Rythmik Audio 18s

[billy p]

I understand that Rythmik is currently working on 18" prototype based on the vented model. Will there be any chance of a possible big brother to the sealed units like the E/F 15s.

I asked this question on another forum but did not get a reply.... Likely because the Rythmik owners thread went in another direction...a sealed 18 is exactly what I'm looking for at this point.

Any help in this regard would be appreciated...

Bill

[billy p]

Reply from Rythmik Audio @ AVS

In terms of product plan, we will put ported version of 18" and dual 15" in higher priority. They won't be available until late summer. The sealed version is at a lower priority.

[eyecatcher]

Damn, I love my F15HP but I would be really interested in a compact sealed high power/excursion 18" rythmik servo, aluminum cone, rubber surround would be mint. Not too much competition out there either.

[N Boros]

Damn, I love my F15HP but I would be really interested in a compact sealed high power/excursion 18" rythmik servo, aluminum cone, rubber surround would be mint. Not too much competition out there either.

Maybe the 18" driver will be available for DIY, like the other drivers at this point. A sealed subwoofer is probably the easiest to DIY, from what others have said. Or you might be able to Salk do a custom 18" sealed sub for you.

I'm happy to hear that the 18" vented sub or dual 15" sub is a priority. I have a basement theater, where the theater area is open to the entire basement. The space that I need to pressurize is 10,000 to 12,000 cubic feet. I'm thinking about putting up a wall to get the space down to a more manageable 6,000 cubic feet, where maybe I don't need such a large subwoofer. I guess I will have to do a cost estimate though and maybe one of these newer models will be the cheaper option for me. I can understand why Brian is putting more of a priority on the vented models. With most people's newer homes having open floor plans, there is a big demand for big output subwoofers. It is great that we can also be assured that there are options, with Rythmik to ensure the bigger output subs will remain accurate.

[billy p]

Well I decided to go with a Funk Audio 18.0. I've thought about DIY...I know JS builds with Rythmik...not sure what size or how big a cab you'd need for the new 18s... until one is modded but I want a small footprint <4^3ft moving from a sb13 + xs30se...his curved designs are simply stunning...:cool:

[curtis]

Well I decided to go with a Funk Audio 18.0. I've thought about DIY...I know JS builds with Rythmik...not sure what size or how big a cab you'd need for the new 18s... until one is modded but I want a small footprint <4^3ft moving from a sb13 + xs30se...his curved designs are simply stunning...:cool:
Looking forward to a picture!

[billy p]

Curtis...I just unpacked it...I have not given it a listen yet...but hope to in the coming days. His work is utterly stunning...but I must piece together the HT first...I only recently unpacked my speakers...HT conversion will be fun.. trying to integrate and position my Towers + huge CC into our 10*15*9 den which measures 1350^3ft.

I'm expecting some wonderful synergy from the Ascends and FA 18...once it happens..:)

1362 1363
1364 1365
1366

[Jack1949]

Wow that's a beautiful sub! Can't wait to hear your impressions.

[curtis]

....trying to integrate and position my Towers + huge CC into our 10*15*9 den which measures 1350^3ft.

I'll trade you my Sierra-2's at no cost to help with the space. 😁

[billy p]

I'll trade you my Sierra-2's at no cost to help with the space. ��

Don't laugh but that thought has merit....ive considered trading down. The new room is mine and will not be a multi faceted...so everything should be fine.

[curtis]

Don't laugh but that thought has merit....ive considered trading down. The new room is mine and will not be a multi faceted...so everything should be fine.
Well...in any case...I'm here for you. :D

[N Boros]

Anyone know when the new larger ported Rythmik subwoofers are coming out? I think that there is supposed to be a ported model with two 15 inch drivers (FV25 ?) and another ported model with one 18 inch driver (FV18 ? ). I've seen a few posts on AVS about it coming out in the Fall and someone else said October, but I usually don't post over at AVS since threads can get huge and often folks can just get nasty over there.

[Blutarsky]

Just announced today:
https://www.svsound.com/pages/subwoofers#16-ultra

[N Boros]

I saw this yesterday too. I get excited reading about new products like this. Especially things from SVS. They do put together some top notch products. I do think it is funny the sizes of the woofers they choose though. They first came out with a 13" woofer, maybe just so that people will see it is slightly larger than the typical 12" woofers that were the common size several years ago. Now the new subwoofer has a 16" inch woofer because of the proliferation of 15" woofers. Though in the past couple years the 18" woofer is becoming an option from many internet direct subwoofers. I'm surprised that they didn't come out with a 19" woofer. :)

This just gets me more excited to hear about the upcoming Rythmik subwoofers. I'm guessing that the two new ported models might come in at less than the new SVS models. If that is the case, then I think I would still lean more towards Rythmik than SVS. Right now for example, if I needed the output of a PB13 Ultra or a PC13 Ultra I think that the Rythmik FV15hp offers a bit more performance in just raw output in addition to the servo technology and at a lower price.

[billy p]

Well in the case of Svs....the U16 has being in development going on 5-6 yrs. Reflecting back at that period... it would have being something else... now...meh.
I've heard both variations of the Ultras...even had the SB13U for ~4 months. It was good but it didn't exhibit that tremendous mid-bass we mostly crave and ultimately want for music or visceral movie effects.

You can't deny Svs stature worldwide...id be curious to see how the Rythmiks and Ultra stack up....I'd take the 18 until proven otherwise...:)

[N Boros]

Well in the case of Svs....the U16 has being in development going on 5-6 yrs. Reflecting back at that period... it would have being something else... now...meh.


