[HAL]

Based on my listening experiences, I don't agree with your continued dismissal of its quality. In fact, I don't think you've ever heard it used properly and are just speculating/badmouthing it in order to help you hype your supposed "best sounding but we've not even built it yet" product. That aside, can you be specific about the "how it does it" comment? What is it about "how it does it" that is "bad"?

JohnR,
I have a DEQX 2.6P and Beheringer DCX2496 as examples of digital crossovers.  Have used them in the past for multiple speaker ideas.  The DAC's in both are not that great sound quality wise.  I have heard the newer unit at RMAF and it did sound better.

Danny and others have heard the DAC section that I have worked on as part of the digital crossover project.  I was in his DAC shootout awhile back.

My idea is to couple those DAC's to a PC for The Monolith digital crossover.  One section will drive the three 8" servo's per side in that design.  Not unlike the idea of the bass setup for the Maggie's being discussed here. 

I use to have Maggie IIB's and VMPS standard subs back in the 1980's with biamped Maggies using their passive crossover and Hafler DH220 amps.  I think the servo subs with the Maggies here would be a fine setup. 

[Danny Richie]

Guys, I never said that the mass of a driver had something to do with its ability to accelerate. Davey pulled that from my comparison to some cars.

However, mass does have a lot to do with the speed of a driver. It can easily be measured by how high a driver can play. So one cannot say that mass has nothing to do with acceleration.

Now let me clear up a misconception. When people talk about the bass response of a speaker in terms of bass being really fast, or bass being slow, or any other loose terms you want to throw in there like sloppy bass or quick bass response, etc, they are not really talking about the acceleration of the woofer or how fast it moves. If it moved any faster or slower than the input signal then it would be playing a different frequency. It can't really play any slower or faster than the input signal. What people are really hearing when they describe things like that is the settling time of the woofer or woofers. It's how fast it recovers from the signal, not how fast it plays it.

Here is an example. Many people listen to a line source speaker using multiple small drivers and I hear them saying that "I have never heard bass so fast", or "that's the fastest bass response I ever heard." And I have heard that a lot. I have exhibited at RMAF many times with line source designs. They say things like that because the recovery time or settling time is so fast. For one, the drivers are light weight, but secondly, they didn't have to move very far to hit a high SPL due to the use of so many small drivers. So they return to rest very quickly. Some people have never heard bass like that before and are a bit freaked out by it. It is even really hard to blend a lot of subs to some of these really good line sources that play down very low. Traditional subs sound very slow by comparison and a lot of resolution is given up if the subs are allowed to play up very high. The line source by comparison is just MUCH faster.

It's all about the stopping speed man!

[JohnR]

However, mass does have a lot to do with the speed of a driver.

Danny, your 12" driver has nearly twice the mass of the Lambda-designed Dipole12, so by your own criterion, it comes out a pretty poor second.

Also, you didn't answer the question about the Le spec. Do you know what it is?

[Early B.]

This is an amusing discourse. It's kinda like an amateur welterweight sparring with a heavyweight champ, and despite getting knocked out repeatedly, he believes he can still win the fight. 

[lowtech]

This is an amusing discourse. It's kinda like an amateur welterweight sparring with a heavyweight champ, and despite getting knocked out repeatedly, he believes he can still win the fight. 

Moreover, some of the spectators are (apparently) rooting for the emperor who's not wearing any boxing briefs.   

[Danny Richie]

Danny, your 12" driver has nearly twice the mass of the Lambda-designed Dipole12, so by your own criterion, it comes out a pretty poor second.

Also, you didn't answer the question about the Le spec. Do you know what it is?

That is super light weight for a 12" woofer if that is correct. It must have a really small motor structure to hit those T/S parameters with that light weight moving mass. So you get less stored energy, but less electrical control too. I don't know what the net gain would be. It might be a slight positive but not much.

