room treatment gurus, please

You can, somewhat, overcome some issues with extra absorption where you can.

Consider the AM Acoustics room mode simulator to help place listener and speakers. 

Include the ceiling and floor in your calculations.  Consider curtains in front of the sliding doors.

I have used GIK acoustic panels, and it worked great. I have also used DSP using convolution filters remotely created by the acoustic guru behind this company.

Digital Room Calibration Services, Convolver, Headphone Filtersets

It was even better than the panels since there were a few options to tailor the sound.

I actually tossed the GIK panels when I moved to another room. Reason being is that I had the guru as my safety net in case the room was wonky. I was not concerned about the loss of the physical treatments.

Now the DSP I am suggesting is best done on a client such as ROON or JRiver and it will ONLY work on digital streaming, Not your TT or tuner. No analog. The computer to run this can be far away in another room and not near your audio gear.

Glass walls are the worst. A good room is a mix of absorption and diffusion.

DSP won’t fix 1st reflection points whereas your panels would have.

I was using dsp for a couple years trying to get the sound right with my speakers that were just too big for my current room. Buying speakers to fit my room, adjusting the speakers using the techniques from Jim Smith and Cardas, I stopped using dsp and allow me to put up for sale some of my absorption panels.

Drywall with Cavities are the most difficult to work with. 

A Filled Cavity is the better of the Two Evils, the room coupling of Speakers is quite difficult in such an environment. 

It was described to me, by an individual who is quite skilled at producing Speakers, it is due to Drywall Systems with Cavities, that Typical Speaker Designs produced in the US are heavilyy augmented in the Bass Frequency.  The same individual stated that when such designs arrive to be a sale item in the UK, when used in a Typical UK Home the Bass is noticeably overbearing. 

A corner set up can be effective in a square room. You could also consult an acoustician. Jeff at hdacoustics is very good and I highly recommend him. Good luck!

You didn’t note the speaker and listening chair placement. I am stuck with a difficult room but have found inches of speaker movement can make a significant difference.  Same with moving the listening chair. It might be interesting to create a near-field space in the middle of the room temporarily (like at a mixing board) just to hear what’s possible. Also, the corner configuration mentioned above solves a lot of problems. 
 

Has your friend tried damping the rear wall to hold down standing waves?  Or any other experiments with the room?  Rugs on the floor?  A little bit of absorption can make big changes. Of course, if you can have an acoustician treat the room, all the better. I have found the experimentation interesting and kind of fun. It’s helpful to have friends with good ears who can provide feedback. 

You can still enjoy the system by using the right volume, not to overwhelm the room.Maybe you can use room divider that folds .

Having tried three types of room treatment in two awkward rooms and comparing these to a one room that is close to ideal. I tried Dirac (Datasat and others), Trinnov (both multi and 2 channel / 2.2 channel) and Lyngdorf "roomperfect".

Only Trinnov gave the level of performance and integration I was looking for (initially tried ST2 HiFi, then Amethyst). I have glass on two sides in awkward places in one of the rooms and on all for sides two with awkward places in another.  The difference between on correction on / off and completely bypassed (just to check against 'off) is huge.

But I acknowledge that some of the DSP benefit is that in both instances I am using speakers with smaller bass drivers than I would like and consequently I am integrating speaker arrays / sub integrations which would not be "an advantage" in a 2.0. 

However, where one of the sets of speakers I use are 2 way then I found the dsp crossovers were for both a single seat and especially for a multi-listening position more effective than either single or bi-amping without correction.   Comparing this to the set-up in the 'ideal' room gave a 'awkward room' performance that was quite close. Even the 'ideal', gained in timephase precision.

To be clear I am not in anyway suggesting that physical correction should not be undertaken or ignored.  But in cases where I simply could not remove windows, etc., Trinnov DSP did and excellent job.  

Get the book and make a call to the author; he's very accommodating with his expertise:

Get Better Sound by Jim Smith

Consider suwoofers, which could be placed in a location where the bass modes couple better to the listening position. 

Thanks for all the suggestions. Looks like I have some research to do.

I contacted GIK Acoustics and added the Tri-Trap Corner Bass traps per their recommendation.  I could not add side wall acoustic panels due to furniture placement. To my ears, the bass traps improved bass definition and overall imaging.  I have a nearfield setup due to my small listening space.  

Submit a request to GIK Acoustics with photos and all the information you posted here. Deal with the pros. That’s your best bet. 

I engaged Vicoustics to provide an acoustic treatment plan for my listening room. They orovided 3D diagrams and a list of their recommended products. This can get expensive so I sourced 2nd hand absorption panels, diffusers and bass traps. Your room is a huge part of the listening experience. I could not be happier with the result!

I suggest as the initial investigation and one that costs not too much monies a period of learning about the room and how the Speakers are able to couple to it.

A stool type chair and a increased length of Speaker Cables will allow for the repositioning of the Speakers and placing the stool at the correct listing point to enable a reasonably comfortable listen.

At each location Toe out and Toe in the Speakers to change how the sound is dispersed. The Stool can be placed nearer the speakers of further away to see how the dispersal of sound creates a sound that satisfies the listener.

It is well worth learning a little about the sound able to be produced in a room, before spending monies on somebody to make available similar learning using tools that are able to make the job a little easier, as well as create a data to show what ears are already reporting on. 

FYI I created a design for  my own room using my own ears and addition of DIY Produced Acoustic Controls, that really do work to my satisfaction. Visitors to the audio room are always impressed with the Speaker Coupling to the Space.

Yes I could have spent on a Professional Service and Commercial available Product to do something similar, but would it be slightly better or slightly worse? Does it really matter ? Improved is Improved and I certainly got improved.   

@pindac,

I agree with your assessment. There is nothing more satisfying than experimenting on your own and realizing the benefits of tweaking things here and there to realize greater outcomes. 
 

For my own personal philosophy, I have learned through trial and error that I much prefer to have strategically placed diffusion along with some absorption products to balance the room. I use old school Test Cd”s, Radio Shack sound pressure level meters, Rives Audio Professional audio test measuring kit, and a PAA audio measurement device. However, my ears tell me what is good overall, no matter the measurements. These tools are guides to help one understand the audio environment where you will be listening. Also, if I decide to use subs, I use a Velodyne SMS-1 sub EQ which is plugged in a tape loop on my Octave Jubilee preamp. 
 

I much prefer reverberation and ambiance over a less dry and less reverberating sound field. 
 

Can you please share your a sampling of your DIY acoustic controls? Would be interested to see what others are doing.