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Is this frequency response any good? Audio Interfaces
Old 22nd December 2010
  #1
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Beiteltjie's Avatar
Is this frequency response any good?

I recently (half)finished my control/recording room and downloaded FuzzMeasure to check what's going on. I am waiting for the rear wall panels, but they will only be coming in Jan, so I did some tests in the meanwhile. The room sounds pretty impressive as is already - I have 3 off big 100mm panels in first reflection points on side walls and roof, 2 more 50mm big panels (2.4x1.2m) hanging from the (concrete) roof, but that's about it at the moment. The sound is pretty impressive as is but kind of unpleasing/sterile/harsh. But I can hear stuff I've never heard before! Size of room is 5.6mx3.7mx2.7m.

I don't quite know what to do make of the frequency response graph though - don't know what defines a good frequency response. Any comments?
Attached Thumbnails
Is this frequency response any good?-studio-888.jpg  
Old 22nd December 2010
  #2
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Magickman's Avatar
 

Quote:
Originally Posted by Beiteltjie View Post
I recently (half)finished my control/recording room and downloaded FuzzMeasure to check what's going on. I am waiting for the rear wall panels, but they will only be coming in Jan, so I did some tests in the meanwhile. The room sounds pretty impressive as is already - I have 3 off big 100mm panels in first reflection points on side walls and roof, 2 more 50mm big panels (2.4x1.2m) hanging from the (concrete) roof, but that's about it at the moment. The sound is pretty impressive as is but kind of unpleasing/sterile/harsh. But I can hear stuff I've never heard before! Size of room is 5.6mx3.7mx2.7m.

I don't quite know what to do make of the frequency response graph though - don't know what defines a good frequency response. Any comments?
"Good" would be +/- 5dB. Actually, +/- 5dB would be "really good". +/- 12dB is not so good. Not horrible, but not good.
Old 22nd December 2010
  #3
SAC
Registered User
 

Its impossible to tell from the FR alone..

First, is it made with both speakers playing? If so, it is simply a documentary of a comb filtering lab - as the interaction of two spaced sources superpose (combine) to create polar lobing, whose nulls correspond with comb filtering in the frequency response...

Second, you have some deep nulls outside of the modal region - but it is impossible to tell what is causing them - speakers? crossovers? reflections?

In other words, what you have is a response that shows the interactions of any number of causal factors - none of which we can identify from the frequency response - we simply know that 'something' is happening. So we need to dig a bit deeper to uncover the causal elements.

One powerful way to find out what is causing the comb filtering and thus, armed with the ability to identify and analyze each causal factor, remediate them is:
Using only one speaker at a time, and without moving the mic
, you can recreate the FR and also generate the impulse and then display the ETC response for each speaker to see the causal components that are at play in creating the frequency response anomalies.

Then, after windowing the ETC so that sufficient detail is able to be seen (say 50 dB from the peak & ~40ms from the point of direct arrival), you will be able to start to get an idea of what is causing the anomalies - along with sufficient information to actually identify and resolve the casual factors.

As for any modal issues, a frequency response and then a waterfall plot generated from it, windowed to ~0-300 Hz should show that detail...
Old 22nd December 2010
  #4
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Quote:
Originally Posted by SAC View Post
Its impossible to tell from the FR alone..

First, is it made with both speakers playing? If so, it is simply a documentary of a comb filtering lab - as the interaction of two spaced sources superpose (combine) to create polar lobing, whose nulls correspond with comb filtering in the frequency response...
Er, yes. I was making an awful lot of assumptions here. tutt

My bad.
Old 22nd December 2010
  #5
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Beiteltjie's Avatar
SAC, I actually measured both speakers individually without moving the mic and then took the average of the two measurements. My trial of the software has expired so unfortunately I am limited to 2 measurements at a time and cannot do the reverb time and waterfall plots. If you tell me they are required to do the proper measurement then I will purchase the software. I also noticed that I forgot to change the mic to omni. Here is the measurement in omni, but I'm afraid it does not look much better. Note that I had very little smoothing on the first graph
Attached Thumbnails
Is this frequency response any good?-studio-888b.jpg  
Old 22nd December 2010
  #6
SAC
Registered User
 

Alternatives to whatever you are using now -
RoomEQWizard - free - and that's hard to beat.
ARTA, unlicensed it is fully functional, but you will not be able to save results - but you could use any number of tools to make screen captures - you just won't be able to post process... {And at ~79 Euros for the licensed version (saving enabled) it is possibly the best buy in the entire industry based upon price vs capability.}
Even Easera has a 30 day trial available.

But REW may be the easiest to learn and source and should do fine for your purposes.

Averaged responses do not help - especially as we are only concerned with the local listening position - they just add more variables and less specific detail making isolation and identifying causal factors more difficult. Run them individually - and the individual ETC response will allow you to isolate and identify the reflection paths that cause the destructive interactions.

Oh, and yes - an omni is important is one is attempting to ascertain the speaker-room interaction! heh
Old 22nd December 2010
  #7
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I am on Mac and use Apogee Ensemble so can't connect to a PC. I will look into REW - as far as I understand mac is supported. I will redo the frequency responses for individual speakers. Do you know if you can do a microphone frequency response adjustment on REW?

OOPS! see REW is PC only. What other options are there for Mac?
Old 22nd December 2010
  #8
SAC
Registered User
 

Quote:
Originally Posted by Beiteltjie View Post
... REW is PC only. What other options are there for Mac?

