[Danny Richie]

Danny, I understand the difference between listening and measuring, but we are not talking about (for example) a piece of wire here, but a circuit that (it is claimed, and amongst other things) changes the effective system Q by a factor of 10. Surely it can't be that hard to show.

It is not that easy to measure. We are talking about differences in spectral decay rates in really low frequency ranges. That is REALLY hard to measure. You really need to be about 50 feet away in a really good anechoic chamber to get good measurements down that low.

I think Brian may be able to show differences in distortion levels with his set up. We'll see.

I sure wish you were closer.

I expect we'll have to wait a few years though, as you'll need to get your PhD before Brian will be able to talk to you.

John, those types of comments are not helping. That is the kind of comments that are really putting people off.

I know I am not the most tactful sometimes in my comments and they may sometimes come off condescending but I can assure you that is not my intent. I have been know to be brutally honest, but I am always honest. And if any of my comments here have been taken as such I certainly apologize.   

[JohnR]

It's not like they're in an industry that provides real/valid explanations for audible claims.  The whole industry is full of it (little pun there.)

I'm actually fine with Danny's exclamation that you just need to hear/experience the result and not worry about the technical details.  If potential customers are convinced and lay down their money, excellent.

I think it might be easier and more successful if Brian would actually take down a bunch of the technical information on his website.  Most of the customers wouldn't really care one way or the other, and it would preclude him getting bogged down in discussions like these.

Anyone, besides me, in this thread ACTUALLY have dipole basses in use with their Maggies? 

Davey -  of course, you're right. It started with a simple point and a question.

I don't personally have dipole subs in use with my Maggies, as I ended up not buying Maggies but a pair of electro-static mid-tweets instead. Hey, you can't have/do everything.

[Danny Richie]

What model is your mic specifically?

I have one of these: http://www.audiomatica.com/wp/?page_id=224

[dBe]

The thing that gets me is comments like "every other sub isn't even in the same league" implying, actually straight up saying, that if you don't have a servo sub, you're not going to get the best bass possible. But once you start looking outside this little realm you see that just isn't the case.

It is very easy to see comments like that as a wee bit off the wall, but there  are big differences in LF reproduction by different types of LF systems.  One of the difficult things is gettin the speed (impulse response) correct for proper integration with planars like the Maggies.  Here in Albuquerque a guy by the name of Pacha Kaye had a pair of Tympani's years ago.  His subs were the old KEF oval LF drivers in long transmission lines.  This was a long time ago and I still remember the tight, tuneful, extended bass that these guys put out.  What I remember the most is the way they integrated with the Maggies.  They worked.

Bass is easy to come by.  With enough swept volume and enough horsepower to a low Fs driver you can get huge amounts of bass.  Look at (but don't listen to) the car guys.  SPLs that would deafen an already deaf person even more.  Good bass systems, like people, need to have integrity.  This means that they must: go very low; move a tremendous amount of air; trace the signal accurately, and so on.  The most important things to me are that the LF system adds no resonances of its' own and integrates well with the drivers that it hands of to in the context of impulse response.

As a bit of an outsider I think I know where Danny is coming from considering these requirements.  For some time he has been dealing with high sensitivity systems and very "fast" drivers.  [Sidebar: I don't EVEN want to get into the driver speed discussion here... not my intention] In order to get LF drivers to integrate well with these types of drivers we need to have either strong magnetic systems (high BL) or an external method to control the cone.  Brian had the perfect control system for this application and Danny knew what he wanted from a designers perspective to meet his needs.

One of the byproducts of this type of LF module is the ability to integrate well with planars.  Planars tend to be lower in efficiency and a lot of people have tried to integrate low Qts subwoofers with mixed results.  Many sealed LF systems have a tendancy to ring at very low frequency.  Low frequency performance that compliments the performance of Maggies is hard to achieve.  I've heard a lot of systems over the years and my take on this is that Brian's sensing coil technology mated with the H-frame and Danny's woofers is a no-brainer in the context of integration and extension.

Dave

[rythmik]

Don't be a dimwit. This is a public discussion forum, there is no "qualification" required for entry or participation. The question is really very simple: can you provide measurements to demonstrate the claims being made for your servo system? Seriously, it's a simple question, that never needed to go where you've taken it.

You still did not answer my question. what is a linear time invariant system?  I am trying a guide a discussion with some common language here.  If you don't know, just say you don't know.

A linear system satisfies scaling and superimposition.  So F(a*x+b*y) = a*F(x)+b*F(y).

A time invariant system is if you apply a signal now or  5 sec from now, you get the same output response except the time difference, That is A(t) is an input with time. F(A(t-k))(t)= F(A(t))(t-k).   

For a continuous sine wave, you can chop up the inputs into single cycle, find the output response of single cylce sine wave, and rebuild the output waveform using time translation and superimpostion and recontrcut back a continuous sine wave.

