Room treatment advice needed


I have a pair of Yamaha NS-1000x as mains in my primary listening room, and I love them so much I bought a second pair for my office. The new pair is a gorgeous rare walnut cabinet and the drivers are pristine without blemishes. A very lucky find that I treasure. I tried them with my original equipment in my main room, and they are wonderful. However, the new pair sounds awful: super-detailed, as expected, but thin, trebly, no bass, no imaging at all, in my office.

My office is small (I'm in Japan), less than 3X4 meters. It has a hard wall on one side, but that side has my work desk and computer. The other three walls are composed of thin sliding doors made of plexiglass.

The floor is of firm wood, covered by a carpet.

The Yamahas are currently on brass cones on granite slabs over cement blocks. I have put blotches of blue tac between the stone slabs.

I know these large, heavy speakers are huge overkill for such a small room, but I want to make them work (or face a serious marriage crisis...) there. I am wondering what should be my first aim in room treatment, and hope for the advice of this boards' minds.

What comes to my mind first is thick curtains to cover the plexiglass sliding door/walls, hopefully reducing lots of high-end reflections. Do you guys agree with that?

What other steps should I take?

Main source/amp is flac files fed from iMac or Wav from iPod through an iDecco. I also sometimes bring in my Luxman amp and Njoe Tjoeb CD player instead, from my main room. Wonderful sounds in the main room, but no magic in the office in either case.

On the other hand, the iMac/iDecco combination sounds rich, full, warm, and detailed through a pair of Quad 12L's on my desktop. These are placed with the rear-port bass outlets facing the hard wall. They are on small granite slabs on my computer desk on either side of a 27-inch iMac, with blue tac between slabs and desk and slabs and speaker. They are in a near-field listening position, meaning that I hear mainly the unreflected sound from them, as opposed to my Yamahas (behind me while I work), from which many reflections reach my ears together with the direct speaker sound.

Please freely offer advice on getting the best sounds out of my Yamahas that they are capable of in this small, plexiglass-walled office space. I will greatly appreciate your opinions.
deaf_in_left_eye
I know this is stupid, guys, but I solved my problem. I just moved my Luxman amp and CD player in from the other room, and wa-la! It sounds absolutely superb. The bass in my office is even better from the new Yammies on cement blocks than in my listening room on thin stone slabs.

The problem wasn't in room reflections or bad acoustics, though there is certainly room for improvement there.

I had been assuming all along that the iDecco had to sound great with the Yammies, because it sounds so good with the Quads. WRONG!!...

This was perhaps my first expensive, involved lesson in component compatibility.

iDecco + Quad bookshelves = Good
Luxman + Yamahas = bliss
Couples that can't be intermixed.

Thanks for all your help. I'm still going to try some of the tweaks you all suggested, and see just how good it can get...
Go out and land yourself a copy of Dr Floyd Toole's latest book.

In it you'll learn why treating 1st reflection points is NOT a good idea; where your room's transition frequency lies and how the treatment strategy below this frequency differs from the strategy above it; how various bass absorption methods work and which may be best for your room size; why mid/high frequencies should be reflected or diffused rather than absorbed; where diffusion should be placed and whether it should be 1D or 2D kind of diffusion and what available brands/models are which; how thick absorption should be and how far out from the wall the air space behind it should be . . . and many more very important nuggets.

In the end you are listening to direct (from the speakers) and indirect sound (reflections of room boundaries) and ideally you wish to remove the room from the equation, or at least minimize its negative effects on the sound and enjoy its positive effects on the sound. But knowing which parts of the room will harm the sound and which will be beneficial is of untmost importance. Otherwise you'll spend (waste?) much time trying many itterative variations of speaker, listening position placement options.

Dr Toole is not affiliated with any acoustical treatment manufacturers so he calls a spade a spade. He wrote the book after he retired so again he is unbiased and a world renown expert.

(I have never met the man, nor am I related in any way.)

Good luck.
Kevin
"treating 1st reflection points is NOT a good idea"

I think you're distorting what Toole says.

On page 116 of Sound Reproduction he suggests "add sound absorbing material to front wall."

On page 119 he suggests "for stereo listening, leave side walls reflective at reflection points."

There's a lot of discussion of how side wall reflections increase a sense of spaciousness.
I find a mix of absoprtion and diffusion works best. You really have to experiment to achieve the right mix and the effect you desire. Diffusion would decrease and spread out specular reflection and make the room sound bigger.

With mostly absorption, the sound in my room was very focused but I was always aware of the side boundaries. The diffusors along the side and front wall increased the perceived width and depth of the soundstage and relieved a lot of combfiltering problems at mid and high frequencies. The traps or absorption was not as effective as the diffusors at the upper frequencies.

When I had too much diffusion along the frontwall, the soundstage was too far away and individual instrument lost focus. It is really up to you to decide whether you want a large hall sound vs small Jazz venue. Good luck.
Glai - I agree with what you've said and experienced.

I'd add that I find a mix of LOW FREQ absoprtion and MID/HIGH FREQ diffusion works best. Broadband absorption for low-to-high frequencies tends to narrow the soundstage and create more defined sound images in space when placed on side walls, whereas diffusion achieves the opposite effect - personal preferences prevail of course. I found that absorption on the front wall center deepened the apparent sound stage depth.

The diffusors along the side wall should be 1D and diffuse horizontally to increase apparent sounrce width if bare wall reflections are not being used. I used diffusion (hemi-cylindrical) to eliminate flutter echo between two paralel side walls. If your absorption traps were not as effective as diffusors at upper frequencies may be due to the density of the fiberglass and angle of incidence: Higher fibreglass densities will tend to reduce higher frequency absorption as will small angles of incidence.

One conclusion Toole arrived at was that 1st reflection point absorption was a GOOD thing IF you were a musician mixing your music or a stereo component reviewer, otherwise 1st reflections were a positive things that increased listener envelopment and apparent source width, which my humble unscientific tests have concurred with.