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Discussion Starter · #1 ·
As I've been researching how to use acoustical treatments I've seen a lot of information on being careful not to over deaden a room. Makes sense. Can someone describe what an over deadened room sounds like? I've heard people say that such as room does not sound "lively" but I'm not sure what a lively room sounds like.

Is it fair to describe an overly deadened room as one that sounds somewhat muffled? I was in someone's room that I think was over deadened. The owner himself told me the room was "bordering on being too dead" and I noticed as soon as we stepped inside it an started talk (with no audio playing) our voices sounded "flat" to me, somewhat muffled, like it was missing the higher frequencies. It was quite noticeable and I think I would have noticed it even if he didn't mention anything. Did I indeed experience a deadened room?

If one was to measure a room that is over deadened, what would the measurements made in REW look like compared to if the room was treated "just right"? For example, are there certain technical measures or tolerances for defining such things, such as "you shouldn't see xyz below abc in this range compared to that range". IOW would somewhat that knows what they are doing be able to look at a measured frequency response in REW and tell that the room was over deadened, and if so, what would they be looking for to make that determination? Same question about identifying a room that was too lively or bright. Thanks!!
 

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REW Impulse, using DB Fs scaling - selectable at the top left of the graph when you move your mouse to that area, shows how sound level in your room drops off with time

The Filtered IR graph can do it for different frequency bands.

At least, that's my interpretation of the display.

 

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Discussion Starter · #3 ·
REW Impulse, using DB Fs scaling - selectable at the top left of the graph when you move your mouse to that area, shows how sound level in your room drops off with time

The Filtered IR graph can do it for different frequency bands.

At least, that's my interpretation of the display.
Thanks. What should one look for in these graphs to assess whether the room is too lively, too dead, or just right?
 

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Thanks. What should one look for in these graphs to assess whether the room is too lively, too dead, or just right?
I think the initial drop - 20dB or more is 'good' - the direct sound isn't obscured.

After that, the slope of the drop. The time it takes to get back to the baseline. Longer time = more lively.

Little spikes during the drop are reflections. I have one at 26ms, seems to be when the soundfield returns to the microphone after reflecting off the wall behind the microphone, and then off the wall behind the speakers and hits the mic again.

How much is too much? Too little?

That's a judgement call, or fodder for the 'experts' to have a 'debate'. I think mine is about right, not dead, not echoey like a bare room. It just has a little resonance.

My room is 'untreated', except for 8 pieces of 7x24x48 rockwool, carpet, a couch. 3 rockwools in the bottom corner behind each speaker, and 2 standing up behind the couch (blocking PC fan noise), and the reflection from the wall behind the couch (at least at ear level).
 

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I think the initial drop - 20dB or more is 'good' - the direct sound isn't obscured.

After that, the slope of the drop. The time it takes to get back to the baseline. Longer time = more lively.
Does this graph represent the combination of all frequencies? If so is it basically like a waterfall except organized by all frequencies for each point in time?

Longer time = more lively - got it, makes sense. So what would generally be considered the right amount of time that the slope should drop off at for a properly treated room? How fast does a deadened room drop off at, etc?

How can you tell if its too dead in just certain frequencies? Like to make sure that your are not absorbing too much of the high end (according to measurements, without trusting your ears)?

Little spikes during the drop are reflections. I have one at 26ms, seems to be when the soundfield returns to the microphone after reflecting off the wall behind the microphone, and then off the wall behind the speakers and hits the mic again.

How much is too much? Too little?

That's a judgement call, or fodder for the 'experts' to have a 'debate'. I think mine is about right, not dead, not echoey like a bare room. It just has a little resonance.

My room is 'untreated', except for 8 pieces of 7x24x48 rockwool, carpet, a couch. 3 rockwools in the bottom corner behind each speaker, and 2 standing up behind the couch (blocking PC fan noise), and the reflection from the wall behind the couch (at least at ear level).
Well, I'd hardly call that untreated. :)
 

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Does this graph represent the combination of all frequencies?
I think so. it is unfiltered. Filtered IR gives you other choices, by a list of frequencies or frequency bands.

lovingdvd said:
If so is it basically like a waterfall except organized by all frequencies for each point in time?
I think so. It shows level by time.

lovingdvd said:
Longer time = more lively - got it, makes sense. So what would generally be considered the right amount of time that the slope should drop off at for a properly treated room? How fast does a deadened room drop off at, etc?
Don't know. I'm not a pedigreed acoustician nor pretend to be.

lovingdvd said:
How can you tell if its too dead in just certain frequencies? Like to make sure that your are not absorbing too much of the high end (according to measurements, without trusting your ears)?
Use the Filtered IR graph, and select frequencies of interest. Mine are pretty similar, though the lows seem to die more quickly than the highs, a little, and maybe.

lovingdvd said:
Well, I'd hardly call that untreated. :)
Yeah, well, I was trying to tame a little LF resonance (experimentation). And seeing what would happen to a 50Hz hole I have, that bothers me when measuring but doesn't bother my ear, and the PC cpu is on the floor behind the couch, wanted to kill the fan noise at the listening position. It worked.

But I don't have panels all over the walls and hanging from the ceiling and stuff like that.

Just bringing the bags with the rockwool still compressed inside into the room seemed to make an audible difference. Added some deadness to the ambience.

I might cover them sometime, make them look fancy. WAF is not a problem here.

http://www.lowes.com/pd_122333-1278...urrentURL=?Ntt=roxul+23-in+x+47-in&facetInfo=

They are soft, but still firm enough to stand up on their own or hold their shape pretty well. Not fiberglass, so not itchy. Has sort of a fine sandy feel when you rub your hands after handling them.
 

