems with dual Revel Ultima Subs, Revel Studios, among others.

The NX-Otica, along with GR Research's other speaker designs, are DIY designs. I know that scares a lot of people off, but they are really not difficult to build. For the NX-Otica and stereo triple 12" open baffle servo subs that I built, GR Research has teamed up with a woodworking company to produce MDF flatpacks which just need to be glued up to create extremely robust and well constructed cabinets. GR Research provides everything else.

The NX-Otica is an open baffle design with a narrow (~8 inch) front baffle and side wings to reduce dipole cancellation. The driver complement is a planar magnetic NEO 3 tweeter (in a wave guide), two 6 inch midrange drivers with phase plugs in an MTM array. The wave guide allows the tweeter to cross over fairly low, while the midrange phase plugs allow the driver radiation pattern to more closely match the tweeter at the crossover point. Four 6" woofers complete each tower.

The NX-Otica by itself only reaches down to 40-70Hz depending on the room, and are designed to be used with the servo open-baffle subs. I finished the NX-Oticas a couple weeks before the subs, and in my room they didn't really sound that bass shy on most recordings, but the subs really complete the package.

The crossover components supplied by GR Research are stellar quality with a mix of heavy gauge copper coil inductors, copper foil inductors, sonicaps, miflex copper bypass caps. In other words, these crossovers put most crossovers you'd find in sub $20K speakers to shame.

I've never built a DIY speaker before, and I think I jumped into the deep end with these speakers. The large number of drivers and fairly complex crossover make this a somewhat more challenging project than many kit speakers, but they really weren't that hard to build and Danny Ritchie from GR as well as numerous other builders on Audio Circle, are there to help.

There are obvious downsides to this system: You have to spend some time to build them unless you pay someone else to do it for you which ups the cost. Their complex front baffle shape makes them hard to veneer although some builders have veneered the side panels. I decided to just paint the whole speaker. This was by far the most time consuming part. I don't have great painting skills and have never painted anything like this, but they came out fairly nice. I think if you had another couple $K to invest, you could take the built cabinets to a cabinet shop or auto-body shop and have them professional sprayed and could get a much more professional finish.

Open baffle speakers aren't for everyone. They need a fairly large room. I have mine in a 17' x 27' room, with the front of the baffle about 6 1/2' from the front (17') wall. The two cabinet per channel design takes up a lot of space.

And probably the biggest downside is resale. Even if more people knew how good these speakers sound, finish quality is an unknown, so it's unlikely a buyer would be willing to buy them sight unseen.

But the upsides are huge. For a relatively modest investment in time and money, you get a speaker system that sounds amazing. They have the open, airy sound of magnepans with more precise imaging due to the narrow baffle. They have thunderous, fast bass that doesn't energize lateral room modes and transmits a lot less of the bass energy through the walls. They are efficient (93db/w), easy to drive, and very dynamic, with a beautifully smooth and detailed midrange and high end. Vocals - both male and female - sound amazing.

Sorry for the very lengthy post, but it's hard to stop gushing about these speakers. I've only heard a few other speakers that sounded all-around as good to me as these, and they were ~10 times the cost.
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Showing 8 responses by jaytor

@bdp24 - Thanks. If you are interested in hearing them sometime, send me a PM. I live nearby in Portland. 

It was Danny's Tuesday Tech Talk videos that got me interested in these. I had been seriously considering the Tekton Moabs, but after watching these videos, I was convinced that the open baffle NX-Oticas were the better choice for what I was looking for. 

My background is electronics engineering and I took a few graduate level acoustics courses way back when. Everything Danny says jives with my understanding about speaker design. 
The Line Force is a new design Danny is working on that uses a line array of 16 NEO3 planar magnetic tweeters (the same one used in the NX-Otica) and six NEO10 planar magnetic mid-range drivers. 

This speaker design is not yet available primarily because the NEO10 drivers are out of production. Danny is working on creating his own version of these drivers but isn't ready for production yet. 
These OB subs are unlike any other subs I have heard. If you've heard the bass from large magneplaners, you'll have some idea of what these sound like, but the GR Research OB subs go much deeper and perhaps with more energy than the large panels. The -3db point in my 17'x27' room is around 14Hz (with the rumble filter off) - not that there is much music that low anyway. 

They are extremely impressive on acoustic instruments like double-bass and large drums. The sound is very deep and powerful without sounding boomy. They don't seem to pressurize the room like a typical sub, but still create a lot of bass energy. Sort of like the bass that is created when a big truck goes by. 

A nice side effect of this type of bass is that it does not energize room modes as much - particularly side to side and floor to ceiling modes - so the bass is much smoother (you can achieve similar results by using 3, 4 or more separate closed-box subs at different locations in the room). Also, you can get a lot of bass energy in the room without the bass transferring through the walls to the rest of your house or your neighbors. 

As I stated in my original post, the downside is that they have to be at least a few feet from the front wall (although they can be placed directly against the side wall - firing front and back). 
@brewmasterdon - You and Jay do great work! I was really impressed with the quality of the flat packs and how easy they went together. 

I'm watching Danny's development of the Line Force with some interest. My wife would not be happy if I built another speaker system any time soon, particularly at the cost these are likely to run, but maybe in a couple of years... In the meantime, the NX-Oticas are pretty spectacular and I'm sure are far from the weak link in my system.

@sunshdw - I think you could probably get away with placing the speakers a bit closer to the side walls, particularly with a little acoustic treatment, but distance from the front wall is more important. Keep in mind that this is the distance from the front baffle to the wall. 

In my fairly large room (17' x 27' x 8'), the NX-Oticas by themselves were reaching down into the mid 40's Hz range. For a lot of music, this was just fine.  I think in a smaller room, they'd reach even lower.

That said, I'd probably be looking at one of Danny's smaller designs for a room your size. Maybe the new Super Mini design (once Danny has the NEO10 drivers ready) mounted on a sub of some kind. Give Danny a call and discuss what you're looking for. 

- Jay
To answer your second question, I haven’t personally tried my system in a room like this, but others have indicated that open baffle speakers, particular OB subs, have worked much better than traditional speakers in this kind of environment. 
I suggest you post your questions in the AudioCircle GR Research forum. There are a lot of participants in that forum that have a lot of experience with Danny’s various designs. 
I haven’t listened to either these, but according to Danny Ritchie, the designer:

The Super Mini is not available, is a little faster and more articulate.  

The NX-Otica MTM is available, plays down lower, has more body and weight. 

And they sound more alike than different. 
Danny is working on re-engineering the NEO10 (which is no longer available from the original manufacturer) which is the larger planer driver used in the Super Mini. 
Don - I had five people come over last weekend for a listening session. Everyone seemed to be very impressed with the sound from the NX-Oticas and subs. A couple of them commented that they had never heard bass that sounded so natural, and everyone commented how well the sound fills the room such that you can be well out of the sweet spot and still get decent imaging and great tonal balance.
@sortner Hi Steve - I'm glad to hear you liked them enough to build your own set. It was fun to show them off to you and the rest of the group. Good luck with your project!