[ekovalsky]

posted some pics and a diagram of my setup (featuring the RM-40/TRT) in the 8th nerve forum.  anyone with any suggestions on speaker placement and room treatment please help!

 

[Housteau]

Where is that other forum?  I am sorta new to the audio forum stuff.

My best suggestion would be to first follow the simple room treatment rules of:

1)  do not have any solid objects between your speakers to disrupt the image formation.  At least keep them lower that 2'.

2)  Have absorptive material on the wall between and behind your speakers and centered at the listening height.  An area of something like 4 x 6 should do.  I have tall walls there, so my absorptive area is taller than wider.  You will need to play with the exact size.  Too much (such as placing material directly behind speakers) may kill needed back reflection required for some speakers, such as older Infinities.

3)  The side walls between you and your speakers at the midpoint should be absorptive as well.  Once again you will need to play with the exact size and positions.  Try to be symetrical side to side though.  For example:  if you have window curtains on one side, a wall hanging on the other could help balance that out and give you what you need.  

4)  The back wall need to be refractive and diffusive.  You do not want to absorb too much here at all, but you do not want direct reflections either.  Lots of tall bookcases and record storage do the trick nicely.  If you have limited refractive areas, try to place them directly behind your listening spot up passed the listening height.  Have that area as wide as you can.  Be creative, any unusually shapped objects can help diffuse the soundwaves.

Next, I would do what has always worked for me and what I had mentioned in that other post:

.....It has been so long since I have had single cabinet speakers per channel, that I had almost forgotten how hard it was to set them up properly. This thread has reminded me of that. I have heard some home set-ups that were able to pull this off quite well, but I always had trouble and was never satisfied. Either the image, soundstage presentation , or the bass had to suffer. I could never get it all until I went with speakers that had separate bass towers to augment the upper frequency sections.

Just for fun, try moving your RM-40's into the absolute best location for image and a breathtaking presentation of space without any consideration given to the bass at all. Then, tweak in the bass the best you can by reducing the upper range frequency controls and playing with the putty removal method.

Next, beg, borrow , or steel to get loan of a VMPS subwoofer and support equipment to augment the RM-40 as a test. I have found that by placing my bass towers fairly close to my main speakers allows enough separation for both optimum bass and proper integration.

You may find that your room really likes dedicated multi-enclosure speakers per channel to give you the best of both worlds. The key is to only have them as far apart as necessary to get the optimum position for each.....

If a pair of extra subs, or even a single is out of the question for now, at least you will know what you may need to work towards.  If you find out that the sub(s) does not make a huge difference, then you may need to make that sacrifice of soundstage to balance everything out.

Dave

[JohnR]

Where is that other forum

Eighthnerve forum is here:

http://www.audiocircle.com/index.php?board=47

[Housteau]

Thank you, it was right there in front of me .

Now that I can see your room, and a nice one it is too.  I see that the photo is different than the drawing in that your equipment rack is between the speakers.  I would move that to the side as it is in the drawing, if not done already.  Then place absorptive material on that same area of the wall.  

Second, you have an open door on the left side with infinite absorption.  You need to balance that out by placing absorptive material on the opposite wall.

You may need to move your chair into the room just a bit and experiment with that ottoman being in place and removed.

As described in my other post, your rear wall needs material to break-up direct reflections.  

It is nice that you have a dedicated room to work with.

Now I am going to suggest something that may seem a bit odd.  Ok, here it goes.  Switch walls .  Thats right.  Place your speakers on either side of your sliding doors along that long wall and your favorite chair opposite.  I think you will be surprised at what you will experience.  It may not work as well with single enclosure speakers, but with your room, it is easy to switch it back again.

The open wall between the speakers is ideal to cancel out those unwanted reflections and it adds symetry to the rest of the room as well.  You should notice a wider presentation with the illusion of more space.  You will also naturally be placed more in the nearfield listening position.

