monitoring/acoustics questions

general questions, comments and ideas about recording, audio, music, etc.
memes_33
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monitoring/acoustics questions

Post by memes_33 » Tue Oct 19, 2004 3:12 pm

I have been reading a lot lately about acoustics, especially in small rooms, and believe this to be (at least one) reason for my immobile mixes. I have a few questions about information that seems in contrast with one another. First, it is widely recomended not to compensate during monitoring with EQ, but many (at least active) monitoring systems have a "bass compensation" or "room compensation" switch for smaller rooms and less-than-ideal speaker placements. Wouldn't this "room compensation" switch be a form of EQ? Second, some diagrams I have seen in Ethan Winers' articles suggest dips and peaks of up to 35 dB in certain frequencies (http://www.realtraps.com/art_vibes.htm). I have also read (as well as experienced) that mixing with headphones yields undesirable results because of the somewhat rocky frequency curve. I know I'm missing something here, but wouldn't a "flat" set of headphones possess a more favorable mixing environment than a room with this many nulls and peaks? What is a renter to do about these acoustic gremlins in their control room? Any help would be appreciated.
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I'm Painting Again
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Re: monitoring/acoustics questions

Post by I'm Painting Again » Tue Oct 19, 2004 3:30 pm

Hire a acoustic physicist and a master architect ?

not too many people on this board are experts on the subject..but Ethan might show up..and others usually have some great insight..i dont know anything good about room acoustics..

there is a great forum for studio design someplace..ive seen it before but im not sure where it is..

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Re: monitoring/acoustics questions

Post by I'm Painting Again » Tue Oct 19, 2004 3:32 pm


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Re: monitoring/acoustics questions

Post by 8th_note » Tue Oct 19, 2004 5:08 pm

I was having trouble with my mixes (too bassy & muddy) so I put an inexpensive 12 band equalizer in my monitoring setup that I had laying around. I adjusted the eq to approximate an average of several systems that I listen to and are representative of what the average listener might use. I ended up goosing the lower midrange frequencies and making a few other adjustments.

I don't care what the experts say - this worked. My mixes improved dramatically. I've continued to refine the eq and things have continued to improve.

I use a pair of Polk bookshelf speakers and a low cost subwoofer as my monitor setup. Someday I'm sure I'll upgrade to a good pair of monitor speakers that may not need the eq but for now this setup works really well.

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Re: monitoring/acoustics questions

Post by I'm Painting Again » Tue Oct 19, 2004 5:14 pm

eq-ing the monitors seems to be a fairly common practice..to me its a logical work around..but if done incorrectly it can probably cause more harm than good..i dont really know too much about this stuff..i would love to hear some expert opinions..

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Re: monitoring/acoustics questions

Post by jajjguy » Tue Oct 19, 2004 7:05 pm

It IS possible to flatten the frequency response of a particular monitoring situation IF you know the precise location of the speakers and the listener AND these positions won't change. So, like, don't lean over to tweak a knob or something and expect your EQ room-tuning to still work.

The reason for this is that small rooms resonate with lower frequencies and this produces louder and softer locations for many different frequencies in your room. Move a few feet and everything changes.

The bass rolloff switches on some speakers (such as Mackie 824) have recommended settings depending on the placement in the room -- if the speakers are near a wall or corner, they'll send more bass toward the listener. So the switches can help with this particular placement issue, but not with the room's low freq problems. [edited for correctness (oops)]

Headphones create a very small room of their own: the air trapped between them and your head, including your ear canal. This can create ripples all up and down the spectrum.
Last edited by jajjguy on Thu Oct 21, 2004 3:03 pm, edited 1 time in total.

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Re: monitoring/acoustics questions

Post by wwsm » Tue Oct 19, 2004 8:00 pm

IMO, people who can't do too much construction in their control rooms have to rely on a variety of cures to get close, and then "learn the sound of the room". Building an accurate and reliable control takes work, but hopefully you can get closer than where you're at now. The thing you have in your favor is time. If you can try a few ideas out, you should find a combination that will work for you. Some things may only even out the frequency response in a specific place (hopefully your mix position), but at least you'll be gaining knowledge about what's happening in your room. Here are a couple of thoughts...

