How I do full range equalisation.

Hi all, I kinda 'promised' this in my build thread, and I see that there is a discussion happening at the moment about full range equalisation, and it made me get off me backside and finally post this how to.

Well, not really a how to as such, as that implies that I am right!! Nahh, but it is how I do it and I like the results.

Just for background. I have always been plagued by a bit of 'harshness' at times. I use a deqx as the crossover etc for my system, and one of it's functions is that you can use the remote to dial in eq points on the fly. So at those times of harshness, I used to cut back (what I thought to be) the offending area.

I had always been fine with eq in the bass region, as are most here, yet had 'philosophical' objections to the use of eq in the full range, mainly based on things of the 'where is the correct point, left ear, centre of forehead, right ear?' type. Because, as we know, the position of the mic makes a huge impact in the upper frequencies.

One night I had a brainwave, and what follows (with hopefully not too boring explanations) is what I found.

Ok, to start, (and hoping I can remember how to load graphs....been a while) you may have to take this on faith, but as I use the deqx I know the speakers are flat and accurate. For the sake of illustration, I just now threw the mic vaguely in front of the right speaker to show my points, but I am in the middle of renos so there are ladders etc everywhere, so 'ignore' the roughness of the graph.

Ok, managed to do that without too much drama, unsmoothed and 1/3 on top of it, right speaker (woofers turned off, won't bother explaining why and we are talking full range anyway)

So (for me at least) that was the starting point, that I know the speakers are flat. Hence, at the LP, any non smoothness can only be due to the room. Stating the obvious I know, but hey. (I emphasise smoothness to avoid confusion with 'flat at the LP' which can imply equal sound levels at all frequencies at the LP)

Here is the bass measurement from LP

But this is what we are interested in.

These are the three measurements across the LP, 1/3 octave. Not a pretty sight!! I usually take (say) five measurements across the LP, but for the illustration now I only did three.

As I say, the room is a mess with stuff everywhere (am building huge bass traps actually!!) so tbh it does not reflect the normal situation. Still, if you can imagine it, the harshness (say) I used to cut back with the remote was around 2k (what most think of as 'bright' etc they usually blame the tweeter....nahh, safe bet number one, it is never the tweeter, always the midrange. You can basically take that to the bank)

Now, this is the 'breakthrough' in my thinking I mentioned before....the 'peak' I used to cut back to cure the 'brightness/harshness' was only a peak because of the room induced dips before it.

Did that make sense?? I found that when I filled in the valleys to make a smooth graph (as we should have because the speakers are flat) it cured the 'brightness'.

So, my goal in doing this is not to 'tailor' the graph so much (tho of course that is perfectly ok if it is your taste) but to simply restore it to what 'should' be it's natural shape, 'perfectly' smooth with the natural high end tweeter roll off.

(it would be a mistake to have 20k at the same level as 2k as 200...ie flat at the LP across all frequencies, that would be horribly bright indeed).

So, heeding the natural high end roll off as natural, my intent is solely to smooth the graph.

Ok, we have the three (or five or whatever) measurements across the LP...and when we look we can see what stays constant and what changes.

I then load them all into the average tab, and apply FULL smoothing to them, and then average them all.

This is for a number of reasons. We only want gentle correction, massaging. Earlier I spoke of philosophical objections, this was one of them. It is a fact that you cannot use drc to do full range correction per se, one glance at an unsmoothed graph will show you why. AND that correction is so intimately connected to that one solitary point in space that anywhere else is very wrong..left ear right ear stuff.

Once we have switched to 1/1 smoothing then we are only doing gentle corrections, and strangely enough it 'forces' you into use only very broad filters! (that's a good thing in case you were wondering)

So go back to the filter adjust tab, and use the eq filters window to work out what filters to apply to the averaged graph.

Again, this is only for the sake of illustration, but here I applied the filters to the average, with (as explained) the sole aim of gently massaging it back to a smooth natural shape.


I now (of course) load those filters into the deqx (you would use whatever unit you have) and redo the measurements across the LP. You will probably find the measured response to not accurately track the predicted response, due no doubt to the fact we have fully smoothed them prior to working out the filters, and any slight change in the frequency in a fully smoothed graph can make a large difference, and the mic will not be in the same spot the second time around.

Whatever, as said before, this is just gentle massaging so it does not matter too much.

So here are the three measurements across the Lp after filters applied

Even now we can see an obvious improvement in the collection of graphs.

So for the final 'check' those measurements are again loaded into the average tab at full smoothing and of course averaged.

Bingo, and it very closely matches the predicted response earlier. So we have used very broad gentle filters to restore the correct balance between the frequencies, and have not limited ourselves to one position in space, presumably the more measurements across the lp (you can go up and down, back and forth as well) will make any correction less severe and more gentle, and more broadly applicable.

Bear in mind that as we have two ears, they can cross compensate a lot with measured discrepencies from ear to ear, so we really do only want gentle corrections.

I have also found that (depending on your chair) by measuring in free space (ie move the chair away) you are more and more only addressing the room. It is your call whether or not you feel you need to correct from the reflections straight off the chair. I find it better to move it away.

I find that tonally it all works much better, more relaxed and less strident (you may have different symptoms of course, as I say I was troubled by 'harshness')

Funnily enough, the real cure for my harshness was not 'cutting back the offending high' but 'filling in the valleys that caused the offending high'.

That was the big counter intuitive surprise for me.

By all means try it for yourself, I make no guarantees that you will like it as much as I did, and if any try it report back the findings good and bad.

I will not be offended!!