You are right! I had forgotten about this until just now. Right after the SVS PB13 Ultra was first reviewed by Audioholics and Data-bass was starting to take off I was really excited about the SVS offerings and their performance. Soon after I saw the SB16 announced and was really excited. They scrapped the idea because of the significant cost of neodym. Here is the original ad:

https://drive.google.com/open?id=0B_q3Z7pK4yL0djlwWXMtdWpLb1U

This is pretty remarkable that they were able to bring it out several years later at a cheaper price with what looks like on the spec sheet more performance.

[Blutarsky]

The new SVS 16'ers have a 1500W amp. I wonder how this power will translate into sound compared to Rythmik? the sealed box model is only 19.5" wide... DSP vs. accelerometer? I wish I had a bunch of new subs in my room to play with. Affordable high value audio is getting better every day.:)

[N Boros]

The new SVS 16'ers have a 1500W amp. I wonder how this power will translate into sound compared to Rythmik? the sealed box model is only 19.5" wide... DSP vs. accelerometer? I wish I had a bunch of new subs in my room to play with. Affordable high value audio is getting better every day.:)

I asked the same question a while ago and here is what Brian responded with:

http://forum.ascendacoustics.com/showthread.php?6071-Differences-between-SVS-and-Rythmik

I only picked up some of what he was talking about, but to me it seems like what Rythmik has going on is more sophisticated and will transfer to some audible differences. SVS seems to just simply limit the output with a DSP if the THD is going to get excessive. Apparently there are trade offs for doing this. On the one hand the THD is exceptionally low and it is really tough to get it to make any bad noises from asking it to play too loud. It just stops playing louder even when asked to do so. But, there are other forms of distortion than just THD that one gets that are a bigger problem, that crop up as a result. Rythmik seems to attack the this problem from a different angle. Rythmik subs keep some of the other forms of distortion in check, since they are more important. As a result the THD looks worse than that of the SVS, but apparently it doesn't matter. Like I said I'm still trying to wrap my head around it, but it is starting to make sense.

[davef]

The new SVS 16'ers have a 1500W amp. I wonder how this power will translate into sound compared to Rythmik? the sealed box model is only 19.5" wide... DSP vs. accelerometer? I wish I had a bunch of new subs in my room to play with. Affordable high value audio is getting better every day.:)

DSP is not comparable to servo. DSP is one method (actually, a lesser expensive method these days) for equalizing / contouring the subwoofer's response as opposed to equalizing by analog means. It means the LFE signal that is being sent to the sub is once again converted to digital - then various filters are applied to the digital signal, and then it is once again converted to analog so it can be amplified and then sent to the woofer.

Regardless of how good the DAC's are - each time an analog signal is converted to digital and then back again, information is lost.

Servo is a real time solution whereby the woofer sends a continuous signal back to the amplifier, so that the amplifier makes sure the woofer is properly tracking the signal being sent to it.

DSP does not have any effect on overall sound quality other than adding additional features and a simpler way of implementing eq. In fact, because of the additional A/D D/A conversions, it has a negative effect on the purity of the original signal being sent. These days, there are way to many A/D D/A conversions taking place in the audio chain. DSP in a sub would be more beneficial if the LFE output itself were digital.

I'll take servo any day of the week when it comes to sound quality in a subwoofer.

[billy p]

The most important aspect of the sub IMO is the driver itself....efficiency, inductance...motor strength...distortion.... will shape or identify the SQ...long before a servo or DSP is put in chain.

I suspect even you Dave would be impressed with the TSAD specs at DB in the Funk subs...I'm using no eq....and its awesome...its basically an extension of the Towers only better...:)

[sludgeogre]

The new SVS 16'ers have a 1500W amp. I wonder how this power will translate into sound compared to Rythmik? the sealed box model is only 19.5" wide... DSP vs. accelerometer? I wish I had a bunch of new subs in my room to play with. Affordable high value audio is getting better every day.:)

A servo sub is managing the backwave radiation inside the box to heavily reduce it, other subs can't do that, or just have overbuilt boxes to manage it. It means that the signal the servo sub produces will be more accurate. Normal subs need a bigger amp to deal with the deleterious effects that they can't manage. Also, Rythmik subs are direct servo, so they don't use an accelerometer, they use a sensing coil that is in the same magnet gap as the voice coil. The sensing coil sends feedback to the amp and corrects the signal being sent to the woofer. The result is a much more accurate signal.

This is why I don't understand why more companies don't implement a direct servo design. It must just be difficult to do correctly, or they just want to market giant amps and boxes, because people like big amps and big boxes, especially ones that shake a lot. It's probably more of the latter and some of the former. I mean my Dad put floor shakers in his theater as well as having a big rumbly sub. It was too much for me. I prefer accuracy and gut punching depths of rock solid sub 20 Hz bass that Rythmik subs provide. When I first heard that kind of bass from my dual F12's, it scared the hell out of me and I was immediately thrilled as my heart instantly sank because my neighbors must have been freaked out. I was immediately addicted.


DSP is not comparable to servo. DSP is one method (actually, a lesser expensive method these days) for equalizing / contouring the subwoofer's response as opposed to equalizing by analog means. It means the LFE signal that is being sent to the sub is once again converted to digital - then various filters are applied to the digital signal, and then it is once again converted to analog so it can be amplified and then sent to the woofer.

Regardless of how good the DAC's are - each time an analog signal is converted to digital and then back again, information is lost.

Servo is a real time solution whereby the woofer sends a continuous signal back to the amplifier, so that the amplifier makes sure the woofer is properly tracking the signal being sent to it.

