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Audio For Dummies ™
Topic: Room acoustic

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Posted by Romy the Cat on 04-05-2005

When I come to listen somebody’s system then the first thing that I usually do is taking a possession of remote control explaining that I‘m a control freak and gently smiling…. In reality the thing are far from being so simple. The very first thing I care it to play an orchestral peace with cellos and violas group to pose the CD transport. The tempo with which music decays in the listening room when music is aborted instantaneously (electrically) is one of the most important ingredients that would be responsible for Sound in this room.

Without diving in the nuances of the RT60 tests, how to do them properly, how to interpret the results and, the most important - how to USE them I would like to recommend to audio people: learn to listen how your rooms decay in response to sound. If you look at this sufficiently enough and thoughtful enough, and if you correlate your observation with the type/topology of the acoustic systems "in use" then you might develop some very powerful observations.

In general: when you pose your CD transport your room should not go silent but Sound should very softly and gradually decay to a noise level. The softens, the length, the harmonic content of this decay should be the primary target of your interest and attention…


Posted by ArmAlex on 03-28-2009
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Is this test just for CD player? will you explain a littel more
Thamks,
Armen

Posted by jessie.dazzle on 03-28-2009
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If you discover the decay seems quick, try comparing it to what happens when pressing the resume/play button. You may then perceive that the music starts up much more instantaneously than when cutting off the source of sound (pausing).

jd*

Posted by jessie.dazzle on 03-28-2009
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Apologies, posted to quickly; should have written the following :

You may then perceive that the music starts up much more instantaneously THAN IT DECAYED when cutting off the source of sound (pausing).

Posted by ArmAlex on 03-29-2009
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Thanks for reply. But I'm confused,Romy says"In general: when you pause your CD transport your room should not go silent but Sound should very softly and gradually decay to a noise level"Ok we can listen to this but what can we do to improve if the decay is not the way it shoul be?
Armen

Posted by Romy the Cat on 03-29-2009
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This is very complex question and since you ask too generic question I would not feel that any answer is warranted. Generally you would never have the right decay in playback system as you will get 1.5 sec of reverberation time at 50Hz in 3000-5000 sq feet. Audio systems do not work in those spaces and listing rooms are way smaller. The measurable demands for delay of playback an installation is VERY tricky subject – discard anyone who says that they know what they are taking about it. Obviously you need to peruse to lover order crossovers and to the driver and configuration that are able to work with lower orders. Avoid any room treatment at low frequency - fine that idiot who invented the BassTraps and stick them into his stupid ass. The plated lording is very powerful tool, the delay channels (properly done) is even more powerful. There are many way and there are even more “depends from…”. It all depends what you are trying to accomplish and what technical recourses you have in your playback to deal with it.

Posted by drdna on 03-30-2009
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 ArmAlex wrote:
what can we do to improve if the decay is not the way it should be?
Armen
Change the elements of the room that are creating the problem. The mistake is to use electronic means to try to compensate for the room. It doesn't work well.
Adrian

Posted by ArmAlex on 03-30-2009
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Lets go into more detail. I'm very new to audiophiling-a year and half-which half of it wasted by Moronizm.
Anyhow a friend of mine(Amir who runs a blog about audio) introduced this site to me, and I saw the "real thing". And I specially am obssesed by DPoLS and with Amir's help we moved he speakers to hundreds of places during past 6 months. Now we think we have found optimum zone, as sound started to change dramaically. So I read whatever I think would be helpful to find DPoLS in this site, and I think listening to room has a important role in DPoLS(correct me if I'm wrong).Hence my interest in "listening to the room".
I don't use any room treatment, my room is very big(34x42x8 feet) and I think acoustically its not bad.
Please have a look the picture in attached file.
I'm looking forward for your advise(s).
Many thanks,
Armen

Posted by Romy the Cat on 03-30-2009
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Armen,

If you look somebody to advise you in specifics then you are talking to a wrong person – I do not do it. Well, I do it but ONLY if I feel that the area of attention is very narrow and the question is well-understood by the person who asks. I do not think that that we will have a dialog about… hold on let me to figure out what we are talking about…

I am glad that you took upon the DPoLS – people have no idea how powerful it is but I am worn think to talk about it. If a person knows than he does not need any DPoLS evidenced from me. If a person does not know (the majority of them) than any of stories about DPoLS he recognize as another BS that his brain has already stuffed up.

The "listening to the room" is NOT the DPoLS subject in my view, however, if you feel that it is then it is fine with me.

The Cat

Posted by ArmAlex on 03-30-2009
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Dear Romy,

I know it's impossible for you to answer to everybody especially a rookie like me. And I deeply appreciate whenever you’d reply, but you know, you and a very few people in your site are the only reliable source.
Regarding DPoLS I strongly believe that there is such a thing and that’s why I’ve already spent 6 months to find it. Also I already have the evidence, it is huge difference I heard when just entering in the optimum zone.

Armen


Posted by jessie.dazzle on 03-30-2009
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Here's what I would do.

In general :

Start by excluding the DPoLs, excluding the electronics and associated gear, and considering just the room.

With no electronics functioning, is the room an acoustically pleasant space ? Invite friends over and get them to talk; carrying on two separate but simultaneous conversations in this one space should be effortless and non-fatiguing for all concerned. 

Once alone, pick up a book; is this room a nice place to read ? Can you concentrate ? (I find this "test" most revealing). 

Does your dog seem at ease in this room ?

