My view on the 'ideal' graphs, and a question about measuring them
hugohuijer
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#1
28th December 2012
Old 28th December 2012
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My view on the 'ideal' graphs, and a question about measuring them

Okay,

I have done a fair bit of research about (home)studio acoustics. I am currently building 12 x 20cm deep panels for my small room, and I have been thinking about buying a mic for measuring the frequency response.

There is a topic on here about the 'ideal' frequency response, and what should be the perfect result for any treated room. In my opinion, there was no clear answer (I've read the first 2 pages..).

I think the perfect frequency response could be measured when you do the measurement outside. Think of a situation where there are no walls, ceilings, or floors, and no sounds. A test would show the perfect frequency response, right?

On the other topic someone mentioned using a headphone (for monitoring), placing it on your mic, and then run the test. This would leave out most of the room's acoustics, so I thought of this would give a proper 'baseline' for me to look up to (sorry for my language, I'm from the Netherlands).

Since I'm a just a poor student, I am refusing to spend 50 quid on a measurement-mic just for a some measuring. I know it will eventually be worth it, but I think I have a better alternative. Here's the setup:

I already have a Rode NT1a, so how about I place my headphones on the rode NT1a, like the guy in the other topic mentioned. This would give me the 'baseline' frequency response that I'm looking for. It would be different when compared to a measurement with a mic build specifically for measuring, but since I'll be doing all my measurements with the same mic, I can compare the measurements to each other. In this way, it doesn't matter wether or not the mic is build for measuring, right?

I think of it like some mathematical equation. When (A * B) + X = (C * D) + X you can just leave the X's out of the equation. Think of the X's as of they are the mic's incapability to measure room acoustics. Since the 'baseline' frequency response is measured with the same mic as the actual room measurement, I will be allowed to compare the two, and get a proper result placing my acoustic panels.

I hope some people are able to understand my what I just said, and I defenitely hope I'm not talking complete bullshit.

Can anyone give their opinion on what I just typed?

Thanks in advance
#2
28th December 2012
Old 28th December 2012
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The perfect freq response is perfectly flat 20-20k. This is simple and rather obvious I think. What is not simple or obvious is how to achieve it (get close to it) in an enclosed space.
hugohuijer
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28th December 2012
Old 28th December 2012
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I agree with you that that is the perfect response, but that is not realistic. I've never seen a perfectly flat frequency response, and I guess no studio around the world even comes close to that.

So what I'm trying to say is that with the experiment I explained above, I can get a realistic frequency response measurement with the Rode NTA1, thus moving my panels so that I get as close to the ideal frequency response as possible with my room
#4
28th December 2012
Old 28th December 2012
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The problem with using your mic is its transient response, especially in the higher frequencies. Most measurement mics are very small diaphragm, smaller responds better because less mass.
#5
28th December 2012
Old 28th December 2012
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Quote:
Originally Posted by hugohuijer View Post
I agree with you that that is the perfect response, but that is not realistic. I've never seen a perfectly flat frequency response, and I guess no studio around the world even comes close to that.

So what I'm trying to say is that with the experiment I explained above, I can get a realistic frequency response measurement with the Rode NTA1, thus moving my panels so that I get as close to the ideal frequency response as possible with my room
By close, I am not sure what you mean. But the best studios get close to 20-20k +/- 3 db @ 1/24th octave smoothing. If you want to get flatter than that, then tell the rest of us how you did it

As far as your experiment goes, frankly, I dont understand what you mean. Going outside or sticking a mic in a headphone is going to accomplish what?

Maybe your trying to determine if your mic setup is flat?
hugohuijer
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28th December 2012
Old 28th December 2012
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Quote:
Originally Posted by jim1961 View Post
As far as your experiment goes, frankly, I dont understand what you mean. Going outside or sticking a mic in a headphone is going to accomplish what?

Maybe your trying to determine if your mic setup is flat?
I am thinking it will give me a frequency response with little to none of the acoustical problems my room contains. This may be were I am completely wrong though

But if I get a frequency response with no room influence with the Rode NTA1, I'll be able to compare any measurements done with the NTA1 with that one, so that I can get the best out of my acoustic absorbers.
hugohuijer
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28th December 2012
Old 28th December 2012
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And theoretically, if you're in a complete open space, like literally SPACE, with no reflections and just no room dimensions, you 'should' get a perfectly flat frequency response, right?

So that's what I'm trying to recreate with the headphone/mic setup, kind of...
#8
28th December 2012
Old 28th December 2012
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Quote:
Originally Posted by hugohuijer View Post
I am thinking it will give me a frequency response with little to none of the acoustical problems my room contains. This may be were I am completely wrong though

But if I get a frequency response with no room influence with the Rode NTA1, I'll be able to compare any measurements done with the NTA1 with that one, so that I can get the best out of my acoustic absorbers.
Maybe I am still not getting what you are saying, but it seems to me measuring your room with the mic is the only way your going to know what your room is doing. Add absorbers and measure again. Compare the responses. Keep changing the room until you get the response you want.