DSP does not have any effect on overall sound quality other than adding additional features and a simpler way of implementing eq. In fact, because of the additional A/D D/A conversions, it has a negative effect on the purity of the original signal being sent. These days, there are way to many A/D D/A conversions taking place in the audio chain. DSP in a sub would be more beneficial if the LFE output itself were digital.

I'll take servo any day of the week when it comes to sound quality in a subwoofer.

I love this post. This is true audiophile engineering here. Keep the signal pure and do as much as you can to keep it that way at every step. This is why I love my Schiit Bifrost Multibit so much. It stays out of the way of the music. It's so accurate, I constantly notice new things. I'm listening to Wedding Nails by Porcupine Tree again and I never really noticed how much ambient keyboard there is in the background before. You can't discover new and incredible details in music you've listened to for years on a system that is constantly screwing with the signal you send it.

[N Boros]

DSP is not comparable to servo. DSP is one method (actually, a lesser expensive method these days) for equalizing / contouring the subwoofer's response as opposed to equalizing by analog means. It means the LFE signal that is being sent to the sub is once again converted to digital - then various filters are applied to the digital signal, and then it is once again converted to analog so it can be amplified and then sent to the woofer.

Regardless of how good the DAC's are - each time an analog signal is converted to digital and then back again, information is lost.

Servo is a real time solution whereby the woofer sends a continuous signal back to the amplifier, so that the amplifier makes sure the woofer is properly tracking the signal being sent to it.

DSP does not have any effect on overall sound quality other than adding additional features and a simpler way of implementing eq. In fact, because of the additional A/D D/A conversions, it has a negative effect on the purity of the original signal being sent. These days, there are way to many A/D D/A conversions taking place in the audio chain. DSP in a sub would be more beneficial if the LFE output itself were digital.

I'll take servo any day of the week when it comes to sound quality in a subwoofer.

That is a really helpful explanaintion of the differences! This is really simple to understand as well. I do have a follow up question though. Filtering the analog signal in real time sounds kind of tricky. Is it kind of like just a sophisticated graphic equalizer boosting or cutting frequencies that differ from when the true signal is supposed to be (where this difference is measured in the accelerometer)?

[curtis]

That is a really helpful explanaintion of the differences! This is really simple to understand as well. I do have a follow up question though. Filtering the analog signal in real time sounds kind of tricky. Is it kind of like just a sophisticated graphic equalizer boosting or cutting frequencies that differ from when the true signal is supposed to be (where this difference is measured in the accelerometer)?
I can't explain it like Dave, but servo control is not a filter in the same sense as an EQ. It tracks the position of the woofer vs the output of the amplifier. It corrects in real time rather than preset filters....so it can handle anomalies such as the environment, memory, etc. On top of what the servo does, you can apply traditional EQ to it...as evidence of the parametric EQ on the amp.

and as sludge said, the Rythmiks use a sensing coil, not an accelerometer.

[curtis]

I love this post. This is true audiophile engineering here. Keep the signal pure and do as much as you can to keep it that way at every step.
I believe this is why Dave spends so much time on getting the drivers in his speakers "right". Doing this means there is less interference needed by the crossover.

[billy p]

I believe this is why Dave spends so much time on getting the drivers in his speakers "right". Doing this means there is less interference needed by the crossover.

Having control of the driver design from the ground up is what makes Rythmik, Funk, JTR, Seaton and Svs for that matter so unique. Dave relationship with his OEM is likely unparalleled...geting the right driver for the given task helps eliminate some of the added processing to reach the desired results.

Most of the DIY community don't have this available to them and why off the shelf parts need plenty of tweaking but if done right can be made to sound just as good.

Not trying to play devil's advocate here but I can guarantee you any sub from the Seaton, JTR or Funk will sound great with or without a servo.... JMO.

[RythmikAudio]

If you imagine all drivers are same out of the factory, then the benefits of servo is just improving distortion and make the bass sound less boxy. Let us assume that for a moment. The Achilles heel in stoping boxy sound is the cone itself. We all build thick wall enclosure to stop the internal boxy sound from coming out through walls. But how about the cone? Does the boxy internal sound just magically avoid the cone? So after we build a thick wall enclosure, all the boxy sound now comes out from the cone. Servo reduces that boxy sound coming through the cone by up to 10x in energy becasue servo fight against any unintentional cone movement that is not in the signal source. To measure that you need to place another driver in the back of the enclsoure to emulate a source of boxy sound. Then you measure how much the cone moves under this pressure. One measurement for servo and one measurement for nonservo and you get the improvement. That is how much clarity servo can improve.

Now if you look at another real world issue called variation which servo also helps. Variation consists of aging, unit to unit variation and batch to batch variation. There is an JL audio discussion on the version of firmware in those subs even for the same model. Why did they do that? It is batch to batch variation. It is like in a factory that you recalibrate your tool once in a while. Servo makes that easy because it is a close loop system that all variations that I have named above are reduced by the servo feedback.

[billy p]

Thanks for explaining thing in layman terms. Rythmik was on my short list...hence my curiosity when I heard about the upcoming 18" designs.

Unfortunately...a single sealed 18"...was not in the plan at this time....so I had to focus on those mfg who offer the compact design I need for my current needs.

I'd like to experience a Rythmik product one day...in hindsight...I could have waited I suppose, given the current delays, not sure on when the new 18" will be coming out.

Unfortunately, most of the local folks I know are into DIY designs.... thankfully...I have not gone down that rabbit hole, nor do I have any future plans in doing so.

[mikesiskav]

Do the improvements from the Servo show up in measurements? Where would we see the improvement? FR? THD? Decay?

