Exploring "compact" Otica variants... feedback requested!

0 Members and 1 Guest are viewing this topic. Read 7465 times.

paolocaminiti

  • Jr. Member
  • Posts: 63
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #80 on: 26 Feb 2023, 11:36 am »
In large rooms they're even more limited in output, which is where an H-frame or a triple 8" sub will be better suited.

My understanding is the upcoming model uses 3 servo woofers to compensate the loss of surface compared to the double 12...

It would be nice to understand if 30hz comes as a supposed optimum but one has the flexibility to experiment with lower extension or if it's a hard limitation due to the load of the U shaped baffle or amps/drivers...

I've been putting everything on hold waiting for this model to happen and be my possibly end game speaker that's why I'm asking in such detail - not easy at times because, no matter how much I love my spatial m3 turbo S, I can't bare its budget compression tweeters for much longer; the other week I almost pulled the trigger on a pair of Qualio semi openbaffle... those look great but ported woofers scare me now :)

Tyson

  • Full Member
  • Posts: 10725
  • Audio - It's all a big fake.
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #81 on: 26 Feb 2023, 03:47 pm »
If you can get a speaker to do OB bass down to 30 hz, then a box sub tucked away in a corner only doing 16hz to 30hz is actually a good solution. 

My suspicion is that Danny under-rates his drivers a bit because he doesn't know how big the room is that it will play in.  For example, my NX-Oticas are rated down to 70hz but I get extension down to 30hz in my smalllish room.  I actually have to remove some of the bottom end on them in order to get the subs blended in where i want them.  I also had to shift the sub's crossover points from 50hz to 40hz.  And these speakers play LOUD. 

So the upcoming single tower Otica plus a sealed sub in the corner might give you the best performance and the best aesthetics. 

If not, then the ripole plus NX-Studio looks like a winner to me.

Early B.

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #82 on: 26 Feb 2023, 04:01 pm »
My understanding is the upcoming model uses 3 servo woofers to compensate the loss of surface compared to the double 12...

My friend has the triple 8 OB servo subs and when I had a pair dual servo subs, there was no comparison -- the duals provide significantly deeper bass and better performance. Triple 8's are fine for smaller rooms, but for great bass, your starting point should be 12" woofers, and more than one of them.
   

dayneger

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #83 on: 26 Feb 2023, 05:35 pm »
Makes sense to me. I think it's fair to state that this thread assumes 2x 12" servo drivers per side as the starting point.

If not, then the ripole plus NX-Studio looks like a winner to me.

I'm curious what you feel would tip the balance for the Studio over the Otica MTM to have on top of the servo sub section?

I'm a little concerned that the sealed midwoofer on the Studio wouldn't give quite the same feeling for the body resonance of a bass or lower cello registers?

At the same time, perhaps they would sound better at times when I have to shove the speakers too close to the rear wall. I even briefly wondered whether a plank with bolts or other mechanism to "seal up" the sub section would make the speaker more flexible?
« Last Edit: 26 Feb 2023, 08:40 pm by dayneger »

Early B.

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #84 on: 26 Feb 2023, 08:37 pm »
I'm curious what you feel would tip the balance for the Studio over the Otica MTM to have on top of the servo sub section?

I'm a little concerned that the sealed midwoofer on the Studio wouldn't give quite the same feeling for the body resonance of the a bass or lower cello registers?

I'm not Tyson, but since I've asked myself this question, I figure I'd give you my answer FWIW. For background, I previously had a pair of OB monitors (not GR Research, but Danny designed the crossover) on top of dual OB servo subs. Sounded great and I had no issues with it, but the insatiable audiophile always wants more. One of the drawbacks of OB is a Miss Manners midrange (ummm..., polite). That's OK for some types of music and perfect if that's what you prefer, but when you want to rock out (and dayneger seems like a dude who rocks out when his wife isn't around :o), you want a big-bellied midsection that only a box speaker can deliver. This is the reason I built my own speakers with 12" sealed midwoofers. Plus, as Tyson mentioned earlier, the NX Studio goes down deeper and should be easier to integrate than the Otica MTM.
     

     

Tyson

  • Full Member
  • Posts: 10725
  • Audio - It's all a big fake.
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #85 on: 26 Feb 2023, 08:54 pm »
Makes sense to me. I think it's fair to state that this thread assumes 2x 12" servo drivers per side as the starting point.