If your mic/software setup is known to be flat, then comparative data isnt necessary.
jwl
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28th December 2012
Old 28th December 2012
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When measuring rooms, I'm generally interested in 400Hz and down since that's where the biggest (and hardest to solve) problems will be.

Also, before/after measurements are much more useful, I find, than absolute frequency response graphs, which change from point-to-point throughout the room anyway.

Bottom line, use the best mic you have available to you. For me, that's a $30 cheapo measurement mic, that has a flat frequency response and an omni pickup pattern. If your NT1A is your best option, then go with that. It won't be as accurate but it should still give you some useful info, especially comparing before/after treatments.
#10
28th December 2012
Old 28th December 2012
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Quote:
Originally Posted by hugohuijer View Post
Okay,

I have done a fair bit of research about (home)studio acoustics. I am currently building 12 x 20cm deep panels for my small room, and I have been thinking about buying a mic for measuring the frequency response.

There is a topic on here about the 'ideal' frequency response, and what should be the perfect result for any treated room. In my opinion, there was no clear answer (I've read the first 2 pages..).

I think the perfect frequency response could be measured when you do the measurement outside. Think of a situation where there are no walls, ceilings, or floors, and no sounds. A test would show the perfect frequency response, right?

On the other topic someone mentioned using a headphone (for monitoring), placing it on your mic, and then run the test. This would leave out most of the room's acoustics, so I thought of this would give a proper 'baseline' for me to look up to (sorry for my language, I'm from the Netherlands).

Since I'm a just a poor student, I am refusing to spend 50 quid on a measurement-mic just for a some measuring. I know it will eventually be worth it, but I think I have a better alternative. Here's the setup:

I already have a Rode NT1a, so how about I place my headphones on the rode NT1a, like the guy in the other topic mentioned. This would give me the 'baseline' frequency response that I'm looking for. It would be different when compared to a measurement with a mic build specifically for measuring, but since I'll be doing all my measurements with the same mic, I can compare the measurements to each other. In this way, it doesn't matter wether or not the mic is build for measuring, right?

I think of it like some mathematical equation. When (A * B) + X = (C * D) + X you can just leave the X's out of the equation. Think of the X's as of they are the mic's incapability to measure room acoustics. Since the 'baseline' frequency response is measured with the same mic as the actual room measurement, I will be allowed to compare the two, and get a proper result placing my acoustic panels.

I hope some people are able to understand my what I just said, and I defenitely hope I'm not talking complete bullshit.

Can anyone give their opinion on what I just typed?

Thanks in advance

First you talk about "building 12x20cm deep panels" for your "small" room. So we know very little about your room dimensions or what you are building?

When you talk about measuring outside I think you are alluding to anechoic conditions ie no reflections? In general loudspeaker and microphone tests would be carried out in these conditions to create data sheets that isolate the response of the transducer being tested. However, any musician or engineer will tell you that these are not subjectively pleasant conditions to create or mix music in, despite being intrinsically "flat".

You "don't want to spend £50 on a measuring mic" but you have a reasonable quality condenser mic. Fine, as long as you are only interested in comparable (before and after treatment) measurements then so be it. We are not talking about lab results here. Only interest, as far as I can see, is.... are you making a difference, and is it in the area that you want to change?

I regard your thoughts on putting the headphones on the microphone and measuring the overall transfer response as pointless, on several levels. What exactly are you trying to achieve? When you have built and installed your treatment panels and then presumably measure your room, how is the headphone measurement going to help you?

Quote:
Originally Posted by hugohuijer View Post

I think of it like some mathematical equation. When (A * B) + X = (C * D) + X you can just leave the X's out of the equation. Think of the X's as of they are the mic's incapability to measure room acoustics. Since the 'baseline' frequency response is measured with the same mic as the actual room measurement, I will be allowed to compare the two, and get a proper result placing my acoustic panels.
The mic is not "incapable of measuring room acoustics" as you put it. The "baseline frequency response" of you measuring your headphones is not going to be of any extra help in room acoustic measurements. If you really want to adjust your room measurements then you could allow for the response of the microphone (from the manufacturers data sheet), however, in the overall scheme of things this is minimal.
hugohuijer
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28th December 2012
Old 28th December 2012
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All the posts above make it pretty clear to me that I still am a noob when talking about room acoustics. I didn't know manufacturers provided their own frequency response charts for their mics, so in that case, there is no need for me to test the thing with headphons like I was trying to explain.

Anyway, I'm going to build 12 panels: 1200 * 600 * 190 milimeters.

I've added some sketchup drawings that I made a while ago, so you guys get the idea. You can now also see how shitty my room actually is









I first had the intentions to make panels with different depths, that's why I made them blue/red. I've decided to just make them all 190 mm deep.

Hope this clears some things up.

I will be just be placing my panels with the help of my Rode NTA1 measurement results, just checking what gives me the best results.

All I was trying to get with my headphone 'experiment' was something to compare my results with. But if I can find something from the manufacturer ,like a frequency response chart, then that will be the option to go with.
hugohuijer
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28th December 2012
Old 28th December 2012
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