Open Baffle Experience

I own the Spatial Audio M3 Sapphires....so count me as an OB fan. AC has a whole section devoted to OB not specifically sponsored by any manufacturer...here is a link for some light reading.

My general overall comment about OB sound is most of the advantages of a panel speaker but with some of the advantages and dynamics of a box speaker as well...without the supposed box sound.

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.

I heard a set of Spatial speakers, can’t remember the model bit less sensitive ones, at the Pacific Northwest audio show, and was very impressed. I like them more than the linkwitz. I would like to know more about the GR research line. Particularly whether it is still possible to still put together a pair of line force. @jaytor do you know? But also just how they compare to other open baffle offerings.

If you think open baffles are great, then just remove your drivers from your speakers right now and throw your wooden boxes away folks. You will be shocked how horrible your speakers sound without them. You have been warned. I’m sure Magico and others would not go to all the time and trouble to produce such expensive cabinets if the answer was as simple as having no cabinet at all!

Do not listen to folks who claim open baffles are better than box speakers. They probably cant afford state of the art box speakers which can cost hundreds of thousands of dollars. Its just sour grapes

@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. 

This site desperately needs an eyeroll emoji.

The suggestion to just throw away the box is somewhat simplistic in that the bass and midbass will sound weak. The better sounding open baffle speakers don’t have this issue because the designer selected drivers to compensate and produce a balanced sound. 
 

OB speakers are not inherently better than box speakers… they are different sounding… on some instruments the tone sounds more correct… but as noted the bass pressurizes the room differently. 
 

I’ve heard great box speakers, panel speakers and OBs… and the nice thing about shows like CAF is you can usually hear them all, albeit different rooms and gear. 
 

They are definitely worth a listen. 

@jaytor Thanks for the information. That is really helpful.

To the naysayers, I heard the X4 speakers at the Pacific Northwest audio show, and they were very impressive for their price.  Not out of the park better than any speaker I heard there, but they really stood out for having an organic and natural sound for a lot less money than many of the conventional speakers I heard. I will likely try them out since there is a 60 day audition period, I believe.

secretguy

1,106 posts

11-12-2022 at 04:25pm 

This site desperately needs an eyeroll emoji.
 

🙄

FWIW, I've heard @jaytor 's system (maybe with the old subs) and thought it was among the very best I've heard, including some costing far more. It's clear to me that, if designed and set up carefully, OB systems can be really outstanding.

@erik_squires 

I’ve had Maggie’s, Ohm F’s and I still have Acoustat model X’s and they do project the sound differently. Many times I’d swear the music was coming from behind me. I’m not sure it’s exactly the same as the Spatial Audio’s, but I sure would like to give a pair a try for a few weeks.

Open baffle seems like a terrific idea. Unfortunately there's unusually a wall behind them.

 The reality is most speakers are just wooden boxes with drivers in them. It has been that way for decades but the public have been duped. 

Well, kenjit: here are some that have not been duped.

Do not listen to folks who claim open baffles are better than box speakers.  Its just sour grapes

This is silly. To each, their own:

Some enjoy the taste of sour grapes

Unless you listen to box vs. open baffle you can’t really comment.  I heard the Spatial Audio X4’s at the audio fest and thought they were wonderful and could easily live with them.  Oh yeah I have 20k box speakers.

I have built two sets for friends using Focal drivers at a time when they were still available. Both of them were coupled to sealed subwoofers. The baffles were a Corian sandwich with MDF in the middle. They were two way with a very straight forward 12 dB/oct crossover. The baffles were hung from the ceiling using decorative chains and the subs were just underneath. They were in essence open baffle LS3 5As. They sound much larger than they are. The owners are very happy with the results. 

Building an open baffle system is much easier than trying to build a non resonant box and the open midbass/midrange driver makes the speaker sound three times as large as it really is. Open baffle subwoofers is a patently silly proposition. I have tried it and the results are poor.  

@goose  You sir, make a good point, and have credibility.

@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. 

OP.

