Measuring the Room Acoustics--EQ Wizard Software

[Primal Yell]

Anybody mind sharing "tips" about using it? It's discussed at the Home theater Shack forum, but before diving in, is it applicable for use in small room project Studios?

 

Best Regards in Your Studio, Have a Good One.

Greg

[Ethan Winer]

I've used ETF for years, and more recently I use REW exclusively. Yes, it's perfect for measuring small rooms. This article explains how I use ETF, but the principles apply to all such programs including REW.

 

--Ethan

[Primal Yell]

As a professional you are capable of taking the acousitical correction process to great measure---and I respect that. I refer to it as a "process" as far as correcting the flaws, and deficiencies because it seems that experimentation is at play, with retesting, and further iterations after that.

 

When is it ok to say that you've done enough testing and correction?

When are you supposed to say OK, lets live with it, go with it, and make the most of your room situation?

How much db variation (for example) are you supposed to tolerate in a project studio? (I respect that your clients are the likes of mastering engineers and audiophiles and their standards are higher).

 

I do not mean to lesson the importance of persistance and rigourous effort in any way. But on the other hand, I want to know when to say when, and avoid chasing my own tail so to speak. I'm not opposed to doing my homework. In fact, it's quite interesting, and a potential distraction from music....sorry for being verbose. Thank you Ethan.

[Ethan Winer]

When are you supposed to say OK, lets live with it, go with it, and make the most of your room situation?

 

When you have lined every possible corner with bass traps.

 

Seriously, I do not rely on measuring very much, except to 1) show people how bad their untreated really room is, and 2) to confirm that it's better after adding bass traps and other treatment. I treated my 25 by 16 foot living room over the course of a few years, and I just kept adding traps. I did measure once in a while, but mostly because I'd need a graph for an EQ Magazine article.

 

--Ethan

[starsnuffer]

"good enough" probably depends on your ears and how sensitive you are to inconsistancies.

 

A good way to answer that question is to mix something in your space, and then take that mix to another space. . preferably a very nice space, and see what you glean from that. If you don't notice much difference, then it's "good enough".

 

-W

[WRGKMC]

What the pros use is software like this now.

http://ral-realtime-analyzer-light.yoshimasa-electronic-inc.downloadsoftware4free.com/

 

They used to use hardware test instruments but since the onset of computers this stuff can be loaded on a laptop to get the same results.

With a decent reference mike you can fix nearly all acoustic problems in real time simply walking around the area with the mike searching for acoustic issues with white, pink, or a variety of tones pumping from your monitors. It can even bring up results in stereo and compensate nfor various mike types.

the only issue I had with the software is it didnt work right with an 8 thack PCI card like I use. it dominated 2 tracks and disabled the other 6 on my setup till I removed the software. I later reinstalled it when I had a dual boot system and had a seperate card for it. The software will do as good a job as the person using it.

[MrKnobs]

Actually, what the pros use varies a bit but it's usually either a handheld frequency analyzer:

 

 

Which has the disadvantage of walking around the room and tells nothing about the direction and phase of the sound, or a better analyzer using external probe:

 

 

Which uses an intensity probe to determine both particle velocity and sound pressure, giving the direction of the sound measured by frequency band, and also allowing for an impulse test where the decay time of each frequency band is measured.

 

Putting a sound meter / frequency analyzer in the listening position gives a rough idea of the room response but tells you nothing directly about what reflections are summing together to cause that response, nor the location from which they're coming.

 

Using the intensity probe, you can measure the amount of reflected sound vs. direct sound at any location in the room, thus determining the absorption by frequency directly at the bass traps.

 

Then again, with no budget I'd have to agree with Nathan's semi tongue in cheek reply of cover every possible corner with bass traps - just make sure they're good bass traps that absorb down into the low bass.

 

As an example, I'd call an Auralex LENRD a bad bass trap as it doesn't absorb much below 250 Hz, and I'd call an Auralex MegaLERND a good bass trap as it has significant absorption below 100Hz where the main problems in a small room generally lie.

 

Everything else I've tried lies somewhere between these two endpoints.

 

Terry D.

[Primal Yell]

Gentlemen, from what I can gather, you've made a pretty good case for abandoning or deferring the use of eq software--at least within the limited budjet and scope of the project studio. Just skip that software process, and go right into "implementing" proper sound absorbtion. If one were to do that, they would not have the benefit of getting a "before" picture of their room, nor be able to judge the effectiveness o their changes.

 

Focus on mix translation-ability.

 

This is not what I expected to hear. But if its practical, and saves time---its still progress, and thats a good thing.

