# very small ht, problem from 200hz and down.



## panduro (Oct 3, 2009)

Hi all,

I have a very small dedicated home theater, approx L9 x W7,2 x H8,5 in foot, or metric 280x215x260cm. the gf woudnt accept that room as our livingroom so i got stuck with it. but its much loved anyways....


my system is an active setup, x-over and eq handled by 2 dbx pa+.
2 three-way fronts 1"/6,5"/12", and two 2-way rears 1"/6,5. 

down to 200hz it has an okay fr. response, but 200hz and down i cant get a resonable flat responce. 

deep nulls, standing waves and so on:crying:

i cant move speakers due to space constraints, seating is 2,5 feet from the backwall(with the door) so cant move that either.

wall and ceilling is covered in dark fabric(flame retardent and normally used for drapes), the whole floor and two feet upon the sidewalls is covered by a thick carpet.

I have one corner where it would be possible to put a corner bass trap. and room for panels one the sidewalls and ceilling.

I need as much low frequency dampening as i can possibly get without getting to much more high fr. dampening.

sorry for the random rambling and the way to long post:innocent:

What can i do?

best regards bent


----------



## bpape (Sep 14, 2006)

Ditch all the curtain material as much as possible. It's just sucking the life out of the room an leaving the bass untouched.

Can you treat the middle of the wall behind you? Can you do anything on the front wall behind the speakers? How about where the walls meet the ceiling?

Bryan


----------



## panduro (Oct 3, 2009)

Hi Bryan,


thanks for replying to my post, its much appriciated.


i know its killing the room, but its a rental and the owner wont let me paint it black, so it would mean that i would have to make and put fake walls up that i can take down again in a year when i have to move without damaging the originals walls too much. a lot of work. 

but its possible to put up some reflectors one the side/rear if the room gets way too dead.


yes i can treat the wall behind and between the speakers, but only the first two feet from the floor.


the middle of the rear wall is a door, so only it would have to be pretty "thin" in depts, 4 inches or less.

wall to ceilling is possible. 

best regards

bent


----------



## bpape (Sep 14, 2006)

Can you do a thin black cloth to get the color but minimize the high frequency absorption? Something like a muslin or broadcloth?

If the door is in the middle on the rear, then the corners back there should be available?

Straddling wall/ceiling corners will help with decay time overall though not likely in most cases have a huge impact on frequency response issues. Most of those are likely boundary related and rear wall problems.

Bryan


----------



## panduro (Oct 3, 2009)

hi again,

yes it is possible to use a thinner cloth. can you explain what muslin and broadcloth is, my english isnt that good...

left rear corner from floor to ceiling is possible, how deep will a corner trap have to be? right rear corner is occupied by a heater(floor and 3 feet up) but above is free. 

i agree with you, speakers are in the worst possible possition in each corner, so bounderies would be the biggest issue.

my decay is very short(short distance to all bounderies), so that not a big problem. but maybe it would be an idea for ceilling/rearwall. 

straddling?

again, doesnt know what that means :dontknow:

best regards

bent


----------



## bpape (Sep 14, 2006)

Decay time has nothing to do with distance to boundaries. That simply defines how much gain you get from being close and how soon in time the reflections happen. Decay time relates to how long sound keeps ringing in your room until it goes down by a certain amount.

Straddling just refers to having a panel across a corner that forms a triangular air gap behind them.

Upper rear corners are better than nothing. If the speakers are corner loaded, you'll need something in those corners too - even if it has to be flat on the front and side walls.

Muslin/broadcloth - think of a somewhat heavier bed sheet type of material.

Corner traps - as thick as you can get away with.


----------



## panduro (Oct 3, 2009)

thanks very much for your replies.

looks like i have some planning and work to do. thanks for all the advise.

i thought that sound waves lost magnitude when hitting a boundery, and therefore alot of bounderies would mean a short decay time. same reason thats it hard to get a spacious sound, to get the right mix of direct and reflective sound in a small room. because the reflective sound "build up" takes longer in a small room than in a larger room?

sorry for the maybe stupid questions..


best regards


----------



## bpape (Sep 14, 2006)

not stupid at all.

The thing is that sound does lose some intensity when bouncing but bass waves are pretty strong and persistent. That just means they're bouncing around the room more times in a given time than in a larger space - hence more chance for damage, cancellations, reinforcement, etc.

Bryan


----------



## panduro (Oct 3, 2009)

does that mean that it applies to mid and high range, but not to bass and there fore ones has to mach them by dampening the bass only?

best regards

bent


----------



## bpape (Sep 14, 2006)

Not sure what you're asking. In any room of any size, there are naturally more things that absorb as you get higher in frequency (carpet, furniture, curtains, air, etc.) that do little to nothing in the bass. So, the decay time in any room is already naturally skewed. The idea is to balance the absorption scheme to bring the decay time curve into it's proper range based on room volume, what you use the room for, how the room is built, what is in it in terms of furniture and people, etc. 

Bryan


----------



## panduro (Oct 3, 2009)

that was what i asked about.

thank you


best regards

bent


----------

