Axiom Home Page Forums General Discussion Technical Questions A question about DSP

Hey all,

Just wondering what's the deal with DSP? Is it worth it to have a subwoofer that has it?

The answer is: it depends. While many great DSP-less subwoofers exist, the benefits of DSP technology are almost too good to pass up from a design perspective. Axiom's DSP circuitry is programmed with the specific characteristics of the driver, so the amp is able to precisely control the driver without distortion.

(or over-driving to the point of causing damage)

Like Cole Trickle in Days of Thunder.

the only thing is Axiom DSP subs are WAY over my budget

Check our Hsu Research subs, then. No DSP, but great performance.

Let's not forget the EP350 is a very good performer for the money. Also look to Elemental Designs, they have some very good/lower priced subs. Epik is yet another place to look.

The Paradigm DSP series of subs is good bang for the buck too, the 3100 is great with music and can add something to movies but the 3200 is much better with HT and sounds just as good with music.

I do not think that is correct. As you boost the signal using dsp/eq you also increase distortion. The big advantagesof dsp/eq is that you can extend the bottom end on the sub and control over-excursion.

As to whether or not you can hear the added distortion is not entirely clear. Certainly the EP600 compared to the SVS pb13 there is a lot more measured distortion as you get to the bottom end of the range, yet the sonic differences described in direct comparisons are subtle, at least for music.

fredk,

Distortion is a very misunderstood thing in audio and especially subwoofers. A lot of this just comes from the word “distortion” itself. Certainly on the surface if you simply ask; “would you like less distortion or more distortion?” the answer would seem obvious. But the answer in fact may be that you want more distortion. I guess I had best explain how that could be possible! The reality is that there are many different types of distortion. The basic categories would be linear, non linear, harmonically related, and non harmonically related or noise. On top of the different types of distortion there is also the matter of what frequency they are occurring at. The typical measurement is THD (total harmonic distortion) or THD+N (total harmonic distortion plus noise). Unfortunately these measurements are just not detailed enough to explain if the distortion is going to be a problem; in other words is it going to be audible. Once you drop below the audible level of any type distortion it ceases to be a concern in audio design. This is very important when analyzing distortion. If one type of distortion is audible at say 10% but another type is audible at say 1% then you would not want to try and reduce the 10% number at the expense of the 1% number. From a specmanship point of view you would look like a hero if you reduced the 10% number to 5% (50% less distortion). But what if in doing so you raised the 1% number to 3%? The result would be a much a better spec of 5% THD+N versus 10% THD+N but the reality would be that you now have audible distortion. This is obviously a very in-depth subject that I am barley scratching the surface of here but is also a topic we have researched ad nauseam at Axiom over the years. Perhaps I should write a multi chapter piece on it for our newsletters or even have a workshop on the topic at the get together.

As for DSP use in a sub-woofer it is important to keep in mind that DSPs come in many different flavours. In our DSP controlled subs we are using a very powerful (and hence expensive) DSP that allows us to control every aspect of the sub-woofer performance. We did consider using a small DSP in our less expensive subs but the reality is the limitations of the small DSP made analog control a better option. Unfortunately we lost the ability to claim DSP use in our smaller subs but that would be back to the specmanship game again, like above with distortion, and we try to avoid that.

Great post Ian! I for one would enjoy and appreciate an article better explaining distortion.

I did some light Internet research into distortion after getting a demo of a friends tube amp that he had modded to easily swap different types of tubes. He like to tell me what to listen for before he made the swap so I wanted to understand the real difference to determine if my brain was being fooled by his introductions to each tube or if the audible effect was real. The material I found ranged from much too basic to much too detailed with little in the useful, middle ground. In short my interest is peaked and would love to hear a discussion from someone skilled at hitting the middle ground.