[dayneger]

I somehow intuit that my next phase of audio experience should include at least some degree of dipoleness.  I don't have--and nor do I ever expect to have--a perfectly controlled room, plus descriptions of the OB musical portrayal are very appealing.  Holographic and natural music experience is my goal (whatever those terms mean to you ).

So, I've watched Danny's and Clayton/New Record Day's videos, read around about various projects and offerings, etc. and I'm frankly finding it hard to fully understand exactly which factors lead to which results across the frequency spectrum; which are unique to dipole implementations; and which combination could work best for my context.

Which attributes buy you which acoustic results?  Given limited space and budget, where to most smartly invest?

A few examples across the frequency range, without intending to imply that any approaches are inherently superior:

1.  Only >1200 Hz (at the minimum due to Neo3):  NX Studio.  Not positioned as an OB speaker per se, but claimed to have a fair amount of "OB goodness".  Closed bass/mid-bass, requires some kind of sub.

2.  Only mids:  Statement IIs, Travelers, etc. from Jim Holtz/Curt Campbell collaboration.  Also not positioned as OB, mid opens to back via a 6" tube, claimed to add air and soundstage depth.  Closed tweeter, ported bass depending on model.

3.  Only bass through lower mids, 32-575 Hz:  Spatial M3/5 Sapphires.  Fully OB-mounted 15" driver on flat baffle, closed sapphire tweeter covers 575 and up.  Considered OB.

4. Only bass 20-180/250 Hz is OB, rest is "non-boxy" closed speaker implementations (Gallo, modified KEF), as seen in Vic's entertainingly informative blog:  https://trans-fi.com/diy-speaker-blog. Holy dual 18's per side.   

5.  All frequencies OB, often with extra subs.  E.g., Danny's NX Otica's, Extremes

Some of these choices also have very specific implications (and costs) for driving electronics and amplification as well.   

My personal context--a target customer who a) can have drivers at least 3' into the not easily-acoustically-treatable 17' front wall x 20' side x 8' living room, at least for critical listening, b) needs to keep the visual "bulk" of the system way down, c) has a modest budget of maybe $2k (could be stretched some over time), and d) stupidly enough, really appreciates the impact of deep bass on wide-ranging music styles and low frequency spatial cues.

I do have solid woodworking skills and machinery, at least, and am fully unafraid of unconventional approaches.

Where would you start?  Which OB aspects do you feel matter the most and how much of the goodness can you get on limited investment and speaker bulk?

Thanks!  And sorry for the long post. 

[mlundy57]

Given your desire for extended bass, non-bulky visuals, and $2k budget, I'd suggest a pair of X-Statiks (OB midrange, sealed woofers and tweeter) with upgraded crossover components paired with a sealed servo sub kit 2. This will give you the open baffle goodness in the heart of the music and stupid good bass performance. The servo sub kit 2 is very fast and musical, plays flat to 20Hz, and is -3dB around 14Hz. I have one in my living room and you can feel the vibrations through the couch down to 10Hz. This combination will give you exceptional performance within your budget.

The full range (20Hz - 20kHz) open baffle speakers with the smallest footprint are the NX-Otica MTM monitor paired with the dual servo sub kit 4. However, depending on crossover upgrades and how you build and finish the cabinets, you're looking at 2 - 3 times your budget.

[HAL]

Since frequencies below 200Hz are the most problematic for room tuning, you might also consider making a pair of 2x12 H-Frame open baffle Servo Subs as they have a dipole radiation pattern.  They could be used with standard speakers to start and then with time, the main speakers upgraded to OB versions.

If you build the H-Frame cabinets, you are in the $2000.00 range for a pair. 

Most people do not realize how much having a very good low end adds to the musical experience.

Good luck with your quest.

[Tyson]

With less than perfect rooms, full OB is the way to go.  I’d do the OB servo subs and the NX-Otica MTM module.

[ric]

As a Spatial owner (M3TS) of course I'd recommend them. The advantages from my perspective are: easy to move around, no sub required (but certainly an option) easy to drive, huge soundstaging, great imaging and "live" sounding presence.
Someone here is selling the M4TS, depending where you live, for $1500. good luck!

