Adjusting Room sound using material damping methods (not DSP)

[STHLS5]

I recently moved from a house built in 1970 to our new (very old) one dating rom 1790. ... The old 1790s house seems to "eat" all unwanted bass. The antiparallel walls help to avoid standing waves....

I can't help noticing the fact that you moved from a 40 year old house to a 220 year old. Maybe, it is something unusual for Europeans but over here it almost unheard of.


About your beautiful and spacious room with anti parallel walls, you must be rediscovering music all over again.

ST

[1ryal]

OK

Here's my effort, apologies for the poor lighting in the photographs, I'm never home in daylight hours at the moment.

I modified A.S's design a little by adding 15 cm wide wooden pieces around the perimeter. There's 20 cms depth of Rockwool (compressed slightly when the fabric was tacked on) and I got my wonderfully understanding wife to choose the fabric ;)

Following a little experimentation I found an improvement in sound quality was achieved by placing them behind and a little to the side of the speakers, I suppose it has helped negate the first reflections from the wall behind.

I'de like to publically give my thanks to A.S. for his demonstrations here and guiding this rather special group through many interesting topics.

[Sebastien]

... Two absorbers would allow you to tame the side-wall reflections; four, the side wall and floor or behind the speakers...

I'm really tempt to try those "fibrerock" DIY damping panels at home. I already made some renovations with that product. We have Roxul company distributed here in Quebec. This product is easy to manipulate, safer than fibreglass and gets better proprieties. Plus, it is easy to cut with a simple knife bread. But for sensitive skin person, please wear gloves to manipulate it.

Actually, I want to ask your opinion about where to place the panels. There is already behind my left speaker my audio rack and behind the right one, some shelves full of books. The left side wall is full of LP and books, the right one is far away. Between the speakers sits a big couch. All of these will be difficult to change place. Just behind my listening position, I already have a studio grade panel absorber, 3 inches thick.

Do you think that I should work on floor's first reflections? On the ceiling ones? Built the panels and experiment? Any idea are welcome.

Thanks,

Sebastien

[BAS-H]

It sounds like you've hit the nail on the head, Sebastien. It looks like your walls are nicely treated as they are, leaving the floor and ceiling as prime spots for absorption panels. If you have carpet or rugs, I'd work on the ceiling first.

Best, Ben

[Sebastien]

I'm actually on a two months parental holiday with my 6 months old daughter. It means that, when she sleeps, I have time to work on some projects. So I did this week my first DIY panels exactly as described by Alan.

Now I have four panels. I can play with them in my living room to see how it influences the sound. I realise that there is a great improvement when I place two of them on the floor, in face of the speaker. It really reduces floor's first reflections. Plus, when I place one behind each speaker, the sound is more focused. It think that it cuts the bass that goes and bounces at this place.

After all, I realised that: 1) the glue in spray have some difficulties to make its effect when you don't have the time to place it quickly on the fibrerock. You must be rapid; 2) The panel I did are not freestanding; 3) The panel are really easy to move around in my house. This allows me to use them when I do some serious listening and I can store them elsewhere easily; 4) It is a cheap and quick way to treat your room and improve the sound.

The entire project cost me $75 CAN. This is way cheaper than most of the professional studio panels for the same results.

Sebastien

[Sebastien]

For those who have already fallow the facts about my listening room, they know that I have a big couch that sits right between my pair of SHL5. The couch is just few inches behind. We give this couch 4 days ago and what an impact on the sound. I can't say that the impact is positive. The bass from the SHL5 is to loud and no more in tonal balance with the rest of the frequencies. I must say that there is a brick wall directly behind the speakers. But the interesting fact is that I hear some new sounds and particular timbers in pieces I know well.

I realise that my couch was an important damping in my "listening-living" room. I found that the sound is more focus, realist and that the bass in more controlled with the couch there. You often see some damping panels right behind the speakers. Well, mine are a couch!

Good for me, there is a new couch that will go there soon. I'll have to see if the damping effect will be similar. Story to follow...

Sebastien

[A.S.]

I was installing M40.1/M20 this week at a studio (more info to follow) and had my first encounter both on the studio floor (a large brick-built open space) and in the control rooms with an attractive and effective Vicoustic damping solution. I was lucky that Phil Beaumont, the UK distributor of the panels was on site to show me the various panels they'd installed. The client seemed very happy. The panels clearly worked (they passed the hand clap test) and they looked great.

The manufacturing company is Vicoustics in Portugal.

The panels I encountered were the Wave Wood and the foam absorbers which looked great in a dark red colour. The general picture portfolio is here.

I wanted to take some pictures of the half-installed panels but it was decided to wait until the entire installation was complete and fully wired in a couple of months and then, when delivering another pair of M40s take some pictures then. I cannot say with certainty whether these panels are more or less effective than the Rockwool DIY one's we've been discussing here. They do have the advantage of looking very smart and being ready to use. I have no idea about cost. Apparently some clients attach them to the wall with velcro so they can be removed.

