[dayneger]

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

Oh! 

So, these little holes need some breathing room?  That stinks. 


 


Thank you so much for taking the time to share this super important piece of information, Shawn!
 

[Rikard Ekval]

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

This Ripole design does vent the magnet.
Quite compact. NX Studios or Nx Oticas on top.👍


 

[Danny Richie]

This Ripole design does vent the magnet.
Quite compact. NX Studios or Nx Oticas on top.👍


 

Careful, those can become buzz boxes.

[dayneger]

This Ripole design does vent the magnet.
Quite compact. NX Studios or Nx Oticas on top.👍

I'm pretty sure I read that there's a bit of sealing material between the housing and the magnet.  It doesn't appear that this driver vents out the back?  I think it was mostly trying to keep the enclosure as small as possible... and they're indeed quite compact.

Studios on top would undoubtedly sound pretty sweet!  That said, non-servo OB bass designs unfortunately don't seem to hit 20 hz very well.

[Danny Richie]

They are going to act like a woofer in way too small of a box with a high tuned port. It will cause a hump in the response and tend to cause a lot of box buzzing.

[77SunsetStrip]

There is a documented caution about 250Hz or so causing resonance.  Low pass filter 80Hz or below eliminates that problem.  My Ripole enclosure is rock solid down to 30Hz.  No punch in the gut impact, but will rattle pictures on the wall cranked up.  Clean and articulate deep bass much better than previous sealed box.  Open baffle servo sub could be better, but a Ripole is great for smallish listening room.

[ebag4]

I can't speak to Ripoles, but I would caution against using too small of an enclosure for the servo subs.  I built a pair of the 12 inch servo's into a small modified U alignment for a build I was doing with the original Wedgies:





Its difficult to see but you can get a feel for where the drivers were with reference to each other and the size of the cabinet, really just large enough to house the drivers.  What I found with this cabinet was that the drivers would go non-linear when driven hard.  I can only attribute this to the cabinet, I am currently using the same amps and drivers for the H frames in my signature.  I ended up tossing these cabinets. I theorized that the front of the cabinet was becoming pressurized as compared to the back half so there was greater resistance to the cone return on that side of the driver.

Given my experience I would recommend building a quick and dirty test cabinet when trying to go small using these drivers.

Best,
Ed

[dayneger]

Hi Ed, thanks for sharing your experience.  First, I gotta say... nice work.  Those look great!   

I theorized that the front of the cabinet was becoming pressurized as compared to the back half so there was greater resistance to the cone return on that side of the driver.

Given my experience I would recommend building a quick and dirty test cabinet when trying to go small using these drivers.

The asymmetry there is interesting to understand... but good to know that it didn't pan out well in your build.  Apparently that particular combination of driver and servo and asymmetry wasn't a winner.

Your advice to build a test cabinet is super wise and much appreciated.  I'm a huge proponent of mockups and prototypes in development.

Has GR tested layouts other than H and W?  Why does the W sound worse... the allegedly insufficient cabinet design or some other reason?

[ebag4]

I should have mentioned, others have had success with this modified "U" alignment using the servos, I believe there are several examples using the 8" drivers and I seem to recall that Mike has a set using the 12" drivers.  Those were similar in design but larger and as far as I know worked as expected. I believe more airflow is required even in a cabinet open on one end, my cabinets were filled by the drivers to the extent that the airflow was restricted from the enclosed end of the cabinet, further impacted by the asymmetrical enclosure as you mentioned, the cabinet getting smaller towards the enclosed end.

The concept can work, my application failed.

With regard to "W" alignment issues, I haven't built one but I believe the biggest issue is bracing the large open section of the cabinet while still being able to load the drivers into the baffle.

Best,
Ed

[corndog71]

Not to be snarky but Danny introduced his OB subs around 15 years ago.  If there was a better way to do them, Danny or someone else would have figured it out by now.

[dayneger]

Not to be snarky but Danny introduced his OB subs around 15 years ago.  If there was a better way to do them, Danny or someone else would have figured it out by now.

That's cool, I can do snarky. 

The point of this thread isn't to better the H-frames--it's to see whether I can come reasonably close to their performance in what I consider a more visually integrated fashion, on a single footprint that includes the Rhythmik amp, and that fits with the space I have for them.

It would be fair to say that 15 years later, the GR offerings with 12" servos don't meet my personal goals. That's meant as an observation, not an accusation. I also don't know whether Danny's tried to meet the needs of my particular market segment.

