What subwoofers have servos? - Page 2

Originally Posted by benny blanko

why wouldn't a servo speaker such as the velodyne have immunity to changes in voice coil resistance and why is this such an issue anyway ?

Originally Posted by benny blanko

Since you are very good at telling me what I posted in the past why don't you ask your good mate why he deleted posts of mine and then barred me from posting on his thread (that someone else started anyway) when I highlighted the error in his reasoning which as I recall went something like this :-

"Even a 100% increase in voice coil resistance would only result in a 3dB drop in output which is hardly noticeable.... !!"

Your good mate said it was 6dB which is point blank WRONG !! Then he made some personal snide remark aimed at myself as to why I was wrong when I wasn't !! He should go back to school for making that error !! It even gets worse for his case because if you enclose the speaker in a feedback loop with a relatively high loop gain such as the velodyne then that drop in output will now be totally negligible simply because negative feedback desensitizes the closed loop transfer function to changes in parameter variations so again your claims are highly exaggerated as most of the rythmik claims are !!

Originally Posted by benny blanko

And you talk about measurements !! What is so good about those measurements on hometheater shack ? There are plenty of non 'servo' speakers that exceed such a mediocre objective performance.

And you are entitled to your subjective opinions. Nobody is denying you that at least not me. Plenty of people will have good and bad stories about other subs including velodyne

Originally Posted by benny blanko

I suggest that you focus on expounding the virtues of your own design rather than nit picking at insignificant limitations of other designs. But when most of your claims are highly exaggerated then what is there to talk about ?

Originally Posted by HuskerOmaha

Whoever this kwarny guy is he is wayyyyyyyyyy too smart regarding this topic.

Originally Posted by kwarny

The velodynes did not show immunity when tested.



The moderators delete posts.

Can you show me your measurements that it is only 3 dB when the voice coil resistance is doubled? Also while you are using the oscilliscope, can you show me your measurements that the reduction of nonlinear distortion is equal to the amount of loop gain when using a driver? It does not need to be motor using differential drive.




Show me some other 12" non servo subs that exceeds it and please discuss how it exceeds the diy rythmik. Also, where are all those negative aspects you describe in the measurements.



I have never created my own servo design before and probably never will throughout my lifetime. Please show me yours?

I asked for you to explain and show the advantages of accelerometer subs. I explained the advantages of Rythmik servo over the non-servo counterpart. The frequency response shows the linear distortion. A decrease in linearity affects the time domain. Impulse, GD, and CSD are other ways to look at the frequency response. If the speaker behaves well in the time domain, wouldn't the nonlinear distortion also be shorter in the time domain? If the fundamental shows side band energy, wouldn't that affect the time domain also?

I also never exaggerated. I think the majority of us still don't know perfectly what correlates to what we hear. I never said the velodyne has major flaws. Perhaps I will enjoy it more when I hear it side by side to the rythmik or any other sub. If so and I have the available EDIT-[funds], I would pick up a few if I felt it was worth it. I feel that even the cheapest subs have a place in situations. Sure there may be engineering flaws and listening imperfections but the sub could still have a place.

If the speaker behaves well in the time domain, wouldn't the nonlinear distortion also be shorter in the time domain? If the fundamental shows side band energy, wouldn't that affect the time domain also?

Originally Posted by benny blanko

The moderators shouldn't be deleting posts that state fact. I never made personal attacks against the dude as he did to me but the posts were deleted simply because I showed up an obvious error in his thinking.

Anyway power = V^2/R

From that formula if you double the resistance you half the power and hence a 3 dB drop in power !! Even the reference efficiency equation from Small includes Re in the denominator. Same deal !!

Originally Posted by benny blanko

As for the comparisons between other subs you must be blind not to be able to see some better results !!

Originally Posted by benny blanko

I don't know what you mean by "nonlinear distortion also be shorter in the time domain". If you are referring to transient response then a servo and non-servo speaker will show IDENTICAL transient response if they both exhibit the same small signal high pass system response !! For example a non-servo sealed box with a cutoff frequency of 20Hz will exhibit the same transient response as a servo version with the same cutoff frequency so the advantages of the servo system is not to be seen for small signal.

Similarly for distortion, the non-servo system will exhibit fairly low distortion for small signals and the servo-d version will have even less distortion. It's the large signal response where the servo should exhibit its most benefit in cleaning up the signal provided the feedback signal from the sensor maintains integrity. Since the accelerometer servo is not effected by the magnetic circuit of the main driving coil this system will have the most benefit. The only way the voice coil servo can compete with the accelerometer servo is if the sense coil is mounted in a separate magnetic circuit to the main driving coil as this patent attempts to do.

Originally Posted by kwarny

Maybe correct using the equation. I am not a mathematician so I don't know if I should even try the equation . I only have a math minor I completed 5 years ago so I bet basic algebra is hard by now. Power compression can still be up to to 6 dB.