As I sit here listening to my recently acquired Spatial M3TM's. I will tell you that they are different. I can see where they might be a completely wrong choice for some. In my space, with my rig they are magic! I will comment on two major impressions, in my space.

First thing I noticed was what I perceived as a lack of bass. What Ive come to realize is I am hearing a whole different kind of bass. Or maybe I should say now I am actually hearing all of the bass and not the box. The speed and definition in the bass is really satisfying to me.

Second thing I noticed was the absence of the room. They really do blend into a room much better than box speakers do. The boomy bass is gone that classic hole in the 80hz zone doesn't exist anymore... 

Running them with Innuos zen mini and power supply, Pontus II, Aric Audio pre amp and Aric Audio super KT88/150 amp, all helix design diy cabling. Have had monitor audio silver 500's, Cornwall IV's and Focal 948's.

Ill stay with Spatial at this point!

Not sure if there was any value there but would strongly encourage you to try and experience OB's if you have interest. I find them simply amazing for the investment.

J.F.

Hi Erik, I would think that you have the experience to do this well. I’ve built a few and they can be very enjoyable.

In general, for bass, the larger woofers work better... I used a 15 at one time and 2 12’s once and 2 10’s another....

Try to keep your QTS between .5 and .8, My experience says look for a .6 and keep it under .8 if you can. VAS and XMax matters. It all depends on the room, stay mindful of response curves, remember that you are now firing from the rear also and room boundaries come into play more easily. If you use a mid, still look at QTS. It is less critical as you move up in frequency, but I would still try to find .5 to .6 QTS.

If you get them built, pull them out in the room listen and slowly move them back toward the walls little by little until you find the boundry reinforcement that fits your taste. Initially, you may find that you don’t have much taste. If you like, don’t hesitate to add another woofer, even a 15, air movement is the key to get bass moving, but stay aware of your room and boundaries that you may have to deal with. I have no doubt that you can pull this off. Use your experience and your ears, you’ll be fine.

Best sound I’ve ever heard, bar none, was the Nola Concert Grand four-tower speakers powered by top ARC electronics and a front end I can’t remember at a NYC audio show. This told me two things — an open-baffle, dynamic driver design is extremely intriguing, and a line array is just superior at conveying the scale and effortless sheer dynamics of a live performance.  Genesis and Pipedreams line arrays impacted me similarly, and I’m forever wrecked until I have a room and budget that can get me there.  Ugh. 

i tried a set of clayton’s m3 sapphires, i felt the open baffle design is a real winner, providing great sense of space and realism in the bass - very very impressive in that regard

as much as i wanted to love them, keep them, i could not get accustomed to their rather forward treble (despite much much effort expended to ameliorate) and relatively recessed midrange, but those issues are ones of tonal balance, related to driver selection/mating, and not related to the wonderful open baffle nature of the design

i think many other users have had really great results using good tube amps with spatials (which i did not want to do in this case for my own reasons)

Kenjit burped: "Do not listen to folks who claim open baffles are better than box speakers. They probably cant afford state of the art box speakers which can cost hundreds of thousands of dollars."

Don’t forget rule #1, never listen to kenjit for anything.

I have heard many, many speakers in my lifetime and the S2 open baffle speakers below are among the top.

BTW, I recently heard Spatial Audio speakers for the first time with Linear Tube Audio electronics at the NYC show and thought they were one of the top 3 I heard at the show.  Very impressed. 

I have the Linkwitz Orion 3.3, the Emerald Physics CS2.3, and the Magnestand maggie 1.6 - all dipole open baffle speakers.

The Orions and Emerald Physics - sound a lot like Maggies on steroids - they have the open sound stage of Maggies, but with better bass and dynamics.  The Magnestand Maggies improve the bass and dynamics of the typical Maggies and are more efficient.  They all sound superb in most respects.  I think I prefer the Orions, but its close.

@kenjit Your posts remind me of the political climate in the country rignt now.   While I fully support your right to your opinion, you attempt to squash any opinion that doesn't agree with yours. I think if we made ou a moderator you would just delete anything tht doesn't agree with you. 

You do realize that if we all agreed on everything we wouldn't need a forum.

