What subwoofers have servos? - Page 3

Sorry no cigar for that chart. You did it at 70 Hz where cone excursion is small and power would be low !! What's the point of that ? It's when the driver is pushed to its limits is where you need the servo the most and that means low frequencies and high power !!

I'll wait for the tests of the sealed box version to appear in home theater but I note they have never done a review on ryhthmik. I wonder why ?

Also the power compression over time due to voice coil heating is not going to be nowhere near as objectionable as distortion caused by non linearities in the motor system.

But don't get me wrong. After all of the negatives I have said regarding this device if you read the patent on this invention you will find that rythmik has taken an original invention from the 80's and improved upon it, the main benefit of it being it's immunity to changes in voice coil resistance. But the original device was never referred to as a servo system. It's because rythmik modifies the design by the use of velocity feedback is where the 'servo' terminology has crept in even though the behaviour is more similar to that of the original invention and not to a traditional servo based system. And because the sense coil shares the same magnetic circuit as that of the main driving coil it is plagued with all of its problems as well and no quick fixes !

This is my last post.
http://www.avsforum.com/avs-vb/showp...&postcount=194

Still finding excuses not to do those tests properly

Look at it like this. If a negative feedback servo in a speaker was as easy to implement as it is in amplifiers then every sealed box subwoofer would probably have one along with all of the benefits that it provides to amplifier design Distortion would be much lower and bandwidth would be extended and flattened and transient response would also be improved. All of the other limitations that plagued open loop designs such as voice coil heating would also be eliminated or minimized. Differences in distortion in a room environment would be a lesser of an issue just as they are with low THD amplifiers simply because if a servo design had minimized it in the first place then the coloration of the room would not have that much effect on it.

Once we had solved these problems with a servo design then other issues which were always an issue such as cone integrity and flexing would now have to be addressed as the more dominant source of problems.

Has this turned into a "servo is nothing but marketing crap" thread? I've tried to read into it but it's not easy. I will say this. I've had a lot of subs including two different Rythmik subs. One ported the other sealed. I don't think the servo tech is marketing. It makes a difference IMO. That's all I'm adding cuz it seems like one party isn't looking for a discussion, just an argument. Out.

Benny has been after Brian about his direct-servo Rythmik subs since his very first post on AVS... it was in a response to a posting I made directed to Brian asking about particulars of his direct-servo implementation. The bottom line is Benny doesn't think Brian's implementation of his 'direct servo' qualifies as a bonafied servo circuit because it lacks a mechanical transducer of some sort as its sensor... however this is Benny's own interpretation of what a "real" servo system should be. (Here I just thought you needed a path for feed back from a sensor, a control circuit and a driver... as far as I'm concerned Brian's subs meet these requirements.) Quite a while back I came across a couple patents on what appeared to be circuits similar to Brian's direct servo (apparently one of these patents is what Benny referred to a few postings above) and apparently Sony did implement one of those patents calling the sub a "servo" at some point... I posted about this find in a thread where someone was asking about Sony's servo sub (its what prompted my Internet patent search in the first place). I'm not an EE, (though I am actually an Engineer in another discipline), so I don't really understand how Brian's patent differs in its technical merits, but apparently it does since he was granted a patent on it and he hasn't been sued.

The 'discussion' here (and elsewhere where Benny keeps bringing up Rythmik's direct-servo implementation) is essentially about types of distortions and which are worse and what values are going to be audible, etc. This type of esoteric rhetoric I find mind numbing and quite frankly useless especially in light of the fact that Benny has never even listened to a Rythmik. He is all about the theoretical discussion and not about relating it back to any actual experience. So when he actually has the chance to listen to a properly set-up and integrated Rythmik sub and to critically evaluate it with familiar source material, ONLY THEN will his theoretical remarks begin to have any real value and weight... until then it begins to just sound like a lot of blah, blah, blah, Rythmik is not a servo sub, blah, blah, blah, Brian is a huckster blah, blah, blah, Rythmik subs are full of distortion, blah, blah, blah, I like Velodynes... 80+% of all his 64 postings here on AVS has been specifically dedicated to 'exposing Brian and the terrible subs he designs'.

Benny, either go and actually experience a Rythmik or give it a rest...

amen to that.....

+1

I'm not after anyone except the truth. It is not my fault that one of his disciples can't help himself that he has to keep replying to my posts. I'd rather he didn't actually and stop trying to spread propaganda. There is already one thread allocated for that.

In case you hadn't read the start of this thread it is about servo feedback subwoofers other than rythmik (which is a misnomer if I'd ever seen one.) Maybe the problem is that I am not a member of the flat earth society that accepts everything that is spoon fed to them without question.

If you studied the patent of this device (6104817) you will realise that it is just an improvement on the original device invented by a swedish company in the 80's. In fact his patent sites this original swedish patent which is probably why he doesn't want you to read it !! It was never a servo design in the traditional sense. The whole thing is just a play on words and the ignorant amongst you doesn't want to question it nor do you want anyone else to question it.

If you are to sensitive for intelligent debate and seeking out the truth then perhaps you should just go away and pat each other on the back and tell each other how good a purchase you have made and just leave it at that. Nobody is denying you the right to be happy in your purchase

then go away and tell your mate to stop parroting the rythmic line. The dude who started this thread just wants to talk about any servo subwoofers apart from rythmik and now you want to hijack this thread and turn it into an "I love brian fan club" !!