You still really can't compare that to my servo controlled woofers because my servo controlled woofers are not used with a traditional amp. You can't even compare the specs. It is a complete system. The electrical control of the servo system is about ten times faster than a typical driver sized driver with no servo control. It doesn't just apply and electrically resistance or brake like adding a resistor to a second voice coil. It actively powers the driver with a reverse polarity signal to counter the force of any movement that does not match the input signal. You can press on the woofer while the system is playing and it will react to the movement that you just created and instantly kick back with an equal force to counter your movement. It is kind spooky at first and will scare you if you are not ready for it to kick you back.

And the inductance of the voice coil is not really relevant nor are any of the rest of the parameters for the most part. You can change the Q of the system by simply flicking a switch to a higher or lower damping setting. So the stopping force is not just about mass, or driver Qts, it's about what the system can do as a whole.

[Danny Richie]

- Many have said (also on this forum) that 2 GR's per side would be more than enough in dipole setup. On the other hand, it is also often said that due the acoustic realities, even 4 x 12" is not gonna give very strong bass in dipole and at least 15's or 18's should be used to get real punch on dynamic music. What's your comment on this? Can GR's really give so much more punch that you can use half less of them? If, why?

Maybe this information will answer that question better: http://www.rythmikaudio.com/smartQ.html

[Davey]

Guys, I never said that the mass of a driver had something to do with its ability to accelerate. Davey pulled that from my comparison to some cars.

It's all about the stopping speed man!

No I didn't. 

And isn't stopping all about acceleration too?

Dave.

[Rclark]

 Danny you can't say you didn't say it, you said it and repeated it in several posts. JohnR even quoted one of them. It's okay, everybody makes mistakes, you can't know every single thing about every parameter. 

"high moving mass that hinders acceleration.."

 Your GR servo subs have a sterling reputation, nobody denies what you say about the servo's "stopping power". I'd like to hear them myself someday. I have come to temper my expectation of them though, because out there in review land, there are people that don't care for them, and there are even head to head shootouts where non-servo subs (like HSU) are considered to be just as accurate. But regardless, your subs have a top notch reputation, especially in the Super V and now Super 7.

 Anyway, I have no doubt that some Dipole subs would rock with Maggies. I was going to do it, but I decided to go a different route, with a swarm of sealed subs, and I did a lot of research and ended up with the dual 12" opposed Epik Legend, which I absolutely love.

 But I do mean to get around to try OB subs one day, and GR is top of my list for that.

[Danny Richie]

Danny you can't say you didn't say it, you said it and repeated it in several posts. JohnR even quoted one of them. It's okay, everybody makes mistakes, you can't know every single thing about every parameter. 

"high moving mass that hinders acceleration.."

Dude, I was talking about three different cars... It was an comparative analogy. Read the whole post below.

You are looking for a new car with all out performance and handling. Your main options have been narrowed down to a Chevorlet Suburban, a Ford Expedition, or the Chevorlet ZR-1 Corvette.

Two have high moving mass that hinders acceleration and the high level of wind resistance due to the large surface area also really limits acceleration. The high moving mass also makes them difficult to stop especially at high speed. They are just not very agile vehicles. The third choice has less moving mass. So acceleration is great, and with less moving mass it makes it much easier to stop. More importantly though is that the huge carbon fiber brakes brings it to a stop much quicker than the others. It is really not a comparison really...

No I didn't. 

And isn't stopping all about acceleration too?

Dave.

That would be deceleration.   

[PDR]

Rclark.......

You can read all you want about sex...and what position is the best....
Youll get all kinds of this is better than that.....heck they even make instructional videos.....
But until you tried it.....well...

Just remember to wear ear protection the first time you hear servo subs.....

[Rclark]

I have a feeling you're right.. My only concern would be a lack of punching power, which the sealed sub I've chosen delivers in spades, plays very low but also up high into the midbass if you want. Something of a marvel.

[PDR]

I have some Shefield recordings of Drum solos....
Friends that are pro drummers have heard these on the servos....
Lets just say its like the first time....punch you in the chest real.

