room treatment, where do you start?

I just finished treating my room. I DIY'd it and worked experimentaly and intuitively.
I started with "glare" high frequencies, early reflections. I built 5 1" Fiberglas panels,(fabric covered with speaker cloth). That was a big improvement and encouraged the fabricating of 5 broadband absorbers mounted 3'' away from the wall and Placed around the room (moved many times) until it cleared things up in the mid range and upper bass regions. That encouraged the need to address my old Nemesis, lot's of confusion in deep bass, especially noticeable when driving my system with greater attenuation.

I constructed 2 air-tight 5"deep panels, Fiberglas damped and faced with 1/4" resonating plywood sheet and one with 1/8th" ply to control sightly higher bass frequencies...

I also found it necessary to construct 4 dampers for the wall ceiling interface in areas where I could hear and feel that woolly bass rumble and excessive vibration. For these I used 12" dia Fiberglas pipe wrap 1/2 sections with end caps and pegboard backing (Helmholtz)and of course full front and back fabric covering.

A lot of work to be sure, but the results are stunning.
I had pretty well tweaked myself out. I had addressed hundreds of little things over the many years but I never quite had the clarity of mind to attempt the (the final frontier) the room itself.

I can now drive the heck out my system without negative room interaction, I can hear every bass note clearly, and finally.... a piano sounds like a piano..to say nothing of a massive improvement in staging,specificity, depth, width etc

The research I carried out was all in the Audiogon forums.
I just kept reading stuff and making notes and piecing things together in my mind until I had a kind of map in my head, so I just did it.

Well worth the trouble. My system sounds exciting to me again. I would recommend putting thought and energy into room treatment to anybody.

Check out my room in Virtual systems under Bigby. I used mostly RPG BAD ARC panels and Real Traps Mondo traps. It changed the sound drastically. If you use the panels, you can take them with you when you move.

Most important is to trap the base in the corners and treat the first reflection points. From there you can go as crazy as you want.

Room treatments – where to start?

You ask great questions, many I’ve wrestled with myself. The approach I took was to
(1) Educate myself about small room acoustics.
(2) Measure the room before you do anything to establish a baseline to determine if and where problems exist and to compare against the addition of treatments and placement options.
(3) Create frequency range (i.e. low VS middle/high frequencies) dependant strategies for dealing with offending modes
(4) Determine if buying and/or building (DIY) treatments is best for you, after considering using regular household items like furniture, carpets, bookcases etc.

Education - Educating yourself will be an investment that will (i) save you money by buying or making (i.e. DIY) the ‘right’ products, (ii) save you time from conducting infinite trial and error placement options of the treatments, and (iii) allow you to critically evaluate products offered by manufacturers, most of whom exagerate their product’s performance specs for marketing purposes. I’d highly recommend you read Floyd Toole’s latest book http://www.amazon.com/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_1?s=books&ie=UTF8&qid=1284840260&sr=1-1 and also Alton Everest’s book http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071603328/ref=pd_sim_b_1. Harman has many good White Papers found here: http://www.harman.com/EN-US/OurCompany/Technologyleadership/Pages/WhitePapers.aspx?CategoryID=White papers

Tools – at the very least get a SPL meter which Radio Shack sells and download test tones from RealTraps to help with analyzing bass frequency modal peaks and nulls. You will also need to calculate your room’s modes or standing waves so this tool will do the job: http://www.harman.com/EN-US/OurCompany/Technologyleadership/Pages/Calculators.aspx?CategoryID=Calculators. You will also benefit from using a frequency wavelength chart for calculating 25% and 50% wavelength distances for absorption placement and diffusion depth respectively. I like this one: http://www.soundoctor.com/freq.htm Like anything, if you can’t measure it then you can’t manage it.