1. Build a few of Ethan's bass traps. I know a few people who have built them and had very good results. Try them in different locations and see which feels best. Ethan's website is really helpful.
2. Move your speakers around. Speaker placement in a room can make a huge difference. You may need to re-design your equipment layout if you find a better location for your speakers.
3. Borrow a good stereo EQ and try to lightly balance out a curve that feels good to you. Like 8th note says... It can work even if it's not the ideal solution. If it does work, you may also have a better idea as to what you need to fix as well (a main problem with this is the phase distortions that you'll introduce into your monitoring chain by adding the correcting EQ). This is best done with the aid of audio analyzers, but maybe you could download (or purchase) a simple program for a PC that could get you started.
4. Check your mixes on headphones. I think mixing with headphones can be way too deceiving. But checking your mix on a pair you're familiar with is a good idea.
5. Borrow a subwoofer. Although I'm not a fan of using a subwoofer in a stereo playback system, it could help. Make sure you use your mains as satellites (avoiding a build-up with the sub), and experiment with placement, overall volume and direction. Many people have success with placing them in corners, try at least a few different locations.
6. Re-read those books on acoustics.

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Re: monitoring/acoustics questions

Post by Ethan Winer » Wed Oct 20, 2004 8:33 am

Keith,

> Wouldn't this "room compensation" switch be a form of EQ? <

Yes, but that's different from how people usually approach EQ to "fix" their room response. There are two different issues, and the switches built into active speakers address only the simpler one.

When a sound source is moved closer to a room boundary or corner the low end rises linearly. That is, the closer you get, the more the overall low end is boosted. This is equal to a low frequency shelving boost on an EQ, or a standard "bass control" on a hi-fi. The switches on active monitors are also simple shelving controls, and they apply cut to help compensate for the boost resulting from placement.

A far larger problem - the main reason people have so much trouble mixing in small rooms - is the low frequency comb filtering that occurs from sound bouncing around in a room. This has nothing to do with proximity boost, and it's impossible to compensate for with EQ. As was already mentioned, even if you could compensate for the exact curve, as soon as you lean forward even a few inches in your chair the compensation fails. The graph below is from my Vibes article you mentioned, for the benefit of others. Note that this is absolutely typical of the low frequency response in small rooms.

> What is a renter to do about these acoustic gremlins in their control room? <

See my company's web site. :)

--Ethan

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exit2studios
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Re: monitoring/acoustics questions

Post by exit2studios » Wed Oct 20, 2004 2:50 pm

These topics come up often here, and I know Ethan getes asked this question A LOT, but:

I would like to find a supply of Corning 703/705 in my area. I live in Dallas, TX.

Is there a resource somewhere that would list places that sell this stuff. I've looked briefly with no success.

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Re: monitoring/acoustics questions

Post by Ethan Winer » Thu Oct 21, 2004 9:36 am

E2,

> I would like to find a supply of Corning 703/705 in my area. I live in Dallas, TX <

This place has a number of outlets in Texas:

www.spi-co.com/servicecenterdirectory.mv

--Ethan

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Re: monitoring/acoustics questions

Post by mjau » Thu Oct 21, 2004 10:36 am

One thing that dramatically improved my room was spending a couple hundred bucks on 3" and 4" foam panels and some bass traps. I ended up getting 144 sq ft of panels, and with the traps, they not only deadened the high frequency echos I'd get, but I think also helped with low frequency absorption. I can hear more bass in my mixes now because of this - and consequently, my mixes are not nearly as muddy. Simply solution, not a fix-all, but worked for me at relatively little cost.

memes_33
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Re: monitoring/acoustics questions

Post by memes_33 » Tue Oct 26, 2004 2:36 pm

Thanks everybody. Very helpful indeed. One thing I intended to ask about on my last post- what effect would objects in between the monitors have? I have my monitors on a bookshelf with manuals, books, and old tape ops in between them (using the monitors as book ends). How much might this effect acoustics?
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Ethan Winer
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Re: monitoring/acoustics questions

Post by Ethan Winer » Wed Oct 27, 2004 10:11 am

Keith,

> what effect would objects in between the monitors have? <

If they're not in the direct line of fire, it shouldn't be a problem.

--Ethan

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Re: monitoring/acoustics questions

Post by Red Rockets Glare » Wed Oct 27, 2004 10:31 am

DO bass traps have to be sealed in a corner to function properly?
I made some that aren't, and they certainly help, but I still end up putting too muck kick in my mixes 9 times out of 10.

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Re: monitoring/acoustics questions

Post by Ethan Winer » Thu Oct 28, 2004 9:37 am

Red,

> DO bass traps have to be sealed in a corner to function properly? <

It depends what type they are and what they're made of. What did you build, and how many?

--Ethan

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