Hi Amp_Nut,
yep, you are getting deeper and deeper into that theme
Regrading the listening chair, if that leather chairs you are looking for has a back- or headrest not that wide (my was about one meter) then it should not be a big problem. But for sure the sofa seat is a better choice for that purposes, even if not that comfortable
The bass traps; that what you have mentioned with a kind of plywood taking energy (resonator) is a more complex story and is used for
certain frequencies. That requires a measurment of your room to find out which low frequencies creating problems / an overload and the bass traps has to be build exactly for that frequencies. Some shops offering traps of that kind for a certain range of low frequencies. Should your room has no "problems" exactly in that range bass holes might be the result.
To build in general a mix of resonator and absorber in my eyes is too "risky" as you could take away wave/bass energy where is it not necessary.
Just try the following:
A step which would improve bass modes and
which should be done first before you are thinking about bass trapes is the positioning of the speakers. Experiences (not only mine) shows that putting speakers approx. 1/5 of the room lenght from the rear wall and the listening position approx. 2/5of the room lenght (I know that your position is about 2,5 feet from the wall / door but try just to see) will eliminate modes very effectively. The distances might differ -> i.e. 1/6 : 2/6, you have to play around. That should improve already modes (provided you have some which are really disturbing the overall sound).
Now, to give it a try whether and how your rooms profits from bass absorbers: Just put all kind of soft stuff you have like pillows, covers, jackets etc. into the room corners behind the speakers (try to create a little tower at least of a meter hight) and test the result. Preferably with music containing low frequencies. While music is playing, walk through the room and listen where you can locate an overload of bass and where you have the feeling that almost no bass is existing. Place on that place(s) where you have an overload also some material and check again.
A great help to locate bass modes (overloads) is a dB measuring device and a CD with low frequencies (i.e. in 5 Hz steps - from 30 to 120 Hz or so). Place that measuring device where your listening position is and play that CD. Make notes showing the frequency and the measured loudness (dB). Put that values into an spreadsheet and create a curve. Done this you can see which frequency, based on the present position of speakers and listening position, creates an overload and which falls into a hole. A
theoretical optimum would be having a straight curve (to be honest, not everybody like it). Of course your speakers playing as well a big role here, depends how they are "sounded". A lot speaker having a higher mid tone and high bass level in order to sound more voluminous. If yours are sounded likewise and you like that sounding then of course this must be considered.
How I would proceed now: position your speakers as above and try to have a distance between the speakers and listening position less, respectively not greater than 3m -> this will reduce early reflections. Check regrading bass modes and maybe play around with the speakers and listening position until satisfaction. Now put all soft stuff you can find in the corners behind the speakers.
After that place wall panels behind the listening position and on the sidewalls. An easy method to find out where to put panels on the sidewalls: sit in your chair and let somebody (your friend or wife...) walk with a mirror along the sidewalls. Where you can see the speakers in the mirrow, put the panels there, if possible. Best is to have absorber mounted at the same hight as the high- and mid tone chassis.
Certainly it will improve already a lot. And now think about bass traps. Maybe just ordinary absorber / corner blocks or similar are sufficient already. If not we can go further realizing resonators you need.
Some of your questions should be answered. The remaing questions:
"
...As a continuition of the same thought.... would the 4 wall sound absorbant panels / boxes that you have made ( each each 100cm x 100cm x 5cm ) be more effective if you gave a sheet of thick paper behind and immediately touching the rear of the sound proof material ?"
No, as they have been built to absorb high- and mid frequencies only, reducing reflections. They are not for low frequencies. Wall panels of this kind aborbing low frequencies must be much thicker ~ 50cm or so, depends...
"
Ditto, to wrap a thin Plywood or thick paper along with a mattress as a bass trap ?"
I would not without calculating what low frequencies must be reduced respectively taking off energy.
"
3.The 4 Panels that you have made, each of each 100cm x 100cm x 5cm... you have given a clearence of 20 Cms from the wall ( refered to the outside surface of the panel (?)."
Exactly. The frame's side having a deepth of 20cm. But I have
two panels (each 5cm thick) in each frame and thus remaining a 10cm gap between panels and wall. Maybe I've missed mentioning it before...
Your intention having 5cm thick panels with 5cm gap is fine but better having 10cm gap (mineral- or cotton wool works more effective with a bigger gap). It should be sufficient, if not, just try with 10cm thick panels and 20cm gap.
As I have no idea about your room, above measures can be put on a minimum provided your room has normal interiors like a carpet, some sofas, curtains etc. If your floor, i.e. consiting of stone or wood/planks a carpet, in front of the speakers, would already help, not that much but some echoes/reflections would be eliminated.
Well, so far... hope some is of help. However, have fun realizing your set-up.
See ya later on this link.
Brgds
nuRoXX
edits:
A web-site with frequencies (mp3, convert to wav if required) for download (in german language).
www.hifiaktiv.at/diverses/testfrequenzen.htm
(web site and contents exclusively by David Messinger)
Depends on the frequency range of your speakers what frequencies you need but would start downloading 40 Hz and above until 200 Hz or so.
Another link detailing acoustic in small rooms for HT but of course applicable for stereo set-ups (englisch)
http://www.bilderspiele.com/de/heimkino/smallrooms.pdf
This link is showing what is meant with the 1/5 : 2/5 positioning of speakers (red dots) and the (black) listening position
http://members.chello.at/gamuerle/BlueDanube/Lautsprecher-Aufstellung2.gif
And some very basic (but useful) stuff about setting up loudspeakers
http://www.audiophysic.de/aufstellung/index_e.html
http://www.audiophysic.de/aufstellung/regeln_e.html
http://www.audiophysic.de/aufstellung/beispiel_e.html
A link for calculating resonators (Helmholtz)
http://82.95.237.142/mhsoft/Helmholtzabsorber.asp
A link for calculating diffusor (skyline diffusor)
http://82.95.237.142/mhsoft/DiffusorCalculator.html
And finally a link describing the whole story about rooms and acoustic
http://www.customaudiodesigns.co.uk/help.htm