[corndog71]

If you limit yourself to $2k then your best option is any of the X-series speaker kits and sub kit 2.  I highly recommend the X-Statiks.  With a sealed servo sub you will get big open sound and wall shaking bass.  Oh, and don’t forget no Rez and Sonicap upgrades.

[dayneger]

Thanks so much for the helpful contributions thus far!

Looking at bass first, OB seems to really shine in terms not being as sensitive to room coupling.  I keep reading comments to the effect of "there's nothing like the sound of OB bass" and "once you hear it, you can never go back."  I'm quite sure that'll be my response as well.

OB bass also seems to be generally bulky and expensive, while apparently usually still not delivering the same very low extension and volume capability as boxed subs.  Or at least it seems that a single sub kit 2 is very difficult for the OB sub kits to match.  -3 db at 14 Hz is pretty intense! 

Just trying to understand more here:

- How well would the sealed servo sub kit 2 blend with slightly higher Hz OB bass?  For example, I believe I read the NX-Oticas play down to about 80-90 Hz.  What does this sound like?  Do room problems ensue?  How much does the "servo" capability help bridge between regular boxed and OB subs?  For that matter, would the NX-Otica MTM module (still not on website ) pair well with a single sub kit 2, at least initially?

@Ric, thanks for the heads-up about the M4TS!  I'm in the SF Bay Area, so out of luck on that set.  I do appreciate the clean lines and low bulk path to low 30's OB bass!  Curious what servo'ed Rythmik 15s would sound like in that config, or maybe with the NX-Otica MTM spliced on top. 

[Tyson]

Don't even worry about a sealed sub until after you've heard the servo OB subs.  I run dual OB subs in my setup and they don't need any help from a sealed sub. 

Let's be clear, the subs used in Danny's designs are the same subs used in the top of the line ($27k) speakers from Spatial audio.  I've heard those Spatial speakers at RMAF a few years ago and the bass is insane.  Well worth nearly $30k for that level of performance.  But in this case, with Danny's design, you get that level of performance for a fraction of that because it's DIY. 

So there's a very good chance you won't need a sealed sub.  Especially if you don't have a huge space.  But the X3 and X5 are just going to be outclassed by the servo OB subs from Danny (and in the Spatial Luminas).  This is bass that is just fundamentally better than anything you've heard before.  I know that, because it's fundamentally better than any bass "I" heard before.  Game changing. 

Something like the X3 and X5 will get you good, punchy bass that sounds good.  The servo OB subs get you world class clarity, punch, depth as well as being able to punch you in the gut in a very visceral way.  It's not the fault of the X3 or X5, they are excellent designs, but they are simply outclassed by the Lumina and GR Research servo OB bass systems.

[corndog71]

If you’re on a budget the sub 2 kit is the way to go.  If not then yes, build the OB subs.

[dayneger]

Hmmm, some more very convincing (thumping? ) endorsements for going all in on the OB bass.

Darn you people!   

Well, just kidding, if I didn't want to know I shouldn't have asked.

So that leaves me pondering:

     1.  How to deal with the fact that a couple of servo OB subs (sub kit 4) plus materials would more than wipe out my original budget just getting to 100-200 Hz

     2.  What could be done to reduce the visual impact/impression of bulk.  I just simulated 16" wide x 14" deep pedestals and... they would be a tough sell (albeit not as bad as some photos appear!)

For #1 = budget, how much difference is there between sub kits 3 and 4 with the different amps? For a pair it's a relevant $380 difference.  Pushing on that, how much would I "lose" going with a single 12" servo OB driver per side, with the less expensive HX300 amp of kit 3 (basically sub kit 1)?  A single driver also might help with #2.

For #2 = visual footprint, do the sides/top/bottom of the H-frames provide an acoustic function other than the structure for rigidly holding the drivers in place?  As in, if I were able to rigidly hold them in space with a different structure that may have more WAF, would they sound the same?  I'm not sure yet which path I'd go, but to illustrate a few ideas for conversation's sake, mounting them to a 3/4" jet-cut steel baffle plate no wider (or barely wider) than the driver flanges, or pouring a figure 8 form in concrete--like 2 conjoined concrete tubes 11" inner, 12 outer, 3" deep.