A nonservo sub cannot even maintain steady output when the input is steady.


It violates all the assumption that we have for linear system.  How do you characterize a distortion type like this?

If you do an FFT, you get extra side-band energy.



And now with servo:

[JohnR]

A nonservo sub cannot even maintain steady ouptut when the input is steady.

Judging by the name of the image, this is because of "thermal compression." The time scale is 6.5 seconds, I'd guess I'd question the relevance on that basis, but regardless, how does the servo sub do?

Edit: never mind, looks like you edited your post, as your are prone to doing. What's the scale on the FFT (it's hard to read)?

Edit again: Ok I see. So even the servo is -30 dB on the second harmonic. What is the power level?

[rythmik]

Judging by the name of the image, this is because of "thermal compression." The time scale is 6.5 seconds, I'd guess I'd question the relevance on that basis, but regardless, how does the servo sub do?

Edit: never mind, looks like you edited your post, as your are prone to doing. What's the scale on the FFT (it's hard to read)?

It is 2048 points with full bandwidth of 1.2Khz and it starts with 10hz. Frequency is in log scale.  I chop off the lower end and upper end so that it is better to read.  BTW, I have all these on my website.  It is not like I don't do anything.

[JohnR]

What's the power level?

[rythmik]

What's the power level?

It is half full power. So it is 200WRMS.

[JohnR]

And which driver is it?

[rythmik]

And which driver is it?

It is DS1200. But it applies to all drivers. This happens at the impedance minimal points where the DCR completely determine the driver's impedance. In that case, the amplifier-drive interface acts more like current driver mode and any variation of DCR affects the output most. On the other extreme, if you look at the impedance peaks, it is more like voltage drive. The DCR variation does not affect its output at all.   

[Danny Richie]

Davey, as per your last post. Thank you!

[AJinFLA]

John/AJ,
I have a sense you guys are not really EE trained.

No need to further Red Herring the argument Brian, you don't need a PhD to do that!
A simple "AJ, you know that I know I don't have a shred of soundwave related data to support that resistor et al silliness" would have sufficed. My questions are rhetorical in nature.
Fact is, your servo system works nicely, but there is far more to getting perceptually "good" bass in real living rooms. Many ways to get there, not just one.

Dave, glad you're feeling better.

Oh yeah..and HAL, I can "measure" the effect of Sunspots and the earths gravitational field on a stereo system. But that doesn't make either audible via soundwave>cochlea conduction. Not that they aren't "audible" .

cheers,

AJ

p.s. Ok, so who's going to be the first to come out with Servo Maggies 

[Rclark]

Or servo Neo panels, servo dome tweeters, etc.

great post...

Dave

Thanks Dave.  The main issue I have is the "all or nothing" pitch. Because I believed it. Came here in '10 and Danny seemed very convincing. I know he means well, but he goes really over the top with the "nothing in the same league" comments about all his products, or tweaks. And he'll say that about everything, everything makes a huge difference, new cap, huge difference, new wires, huge difference. I now have a much clearer understanding of what these kinds of changes bring, and I think the wording is a bit disingenuous. It makes the uninitiated want to buy nothing but GR, so I supposed it's effective. But my experience is finding there are very much products in the same league.

I would prefer the "here is our technology, I think it is superior, here is our data, yes that other product is nice and well designed, but look at what ours does and why I think our design is better", rather than "... that product is not even in the same league, that product is terrible, just terrible, you'll be suffering if you go that route."

I'm speaking here as an objective and wary customer, a bit wiser, who has a wallet to look after. I'm not saying I won't ever buy GR, but the marketing is a bit disingenuous.

I'm sure the servo subs are quite nice, and I'd love to hear one someday, but I no longer believe they are the end all be all. I certainly don't believe they are the only way to achieve accurate bass.

For the record, my sub is running with my modded Maggies and I couldn't tell you where the sub stops and the speakers begin. No servo.

edit: it's an Epik Legend. And for the record I own GR Insignia mod speakers and auditioned the N1X at length.

[mcgsxr]

I have bought items from GR, and have heard one of his OB designs (the OB7 for the record), but have never heard servo bass.  I'd love to build some of Danny's OB speakers because I have personally loved the DIY stuff I have built, and it would be cool to own something designed by someone that likely knows a lot more about design than I do.

My degree is a BCOM, and I played violin for 10 years (ending at the 9th grade conservatory).

I have decent ears, but lack the math skills or interest to learn about it, to objectively assess.  I frequently point this out in my posts that I am a purely subjective listener.  I don't care if there are rats in a cage in the subwoofer cabinet, if it sounds good and I can afford it, I buy it.

I appreciate that the vast majority out there are more technically inclined (specific to audio) and enjoy the objective clarifications.

I also appreciate that this thread has mostly been civil.  I'd like to see it continue to be.

I don't mind reading about what objective measurements folks have and compare etc, but for me it is a secondary interest to what sounds good.