Strategy – Having a game plan is important and will help to determine what kind of treatment goes where and in which sequence things should be addressed. It’s likely a good idea to establish a ‘baseline’ to determine if you have acoustical problems, and from which to compare the addition of treatments and placements thereof. Deal with the offending reflections and leave the others alone. I use an Excel spreadsheet to record the SPL for a broad range of frequencies before any room treatments which became my baseline. Use the same Excel sheet to record the SPLs again for each subsequent ‘Test’ of adding treatments or different placement combinations to note the difference from your baseline.

Frequency-dependant treatments: generally speaking, you should treat the low and mid/high frequency regions separately; use about 300Hz as the transition zone frequency to differentiate the treatment strategies. Bass frequencies ( 300Hz).

Personally, I chose to tackle the bass region first because modal peaks in this region can reach 20dB which drowns out the mid and high frequencies, so clearing up the bass should also introduce more perceived clarity into the upper frequencies too.
• 20Hz to +-50Hz -> use EQ to tame these very low peaks.
• 50Hz to +-100Hz -> use Helmholtz or Diaphragmatic type bass traps for this next lowest region. Placement effectiveness for diaphragmatic bass traps is where air particle pressure is maximized which is at the wall, so these traps are hung right on the wall with no air gap behind them.
• 100Hz – 300Hz -> use resistive type bass traps (e.g. Fiberglass filled) for this bass region. Placement effectiveness is maximized when air particle velocity is maximized which is at the 25% wavelength mark, so from 34” to 11.5” out from the wall for 100Hz and 300Hz respectively. A one or two inch air space won’t cut it – try 7” to 11” air space instead and extend the fiberglass bass trap as far into the room as you can (34” to get to 100Hz). 34” less 11” equals a bass trap of 23” thickness, so buying 2”, 4” or even 6” thick traps won’t likely work well, unless you layer them to extend the total thickness.

If you can swing it, put bass traps in all four room corners from floor to ceiling, and at the mid point of your front or back wall in the floor/wall corner.
For the mid/high frequencies, you can start off using normal possessions like furniture, bookcases etc, but you will need to know where things should go and if they should be diffusive or absorptive in nature.

Of the 6 room surfaces, what should you tackle in which sequence? Here’s one approach:
(1) Since first reflection points are the strongest reflections, deal with the floor and ceiling ones first via absorption and diffusion respectively. Research indicates that lateral side wall first reflections add positive contributions to your room’s sonics by widing the apparent sound stage and creating listener envelopment.
(2) Try adding diffusion to the back wall to keep the energy in the room but attenuate the direct reflections back to the listening position
(3) The front wall can be either absorption or diffusion based on personal taste and type of speakers
Another strategy worth considering is Buy VS Build. Do you want to buy finished products and pay top dollar (as used acoustical treatments are seldom available) or invest your time and energy into building something that will save you money and whose specs can outperform mass produced items?

After saying all of the above here are some of my personal experiences:
• Wall to wall carpet absorbs much more high frequencies than I first expected so to prevent a ‘dead sounding’ room, I focused on using diffusion rather than more absorption for mid/high frequencies which works like a charm. I also put a hard diffusive/reflective front face to many of my bass traps to again prevent further absorption of mid/high frequencies.
• Two parallel side walls introduced a very audible flutter echo which was eliminated with diffusion
• Walls with openings (e.g. doors, windows) extend the ‘acoustical length’ of the room dimension. For example, in my room placing bass trap absorption out from the front wall (which has a door that was shut) at the 25% point of 80Hz didn’t have the same impact as when the absorbers were moved to the back wall (with no door/windows) and placed at the exact same point.
• Experiment with the depth of the air space behind your resistive type bass traps. Real audible differences can be heard by pulling them out further and further from the corners.

Good luck.

Thanks for all the suggestions. My speakers died, necessitating replacement, so this project must be postponed. The new ones do bass very well, so there is no doubt I will need to address the room asap.

ANSWER-Start in the corners with some type of bass control(trap) all rooms could use help with the first order standing waves.