Greetings

I was wondering about the DSP implimentation. Are you using a series resistor and a custom wound second voice coil to get a correction signal or an accelerometer based system? Also how is the system Q effected? - are different settings available?

cheers

pbc - you might do better to send an email to the technical folks at Axiom.

I don't think the DSP system is feedback based (believe it uses driver characterization info preloaded into the DSP) but best to check directly with Axiom at advice@axiomaudio.com or http://www.axiomaudio.com/advice.html. This board is really more of a user group -- a few people here already own EP500/600s but I don't think any of them are ready to take them apart yet

Just sent the question to "advice". But back a couple of years Ian used to personally reply here to some fairly technical questions.

adios

Hello pbc,

I do much of that on this forum now, although I ask Ian to contribute when I defer to his knowledge of driver design and loudspeaker measurement.

As to the DSP implementation in the Axiom EP500 and EP600 subwoofers, you'll find a detailed article by Gene DellaSala at the www.audioholics.com web site. Do a search there for the Axiom subwoofer models. Here is an excerpt that nicely describes the DSP algorithm and how it controls the proprietary driver and digital amp:

"Of course the Axiom engineers didn't just end it with a great digital amp design. They went one step further and implemented Digital Signal Processing (DSP) with a custom-designed "algorithm" tailored around the specific driver to linearize the response across the usable bandwidth at all power levels. This was to automatically correct frequency response deviations. The DSP also serves as a limiter to prevent the amplifier from exceeding its output limits and going into distortion. It also limits the subwoofer driver from over-excursion to minimize excessive distortion and cone break-up. The system is designed to minimize frequency response deviations to +-1.5dB (in anechoic environments) within the full bandwidth of the product."

Regards,

Thanks Alan
I did read DellaSala's article but it didn't seem to answer my basic question which is:

Is this a feedback servo arrangement or is it just processing the input signal (e.g. a Linkwitz transform circuit) ?

cheers

Pbc,

No, it is not a feedback servo arrangement. The custom written code for the DSP is programmed with the characteristics of the driver (which we designed, so we know its characteristics and limits) as well as those of the digital amp, which is also designed in-house. Because the two work in concert, controlled by the DSP, it is also why it's impossible to overdrive the sub. To go into this in greater detail would require both the input of Tom, our senior in-house engineer as well as Steve, who writes the codes. It would also go beyond what Axiom is willing to divulge.

Regards,