[jimbones]

Hi, I have a drop ceiling in my basement with a T Grid setup. I have a mix of T Fusors and GIK diffusors as well as the Armstrong 2x2 ceiling tile. I am beginning to suspect that this hurts the bass performance as there is probably small vibration over a large area muddying the bass. I have Roxul between the floor joists just above this ceiling. Any recommendations? Do I need to do anything? leave it?
 

[MaxCast]

I doubt the diffusers are doing much for the bass.  They are doing what they should for the mids on up.
To dampen bass you need thick absorption preferably in the corners of your room.

[jimbones]

I doubt the diffusers are doing much for the bass.  They are doing what they should for the mids on up.
To dampen bass you need thick absorption preferably in the corners of your room.

Yeah I was only trying to let you know what is currently on my ceiling, the diffusors are for the high end only. What about an open wood frame with fabric stretched over it? The 4 inch batting is already in the joists? or just leave open. As far as locations where I want to have panels they need more mass?

[MaxCast]

What about an open wood frame with fabric stretched over it?

If you can get away with that the easiest thing to do is to cut triangles out of 2'x4' ridged fiberglass and stack in the corners covered by your frame and fabric. If you search this circle you are bound to find pictures of various bass traps.

[jriggy]

Correct me if Im wrong but I dont think rolled batting is dense enough for bass traps... If memory serves, member Kshep (?) did a bass trap making thread with pics a couple years ago...

[AKLegal]

Correct me if Im wrong but I dont think rolled batting is dense enough for bass traps... If memory serves, member Kshep (?) did a bass trap making thread with pics a couple years ago...

You can use rolled batting as a bass trap provided that the trap is thick enough, say at least 10 inches thick. 

I used this calculator to build some very effective bass traps for my room.  http://www.stanleyhallstudios.co.uk/pacalc/

Heres a comparison between 10 inches of pink fluffy insulation vs 10 inches of owens corning 703 and 2 inches of owens corning 703.
graph 1


The general rule is the thinner the trap the more dense it has to be.  So if you have the space for thicker traps you can save alot of money using standard insulation.  From the graph you can see that 10 inches of 703 is very effective at low frequencies but it would get expensive.  The great thing about this calculator is that you can try out different combos to get the price performance that you want.  I ultimately went with a combo of 2 inches of OC703 in front of 10 inches of pink stuff for my corners. 

graph 2

[jimbones]

If you can get away with that the easiest thing to do is to cut triangles out of 2'x4' ridged fiberglass and stack in the corners covered by your frame and fabric. If you search this circle you are bound to find pictures of various bass traps.

I will make corner traps using batts about 16 inches thick. But does that mean I can leave the ceiling tile alone?

[AKLegal]

I will make corner traps using batts about 16 inches thick. But does that mean I can leave the ceiling tile alone?

There are a couple of things you can do with the ceiling.  The consensus minimum thing that experts on sites like GearSlutz think you should do is roll out R-30 insulation on top of each ceiling tile.   You could also replace the ceiling tiles with acoustic ones like these.  I made 10 of these before and you really can't make them for less than what ATS is selling them for.  You could do the whole ceiling or just around the wall perimeter and first reflection points.

You might want to finish your corner traps and see how well they work first before thinking about the ceiling.  After I finished my traps I found that the ceiling wasn't as big of an issue as I thought and only needed minor work as opposed to the massive amount of money I thought I was going to have to spend.   

[dm]

Yeah I was only trying to let you know what is currently on my ceiling, the diffusors are for the high end only. What about an open wood frame with fabric stretched over it? The 4 inch batting is already in the joists? or just leave open. As far as locations where I want to have panels they need more mass?

This is exactly what I did.  stuffed fluffy insulation in the joists all around my basement ceiling and then built a picture frame rectangle and stretched fabric over it for the suspended panels that were located in the corners of the room.

[AKLegal]

Yeah I was only trying to let you know what is currently on my ceiling, the diffusors are for the high end only. What about an open wood frame with fabric stretched over it? The 4 inch batting is already in the joists? or just leave open. As far as locations where I want to have panels they need more mass?

4 inches of batt really isn't enough to affect bass and will lead to uneven absorption (dead room\bass heavy sound).  You want more broadband absorption.  Maybe open frames with 5-7 inches on top in addition to the 4 inches between the joists.  That will give you 9 to 11 inches of absorption which won't deaden the room as much since more bass will be absorbed.

The open frames would eliminate early ceiling reflections though.

[jimbones]

OK I think I have some good ideas here but one more question. I placed the batting over maybe 90% of the floor/ceiling joists area. Do I really need that coverage. I am thinking remove batting from the center of the room where i have diffusors and moving it to make the batting 10 inches thick around the perimeter and corner to be more effective.