I'm curious what you feel would tip the balance for the Studio over the Otica MTM to have on top of the servo sub section?

I'm a little concerned that the sealed midwoofer on the Studio wouldn't give quite the same feeling for the body resonance of a bass or lower cello registers?

At the same time, perhaps they would sound better at times when I have to shove the speakers too close to the rear wall. I even briefly wondered whether a plank with bolts or other mechanism to "seal up" the sub section would make the speaker more flexible?

Mostly for me it's about getting the best upper bass and lower midrange.  If you were going to use a regular H-Frame setup with the bass woofers pointed at you, then I think the MTM fully OB would be fine because the upper bass of the big 12" woofers would be able to 'meet' the lower range of the MTM and it would sound great.

But, going to a ripole will effectively limit how high the bass from the 12" woofers can reach up and still sound good.  In that case, it's better to go with the NX-Studio, which goes down to 70hz and has very nice lower midrange and upper bass, making integration with a ripole sub a snap. 

I've heard a bunch of OB speakers and a bunch of box speakers.  The NX-Studio doesn't sound like a box speaker, it sounds like an OB speaker.  I don't know how Danny performed that bit of magic but it's the only bookshelf speaker I've heard that I could live with.  It's pretty incredible. 

paolocaminiti

  • Jr. Member
  • Posts: 63
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #86 on: 26 Feb 2023, 09:49 pm »
My suspicion is that Danny under-rates his drivers a bit because he doesn't know how big the room is that it will play in.  For example, my NX-Oticas are rated down to 70hz but I get extension down to 30hz in my smalllish room.  I actually have to remove some of the bottom end on them in order to get the subs blended in where i want them.  I also had to shift the sub's crossover points from 50hz to 40hz.  And these speakers play LOUD. 

Living in London my space is pretty small... interesting to hear the regular ottica are so extended, I could possibly live just with them right now and then eventually add one sub or two subs the day I find my self in a larger space...

Still it would be interesting to hear from Danny if this 30hz is gonna be and hard limit imposed by the speaker/electronics or it's just what the optimal performance should be...

paolocaminiti

  • Jr. Member
  • Posts: 63
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #87 on: 26 Feb 2023, 09:53 pm »
I'm curious what you feel would tip the balance for the Studio over the Otica MTM to have on top of the servo sub section?

From what I remember reading about the MTM which I almost bought before they were discontinued some people where never happy about the low midrange weight compared to the regular ottica, they tried to get it there but there was always something missing compared to the bigger ones... and the looks, but personally I liked the look - only thing a bit weired to me was the MTM baffle stretching a bit longer behind the rear of the sub cabinet.

Entirely out of speculation I think a one package ottica could be a very good candidate for a ready made offer as we see some are being supported now like the studio - which would be a great thing for people with less time to spend on construction.

Hobbsmeerkat

  • Industry Participant
  • Posts: 2411
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #88 on: 26 Feb 2023, 09:59 pm »
Living in London my space is pretty small... interesting to hear the regular ottica are so extended, I could possibly live just with them right now and then eventually add one sub or two subs the day I find my self in a larger space...

Still it would be interesting to hear from Danny if this 30hz is gonna be and hard limit imposed by the speaker/electronics or it's just what the optimal performance should be...

I believe Danny mentioned that he plans to have the very bottom rolled off via the amp to prevent over excursion.

My dual 8s can definitely bottom out when driven hard and deep bass, and the new tower will be designed to prevent that.
The 30hz "limit" on my subs is simply a product of their design & room size/shape, where they benefit from boundary reinforcement in small or narrow rooms.

dayneger

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #89 on: 27 Feb 2023, 06:54 am »
One of the drawbacks of OB is a Miss Manners midrange (ummm..., polite). That's OK for some types of music and perfect if that's what you prefer, but when you want to rock out (and dayneger seems like a dude who rocks out when his wife isn't around :o), you want a big-bellied midsection that only a box speaker can deliver.

I've heard lots impressions of non-servo OB bass being insufficiently compelling, but I'm not sure I've heard many descriptions of a "Miss Manners" midrange.  Do others have this take on it as well?  Audio can be confusing with so many preferences out there.  Unfortunately, I haven't heard enough different systems to have an informed enough opinion.  I'm not discounting your description in the slightest since your description of big-bellied midsection absolutely resonates... why do OB systems fall behind here?