Either way--is there a point in dissing me for trying?

[Early B.]

That's cool, I can do snarky. 

The point of this thread isn't to better the H-frames--it's to see whether I can come reasonably close to their performance in what I consider a more visually integrated fashion, on a single footprint that includes the Rhythmik amp, and that fits with the space I have for them.

It would be fair to say that 15 years later, the GR offerings with 12" servos don't meet my personal goals. That's meant as an observation, not an accusation. I also don't know whether Danny's tried to meet the needs of my particular market segment.

Take a deep breath and let it go, man. Just buy a pair of speakers that suits your needs. Don't attempt to design your own speaker of this magnitude (this advice is coming from another novice who designed his current speakers ). Your actual question should be -- "What speaker comes close to providing the bass performance of OB servo subs based on my personal preferences and budget?"
       

[Danny Richie]

I also don't know whether Danny's tried to meet the needs of my particular market segment.

This variation with three 8" servo subs is coming.

[mlundy57]

I should have mentioned, others have had success with this modified "U" alignment using the servos, I believe there are several examples using the 8" drivers and I seem to recall that Mike has a set using the 12" drivers.  Those were similar in design but larger and as far as I know worked as expected. I believe more airflow is required even in a cabinet open on one end, my cabinets were filled by the drivers to the extent that the airflow was restricted from the enclosed end of the cabinet, further impacted by the asymmetrical enclosure as you mentioned, the cabinet getting smaller towards the enclosed end.

The concept can work, my application failed.

With regard to "W" alignment issues, I haven't built one but I believe the biggest issue is bracing the large open section of the cabinet while still being able to load the drivers into the baffle.

Best,
Ed

I had a set using the 12" drivers in a wedge shaped cabinet to better match the form of the Wedgies.







These worked pretty well, better than the triple 8's I had the year before in H-Frames



The triple 8's were really good but the two 12's were better which makes sense given that two 12" drivers have 50% more surface area than three 8" drivers.

To go with the Wedgie, the wedge design was fine though I would make all the dimensions and angles the same except the front would be a couple inches wider. This would give the upper driver a little more breathing room.

With the wider NX-Otica MTMs, the narrow wedge shaped base wasn't needed for aesthetic reasons so I went back to H-Frames. The same drivers and amps preform better in the H-frames than in the wedge shaped cabinet.

Using the wedge shaped cabinets with the Wedgies is a trade off. You give up some performance for a more pleasing look.

[mlundy57]

This variation with three 8" servo subs is coming.

IIRC, this is how you originally envisioned the Otica.

[dayneger]

The triple 8's were really good but the two 12's were better which makes sense given that two 12" drivers have 50% more surface area than three 8" drivers.

Mike neatly summarized the challenge.  With my 17 x 20 x 8' room that has a large open corner, the advice from the team here has been dual 12" servos at the minimum, even votes for triple 12s... darn you all!   

Although consequently not quite what I'm looking for, I do feel the triple 8" servos will be a nice offering--trim and to the point for the appropriate spaces.  Could the amps be integrated on the same footprint?

With time I'd like to play with servo ripoles just to see what actually happens when reality meets the road.  The potential size compression and/or hiding of drivers remains deeply interesting. 

However, for the moment I've decided to see what could be done with essentially "forward-facing" driver orientations.  The day job's super busy at the moment, which is slowing me down.  Soon I'll post updated visuals of my latest thought experiments for feedback.

Danny--in the approximately 60/80-200 Hz range, does the sealed 12" of the Brute somehow exceed the OB 4x 165s of the full Oticas?  Or are they simply different?  I'm puzzling over the conversations around mid-bass slam and "miss-manners" mid-range.

A separate question is at what XO frequency the servo subs would ideally hand over to other drivers?  If you had servo 12's under the Brutes, where would the Eminence driver take over for best sound?

Thanks!

[Tyson]

Mike neatly summarized the challenge.  With my 17 x 20 x 8' room that has a large open corner, the advice from the team here has been dual 12" servos at the minimum, even votes for triple 12s... darn you all!   

Although consequently not quite what I'm looking for, I do feel the triple 8" servos will be a nice offering--trim and to the point for the appropriate spaces.  Could the amps be integrated on the same footprint?

With time I'd like to play with servo ripoles just to see what actually happens when reality meets the road.  The potential size compression and/or hiding of drivers remains deeply interesting. 

However, for the moment I've decided to see what could be done with essentially "forward-facing" driver orientations.  The day job's super busy at the moment, which is slowing me down.  Soon I'll post updated visuals of my latest thought experiments for feedback.

