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Bass Traps & Sprung Ceiling

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Graham Slee View Drop Down
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    Posted: 22 Feb 2017 at 11:29pm
Finally achieved "studio sound" from my new office/workshop/listening room.

Found the best bass traps ever, and only £38 each complete with plastic covers LOL

Bass Traps

Also finally found the remaining boomy bass culprit - the "sprung ceiling".

Modern building methods are rubbish! Once upon a time the plaster board for ceilings was screwed or nailed directly to the underside of the joists - which are very stiff so the ceiling doesn't "bounce". But about 30 years ago some bright spark thought it a good idea to fix 4 x 1 timbers under the joists then screw or nail the plaster boards to them. Result is a springy ceiling.

In a room like this which has a too-low width-height ratio, 1.14:1, standing waves are a problem, so the sprung ceiling easily resonates.

By wedging a brace across the room as pictured, most of the spring was taken out at the point where ceiling reflections take place.

The difference was night and day. Imagery greatly improved, and all boom was gone at the listening position.

The permanent solution looks like being timber beams like old fashioned oak beams. This being needed to take out the spring. If I'd wanted beams I'd have specified them! Oh well, you live and you learn (but not so builders).

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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 2017 at 12:02am
Thanks for this shared expertise and well done on fixing a frustrating situation.
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo UL, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links. and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 2017 at 6:52am
Great!!!
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Graham Slee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 2017 at 9:48am
Next stage is the construction of six BBC A11 absorbers to take the place of the rockwool packs. six absorbers require one full pack of rockwool anyway, so absorbtion should still be good.

http://downloads.bbc.co.uk/rd/pubs/reports/1992-11.pdf shows the research, absorption plots, and construction.

BBC studio A11 absorbers - bass traps

As for the celing, at present it is effectively one large panel constructed of plaster board and wooden strips, which constitutes a flimsy ribbed 3.7 x 2.7 m panel. It is attached to the rigid joists on a matrix where the wooden strips make contact with the joists, and so it can be seen to be largely unsupported.

Perhaps one runner or beam screwed through midway between joists to each strip (under the ceiling) would provide continuous support - continuous contact with the ceiling - and as such damp its resonance at the problem frequency.

The temporary brace isn't that substantial having its own springiness, and only applies upward pressure at the midpoint, indicating that maybe not much more than a basic stiffener is required.

The effect of not having the brace is that the stereo image becomes confused. Also, the problem frequencies of 125 and 250 Hz are much more evident. In reading the A11 absorber PDF, it can be seen that 250Hz "is most undesirable".

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 2017 at 12:18pm
I suspect a lot of us do suffer from room accoustic issues. This remains advanced work in progress and wonder when you reach your end solution whether this could be summarised? Perhaps the biggest issue is having a family friendly solution for those without man caves.   As outlined before I have found that the bass peaks have diminished significantly with improved cable solutions and for the most part mine have gone but sure accoustics could be improved on the question is would it get formal 'approval'
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Graham Slee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 26 Feb 2017 at 3:02am
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