 

The eq software does look neat, but it may be largely academic....., and you don't really have to go there ??

 

Tell me, Am I reading you right---Am I missing something here?

[MrKnobs]

 

Gentlemen, from what I can gather, you've made a pretty good case for abandoning or deferring the use of eq software--at least within the limited budjet and scope of the project studio. Just skip that software process, and go right into "implementing" proper sound absorbtion. If one were to do that, they would not have the benefit of getting a "before" picture of their room, nor be able to judge the effectiveness o their changes. Focus on mix translation-ability. This is not what I expected to hear. But if its practical, and saves time---its still progress, and thats a good thing. The eq software does look neat, but it may be largely academic....., and you don't really have to go there ?? Tell me, Am I reading you right---Am I missing something here?

 

 

Well, all Ethan's saying (and I'm agreeing) is that the more bass trapping you install in a small room the better. Since you're not going to get anywhere close to eliminating the bass modes entirely, you can't put up too much bass trapping.

 

However, if you put up too much broadband absorption your room will be too dead sounding to mix in comfortably. You don't want an anechoic chamber, just as wide an area as possible around the mix position where you can hear what's on the "tape" reasonably uncolored.

 

So, if you cover every square foot of your walls with 12" deep foam you're going to kill your bass modes but you'll also kill the liveness of the room more than you'll like.

 

This is why I have some of Ethan's panel absorbers and some MegaLENRDs. The ML's are better bass traps than the panel absorbers, but they also absorb the higher frequencies as well. The panel absorbers absorb some bass but reflect much of the higher frequency stuff and hence don't make the room sound too dead.

 

As for spectral analysis software, you don't need the expensive gear I use at work (have to be accurate down to 0.1dBA for legal reasons), you're fine with the cheaper or free stuff, and you're also fine with a cheap measurement microphone like THIS or even a cheap lavalier mic, since both are very flat in the low octaves where you want to measure.

 

So yeah, you can just add a lot of bass trapping and most likely be fine, but it's educational (and fun) to use a measurement system to see where you are before and after.

 

As an acoustics researcher, I have a bookshelf full of theory but there's not a week that goes by when I'm working in the field actually measuring things where something doesn't come out as theory predicts. When theory and (careful) measurement don't agree, measurement always wins.

 

Terry D.

 

P.S. One final thing - you're never going to many any room perfect, especially not a small one. You just need to get it reasonably flat and then the most advanced audio computer ever made (which is inside your skull) can learn the room (by listening to many commerical recordings in that acoustic space) and compensate for the remaining problems. THEN your mixes will translate to other systems.

 

Summarized, (1) Get the flattest monitors with the widest sweet spot you can afford, (2) treat your room to make it as neutral as possible, then (3) spend some time critically listening to commercial CDs in that room. If you do this, you really won't need to go running out to the car constantly and you'll have only rare and minor surprises at the mastering lab or in your friends' / clients' systems.

[Primal Yell]

Would like to follow up in a few weeks and post my room curve. Is there other relevant info that should be posted besides the curve?

 

I got ridiculed when mentioning the behringer measurement mic to a mastering engineer--he said that poor quality control at behringer can mean that it may be 10 or 12 db away from the stated mic curve! I'm not a Pro, and please-I mean no offense, but can you please suggest another mic?

 

Thanks for making many good points--they are noted. Best Regards in your studio by the way

[Lee Knight]

I have 2 of those Behringer test mics and they sound identical. He may have a point there but luckily I did ok with mine.

[MrKnobs]

--he said that poor quality control at behringer can mean that it may be 10 or 12 db away from the stated mic curve! I'm not a Pro, and please-I mean no offense, but can you please suggest another mic?

 

10-12 dB? That's....huge!

 

I'd have to see that to believe it, even a $20 Radio Shack lavalier mike is flatter than that in the low frequencies you need to measure. An omni condenser mike that's 10-12 dB off flat between 100Hz - 2kHz isn't "off," it's BROKEN. Maybe someone stepped on it...

 

How about the dBx or Audix mics on THIS PAGE?

 

At work we use B&K or GRAS mics that cost about $10,000 a pair, but those are accurate to 0.5dB and periodically certified. But there's no need for that sort of precision in measuring a room (or anywhere else in my opinion), the modes you're looking for are huge by comparison.

 

Terry D.

[Ethan Winer]

 

he said that poor quality control at behringer can mean that it may be 10 or 12 db away from the stated mic curve!

 

 

Not so. Proof here:

 

Comparison of Ten Measuring Microphones

 

--Ethan