Large room, small room question....

Posted: Sun Mar 02, 2003 7:23 am

This whole question has gotten me thinking some....

Now I've always accepted the "conventional wisdom" on this but,(thinking out loud), I'm supposed to believe that the the small diaphram in the SM57 is usable at 40Hz, but somehow a room that's say, 13" x 10' x 7'6", won't be able to support these frequecies? I haven't thought about this much but it does strike me as kind of odd...

Ethan I'm looking forward to seeing some of the IBM data....

Posted: Sun Mar 02, 2003 9:22 am

http://www.recording.org/cgi-local/ubb/ultimatebb.cgi?ubb=get_topic;f=34;t=000057

Read this one, toward the bottom, Ethan states the truth, I back it up.

Posted: Sun Mar 02, 2003 12:58 pm

Well I guess all those high paid designers of professional commercial rooms don't know what you guys know. Very Happy

I say this with all kindness. I love you guys. But I have yet to see a pro facility that doesn't have large rooms other than Voice Over rooms. And this isn't to accommodate girlfriends. That is what the lounge is for. You can't do audio in a room full of people jackin' there jaws. And try to get five people who are just sitting around for five or six hours to keep quiet. If you want accurate bass response there is no way to achieve it without space. You can't surf in an aquarium. The laws of simple physics dictates this and all the want and wishing won't change those laws. Boundaries are boundaries and you can't make something that is 14 or 20 feet long form in a room that is 10' X 8' X 7.7'. It is a physical impossibility. I have no agenda on this. As I have stated previously, I wish what you are saying could be proved. I would be the first to jump on the wagon if it was. I would rather hear that my living room can be turned into a world class facility with a little bass trapping and some absorption. Now ‘scuse me while I kiss the Sky. I want some of what you guys are on. Very Happy

Love, Fats
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Posted: Sun Mar 02, 2003 6:31 pm

Hey Fats, how's it going? Long time no talkie...
Hi Bill, That's some of the stuff gettin' me thinkin'

I know what you're saying Cedar,

Quote:

Boundaries are boundaries and you can't make something that is 14 or 20 feet long form in a room that is 10' X 8' X 7.7'. It is a physical impossibility.

I always thought that too. That doesn't address the question as to how a 1" or smaller diaphram on a mic can reproduce it accurately though. Especially when that mic is inches from a 10" or 12" speaker!

Just thinking out loud......

Posted: Mon Mar 03, 2003 12:15 am

That would be a question for Stephen Paul. fats

Posted: Mon Mar 03, 2003 1:05 am

Ok fats, you inticed me, time to bring out the big old bag of dirty tricks.

See what time it is eastern? I got to leave for day job in 2.5 hrs but what the fuck.

I am going to try to do this where all can see, their is not absolute, it is always relative.

Here goes:

Reactance VS resistance.

First of all, you have a direct connection with the driver of the loudspeaker (like headphones that are flat to 15hZ) and you have an ambient connection (wave propagation) to the loudspeakers.

The property of direct connection we will call reactance. In electrical terms, reactance is the direct quality of what happens when you ask point A to transmit to Point B.

Resistance is the indirect or passive connection. Resistance involves the lack of direct connectivity and the travel of the source from point A to point B through a medium. Wire is a medium, air is a medium.

The impedance acoustically and electrically will change if a loudspeaker is presented with a wall or other impeading device (impedance)
You can take a cone loudspeaker (which varies in impedance from 4 to 90 ohms depending on the QTS, QES and QMS (electrical Q, mechanical Q and total Q) and simply by placing your hand in front of it, change all the quotients of the measurement in terms of all of the above. This is resistance. You are restricting the propagation of the wave with a boundary..thus changing the whole parameters of the device. A loudspeaker in an enclosure VS a loudspeaker in free Air has totally different properties. The location of a speaker system in a room will feed an eletromotive force back to the amplifier differently from one location to the next.

The system impedance curve is directly related to room location, enclosure dampning and crossover network, even the cable to the loudspeaker.

So , we have discussed reactance VS resistance.

Now, going deeper, with the crossover network, we can control this reactance VS resistance as we can with enclosure type but in loudspeaker design, what we cannot control is the variables of the rooms they are to be used in. To drive a point home, if the reactance is greater than the resistance, then you have a higher Q factor meaning the loudspeaker is effecting your hearing more as a direct sourse of air motion to the ear/brain, than what the room will provode due to wave propagation and distance. As the Q drops, you are working with a resistive device which become more room dependant and uses the room as a source of propogation. The really wild thing is all speakers exibit a different Q dependant on intensity, rise time, amplifier dampning, location, and even souce material. We can even control this reactance VS resistance of the wave shape in mastering! Honestly, you can get a solid 20HZ tone from a loudspeaker at 2 meters. The reactance of the connection of the wave shape to the tympanic membrane and the hearing system will extrapolate the tone and make it true. When running high pressure levels (as in a car stereo that has (6) 12" woofers, tuned to below 20hZ) the reactance is immediate and pure. It is a direct connection of the wave to eardrum or tympanic membrane.

Now, look at the damn time..

Lets take this deeper later.

Questions anyone??? (yea..right..)

Posted: Mon Mar 03, 2003 6:44 am

Fats,

> If you want accurate bass response there is no way to achieve it without space. <

Does this mean you heard back from John Storyk and Russ Berger?

> The laws of simple physics dictates this ... It is a physical impossibility. <

Please tell me which law, and how it applies.

> I would rather hear that my living room can be turned into a world class facility with a little bass trapping and some absorption. <

Well, more like a lot of bass trapping...

--Ethan

Posted: Mon Mar 03, 2003 8:36 am

....