[RythmikAudio]

Yes and No. In the FR response, the FR will be consistent throughout different SPL levels (other than the area where driver/amplifier runs out of juice). The important characteristic of sound reproduction is coherence. If the FR cannot maintain consistency at all time, the sound is said to exhibit memory effect or random variation. Now the latter is actually much better than the former. So how to we come up with a way to separate random variation from memory effect? None of the existing measurement methods can do that. In order to do that, one has to do a very long sequence measurement and do a huge amount of statistical measurements that is beyond most audio engineers. In fact that is the bottleneck of audio measurement. Audio engineers assume transeducers are "time-invariant" system. So it does not matter when you measure at time A or time B. In fact it does. If you have two tests A and B, the test results will be slightly different if do measurement A immediately before measurement B vs. the other order. That is called history, state-depedent, and memory effect. One simple demonstration is measure the FR using frequency sweep, but do it twice, one from low frequency to high frequency and another from high frequency to low frequency. For most systems, the results are slightly different. Will audio engineers make a fuzz over that? Some may comment it is just a random variation. But if you repeat 100 times and you always see the same trend, then it is not random. What one sees is the subtley of memory effect. Another example, there are two ways to measurement frequnecy response, one is use signal sweep and another use white noise signal. The problem of the former is 20hz response is measured at time A and 60hz is measured at time B. So it does not measurement the system at the same time, therefore the result is susceptive to the "state" of the system (similar to what I say sweep low to high vs high to low give you slightly different result). White noise based frequency response measurement on the other hand measures frequency response of all frequency points at the same time simultaneously. It is not as susceptive to the "state" and yet it begin to expose system with problem, for instance, the FR has a lot of small zig-zag vs a very smooth frequency response. So some engineer come up with 3rd octave smoothing, and the small zig-zags are gone. So a lot of techniques we use in measurement unintentionally erase important detail. The above is just the start.

[taigovinda]

I have a 3-yr-old so drawn to down-firing. Is DIY (or Salk/Rythmik) the only option for down-firing right now? I was able to access an a D15SE link on Ascend via google search, but couldn't get there from within the Ascend site and it seems like it's maybe not part of the current offering.

My room is about 8000 sq ft and I have an Outlaw LMF-1+ that doubles as end table, will probably get rid of when upgrading to Rythmik... what size of Rythmik would be appropriate for this room? I was told at one point that the best bet is two vented high-powered 15's... that the quality difference from sealed to vented Rythmik is not that much anymore and vented just has higher output. I would like to be able to use the sub(s) as end tables or coffee tables ideally; not sure from a cost/WAF/sound quality factor whether a center-of-room coffee table sub (maybe 2x12 or 2x15) would be better or maybe one on each sidewall - one of the two could be an end table. Or if the 18 comes out before I jump in, maybe just one that sits where my current one is... Also not sure if these big subs - especially when down-firing - can be held to the right height dimension.

A lot in there - any input appreciated!

Tai

[davef]

I can't explain it like Dave, but servo control is not a filter in the same sense as an EQ. It tracks the position of the woofer vs the output of the amplifier. It corrects in real time rather than preset filters....so it can handle anomalies such as the environment, memory, etc. On top of what the servo does, you can apply traditional EQ to it...as evidence of the parametric EQ on the amp.

and as sludge said, the Rythmiks use a sensing coil, not an accelerometer.

Curtis is correct. By design, Rythmik woofers have an additional specialized coil in the motor assembly. This coil generates voltage due to its movement within the magnetic gap of the woofer (which is in unison with the cone itself). From this voltage source (which is fed back to the plate amp) - acceleration and woofer position can be determined and instantly compensated for in real time.

There are a few reasons why you don't see many manufacturers going this route:

1. It is very complex. You are not going to see this from other ID manufacturers or in the DIY crowd as it really does take a highly educated and experienced engineer to properly design. This is not something that can be modeled by software and it throws typical woofer design (which rely on Thiele Small parameters) into the garbage. With Servo, T/S params are practically meaningless as they are compensated for by the servo functionality. This is what Brian mentions in his post - T/S params for any woofer will change over time as the compliance of the suspension system changes.

2. Rythmik's method of servo is protected by patent. The other method of servo is by use of accelerometer mounted to the moving mass (typically on the cone itself or the former). This is patented by Velodyne.

One of the reasons, amongst many, that I am so fond of Rythmik's subs is that I have a lot of experience with servo and its many benefits. I was privileged to be an engineer for a company that was at the forefront of subwoofer design, this was back in the late 80's early 90's when subs were just starting to become mainstream. Back then we had only one real competitor - and that just happened to be Velodyne. I spent a lot of time with the late Dr. Lester Field, a part owner of the company I worked for and a brilliant PHD'd engineer. He spent a lot of time measuring and evaluating Velodyne subs and I was there to assist him. We blew up a lot of amps back in those days (and a few $4k B&K mic capsules), but it is a very fond memory for me as Doc (as I liked to call him) was one of my major influences, a true mentor.

More importantly, even way back then - we realized the rather dramatic improvements servo brought to subwoofers. I assisted Doc in his evaluation of developing our own method of servo, but sadly, it never came to fruition due to his passing.

A decade later, as we (Ascend) started to develop our own line of subwoofers - I was introduced to a little known DIY company called Rythmik. Brian and I had many discussions back then and I knew he was the real deal, exceeding my own knowledge of subwoofer design (which was extensive). After he sent me a fully assembled F12 - (all while I continually evaluated many ID offerings such as HSU and SVS) - I was both disappointed and hooked. Disappointed because I knew right then that I could not outdo this design in terms of sound quality (and sound quality over quantity was my goal) yet at the same time instantly hooked because this sub measured better and sounded better than anything else before it. I had data stored from close to a hundred different subwoofers from so many years of work in this field. In fact, it was the only ID sub I had measured that actually met its published specifications...

