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St0rMl0rD 11th August 2019 09:22 AM

Looking for feedback on my measurement results
 
3 Attachment(s)
Hi guys,

So I got my Behringer ECM8000 and did a measurement test with Rode's FuzzMeasure yesterday, and got the response below. I have the space acoustically treated (it's 4,4 x 3,75 x 3m ) with 8 acoustic absorbers and 4 bass traps (front L and R corners, stacked up - I don't have space for them in the back corners, as it's a living room/studio situation).

I have compared my response with a response of the KRK Rokit 6 G3's that I found online, and noticed that the graphs are pretty much idential (apart from the bass thing where my bass traps kick in at 100 Hz). I'll be switching from KRK's to Adam A7X's soon, but was still curious what you think about this response graph. Now at this test, I pointed the mic at the speakers, and not the ceiling - should I have done that instead?

Thanks!

johannburkard 13th August 2019 02:21 PM

Quote:

Originally Posted by St0rMl0rD (Post 14143224)
Now at this test, I pointed the mic at the speakers, and not the ceiling - should I have done that instead?

For an omni microphone which I hope you have used, it doesn't matter.

johannburkard 13th August 2019 02:23 PM

I haven't used FuzzMeasure but it looks like you don't have the room modes under much control, even above 100 Hz. There's also interferences... I have to ask: How deep are your absorbers?

St0rMl0rD 13th August 2019 04:14 PM

2 Attachment(s)
Yeah, I did the same test with the mic pointed upwards, got a similar but a bit flatter result:

St0rMl0rD 13th August 2019 04:15 PM

My absorbers are 7 cm or so thick, with an extra 5 cm away from the walls. The bass traps are 40 cm deep.

Soundman2020 13th August 2019 08:09 PM

Quote:

Now at this test, I pointed the mic at the speakers, and not the ceiling - should I have done that instead?
There is a difference when the mic is angled, as you already discovered. Intuitively, you'd think that an omni mic would show no difference, but so many things in acoustics are not intuitive, and this is yet another of those things!

A simple (but incomplete/"sort of but not quite") explanation is this: A perfect omni mic would detect only the pressure variations around it, equally in all directions... But the pressure variations are NOT really equal in all directions! First, there's the "ambient" pressure of all sounds in the room, often referred to as the "reverberant field"... and in a perfect room it would arrive at the mic with equal probability from all angles, and that's what you are actually trying to measure here. However, it's a fools errand, because in a small room there is no such random field! It does not exist. It's not random. That only happens in a very large room. Small rooms don't have true reverberant fields... but that's sort of splitting hairs, and doesn't really matter, because what you REALLY want to measure, is whatever is actually happening in the room, regardless of whether or not is is a truly random, reverberant field: it is what it is, and you want to measure it, and you'd think that sticking a true omni mic in that field would capture it perfectly, because it's just pressure changes arriving from all over, and omni mics don't favor any particular direction, so it shouldn't matter which way you point the mic... except that it DOES matter, because... in addition to the reverberant field that is hitting your mic from all angles sort-of evenly, there's also the DIRECT pressure wave being emitted by the speaker, which travels as a spherical wavefront. If your mic is pointing towards that wavefront, so that it hits the mic capsule "head on", then the mic picks up the direct pressure wave strongly. On the other hand, if your mic is pointing at a steep angle such that the pressure wave hits it side-on, not head on, then the capsule doesn't "see" that pressure wave the same. In summary, the mic always picks up the ROOM sound the same, regardless of which way it is pointing, because that sound field is arriving from all angles the same. But the direct sound from the SPEAKER arrives from only one single direction, and if you point the mic in that direction, you pick it up better than if the mic is pointing tangential to the wavefront.

Short story: if you point the mic at the speakers, you are measuring more of the speakers, less of the room. If you point the mic tangentially, you are measuring more of the room, less of the speakers.

This isn't about whether or not the mix is truly omni: it's about the speakers vs. the room.

This is why you often see the recommendation to aim the mic at the ceiling if you want room measurements, or directly at the speaker if you want to measure the speaker response and plan to gate out the room response ("window" it). The problem comes when you want to measure both speakers individually, and also together: Where do you point the mic then? Do you flip int back and forth, pointing at the left speaker to measure that, then re-pointing to the right or that, then in the middle for both? Or do you just leave it in the middle and not get true on-axis? Hmm.... And iff you do decide to flip the mic around all over the place, how do you ensure that it gets back to the exact same spot for every subsequent measurement? Hmmm...

Personally, since I'm usually measuring rooms, not speakers, I angle the mic upwards at about 60-70° degrees, rather than vertical, and this angle is for other reasons that are too complex to go into right now. But that does tend to give the best actual measurement of the room. Assuming that you are trying to treat your room and want to know what it is doing, I'd make the same suggestion here: angle your mic upwards about 70°.

Yeah, not a very good explanation, I know, and the purest acoustician will be rightfully shouting "Not true! That's not really the way it works! It's much more complex!", but I think it's a useful mental picture to help understand the issue.

- Stuart -

johannburkard 13th August 2019 08:19 PM

Quote:

Originally Posted by St0rMl0rD (Post 14147065)
My absorbers are 7 cm or so thick, with an extra 5 cm away from the walls. The bass traps are 40 cm deep.

You can see that that's not helping too much in the bass.

St0rMl0rD 14th August 2019 02:50 PM

Quote:

Originally Posted by johannburkard (Post 14147455)
You can see that that's not helping too much in the bass.

I know, but you say that there's also some imbalance in the higher frequencies. I know that switching to ADAM Audio A7X's will help a lot with the bass, but I'm curious how I could attend to the higher frequencies as well.

johannburkard 14th August 2019 03:25 PM

Quote:

Originally Posted by St0rMl0rD (Post 14148723)
I know, but you say that there's also some imbalance in the higher frequencies. I know that switching to ADAM Audio A7X's will help a lot with the bass, but I'm curious how I could attend to the higher frequencies as well.

If you are switching speakers, why worry about the results you have with your old ones?

St0rMl0rD 14th August 2019 05:38 PM

Quote:

Originally Posted by johannburkard (Post 14148769)
If you are switching speakers, why worry about the results you have with your old ones?

Wanna learn as much as I can on the subject; my best friends are currently in the process of building a new rehearsal space from scratch, so any knowledge will come in very handy :)

johannburkard 14th August 2019 07:18 PM

The hole at around 1-2 kHz may be you putting the microphone below or above the acoustical center of the speaker. Many speakers have a high directivity around the crossover point. On my Genelec 8350s, this is at 1.8 kHz for example.

akebrake 17th August 2019 03:07 PM

Export of IR
 
Quote:

Originally Posted by St0rMl0rD (Post 14149004)
Wanna learn as much as I can on the subject; my best friends are currently in the process of building a new rehearsal space from scratch, so any knowledge will come in very handy :)

If you upload your Fuzz measurements as wav files here we can open them in REW, dig deep and share some knowledge. kfhkh
Look in the Fuzz menu for "export"

Best