[stevenkelby]

I have come to temper my expectation of them though, because out there in review land, there are people that don't care for them, and there are even head to head shootouts where non-servo subs (like HSU) are considered to be just as accurate.

I haven't seen that, could you share a link or 2? PM if you don't want to post. Thanks for the info!

Steve.

[Rclark]

Sure thing, I'll send you some links tommorrow. I'm watching Walking Dead and about to pass out.

[lowtech]

Danny, an off-topic proposition for you.  Since you're so big on vehicle acceleration analogies, how about we have a little competition on a real drag strip?  I win you give me a pair of your dipole servo subs.  You win and I'll buy a set at full retail?  The only criteria is you race your daily driver and I race mine.  Deal?   We'd have to meet up somewhere between Texas and Seattle. 

[Early B.]

Your GR servo subs have a sterling reputation, nobody denies what you say about the servo's "stopping power". I'd like to hear them myself someday. I have come to temper my expectation of them though, because out there in review land, there are people that don't care for them, and there are even head to head shootouts where non-servo subs (like HSU) are considered to be just as accurate.

Some people are so accustomed to "boxy bass" that once they hear what "boxless bass" sounds like, they nonetheless prefer the boxy sound of a typical sub, and that's OK. Like any other speaker design, OB servo subs aren't for everyone. When I first heard the OB servo sub, I felt it wasn't producing sufficient bass, i.e., enough "punching power." Eventually, I realized that the bass I was hearing was very musical, and it transformed my point of view of what good bass is supposed to sound like. For example, the sound of a kick drum in a typical "woofer in a box" sounds like it came from a box, but when you hear a live kick drum, there's no extraneous bass reverberation, and there's no "room loading." Of course, I really didn't know what room loading sounded like until I heard an OB sub. Another major benefit -- in terms of getting great bass, the room plays a key role, but with an OB servo sub, the room is less of an issue. However, the OB servo sub takes a while to set up. There's a bunch of dials and switches on the amp, and you gotta find the right balance for your taste. A typical sub has a volume and phase switch, and you're done. 

[Rclark]

Just to be clear, I was referring to box sub versus box sub...

I hear what you're saying though, my Maggies are essentially the same thing and produce good bass into the high 30's. So I have some idea of what to expect.

But.. when I talk about my sub, the idea is I'm adding multiples. The preponderance of my research has shown that people prefer a swarm of sealed subs to a pair of OB subs. Multiples of sealed subs seems to tip the scales.

[lowtech]

Some people are so accustomed to "boxy bass" that once they hear what "boxless bass" sounds like, they nonetheless prefer the boxy sound of a typical sub, and that's OK. Like any other speaker design, OB servo subs aren't for everyone. When I first heard the OB servo sub, I felt it wasn't producing sufficient bass, i.e., enough "punching power." Eventually, I realized that the bass I was hearing was very musical, and it transformed my point of view of what good bass is supposed to sound like. For example, the sound of a kick drum in a typical "woofer in a box" sounds like it came from a box, but when you hear a live kick drum, there's no extraneous bass reverberation, and there's no "room loading." Of course, I really didn't know what room loading sounded like until I heard an OB sub. Another major benefit -- in terms of getting great bass, the room plays a key role, but with an OB servo sub, the room is less of an issue. However, the OB servo sub takes a while to set up. There's a bunch of dials and switches on the amp, and you gotta find the right balance for your taste. A typical sub has a volume and phase switch, and you're done.

What you are describing isn't exclusive to Servo dipole bass.  Some of us have been using dipole woofers for more than a decade and what you describe is what I've been hearing for a very long time.  Welcome to the club, albeit a little late.

[Early B.]

Just to be clear, I was referring to box sub versus box sub...

OK, gotcha. I just want to add that an OB servo sub is gonna sound very different from the same woofer/servo amp if it's built in a box.