[AKLegal]

That's a good idea, treat the perimeter of the room and put bass traps in all corners.  Personally I think you will be pleasantly surprised with the bass quality you will get once you finish your corner traps.  You will get a larger range of acceptable speaker positions.  You are on the right track and you won't regret putting in the time and effort.

[jimbones]

Thanks for the advice. I'll start with that and post my results.

[Alex Reynolds]

BTW - your earlier idea of making an empty frame with fabric so that sound passes through to the insulation is a good idea to get more high frequency absorption, but I don't think you'll get too much of an added affect on bass as it will pass through the ceiling tiles, diffusors, etc pretty easily already.

[rollo]

Hi, I have a drop ceiling in my basement with a T Grid setup. I have a mix of T Fusors and GIK diffusors as well as the Armstrong 2x2 ceiling tile. I am beginning to suspect that this hurts the bass performance as there is probably small vibration over a large area muddying the bass. I have Roxul between the floor joists just above this ceiling. Any recommendations? Do I need to do anything? leave it?

  Jim what makes you think it is the clg. tiles ? Did your previous subs boom ? Could it just be the location of the subs ? if you can get a spectrum analyzer and measure your room just maybe it is the position or just your room.
   A good solution is to have a lively [ reflective [ floor and absorptive clg. or visa versa.


charles

[jimbones]

  Jim what makes you think it is the clg. tiles ? Did your previous subs boom ? Could it just be the location of the subs ? if you can get a spectrum analyzer and measure your room just maybe it is the position or just your room.
   A good solution is to have a lively [ reflective [ floor and absorptive clg. or visa versa.


charles

No the previous ones didn't because I had 2 so I think having multiple helped but then I got to thinking after noticing my ceiling tiles were vibrating that can't be good.  my floor is absorptive and I have auralex TFusors on the ceiling in some spots.

[jimbones]

  Jim what makes you think it is the clg. tiles ? Did your previous subs boom ? Could it just be the location of the subs ? if you can get a spectrum analyzer and measure your room just maybe it is the position or just your room.
   A good solution is to have a lively [ reflective [ floor and absorptive clg. or visa versa.


charles

BTW forgot to mention I do have measuring equipment now so I just have to figure out what feature to use.

[dm]

BTW - your earlier idea of making an empty frame with fabric so that sound passes through to the insulation is a good idea to get more high frequency absorption, but I don't think you'll get too much of an added affect on bass as it will pass through the ceiling tiles, diffusors, etc pretty easily already.

You are probably correct for the really low frequencies.  However the fabric corner has the added effect of eliminating horn loading of mid/higher frequency sound in the tricorner area of the ceiling.

[jimbones]

just curious, if I find a deal on corner traps I may buy them but I need to know one thing, are the foam traps as good as the fiberglass traps? Auralex makes corner traps (a 8 pack for a bit over 3 bills) If NG I'll stick with fiberglass.

[cheap-Jack]

Hi.

Hi, I have a drop ceiling in my basement with a T Grid setup. I have a mix of T Fusors and GIK diffusors as well as the Armstrong 2x2 ceiling tile. I am beginning to suspect that this hurts the bass performance as there is probably small vibration over a large area muddying the bass. I have Roxul between the floor joists just above this ceiling. Any recommendations? Do I need to do anything? leave it?

First off, I'd NOT use mineral fibre ceiling tiles like Armstrong. Instead, I have installed for 30 years now with great success, standard 2'x4' fibreglass ceiling tiles (cheapie stuff from any hardware stores) on T grid suspenders for my basement audio den. With only 7 feet ceiling-floor clearance!!!!! Fibreglass panel absorbs sound much much better than mineral wood & are easily removable & replaceable.

GIK diffuser panels are designed for diffusing 350Hz up to 7KHz, which should do nothing for yr bass performance.

I suspect the shape of yr basement audio room & layout of yr loudspeakers screw up the bass.
Why don't you show us the floor plan & the audio layout.

Considering my audio den low low 7 feet ceiling height, with synthetic fibre wall-to-wall carpet on rubber underlay, no nothing bass corner traps nor diffuser panels the likes acoustic control added. Yet the
pipe organ bass notes (down to 20Hz) pumped out from my 100W 10" sub clean, fast & powerful, with signal fed from my stereo tube phono-preamps playing digitally mastered vinyls.

FYI, my sub is placed just off the right corner of the front wall, about 5 ft behind my right channal KEF bookshelvers. Repeat - no conrer bass traps needed at all.

c-J