The times I cannot do my testing blind, I also try to level match and compare and then also give the advantage to both to whatever I am testing. I also try single blind with others. You are still welcome to attend some blind group sessions cause we both know that knowledge can create biases whether these are conscious or not. I only bought my kit cause my friend said he would help build the enclosure and it was easier on the wallet than SVS and Hsu. I am open to buy new multiple new references. There are reasons I attend GTG and go to stores. There are other rooms where the other equipment can go. What happens when you have a huge bias anticipating a favored product on the forum hoping it will sound so similar it is insignificant to the speaker/sub you own but while also being able to produce much more output and then it disappoints you on the first clip?




At a frequency there will be non-linear components such as harmonic distortion and intermodulation distortion. The time domain is dependent on the phase, amplitude of the frequency. So depending on the q, it will determine how long it takes the transient to settle at the affected frequencies. So do the non-linear components decay at the same rate as the fundamental?

If the main benefit of accelerometer servo is eliminating non-linear distortion when the sub is stressed more, I am with the other guys now. Maybe great for single sub systems but since I have space, I would rather buy 8 drivers and use DSP. All theoretical benefits of course. Maybe we use different accelerometers in my program (not engineering) but these are quite expensive; greater than $300 USD.

Can't wait to see your discussion of the diy 12" rythmik sub and another non-servo sealed 12" sub taken from the same measurer. Also don't forget to point out all the mutual coupling drawbacks in the third party measurements. Can you give me a time frame for the loop gain experiment using a driver?

Originally Posted by benny blanko

]

Now you are being absurd. The power compression will still exist on your rythmik subwoofer or any other subwoofer for that matter unless you have infinite reserves of power to compensate for rising voice coil resistance with temperature !! A servo loop will just compensate for changing voice coil resistance by forcing more power into the speaker until the amplifier clips in which case it will no longer have any control. A current output amplifier will have the same effect.

Decent accelerometers can be had for around $35 over the counter

And when doing subjective testing try doing double blind testing using statistical inferences to draw conclusions so in that way you eliminate any preconceived biases.

Originally Posted by benny blanko

Originally Posted by benny blanko

"Even a 100% increase in voice coil resistance would only result in a 3dB drop in output which is hardly noticeable.... !!"

Your good mate said it was 6dB which is point blank WRONG !! Then he made some personal snide remark aimed at myself as to why I was wrong when I wasn't !! He should go back to school for making that error !! It even gets worse for his case because if you enclose the speaker in a feedback loop with a relatively high loop gain such as the velodyne then that drop in output will now be totally negligible simply because negative feedback desensitizes the closed loop transfer function to changes in parameter variations so again your claims are highly exaggerated as most of the rythmik claims are !!

Originally Posted by Rythmik

You flunked the EE circuit theory course. The current is cut in half because the R is now doubled. Since in speakers, the force is BL*I. So the max force is also cut in half. Now you only have half of the force and can move only half of the excursion. How many db change is that? Let us get another EE background memeber chime in.

Originally Posted by Rythmik

You flunked the EE circuit theory course. The current is cut in half because the R is now doubled. Since in speakers, the force is BL*I. So the max force is also cut in half. Now you only have half of the force and can move only half of the excursion. How many db change is that? Let us get another EE background memeber chime in.

Originally Posted by Rythmik

Benny, let me ask a simple question. Your referenced patent has expired. Can you spend some effort and make a product out of it. Or even better, tell me which company uses a circuit structure like that and still in production.

Originally Posted by kwarny

I have always said the direct servo compensates until the amp runs out of reserves. Brian and JBL both state that power compression up to 6 dB.

http://www.jblpro.com/pages/general_faq.htm
http://www.rythmikaudio.com/memory.html

Forget the loop gain. Can you do a breakdown of a 12" sealed sub that Ilkka tested that bests the DIY rythmik measurements? and can you point out all the drawbacks of the mutual coupling in the measurements?

It is not always possible to do double blind testing in a hobby.

Originally Posted by benny blanko

why should I do that. You are the one who boasts about the technology so it is up to you to explain the benefits in relation to the test results. Please do

Originally Posted by benny blanko

Yes you are right. I take that back and eat humble pie.

So the situation is even worse than I originally estimated because you are going to need more amplifier power to compensate for thermal compression and no servo circuit can compensate for lack of amplifier power !!

No need to get posts deleted now is there

Originally Posted by Rythmik

You need a lot of that.



What is there for you to celebrate? The problem I have is just the same problem your Velodyne servo has to deal with, or any other nonservo subs.

Originally Posted by kwarny

Not sure I would say boast but I do talk about it positively in the owner's thread. I don't jump in every thread saying this is the only sub you should get. I'm sure the non-servo version of this driver also sounds nice. Another local has a Dayton Reference driver that I also think has potential. The OP was looking for me to post a summary through our PMs. I was only planning on those two posts and you filling in the benefits of accelerometer based servo since I admitted I was ignorant of the technology. You disputed the claims and state this form of servo has major limitations and also state the sealed 12" measurements are mediocre but have not shown these claims in practice.

