Axiom Home Page Forums General Discussion Technical Questions DSP vs EQ

I've been wondering for a while. Whats the difference bwetween the dsp that is applied on subs an what an equalizer does? Is this just two different names for the same thing?

When you stick a driver in a box and plot the SPL vs. frequency of that system (ie. the frequncy response), the graph will be "all over the place". By programming equation coefficients into a DSP, the desired response is produced. For frequencies where the graph is too high, the DSP will compensate by requesting less power from the amp. For frequencies where the graph is too low, the DSP will compensate by requesting more power from the amp. While this sounds great in theory, in practice it can introduce problems like phase delays and harmonic distortion.

Now when you take a sub like the 600 which was designed for a flat frequency response and stick it in a room and graph the frequency response, the graph will likely not be flat because the DSP has no knowledge of the room. Enter the equalizer. If you know where your peaks and valleys are, you can knock them down or bring them up by adjusting the equalizer. This again sounds good in theory but in practice you don't have discrete control over each and every frequency using an equalizer.

The EP350 dosn't have dsp. Why is it not "all over the place"?

I think what you are saying is that dsp circuitry and an equalizer are more or less the same thing. The DSP is hard wired, where as an eqalizer allows you to adjust those 'power requests' for specific frequencies/bands. Is this correct?

That's correct.

The 350 is not all over the place but it's also not flat. Filters using discrete components (capacitors, resistors, inductors) were used to "tame" the raw response. Axiom did a great job on that one!

Hmm... equalization of another sort. So all subs do equalization of some sort then??

I've been wondering about the range of comments I see on various subs including the EP500 and 600. There seems to be more than the usual amount of bias out there around subs so it becomes hard to sort out what the relative performance of various subs is.

All subs have some form of equalizer, yes. The only way to sort out the relative performance is to listen to them. And just because some are popular doesn't necessarily make them better than others. The SVS PB12 (I think that's the name) that Jason brought over is a popular sub at a popular price and although it's great for movies, I got sick of the thumping when it came to music. The 350 in my opinion is a better sub.

Was the "thumping" you refer to anything close to the "chest thump" you've mentioned before that is missing from your 600?

Yea. I've just finished reading a thread over on audioholics by someone who upgraded from the PB12 to PB13. He commented on how he never liked the PB12 with certain music because stuff like kickdrums just didn't sound right.

After my visit to Axiom, I was considering the SVS PB10 as a reasonable alternative, but given the above comments on the PB12 I suspect I may be dissapointed.

Given the choices here in Canada, as things stand I will end up with the EP350.

I wonder If Axiom will go from dsp to eq in the 500 and 600. If you are going to equalize, it would seem to make sense to do so for the room the sub ends up in.

The DSP is a tool used to obtain the flattest response (and go low with the same +/- 1.5db) at a lower price (after a 5 minutes search, I did not manage to find back the post from Ian talking specifically about that).

The flattest the sub, the easiest it becomes to place in a room (unless you just happen to have a room that compensates exactly for a non-flat sub; it can happen!), and even more so when you want 2 or more subs as they will blend more easily. If there is problem in the room, then you can use an equalizer to further compensate.

If I remember right it is. I seem to remember Mojo saying,"now that is what I am talking about".

I seem to have tamed the PB12 enough that I like it now. I run the XO at 60 and I repositioned it so it is firing into the side of my couch, instead of across the front of the M80s from a corner. It is blending much better. I am still waiting for the PB13 to ship so I can do a comparison.