Flatten Monitors Response - Recommended Software?! Filter Impulse Response?
steve_lambert
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#1
26th March 2012
Old 26th March 2012
  #1
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Thread Starter
Flatten Monitors Response - Recommended Software?! Filter Impulse Response?

Hello everyone,

I am looking for a program that allows me to measure the
frequency response of my monitors and gives me a filter impulse response
that compensates for the measured response, so I can load that response
into my IR-Plugin in Pro Tools and get a nearly flat speaker response. I have got a special
measuring microphone already. I tried Room EQ Wizard and measured the frequency response of my monitors with it but I don't know how to generate
a filter IR File (.wav) based on that response to make it flat.
I believe the program can't do that. It only offers some 20 bands EQ which is not what I need. Is there any other software on the market which can help me to get what I want?

regards, steve
#2
27th March 2012
Old 27th March 2012
  #2
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jhbrandt's Avatar
 

Steve,

While programs like this are life-savers for live events and concert sound, I do not recommend them for critical mix situations except for steady-state problems. ie; when correcting speakers for flush mounting.

You must treat your room to a) eliminate early reflections and b) dampen the ringing time of the low frequency so that it does not mask decay of the source.



Cheers,
John
#3
27th March 2012
Old 27th March 2012
  #3
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DanDan's Avatar
Eq

Room treatment has a much more profound effect than eq.
However it is called RE Wizard for good reason.
If you get into to it REW can identify if particular anomalies will be susceptible to Eq, or not.
The very low frequency Length mode is worth a look.
I wouldn't go beyond 2 or three filters.
REW can generate Eq parameters and predict the effect.
Forget the IR's, try a decent parametric.
A HF roll off can be helpful, using the speakers onboard Eq or the same Parametric with a HF shelf.
See Understanding RTA at studiotips.com

DD
#4
27th March 2012
Old 27th March 2012
  #4
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fastlanestoner's Avatar
 

A piece of software may give you a little insight into your monitoring deficiencies, but it's not gonna fix your room.
#5
27th March 2012
Old 27th March 2012
  #5
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Glenn Kuras's Avatar
 

Quote:
Originally Posted by jhbrandt View Post
Steve,

While programs like this are life-savers for live events and concert sound, I do not recommend them for critical mix situations except for steady-state problems. ie; when correcting speakers for flush mounting.

You must treat your room to a) eliminate early reflections and b) dampen the ringing time of the low frequency so that it does not mask decay of the source.



Cheers,
John
To me the highlighted part is the most critical and EQ will do nothing for it.
See the following from a newsletter we did.
Quote:
Waterfall Graphs

Before we move on to your next set of tests, here is a little background on decay times and waterfall graphs and why they are so important to view (if not more important then frequency response). As a sound plays through your speakers it doesn't just get to you and stop but continues to bounce around the room and slowly fades away over time. This is sometimes referred to by others as ringing or reverb. A waterfall graph allows you to visualize how quickly or slowly a given frequency decays over time.

Low frequencies tend to be stronger and stay more intense longer than higher frequencies. Higher frequencies are also easier to control. Things like people, furniture, carpet, curtains, and even air tend to have a much more significant impact on the higher frequencies than lower ones. In addition, high frequencies are much more directional where low frequencies tend to spread like a sphere in 3 dimensions. In a bare room, there really isn't much that has any significant impact on low frequencies which is why it is critical to have proper bass trapping . As the low end keeps bouncing around the room there are other things that you are trying to hear but the frequencies that are ringing are masking imaging cues, harmonic textures, and even cancelling and/or reinforcing themselves.

When someone refers to a room that sounds "tight" or "clear" they are most likely in a room that the low end decay times are under control with bass traps.
Testing of Acoustic Foam Bass Traps. Acoustic Panels and Bass Traps.
#6
29th March 2012
Old 29th March 2012
  #6
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jitterybit's Avatar
at risk of sounding like a trolling smatass,
i second all of the above and otherwise recommend a good set of headphones until you can afford proper treatments.
also, tweak your monitors(if you can) to the room per your spectral analysis...
and monitor at low volumes with the speakers close to you.

i like ultrasones myself
others like beyers, etc....
#7
29th March 2012
Old 29th March 2012
  #7
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Jens Eklund's Avatar
 

Quote:
Originally Posted by jitterybit View Post
and monitor at low volumes with the speakers close to you.
Low level monitoring
#8
29th March 2012
Old 29th March 2012
  #8
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Dange's Avatar
 

Quote:
Originally Posted by Glenn Kuras View Post
To me the highlighted part is the most critical and EQ will do nothing for it.
See the following from a newsletter we did.
Interestingly, you can actually tame the room mode peaks with EQ. There are high end hi-fi systems that do this by Bang & Olufsen and Meridian Audio.