Jerry

I've long been attracted to Emerald Physics beautiful open baffle speakers but I've never heard them.  If a used pair shows up near me I'll go listen to them.

Jerry

@jaytor , get yourself a measurement microphone and have a look. Yes, you have bass but it is wildly inaccurate. Bass is very deceptive. People will swear they get great bass out of little loudspeakers. What they are getting is the illusion of great bass. Servos on subwoofer drivers seems to make a lot of sense. The problem is that they do not take into account the resonance and movement of the baffle or the cancelation effects of an open baffle. Play something with a really low note like an organ piece and put your hand on your baffle. That vibration you feel is distortion that the servos cannot account for. The other problem with servos is that the best large subwoofer drivers do not have a problem with distortion. Distortion only becomes an issue with smaller drivers trying to make sub bass. They have to move so far to do it that their suspensions become non linear.  To tell you the horrific truth most enclosed subwoofers are not much better. The best subwoofers are going to be balanced force designs with extraordinarily stiff enclosures. The Magico Q series is a good example. Kef Blades use a balanced force design. You should be able to put your hand on a subwoofer while playing and feel absolutely no vibration.  

#carlsbad.  I too was intrigued be the EP features [no box to distort sound]. So at a show I heard them set up in a hotel room.  Hmmm.  Maybe they were not set up properly, but I was not impressed at all.  The sound coming out of the front was OK at best.  Moving around to the back was worse.

I'm really not sure that traditional measurements work well with open baffle designs.  I've never seen anyone claim a tiny OB performs great in the bass.

@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. 

I’ll pile on for GR Research.  I’ve had the NX Oticas and the dual 12” servo subs for about a year and couldn’t be happier.  Incredible soundstage width, depth and height.

Another advantage of OB is efficiency, which allows you to use low wattage tube amps.

But I do have mine about 5’ from the front wall.

 I used to have a full Gryphon system-still have all the cables-and I’d have to say it was mainly better in certain ways, not better overall.

I’ve heard the spatial speakers last Axpona, I think they were not matching the gear they used. They did not sound right. Too bright for my taste. One of the member here got rid of his Tekton Speakers and bought the spatial.I believe they are good speakers because (Sbank) Spencer have them and think they are better than his Tekton.

I often think that at the shows, what we think is "overly bright" is in fact "overly loud" for the room/treatments...and compared to how we will position and listen at home.

@jayctoy I also heard their speakers at AXPONA 2022 and they also sounded off to me. They were using LTA electronics so I'm unsure of what the problem was. Another speaker company I was interested in was Pure Audio Project. Has anyone heard these?

My open-baffle experience (after building many ’box’ speakers) goes like this...

I was enjoying my truck stereo one Spring day, and warming weather allowed me to roll the driver & passenger window down. What just happened!?... suddenly, despite the additional wind and road noise - the system suddenly sounded amazingly better. I’ve been missing something - but what? I also have a curiosity for unique speaker designs. My first speaker build (in high-school) was my attempt to recreate Ohm/Walsh omni-directional design (early 80’s) with drivers from Radio Shack that I put on my Christmas list (along with a jigsaw - which I used to build the speakers in my bedroom) - townhome living with no garage. As an adult, armed with new-found open-back curiosity, I found Martin Logan e-stats. I liked the sound, but despite the panel curvature, they have an unacceptably narrow sweet-spot. Digging further, I found Linkwitz. Not convinced, I ordered the inexpensive Madisound kit including flat-pack to test the waters.

Also note another influence. I saw the writing on the wall decades ago... due to technical innovation, audio systems (like everything else) will become more consolidated, condensed, smaller, all-inclusive, ’lifestyle’. Also, cable believers and nay-sayers alike can agree on one thing... the fewer cables the better (especially analog).

