Open Baffle Experience

I've owned a number of Magneplanars in the past, but my first real exposure to open-baffle was when I built a set of GR-Research NX-Oticas with OB servo subs a few years ago. This has been the most enjoyable system I've owned. I recently replaced the NX-Oticas with GR-Research Line Force speakers, which I would also consider open-baffle, but they use a line array of B&G planar-magnetic drivers. 

I have since heard a couple pair of Linkwitz speakers and the Spatial Audio X4s. 

All these open baffles have a characteristic sound - somewhat similar to panel speakers, but with improved dynamics (I haven't heard any Magneplanars newer than the 3.5r I owned, or their top models). 

Compared to the various box speakers I've owned (Duntech Sovereigns, Revel Gems, Revel Studios, Revel F50s, Totem Mani-2s, Goldenear Triton 2+), the open baffle speakers presented a deeper, wider sound stage where the speakers completely disappear, but the imaging is not quite as sharp.

The open-baffle bass does not pressurize the room as much, but is still very powerful with excellent definition. I find this a big advantage for music, but probably wouldn't work as well for movie sound effects. 

At this point, I can't see myself ever going back to box speakers. When I owned maggies, I always felt something was missing (although I enjoyed their sound very much), but this has not been the case with the NX-Oticas and OB subs.

I've only had the Line Forces running for a week. Compared to the NX-Oticas, the sound stage is a bit wider, the presentation (particularly vocals) is a bit more forward, and they have considerably more detail and sharper transients. They are quite a bit more efficient (at around 98db/w), so part of the improvements I'm hearing could be that they are a better match for my 300B Parallel SET amp. But even with limited break-in, these speakers are pretty stunning. 

I think all speakers sound best when they are given some space in the room (e.g. away from room boundaries), but open baffle speakers really demand this to achieve their magic. I have mine 7 feet from the front wall and about 3 1/2 feet from the side walls.

@peter_s - it was the X4 you heard at PAC. That's where I heard them as well. They were pretty impressive, particularly for the price (~8K). 

Don and Jay from Reference North Audio built my Line Force cabinets. They make a lot of the flat packs for GR-Research products (NX-Oticas, NX-tremes, servo subs). The Line Force cabinets are made from composite in order to be strong and stiff enough with all the driver cutouts, so they take longer to make and are considerably more expensive than the MDF flat packs. As far as I know, they are happy to make more of these cabinets.

GR-Research has NEO3 drivers available, but the Bohlender-Graebener NEO10 drivers are no longer available. I purchased my BG Neo10 drivers more than two years ago when they were still sporadically available.

Danny from GR has been trying to make a suitable replacement driver, but so far he hasn't been satisfied with the prototypes. Parts Express has their GRS 10" planar driver available, which can be used with suitable crossover changes, but this driver drops off quickly in the lower frequencies. Danny is working on a crossover using this driver, but I would expect he will have to compromise efficiency to get a flat response. They will probably sound great, but will need more power to drive them. 

This speaker is not inexpensive to build, even though you are only paying for the raw materials. I spent well into five figures for all the drivers, crossover parts, wire and enclosures. And this doesn't include the pair of open-baffle subs that are required since the Line Forces only play down to about 170Hz by themselves.

But they are pretty stunning, even without being broken in. I've heard speakers that rival these, but not many and all well outside of my budget. 

@mijostyn - Your projects sound very interesting, but I have to disagree on the notion of OB subs.

My open baffle subwoofers work exceptionally well and integrate seamlessly with the open baffle speakers. Each subwoofer uses three 12" servo controlled woofers in an H-frame enclosure. They deliver powerful bass down to 20Hz with lots of detail.

They don't pressurize the room like sealed or ported box subs which reduces the room mode problems and the amount of bass that escapes the room. 

Granted, you need more drivers to keep cone displacement reasonable, but they sound very natural. 

@mijostyn - I assume you haven't heard the H-frame open baffle sub system developed by Rythmik and GR-Research. I do use REW and a calibrated microphone to set up my subs. There are some minor room modes to contend with, but with a little parametric EQ to knock down the peaks, they play flat to within a couple db to about 22hz at the listening position. 

