Diagnosis please.

Have only noticed one thing unpleasant about (as opposed to missing from) the sound of my current set-up. Symptoms are:

A 'ringing' quality to a section of the upper end of the sound (mid to upper soprano) closest analogy is wet finger on a wine glass rim, sort of 'one note treble'. Not present above or below this range, and the quick fix is to turn it down a bit.

Speakers are PMC DB1 blu-tacked to Mission Stance stands (sand filled) spiked onto ceramic tiled floor. Room 4.5 x 4.3m, not generally well damped but big thick wool rug on floor.

Understanding bed-side manner appreciated.

 

Clap your hands hard in the room. See if the same "one note" is generated.

 

Yes, that would be my suggestion. It's amazing what you can hear from a simple hand clap. If you listen carefully, all sorts of surprising sounds can be heard in an untreated room. You may need some diffusion (bookcases are good).

 

speakers spiked on to a hard floor may produce a ringing sound, maybe try someting not so pointy, like wooden door handles for a cheap example, (or RA toylite for a more expensive idea)

 

Have done this in the past and the room has got better since we first moved in (4/5 months ago) but will check again this w/e.

diffusion/bookcases - are we talking uneven surfaces here or adding mass, or both. Do curtains etc. have a part to play? (there are still 20 boxes of books waiting to be unpacked).

Have I got this right: low frequencies (can) produce standing waves which reduce the sound that is heard?
Do high frequencies do something different, as in this case where they appear to be building up?

 

I have been looking into room acoustics of late in quite significant detail.

There are many separate issues. The one that it seems you're contending with is "Slap echo". Two ways to deal with it are some sort of soft wall covering (rugs, acoustic foam, paintings, etc) or some sort of diffusion (purpose made diffusers, bookshelf with different size/depth books, etc). Absorbancy will make the room sound deader, while diffusion will maintain greater openness.

 

If you are (slightly un-)happy and you know it clap your hands,
rpt.

Firstly, standing in middle of room clap as suggested - nothing particular stands out - same at listening position - room probably lacks a little resonance if anything. So have a play with Blue Peter* spike supports, does very little for the posted problem but improves several other areas (I think), also ended up re-positioning speakers again so not sure which had which effect. Top end (eg Art Blakey cymbals) clearer, more precise. Bass bit more warmth.

Back to the clapping. Investigated a bit further and found one corner does have a definate ring in the area that is troubling me! It seems to be down to a window (the room has three internal windows which therefore don't have curtains) which is above and behind the speaker. The speakers are rear ported but my assumption is that this is only relavant to low frequencies; and the window is six inches or so above the top of the speaker. So it doesn't seem like direct sound is affecting the window.
The test cd is quite extreme, three unaccompanied women singing medieval chant, closely miked (very audible breathing) in a cathedral. So lots of high and intense stuff, but what it means is that when I can feel vibration in the glass (and I can) it's not down to bass.
Is there a satisfactory way of damping glass, if only to elimimate it from this line of inquirey?
If the room is already quite dead soundwise, diffusion would seem to be the way to go, but will general diffusion help in a specific area like this?

*Blue Peter spike supports:
Materials: 8 of plastic milk bottle lids (pref. with dimple for spike), 16 of 2 x 2cm pieces 3mm ply wood, blu tack.
Assemble 2 pieces ply, 2 layers blu tack, lid.
Yes I think sound is better than spikes straight onto ceramic tiles, however bright blue (red or green would be no better) clashes with floor so may actually consider buying something.

 

A curtain in front of that window?

 

As I said, it's an internal window (yes, one side of most windows is internal, in this case both sides are) though the previous owners did have a curtain in front of it. We would end up with curtains on all four walls and having them all drawn during the day would seem a bit of a shame (I never had pretensions to true hi-fi credentials). But yes, that was my initial thought as well. Now, if I hadn't taken down the curtain pole.....

 

Similar thing happened to me - when I sneezed, the ringing continued for a second or so, it was the radiator. Stuffed some foam behind it, hung my washing over it - sorted.

 

Is it possible to differentiate (ie hear the difference) between this kind of room (size, construction etc) dependant effect and individual problems like windows and radiators?

 

Coda - you have the same problem as me it seems!

Rught behind my seating position I have glass panels in wooden frames. I COULD block them out with sound absorbant/diffusive panels, but to do so would block the light, and cause a very dark and dingy stairwell.

Like yourself, I dont want to compromise the natural light in the house and the aesthetic appeal of the living room just for room acoustics.