I instantly scrapped nearly two years of work on our subwoofer line - instead choosing to focus on assisting Brian in bringing these incredible servo subs to market.

[Blutarsky]

I have had 3 servo subs designed by my friend Arnie Nudell, who I believe is the inventor of the servo subwoofer. Since he retired I can't afford to buy his stuff. I was going to go with dual Rythmics but decided on a design without forward facing drivers because of my infamous terriers. When the day comes, I will be buying a pair of Rythmics.
Here is an article about Arnie and page 2 covers the Servo Sub.
http://www.stereophile.com/content/arnie-nudell-infinity-genesis#5Pwja0M11R5wcT0P.97

Having Dave chime in on the forum is special and unique....Thank's

[davef]

I have a 3-yr-old so drawn to down-firing. Is DIY (or Salk/Rythmik) the only option for down-firing right now? I was able to access an a D15SE link on Ascend via google search, but couldn't get there from within the Ascend site and it seems like it's maybe not part of the current offering.

My room is about 8000 sq ft and I have an Outlaw LMF-1+ that doubles as end table, will probably get rid of when upgrading to Rythmik... what size of Rythmik would be appropriate for this room? I was told at one point that the best bet is two vented high-powered 15's... that the quality difference from sealed to vented Rythmik is not that much anymore and vented just has higher output. I would like to be able to use the sub(s) as end tables or coffee tables ideally; not sure from a cost/WAF/sound quality factor whether a center-of-room coffee table sub (maybe 2x12 or 2x15) would be better or maybe one on each sidewall - one of the two could be an end table. Or if the 18 comes out before I jump in, maybe just one that sits where my current one is... Also not sure if these big subs - especially when down-firing - can be held to the right height dimension.

A lot in there - any input appreciated!

Tai

I am sorry Tai but the Rythmik D15 is no longer available. We have one here in the shop that I can offer to you, but we no longer have the appropriate packaging for shipping so you would have to arrange for a local pickup (if you are near our office)

[Blutarsky]

Both HSU and Outlaw have affordable down firing subwoofers. They are cheap enough to get a pair.
I use a pair of outlaw 12" now and I am satisfied...I'll give them a B grade. Servo is tighter.

B.

[davef]

That is a really helpful explanaintion of the differences! This is really simple to understand as well. I do have a follow up question though. Filtering the analog signal in real time sounds kind of tricky. Is it kind of like just a sophisticated graphic equalizer boosting or cutting frequencies that differ from when the true signal is supposed to be (where this difference is measured in the accelerometer)?

No - Servo is not about EQ in the conventional sense. Servo is about controlling the movement of the woofer. Generally speaking, it doesn't boost or cut frequencies.

Think about it this way - we have a B12 bomber that is about to drop a bomb and fire a guided missile. Both of these are aimed at hitting a specific target. For clarity, that target is the frequency the woofer is supposed to reproduce and the projectile is the woofer cone.

With a bomb, all the calculations are made in advance and once the aircraft releases the bomb - all we can do is cross our fingers that it hits the target. If the casing of the bomb has a dent on it, or if a big gust of wind comes, for many different reasons - that bomb might not hit the target.

With a guided missile (a servo system) - the missile itself is constantly relaying feedback to the propulsion system (the amplifier) so that no matter what variables might come up - it will hit its target every time (woofer precisely reproduces the signal).

In Brian's explanation, imagine adding another woofer into the box. This woofer will control the movement of the other woofer due to pressure. Nothing can be done about that by conventional means. In a subwoofer box, there is tremendous pressure - that pressure acts like another woofer and fights against the woofer.

With a servo controlled woofer, the movement of the woofer by those external forces (or any other forces) will be compensated for by sending a signal to the woofer to oppose those forces. It is important to keep in mind that a woofer in itself is a voltage source, push that woofer in and out with your hand and it will generate a current. Try it yourself, grab a flashlight bulb, connect it to the positive and negative of the woofer inputs and simply push that woofer cone back and forth and watch the light bulb. The speed and how far you push down on the woofer will directly affect the light given off. It is from this information (the feedback from the woofer movement) that Brian's works his match so that the woofer is properly tracking the signal, regardless of frequency.

[N Boros]

I have a 3-yr-old so drawn to down-firing.

Tai,

I'm a little confused by why you prefer a down-firing subwoofer. From what I understand any bass coming out of just about any subwoofer should be omnidirectional, which means that it shouldn't sound different if it is down-firing or not (unless you are crossing it over very high). I think that the orientation of the woofer is more of a design choice related possibly most to aesthetics than performance.

If you prefer a down facing driver so that the child doesn't possibly play with the woofer, then that does make sense. But, I can say that I have a 2 year old and 5 year old child and have had bookshelf speakers on stands for the entire time. My wife was really concerned about the speakers tipping over on them when they were first born, but it really isn't that big of an issue. We watched them closely at first making sure they know not to mess with them, and they quickly learned. It really isn't an issue now. I'm glad now that I didn't choose my speakers based on being able to wall mount them, just because I was worried about them tipping over on the kids.