What Victor said.

Or, VMWare Fusion or Parallels and Windows.

Or simply buy FM! That one purchase will bring a larger return on investment than any other piece (or pieces of gear) you buy!

Its funny how folks in general have no problem buying any amount of exorbitantly priced hardware, but balk at an investment in the acoustics of their room! And without such treatment, all that fancy hardware will still sound mediocre.
Old 22nd December 2010
  #9
Gear Addict
 

If you're serious, purchase Fuzzmeasure, and a decent SD omni.

REW may work, but has issue with some OSX iterations via a firewire interface.

[QUOTE]Its funny how folks in general have no problem buying any amount of exorbitantly priced hardware, but balk at an investment in the acoustics of their room! And without such treatment, all that fancy hardware will still sound mediocre./QUOTE]

So true..
Old 22nd December 2010
  #10
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Magickman's Avatar
 

Agreed! Buy FuzzMeasure. You won't be sorry. It's so easy to use!

-MM
Old 2nd January 2011
  #11
Gear Maniac
 
Beiteltjie's Avatar
Okay, so I purchased FuzzMeasure and here is the waterfall. How is it looking? It looks to me like there is a problem around 60 Hz.

By the way, REW did not play nicely with my Apogee Ensemble - bombed it out a few times.
Attached Thumbnails
Is this frequency response any good?-888-waterfall.png  
Old 3rd January 2011
  #12
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Magickman's Avatar
 

Quote:
Originally Posted by Beiteltjie View Post
Okay, so I purchased FuzzMeasure and here is the waterfall. How is it looking? It looks to me like there is a problem around 60 Hz.

By the way, REW did not play nicely with my Apogee Ensemble - bombed it out a few times.
You need to narrow your view a little so we can see more detail in the modal range.

Try adjusting your waterfall settings more like this:


Is this frequency response any good?-watefall-settings.jpg


And then post the results.
Old 3rd January 2011
  #13
Gear Addict
 

What about the magnitude??

Its been suggested that -60, -70 is good?
Old 3rd January 2011
  #14
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Quote:
Originally Posted by tonio View Post
What about the magnitude??

Its been suggested that -60, -70 is good?
That really depends on the ambient noise in your room. For most, -60dB to -70dB is a little low. In my room, -50dB give a good clean graph.

Of course YMMV.
Old 3rd January 2011
  #15
Gear Addict
 

True MM. I shoot @ -60, -70 to check any pesky noise, and bring it back to -55 or so to get a good reading.
Old 3rd January 2011
  #16
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Beiteltjie's Avatar
Here is the graph with settings as suggested.
Attached Thumbnails
Is this frequency response any good?-888-waterfall-lf.png  
Old 3rd January 2011
  #17
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Jens Eklund's Avatar
-65 to -70 dB usually works well if not a very noisy room.
Old 3rd January 2011
  #18
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Beiteltjie's Avatar
By the way, the waterfall above is using one speaker alone as suggested.
Old 3rd January 2011
  #19
Gear Guru
Skill

B, Glad to hear you bought FM. FuzzMeasure is deceptively easy to use. Point and shoot. Very soon you will begin to see how really 'Pro' it is also.
Your graphs seem a little strange, no first frequency in the FR and that Waterfall appears to start at 50Hz.
30-300 is good for Waterfalls.
That later FR looks not too bad at all to me by the way.
Might be worth your while reading the Basic Acoustic Measurement Sticky, it is very FM biased. I use REW now, on a Mac. It has more facilities than FM but the interface is a bit foreign to us Mac users. FM is a a lot easier. BTW I believe two individual speaker measurements, then averaged, is a very good way to measure FR. I sometimes move the mic to two different spots (similar to where the two ears will be) to get even closer to the listening reality.
Don't be afraid to use that threshold thing to get a good view.
I also end up at -50, sometimes -45. Many people work at a less than pro level these days with noisy rooms, computers, drives, even interfaces have fans in them.
Don't forget to move away from the mic when taking measurements.

DD
Old 17th February 2011
  #20
Gear Maniac
 
Beiteltjie's Avatar
Okay, so I've finally put in more trapping on the rear wall and got cylindrical bass traps in the corners adjacent to the monitors and redid the waterfall. It looks 'n lot better, but there is a big peak at about 55Hz. I suspect it might be from the adjacent bathroom, which is all concrete and plastered brick. I can hear ringing coming from there on low frequencies. I probably need to install a proper isolating door, if this is causing the problem. Could this be the cause?

In the meanwhile, is there something to be done about this?
Attached Thumbnails
Is this frequency response any good?-waterfall.png  
Old 17th February 2011
  #21
Gear Guru
Hum

Well, a hum from the bathroom eh? Air freshener?

Unfortunately FM is doing it's job faithfully and truthfully. That's a nasty looking boom. Your treatment may not be in the right place. Play sinewaves around 50. Signalsuite is great for this, but a Generator plug in your DAW may do. Tune in slowly and carefully to get the resonance exactly on. You will hear it distinctly. Walk about the room finding peaks and nulls. Take a listen in the bathroom. You should be able to hear the source of your boom easily. Don't forget to listen at the floor and ceiling, particular the corners.

REW uses Java. Apples conversation with Java doesn't do multichannel interfaces I am told. I can't get REW5 to talk properly with a Digi HD192. That is probably why you had difficulty with the ensemble.
If you want to try it further, select 2Ch interface in the Audio Midi setup, if you can.

DD

DD
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