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Is it fair to describe an overly deadened room as one that sounds somewhat muffled? ... like it was missing the higher frequencies.
I'm not an expert, but I think you are right. An overly deadened room would probably sound muffled, unless your listening position is very close to the front speakers. Also, it would sound less complex, due to the higher frequencies not bouncing around as much. Complexity is one of Berlyne's cortical arousal increasing variables, so a very dead room might sound dull and uninteresting, and not wake up your brain as much as a good room. Of course an overly live room has its problems, too. IMO, the more varied the room surfaces, the better, including some soft absorbent materials (overstuffed chair, carpet, etc.) and some hard reflective surfaces that are not flat (vases, etc.). If a room is to be treated, I like a combination of absorbers and diffusers, with absorbers at the first reflection points. Sales people sometimes encourage people to put too many absorbers in a room.

I have suspected that some of the reviewers in Stereophile have pretty dead rooms. I think they measured a YG speaker -- of very high reputation -- as being 10 dB down at 15K, and a Vandersteen at -7.5 dB, also at 15K, both in one of their reviewer's rooms. Audyssey recommends their in-room Reference roll-off of about -2 dB at 10K, and -6 dB at 20K for movies in typical rooms, but, for very highly treated rooms (probably pretty dead), very close to the speakers, they say that Audyssey FLAT might be better (20 -20K, as flat as Audyssey can get it in that room).
 

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Can someone describe what an over deadened room sounds like?

Is it fair to describe an overly deadened room as one that sounds somewhat muffled?

Did I indeed experience a deadened room?

If one was to measure a room that is over deadened, what would the measurements made in REW look like compared to if the room was treated "just right"?

For example, are there certain technical measures or tolerances for defining such things, such as "you shouldn't see xyz below abc in this range compared to that range". IOW would somewhat that knows what they are doing be able to look at a measured frequency response in REW and tell that the room was over deadened, and if so, what would they be looking for to make that determination?
Good questions!

Google RT30 - RT60 measurement. Steer away from verbal descriptions, such as muddy and personal subjective opinions. Measurement will put objective numbers in place of subjective words, which are also limited by a persons vocabulary, bias, and experience in listen to music.
 

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Ray's thinking along the right lines, but IKM hit the nail on the head. Reverberation time vs. frequency is how you characterize a room's acoustic decay. I prefer spectrograms, another REW option, to waterfalls, something like this:
Text Colorfulness Line Organism Wave


The goal is two-fold
- get 40-50dB of decay within ~0.3 sec.
- have nearly equal decay at all frequencies. This may be hard to do in the lower bass range, as you can see above, for residential-size rooms.

I find it convenient to set the chart options for 10dB contours, as crossing 4 contours is then 40-50dB decay. This is the same data as a waterfall, but nothing is hidden behind a strong resonance, as the level (color) is independent of position on the chart. I took this data when playing with subwoofers, but ideally you'd like to measure to at least 10KHz.

Your preception that the room you describe was missing high frequencies is likely right, as it gets easier to absorb sound as frequency increases. That's what makes bass issues so hard to address. Regardless, you're asking the right question first - how to measure, what's a reasonable goal and where does my room sit? Once you've defined a gap to a desirable goal, half the battle's over!

Have fun,
Frank

PS good measurements also require a large contrast; so if your room's not terribly quiet (low noise floor), you'll need to measure at quite high SPLs. You can't measure a 50dB decay if your 100dB signal is on top of a 50dB noise floor. Start very quiet and measure almost uncomfortably loud.
 

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As I've been researching how to use acoustical treatments I've seen a lot of information on being careful not to over deaden a room.
the primary context with respect to the statement is not to over-deaden the highs while allowing the low/mids to persist - which is quite easy to do in small bounded spaces via the use of large sq area of thin porous absorbers.

Is it fair to describe an overly deadened room as one that sounds somewhat muffled? I was in someone's room that I think was over deadened. The owner himself told me the room was "bordering on being too dead" and I noticed as soon as we stepped inside it an started talk (with no audio playing) our voices sounded "flat" to me, somewhat muffled, like it was missing the higher frequencies. It was quite noticeable and I think I would have noticed it even if he didn't mention anything. Did I indeed experience a deadened room?
there's two different "perspectives" at play, and you need to define which you're referring to in these types of conversations when discussing how a room "sounds".

first:
source: speaker
receiver: listening position

the speaker-room response is from the speaker's perspective into the bounded acoustical space. the speakers emit energy (generating sound) and the shape (geometry) of the room determines how indirect energy (reflections) impede the listening position over time. the characteristics of the indirect energy imposed by the room are incorporated into how the ear-brain perceives the direct signal from the speaker - and thus changes the "sound" of the speaker.




second:
source: listener's voice or other sound generated by the listener within the room
receiver: listener's ears

the human-room response is from the listener's perspective and has to deal with how the room sounds ("feels") to you as you talk or move about (making noise) in it.



so the room imposes different "mask" on the signal based on which "perspective" you are viewing from. this is why "first order reflection points" change as either the speaker or listening position are modified.

however when discussing whether a room is "dead" one needs to provide context of one of the above perspectives. one can modify or design a room such that there are no indirect reflections from the speaker imposed on the listening position by the room geometric - which would create a dead (anechoic) speaker-listener response - but would still have reflective walls that would reflect listener-generated sounds back into the room. this allows the room to still feel "comfortable" (lack of "suck-out") to be in, while still having no distortion (indirect signals; completely dead) from the signal generated from the speaker.
 
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