If you think of room mode resonance peak as a mass on a spring then if you drive it hard then let it go it's going to bounce up and down for ages. If you drive it less, it won't bounce up and down for as long (i.e. it's decay is shorter). I think they work on the theory that most hi-fi rooms are setup with the speakers at one end of the room and the listener at the other so both the speaker and listener are in modal peaks.

Still that's hi-fi, not studio. I still think bass traps are the way to go for taming LF.....

Also did the whole minimum phase, excess group delay and applying EQ thing ever conclude? I.e. you can use EQ in frequency regions where the system's excess group delay is zero
#9
29th March 2012
Old 29th March 2012
  #9
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DanDan's Avatar
Open Minds

JohnPM has explained elsewhere how modes are actually shortened by eq, not just apparently so.
Jeff has written about his everyday use of the excess Group Delay as you alluded to.
MiniDSP have a great range of tiny affordable high quality DSP modules.

IMO some useful help can be had from REW and a Parametric Eq.
But there is plenty of experimentation going on with servo/time correction.
A GS here showed a remarkable result on the lowest mode using a mic and a parametric Eq.
I tried but it was too unstable in my complex room. Jeff tells me he has had great success.

DSPeaker-Home seem to have taken this all the way.
Afaik they are using sensing of back pressure at the speaker cone.
There graphs on the site look really promising.

DD
#10
29th March 2012
Old 29th March 2012
  #10
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kasmira's Avatar
 

Quote:
Originally Posted by Dange View Post
If you think of room mode resonance peak as a mass on a spring then if you drive it hard then let it go it's going to bounce up and down for ages. If you drive it less, it won't bounce up and down for as long (i.e. it's decay is shorter).
Yes, but is that not similar to saying "If you turn your speakers down, your room modes won't play as big of a part" ?

I mean how much shorter are we really talking about? Surely no more than 10-20%? The resonance and ringing will still be there (I'm sure you're aware, just stating)
#11
29th March 2012
Old 29th March 2012
  #11
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DanDan's Avatar
Apparently

That's what I meant by 'apparently' kasmira.
An Eq filter can actually shorten a modal ring.
I cannot explain to the level that John would but my basic take on it is that a filter is a partly resonant system. With a much shorter time element than the mode. That damped resonant system can piggyback on the room mode, weakening and shortening it.

DD
#12
29th March 2012
Old 29th March 2012
  #12
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kasmira's Avatar
 

Quote:
Originally Posted by DanDan View Post
That's what I meant by 'apparently' kasmira.
An Eq filter can actually shorten a modal ring.
I cannot explain to the level that John would but my basic take on it is that a filter is a partly resonant system. With a much shorter time element than the mode. That damped resonant system can piggyback on the room mode, weakening and shortening it.

DD
Thanks for the info Dan. Sorry, I had the thread opened before you responded, so I didn't see your post.
#13
29th March 2012
Old 29th March 2012
  #13
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Glenn Kuras's Avatar
 

EQ would only help in a very small area. Move a few inches and it all falls apart. Ethan did a test of this a few years ago.
#14
29th March 2012
Old 29th March 2012
  #14
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DanDan's Avatar
Area

Many attempts at Eq fail in the way you and Ethan describe. But there are many others that work partially or even 100%.
Indeed many measure at a single nose position rather then two ear positions.
Response, even LF, is seen to change radically over even these small distances.
But.
Some Eq's apply over the whole space, e.g. a Baffle Step Compensating filter or a HF shelf. 100%
And, if a mode is shortened by a passive device or by an active device, it is weakened and shortened everywhere. Partial but useful.
I think it is time to move on from the 'rule of thumb' that you cannot Eq a room better.
In the recent IOA Reproduced Sound 2011 a couple of papers were presented on the matter.
The first was in controlling varied subs in an ITU CR setting and it was deemed entirely successful.
The second was on three proprietary room eq system in four pro CR's.
They concluded that a good studio was not changed but a bad one was significantly improved.

I will just mention the BagEnd E Trap and again recommend anyone to take a look at DSPeaker. If it's true, this may be an affordable Trinnov.