In any case, yes, I've definitely been known to crank it up a bit from time to time.  Impromptu dance parties are also not unknown.  8)  When critically listening I might bounce around from a cello concerto to hip hop to female singer songwriter to whatever in sequential tracks.

Mostly for me it's about getting the best upper bass and lower midrange.  If you were going to use a regular H-Frame setup with the bass woofers pointed at you, then I think the MTM fully OB would be fine because the upper bass of the big 12" woofers would be able to 'meet' the lower range of the MTM and it would sound great.

But, going to a ripole will effectively limit how high the bass from the 12" woofers can reach up and still sound good.  In that case, it's better to go with the NX-Studio, which goes down to 70hz and has very nice lower midrange and upper bass, making integration with a ripole sub a snap.

That's a very helpful description!  If the ripole layout would struggle above 120-150 Hz then it makes total sense that the Studio would blend more easily than the MTM.  If the Studio semi-defies physics in terms of sounding significantly OB through the midbass and midrange, then it really could work nicely as a speaker system. 

It would be pretty interesting to measure this with a test rig.  How high could the 12" in a servo ripole layout go to meet anything else on top?

It would also be fun to see what happens when there's a middle ground, say a parallel driver setup like the H-frame but with some degree of reduction of the frontal open area in order to help it blend better with the width of an MTM/Studio baffle.  I'll go ahead and say it... a 16x14x30" brick is not only suboptimal for a lot of interested customer, it's also quite non-obvious that these 90 degree flat panels are optimized for acoustic results.  To be honest, it would be a total accident in favor of flat panel logistical efficiency and simple DIY convenience if that were the case.  Highly tuned engineering is rarely so convenient to either of those fully legitimate concerns.

Exploring the H-frame a bit, it at present each driver zone has an internal width of 13" and an average height (front-facing 13", back-facing 12.25") of 12.625", so call it 164 sq in of area.  The actual driver Sd is 76 sq in according to the GR site, so we have 216% of Sd open.  If you applied the recommended norez to the (questionably) flat panels you effectively chop 2" of air space off of both directions.  This reduces the open area to 113 sq in, or 148% of Sd. 

Is that 50% premium (or 116% sans norez) helpful, or could it be better utilized for resonance avoidance and/or pure aesthetics?

If you leave the back side to that 150ish percent to hold a variable constant, what happens as you sequentially reduce the frontal open area to 125%, 100%, to 80%, to 60%, to 40%?  What if you did so in a fashion that also had walls of variable thicknesses and possibly different materials?  This is another way of asking what would happen if the we actually optimized the environment, then stepped back to see how close we could get with more accessible mechanisms like flat panels of MDF?

I'd love to also do this set of experiments with a number of servo ripole rigs.  If only I had the time and $$ to do so!  I could support the CAD development, though... that might be the easiest part. Hence my thread here.  :oops:

P.S.  Where does an H-frame "meet" the MTM in terms of XO frequencies right now?

dayneger

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #90 on: 27 Feb 2023, 11:14 pm »
Here's a H-frame with tapered front geometry.  As a thought experiment, with a couple of small removable pieces for the undercuts, this could in theory be cast as a single piece of counter concrete or whatever.  Just don't try to carry them upstairs yourself.  :wink:

A bit late I noticed that I'd accidentally set the driver further back than intended, and it might be a bit deeper front to back than necessary.  The max width in this particular study is 16".  I wasn't able to "win" much vertical height, so even with the MTM section spliced down pretty hard it's 47" tall.  The sub section is 28" tall, which could be reduced maybe an inch.

For reference, the front sub openings taper to 60 sq in, or 79% of the 76 sq in piston area of the driver.  The back openings are each 135 sq in, or 178% of the Sd.

This is by no means a fully optimized design!  I was just just trying to visualize some of my overly wordy explanations in the prior post.

















corndog71

  • Full Member
  • Posts: 1644
  • Some people call me Rob.
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #91 on: 28 Feb 2023, 01:14 am »
For the record, my dual subs alone weigh 88 pounds each.  And there’s already a lot of pressure on the h-frame walls in this configuration.


Early B.