To me all of the above should be part of what the French would call normal "savoir vivre", but it is not, and I am always shocked to learn that friends of mine endure acoustically horrible home environments.

More specifically :

From the photo of your room there seems to be adequate space, however the many hard, parallel surfaces are likely to propagate echoes (bare parquet floor, bare walls, window off to the right, bare ceiling... At this point, that  big, woolly dog is probably the most effective part of your system!). The surface treatments of your room are typical of those found in certain regions, often having a very warm climate, or, in other cases, of the residences of people who are most concerned with ease of maintenance (ceramic tile flooring is a favorite of these folks...). There are reasons why slaughterhouses and morgues have tile flooring, and its got nothing to do with acoustics. Do you sing in the shower ?

In fact, the photo of your room reminds me of the corporate restaurant at the place where I work; I'm not at all exaggerating when I say the acoustics of this place result in indigestion, and are problematic to the extent that everyone complains, but the room is easy to keep clean.

Assuming fixed dimensional geometry, the optimization of an overly live or dead room can be accomplished to a great extent by adding/subtracting normal furnishings and surface treatments; that is to say, without resorting to expensive "official" audiophile-blessed room treatments.

You may also want to consider adopting a few really fluffy feline friends for that nice big dog.

jd*


Posted by ArmAlex on 03-30-2009
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Actually my listening room is quiet neutral acoustic wise, maybe it’s because of ceiling which is wholly covered by wood bars which are very old and not prfect so acting as a big diffuser-picture in attachment. Also a lot of sound-absorbing furniture and carpets. Pino and his father Toby usually sleep under my listening chair during my listening sessions which is pretty loud (you could ask my wife!) At one time I tried a relatively big carpet just in front of speakers and it completely ruined the sound
Many thanks,
Armen

Posted by drdna on 03-31-2009
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There is a lot on this site about room treatments, if you take the time to look for it. For example remember this from a few years back? I suggest you browse the site for a while.

If you have a frequency analyzer you can move your microphone around the room and find out where the abnormalities are. You can then proceed to address those points directly.

With your carpet fiasco, I am guessing you lost the bass reinforcement from the reflective floor. The room adds a lot to the sound you hear, and you want to treat it as an active dynamic element, rather than trying to dampen it totally.

After looking at the pictures of your room ,I would consider getting some nice house plants, big ones and putting them around the room, in front of the stereo, behind the speakers, to kind of give a more relaxed feel to the room, plus they will help with the cancellations.

A long time ago, when I had electrodynamic speakers like yours and they were very close to the wall like yours, I had to wrap them up in egg crate to reduce the back reflections. I am surprised it is not an issue. This may be why you have your speakers toed in so much, as compensation.

Adrian

Posted by ArmAlex on 03-31-2009
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Dear drdna,
Thanks a lot for reply and helpful advises actually this is the only site I read these days. That problem with carpet was not low frequencies alone, surprisingly it did a lot more damage. Will you explain more about egg crate, my speaker distance with rear wall is about 5 feet and with side walls 10 and 15 feet respectively.

Armen

Posted by Amir on 04-05-2009
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 Romy the Cat wrote:

The "listening to the room" is NOT the DPoLS subject in my view, however, if you feel that it is then it is fine with me.

The Cat


I agree with romy , I think DPOLS help us to find the most neutral zone in room but dpols can not give us one result with all rooms.
my friend room (Armen) in my idea is far better than my room and i think finding dpols in armen room turn system to very high level of musicality but in my room in never got that result with macro positioning.
my room is so reflective with large parallel un-treated walls and though i find a good position (for my speakers) but sound texture is bad and i think this bad texture is result of my room response to sound.

another thing that we should be aware about decay of sound after stoping transport is ground loop problem, if the system not properly installed and there be ground loop in system after stopping transport electronics system push some energy and influence decay of room.

for hearing room decay you should first remove ground loops if they are in your systems.


Posted by twogoodears on 08-31-2009
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JD's post contains several interesting tips and hints: talking of walls and floors is important like and possibly more than talking about a pleasant, cocooning space where to find themselves in music and reading and relaxed chatting with friends and relatives.

I find miself agreeing about such a character of the room, me and my wife always called (in italian) "La stanza della Musica"  - i.e. the music room - where music is lived, absorbed, discussed, enjoyed, played.

I also read in the dimmed light, with no music at all, and, most important, I also play - alone or with friends and practice by myself, on acoustic and classical guitar and, more recently, on oud.

The sound of the music room is very different from other rooms in my home - I'd define it as "sweet" sounding.

Many years ago I had a kilim carpet from Konya (Turkey) over the black marble floor, but when I throwed it somewhere else, I improved  music reproduction from my audio system.

Also without a carpet, the reflections are apparently very low - thousands records and hundreds books and guitar cases and plants an curtains, all works in, as I jokingly say, "distracting" reflections...

I also record  - myself or freinds - in this very same room: acoustic guitar, oud, theorbo or lute... with a Blumlein-patterned Neumann's USM-69 at 2 meters from instrument with analog tape... well, the results are often surprising.

It's not an anechoic room, but sweety and lively... so, I'd add to JD's list for a nice, proper room for home music - if a room sounds good (unboomy/undull/pleasant) for playing an acoustic instrument, it's another signal for a music-friendly room also good for audio.

... my dog also love to sleep - more like a cat, than a dog, actually;-) - in my music room. 

... but don't try to play "Beauty in the Beast" by Wendy Carlos or Windham Hill Records "Guyto Monks"' growling vocals... my dog will sure bark at speakers!   

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