[bluemike]

I'm about to start treating my room and wanted to ask do all broadband absorbers need to be the same height
Most of them are set at 30 inches from the floor but I have one that in order to get to that height (this is a free standing absorber) I may need to hang it
from the ceiling and let it hang putting it on a stand won't work as it's too high

Opinions ?

[InfernoSTi]

I'm sure someone with some expertise will respond, but in the meantime, I've read that a bit of variation on the wall is good...it creates a bit of diffusion simply by the variation in reflection timing.  I'd go for it...perhaps you can use a small set of eyelets and adjust the height to taste?     Just use a longer than needed suspension wire/rope/cable and try it at different heights.

Have fun...

John

[Big Red Machine]

The first step is usually the first reflections using the mirror trick to stop out of phase reflections from hitting your ears before the direct stuff.

[Hipper]

I would suggest that you first listen to your system in your room as you would like it set up, that is all furniture and gear in place. It's a good idea to have carpet on the floor between your chair and the speakers in most cases.

Next, you may hear problems with bass, and these should be addressed first, so, if you can, move the speakers and listening chair about until you think the bass sounds best when in your chair.

Usually material to absorb the bass frequencies (below 300Hz say) is placed in the corners, particularly the corners of the two walls behind each speaker. Some speakers though need a solid wall behind them to give effective bass. Your speaker instructions or manufacturer should tell you this. Broad band absorbers may not help much with bass frequencies. The ideal solution is to identify specific problem frequencies and deal with them with bass traps for those frequencies. Often these frequencies are associated with the rooms dimensions.

Once you've sorted the bass try using the sound absorbers. A lot depends on what your speakers are like. You should try to find out how the higher frequencies (300Hz and above) are dispersed by the drivers - mine for example are said to come out in a 30 degree cone shape. These frequencies are reflected off walls and hard material. First reflection points are usually the ceiling and walls. My experience is that the ceilings don't cause a problem and that side wall reflections are a positive, adding to the quality of the sound. Soundwaves from your speaker that reflect off the wall behind your chair and then off the wall behind your speakers and then arrive at your ears are the most likely problem reflections as they may come late enough to muddy the sound. So absorbers are often placed on the wall behind the speakers to deal with this.

In effect, that's what I have done - see my gallery. I also use a digital equaliser. Cost is $300 plus maybe another $100 for microphone and stand. A steep learning curve awaits but I wouldn't be without it whatever gear I had.

[bluemike]

I dug up a bit more info on my speaker
The problem is i'm not sure what this means in laymans terms 


The crossover frequency is 1,700 Hz, 18 dB per octave symmetrical. At an octave higher (approx. 3,400 Hz) the on-axis response is 18 dB lower, and given that the midwoofers are becoming directional at that frequency, the in-room power response is attenuated even further.

Does this mean that having my speakers in a cove (see sketch above)
that It's posssible that the new speaker placement may overload the room
as there will be higher LF pressure ?

[bluemike]

Comments on my room sketch
Good bad or indifferent

Help is appreciated 

[Hipper]

Is that an open space behind your chair, apart from the small bit on the right? If so the only concern for reflections off the back wall is the right side - the left side just goes off into the room.

Similarly I would have thought that the absorber immediately to the left of the left speaker serves no purpose as the sound just goes off to the left. On the other hand it is probably correct to have the absorber on the right wall because a reflection from there could unbalance the sound.

I'm not sure the second absorber on the right , next to your chair, serves any purpose either. If you imagine a sound wave travelling to that point it would then be reflected into the back of the room and lost.

Of course the way to test that is to remove it and listen.

The way I see things, if you are trying to control bass, absorbers should be somewhere behind the speakers, perhaps on the diagonal bits of the wall (I've no experience of diagonal walls so I may be wrong!). For controlling the higher frequencies - above 300Hz - they should be placed to deal with reflections. If there are no reflections (such as where there is no wall to reflect off) there's little point in having absorbers there.

In your shoes, what I would do, as an experiment, is to keep that absorber nearest the right speaker and the one on the wall behind the speakers in place, as well as those bits on that wall behind the right of your seat. The rest I'd place somewhere behind the speakers. Then I'd listen.

The height of these absorbers, if used for the higher frequencies, is your ear height.

I don't understand what that information about your speakers means. Frequencies above 300Hz or so reflect so what they mean by 3,400Hz (3.4KHz) becoming directional I don't know. What speakers are they?

[Hipper]

Just a thought. Another experiment you could do is to remove the right and left absorbers, nearest each speaker, and replace the left one with material similar to your right wall - something that reflects sound in a similar way.

This might add reflections to both sides, and as I said earlier, I now think these reflections off the side walls are a positive that liven up the sound.

[bpape]

Given that setup, you will have a lot more boundary loading on the right side than the left as well as a completely different set of arrival times/intensities for your early reflections. 

The treatments don't have to all be  at the same height by any means though purely from a reflection zone standpoint, they'll likely be.

With that much of a drastic difference in off axis power response that low in frequency, you'll definitely need to absorb the reflections as they'll not only be skewed from the direct and from each other in time - but they'll have a significantly different spectral balance  than the direct signal.

Bryan

[bluemike]

OH boy me thinks I need a room shrink 


Attached is a pic of the room with the treatments in place


Uploaded with ImageShack.us

[bluemike]

Given that setup, you will have a lot more boundary loading on the right side than the left as well as a completely different set of arrival times/intensities for your early reflections. 

The treatments don't have to all be  at the same height by any means though purely from a reflection zone standpoint, they'll likely be.

With that much of a drastic difference in off axis power response that low in frequency, you'll definitely need to absorb the reflections as they'll not only be skewed from the direct and from each other in time - but they'll have a significantly different spectral balance  than the direct signal.

Bryan

Bryan any suggestions on how to improve this ?

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[bpape]

Pull the speakers farther out so they're not in the 'nook'.  Make sure to have a thick panel directly to the side of the right hand speaker to address those boundary interactions that are not going to be present on the other side.  I'd also do something on the 'front' wall that's to the left of the left speaker since that will also be a different boundary that the other one doesn't have.

Bryan

[bluemike]

.  I'd also do something on the 'front' wall that's to the left of the left speaker since that will also be a different boundary that the other one doesn't have.

Bryan

put absorption there as well should it be as thick as the right one

[Red Dragon Audio]

Hey Mike what do you think about trying the system rotated to the left like this?
It would allow a little more flexibility with lateral speaker placement.
However it does introduce a new issue with having a wall close behind the listening position.

[bluemike]

Thanks

[bpape]

put absorption there as well should it be as thick as the right one

Probably.  Yes.

Bryan

[bpape]

Bryan
Within my current listening configuration
Where should the tritraps be placed for best results

Thanks
Pat

Having things all in that alcove the Tri Traps mostly will be in corners away from the speakers or seating and be primarily for decay time. Thinking front far left and the rear corners.  Another option is to use them along the wall/floor boundary by the speakers. Easy enough to try both ways since no mounting required.

Bryan

[bluemike]

Thanks again

[bluemike]

Well after a few weeks of playing with the system
As per Bryan P suggestions here
 
things are looking up
I thought that by removing the speakers from the cove the sound would deteoriate
Im really scratching my head now what sounds good on paper vs listening