Posted: Mon Mar 03, 2003 10:33 am

Bill,
Your last post was about 50 feet over my head. Very Happy

Didn’t understand a single word.
THE MASTER
No I don't really understand acoustics a lot. I am relating things that were told to me by Michael Gore, Chips Davis (inventor of the LEDE room) and John Storik when I was building my room in the early 90's. I never claimed to be an acoustics expert. As far as room dimensions, I was told that 14 feet is the "magic" number for what would be termed a “legal room”. I have never seen a pro room with less than 14 foot minimum dimension. Period! If all of this is true, (small rooms ok) why isn't it done? All pro rooms have high ceilings, (girlfriends don't sit on the ceiling or the walls) and minimum dimensions of 14 or more. Once again I'm not saying that a small room can't be useable, look at Sun Records, the control room wasn't much bigger than a phone booth, but if the goal is to have an accurate bass response, then a large room is in order. I had a space that was 21’ X 40’ and had an 8 foot ceiling. I tried to get Chips Davis and Michael Gore to tell me a way to make it into the control room. All I could get from them was, "Blow out the ceiling". Once again, all I am doing is relating what I have been told by people who have made mega hit records, worked with guys like Neil Young, tom Petty, Colombia Records (as a mastering engineer btw in the case of Michael Gore) and designed some of the largest studios in the world. Ethan, no I haven't heard back from Storik/ Walters or Russ Berger Groups as of yet. If I do you may be sure I will let you know, no matter what the answers. I am not so pig headed as to not admit if I am wrong. I find no shame in something like that. As you have pointed out , the main reason for all of this discussion is to try to learn something. ……. Fats
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Posted: Mon Mar 03, 2003 11:00 am

Fats,

> As you have pointed out , the main reason for all of this discussion is to try to learn something. <

Of course. But let me try to explain it one final time, while waiting for your guys to reply:

You put your speakers outside where there are no walls at all. We both agree that with no walls, any frequency can be played through the speakers. Now you build walls and a ceiling. So what changed that might affect low frequencies? What changed is that you now have reflections off the walls and ceiling that combine with the direct sound from the speakers. The combining is both constructive and destructive, which is why you get both peaks and dips. Okay, so you install bass traps - enough to cover a significant portion of the surface area. Now you no longer have those reflections, or you have enough less that the combining is less damaging.

Here's another way to look at it: Suppose you build walls out of tissue paper. We both agree that will not do anything to the low frequencies. Now you replace those with heavier paper. It still won't affect the lows, though maybe the highs will be reflected a little. You keep making the walls heavier until the reflections affect lower and lower frequencies. The point I'm trying to make is that it's the reflections that cause problems, and nothing else. Since bass traps reduce the reflections, they make the room seem acoustically much larger.

--Ethan

Posted: Mon Mar 03, 2003 11:13 am

Ethan said,

Quote:

You put your speakers outside where there are no walls at all. We both agree that with no walls, any frequency can be played through the speakers. Now you build walls and a ceiling. So what changed that might affect low frequencies? What changed is that you now have reflections off the walls and ceiling that combine with the direct sound from the speakers.

Ethan,
What has changed also is you have introduced a boundary. You have contained the wave. By adding absorption you don’t make it possible for the wave to pass through the wall any more than it would be possible for you to walk through that same wall. Whether it is in a padded box or a hard box only effects the reflections not the containment. That's all I am saying. Like I said, you can't surf in an aquarium. Fats
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Tannoy, Dynaudio, Blue Sky, JBL, Earthworks, Westlake, NS 10's Very Happy

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Posted: Mon Mar 03, 2003 12:26 pm

Fats,

> What has changed also is you have introduced a boundary. You have contained the wave. By adding absorption you don’t make it possible for the wave to pass through the wall <

Why do you think the wave has to pass through the wall? And why would that make a difference within the room anyway?

> Whether it is in a padded box or a hard box only effects the reflections not the containment. <

And the difference between containment and reflection is ... ?

There are things I'm not sure at all about, things I am fairly certain of, and things I am absolutely positive about. This issue falls into the last category. Very Happy

Posted: Mon Mar 03, 2003 1:12 pm

Ethan asks;

Quote:

Why do you think the wave has to pass through the wall? And why would that make a difference within the room anyway?

My point is there shouldn’t be a wall for the wave to have to pass through or reflect off of. My concept is, if a bass wavelength is 14 feet long, the room needs to be 14 feet long for the wave to form accurately within it. I think that’s pretty simple.

I have now asked Michael Gore to join the conversation here. I hope he will. He is very well versed in this subject and my hopes are that he may be able to set one or the other of us straight on this. He is usually very busy and I am sure he won't respond until at least this evening. So until then, I'm outta here. .... Fats
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To help keep this site alive and growing, please show your support by purchasing one of our caps, studio clocks, T-Shirts etc. Banner ads too!
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Tannoy, Dynaudio, Blue Sky, JBL, Earthworks, Westlake, NS 10's Very Happy

, Genelec, Hafler, KRK, and PMC
Those are good. …………………….. Pick one.
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Posted: Mon Mar 03, 2003 9:20 pm

....

Posted: Mon Mar 03, 2003 10:24 pm

Hi Fats,

Have been reading your comments and have to step in Wink

:
1. Ethan is right, simple as that. I did study quite some acoustics and have seen a lot of pro-studios that don't have 14' ceilings (check the Fran Mancella site).
2. if you were right, how would you explain "headphones"? Seems like very small spaces being able to produce sub 100Hz tones?

Nothing personal here, but try to understand what Ethan is saying, cause it won't be possible to explain it much better IMHO...

Greetings,
Dirk

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