[gooberdude]

One interesting aspect that led me to buy an ob servo sub system is that power requirements are less critical .  The A370 rhythmik amps are certainly powerful enough, but according to danny richie it takes less power to produce prodigious bass with a servo system.

The best metaphor that i've heard about servo subs is in comparison to a sports car.  The servo subs are not like adding a bigger engine or turbo, they are like adding a better/bigger braking system.  Its not the 'start' in other words, its the 'stop'.

You can go faster, deeper into a corner & then pour on the power when you want to...not when natural forces like inertia force you to make corrections...

I'm still waiting for Rclark tp produce some links to info on the negative side of ob servo subs.  I can't find any, regardless of mfgr of the system.

[medium jim]

Gooberdude:

Please don't hold your breath waiting for RClark

Jim

[Rclark]

It's just what I found in my own searches, not meant to upset anyone by it. I'm sure your subs are awesome.

 And had nothing to do with negative on servo's, funny that's how you took it though.

[Davey]

No, not sensor accuracy.  Accelerometers or even a second voice-coil are going to yield a pretty accurate error-correction voltage.
The power amp has the difficult job.  There's a large motor with a lot of mass that it needs to drive/control.  Many times woofers are mounted in too small of boxes in order to keep the systems compact for aesthetics.  Small boxes require even more power.  Other issues as well.

Much of the distortion is inherent (non-linear) in the drivers themselves and can't be corrected.

However, it does become somewhat of an apples/oranges scenario because, by definition, the 'amplifier' is not the same since a closed-loop control system has been created with the servo configuration.

I have no doubt that servo-controlled systems can reduce measurable distortions quite a bit, but 20db is a large reduction..... assuming all other factors are also considered with a relative comparison to a non-servo-controlled system.

Cheers,

Dave.

[gooberdude]

Thanks Jim   

Seems like we all walk tall but carry small sticks around here.  Sure seems like the term SOTA is centered around ob servo subs recently.

[Rclark]

 You know what,with that comment, I will go do some searches. I can remember even a video shootout that won't be hard to find, and guess what, the rythmik (gasp) didn't win.

 Seems like if we don't get stroked the right way our panties get wadded up is more like it

[gooberdude]

Or it could be that your comments aren't welcome, way too often


Youtube away bro...

[Rclark]

 Sure. Already found one. Took all of 30 seconds. Hsu was said to be as good sonically as the rythmik.

"Then there's the HSU. It tied with the Rythmik in sound quality over the other subs, and again these two had their own distinct sound so you might prefer one over the other. The Hsu had the least output average, but only by about 2.8db. Oddly enough it shook the couch more than any other sub. One of the things we loved about this sub besides its looks was that it never complained no matter how loud it went. An outstanding sub all around."

 http://www.avsforum.com/t/1313176/shootout-epik-empire-vs-hsu-vtf-15h-vs-cht-cs18-1-vs-rythmik-fv15-vs-ed-a7s-450

 You asked, I said I wasn't interested, it's not a big deal, but then you insult, so I'll go ahead and find what you want.

 And before you dive in with the obvious nitpick, that these are ported and somehow don't matter, it's a SERVO sub, the HSU isn't, yet the HSU was an equal match.

[Rclark]

Another, took me about a minute to find

http://www.avsforum.com/t/1316431/svs-pb13-vs-submersive-vs-2-x-rythmik-in-a-large-space

"IMO rythmiks are WAY overhyped and don't offer anything more that a basic 15" or 12" sub in a box with 15 year old tech behind the wheel.
 and yes, I've heard the F15, HP and regular (4 in 1 room) as well as F12."

"Servo is a gimmick. plain and simple. If it is sooo great, why isn't every company using it right? The rythmiks are good, don't get me wrong, but they get so hyped up. I'm guessing most people are going from a real crappy sub to the rythmik and calling it the holy grail of subs. I will admit in my day I though that the cerwin vega sub I had was amazing. I've since changed to well over 30 different subs"

 Pretty sure I could do this all night.

http://forum.audiogon.com/cgi-bin/fr.pl?bhome&1325025368

 "If a pair of 12" Rythmiks weren't well under half the price of a pair of 12" JLs, I probably wouldn't have gone there either - home trial or no home trial. Buy, unpack, set up, evaluate, re-pack, re-ship a big ass box...maybe not.

However,.....

Once I decided to commit to quality subs in my system, I auditioned a sh*tload of subwoofers (most on more than one occasion) over the course of 12-18 months. The results of those auditions varied widely (as did the quality of dealer demo). The variability of subwoofer set-up care, demo system, demo room, etc. really hindered my ability to reach confident conclusions re: relative subwoofer performance, model to model. At the end of the day, I thought that the JLs were the best of the lot"

 

[JohnR]

That's very selective reading/quoting there, Rclark. I can do that too. From AVS thread:

"I have Rythmiks. Four of them. I have 2 of the LMS5400's. I have 2 of the Maelstrom-X 18". I have the SVS. I have a DTS-10. I built a THT with a Rythmik driver. I would take the Rythmiks over all of them. They sound the best. They can go as loud as I can stand."

From the AVS review:

"Rythmik's FV15 is a ported sub that has the sound quality of a sealed - a high-end sealed sub. It amazed us how clean and tight the sound was - at very loud volumes. You would never guess it's a ported sub except for it's output down low. It went the deepest of any of the subs, which is to be expected, and made it's presence known on some material where the other subs didn't."

It's good for you to post some links, though, finally, so thanks for doing that.