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #92 on: 28 Feb 2023, 01:31 am »
For the record, my dual subs alone weigh 88 pounds each.  And there’s already a lot of pressure on the h-frame walls in this configuration.

Yep. If I had to do it all over again, I'd make the outer walls of my dual subs 1.5" thick. This would probably increase the weight to about 100 lbs.

dayneger

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #93 on: 28 Feb 2023, 05:23 am »
The current H-frame design does spec 1.5" walls... 2x 3/4" of MDF.  It's no surprise that a high-performing set of speakers will have some heft.  I've read that the higher end of the spectrum requires piano movers or their equivalent, to horse around 400-800 lb speakers.   :o

Ok, so if we chop off the top and just look at the sub section for comparison, it could look like this (with a few radii):

Front quarter without perspective



rear quarter with perspective



If these were concrete, the shell would be around 210 lbs plus drivers.  Without the exotic 3" rounds and the bottom draft, 230 lbs plus GR12s.  With the geometry, the variable wall thickness, and the sheer mass I'd guess you could kiss the norez goodbye.  Concrete in these dimensions is unlikely to sing along to 50 plus/minus 35 hz.

If these were produced with, say, reaction injection molding using dense foamed polyurethane that would drop by more than half.  Not really viable for producing 2 of them, however.  :?

Either way, I'd be expecting to put these on heavy capacity rollers for easy repositioning, so at a certain point it doesn't need to matter that much.

I'm not yet sold on this "frontal, mildly SLOB" approach for my particular situation (still noodling over Studio vs MTM and ripole vs frontal sub variations).  However, if I were considering standard H-frames I'd absolutely break up the side panels with radiused parts for the corners and then pour some non-resonant mixture of sand and epoxy (or better) into those radii pockets to deaden the structure.  Talented CNC folk that support GR could easily create an "advanced" H-frame kit with more sophisticated flatpack parts... after someone more skilled than I supported their creation, of course.  :)



« Last Edit: 28 Feb 2023, 02:01 pm by dayneger »

Early B.

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #94 on: 28 Feb 2023, 05:41 pm »
I like the direction you're proposing for the dual sub redesign. I'd love to replace my sub cabinets with something more appealing look than the standard box.  I realize the cost would be crazy, though.

corndog71

  • Full Member
  • Posts: 1644
  • Some people call me Rob.
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #95 on: 28 Feb 2023, 06:39 pm »
I don’t think concrete is immune to resonance.  If it were that easy, it would be more prevalent.

dayneger

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #96 on: 1 Mar 2023, 05:29 am »
I like the direction you're proposing for the dual sub redesign. I'd love to replace my sub cabinets with something more appealing look than the standard box.  I realize the cost would be crazy, though.

Thanks!  Glad the general idea resonated.  Or didn't.   :D

The cost doesn't necessarily need to be crazy.  In fact, with some thought, things could be streamlined pretty well. It does also depend on what finish you're gunning for.  Seamless high-grade wood grain usually makes it tougher.  Being able to combine materials and fill in gaps and then paint tends to make things easier.  Trying to fit unhelpful geometry from prior efforts may make things harder.

So, let's imagine that you'd like to have something similar to the "sub only" image above, but perhaps without the corner rounds, and a flat top for placing other elements on.

I haven't fully thought this through and there are many possible variants, but for example you could make a simple shell, drop it into a mold with plugs, fill up the shell, and make it pretty.  It might not be so bad.

A quick, imperfect take on it:

- cut or procure a CNCed front baffle probably 1.5" thick that includes side notches and the radiuses for the lead-in geometry of the woofer front exits, cut mostly but not all the way through
- cut or CNC some external framing structure that forms the basis of an alignment mold/jig to hold pressure, plus a few 2x4s and sheets of 4 mm ply (baltic birch, marine/meranti ply, whatever) for the sides.
- build the alignment mold/jig out of the above
- cut or CNC the end caps (top and bottom) of the subwoofer
- glue the end caps to the baffle
- add 3D-printed caster inserts to the base end cap if desired
- tricky part--create the port plugs made out of a first section in front of each driver, and a second section after each driver.  The walls need to be smooth and have a draft angle, guessing 3-4 degrees minimum.  If undercuts are needed the plug cores must be hollow to allow internal access to one or more bolts that hold the separate "undercut" sections so that they can be released before removing the plugs.
- wax the sides and baffle side of the port plugs and then screw them to the front baffle
- tack and glue a 2-4 mm sheet of baltic birch or similar thin substrate for the sides to the notches in the front baffle and the end caps (forming a complete outer shell)
- while the sides are being tacked on and glued, a second person is mixing up the "cement"--polymerized counter cement or one of those exotic epoxy mixtures of many particle sizes I recall home CNC-types exploring for their machine beds
- immediately set the shell down into the alignment mold/jig and secure to the jig
- add additional layers of ply if more layers are desired for whatever reason (e.g. larger outer radii), tacking them into place with glue to the outermost layer.  Or it might be possible to have achieved this thicker outer skin before the wet pour starts.
- fill/pour the mold with chosen cement or epoxy mixture
- fill the back of the shell with the cement/filler mixture until about 1/2" below the "back depth" line
- attach one of those thumper/vibrator thingies to get the air cavities out of the poured mixture
- cover and let start to set.  Apparently concrete likes to set slowly.  If it's epoxy-based, make sure it doesn't get too hot and burn your garage down. ;)
- at the appropriate time interval (TBD), pour the final 1/2" or so of depth using a self-leveling cement to make getting a clean back easier.  The port plugs could have back radii plates that soften the rear airflow, so this would allow pouring right up to the tangent more easily in a second step.  Or you could drop in a wooden back.
- release the attachment bolds and undercut pieces, then remove from the mold with the help of 2 or 3 or 4 of your strongest friends
- remove the plugs and then cut/fair in the front port openings
- grind off any other burrs than may have occurred, round off edges, fill in tiny voids with a filling primer, then paint in such a fashion that even nlitworld has serious sub envy

Since this approach maintains an all-wood exterior for at least the skin, you could go also choose a fancy wood for the external veneer and baffle.

Once such a "mold and plugs" combo is created, making the second and thirtieth sub is much easier.  You could make several subs for yourself and local friends, then send the slightly bulky but relatively light mold/plugs to the next eager OB bass devotee.  Or have several sets in circulation.

After the mold and plugs are created ($1-5k?), the raw materials for the each sub chassis could be in the $100-300 range.  Possibly less if the mold where for casting the whole thing in one shot.

With appropriate geometry and flexibility/complexity of the molding components, you could integrate an MTM on top as a seamless element.  But this post is way too long already.






WGH

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #97 on: 1 Mar 2023, 09:09 pm »
I was plowing through another unreadable review on 6moons about the Cen.Grand DSDAC 1.0 Deluxe DAC and saw this sub in the review photos, you might be interested in checking it out:

Sound/Kaos DSUB 15



DSUB 15 review
https://6moons.com/audioreview_articles/soundkaos10/




dayneger

Re: Exploring "compact" Otica variants... feedback requested!
« Reply #98 on: 1 Mar 2023, 11:14 pm »
Thanks for sharing!  I hadn't seen that one.  And agreed, hard to read, although there were some interesting observations scattered throughout that made it worthwhile.

I also liked seeing a few of the other ripole designs out there.  https://6moons.com/audioreview_articles/soundkaos10/6/

It would be interesting to do a comparison of these layouts... possibly keeping the frontal/rearward piston area compression/decompression ratios similar.  Say, 33% of driver piston area to the front, 150% to the back.

- ripole with some genre of trumpet or flare between the drivers and open space, like this DSUB 15 and some of my studies
- ripole with the forward edges of the woofers more or less directly interfacing with open space
- forward-facing SLOB, like the subwoofer study I just posted

Overall I still suspect that the servo system paired with velocity compression forward, velocity diffusion rearward, could be pretty sweet.
« Last Edit: 2 Mar 2023, 04:54 am by dayneger »

MarvinTheMartian

  • Jr. Member
  • Posts: 127
Re: Exploring "compact" Otica variants... feedback requested!
« Reply #99 on: 7 Mar 2023, 01:21 pm »
Servo ripole, be aware that both the 12” and 8” drivers have a vented pole pieces to assist voice coil cooling,
The hole on the back of the magnet requires at least 1” or 2” clearance for ventilation.
I ran across this same issue when trying to build ‘minimum depth’ sealed cabinets.
Shawn