Danny--in the approximately 60/80-200 Hz range, does the sealed 12" of the Brute somehow exceed the OB 4x 165s of the full Oticas?  Or are they simply different?  I'm puzzling over the conversations around mid-bass slam and "miss-manners" mid-range.

A separate question is at what XO frequency the servo subs would ideally hand over to other drivers?  If you had servo 12's under the Brutes, where would the Eminence driver take over for best sound?

Thanks!

Well, let me be the voice of dissent here, re: the triple 8's and the dual 12's.  IME, the 12's are best in class for 'under 100hz' bass.  But they don't do upper bass as well as some other woofers.  The triple 8's in the compact-Otica design will actually give you better upper bass integration than the H-Frame 12's.

Here's how I'd break down the performance - upper bass the 8's will do better.   Mid bass will be a tie between the triple 8's and the dual H-Frame 12's.  Low bass the 12's will do better.  IMO, having better upper bass performance is more important with the MTM-Otica design because they only go down to around 150hz so you need something that will blend seamlessly with them in that region.  The 8's will do this the best, the H-Frame 12's will be 2nd best, and the ripole 12's will be the worst. 

[mlundy57]

Well, let me be the voice of dissent here, re: the triple 8's and the dual 12's.  IME, the 12's are best in class for 'under 100hz' bass.  But they don't do upper bass as well as some other woofers.  The triple 8's in the compact-Otica design will actually give you better upper bass integration than the H-Frame 12's.

Here's how I'd break down the performance - upper bass the 8's will do better.   Mid bass will be a tie between the triple 8's and the dual H-Frame 12's.  Low bass the 12's will do better.  IMO, having better upper bass performance is more important with the MTM-Otica design because they only go down to around 150hz so you need something that will blend seamlessly with them in that region.  The 8's will do this the best, the H-Frame 12's will be 2nd best, and the ripole 12's will be the worst.

Agreed. Like everything in audio there are trade offs for sure.  My MTM Oticas are -6dB at 80Hz which is where I cross them to the dual 12s. The trade off here is the NX drivers are covering the upper bass. The triple 8s will do this better than the two NX midwoofers. Also, as Tyson says, the 8s can be crossed to the NX drivers a lot higher like the current full size NX-Otica. This would result in better midrange performance.

As noted, the weakness of the 8s compared to the 12s is in the lower bass. While the 8s are capable of playing down to 20Hz, I was never able to get solid performance out of them much below 30Hz at the listening position while the 12s are strong down to 20Hz and -3 around 16Hz.

For uncompromised full range performance, the answer is MTM with triple 8s paired with triple 12s, the four tower arrangement. Any two tower system is going to be a compromise. Better upper bass and midrange on one hand, better low and sub bass on the other. One is not better than the other. Only better suited for a given preference.

[dayneger]

Well, let me be the voice of dissent here, re: the triple 8's and the dual 12's.  IME, the 12's are best in class for 'under 100hz' bass.  But they don't do upper bass as well as some other woofers.  The triple 8's in the compact-Otica design will actually give you better upper bass integration than the H-Frame 12's.

For me this isn't dissent, it's awesome feedback!  Exactly the kind of thing I was hoping to learn vicariously. 

So, the 12" servo subs can apparently easily play up to 200 Hz, but what I'm hearing is that they're not necessarily the best-sounding choice over about 100 Hz, where the triple 8's (or something else) would be better.  How about a passive 10-12" OB driver effectively between the servo 12s and the MTM section?  Covering from, say, 80/100-300 Hz? 

I'm working on a layout idea (that kills my height goals  ) to incorporate that idea.  Unload the 165NQs of the upper bass for better mid-range performance as Mike noted, maybe getting more visceral impact in the mid/upper bass at the same time?

As noted, the weakness of the 8s compared to the 12s is in the lower bass. While the 8s are capable of playing down to 20Hz, I was never able to get solid performance out of them much below 30Hz at the listening position while the 12s are strong down to 20Hz and -3 around 16Hz.

Mike, I've resigned myself to the inevitability of dual 12" servo drivers per side based on this kind of consistent commentary... darn it!  I just know myself too well.     Skipping multiple 12" massive drivers per side would certainly make some things easier!

[Tyson]

Why not just build the compact Otica and get a sealed sub and put it in the corner?  That would give you a small footprint, very good midbass from the triple 8's and very good ultra low bass with the sealed sub.