So with Linkwitz LXmini, there is potential for these two factors to coincide. I built the LXmini, and was rewarded mightily, inexpensive, beautiful, natural, enveloping sound. This is compared to the other speakers in the stable at that time (ML estats, ML motion-series, GoldenEar Triton, Tekton DI-upgrad, B&W, Elac, SVS Ultra, Buchardt). Only problem was the ported sub I had did not keep up with the LXmini’s... they need an open-baffle sub to match their accuracy. Back to the genius Linkwitz for a solution in the Phoenix[alt] sub. I built a pair with the recommended Peerless XLS drivers and could not be happier with the result. So, how does this coincide with ’lifestyle’?

My current normal listening rig consists of Node N130, a pair of Hypex FA123 (each mounted into the Phoenix[alt] OB-subs powering everything) and LXmini speakers. This is a ’lifestyle’ system - just one piece of gear and it’s half the size of a ream of paper. Cables are minimized down to one digital coax to Hypex FA-123(master), and one digital coax cable going from the master to the other Hypex FA-123(slave) - two cables total, and they are carrying digital signals (not analog).

What do I think of the Hypex FA-series + LXmini + Phoenix[alt] combo? It sounds like being on the stage listening to a performance first-person, as opposed to sitting in the audience listening through mic/mixer/amp/speakers. Rather than bore wax-poetic, let’s review the truths about this and potentially similar systems:

• These are the least room-dependent speakers I’ve ever heard. Why? Because they have omni-directional midbass and cardioid mid/treble, so there is very little side dispersion to reflect off walls/ceiling/floor.
• These speakers are no further in the room than any other speaker would need to be to sound good - mine are 30" from the front wall.
• Open-baffle bass doesn’t pressurize the room, so your house doesn’t become a giant vibrating box. Also, someone said, "Magico and KEF... balanced-force...". Take a look at Linkwitz Phoenix OB-sub design to see a simple example of cancelling cone inertia - there is no cabinet vibration in this configuration.
• No analog cables (caveat here, I do use balanced XLRs with NAD C658, when using that as source/pre). Node doesn’t have phono input or the suite of HDMI In/Out that the C658 has with MDCmodule.
• And finally, the #1 best reason for a system like this. The sound is fully controllable, at-will, on the fly, while listening/measuring - because it uses DSP crossovers and filtering within the Hypex FA-series DSP/amps. Let’s say you suddenly think the highs are too bright - adjust the filters (2minutes = done). Or, you want more bass (2minutes = done). Maybe you want a different adjustment for night-time or party-time listening, dial it in as you wish and save it as a preset (2minutes = done). Try doing that with most mega-buck monkey coffins. With these, you have the freedom to make them sound however you want, whenever you want. This benefit alone is worth the cost of admission, and why I can’t imagine making another speaker system without this capability. Note, Hypex FA-series amps are not the only way, as I started with the miniDSP2x4HD, to the nanoDIGI 2x8 (and 4 stand-alone Topping DACs), 4x10HD, DDRC-88A/BM (its been a journey of passion) - they all worked very well, but the FA-123 (also have new pair of FA-251 sitting idle) is the most ’lifestyle’ solution.

So, there you have it @erik_squires go out and get some open-baffle goodness. And I’ll leave you with this

And for those that doubt the bass...

How does this sound to you guys?

Then compare same track on 3x more expensive Voxativ.

Spatial Audio sounds better to me - which is surprising since I'm not a fan of horns, and tend to ignore all but the most botique giant horn models. What did you use to record that? Recordings sound great!

@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).

What kenjit overlooks is that drivers and crossovers can be selected and tailored for their specific application.  What may sound good in one configuration may not in another.  Expensive boxes with exotic hardwoods or automotive finishes may not contribute to the sound as much as they would the WAF and eye appear.  

What kenjit overlooks is that drivers and crossovers can be selected and tailored for their specific application. 

That is not true. Open baffle designs are WRONG. They emit sound that is out of phase out the back end. If you can show me an open baffle design that can emit sound IN PHASE not OUT OF PHASE from the back end then I will happily throw my box speakers away and we can all enjoy perfect sound with no cabinet resonances. I dare you

I ran various Alon/Nola speakers for well over ten years, went to box speakers, could never not hear the box contribution to sound, big mistake. Now into horns, 99.999% certain I'll never have another box speaker. I've heard Spatials lately, reminded me of my Alons, my horns have yet another distinct set of sound qualities.