The amps, of course, adjust the output to compensate for the back wave cancellation, but the H-frame enclosures lowers the frequency where this has to start (compared to a simple flat baffle)  

I don't play my system at levels loud enough to damage my hearing, so generally keep peak SPLs below 90db, which sounds plenty loud to me. At these SPLs, I feel hardly any cabinet vibration. It's hard to feel the baffle directly since it's tucked inside the H-frame and is barely larger than the drivers. 

With six 12" drivers, these produce plenty of clean bass. I've heard Magicos at shows that sounded quite nice, but these were $85k speakers with $40k amps, which is more than I'm willing to spend, and I didn't think the bass was appreciably better than what I already have. The bass from my current subs is certainly far better than any box speaker I've ever owned, although I've never spent more than $20k for speakers. 

I'm sure there are excellent sounding box speakers and subs on the market. I'm not saying that my open baffle subs are better than anything else available, just that they easily hold their own for music reproduction, and blend seamlessly with my open baffle main speakers. 

@mwatsme - I don't believe the Spatial X4 uses a horn. I think the tweeter is an AMT design with a wave guide to control dispersion, but operated as a dipole (i.e. open in the back).

@mwatsme - yes, I agree that a narrow baffle helps make the speakers disappear by reducing the front baffle reflections. I think the wave guide used by the X4 does reduce the affect, but probably doesn't eliminate it altogether. I listened to a few songs on them at Pacific Audio Fest and thought they had a nice sound stage, but I wasn't that familiar with the songs that were played. 

One of the things I like about GR-Research's designs is that they use a folded baffle design so that the front baffle is as narrow as possible while still providing more separation between the driver front and back wave, lowering the frequency at which cancellation starts to occur. Like the Linkwitz speakers, they do a nice job completely disappearing 

On the other hand, I do find the Spatial Audio speakers somewhat more attractive. They have a nice clean look. 

I've heard some very nice box speakers, but they were also VERY expensive. As a percentage of production cost, a lot more of the expense goes toward the cabinet in high quality box speakers. An open-baffle speaker with comparable quality drivers and crossovers can be made for a lot less. 

When I first set up my open baffle system, I used GIK absorber/diffusers behind the speakers on the front wall. These are absorption panels with a plate mounted on the front with various holes. They are supposed to absorb low frequencies and scatter higher frequencies. I found that these deadened the sound too much and reduced the depth and airiness of the soundstage. 

I replaced these with Quadratic Residue Diffusors from ATS and these made a huge difference for the better. 

GR-Research offers a model called the NX-Studio which are designed for applications where the speaker can't be placed at least 3ft from the front wall. These are a two-way design with an "open-baffle" planar-magnetic tweeter and sealed woofer. The cabinet has an angled panel behind the tweeter which deflects the back wave up through an open top, so the rear wave bounces up and off the ceiling. 

These aren't quite the same as a full open baffle, but in a smaller room, they project a nice spacious soundstage. They don't play super low so a sub is required if you want deep bass. I have a pair in my bedroom system (13' x 15') and they sound very nice with an open-airy sound. 

I heard the Spatial X4s and Linkwitz LX521s at Pacific Audio Fest, and both sounded excellent. IMHO, the X4s were the best sounding speakers under $10K, and the Linkwitz were among the top rooms at the show (not my favorite, but certainly among the top 10).

@dz13 - I assume you are referring to the NX-Studios. I would say that, within their limitations, they are exceptional speakers. The NEO3 is one of the best drivers for upper midrange and treble that I’ve heard, particularly in an open baffle implementation.

These speakers won’t play exceptionally loud, and they don’t go very deep (maybe 65Hz) so if you are looking for deep bass, they need to be used with a sub. They also aren’t as efficient as GR-Research’s other models, but that’s true for most stand mount speakers.

I use them in my bedroom system (approximately 13’ x 15’) driven by a Purifi amp (DIY) and don’t play them particularly loud. With the jazz and folk music I typically play on this system, they are excellent - far better detail and soundstaging than the Totem Mani-2s I was using, with a sweeter sounding midrange, although the Mani-2s handily beat them in bass extension.