Axiom Home Page Forums General Discussion Technical Questions Subwoofer Servo Technology

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I'd like to see more technically advanced Axiom products come to market,

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Umm, the DSP onboard the new Axiom subs were Axiom designed and then programmed with months if not years of efforts by Jim, an Axiom tech guru whose programming expertise is obviously very good. Call me crazy but designing and programming computer chips is considered cutting edge technology and not expensive, if you have the time to do it (DSPs on modern receivers are virtually a couple of bucks per unit these days).

I watched Jim during this building process for the prototype EP600. He had dozens of sheets of programming code to work through, tweaking each individual Hz until the DSP made the driver work in producing an equal peak (flat response) across the sub range. This would have been followed by testing in the anechoic chambers followed by more tweaking. Since this specific code would ONLY work for a single speaker design (change the cabinet, change the acoustics), the same had to be done all over again for the EP600. Jim has probably coded near half of the Windows XP OS in his DSP programming of the EP subs.
The result?
The EP500 has less than a TWO DECIBEL variation from the average across the 20-95Hz spectrum!! This is phenomenal and better than the reproduction i've seen with parametric EQs and DEFINES the most accurate sound reproduction possible (a straight line frequency response)!!



Creating a speaker with a flat response is NOT an easy feat (if it were then everyone would have made one by now), if not impossible without advanced DSPs to control the output; so to say that Axiom DSP technology is not advanced, is somewhat off the mark, no?
Many audio components are simple things like copper wire and analog signals. Many more "technically advanced" (e.g. digital speakers which you plug into a wall) are not exactly audio bliss. Sticking a new fangled miniature plasma screen on the side of a speaker with touch screen controls for a whopping 8 band EQ to say it is more technically advanced does not make a good speaker.
Have a look at the extensive and advanced research that Axiom does in the course of creating and tweaking their speakers over the decades. The appreciation of this work comes from reading about it and seeing it first hand, something that many audiophiles never take the time to do.

Hello peterb,

There is nothing new about servo-feedback design in subwoofers and Axiom isn't interested in servo-feedback designs. These have been around for decades and used by such subwoofer brands as Velodyne, PSB and Paradigm in numerous models that deliver very good performance, better than would have been achieved without servo-feedback integration.

However, Axiom believes that our DSP design in the EP500 and EP600 subs is superior to the older servo designs in a number of important ways. Without going into a long dissertation, using a custom-written DSP algorithm that contains all of the traits of our particular dual-voice-coil driver, the enclosure, our amplifier and the expected performance goals results in an integrated system that delivers much more linear performance and optimal output well into the sub-sonic region.

Moreover, using a custom DSP algorithm means that the sub can never be overdriven or damaged. The algorithm was arrived at throught constant measurements and test of the driver, the amplifier and the enclosure, with any non-linearities (deviations from the desired frequency response) compensated with new instructions in the digital code.

Me thinks you take offense WAY too fast. What I meant was:
"I'd like to see more, technically advanced Axiom products like the 500/600 come to market..."

Also, I didn't say or even mean to imply that DSP was a simple or unsophisticated technology. However, servo feedback systems, because of their dynamic nature, offer capabilities that are beyond what's possible with a static DSP implementation. Not that this is always the best or most cost-effective design, but intrinsically it's more complex and adaptable.

And please don't take offense (I own several Axiom speakers)but... a flat FR to 20 Hz at only 90dB is very good, but given the current competition, far from earth shattering performance.

I agree that the 500 and 600 subwoofers put out by Axiom are really outstanding, and I have never heard one! These subwoofers have really gotten people to notice Axiom, even some people that don't care for Axiom speakers (with or without valid reason). Audio gurus from all sorts of magazines, design groups, and installers are praising the outstanding audio of the EP500 and EP600.

Peter, I think that you are reading too much into Chesseroo's post. He isn't coming down on you, just stating some facts, and asking you to consider them compared to your statements (like when he typed "No?"). It is just to spark conversation. Don't get discouraged or frustrated. Go ahead and keep posting your thoughts and even better some facts about the technology, then we can all speak to it with some technical insight.

I'm always interested in learning. I aspire to inclusiveness.

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I was hoping to find someone who actually knows something about physics and electrical engineering who could discuss why Axiom went DSP when low cost servo technology is available

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I think Alan answered this question above. Axiom - at its heart an R&D company - believes the DSP path offers superior performance.

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However, servo feedback systems, because of their dynamic nature, offer capabilities that are beyond what's possible with a static DSP implementation. Not that this is always the best or most cost-effective design, but intrinsically it's more complex and adaptable

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I'm going to suggest "debatable" here rather than "intrinsic". Your earlier comment about finding "somebody who actually knows something" leads me to think that your assertions about the "intrinsic" benefits of certain technologies may come from other sources. Care to cite them? "Technical" Forum and all that.

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a flat FR to 20 Hz at only 90dB is very good, but given the current competition, far from earth shattering performance

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Are you going to suggest the alternatives by name and cite the quantifiable data, or just leave this hanging out there? What's "better"? How do YOU KNOW it's "Better"? How much does "better" cost? How are we measuring "better" this week?

Look, I'm not trying to be a hard case here. I like fun new blinky stuff that plugs in as much as the next guy. You are advocating and defending technology that is "different" - not "new" - while dancing perilously close to "Axiom doesn't know what they're doing if they're not pursuing THIS".

I liked Alan's reply. And yes, I do get grumpy before lunch.

So cute the way y'all spring to defend Axiom's honor against any perceived slight. Touching really.

I love Axiom, I buy their products, I know the whole story about Floyd Toole, the NRC etc. But do they represent the last word in audio? Are all technical approaches other than theirs wrong, a priori? Give me a break.

A priori?
Interesting choice of words considering it was used in an incorrect context. A priori to what?
The sentence doesn't make any sense without a reference.
Neither does your argument about how Axiom should be pleading at the doorway of Rythmik Audio for their amazing, "new" technology.
I guess i'll just go back to defending my Tannoys...oh i mean my Monitor Audi...no no, my Axioms because that's where my heart and soul of speakers is at and i have nothing better to do.

Main Entry: a pri·o·ri
Pronunciation: "ä-prE-'or-E, "a-; "A-(")prI-'or-"I, -"prE-'or-E
Function: adjective
Etymology: Latin, literally, from the former
1 a : DEDUCTIVE b : relating to or derived by reasoning from self-evident propositions -- compare A POSTERIORI c : presupposed by experience
2 a : being without examination or analysis : PRESUMPTIVE b : formed or conceived beforehand