DD
#15
29th March 2012
Old 29th March 2012
  #15
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Dange's Avatar
 

Quote:
Originally Posted by Glenn Kuras View Post
EQ would only help in a very small area. Move a few inches and it all falls apart. Ethan did a test of this a few years ago.
Not going to dispute that. Although the Meridian System is more than just an EQ (which is what the ARC system is that Ethan tested, I believe) and they also explain why just simple Room EQ won't work here: - Meridian Audio White Paper
#16
29th March 2012
Old 29th March 2012
  #16
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DanDan's Avatar
Deep

Here's the stuff by John which I spoke of.
Minimum-Phase Room Response
Worth noting that elsewhere he says that Eq is very useful in the limited circumstances where it delivers but it can only ever be a very small part of the overall treatment.

While true, it is perhaps worth repeating that much of the current development involves time domain and even servo/reactive elements as well as the simple Eq.

DD
#17
29th March 2012
Old 29th March 2012
  #17
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Glenn Kuras's Avatar
 

Quote:
Originally Posted by Dange View Post
Not going to dispute that. Although the Meridian System is more than just an EQ (which is what the ARC system is that Ethan tested, I believe) and they also explain why just simple Room EQ won't work here: - Meridian Audio White Paper
I am actually talking about a test he did where one guy eq'ed the room and said you could effect ringing. Well I think he did but only for a very small portion of the room. When the mic was moved it all fell apart. I tried to find the article but could not find it. If I get a moment I will email Ethan to have him post it.
Needless to say if you had a spike at say 30hz you could bring that down but keep in mind that it would only work for that one small area of your room. Also it still will ring.
#18
29th March 2012
Old 29th March 2012
  #18
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Glenn Kuras's Avatar
 

I just went into our test room and ran a quick test. I tested at the mix spot then moved around 1' left and right, around 6' off the floor (one foot behind mix spot) and tested in the back of the room like someone sitting on the couch.

I also am attaching decay times for the mix spot and standing. Sure you could eq that 38hz area but the guy standing behind you is going to hate you for it. Also there is still ringing there.

I guess if I fully treated the room and still had a bit of a problem at 38hz I could pull it down, but it is not going to solve decay to any great degree.
Attached Thumbnails
Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-differentseatingspots.jpg   Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-mixspotwf.jpg   Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-standing.jpg  
bwo
#19
29th March 2012
Old 29th March 2012
  #19
bwo
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Here are ETC graphs with and without room correction. The program being used for correction is Audiolense: Juice HiFi
Attached Thumbnails
Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-etc-no-drc-55ms.jpg   Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-etc-ttd-11-55ms.jpg   Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-etcnodrc14ms.jpg   Flatten Monitors Response - Recommended Software?! Filter Impulse Response?-etcwithttddrc14ms.jpg  
#20
29th March 2012
Old 29th March 2012
  #20
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DanDan's Avatar
Ringing

Thanks for going to the trouble Glenn. However, I wish you had tried an Eq to see whether one of those modes would shorten.
I am quite sure that JohnPM is correct when he says they do, but as you say whether that is to any great extent is not widely established.

Here GS capoeira got pretty significant Mode shortening and null filling using DRC.
room treatment coupled with digital room correction
I am not sure if DRC is an Eq or works in the time domain also.

Here's an example of mode shortening by 'servo'.
room treatment coupled with digital room correction

DD
#21
29th March 2012
Old 29th March 2012
  #21
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Glenn Kuras's Avatar
 

Quote:
Originally Posted by DanDan View Post
Thanks for going to the trouble Glenn. However, I wish you had tried an Eq to see whether one of those modes would shorten.
I am quite sure that JohnPM is correct when he says they do, but as you say whether that is to any great extent is not widely established.



DD
I am sure it would shorten (by a little) but it still is going to be there. That really is my point.
#22
29th March 2012
Old 29th March 2012
  #22
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by Glenn Kuras View Post
When the mic was moved it all fell apart. I tried to find the article but could not find it. If I get a moment I will email Ethan to have him post it.
Audyssey Report
#23
29th March 2012
Old 29th March 2012
  #23
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DanDan's Avatar
Little but where?

Well the Audyssey Report is the only one showing NO modal shortening.
In fairness Glenn and Ethan, the links I posted showed noticeable reductions in modal ringing. (Although I am not sure if DRC is just Eq)
As does this Hard proof that equalization kills room

However, the question, posed by Ethan at the end of that linked article, remains sort of unanswered.
I really don't know if such Eq would shorten modes in one location and not in another. This seems unlikely. Passive Traps seem to shorten modes equally everywhere. However I am pretty much equally mystified by the fact that they do shorten at all. The tests presented do show it happening quite noticeably.
Also this is interesting.
Quote:
“Room resonances at low frequencies behave as “minimum phase” phenomena, and so, if the amplitude vs. frequency characteristic is corrected, so also will the phase vs. frequency characteristic. If both amplitude and phase responses are fixed, then it must be true that the transient response must be fixed – i.e. the ringing, or overhang, must be eliminated” (Toole, The Acoustical Design Of Home Theaters, 1999)
Hmm, more stuff to add it to the ToDo List in your's and my test scenarios Glenn.