The bass traps look very interesting (not used at the studio). Taken at face value, the graph on this page suggests that in the 60-90Hz bass region where most untreated domestic listening rooms have a bass issue to one degree or another, the 19cm trap (the blue trace) is especially absorptive. The smaller ones far less so.

[A.S.]

I was installing M40.1/M20 this week at a studio ....

The dubbing/voice-over are uses a more conventional thick fibreglass wall treatment arrangement. ITV have kindly sent on these pictures.

You can see in the pictures attached that an arrangement of deep compartments are filled with Rockwool. This is held in place by heavy grade 'chicken wire'. The whole wall is then covered with a heavy drape curtain, which can be easily removed for cleaning. The curtain has a slightly sparkly finish so brightens up the room. I'm not sure if this wall treatment is finalised in this room, but it seems that there is a combination in the wall of completely Rockwool filled compartments, unfilled compartments and hard-faced areas. This would allow the acoustics to be tuned so that the overall effect is not too dry and hence not oppressive to work in.

As I mentioned, many more pictures of modern attractive surface-treatment will be available when the installation is complete.

>

[BAS-H]

How interesting. I am surprised the heavy, shiny curtain doesn't counter the absorption by the Rockwool. Perhaps it is flexible enough to move with the sound waves, and so pass them on towards the absorbers. Or perhaps it is porous enough to allow pressure waves to flow through.

[kukakunga]

Hello from Canada!

It has been a while since I have visited the forums and was happy to see that there is some discussion on the subject of acoustic treatment of listening rooms. I have been pursuing my own set of treatments and have done a lot of experimenting over the last two years. I will try to share some of the key points of what I have learned and also some of what my priorities have been.

- DIY acoustic treatments can be very effective, broadband absorbers and bass traps can be built with basic skills and readily available materials. One of the best sites I have found in terms of DIY resources is http://forum.studiotips.com/index.php

- My first attempt was to build some simple 2x4ft broadband absorbers, I built two and mounted them behind the speakers. It was very apparent that these absorbers worked, standing next to one feels kind of like an acoustic black hole. Later I built 2 more and mounted them behind my listening position, then I built two large floor to ceiling "Superchunks" bass traps and another set of panels for the ceiling. The bass traps really bring things into focus, every other room I hear now sounds flabby in comparison, bass trapping results in tight, tuneful, balanced bass that effects everything else in that it now does not blubber itself all over everything in both the time and frequency domain.

- I will try not to blab too long....I have much to say on the subject but will focus on a few key points. Treating my room to the point it is at now resulted in a few days of my wife hating what I had done and the room's sound being unconmortable at first. We are not used to hearing our domestic spaces have so little reverb, it sounded like a weight on your ears, but after a matter of two days you get over it and the benefits become very obvious. Don't overdo the absorber thing....a strategically placed balance will allow your brain to be "human" and your room to disappear.

-Conversation in my room is very easy to understand across the room, even though the level is lower. My TV now sounds as crappy as always, BUT..sometimes the image is huge and way beyond where it should be, speech is much easier to understand.

-On the music side, I used to listen sometimes late at night at quite low volume, since treating the room it is harder to get a convincing and "connected" musical presentation at those low volumes due to the lack of reflection in the space, in one way a negative....as some have suggested side wall reflections are good. So, for proper listening in a treated space it is necessary for you to have volume sufficient to convince your brain that the acoustic space in the recording is now your acoustic space.....you've erased a good part of the room. To me, that's a good thing, I want to hear the speaker and the acoustic space of the recording.

I have too much to say right now so I will post some pics for now and revisit with more comments later, I look forward to more discussion on this subject.

[kittykat]

... compartments are filled with Rockwool.

There is some DIY info here if anyone is interested in building their own...

http://www.radford.edu/~shelm/acoustics/bass-traps.html

Rockwool is even used in a Gatling gun post maintenance test facility. The guns are fired inside a building (>200dB) and Rockwool behind chicken wire have been found to be effective in toning down the high frequency aspects.

[ummaya]

Hi kukakunga,

Sorry to hijack this thread...

I really like the look of the stands on which your speakers stand. I love their simple and almost rustic look with no wannabe techno-futuristic design. I am thinking to get such stands for my brand new C7 that I will receive next week. Are these DIY stands ?

{Moderator's comment: You can always message the poster directly through the Harbeth User Group messaging facility and ask the question directly .....}

[kukakunga]

Hi Everyone,

I have been discussing some acoustics topics in another part of the forum, "Harbeth at Home Pictures", and thought I should move the questions and my responses over here for the benefit of this discussion. I appologize if some of the text is a repeat of my earlier post.

Would you be able to say what made the biggest sound improvement, treatment wise eg. was it the rear/ front diffusers, ceiling/ brick absorption. At what point did you decide it was sufficient?

How long is your speaker cable? My advice better use longer interconnect cable instead of speaker cable.

Nice setup and thanks for sharing. BTW what's that on the ceiling? What I can see there's stacks of uncovered (exposed) rock wool. If my guess is correct, please cover those rock wools. Those loose fibre will be all over your room (airborne). It's not healthy and long exposure could cause respiratory problems.

