Room treatment - start with acoustic, or corrective EQ?

[DanDan]

Room Eq Wizard can help you analyse your current situation. It can also prescribe Eq settings and show the probable result.

I, and coincidentally a recent AES survey, came to the same conclusion about Eq. A little different than the commonly quoted views.....

It can make a bad situation better. With better rooms and treatment it does less because there is less to do.
Small room treatment needs to be extensive and positioned to achieve greatness. However lesser treatment still yields wonderful improvement.
I would encourage you to go for it asap. Do some certain treatments, e.g. hit the L R and Overhead Reflection points with at least six four inch traps with similar airgaps. The result will persuade to do some serious work on the LF side. Try some Eq also. I am on Mac so choices are a bit limited.
I am liking Dirac Live at the moment. As your treatments are developed you will see the DRC reacting with gentler filters and so on. The sweet spot will expand and the overall result will reward your efforts.

DD

[Glenn Kuras]

Which should I invest in first?

Treat the room first.

Which will give the most initial improvement?

Considering you are not fixing the monitors but fixing the room it only makes sense to fix the problem, which is the room. No amount of EQ will solve a room problem. It might lower a peak here or there but will do very little to nothing about the decay times, which decay times are just as important (IMO more important) then a flat response.

About decay times.

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 Acoustic Foam Bass Traps

Edit: BTW if you did treat your room and found a peak at around 40hz it would not be totally wrong to slide that down a few db but it really is not going to solve the over all problem.

[DanDan]

Sorry to disagree directly Glenn but Eq can and does shorten room modes.
Furthermore while it cannot fix nulls directly they do get filled in as a by-product of the process. I also think it extremely useful to 'fix the speaker'
both in terms of anomalies in the device but in the interaction between it and the room. This also allows a favoured 'target curve' to be imposed. Much like with speaker processors.
I used to think my speakers were just great until.....!
John PM, bwo, and others, have shown direct tests revealing distinct mode shortening. Here's another.
http://blog.acousticfrontiers.com/wh...oom-modes.html
DD

[Glenn Kuras]

Sorry to disagree directly Glenn but Eq can and does shorten room modes.

Not like room treatment does and to let someone thing that is just, well wrong. Sorry to disagree with you also.
To solve a knocking in your car engine with better tires is just about the same as using a eq to solve room acoustic problems.

Edit: And just to make sure, I am saying "solve" the problem.

[jim1961]

I feel the room should be dealt with first via room treatment.

Take good measurements before and after. Then, if some minor anomalies still exist, then EQ.

The thing about EQ is that it affects both the room response AND the direct response. Any EQ you introduce will color the direct sound, and you dont want to do more of this than is necessary.

[DanDan]

Treatment and Electronic treatment both work and both have limitations. Start with and continue with both would be my advise.
There seems to be an accepted wisdom about Eq perhaps based on a hatchet job done on one particular product way back. It ain't true.
Here's an example of pretty spectacular success. There are many others. Please do read these links before using the wrong word again.
room treatment coupled with digital room correction
Eq can and does actually shorten modes. That earlier link seems intermittent so I fixed it
http://blog.acousticfrontiers.com/wh...oom-modes.html
Heres another more scholarly one.
http://accucalhd.com/documents/audio...20Research.pdf
Another with examples from bwo using Audiolense and input from JohnPM.
Flatten Monitors Response - Recommended Software?! Filter Impulse Response?

“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)

DD

[Glenn Kuras]

Originally Posted by jim1961

I feel the room should be dealt with first via room treatment.

Take good measurements before and after. Then, if some minor anomalies still exist, then EQ.

The thing about EQ is that it affects both the room response AND the direct response. Any EQ you introduce will color the direct sound, and you dont want to do more of this than is necessary.

Pretty much sums it up.