Btw, f anyone happens to have the 12" driver dimensions (or a CAD file) that would be great--many of the .pdf links on the new GR site appear to be broken.

[mlundy57]

Hmmm, some more very convincing (thumping? ) endorsements for going all in on the OB bass.

Darn you people!   

Well, just kidding, if I didn't want to know I shouldn't have asked.

So that leaves me pondering:

     1.  How to deal with the fact that a couple of servo OB subs (sub kit 4) plus materials would more than wipe out my original budget just getting to 100-200 Hz

     2.  What could be done to reduce the visual impact/impression of bulk.  I just simulated 16" wide x 14" deep pedestals and... they would be a tough sell (albeit not as bad as some photos appear!)

For #1 = budget, how much difference is there between sub kits 3 and 4 with the different amps? For a pair it's a relevant $380 difference.  Pushing on that, how much would I "lose" going with a single 12" servo OB driver per side, with the less expensive HX300 amp of kit 3 (basically sub kit 1)?  A single driver also might help with #2.

For #2 = visual footprint, do the sides/top/bottom of the H-frames provide an acoustic function other than the structure for rigidly holding the drivers in place?  As in, if I were able to rigidly hold them in space with a different structure that may have more WAF, would they sound the same?  I'm not sure yet which path I'd go, but to illustrate a few ideas for conversation's sake, mounting them to a 3/4" jet-cut steel baffle plate no wider (or barely wider) than the driver flanges, or pouring a figure 8 form in concrete--like 2 conjoined concrete tubes 11" inner, 12 outer, 3" deep.

Btw, f anyone happens to have the 12" driver dimensions (or a CAD file) that would be great--many of the .pdf links on the new GR site appear to be broken.

I'll get back to your questions after work. For now, here are some pictures of my NX-Otica MTM/dual OB sub setup.

at Lone Star Aidio Fest 2019


In my 12' x 14' x 8' room at home



previous setup in my room at home








The equipment racks are at the back of the room on the side wall

[corndog71]

With kit 4 you get a more powerful amp which also comes with an EQ that could help in certain rooms. 

The enclosure is designed to separate the front wave from the rear wave.  Some guys have built u-shaped baffles but I believe Danny has said those may technically work but the rear wave puts a lot of pressure on the side baffles and could add resonance.  I think it's best to stay with Danny's design.

The link for the cabinet works for me.   https://www.gr-research.com/uploads/1/2/6/6/126601004/h-frame_2.pdf

I too considered a single driver per side but if I remember correctly someone who tried this said you lose a lot of output compared to the duals.  Multiple drivers just make it more efficient.  As a cheap bastard myself, I understand the desire to try to make these as cheap as possible.  Danny has already done as much as he can to make these affordable.  If you think these are expensive, (well, they are for us poor folk) then consider what they would cost as a fully finished speaker.  Basically $x5.  These are endgame subs.  The kit price makes them an absolute steal. 

I had someone else cut my cabinets.  Since I'm not a woodworker this was ideal for me.  All I had to do was glue them together and paint them.  If you can cut them yourself then that'll save a lot of money.
 

[dayneger]

@mlundy57, those are some beautiful-looking NX-Otica MTMs and subs!  Nice work.  I'm leaning toward white as the dominant tone, although I'm not yet sure by which method I'll get there.  I'd love to hear more of your thoughts when you get a chance.

@corndog71, thanks also for your comments.  No question a single driver will lose a fair bit of output... just trying to get a handle on how much.  I usually don't play my system that loud in absolute db, so could possibly get away with it.

Regarding the enclosure/speaker mounting, it's not clear to me how or why the separation of the front/rear waves works at these low frequencies/long wavelengths?  Curiously, most other products have no baffle width on their bass drivers (based on a non-exhaustive, informal image search). The interesting configuration I linked in my first post literally has the drivers suspended in free space.