[N Boros]

Dave, Curtis and Brian,

This discussion about how the servo technology in the Rythmik subwoofers work has been very helpful. I have a much better understanding now. I think that comparing what most other subwoofers do with simple DSP cannot be compared at all to what Rythmik is doing with the servo technology, as you have said. This would be like comparing the the old Ford Mustang from the late 60's to early 70's with the new Mustangs from 2004 until now. Starting in 2004 Ford decided to go back to the body style that so many loved in the muscle car era. During those early years the body styles were quite close. In both cars you could get the option of likely the Ford 302 engine, either an automatic or manual transmission and both were rear wheel drive. But, the similarities ended there. It isn't even a contest comparing the performance between the two cars. Fuel injection vs. carburetor in terms of performance and fuel economy, computer for engine and transmission vs. well... no computer, handling abilities vs. ability to go fast as long as it is in a straight line, Antilock 4 wheel disc brakes vs. maybe disc brakes on the front, bluetooth GPS integrated into a nice stereo head unit vs. AM/FM and maybe a clock, etc. If your only concern is the look of these two cars and going fast in a straight line then either would do that just fine, but if you are looking for performance past that then the two are quite different.


I used to be into restoring cars in improving their performance of them, but gave that up about 7 or 8 years ago. My old pickup truck that I was driving while restoring and was my only vehicle to get back and forth to work kept breaking down at very incontinent times and finally I had enough. If I was choosing which Mustang I would restore while driving, I would definitely choose the old classic one. The new one is far too complicated to work on for many things. But, if I had $30,000 to $40,000 and really liked the body style of that particular Mustang, I would definitely just get a new one. I think this is really similar to the DIY subwoofer community. I think if I spent some time and wanted to make a hobby out of it, I could put together a nice DIY subwoofer using DSP technology and it would sound pretty good after all that time and effort. Honestly though I am to the point where I would rather spend the extra money and not have to worry about fixing any quirks and troubleshooting things when I just want to sit down and listen to some music or enjoy a movie. Not only will the extra money buy me this ease of use where things should just work most of the time, but I think that if I go with a Rythmik I will be getting a big difference in performance as well.

[sludgeogre]

Tai,

I'm a little confused by why you prefer a down-firing subwoofer. From what I understand any bass coming out of just about any subwoofer should be omnidirectional, which means that it shouldn't sound different if it is down-firing or not (unless you are crossing it over very high). I think that the orientation of the woofer is more of a design choice related possibly most to aesthetics than performance.

Downfiring woofers have gravity acting on their forward/back motion. This is just another force that creates inaccuracies in the final signal. In front firing woofers, gravity is acting perpendicular to the woofer motion and does not effect woofer travel differently across the woofer's motion. In downfiring systems, it does. The pressure inside the box works against the cone as mentioned previously by Rythmik and Dave, but now you're adding complementary force to the woofer as it pushes forward, and impeding the motion as it draws back. This means you have to correct for more forces through servo or EQ.

Since we're on the topic, I'm not sure if a downfiring sub gives an advantage by using the floor as a re-radiating area, or by using the short distance between the cone and the floor as a way to increase air velocity of the wave as it leaves the woofer? This is what some speakers do that are vented on the under-side of the speaker, such as Zu's speakers. It makes sense to me, but I'm not sure how the physics of it actually end up in the real world.

[taigovinda]

N Boros, Alex,

Yes, consensus from what I've read in various places is that the two form factors are equivalent in sound or maybe side-firing is a bit better. My concern is indeed that my son likes to climb on my current sub and smash toys against it; also the look of down-firing could appear more like an end table and less like audio equipment, even by purchasing a stock one and adding veneer. The fact that the down-firing is not readily available does change things for me - guess I'll have to either train my kid or else pay about 2x.

For an 8000 sq ft room, would F15HP x 2 (non-vented) be right? In terms of output levels, I don't have a sense of how it would compare to what I have currently, the one vented Outlaw... or how it would compare to just one F15HP. I've read somewhere that output gain from adding identical subs is a lot less than going up a size, but I'm not sure that when the 18 does come out it would be the right form factor for me trying to be at end table height. The room is 33 x 15 x 16 (high point of sloped ceiling), the sub(s) would go against the side wall(s) close to halfway back in the room.

Thanks.
Tai

[sludgeogre]

N Boros, Alex,

Yes, consensus from what I've read in various places is that the two form factors are equivalent in sound or maybe side-firing is a bit better. My concern is indeed that my son likes to climb on my current sub and smash toys against it; also the look of down-firing could appear more like an end table and less like audio equipment, even by purchasing a stock one and adding veneer. The fact that the down-firing is not readily available does change things for me - guess I'll have to either train my kid or else pay about 2x.

For an 8000 sq ft room, would F15HP x 2 (non-vented) be right? In terms of output levels, I don't have a sense of how it would compare to what I have currently, the one vented Outlaw... or how it would compare to just one F15HP. I've read somewhere that output gain from adding identical subs is a lot less than going up a size, but I'm not sure that when the 18 does come out it would be the right form factor for me trying to be at end table height. The room is 33 x 15 x 16 (high point of sloped ceiling), the sub(s) would go against the side wall(s) close to halfway back in the room.

Thanks.
Tai

Indeed, totally support your decision based on your kid and your room, no problems there, just discussing the physics of it.

FWIW, I own two F12's in a pretty big open room and it gives SCARY amounts of bass when called for. I run them at about 1/3rd volume each, normally. I think that two F15HP's would totally rock your world.

Finally, the grilles that come with Rythmik subs are pretty beefy frames, so even if your kid is pawing at it, it'll give them a good amount of protection. SVS also has some models that have metal grilles on them for more protection, but they're small, overpriced, and not servo subs.

