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Room Treatment

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Richardl60 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2017 at 8:05pm
Sound logic as ever Graham.

I must admit the door I tend to leave open is the one behind my listening position which not only will likely reduce the pressure loading but as a glass door reduce reflections also allowing the sound waves to disperse or travel into the dining room behind me.   Probably acts as an absorber too.

Yes I do remember FM from the mid to late 70's being on the warm side probably a little basss heavy but certainly lacking sparkle on a lot of material. The early commercial radio was less warm should we say.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2017 at 7:21am
What you are about to see - when I upload the photos of my "treated room" - will be a bit of a shock.

The "dead end" is the speaker end of the room, the one which has the absorption because it is where the acoustic power or sound pressure levels are greatest. Obviously sound pressure level is lost the further away from the speakers, and the loss is at 6dB per doubling of distance (unless a column array).

The "live end" is at the listening position end - in other words it is not treated (as such), although it has things which will absorb and diffuse such as the listener(!), his/her seat, and other things of importance to the listener's comfort or needs. At this end the sound pressure level is much lower and the effect on the sound of these things is less pronounced.

I have the system equipment at the "live end" because the sound pressure level is lowest there. The tradition has the equipment between the speakers, which is OK I suppose for a completely solid state system (i.e. computer source), but it is asking for trouble with a turntable or CD transport due to the high sound pressure levels vibrating it. A system placed there will also introduce unhelpful reflections.

The reason the photos will come as a shock is because the solution is not as neat as all those room treatment websites show. Is this because my room is a problem? No, the room dimensions make one of the best ratios recognised by acoustical science. OK, I mentioned a "pier" and a door, but I have yet to see a perfectly symmetrical domestic room, or one which doesn't have any compromises, like windows...

So, these neat acoustic treatments work? Then I've been wasting my time on all the research, absorber making, positioning and repositioning? I don't think so.

What the human mind might think is seldom what nature does. If we could only see what the sound is doing, it might help. If we are presented with a "solution", and it looks neat and professional, there is a tendency to trust in it. From what I've seen on the web so far, the offerings and advice look very dodgy indeed.

Do you really need any of it? Do you need 3D sculptures of a New York city skyline to magically diffuse your sound? Do you need ugly dust gathering foam rubber in all shapes and sizes stuck to your walls and ceilings? The most that will do is scatter high frequencies making the stereo image less precise, and at worst will increase coloration.

Fill your room with such things and you will have a dead anechoic chamber!

After all the experience I've had over the last 6 months of trying to improve my sound to make it more accurate for critical listening (which is part of my job), I see many of these treatments as being akin to the tablets you put in your fuel tank, supposedly to increase performance and reduce fuel consumption. And in tests such things don't work.

But what works is what I found to work, and it was hard work, but to my ears, isn't the be all and end all of room treatment, because, although far better sounding than when I started, it is not the holy grail. It is something we seek, but something I doubt we will ever reach. Until then it is, as ever, our best compromise to date.

That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2017 at 8:29am
Those tablets in the fuel tank were great; produced another 50 bhp and the car improved by 10 mpg on my 1.3 ford escort!   Only joking - looking forward to the photographs.......
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2017 at 8:40pm
Start with a good room and make it sound better Thumbs Up

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2017 at 11:11am
Photos as promised...



Leaving the packing and printing facilities in situ, the rest was moved into what was the R&D office. The electricians (Darfield Electrical Services) repositioned the lighting, and the partition wall, which was required to make the new R&D office have the right room dimension ratios, was begun.



I enlisted "diploma in site joinery" student Ryan Slee, to construct the partition wall (with help from dad...). The studs are proper "3x2" and not CLS which is too flimsy. The door frame also went in at this stage.



And then "the heavy wooden door". Better to use something which won't rattle like those cheap "eggbox" filled doors. This is a half hour rated fire door in the process of being hung. The studs were filled with 50mm rockwool during dry wall cladding. 12.5mm standard plasterboard both sides was used.



The result: this is the "live" end - the listening position end - the chair swung round and facing you and  positioned in the middle of the mat, gives the "sweet spot". The system rack is furthest away from the speaker end as is practicable - mounted to a dense massy wall section, the 19mm MDF backing is frame bolted to the stone work. This end also serves as general office, prototyping (left) and the CAD PCB artwork design (right). In answer to an earlier question from Richard, yes, there is a window, actually a door and side panel as can be seen (toughened kite marked glass - all 6 pieces - for security and safety). Reflections at this point will be minimal being at 90 degrees to the listening position, and there is a curtain which can be drawn across the glazed area, but the difference between it being open or drawn is difficult to detect. (Pile of muddy shoes under the desk is incidental...)



The view from the rack (to the left of the listening position). The unfortunate position of the door is because there was nowhere else to place it, and it couldn't be where the speakers are. The offset meant there was differing amounts of absorption from the stud wall, which is mainly at low bass frequencies. Also there is a pier in the right corner (easier to see in the construction photos), and this, as mentioned before, is dry lining straight onto the stone work. The side walls are dry wall over 50mm rockwool onto single skin stone work to the right, and double skin (cavity) concrete block to the left.



The room acoustics were good without any treatment, but not having any soft furnishings, the sound was on the brittle side (too much echo - a long reverberation time). Originally I'd put 12 absorbers on battens, arranged similarly to a BBC control room, copying what I'd seen in photographs. This proved too much, absorbing a lot of detail. It was then a case of tuning by ear, using several pieces of music, to ensure nothing was "blocked" by the absorption. The original pattern and positions of the absorbers changed considerably and the end result uses a total of 7 absorbers. The photo above shows the A2 style mid-bass absorbers used to the rear of the left hand speaker, all others being A11 style wideband absorbers.

The A11 type are used at the side wall first reflection points. Low frequencies from the speakers radiate into 4pi space until they reach the room boundaries, and like baffle-step, there will be a change in level where room reinforcement takes over. This can muddy the lows and mask the highs (and mids), and so the arrangement of absorbers (and their type) has to be painstakingly guessed at, and trialled so as to end up with the best possible imaging and subjective frequency range.

Room corners give the worst kind of reinforcement, and differing construction materials just serve to complicate matters. By placing modular absorbers like these close to a corner, they act in a similar way to a corner bass trap, and the two A11 wideband types behind the right hand speaker gave good results, absorbing artefacts of the much more reflective larger wall section on the right. It was found that the upper section wasn't being dealt with properly by a third absorber above the two, but by placing it on the right hand side wall, into the corner, as shown in the 5th photo, the image and subjective response was much cleaner and clearer.

The left side treatment did not work using the A11 type absorber - it took away too much low mid information - it was too wideband. This is why the A2 type absorber is used rear of the left hand speaker. It allows room reinforcement similar to just having plain drywall behind, because the A2 type surface is quite reflective, but absorbs where the lows become concentrated by the corner. You should be able to make out that the A2 type have much fewer holes.

Other adjustments found necessary were: the positioning of the desks so their edges nearest the speakers were of equal distance from the speakers - glancing reflections made identical; and the addition of a floor covering over the tiles - a rubber backed large entry mat.

The result has been that of hearing much more information from the music played thus far (a rather large eclectic collection). Quite revealing of style and studio techniques used, and a lot of things never heard before, which we're always talking about on here. Hopefully it will make it easier to discover which designs and tweaks will deliver more of that.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2017 at 7:21pm
Thanks Graham a good point of reference!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2017 at 8:48pm
Really good explanation, spot on!
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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