#1888509 - 02/09/08 07:33 PM
ethan - ceiling pitch:symmetry / bedsheets:703 /
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promesis
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Registered: 02/09/08
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hi Ethan (et al)... i have been pouring over the huge amount of helpful materials you have authored (*as well those of other folks here at this forum .. thanks for directing me here earlier today).
thank you so much for your contributions.. if i may, i would like to impose a couple of questions for answers or discussion.
i am moving into a new small control room .. i don't have the exact measurements but it is approx. 10-11' wide and 14-15' long (referred to as left and right in example).
1.
maintaining ROOM SYMMETRY :
the ceiling in the room pitches from the left to right walls - the height is about 9' and slopes down to the right wall at about 6' and maintains this 3' pitch the length of the room.
should i set up against a short wall respecting the optimum room orientation forgoing symmetry; or is symmetry the limiting factor in this particular environment?
my instinct was to maintain symmetry (being a rather unlearned type dude in these matters) so that is how i have started to set up; with monitors positioned along the right wall with sound facing the tallest left (now "back" wall) emanating out as the ceiling slopes up.
Could you explain the consequences of either for compare and contrast?
and finally ..
2.
the modal properties of the room are apparent.. listening to very familiar program material i can hear some of the bass freq peaks and nulls, parts disappearing etc.
i need some bass trapping - can i just cover some OC703 and OC705 with bed linens? i realize they aren't that acoustically transparent - but wouldn't the low freqs still be absorbed.. i am not worried about the mid/hi freq level or the reflection of these freqs off the bed linens (or could that be a problem - i figure those freqs are the easiest to control if the room is "too live" .. another instinct thing, your FAQ seemed to confirm this as well as good ol' experience .. plenty of old carpeted band rooms LOL!!)
i need to be sure that the lows will not be affected by this choice of covering materials. i would like to get a bunch of rigid fiberglass and simply sew them up in bed sheets and place them appropriately. (* i have, since authoring my original email, discovered on this board the use of inexpensive muslin fabric - this seems a viable option, however, my original curiosity remains).
Could you explain the consequences or effects to lo freq bass control utilizing bed sheets as coverings in general or consistent with my aforementioned listening environment should that be a factor?
2a.
just a side bar question - 703 or 705 for the ultra low end absorption? according to your FAQ - the more dense 705 is more affective at absorbing lower frequencies than 703.. but in some other area or somewhere else altogether (kinda saturated with bass trappingotosis ) indicated if making 4" or thicker traps to use 703. i am confused - does the 705's density begin to reflect instead of absorb at a particular thickness i believe your FAQ indicates that this is a possible consequence?
what about two 705's sandwiched by two 703's? have you/anyone tried these schemes of mixing different densities of rigid fiberglass .. or am i getting too silly and just freaking fill the room with both 703 and 705 everywhere and simply learn to deal with the fact that "i am now aware" that my room - and most everyone else's really sounds like poop and there is really not much you can do at these tolerances except just that?
thanks so much folks - any direction or advice is much much appreciated!
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#1888650 - 02/10/08 07:03 AM
Re: ethan - ceiling pitch:symmetry / bedsheets:703 /
[Re: promesis]
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Ethan Winer
MP Hall of Fame Member
Registered: 06/12/00
Posts: 5300
Loc: New Milford, CT, USA
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the height is about 9' and slopes down to the right wall at about 6' and maintains this 3' pitch the length of the room.
There is no right answer here, but if it were me I'd have the speakers fire the longer way down the room, and use absorption on the ceiling to "force" symmetry.
Could you explain the consequences of either for compare and contrast?
Bad bass response that's not fixable, versus symmetry that's mostly correctable with absorption. 
can i just cover some OC703 and OC705 with bed linens?
Sure.
i realize they aren't that acoustically transparent - but wouldn't the low freqs still be absorbed.
Yes, exactly.
Could you explain the consequences or effects to lo freq bass control utilizing bed sheets as coverings
At worst there will be no difference and at best you might even get a little benefit (possibly more bass absorption) from the bed sheets.
703 or 705 for the ultra low end absorption?
Either will do a fine job. As the material is made thicker, using a higher density is less important. One of these days I hope to do my Density Report tests again with twice as many panels, to get more compelling data. But if cost is a concern, which it usually is for DIY types, 703 does a fine job for half the cost of 705.
--Ethan
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#1888734 - 02/10/08 11:21 AM
Re: ethan - ceiling pitch:symmetry / bedsheets:703 /
[Re: Ethan Winer]
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promesis
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Registered: 02/09/08
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thanks for your replies ethan.
Bad bass response that's not fixable, versus symmetry that's mostly correctable with absorption.
that's a pretty bleak prognosis. i will re-orient the room and ruminate about what the apparent (if any) differences are. I have a dBX RTA reference mic used for calibration purposes with my JBL LSR series monitors (of course any "calibrating", so-called, that the circuitry does in those speakers, is simply reacting to the poor bass response of the room) .. do you think i could use this mic with Room EQ Wizard (i am a mac dude - i know RPlusD.. but 0Plus0 = $0) to identify changes with science as opposed to "interpreting" the changes. This way i can hopefully accomplish what i see a lot of folks here wishing to do; to treat their rooms and document the changes affected by their efforts.
on the subject of "forcing symmetry", how so? i assume that because regardless of the room's inherent properties or listening orientation, treating the bass freq with bass traps appropriately i.e. in all corners, observing rules established, et cetera, is a constant - simply, regardless of "whatever", the bass will be treated exactly the same .. so, the hi and mid freq control would be the key to "forcing symmetry" right? if so, could this be done be treating the ceiling the same with maybe packing blankets across the width of the ceiling down to where the right wall meets it - then down the left wall to a level equal to that of the right side. essentially creating a symmetrical l/r "hard wall surface area" along the length of the room - with a sort of 30° 60° 90° triangle tent or pocket of hi/mid freq absorbing material upon the ceiling and partially down the left wall - where the intended effect would be of those freqs "poofing out into space" but the sound remaining underneath would be subject to this "symmetrical tunnel" .. where of course, those walls would subsequently be treated at the appropriate first reflection points - thus treating the area as the classic rectangular room with flat ceiling?
jeesh .. hope that makes sense, i write much like i speak; the king of run-on sentences and unique punctuations..
Thanks again Ethan.
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#1889375 - 02/11/08 10:12 AM
Re: ethan - ceiling pitch:symmetry / bedsheets:703 /
[Re: promesis]
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Ethan Winer
MP Hall of Fame Member
Registered: 06/12/00
Posts: 5300
Loc: New Milford, CT, USA
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that's a pretty bleak prognosis.
Not at all! Set up lengthwise, then use absorption on the ceiling. But not packing blankets - please!
I have a dBX RTA reference mic
I'm sure that's fine for bass frequencies, and maybe mid/high frequencies too.
the bass will be treated exactly the same .. so, the hi and mid freq control would be the key to "forcing symmetry" right?
Exactly.
jeesh .. hope that makes sense, i write much like i speak; the king of run-on sentences and unique punctuations..
You need to work on that.
Seriously, I work best with specific questions, versus long descriptions followed by "whaddya think?"
--Ethan
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