standing wave?

BoB_DoLe · Post by **BoB_DoLe** » Wed Jul 05, 2006 4:11 am

David French wrote:The smaller your room, the more severe you must be with your bass absorption, so this is definitely not overkill.

yeah, i know that (and hear it

), i meant it just as "do the large chunks take too much space in my little room" not like "is that too much absorption", i hope you know what i mean.

You will, however want to use chunks in other areas besides the floor to ceiling corners. You will also need to do something with the area where the ceiling joins the walls. This will help tame the resonances that exist between the floor and the ceiling. Chunks are always good, but you should be able to get away with 4" thick panels if you want to go that route.

wait, lets step back! i thought we were talking about the ceiling to wall joints all the time? you know, im german and have sometimes problems with understanding such 'technical' things or such, thats why i ask instead of reading old topics (even though im sure this problem was discussed already..)

im now in this chunks-thing, seems easy to me and affordable in my situation. so to conclude, i will make 4" thick chucks, about 20 of them, and put them in the corner from wall to ceiling, both sides of the room (of course..), and covered with fabric.
right so far?

thanks again!

David French · Post by **David French** » Wed Jul 05, 2006 4:59 am

I just looked over the whole thread again. I think that chunks will not be necessary. from looking at your SketchUp model, it appears you already have chunks where the walls meet. Panels are extremely effective in such a high range as 140 Hz. I think chunks are not necessary and you should simply use 4" thick 2' x 4' panels, as many as you can fit (probably four) placed at 45 degrees across the intersections where your side walls join with the ceiling.

Sorry fo r the confusion. I had it in my head that the room was not treated, but now I believe that it is. Are we in agreement now?

BoB_DoLe · Post by **BoB_DoLe** » Wed Jul 05, 2006 7:45 am

ok, now i got it

yeah, the other corners are already treatened, like the corner traps here, but more filled with insulation..
then i go for the panels, even better if it works

so response from me on sunday or so!

David French · Post by **David French** » Wed Jul 05, 2006 8:30 am

Cool. The panels really should solve this.

BoB_DoLe · Post by **BoB_DoLe** » Sat Jul 08, 2006 2:30 am

ok what should i say im a bit disappointed right now..
we built the panels today and in the first ear-test i noticed little change

im gonna make new tests today (or perhaps tomorrow) but i think its about the same as last time.
so what could be the problem?
thanks

David French · Post by **David French** » Sat Jul 08, 2006 4:03 am

That's surprising. Can you tell me exactly what you added and where? I was very sure that this was a height dimension resonance. Have you tried a differen set of speakers?

BoB_DoLe · Post by **BoB_DoLe** » Sat Jul 08, 2006 4:13 am

it was only first testing though, but.. well like i said its little difference sadly..

we build frames about 80" by 24", covered with fabric, and put the insulation behind it (two layers of 4" glaswool - the one i told you), then we put the frames in the corners right and left from the listening position, so that its about 40" behind and 40" in front of my chair.
thats about it.
im also really shure its a height reso, based on the facts i said in the opening post about varying my position..
no different speakers yet, will try that tomorrow perhaps.. but as far as that i know these speakers, i own them about 2 1/2 years by now.

im going to test more right now.

David French · Post by **David French** » Sat Jul 08, 2006 4:33 am

The absorbers you made should be very effective.

You dont happe to have a small diaphragm omni, do you? If so, I could help you do some room measurement and we could quickly get to the bottom of this.

BoB_DoLe · Post by **BoB_DoLe** » Sat Jul 08, 2006 5:01 am

David French wrote:The absorbers you made should be very effective.

thats what i thought, yeah, and they look as they would

You dont happe to have a small diaphragm omni, do you? If so, I could help you do some room measurement and we could quickly get to the bottom of this.

nope, all i can give you is a large diaphragm omni or a dynamic cardiodid (ok forget the last one

).
but i measured with my b2 and came up with this.
looks like the 140-peak got a little bit less, but now theres one at 300hz and about 500hz

i really dont understand THAT!

David French · Post by **David French** » Sat Jul 08, 2006 7:01 am

I wouldn't trust those measurements. If you really want to get to the bottom of this, pick up a cheap Nady CM-100 or an equally cheap Behringer ECM8000.

BoB_DoLe · Post by **BoB_DoLe** » Sat Jul 08, 2006 7:14 am

David French wrote:I wouldn't trust those measurements. If you really want to get to the bottom of this, pick up a cheap Nady CM-100 or an equally cheap Behringer ECM8000.

yeah im gonna do that, but this takes a few days..
and ive only measured for comparison now.
hmm any ideas about this behaviour?
or should i wait until new measurments?
what i forgot to say, my inner walls arent actually the original walls, just drywall (1/2" thick) on woodframing. but i stuffed a lot of glasswool behind it.(up to the ceiling of course!)
could this be the problem that the drywall is perhaps acoustically transparent for those frequencies or am i talking bullshit? thats just what came in my mind at first..
thanks anyways!

David French · Post by **David French** » Sat Jul 08, 2006 7:21 am

Glad to hear you're going to pick up a measurement mic. Let's wait for that. I'd like you to run a test tone that I will provide though your system so I can analyze the data myself on familiar software. I could be more helpful that way.

BoB_DoLe · Post by **BoB_DoLe** » Sat Jul 08, 2006 7:33 am

ok that sounds good to me!
i just ordered the behringer (no nady available in germany, huh?), but i dont expect it to be here before tuesday. but i think until then i can get up another speakerset for comparison, and perhaps get my couch (ok i just wanted to say that

).

David French · Post by **David French** » Sat Jul 08, 2006 7:40 am

Cool, looking forward to it.

BoB_DoLe · Post by **BoB_DoLe** » Wed Jul 12, 2006 6:16 am

cheers
our postal service is so damn slow, you wont believe it

well, i expect the mic to be here by tomorrow.. as far as im busy the whole day, i will get to make the measurements in the evening or perhaps on thursday.
but you could send me your test files, so i have them when its getting interesting