Do the folks around here with a vested interested in their own business act passionately?  Of course. 

Does everyone always contain themselves?  Of course not.

Keep it fun folks, it is just audio after all, even if you are making a living doing it.

[Early B.]

I built my GR Research OB servo sub based primarily on Danny and Brian's reputation, and that proved to be a smart move. My OB servo sub is, by far, the best subwoofer I've heard in my home, and I've owned many of them -- Hsu, SVS, AV123, and VMPS, to name a few. All of them provide "one-note bass" in comparison. There's nothing in the same league that I have personally heard. IMO, for 2-channel listening, if the bass isn't right, then nothing else matters. I don't understand the technical aspects, nor do I really care. I only care about one thing -- how it sounds. Now, you guys can continue to go back and forth to argue with experts about the technology. I find it quite amusing. 

[JohnR]

I find it quite amusing.

Well, you know what they say about people who are easily amused.

[HAL]

AJ,
The article is a methodology to measure differences in capacitor DF and DA parameters with different dielectric materials.   They found measurable differences and tried to correlate that with sound quality.  They did recommendations for materials for different applications.

What was not done was a threshold of audibility level study of each parameter.   

To me the differences in the Mylar caps in the original Maggie IIB crossover and the replacement Polyproplyene caps was significant sound quality change for the better with the new PP caps.   That also correlated with the findings of the article. 

I have an old Genesis 12M servo woofer with the metal cone 12".  This has a sense coil for motional feedback control.   The amplifier is very sensitive to changes.  They actually made different gain settings internal to the amp depending on the sensitivity range of the driver in use.  There was no way for the user to disconnect the servo loop and keep the driver connected, as that would probably have smoked the amp. 

My listening findings, seem to be like yours about servo woofer systems and goes back to 1979.   The first Infinity IRS Reference III's had accelerometer based motional feedback servo control.  This was a six-12" driver per side setup with 1.5KW of amp power per side.  This was truly an ear opening experience.  From my listening to the OB servo subs in the Super-V's, this is in the same league.

What is needed in this discussion is a test methodology like is being proposed to try and measure the differences between a servo and non-servo driver.   Since the servo amp was never intended to to be used open loop that does not makes sense.  The same amp without the servo feedback system does make sense.  That is what I belive is now being attempted.

Possibly one way to analyze the difference is to use a subtractive method to see what the difference function is between the two measurements.  There will be linear and non-linear components that will need to be analyzed.  Just a thought.

   

[Nyal Mellor]

I would prefer the "here is our technology, I think it is superior, here is our data, yes that other product is nice and well designed, but look at what ours does and why I think our design is better", rather than "... that product is not even in the same league, that product is terrible, just terrible, you'll be suffering if you go that route."

Agreed. I hope people are wise enough to take statements from one manufacturer about another manufacturer's products with a large grain of salt, especially when bashing things that the manufacturer doesn't seem to properly comprehend.

[AJinFLA]

AJ,
What was not done was a threshold of audibility level study of each parameter.   

To me the differences in the Mylar caps in the original Maggie IIB crossover and the replacement Polyproplyene caps was significant sound quality change for the better with the new PP caps.  That also correlated with the findings of the article. 

None of which constitutes evidence that caps change soundwaves>ears to audible thresholds by means unknown...means like "capacitance" or "series resistance"  .
We/science knows exactly how to find out whether things are "audible" via soudwaves, vs "alternate" means. Clarity gave it their best shot, but alas....another fail. Now back to dipoles/Maggies....

I have an old Genesis 12M servo woofer with the metal cone 12".  This has a sense coil for motional feedback control.   The amplifier is very sensitive to changes.  They actually made different gain settings internal to the amp depending on the sensitivity range of the driver in use.  There was no way for the user to disconnect the servo loop and keep the driver connected, as that would probably have smoked the amp. 

My listening findings, seem to be like yours about servo woofer systems and goes back to 1979.   The first Infinity IRS Reference III's had accelerometer based motional feedback servo control.  This was a six-12" driver per side setup with 1.5KW of amp power per side.  This was truly an ear opening experience.  From my listening to the OB servo subs in the Super-V's, this is in the same league.

What is needed in this discussion is a test methodology like is being proposed to try and measure the differences between a servo and non-servo driver.   Since the servo amp was never intended to to be used open loop that does not makes sense.  The same amp without the servo feedback system does make sense.  That is what I belive is now being attempted.

Possibly one way to analyze the difference is to use a subtractive method to see what the difference function is between the two measurements.  There will be linear and non-linear components that will need to be analyzed.  Just a thought.

Well, I suspect if you compare apples to oranges...you're gonna find a "difference" .
The question then becomes, are apples "better" than oranges.
Been doing the gradient vs non-gradient and servo vs non-servo thing for quite a while now...and my position is still - plenty ways to get to the very same place. The science of sound ain't no mystery...or magic, to me  .

cheers,

AJ