It would be interesting in the end and independently of which way is chosen, what’s the advantage of a none use of servo except cost savings (as in pure technical theory it should be better as far as I can (not) judge it). On the other hand if it would be really superior generally, more cost no object designs should have used it? Difficult to oversee for us consumers.
@Paul it just occurred to me that the original AN3 prototypes are now taking up valuable space at PS Audio Galactic Headquarters. Being the paragon of selflessness that I am, I’m willing to assist you with this major roadblock to progress. Yes, you can unload them on me. Hell, I’ll even pay for shipping.
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We are currently using an XBL design on the midbass, which is like an underhung, in that the motor force is essentially constant across much of the stroke of the driver, but flux utilization, and power handling is better and Xmax is higher for a given amount of steel and coil length.
For the subwoofer driver, it is an overhung design but I’m using an undercut pole piece and pole extension to improve the linearity.
@Chris_Brunhaver what is the difference between an XBL and XBL^2 design? I’m curious as I have an Adire Audio Brahma sub (developed for car audio) from ~2002 using XBL^2. I believe (but am not 100% sure) that Adire Audio is the house brand for the original XBL OEM.
Man, come on! Who cares at the end of the day IF it sounds great? You’ve been going on and on about this, if at the end of the day it sounds great as the bass driver was designed in a way to sound great, WHO CARES if it’s Servo or not?
Honestly, I take ALL the “tech talk” with a grain of salt… EVERYONE was on and on about Magico technology, the Aluminium block, how silent the cabinet is, etc… and when I listened, MEH, over and over again, all auditions resulted in disappointment.
I personally found the bass in the prototype AN3 in Axpona too boomy, over-powering and I am glad they’re changing things to tighten it all up.
Fully agree, it doesn’t matter at all what’s inside at the end as long as it’s their preferred solution…I’m just interested to understand the reason why a servo can be worse than no servo (which seems to be possible). I’m not keen on having one implemented if it’s not the best solution…I so far just understood it’s generally the best solution technically. Just trying to understand the background of the changing insight. Ted would explain such backgrounds in a minute when it concerns DACs.
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It’s interesting in that I couldn’t figure out if people were irritated that it didn’t have a servo woofer (as in servo is better/not better), or if it was because Paul had said it would be servo and then it might not (IE Paul going back on his word/preferences). I agree that, in the end, how it sounds is all that matters…
“Going back on his word/preferences” seems a bit harsh.
It is not as if we are entitled to a servo woofer, such as we put down a non-refundable 50% deposit on the speaker based on a representation there will be servo woofers and the manufacturer has engaged in bait-and-switch, deleting the servos.
PS Audio is instead merely sharing the development process with us. The design is going to continually evolve, including the thinking as to what is best for the application.
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Just to mention from my side:
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I had and still have interest what can be a disadvantage of a servo (as I thought it must be somehow superior generally).
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I mentioned that Paul so far declared a servo as mandatory for proper bass response and for the AN-3. I also mentioned that I have no problem with the fact that it was now considered to eventually use no servo because it possibly sounds better like that. And I can also easily live with the realization that when Paul makes a general statement, it’s probably as much just a current status of his personal knowledge as with anyone else.
Hope this helps 
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Snooze
Hi Jedi,
Yes, this is the very same XBL as your Brahma (he has since dropped the ^2 branding, as far as i know). I worked at Adire Audio and I was hired as one of Dan and Dave’s early employees there.
I learned a ton from them about low distortion woofer design and still use some of the FEA tools that he developed (they are great).
Fun fact, I’m using the same spider profile as your Brahma on our subwoofer driver. Our version has quite a bit softer compliance (to get to a 20 Hz resonance) and has has leads stitched to the top, but is otherwise the same.
The suspension is incredibly linear in the +/- 25 mm range, as seen by this old Adire DUMAX report.
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Ha! That’s super cool. The crazy linearity coupled with the high excursion is what initially attracted me to the sub. Over the years I’ve been through many subs at that performance envelope (JL W7s, etc.) and the only one I’ve kept all along is the Brahma. It’s a beast (it weighs 39lbs lol) that sounds fantastic and has been out of the car and part of my home system for many years now. Perhaps @Paul should think about doing standalone subs somewhere down the line. I’m very intrigued by the XBL usage in the midbass drivers. Hopefully you guys will carry the tech down through the speaker lines…AN3 is way out of my budget.
The original Brahma was good but the addition of faraday rings and deeper rebates in the core and top plate have now we can take that sort of design to the next level. I almost went that direction with the AN3 woofer but this other design we did won out, for a few reasons.
Yes, we have been working very hard developing all of the bits of some great subwoofer designs (driver technology, amplifiers, servo, dsp etc.) and so I wouldn’t be surprised if that means some dedicated subwoofers in our future offerings. Certainly Paul is a big proponent of subwoofers for the highest quality music reproduction.
I like XBL a lot and have done a bunch of drivers with it over the years and will be using it where it makes sense in the other lines as well (probably even the Sprout speaker). For me, it’s great for doing a wideband driver with both great bass and midrange.
We will definitely have some designs that you can afford. As with a lot of products, it just makes the most sense to start with a top down design process where we develop the core technologies and concepts in a flagship offering and then scale and configure those for a full product family.
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Hey bud! I live in Minnesota as well and have been absolutely dying to hear the 20.7’s! !
Would you want to have a listening session this weekend?
Send me a text 612-402-0187 either way!! 
Since no one else has mentioned it here, Robert Harley gave the AN’s a Best of Show for the Money, and wrote, “the new PS Audio speaker (est: $17k) rivaled speakers approaching six figures.”
See, here.
Shoulda known - though when I wrote “here” meant “this here thread” ; )
As for servo, maybe it’s not needed with modern woofers…? Most servo designs date back to the 80-90’s…woofers have definitely evolved since then, lower distortion, higher excursion etc…
True, modern woofers definitly do a better job then their 70ties predecessors when it comes to distortion, excursion etc. But next to D3 reduction servo also minimizes enclosure influences allowing a designer to choose high Qbox values (=smaller boxes) without sacrificing low note performance. Which is a good thing if your a family man 
For example, this is what I get running a small servo driven 5" SB acoustics driver in just under 3 liters.
You emphasize that this is just a theoretical product since it’s still so early in the game. So, how can a price performance evaluation be made? The price has shifted—upward, I might add—at least as much as the rhetoric and product design. We have no idea what the final configuration or price will be. Why level judgements like this? Hype Unlimited…
Given Harley heard the speaker in its current configuration he had plenty of information upon which to express an opinion and to conclude it "rivaled speakers approaching six figures.”
If he was additionally told they are estimated to be priced at $17,000.00 he could reasonably judge them best for the money.
That is, he heard the product in front of him and judged it on its actual merits - not theory. He was not expressing a prediction as to the sound and price of future speakers which may or may not ultimately exist.
We all know the speaker’s configuration and price have not been fixed, and sufficiently astute to understand that best for the money judgments will differ if the sound and/or price changes.