Clearly I'm not a speaker designer!  However, a lot of things in the audio world look the way they do based purely based on production convenience and/or cost (e.g., flat sheets of wood and metal).  That's why I'm seeking to understand the degrees of freedom that are available rather than assuming them.

Finally, I'm not intending to imply in the slightest that Danny's designs aren't great value!  Heck, if I didn't believe they're high bang for the buck I certainly wouldn't be considering them.  The challenge is that those bucks show up in absolute and not relative terms.

[Early B.]

Finally, I'm not intending to imply in the slightest that Danny's designs aren't great value!  Heck, if I didn't believe they're high bang for the buck I certainly wouldn't be considering them.  The challenge is that those bucks show up in absolute and not relative terms.

Buy once, cry once. Don't settle for anything less. 

[Tyson]

If dual servo subs are absolutely out of the question, then another option would be to do a pair of NX-Studio monitors as your main speakers, then do a dual OB Servo sub sitting between the 2 speakers.  Since the NX-Studio Monitors go down to 70hz, you can get away with a single OB sub.  Total output for bass will be down a bit vs having dual OB subs as stands, but you still won't need a sealed sub to fill anything in.

This would still be an EXCELLENT system, FAR better than most setups in the world.  But it's not quite the "end game" system that dual OB subs and MTM NX-Ottica is.

[jn316]

I was in a similar position last year. Most people said get the H-frame dual servo subs now and save up for your top end of choice later. That is what I did. Since you mentioned that you really appreciate detailed, great sounding bass, I'd suggest going that route. Otherwise, you will always wonder how much better your bass could be. With them, you will have no desire to upgrade.

[jn316]

Just saw Tyson's post...very good advice there too. You could then have a complete system and save up for the second H-frame sub.

[dayneger]

Dual OB subs aren't completely out of the question, and the amount of enthusiasm for them is quite notable!  My financial goals may yet probably will crumble.

Understanding which aspects of the H-frame would be fair game to modify (design degrees of freedom that would be largely acoustically insignificant) would certainly be helpful in guiding my exploration into how I might make the OB bass section look lighter and more graceful to my wife and me, in our home context.  Aesthetics are of course very personal--not commenting about anyone else's system.

To get 4x 12" drivers well out into my living room that would likely mean removing visual mass, trimming unneeded air volumes, that kind of thing.  Do you really need side and top walls around the drivers?  If yes, could they be shorter than 14" deep (-->where did that number come from)?  If yes, could they be tubes (instead of rectangles), or a big slot shape, or something else?  Does the no-res serve a function other than dampening the flat panel surfaces?  That kind of thing.

D.

P.S.  About the site links, for example https://www.gr-research.com/store/p37/SW-12-08FR_Servo_Sub_Woofer.html, every one is broken, including the mechanical one I was looking for.

[Tyson]

I think with the H frames, if you do something to soften the top, they look a lot nicer.  Something like this:

[Hobbsmeerkat]

I have both a modified Rythmik L12 and a pair of Danny's dual 8" servo stands (tho no longer available) and they're two totally different beasts.

The L12 is an incredible sub, esp if you want absolute low end authority. It could easily shake my house apart if i let it. lol
Its also fast & articulate, however, like most sealed subs, is prone to boominess. But for under $600, i highly recommend it.



The 8" OB servo stands are a different story. They're a U frame with one 8" driver on each side. And a plate amp under one driver.
What these lack in authority, esp below 20hz, they make up for with incredible speed, texture and detail. They're best suited for medium fo small rooms. I've only ever heard them "boom" once, even when neither settings or placement were changed from the previous use.
Their biggest struggle is in large rooms. They need a little bit of room reinforcement to sound their best. They're currently being used with my XLS.



Tonally, the only bass I've heard that's better is Danny's personal pair of triple 12" H-Frame Subs, which are the best of both worlds. Absolute authority, speed and detail esp in large rooms. Their only "downside" is their size. But that can be made up for by getting dual servos and putting the speakers on top, as others have shown above.