Official Rythmik Audio Subwoofer thread - Page 106

I love what you said here... this really is the bottomline in the whole discussion of controls.

+1 on the SMS-1.
Even if you don't have to do much EQing the SMS-1 is hella tool to have.
For me, it made things so much easier with my pair of other brand subs.

Curious: Is the Velodyne unit better than the cheaper Behringer units, except for ease of use? (Not that more user-friendliness, or at least less user-hostility, is not a big deal!) How about compared to the Antimode unit?

imho, it's far better than ones that you have accept what they give you.
I haven't used the others, I know I want to make my own adjustments however.

YMMV.

They can measure room decay (e.g. RT60) but that's unrelated to Rythmik damping. In any case for "small" (e.g. a home theatre) rooms there's evidence that suggests decay is of questionable value.

Then how would you measure the damping adjustment and its effect in room?

Well, I agree to an extent, but as of now I would be almost blindy flipping switches since I dont fully understand the INTENDED effects. I am fully aware that the room characteristics will play a vital role, but you need to know what each control was intended to change, otherwise it is quite simply a crap shoot.

So again, I revert to my original post. Looking forward to what Brian might have to say as well.

This posting is really meant for Brian and so I should probably do it in a PM to him rather than open posting but on the off chance that my questions and Brian's response might prove helpful to others, here goes...

Brian, amid this recent discussion of Rythmik controls and how they directly affect the sub's output response, I've come to doubt my own feeble understanding of how your direct-servo functions. I'm not an electronics guy at all, near zero formal training however I do understand the basic principles of servo-controls as they relate to closed-looped servo-controlled hydraulic circuits and even closed-loop temperature control circuits... how closely related is your implementation of direct-servo control of the driver?

In hydraulics a pressure transducer and a linear potentiometer are the sensors required to monitor and send back information to the control circuit (and a thermal couple for temperature control loops). I have been thinking that the 'extra' wire wound around the voice coil is very similar to a linear potentiometer in that it monitors cone position (actually movement) and provides the needed info on acceleration. However where the potentiometer uses the voltage (resistance wire of the coil) to relay positional information, your circuit is using the current generated in the wire due to its movement in a magnetic field for the acceleration info? correct?

In closed-looped hydraulic and temperature control circuits the sensor feedback loop is compared and summed to the setting profile (original signal) and the difference is acted upon by subsequent circuitry. Typically there are three commonly use circuits that contribute to proper 'tuning' of the system output.

Proportional is used to adjust the size of the proportional band width. This is set to prevent constant oscillation around the set-point (original signal).

Because each component in the system has its own resonant value determined when it was sized by the designer, when the setting (signal) is other than the component's own resonant value the actual settling point will be off-set (hysteresis) from the (desired) setting. Integral (reset) is the circuit that compensates for the off-set by appropriately shifting the whole proportional band according to the degree of off-set reported from the monitoring sensor.

Finally, process upsets will always lead to over-shoot on the correction. Derivative (rate) is an anticipatory function that monitors approach to set-point (original signal) and dampens the approach so as not to over-shoot with a rippling effect (ringing). Too little damping and response will take too long to settle down (excessive ringing), too much damping will lead to taking too long to achieve set-point IOWs slow reaction times leading to inaccuracies in reproducing the original profile (signal).

What I've described above is a typical full PID tuning of a closed-looped control circuit as I know it.

The real questions from me is how much of this applies to the way you are implementing direct-servo in your subs? Is damping (derivative) exactly the same in terms of the way your circuits are treating it? or is there some other 'audio' specific meaning which has nothing to do with taming the overshoot oscillations on any process upsets? Is the damping as you've implemented it directly intended to 'shape' the response curve or is it merely a by-product of the circuit tuning (perhaps due to a limiting driver excursion)?

I recommend the SMS-1 too. Also makes it easy to optimize the phase. Just turn the phase knob and watch the display for changes around the XO freq.

As easy as that.

Dave.

I suggest you start with the tech section on the Rythmik site to get an understanding of what DEQ is doing. I'd guess that for most people in most rooms the effects are too subtle to notice.

Not to sound like a broken record but have you read the Rythmik tech papers? I think they answer all your questions.

IDK, seems relatively straightforward, The frequency controls how deep or low the sub plays. Highest lets it play louder because it's harder to play those lower frequencies. Beyond the question of whether you just want the loduest it can be, the right setting will depend on your room gain and personal taste. Nobody can tell you precisely what your room gain is at any frequency, but you probably can pretty quickly figure out if you're getting overwhelmed at the low end with a lower extension setting.

Damping controls ringing. Ringing is the tendency of a device (like a sub driver) to continue to move after you stop applying a signal to it. It's kind of a spring, after all, so left to its own devices the driver will ring a bit. Using a sealed enclosure reduces ringing by putting air pressure behind the driver to fight the tendency to continue to flap after the signal stops. The damping settings essentially let you control the amount of flap. Based on simply reading the Rythmik website, it appears that lower damping (higher ringing) will allow higher ultimate SPL. A

fter that, it becomes, I think, a question of what simply sounds best in your room. My bias would be deepest extension, highest damping, because that should theoretically get me the most accurate sound from the sub. But if my room gain is too much below 20 Hz, I may try middle extension to get things under control. If I find I seem to be losing oomph on the loudest parts, I might try a higher damping setting to compensate.

Whether and to what extent the damping settings are audible and matter to you depends, I think, on your room, your ears, your experience, and your expectations. Although ringing is technically "wrong," I think, it can be at low enough levels to not matter. Plus, the real world things that get recorded (like a bass guitar or even an upright bass) are made of actual physical materials, not theoretical concepts, and they ring (resonate, sustain) too. So a little sub ringing may sound pretty natural to your ears, as it kind of adds to the instrument's (or noise's) natural "dropoff."