[JohnR]

I have no doubt that servo-controlled systems can reduce measurable distortions quite a bit, but 20db is a large reduction..... assuming all other factors are also considered with a relative comparison to a non-servo-controlled system.

Thanks for those thoughts. I read an XBL whitepaper that claimed around 4x reduction for their motor system. So there is more than one way to skin a cat.

Reducing excursion would presumably be another.
 

[Freo-1]

It's Genesis advertising copy.  Of course they would tout their superior performance and claims. 

You may want to re-read my sentence about the X10 reduction.  I said "all other things being equal."  That means if say, two identical woofers were utilized...you stayed within Xmax....same box....etc, etc, one with a properly implemented servo-control system and one without were used, then a X10 reduction in distortion would not be possible.  I don't believe that's an untrue statement.
Maybe you can find/quote some other advertising copy that disproves that?

Anyways, if it's so much better a solution, then your original query is very apt.  Why do you think there aren't more available?
I believe the question has already been answered in this thread.  They're too complicated and too expensive for the relative performance gain.  Just my opinion.

Cheers,

Dave.

Go check reviews on actual measurements of subwoofers, and you will find that non servo units (often) do indeed go above 10% distortion, while servo units (generally) stay at 1% or less.  They may be a bit more expensive to produce, but we are talking high end audio here, which is a niche market in and of itself.

[pslate]

Ever listen to two different monitors using identical drivers and think, one set had the magic, and the other was grating on the ears? I know sub systems are less complicated than a well designed three way, or two way monitor, but I think the analogy is still good. It's the whole system that matters, and most of all how it sounds to you. Rythmik probably takes both vitriol and praise being such a prominent example of servo technology. I think they sound fantastic, but it certainly does not mean non-servo subs cannot sound as good (depending on the formula).

[medium jim]

Too much smack talk I'm glad that it got back on topic

Thanks,
Jim

[randytsuch]

Thanks for the info.

http://forum.audiogon.com/cgi-bin/fr.pl?bhome&1325025368

 "If a pair of 12" Rythmiks weren't well under half the price of a pair of 12" JLs, I probably wouldn't have gone there either - home trial or no home trial. Buy, unpack, set up, evaluate, re-pack, re-ship a big ass box...maybe not.

However,.....

Once I decided to commit to quality subs in my system, I auditioned a sh*tload of subwoofers (most on more than one occasion) over the course of 12-18 months. The results of those auditions varied widely (as did the quality of dealer demo). The variability of subwoofer set-up care, demo system, demo room, etc. really hindered my ability to reach confident conclusions re: relative subwoofer performance, model to model. At the end of the day, I thought that the JLs were the best of the lot"

OK, but in reading that thread, that guy ended up with two Rythmiks in his system.  Was a cost to performance issue.

I had already found the thread that liked both the Rythmik and Hsu subs, I mentioned that in one post.

And, IMHO, the other AVS thread has a lot of opinions, but there is one guy on that thread who appeared to not like Rythmik, and it was kind of unclear the conditions of how he heard the Rythmik, and what he really compared it to.

One think with Rythmik's is that you can buy the pieces and DIY you own (what I did), but in that case you have a one off, and the quality of your Rythmik depend on many factors.

And one last thought on the subject.
When I read "reviews" on audio forums, I take them with a grain of salt.  You don't know the pedigree of the reviewer and other factors that could affect the review.

I take more stock in reviews from internet sites.

http://www.enjoythemusic.com/magazine/equipment/0709/rythmik_f12se.htm

http://www.audioholics.com/reviews/speakers/subwoofers/rythmik-audio-f25-fl

Randy

[srb]

One think with Rythmik's is that you can buy the pieces and DIY you own (what I did), but in that case you have a one off, and the quality of your Rythmik depend on many factors.

If you build the correctly size braced enclosure and line it with a damping material (as one would do with any DIY speaker project), what other factors exist to affect sound quality?

Steve

[JohnR]

The binding posts - they make all the difference.

[srb]

The binding posts - they make all the difference.

If it were a passive subwoofer enclosure, then one could run the internal speaker leads through a hole below the binding post, using the post only as a clamp to the external speaker cables and bypassing the post as an inline circuit element.

But because the servo driver is intended to be driven by the servo plate amp, I assume the majority of builders would be installing the plate amp into the subwoofer enclosure which would be directly wired to the driver - no binding posts.

Your response is likely tongue-in-cheek, but seriously, if the cabinet plans are followed I see little difference between a factory Rythmik and a DIY Rythmik and can't imagine "many factors".

Although the Rythmik is one of the more affordable servo subwoofers on the market, I don't see the servo subwoofer as being all that rare with a variety of servo models available from major manufacturers such as Martin Logan, Paradigm and Velodyne in addition to those from the smaller custom manufacturers.

Steve

[TRADERXFAN]

SRB I think the rythmik is patented circuit and would be a different design than others you mention.  That alone doesn't indicate anything, just saying trying one doesn't mean you tried them all.

And just wanted to highlight something about the earlier back and forth, the OB servo sub Gooberdude mentioned is a bit of a different approach than "boxed" servo sub.  A lot of quotes were about the non-ob versions.  How you use the tool in your room makes all of the difference, so YMMV.  The room will play a large part of the experience and some will or won't recognize a benefit.

[Rclark]

Randy, my point wasn't to say I think servo subs are probably worse, only that I've found in my searches that lots of other people have found other types of subs to be just as good. That's all.

and a couple of those might not have been the best examples, but all I did was a quick and dirty search. Anyway, please carry on with the conversation.