[N Boros]

N Boros, Alex,

Yes, consensus from what I've read in various places is that the two form factors are equivalent in sound or maybe side-firing is a bit better. My concern is indeed that my son likes to climb on my current sub and smash toys against it; also the look of down-firing could appear more like an end table and less like audio equipment, even by purchasing a stock one and adding veneer. The fact that the down-firing is not readily available does change things for me - guess I'll have to either train my kid or else pay about 2x.

For an 8000 sq ft room, would F15HP x 2 (non-vented) be right? In terms of output levels, I don't have a sense of how it would compare to what I have currently, the one vented Outlaw... or how it would compare to just one F15HP. I've read somewhere that output gain from adding identical subs is a lot less than going up a size, but I'm not sure that when the 18 does come out it would be the right form factor for me trying to be at end table height. The room is 33 x 15 x 16 (high point of sloped ceiling), the sub(s) would go against the side wall(s) close to halfway back in the room.

Thanks.
Tai

Tai,

You and I have a couple of things in common. I too own the Outlaw LFM-1 (though you have the "+") and it is in far too large of a room to properly do its job well. I am currently in a almost 10,000 cubic foot basement, since it is an open floor plan down there. I originally bought the subwoofer for my 12 by 16 foot living room in a small starter home. Even though the room was partially open to the rest of the house, it still did a wonderful job of pressurizing the space and adding an extra sense of realism when playing movies and music. That is no longer the case in this huge space. If I run sweeps I can technically hear the bass frequencies, but there is very little "feel" to the bass. Honestly, it is almost as if I don't have a subwoofer at all in this large space.

What I am planning to do is to put up a couple of walls in my finished basement to get the size of the space down smaller. This way I don't have to get such large outputting subwoofers and speakers to contend with the large space. But, if I were to leave it open I would be looking at the largest ported offerings from various manufacturers: Rythmik FV15Hp, or the new upcoming bigger models, JTR 1400, SVS PB 16 Ultra, HSU VTF-15H MK 2, Powersound Audio's ported offerings, etc. On this thread a large part of the discussion has been focused on the added performance benefits of the technology used in the Rythmik subs, so if you can fit it in your budget I think it is worth it. I know that I plan to go with a Rythmik to fit my room size when I save up the money.

[taigovinda]

Thanks Guys. I'm hearing one vote for 2xFV15HP and one for 2xF15HP. So I went and read like 20 other related threads across the web (some of which include more thoughts from N Boros :))... I'm leaning strongly towards the 2xF15HP because:

- concern: not enough output for 33Lx15Wx10-17H (sloped ceiling)

- subs will be relatively near field, against the walls directly to the sides of the main seating area, more perceived output
- music is at least 50%, from what I understand sealed is better for this
- sealed is "harder to screw up" in setup or "ported is harder to get right"
- sealed is smaller, especially in height... so I can set them on auralex pads and still not be too tall

Now I just have to save up the money and see if going in for horizon and surrounds at the same time makes it a better deal. I asked black or silver woofer and the wife said silver - I take that as authorization for the entire purchase!

Tai

[Mag_Neato]

........I asked black or silver woofer and the wife said silver - I take that as authorization for the entire purchase!

Tai

Sounds like a green light to me!!

[N Boros]

Thanks Guys. I'm hearing one vote for 2xFV15HP and one for 2xF15HP. So I went and read like 20 other related threads across the web (some of which include more thoughts from N Boros :))... I'm leaning strongly towards the 2xF15HP because:

- concern: not enough output for 33Lx15Wx10-17H (sloped ceiling)

- subs will be relatively near field, against the walls directly to the sides of the main seating area, more perceived output
- music is at least 50%, from what I understand sealed is better for this
- sealed is "harder to screw up" in setup or "ported is harder to get right"
- sealed is smaller, especially in height... so I can set them on auralex pads and still not be too tall

Now I just have to save up the money and see if going in for horizon and surrounds at the same time makes it a better deal. I asked black or silver woofer and the wife said silver - I take that as authorization for the entire purchase!

Tai

One resource that has been very helpful to me in my planning of my home theater is the AVRant podcast. A cohost of the podcast is Rob H, who goes by FirstReflect on this forum when he posts. For the past 2 or 3 years now their podcast has been focused on answering questions that folks like you write in and then they just give advise. I would take advantage beacuase it is free and they do give quite good advise. I don't always take the advise that they give, but just having a couple of knowledge guys talk about it can sometimes get me to think of an approach that I didn't think about before. To write in you just email rob@avrant and tom@avrant with your question and then usually on the next podcast or the one after that they will discuss it. Good luck with your decision.

[billy p]

Thanks Guys. I'm hearing one vote for 2xFV15HP and one for 2xF15HP. So I went and read like 20 other related threads across the web (some of which include more thoughts from N Boros :))... I'm leaning strongly towards the 2xF15HP because:

- concern: not enough output for 33Lx15Wx10-17H (sloped ceiling)

- subs will be relatively near field, against the walls directly to the sides of the main seating area, more perceived output
- music is at least 50%, from what I understand sealed is better for this
- sealed is "harder to screw up" in setup or "ported is harder to get right"
- sealed is smaller, especially in height... so I can set them on auralex pads and still not be too tall

Now I just have to save up the money and see if going in for horizon and surrounds at the same time makes it a better deal. I asked black or silver woofer and the wife said silver - I take that as authorization for the entire purchase!

Tai


Obviously...you have some easy choices and some more difficult one's along the way. IMO that room is huge and I would look into the vented vs. sealed...for that large of a space. Room interaction & placement will determine the difficulty of setting up, not sub design. General rule of thumb larger rooms with adjoining spaces go with vented, smaller or sealed rooms tend to benefit more from a sealed.

