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View Full Version : Room treatment -- reflective & absorptive surfaces (WARNING: long and boring!)



magiccarpetride
21-02-2011, 20:56
After spending literally years experimenting with different speakers, I've settled on the planar speakers (more specifically, Magnepan). These, in my opinion, have the ability to offer least colored, most naturally sounding music reproduction.

At first, while I was enjoying their uncanny lifelike sound, I was still being bothered by the residual glare that these overly lively speakers were producing. I started thinking about ways to reduce that glare, but it just so happened that at the same time I started getting into upgrading my source. The first thing I've noticed after replacing my CD player with the digital streaming player is a substantial reduction in glare caused by the digital artifacts. I then started enthusiastically chasing after the source component upgrades.

After doing some research, I've discovered Beresford Caiman DAC (arguably, the best bang for the buck in the DAC arena). And sure enough, Caiman managed to drastically lower the residual glare and digital artifacts.

Tickled by the very audible improvements in the digital source, I continued doing research in the digital transport arena, and soon enough ordered Logitech Squeezebox Touch. That player, plugged into Caiman, offered much more natural sound with reduced (again!) digital glare. I was one happy puppy.

Then, late last year, I've ordered a Gator board for Caiman, which yet again managed to drastically clean up and further reduce the unpleasant digital glare. So now I was sitting pretty, liking the sound very, very much.

But, there always seems to be room for improvement, so I kept researching. Soon enough, I came across the infamous Souncheck mods for the Touch. It didn't take much prodding from our own Gary 'Gaz' to push me into trying these upgrades. Once again, major improvements in the overall sound, more natural texture and soundstage, deeper depths and higher highs and all that jazz.

Lastly, I purchased the power mains conditioner, even though I was extremely skeptical. But I got it anyway, if anything, just for the surge protection. My god, the improvements I got from plugging into that conditioner were absolutely drastic -- just as I thought the sound could not theoretically get any better, that contraption managed to drastically lower the noise floor and to promote singers and instruments into the never before seen spotlight.

After that major achievement, I continued trying out various mods, but quickly realized that I've pretty much reached a point of diminishing returns. After trying various interconnects, and not hearing any, even the tiniest difference, I've decided that my audio chain has reached it's stabilization point. The sound is now as sweet as it can be, and I can finally relax and sit back and enjoy.

But not so fast (and here is where this long drawn boring story gets to its actual point): I am now thinking about tackling the last frontier -- room treatments! And here is what seems confusing to me with regards to these treatments:

My speakers (dipole) radiate sound both from the front (i.e. the part facing listeners) and from the back (i.e. the part facing the wall behind them). The sound emanating from the back of the speakers bounces off the wall behind them and then meshes up with the direct sound to produce the illusion of depth.

However, I've also read that 'audiophiles' recommend that the wall behind the speakers be treated with absorptive material, to dampen the unruly reflective sound waves. And I did precisely that yesterday: I hung two fairly large, absorptive pieces of textile behind each speaker. The result -- atrocious sound. It was as if I had somehow castrated my audio system. The bass suddenly became much louder, bloomy, and as if covered in maple syrup (very dark, deep, chocolatey, sticky). The mids became much more intimate, but lacking the space around them. The highs attained their own kind of overly colored euphonics -- much softer, silkier, safe sounding, liquid, vinyl-like, and somehow extremely tame.

All in all, the results of this back wall dampening started approaching the sound you can hear in the high-end audio stores when they're demoing those ultra expensive many tens of thousands of dollars worth speakers. Safe and secure sounding, but oh-so-lifeless and boring.

Yuch -- I couldn't stand that abomination! So I tore down those absorptive textiles, and then breathed a huge sigh of relief. The sound was thankfully restored back to its old former glorious self. Full of life, rude, impolite, but at the same time extremely authoritative, firm, kicking, and moving you to tears. Nothing safe and secure about it, I can tell you that.

So now I'm wondering: what's the suggested approach when treating the room? Is there a recommended 'best practices' ratio governing the absorbing/reflecting the sound?