Is your youtube name rentabomb?
http://www.youtube.com/watch?v=Af5K1OcJut0

Originally Posted by benny blanko

not me but you can see others questioning the benefits and so they should. Maybe ask yourself why no one else really adopts this type of servo feedback system ? Why didn't Genesis, Infinity, Paradigm, Velodyne and Phillips etc use a voice coil sensor instead of an accelerometer ? Surely it would have been easier and cheaper

And why not step up to the plate and do the some steady state power testing with simple sinewaves. Lets see the distortion reduction ability of this compared to other subs in a sealed box Simple tests that can be done cheaply with a sound card and a mic If it's as good as you say it should show up in the testing

Originally Posted by benny blanko

but it's not the only problem is it !! You seem to create problems that are not major issues and then proceed to swat the competition around the ears for not dealing with it just because you do !!

And to set the record straight I don't own a velodyne nor do I have any vested interests with the company so I have nothing to gain by talking about it or any other technology.

Originally Posted by Rythmik

This is much closer to the so called the time-invariant linear system.

You need to stop just reading the papers and start doing hands-on work. You defintely read more papers than most on the forum. But you need to find new direction. Otherwise, you are just being boxed in by those papers.

Originally Posted by kwarny

Still about max output and total harmonic distortion being a great indication of a quality sub ? Guess this is the AVS forum . Ask Mark Seaton or Bossobass what they think about of in-room harmonic distortion measurements?

Originally Posted by benny blanko

You talk about linear time invariance and all you have shown is the result of driving a speaker with an amplifier with a high output impedance which approximates current drive. Sure with current drive the voice coil resistance gets taken out of the equation and it compensates for rising voice coil resistance. Nothing new here. But the droop in output over a period of seconds is not going to be that objectionable compared to distortion of the actual signal. You just make it an issue whilst choosing to ignore the other obvious problems.

Also am I missing something. How much dB droop is that first chart showing ? It doesn't look like much at all !! In fact it looks like a droop of 10% or barely 1dB !!

Now reduce the time base of your measurements and lets have a look at the detail of what you actually hear which is much more important Lets see how linear time invariant your system is at cleaning up distortion especially at high power ? I don't see any of these measurements on your website.

Originally Posted by benny blanko

Jee's nearly every amplifier maker specifies harmonic and intermodulation distortion and tries to reduce it as much as they can so they must be wrong as well

Originally Posted by kwarny

Have you compared the time-invariant system directly to the time-variant version?



Perhaps amplifiers would be a better fit for your expertise even though Frank Van Alstine thoughts may differ on what measurements are important and how these are measured.

Originally Posted by benny blanko

I've been to a few night clubs where the time variance of my ears tended to mask out the time variance of the speakers Besides I've never heard any reviewer talk about time invariance !! Have you ?

But am I wrong about that chart ? A 1 dB drop over 6 seconds which is barely audible !! I think I was being pessimistic originally when I said a 100% increase in voice coil resistance

And if someone offered to sell you an amplifier with 10-20% THD and IMD would you buy it ?? Somehow if it's a speaker with a lot of distortion then you are supposed to pretend that it doesn't exist by ignoring it or focusing on other issues which are not significant like time in-variance !!

Originally Posted by kwarny

One of the sub reviewers said when referring to some time variance measurements.

Sure but there is now side band energy on the fundamental. The brain also filters out the majority of sound in the environment. It tends to focus on the information that varies in time. So could it be plausible that if the delayed energy (reverb track) is different than the main track for it that the perception may increase?

Depends how this number was measured. It may include amp clipping for all I know. Even if it was an amp that measured perfect, I would still rather invest the money into drivers since these contain moving parts or invest it into room treatment depending on the layout and speakers. Have you taken the Klippel tests and determined what levels of nonlinear distortion affect your perception? This level and importance of level will vary by person.

Originally Posted by benny blanko

But sideband energy from intermodulation distortion is not an issue ?

How come ?

Intermodulation distortion is one of the most common tests done on audio equipment but if you are only interested in the lesser of two evils such as time invariance and NOT linearity then I suppose you would not be willing to do these fundamental tests. These are objective tests designed to test the effectiveness of the equipment at doing its job especially something that claims to be a servo feedback system.

Originally Posted by kwarny

Side-band energy on the non-linear distortion spectral components? Take the klippel tests and figure out what level of non-linear distortion really is that offensive. These are not the sort of sounds I hear when it comes to inaccuracy. Building some speakers for the annual parts-express diy speaker design competition would be a good place to test this out for you also.

Now coming out of retirement and stepping up to the plate for the slowest game on earth...... I'm not sure if I should type this left handed or right handed . From the listening position with calibrated mic and audio interface response (not pocket change).

Originally Posted by benny blanko

So a 1dB drop in output over 6 seconds is totally objectional to you but spectral artifacts aren't ??

Now do the tests with a sealed box and without room gain and at a much lower frequency like these which I assume are ground plane measurements. If your mic can handle the SPL you can do near field tests. Like I said compare apples with apples. If you want to nit pick at accelerometer based servos you need to compare like with like.

I am getting sick of this avoiding the issue of an otherwise straight forward measurement. I am not interested in the subjective aspects of how much distortion is enough because if the hardware is good at what is does then I shouldn't have to worry about this anyway. I just want to see what the hardware is capable of doing and how good it is at doing it.