My experience with such speakers is limited.  I remember hearing the Spatial speakers at a show but can't quite remember the sound.

But my general experience with dipoles (including my Quad ESL 63 with a dipole Gradient subwoofer), is that the sound was at first intoxicating "wow, it's so free of box coloration! I'm seeing right in to the recording."

The problem was that they didn't excite the room the same way. There was much less "feel" of the music - lacking the sense of instruments really being there, pushing air in the room.  So it was a bit more of an audiophile-intellectual experience.   I found going back to well designed box/forward radiators to be generally much more satisfying.  Of course it's all about compromises..

@mwatsme The recordings were made by Audiogon member @shkong78 at the Pacific Audio Show. I don't know what he used to make them.  To me the Spatials sound very good and are at the very least competitive with the Voxativs.

@jaytor Wave-guides, yes that makes more sense, open-back - nice!

One of the things that has prevented me from pursuing large front baffle designes (like Spatial, Pure Audio Project, Caintuk, etc.) is one of the same problems I hear with box speakers - reflections from the front baffle allow localization of the speaker, they don't 'disappear' so they sound like listening to speakers - ruining the 'being there' effect. Maybe a wave-guide solves this? Problm with wave-guides is they act to compress - same as horns can seem 'shouty' and broadcast forward. Maybe the AMT being open on the backside solves this? Most box speakers take these issues and add cabinet resonances, backwaves, (typically) flat side-panels and so on, stacking too many bad cards in your hand to form a winning combination unless a ton of $ is thrown at it. I once had a pair of egg'ish-shaped speakers made of concrete (no cabinet resonance), they sounded very good... until the Carver monoblocks blew a chunk off the inside in short order - returned those rattly beasts for a pair of bipole Mission spreakers that served me well for decades.

Cool thing about LXmini + OB-subs is they're inexpensive, you get to build them yourself (sense of accomplishment), they barely care about the room or treatments, you can use them to build an entire 'lifestyle' system for $2k (less than many of these guys are paying for a pair of cables), and tune them to sound however you like and whenever you like. What can be done to change the sound of most speakers... an endless game of cable-swapping, gear matching, tube-rolling, room treatments, vibration oscillators all around the room, copper screws, magic beads... the list may be infinite and infinite $.

One of the things that has prevented me from pursuing large front baffle designes (like Spatial, Pure Audio Project, Caintuk, etc.) is one of the same problems I hear with box speakers - reflections from the front baffle allow localization of the speaker, they don't 'disappear' so they sound like listening to speakers - ruining the 'being there' effect

Honestly I do not understand this problem. I get edge diffraction, but my speakers have 1/2" rounds on the edges and I defy anyone to tell me they can hear where the speaker is.  I've heard many other speakers that do a great job of disappearing as well, some with very narrow (Vandersteen) and some with broad baffles (SF Amati Heritage).  I've never felt this was an attribute of baffles which could not be dealt with.

@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. 

The PAP Quintet s in my 16x26x 12 room, 7.7 ft off front wall, create a complete disappearing act, profoundly deep imaging and hit me with sound hard enough from a 20 w amp that I feel no need to reproduce the memorex commercial of years past. Huge effortless wall of sound. Invited guests are constantly thrilled no matter how poor the recording quality as that 3-D wall of sound just takes over. 
im partial to bi-poles, dipoles,  however, having owned Quad 57’s until recently, Mirage M1’s. Only experience  boxes were the Ref 3A GV’s. With the PAPs, the quality of the bass is something I’ve never experienced in the prior designs. With these, Midas and highs can be tailored with the use of different widebanders. XO is easily accessible, can be tailored, upgraded with a screwdriver. I also have joined the permanent “no box” camp. 
GR- research may be next on the list. 

how does the sound of OB differ from IB? if i mounted speakers in a wall separating one room from another room with no direct communication between the adjoining rooms [no windows], would infinite baffle sound the same as open baffle? or is it the rear-wave "bounce" that is key to OB sound?