I have tried the damping controls in two different rooms....it was easily noticeable in those situations....especially between the high and low damping settings.

Damping controls ringing, and ringing can be shown in decay measurements, correct?

Do you have a Rythmik sub? If so, have you tried the different adjustments?

I think so. The question then becomes, in part, whether the ringing of the speaker is audibly swamped by the "ringing" of the room . . .

Agreed....but the ringing of the speaker can/will also be transferred to the room.

It's fixed! It seems that just about all avr's have an internal muting function that activates for a millisecond whenever inputs are changed or when programming fed into that input changes(ie:changing channels on tv). That's what failed on my 8 year old Yamaha. So, after buying a new avr,I am poorer but happier! Thanks for your help!!

I've read what he has written on the Rythmik website, don't know if that is what you are referring to but unfortunately it doesn't answer my questions... which is why I bothered to ask them in the first place. However, if you have managed to somehow divine the answers from what you've read please by all means offer up your own response, I'm interested in understanding how damping is being implemented.

Cool..... That discussion is pretty intense. I had a flashback: I'm feeling like at Thermodynamics II Classroom 20 years ago, I mean, did not understand anything but I liked it.

Just as some background, I do a two-hour lecture on the tuning of closed-loop servo-controls in a manufacturing class I teach... for the last 24 years! Its not quite as complex as it sounds, it only looks that way if I have to write it all out in one short posting. Believe me, if you'd sat through my powerpoint presentation it would be very clear to you and I'm sure no where near as cryptic and difficult as your Thermodynamics class years ago must have been.

Because of these recent discussions here, especially about damping, I'm just curious as to if my information is relevant to Brian's implementation of his particular servo-design... I'd just been naturally assuming it was until recently and now I'm feeling some doubt so now I'm thinking I'd better be sure before I am caught spreading any heresy.

monomer,

As an engineer, I have to say that your explanation is at the level of the best teachers I had for 7 years in University. Maybe it's not 100% right (only Brian can confirm that), but it was EXCELLENT explained and detailed.

Please, if you can send me that powerpoint presentation.

I certainly support the idea of knowing versus speculating. If the answers are of general interest perhaps then can find their way to the tech section.

This link might answer some questions regarding the Rythmik controls. http://rythmikaudio.com/amplifiers_controls.html

Brian, are you going to be getting the 600W plate amps in the next month or so? I'm interested in your F25 DIY kit. I also see that the drivers are being used in front firing configuration, can the drivers also be used in a dual opposed set-up?

Also, are you working in putting together a more powerful sub than the F25? Say a 1,000-1,200W plate amp with the DS1510 drivers? If so, when will it be available both in commercial and DIY form? That's probably another 3-4db's over the F25 to go along with its great SQ.

A sub like that would make for a great choice for people like me with only a one sub solution in a big room looking for the most bass and SQ quality, specially considering your very competitive prices. I'm lucky that when the sub in my room is placed in a corner, I get very good room gain down low to go along with a good bass response.

I've noticed that Rythmik has had a problem keeping things stocked. Is there a specific reason that nearly all of the products are constantly on backorder? Is it a part issue or labor issue? Is it from underestimating sales or suppliers not being able to meet demand? I have a feeling that you may be losing sales because of this. Which is unfortunate.

The naming of this device is misleading. It is no more a servo than is a speaker with negative or positive current feedback. In fact the patent on this device more or less describes it as a variant of the Audio Pro ACE bass principle which was never described as a servo with degenerative feedback. So all of those procedures you used to tune a closed loop control system do not apply to this device.

hope that helps

regards
benny

Yes that does help... it answers one of my most basic questions, however I'm still left wondering how the damping is being effected/controlled in his implementation. Any ideas?

I guess the bottomline here is, regardless of the choice of using the name 'servo' or how he's got feedback implemented, there's not doubt about the results in sound... it can definitely sound very real.

Who else is waiting for Rythmik to receive their next shipment to re-stock CI components? I want to build two sealed enclosures and install the 1510 driver and 550 PEQ amp. Around the first of March it was about 6 weeks out, and then on 3/23 Enrico sends me an email stating 'it could be available in 6 weeks'.

I'm a pretty patient guy but waiting two months before I can start the build is stretching it thin. Has anyone heard anything different on delivery. One forumite said that the 550 amps were currently available. Are the drivers the hold up?

Blues

Brian and Steve Jobs have the same problem -- a hot product with demand outstripping supply.

In Brian's case, it was a double-whammy with a concurrent positive review by Audioholics and a favorable comparison with other subs in the recent AVS shoot out. This is what convinced me to buy Rythmik.

It was a major hassle to get my FV15 HP because of all the confusion about product availability, but in hindsight it was well worth the wait.

I would be more concerned if no one else wanted to buy Rythmik.

Does Ascend have the same issues? Enrico made it sound like an Ascend order would come from California which would suggest they were a stocking distributor and not just taking orders for drop shipment from Austin.

It's obviously a demand issue...but why are they unable to keep up with the demand? This was a problem long before the reviews. I know they sell a lot, but they are also on backorder over 50% of the time. It leads me to believe that they either have a part shortage, labor issue, or forecasting issue.

This is not a slight of Brian. I hope this business makes him rich. I work in the manufacturing industry and know how lead times can impact sales. If his vendors are unable to keep up with his demand, there is little he can do without switching suppliers. Forecasting and labor issues are easier to fix.