Need Help to understand what the graphic shows!

[ocilsound]

Hi,

I have a small treated Control Room and just got this measurement. But I am not totally sure how to analise it.

This was taken from the "sweetspot". I used Fuzzmesure, Pro Tools HD, DBX Microphone, Dynaudio BM15 Speakers.

Can someone help me or you need more info to help me out here.

[Soundman2020]

Hi "ocilsound", and welcome!

But I am not totally sure how to analise it.

It shows only a small part of the story, and not enough to draw conclusive conclusions. It shows the room response only in the frequency domain, but the time domain is just as important: How the room reacts to the sound after it stops playing. You should also look at the impulse response and waterfall plots to learn about the time domain.

From the pure frequency response point of view, that isn't too bad, and is pretty typical of a home studio. It shows that your frequency response is within roughly +/-9 dB from about 60 Hz through to 10 kHz, with what seems to be some modal issues, ringing, comb filtering, and reflections going on, but without the data on the time domain, one can't say much more at all about that.

So please post some other graphs, as well as a few photos of the room, plus the dimensions of the room (all three directions) and details of the treatment you already have in there.

Also, please identify which speaker that graph is for (left or right) and post the same set of graphs for the right speaker too.


- Stuart -

[ocilsound]

Hi Stuart,

Thanks a lot for your reply.

Here's some more measurements:

Control Room Layout.jpg

Octave Band RT (EDT).png

Sweetspot L Speaker.pdf

Sweetspot R Speaker.pdf

Sweetspot L+R Speaker.pdf

Octave Band RT (T20).png

Octave Band RT (T30).png

Cumulative Spectral Decay1.png

Cumulative Spectral Decay2.png

Hope it gives you a better idea!

[Soundman2020]

Hope it gives you a better idea!

Actually, that's more confusing than before! Those graphs don't even agree with each other. For example, one graph shows a decay time of well over one second at 32 Hz, yet another graph shows less than 200ms decay at 32 Hz. They cannot both be right! There might well be differences between different calculation methods, and difference between speakers, but not that big. Then to confuse things even more, the waterfall plots don't seem to show any decay at all, either at 32 Hz nor at any other modal frequency: the decay looks flat, to me. Add to that the curious situation of having a much higher decay time for 4k (290 ms) than for 250 Hz (70 ms)... That's hard to explain, unless there are some pretty serious treatment problems in the room.

I suspect there's something wrong with the way the measurements were taken, or with the way they were processed. I'm not familiar with Fuzzmesure, so I can't tell what you need to do to get valid readings, but there definitely seems to be an issue with the way those graphs are presenting the data.

Is there any chance you could try again using REW (Room EQ Wizard - it is a free download from Home Theater Shack), and post the data file here, so we can take a look at it, and do the analysis in more detail.

I'm also wondering if those readings might have something to do with the rather, ummm... "unconventional" shape of the room: I have never seen curved soffits before, and that flies in the face of everything I thought I understood of soffit design theory. Curved surfaces focus sound at a point, which is generally very undesirable in a critical listening room. The sudden transition at the edges of the soffits also looks like a major source of edge diffraction, which is part of what soffits are designed to eliminate, so that has me rather puzzled too. Then there's the location of the listening position itself, and the position and orientation of the speakers.

I'm just not grasping the design concept here at all. It doesn't seem to fit any category that I'm familiar with.

What is the basic design concept that was used here? I thought I was pretty much up to date on design concepts, but I guess not: this is, indeed, unusual, and I can't see how it can work, acoustically.

Would it be possible for you to post some photos of the room? I'm intrigued.

Also, what is your impression of the room? How does it sound when you try to mix? Do you have a crystal clear, accurate, well defined sound stage? Good stereo imaging? Is the room neutral, or "boomy", or "tinny"?

Sorry for all the questions: just trying to get my head around a design concept that I've never seen before, and doesn't seem to make much sense.


- Stuart -

[ocilsound]

Hey Stuart,

Well I will try to redo the measurements with REW. But it's just a "pita" to have it working with Pro Tools HD. I haven't done this before so I am not totally sure if I printed the right stuff. The frequency graphics I think it's right though.

The most problem I have right now is with some cancelling in the Lo Freq area in the "sweetspot". My image in the stereo filed seems to be very solid and clear.

I can send you the project if you want to understand it a little more.

Here's some pics of it:

PANORAMICA 02.jpg

IMG_3802 copy.jpg

IMG_3766_copy.jpg

[Soundman2020]

Here's some pics of it:

The plot thickens! The actual room does not match the drawings. The monitors are not soffit mounted, but rather are sitting on top of the bridge, so you aren't getting the benefits of the soffit, and are getting the usual artifacts from first-order reflections off the face of the console. There also doesn't seem t be much broad-band bass trapping in the room, although there might be: the diagram seems to show it, but it's hard to figure out form the photos if that's what they actually did.

The most problem I have right now is with some cancelling in the Lo Freq area in the "sweetspot".

That might be due to the lack of bass trapping, or it more likely it is due to the location of the listening position and also the curved front wall. It seems that your listening position is very close to 50% of the room depth (front to back), which is the worst possible place: that's the location in the room where ALL of the room modes are either at full peak or at null, so it would not be surprising for you to notice some low frequency cancellation there, and that would explain the rather large peaks and dips below 500 Hz. on the frequency response graph.

I can send you the project if you want to understand it a little more.

Sure, that would be great. But I'd suggest that you PM me with that, rather than post it in public, since it seems to be a paid design job, and the designer might not want his work in the public domain. So send me a PM (private message) with that, and I'll take a look.

The room looks very nice, by the way: It's just that some of the things visible in there don't seem to fit the common principles of acoustic design. So if the designer based this room on some new principle, then I'd need to understand that before I could comment intelligently on how to improve the issues you are having. Obviously, there is something wrong, or you would not be having those issues!

- Stuart -