DD
#24
29th March 2012
Old 29th March 2012
  #24
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frans's Avatar
Steve, I'm sorry to say that EQ or IRs won't flatten the response of your room. It will do a little something for your speakers, but nothing for your room. But you will listen to your speakers IN your room. Speakers plus room = what you hear.
It's a little like when you want to drive 200mph with a sports car on a gravel road. Try to flatten the road with an IR? Of course not. The car needs a suitable road as the speaker needs the room, they can't be seperated. Or .. you could. It's called headphones. But you won't escape the room with speakers as much as a diver can't avoid getting wet.
#25
29th March 2012
Old 29th March 2012
  #25
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Glenn Kuras's Avatar
 

Quote:
Originally Posted by DanDan View Post
Well the Audyssey Report is the only one showing NO modal shortening.
In fairness Glenn and Ethan, the links I posted showed noticeable reductions in modal ringing. (Although I am not sure if DRC is just Eq)
As does this Hard proof that equalization kills room

However, the question, posed by Ethan at the end of that linked article, remains sort of unanswered.
I really don't know if such Eq would shorten modes in one location and not in another. This seems unlikely. Passive Traps seem to shorten modes equally everywhere. However I am pretty much equally mystified by the fact that they do shorten at all. The tests presented do show it happening quite noticeably.
Also this is interesting.


Hmm, more stuff to add it to the ToDo List in your's and my test scenarios Glenn.

DD
I am looking for a eq plug in that runs on windows (free) and see if I can eq that way. I could then rerun the test with it eq'ed. I feel pretty confident though that the decay will only shorten due to drop in db.
#26
29th March 2012
Old 29th March 2012
  #26
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by DanDan View Post
Well the Audyssey Report is the only one showing NO modal shortening.
Right, because it's the only article that shows graphs of the actual rate of decay.

I've been in a discussion in another forum with Nyal Mellor, and I asked if he can display a traditional waterfall that shows the decay rate. He said he'll try and will reply again later. This is at the AVS forum in the Audio Theory section. What I see in his blog (as best I can read it) is a graph that shows mainly energy, not decay rate.

Nobody disputes that EQ can reduce the level of a ringing peak. When the level is reduced, it doesn't harm the sound as much. But those bass notes still linger, which muddies subsequent notes. This is the real issue. And of course EQ cannot fix nulls, and EQ that improves the response at one place in a room almost always makes the response worse elsewhere.



--Ethan
#27
29th March 2012
Old 29th March 2012
  #27
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Glenn Kuras's Avatar
 

Quote:
Originally Posted by frans View Post
Steve, I'm sorry to say that EQ or IRs won't flatten the response of your room. It will do a little something for your speakers, but nothing for your room. But you will listen to your speakers IN your room. Speakers plus room = what you hear.
It's a little like when you want to drive 200mph with a sports car on a gravel road. Try to flatten the road with an IR? Of course not. The car needs a suitable road as the speaker needs the room, they can't be seperated. Or .. you could. It's called headphones. But you won't escape the room with speakers as much as a diver can't avoid getting wet.
200mph??? Oh wait your from Germany.
bwo
#28
29th March 2012
Old 29th March 2012
  #28
bwo
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Quote:
Originally Posted by Ethan Winer View Post
I'm not a particularly believer in room correction, but you can't make a generalization out of that comparison. Audyssey, an especially from that time, has also never been considered a good correction system.

Here are some waterfall graphs. First without Audiolense correction, then with standard DRC and the last with additional True Time Domain DRC applied.


#29
29th March 2012
Old 29th March 2012
  #29
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DanDan's Avatar
Glenn, yes struggling with that one on a Mac myself. Interapplication communication is not a strong point.
And MiniDsp modules seem to SRC everything incoming to 48K.....
Did you look at the linked blog? (CC Ethan) Nyal does show a regular Waterfall there.
Thanks bwo. Does DRC do something more than Eq, some time domain damping thing?

DD
#30
29th March 2012
Old 29th March 2012
  #30
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Glenn Kuras's Avatar
 

Quote:
Did you look at the linked blog?
I did but he changed the time from his first graph to the other so it is hard to say what really happened but Ethan's point seems to fall in line.

Quote:
Nobody disputes that EQ can reduce the level of a ringing peak. When the level is reduced, it doesn't harm the sound as much. But those bass notes still linger, which muddies subsequent notes. This is the real issue.
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