Modal ringing and positioning

[SaSi_SiDi]

You mentioned the graphs were "fully smoothed, would be a total mess with five measurements otherwise". How wide is the smoothening? Take one of the measurements and apply very little averaging. If it's a mess with peaks and valleys, then this simply presents the issue with bass response due to room modes.

[terry j]

Originally Posted by SaSi_SiDi

You mentioned the graphs were "fully smoothed, would be a total mess with five measurements otherwise". How wide is the smoothening? Take one of the measurements and apply very little averaging. If it's a mess with peaks and valleys, then this simply presents the issue with bass response due to room modes.

The first graph had full 1/1 smoothing applied, even so we can see that a) the bass response stays remarkably the same (even tho across a span of two feet, remember the question is about 'moving the mic two inches'), and b) even at 1/1 smoothing, the higher frequencies (as expected) do vary greatly.

So the starting point for my query is that moving the mic two inches is simply not that relevant in the bass region where most eq is used.

the second graph has NO smoothing whatsoever, and I 'avoided' all the comb filtering by only showing up to 200 hz. Again we see the bass hardly changing across the two foot span, and it could be argued that any changes that are there are due to the very windy conditions last night, or perhaps even normal measurement to measurement variation (?).

Anyway, unless I am missing something obvious, I find the argument (in the bass region) that moving as little as two inches (or whatever) completely undoes the benefits of eq less than compelling.

(ohh, and for clarification, I forgot to mention that these graphs were generated with eq applied as normally used for listening)

[Ethan Winer]

Originally Posted by terry j

fully smoothed

Right, and that's the problem. I already measured what you want to see, though it's for a different article about something else entirely:

A common-sense explanation of audiophile beliefs

If a room has a lot of bass traps, there's much less change over small distances. But with no traps Figure 1 shows a 3 dB change as low as 42 Hz over 4 inches, and much more change at higher bass frequencies.

--Ethan

[terry j]

gee, my explanations must be more obtuse than I think???

I thought it was clear that the second graph was UNSMOOTHED??? And as it only went to 200 hz then we can focus on the bass area.

So try this one, luckily the program is still open ha ha



no smoothing, but traces seperated for clarity.

The trouble is, I do not see any substantive change at all over a two feet span, in the bass region I mean. The slightest change in mic position will and DOES produce large changes in the upper frequencies, as to be expected from the size of the wavelengths involved.

Note that I am not trying to make an argument against bass trapping, lest you think I am. Indeed that is the reason I have joined this forum to treat the room as best I can (just started cutting wood for my traps last night actually!!)

But I have seen this argument used against eq often, 'it might be good for that ONE position in space, but as soon as you move the slightest it all goes to shit'. Oh, and I also think I grasp why it may not be a good idea at all to use eq when MIXING music etc, so be aware that my examples are only from listening at home to music.

I have absolutely no idea of what happened when you ran those tests Ethan, but TBH I have never seen changes in the bass response such as you describe by simply moving two inches, and luckily I happened to have run these series of measurements a couple of nights ago, AND had them still open.

And here they are.

With or without eq, would not (if true) the argument 'move your head two inches' and you will get major changes in the bass apply to all situations? What I mean is, WHY does moving your head two inches (with eq) produce poor results yet moving your head two inches (without eq) not produce poor results? *I know that you will say, and I accept, that with treatment the peaks are reduces and the nulls filled in, so we'll just do the comparison between no eq and eq without treatment ok?*

The point is (and by far the vast majority of people do not use eq OR treatment) we simply do NOT hear these vast changes from moving your head a few inches, no matter what the response may or may not look like, yet suddenly we are expected to believe that when we use eq the slightest change in head position produces unwanted changes.

I do not buy it for a second. I have not read your link this morning, but am pretty sure I have read it, (yet will do so again later) and suspect it talks about comb filtering being at the bottom of heard changes by audiophiles such as getting up and swapping cables (???). Personally (if that is the one) I have found that explanation a bit simplistic tho no doubt some elements of it could apply.

I think a much truer explanation of why audiophiles hear things change is that, basically, they are idiots. Some, as you are well aware, can hear when a bottle of blue water is present or not present in the listening room.

As I say, idiots.

EDIT is THIS the source of our conflict?? From your article..16 by 11-1/2 by 8 feet high.

My room is much larger than that.

[Hypagen]

Originally Posted by Ethan Winer

Right, and that's the problem. I already measured what you want to see, though it's for a different article about something else entirely:

A common-sense explanation of audiophile beliefs

If a room has a lot of bass traps, there's much less change over small distances. But with no traps Figure 1 shows a 3 dB change as low as 42 Hz over 4 inches, and much more change at higher bass frequencies.

--Ethan

That was a very interesting article, I'd not read that one before. I can see audiophiles everywhere ordering their modified dentists chairs to maximise the chances of experiencing the same sweet spot everytime they listen to music........well mines on order anyway!

[Ethan Winer]

Originally Posted by terry j

I thought it was clear that the second graph was UNSMOOTHED???

Sorry, I missed that totally.

I do not see any substantive change at all over a two feet span, in the bass region I mean ... EDIT is THIS the source of our conflict?? From your article..16 by 11-1/2 by 8 feet high.

The size of the room matters a lot, and so does the number of bass traps already present. In my Believe article, Figures 1 and 2 were measured in the 16 by 11 room with absolutely no treatment. But figure 3 is from my home studio, which is about 34 by 18 by 12 feet and has a lot of bass traps.

Since 99.99 percent of audiophiles don't have even one bass trap, and 99.90 percent probably never even saw one, I'm confident my article is still valid.

(BTW, that's a joke. I'm sure that at least 10 percent of audiophiles know what a bass trap is, even if they don't actually own any.)

--Ethan

[Weasel9992]

Originally Posted by Ethan Winer

(BTW, that's a joke. I'm sure that at least 10 percent of audiophiles know what a bass trap is, even if they don't actually own any.)

Frank

[SaSi_SiDi]

Originally Posted by Ethan Winer

Sorry, I missed that totally.

The size of the room matters a lot, and so does the number of bass traps already present. In my Believe article, Figures 1 and 2 were measured in the 16 by 11 room with absolutely no treatment. But figure 3 is from my home studio, which is about 34 by 18 by 12 feet and has a lot of bass traps.

Since 99.99 percent of audiophiles don't have even one bass trap, and 99.90 percent probably never even saw one, I'm confident my article is still valid.

(BTW, that's a joke. I'm sure that at least 10 percent of audiophiles know what a bass trap is, even if they don't actually own any.)

--Ethan

An audiophile friend of mine, you know, the kind of people that buy expensive cables and break them in for a month or so, has a basement listening room that is "L-shaped", with plastered concrete walls, tiles on the floor and a 7" plastered ceiling. The listening sofa is flush against the back wall. He was bragging about the sound quality of his system and how strong bass was.

[Ethan Winer]

^^^ Yes, that's the type of audiophile I was referring to.