Welder
21-02-2011, 21:09
Basically Alex the rule of thumb is, absorb bass and try to reflect everything else.
Your Maggie wouldn’t do troublesome bass I imagine; I could be wrong. What you need to do is research a bit on deflectors.
Absorbers, if not done spot on tend as you’ve noticed, suck the life out of the music.
Because of the way planer speakers work, I doubt very much that there is an awful lot you can do with room treatment without getting someone in to measure what’s going on.

Mr Pig
21-02-2011, 22:07
The bass suddenly became much louder, bloomy, and as if covered in maple syrup (very dark, deep, chocolatey, sticky).

What's happened is that the higher frequencies have been absorbed making the bass seem louder.


The mids became more intimate, but lacking the space. The highs attained their own kind of overly coloured euphonics -- much softer, silkier, safe sounding, liquid, vinyl-like, and somehow extremely tame.

I know exactly what you're talking about. If you keep making a Hi-Fi better it gets to a point where it starts to get worse! Live music is vibrant and alive. The only way to get recorded music to sound similar is to sail very close to the edge, not remove too much distortion and employ plenty of reflected sound without tipping into cacophony.

Don't feel bad, you've learned something that lots of Hi-Fi buffs never understand.

Clive
21-02-2011, 22:52
The absorbent wall should be behind the listener, not the dipole speakers. I too tried absorption behind my OBs......death.

In my room with OBs I have a pile of cardboard boxes (neater than it sounds) in one corner because the bass bounces around in a corner behind the speakers. The reverb measures way better with the boxes and the sound is totally transformed. Sort of a cheap tube trap. Measurement makes it all much easier but it's still not easy.

Ali Tait
21-02-2011, 23:55
Why treat the room at all if you are happy with the sound?

magiccarpetride
22-02-2011, 00:03
Why treat the room at all if you are happy with the sound?

Good question. I think it's just that I'm still buzzed by the flurry of recent upgrades which took the sound to the whole new level. Hard to stop now, although like I said I'm definitely experiencing a point of diminishing returns.

Many 'experts' claim that the biggest wins are to be had in the area of room treatments, so I'm curious to explore that option. So far, very negative results.

Ali Tait
22-02-2011, 00:10
As John says, I think you'd need to get the room measured, or you are just guessing. There are cheap and easy things to try though, like a rug between you and the speakers, including one on the ceiling, and as Clive says, try the wall behind you too.

John
22-02-2011, 08:04
Agree if you can get the room measured this would help. Its worth playing around with using cusions in different places just to see if they have an effect. Like Colin has pointed out we need room reflection, with dipole speakers you have to get reflections working for you its is not something we want to eliminate

jandl100
22-02-2011, 12:21
I used to have GIK acoustic panels on the wall behind each speaker and also one on the wall behind my listening chair.
Worked extremely well with my old Infinity RS2.5 which were di-pole speakers in the mids and treble.

But with the coming of my omni-directional MBL speakers the panels behind the speakers drastically reduced the imaging capability, so out they went. The panel behind the listening position has stayed, though.

Tbh - I'm not sure if measurements would have predicted this effect. You need to tune the room treatment to your particular system's subjective characteristics, ime.

Clive
22-02-2011, 13:22
Here's a couple of examples of what you can do with measurement, they show poor and partly fixed reverb. Measurement doesn't do everything for you, it mainly stops you going mad by giving you feedback that what you are hearing is real (or otherwise).

The less red and yellow the better, ideally keep the reverb down below 50ms, there's a vertical line on the LHS, just visible.

1st of all poor, ie without cardboard boxes in one corner:

http://i43.photobucket.com/albums/e359/cmeakins/lnoboxesheatMedium.jpg


Here I have the cardboard boxes in place and still one room mode to fix:

http://i43.photobucket.com/albums/e359/cmeakins/LRheatimproved.jpg


Here the room modes are reasonably well fixed:

http://i43.photobucket.com/albums/e359/cmeakins/LRP8Medium.jpg