[DanDan]

I absolutely do want to affect the Direct sound. Speakers, with their various radiation patterns are perfect for all rooms?
There are very few speakers or systems that I have encountered which I didn't want or have to tweak to suit purpose.
I have rarely seen a high end studio with a speaker processor.
A recent AES survey of Pro CR's found DRC to be beneficial in those with the most problems, and less so in properly treated balanced rooms.
This looks opposite to the common wisdom? to me. My own limited experiments confirm the finding.
I see yet another 'Rule of Thumb' wobbling.
Plse do read the links guys, the times they are a changin

DD

[diggo]

Times might indeed be changin'..... are times are indeed the issue here. Not only decay times, but also faster events such as SBIR/reflections, which are important, no?

A very clear distinction needs to be made between the consumer and the professional audio engineer. One just wants things to sound good, the other makes professional decisions based on listening. Those decisions have consequences for our customers. We need to be sure what we hear is minimally influenced by the room.

I personally have nothing against room EQ, provided the room has been optimally treated first.

It is inexpensive to reduce modal ringing and SBIR/reflection anomalies, sometimes using the same materials twice (ie material/device to reduce ringing can also reduce other problems).

Here's why you should treat rooms first: it makes for better results if the room is ever used for recording. No amount of room EQ will affect how a guitar or voice sounds in the room....which is one reason why professional rooms have different requirements than consumer listening rooms.

Sean

[Glenn Kuras]

I personally have nothing against room EQ, provided the room has been optimally treated first.

Which I stated also....
I wanted to answer the person (not start a dumb debate, which sorry if I did) that started the thread, which the question was

Which should I invest in first? Which will give the most initial improvement?

The answer is room treatment.

[Davido]

Classic case of someone asking for advice, getting advice from people who are the leading minds on GS about the topic, then disagrees.

Why ask in the first place if you think you know already?

[Rod Gervais]

Dan,

I would not suggest that this is contrary to the common wisdom......

It's easy to keep in perspective if you picture it from the "law of diminishing returns" point of view....... it's costs me "X" to build a room and treat it to the point of a pro level "A" room - from that point on the cost of improving on the room almost becomes exponential - small improvements take very large investments..... using standard construction methods...

If I already have a space that is "world class" in acoustic quality - there are only very very small improvements that can be made in the space to begin with - regardless of the means I might choose to take to make those improvements...

If the room was 110% perfect - no acoustic anomalies - then there would be no improvements that could be made..

Now - let's suppose I design control room "A" and it's a great room (I always strive for that) thus there is going to be little benefit to the client if they apply EQ as a part of the chain.

Now - the flip side of the coin -

I am hired to deal with acoustics in a studio that was badly designed from the onset - I recommend to the owner that they have 2 very different paths they can follow - and which route they take is going to be very dependent on the depth of their pockets, and their willingness to part with some serious cash (or not as the case might be)......

We can either completely rip the room down - at which point I can design an excellent room for them given the available real estate,

OR

I can guide them in the best direction possible to make some decent acoustic changes - but they will have to (in the end) deal with the remaining acoustic anomalies through the use of EQ....... at least to the point where they have a fairly decent room when all is said and done.

In the first case - the use of EQ is not going to be necessary -

In the 2nd case the use of EQ is going to make both the best of a bad situation and a relatively drastic change in the quality of the sound in the space..

To me the question is not (and never has been) can EQ make improvements - even drastic improvements at times - it is (rather) this:

Can one achieve (with today's technology) the same acoustic quality (in a poorly designed/treated space) using EQ that one can with a properly designed and treated space not using EQ?

I am well aware that the technology has grown in leaps and bounds in the past few years - and will not predict the day will never come where the technology will reach the point where common room treatments won't become a "thing of the past" - but that is not a point we're at today....

Now - that having been said - there must be some point where a balance could be struck (again this would have to be a properly designed space - taking everything into account) where there could be lesser room treatments coupled with an EQ solution that achieved the same level of acoustic properties as a properly designed space without EQ...... but it would be a delicate balancing act figuring that out... of course it is to do it the other way as well...

Rod

[DanDan]

Hmmm, well the Ark was built by Amateurs but Professionals built the Titanic...

We need to be sure what we hear is minimally influenced by the room.

Tell the LEDE gang that!