I like AVS....it has a extensive information base if researched thoroughly, plenty of knowledgeable members...thou...you must sort through some of the biases and bickering from time to time...usually found in comparison or owners threads. Check Data-Bass for third party objective analysis of comparable subs...

Several different subs you may consider... that would fit your needs but if your considering Rythmik Audio first and foremost... talk to them directly have them guide you...your room/or space, budget, listening levels and habits...etc...should determine what you chose...I doubt the F15hp will vary much in SQ vs the FV15hp....:)

Good luck,


Bill

[sludgeogre]

Thanks Guys. I'm hearing one vote for 2xFV15HP and one for 2xF15HP. So I went and read like 20 other related threads across the web (some of which include more thoughts from N Boros :))... I'm leaning strongly towards the 2xF15HP because:

- concern: not enough output for 33Lx15Wx10-17H (sloped ceiling)

- subs will be relatively near field, against the walls directly to the sides of the main seating area, more perceived output
- music is at least 50%, from what I understand sealed is better for this
- sealed is "harder to screw up" in setup or "ported is harder to get right"
- sealed is smaller, especially in height... so I can set them on auralex pads and still not be too tall

Now I just have to save up the money and see if going in for horizon and surrounds at the same time makes it a better deal. I asked black or silver woofer and the wife said silver - I take that as authorization for the entire purchase!

Tai

I know a lot of people will push you to go with ported subs, but I'm voting that you don't need to, and that your plan is great. Like I said, with my dual F12's in a huge open space, they run at 1/3rd volume and I STILL ask my girlfriend to turn it down all the time at night. Two F12's is roughly equal in output at 20 Hz to one of the 15 inch vented models I believe, but I can't find where I read that. Two of the 15 inch sealed subs would likely have greater output than one of their biggest vented subs. The added bonus is that sealed subs have extension all the way down to 5 Hz whereas even the mighty FV15HP goes down to about 13 Hz at -10 dB. I don't know if I could really even tell a difference between the extension if I heard both subs back to back, but I can tell you that the deep bass capabilities of even the F12 are just frightening. I usually don't run them in that mode because it is pretty distracting having that on in the main room. I cannot wait to move into my new house with my dedicated theater. 41 more days.....

[N Boros]

Here is a photo of the prototype subwoofer which is being called the FV25HP in post 23826:

http://www.avsforum.com/forum/113-subwoofers-bass-transducers/1214550-official-rythmik-audio-subwoofer-thread-795.html

I agree with Billy P's suggestion of using AVS as a resource, but as this thread I am linking to illustrates, threads over there get so massive that they can sometimes feel overwhelming. I've been trying to follow the Rythmik thread since spring to see if I could find out any news for the upcoming FV25Hp and the FV18 subwoofers and it is nearly impossible. Many days there will be several new pages full of posts added. I just don't have this much time per day to set aside to even follow this one thread on AVS.

[taigovinda]

Thanks everyone for all the continued input. Two things are definitive for my sub upgrade, the green light and Rythmik. So the forums have narrowed things down tremendously for me.

F25 is a possibility for me, seems likely right now. I've got a question series out to Rythmik and a question out to Salk now... I'll be back later to ask more here or to update on what advice I got and which direction I went at that green light :)

Tai

[enricoclaudio]

Here they are: FV25HP and FV18 final prototypes going into full production. I will post more info and specifications as soon I get green light from Brian!!

1374

1375

[rsmt2000]

Here they are: FV25HP and FV18 final prototypes going into full production. I will post more info and specifications as soon I get green light from Brian!!

1374

1375

http://forum.ascendacoustics.com/attachment.php?attachmentid=1264&d=1455147176

Funny can't help but notice how ascend and rythmik are going opposite directions 😀

[N Boros]

DSP is not comparable to servo. DSP is one method (actually, a lesser expensive method these days) for equalizing / contouring the subwoofer's response as opposed to equalizing by analog means. It means the LFE signal that is being sent to the sub is once again converted to digital - then various filters are applied to the digital signal, and then it is once again converted to analog so it can be amplified and then sent to the woofer.

Regardless of how good the DAC's are - each time an analog signal is converted to digital and then back again, information is lost.

Servo is a real time solution whereby the woofer sends a continuous signal back to the amplifier, so that the amplifier makes sure the woofer is properly tracking the signal being sent to it.

DSP does not have any effect on overall sound quality other than adding additional features and a simpler way of implementing eq. In fact, because of the additional A/D D/A conversions, it has a negative effect on the purity of the original signal being sent. These days, there are way to many A/D D/A conversions taking place in the audio chain. DSP in a sub would be more beneficial if the LFE output itself were digital.

I'll take servo any day of the week when it comes to sound quality in a subwoofer.

Dave,

I'm a little confused about what you are saying here. Are you saying that Rythmik subs don't do a D/A conversion? Or that they can be configured where they are not doing a D/A conversion?

I know that there are PEQ knobs on back, so are those working in the analog domain?

[N Boros]

The new Rythmik subs have been measured by Josh Ricci on data-bass.com:

F18: http://data-bass.com/data?page=system&id=145
FV18: http://data-bass.com/data?page=system&id=146
FV25: http://data-bass.com/data?page=system&id=147

Also, the FV18 was reviewed by JMan at HomeTheaterShack, for a much more subjective write-up.

http://www.hometheatershack.com/forums/speaker-subwoofer-reviews/171498-rythmik-fv18-subwoofer-review.html

[kdaq]

Anyone spend some time with an F18? I'm curious how it compares to other Rythmiks.