This would actually be a great way to test adding in a pair of subs.

Dave

[Sedona Sky Sound]

Hello Eric,
I ran some back-of-the-envelope calculations on your room and here is what I came up with:

Low Bass Room Modes (Hz): 33, 39, 57, 69, 78, 100, 113
Reverb Time (seconds): 125 Hz = .41s, 250 Hz = .78s, 500Hz = .63s, 1kHz = .57s, 2kHz = .51s, 4kHz = .47s

So what does this mean? First, it means that you actually are starting off with a fairly dead room   . My guess is that this is totally counter-intuitive to you. You want your reverb times to be somewhere in the range of .5 to .7 seconds. The 125 Hz time of .41s means that the drywall in your room is really sucking out the low bass. This may be the reason that azryan felt your system did not have the bass volume that he was used to. The 4kHZ measurement is primarily caused by your carpet.      

So what do you do about it? Lets break this sown into 3 areas: 1st order reflections, slap echo, bass

1st order reflections: You will need a diffuser or absorber to block the first order reflections. If you use an absorber, you just have to be a little careful how much absorption you are actually doing at which frequency. With the speaker placed where you think they should be, sit in your seat and have someone walk around the sides of the room with a mirror placed against the wall. Any place you can see the reflection of the tweeter in the mirror, that is where your treatment needs to go. You should therefore have two treatment points on each side wall. Since your seat is relatively close to the back wall, treatment on the back wall behind your head will also be equally important.

Slap echo: With all the parallel painted surfaces in the room, I can only imagine how bad the slap echo is. A curtain over the glass door would be a good start but be a little careful in what material you choose. This is one case where heavy drapes would NOT be recommended. Go for a lighter, somewhat reflective material (maybe something like polyester). This curtain would probably also fix the first order reflection problem described above. If you were really ambitious, you could forget the curtain entirely and put a sliding tract on both long walls so that you could hang something like RPG Abffusers   . For the back wall, a good diffuser would be helpful. You may also want to put two small diffusers on the front wall behind the speakers. Finally, put a couple of plastic plants in the room on either side of your listening chair. These would break up the sound but absorb very little high frequency energy (which is what you want in your case).

Bass: You may have a few room modes but bass should not be that big an issue. The use of a "bass trap" would NOT be recommended. You may want a  "tube trap" tuned to frequencies of 250Hz-500Hz but I think if you use the right diffusers (something like the RPG Skyline has peak absorption at 315Hz and zero absorption at 125 Hz) this frequency range will already be taken care of. Therefore, you will want to tackle bass last. Once everything else is perfect, you can specifically measure problematic modes and build (or buy) a true helmholtz resonator to counteract specifically that frequency.  

Generally speaking, I really like Houseau's suggestions. However, my personal experience/testing is that you should leave your rack between the speakers. An open rack like yours acts as a pretty decent diffuser (good thing) and impacts imaging very little. The longer Interconnects required to get to the amp would be far more harmful to the sound than the rack. If your rack was solid (like an entertainment center) and was positioned directly between the speakers (versus a few feet behind as in the photo) then I would have to agree with Housteau 100%.

My numbers are far from perfect but they usually do a good job of defining trends and obvious weaknesses. A more detailed analysis would require someone to come to your house with detailed software to do measurements. (probably set you back about $500-$1000). My way is significantly cheaper.          

Julian
www.sedonaskysound.com

[ekovalsky]

Julian,

Thanks for the free detailed analysis!  This is exactly what I needed, since just buying random room treatment accessories may have made my sound worse and not better.

I'm checking into the RPG offerings, they look promising although I'm sure they aren't cheap.


Eric

[John Casler]

Hi Eric,

Look here.  I have the price list if it is not shown.

http://www.acousticsfirst.com/artdif.htm

http://www.acousticsfirst.com/transfusor.htm

http://www.acousticsfirst.com/products3.htm

These things are not cheap either!!!