I am not sure if SBIR is amenable to EQ or not. Instinctively I doubt it.
REW can show susceptibility to successful Eq or not , using the Excess Group Delay graph. Must look into that one as most instincts seem to be proving wrong these days.

Speaking of which, instinctively I am with you guys. Attack the big problem first, treat the room. However, in many many circumstances, location work, rental, money, domestic issues etc. etc. treatment is restricted.
In such circumstances Eq is IMHO a godsend.
It is very quick and easy to download a package, demo it. If it sounds and measures better, how bad?
An encouragement to do the heavy lifting perhaps?

I don't care which comes first.

Speaking of which:-
Chicken and Egg laying back in bed together, smoking cigarettes....
One says to the other, well that answered it......


DD

[DanDan]

Synchronous typing!

I fully concur with every word of that Rod.

Diggo's point too, a well treated CR is often most useful Recording space.

Another advantage unique to a well treated room is the ability to simulate or experience other environments. Now and again I fire up 4.0 and create a nicely live space by trimming down IR's of great recording rooms. The modern balanced ones work brilliantly, e.g. TrackDown in Australia.
It is interesting to note that many legendary studios have made their live rooms freely available to use, Wiseloord, Cello, Teldec, etc. etc.
But no CR's.
I have to brag here. I was in Real World Studios at the weekend.
Holy frick!
I asked them to consider doing some Altis.

DD

[jim1961]

Originally Posted by DanDan

I absolutely do want to affect the Direct sound. Speakers, with their various radiation patterns are perfect for all rooms?
There are very few speakers or systems that I have encountered which I didn't want or have to tweak to suit purpose.
I have rarely seen a high end studio with a speaker processor.
A recent AES survey of Pro CR's found DRC to be beneficial in those with the most problems, and less so in properly treated balanced rooms.
This looks opposite to the common wisdom? to me. My own limited experiments confirm the finding.
I see yet another 'Rule of Thumb' wobbling.
Plse do read the links guys, the times they are a changin

DD

Let me make a distinction / clarification.

Lets say the direct response is exactly what you want, but the room response is not. Introducing EQ in this scenario helps one case and hurts the other. Here, a compromise must be reached.

Now, if you dont like the direct response, then sure, EQ away!

I think what occurs in many cases is we sit in front of our system and evaluate the overall response, which of course is direct and room. And in some of these cases one or the other maybe fine, but without experience in both listening and treating rooms, we are unclear which is contributing to some given aspect we deem needs fixing. Or, both may have coloration, but say the direct response is too bright and the room response is lacking in the highs (often the case with carpeted rooms and loudness wars CD's), you get something where the overall tonality may seem about right, but yet, we detect something is wrong with it. In this case, having good measuring equipment is about the only way we have a chance to easily get to the bottom of the real problem which your average listener does not have.

[BriHar]

Three acoustical issues a room correction product can't actually correct!

Three Acoustical Issues that Room Correction Can’t Correct

[jim1961]

Originally Posted by BriHar

Three acoustical issues a room correction product can't actually correct!

Three Acoustical Issues that Room Correction Can’t Correct

You mean, three acoustical issues digital room correction cant correct dont you?

[BriHar]

Originally Posted by jim1961

You mean, three acoustical issues digital room correction cant correct dont you?

You'll have to take that up with the author of the article, Nyal Mellor

[diggo]

Originally Posted by DanDan

Speaking of which:-
Chicken and Egg laying back in bed together, smoking cigarettes....
One says to the other, well that answered it......
DD

Because a chicken is just an egg's way of making another egg.

Sean

[Glenn Kuras]

Speaking of which:-
Chicken and Egg laying back in bed together, smoking cigarettes....
One says to the other "Why is Dan trying to lay an egg with a cow?"

[BriHar]

I remember one of my teachers got quite upset when I gave him the definitve answer to this question (I didn't know he was a creationist).
When I explained that because a chicken is hatched from an egg, then the egg obviously had to come first.
He replied with a cheshire smile the obvious response "what laid the egg?"
I replied it was something that was almost a chicken.
A proto-chicken if you like. to be more specific you first have to define exactly what a chicken is.

[diggo]

Originally Posted by BriHar

I remember one of my teachers got quite upset when I gave him the definitve answer to this question (I didn't know he was a creationist).
When I explained that because a chicken is hatched from an egg, then the egg obviously had to come first.
He replied with a cheshire smile the obvious response "what laid the egg?"
I replied it was something that was almost a chicken.
A proto-chicken if you like. to be more specific you first have to define exactly what a chicken is.

And not lose sight of the fact there isnt a whole lot of difference between humans and earthworms. We just have a lot more apparatus assisting the in/out tube...but there is no denying that animals with digestive tracts at one point were not much more than digestive tracts. The stomach doesnt support the brain - it's the reverse. We had stomachs long before before we had brains....

Sean

[diggo]

Originally Posted by jim1961

Let me make a distinction / clarification.

Lets say the direct response is exactly what you want, but the room response is not. Introducing EQ in this scenario helps one case and hurts the other. Here, a compromise must be reached.

Now, if you dont like the direct response, then sure, EQ away!

I think what occurs in many cases is we sit in front of our system and evaluate the overall response, which of course is direct and room. And in some of these cases one or the other maybe fine, but without experience in both listening and treating rooms, we are unclear which is contributing to some given aspect we deem needs fixing. Or, both may have coloration, but say the direct response is too bright and the room response is lacking in the highs (often the case with carpeted rooms and loudness wars CD's), you get something where the overall tonality may seem about right, but yet, we detect something is wrong with it. In this case, having good measuring equipment is about the only way we have a chance to easily get to the bottom of the real problem which your average listener does not have.

Correct.

As an aside, the best place for DSP is within the speakers themselves, where it can be (and often is) the best method to tweak crossovers and speaker response. But this kind of DSP is very different to "room DSP", because it is dealing directly with known mechanical factors, whereas applying EQ to the system to reduce (say) modal ringing in the room is not the best initial method to deal with modal ringing, because (when room EQ is used as the only method) it may create additional problems which may be more serious than the ringing. And if the user is inexperienced, those additional problems may go unnoticed.

This is especially true of professional rooms, as I've said on multiple occasions. If we adjust the EQ on a track, we need to be very confident that what we are correcting is the audio and not room anomalies.

Hence the brilliance of tools like REW.

Measure with mic as listening position. Analyse the results. Move the mic forward 1', measure again. Move the mic back 1', measure again. Move the mic sideways 1' in both directions, measure each time. Raise it 1', lower it 1', measure each time. Move the mic to one of the room's tri corners, measure again.

That entire process takes less than 30 mins and it costs NOTHING, yet it will give you a very clear idea of what is happening in the room, particularly in close vicinity of the listening position.

Moving the mic helps you determine whether a frequency dip is SBIR or something else.

If you can spend longer, run variations where you move the speaker. This is especially illuminating once you start playing around with sub positions, or incorporating subs into your system. It's one reason why many people freak out at first when they upgrade their speakers (for example) from NS10s to full range Barefoots, because suddenly SBIR and modal excitement becomes a problem.

There's a lot to be said for full range speakers instead of separate subs, but there's also a lot to be said for separate subs. The decision about which option to pursue depends on multiple factors, but one thing is sure: any full range system will benefit from inexpensive room treatment without the treatment causing other problems (except for consuming space, but VPRs such as Modex Plates are a great solution if space is a problem)

It's not rocket science to use REW and put in some fundamental room treatments before you resort to "room EQ", especially if you dont know a lot about acoustics. You'll learn A LOT by doing it.

And if you are working in professional audio, you really should spend a bit of time experiencing the effects of room anomalies - learn to recognise the symptoms, pin down the causes and determine the optimal solution. If it gets a bit too confusing, hire someone to help. I can recommend Jeff Hedback as someone who delivers excellent value for money in this regard. All you'll need to do is send Jeff your REW files, pics of your room and dimensions etc. Of course, there are multiple guys who offer inexpensive yet very professional services like Jeff.....and many of them hang out on forums like this.

So you dont even have to pay - post your REW files here and get excellent, free advice from experts like Jeff.

Sean