Thanks Guys for your comments and concerns.

Re: Speaker cable: I use Supra Ply 3.4s, this is a low resistance, sheilded, tinned copper cable. http://www.jenving.se/?p=ply The length is unequal, one is around 18ft and the other is around 24ft. From what I've read, I am not very concerned with the length or the fact they are of different lengths, I've found no conclusive evidence indicating that this cable design will present any adverse effects. They are very reasonably priced at around $15/meter, the tinning prevents oxidation...which I really like, and they are very easy to work with. Long interconnects are not an issue since I've moved my rig off to the side, interconnects that long would be very pricey. I use an Eico HF81 integrated amp presently so pre-power is not an issue, I have numerous sources going into the amp so it has to stay close to the sources.

Re:Danger!: I do intend to have everything covered to prevent any fiber release, I am still in the testing stage with my treatment......well, not changing much now...so soon I will seal everything up. I found some good info regarding the uses of these mineral fibres in acoustic applications and the good news is that Rockwool is safe. http://www.gearslutz.com/board/bass-...rs-review.html

Re: Acoustics Treatment: I first made a set of two broadband panels 2 years ago, those are the ones on either side of the TV. The effects were obvious with just those two, they did kill some of the room and prevented the speakers from refecting much from that wall, inherent in the design the SHL5 throws a fair bit from it's cabinet walls so this was considered. Standing next to one of these panels is interesting...it's like a black hole for sound...and you "hear" it....or not...lol.

Recently I decided to complete the plans for more broadband absorption and also implement bass traps into the corners, you can see the large black fabric in the corner, this is a "superchunks" floor to ceiling bass trap made of triangles of Rockwool stacked up. The addition of the bass traps and rear panels happened around the same time, the biggest improvement overall was the bass trapping. There is a tipping point in treatment where you end up with adequate broadband absorption and bass needs to be tackled less you end up with a dull, lifeless, bloated sounding room. The bass traps need be factored into the HF absorption in that they have very large surface area, they are not in zones of high direct SPL's but still take a lot of energy out of the room. So, it doesn't look like a lot of absorption overall but it is placed in areas of high energy first reflection points, ceiling and wall behind chair especially, the idea being to suck it up there before it has a chance to bounce more.

The bass traps bring it all together, everything snaps into focus and you suddenly find your Harbeth and 14watt Eico capable of incredibly tight bass extending down where you never imagined it could. The detail and ability to hear complex bass parts from multiple instruments and actually having a very distinct bass "image" surprised me a lot. That clarity down low also allows everything above to have it's own space without ever getting muddied or stepped on. And of course with all the HF absorption there is great low-level detail and the timing that comes from the lack of smear created in the room's reflective feild.

The SHL5's are sometimes seen as speakers that create more of a tonal landscape and not so much precise imaging, not now, the image has incredible depth, width, and scarry sounding presence in the way performers appear on the stage, the tonal strengths of the speaker along side sometimes make it seem like the ghost of long dead singers has arrived and is floating 15ft behind your wall.

The ceiling panel had a very specific impact on the upper mid-range in that I had always had a bit of peaky bahaviour, especially up around 2 octaves above middle c...somewhere around 1000Hz, this was partly due to the ceiling reflections and also partly due to having a large, soft, leather sofa as my listening spot. The sofa caused a surprising amount of shift around the mids, especially if you head was leaning at all into the back of it. With the sofa moved and the panel installed things are much better. My wife was pissed of course and questioned my need to move the sofa, so one day we moved it back and I had her listen a number of times....moving the sofa each time.....and it was pretty obvious to her that the sofa was very bad, so she conceded even though we lost a nice comfy place to watch TV in the process.

BTW, yes the ceiling panel is basically a wood frame with thin fabric I had in the stairwell......then one day....light bulb moment, and another way to anger my wife. I just stacked Rockwool on top of it, it was ideal because the frame did allow for some reflection and dispersion rather than totally absorbing, I didn't want to overdo it with too much damping.

Speaking of which.....after I had installed the bass traps, ceiling panels, and everything was mounted I was confronted with some doubts. The room felt heavy on my ears, not natural, but at the same time was amazing when I listened to music at moderate volume. It was also cool how intelligable conversation from across the room was, it sounded half as loud but was twice as easy to understand! Same with my TV, the thing was imaging like a champ!

Again....my wife's reaction was to demand I take it all down and that it was freaking out her brain....and right she was, we were not used to how it sounded. Within two-three days of listening a lot I soon became acclimatized and didn't notice it much any more, my wife took a bit longer but now when we walk into the room there is nothing odd about it at all, it does take some time and I suggest to anyone doing treatment to give adequate time for your brain to adjust, I've seen too many folks give up after either putting too much treatment up or not waiting long enough before making changes, be patient, methodical, and know why you are doing any particular thing, at least in theory.

One more observation about the sound now, I used to listen at low levels, late at night, and the presentation was quite nice, with the treatment in place that is no longer the case. The levels I was at before sound distant, disconnected, and small. When you make part of the room dissapear you also have to realize that you've taken what used to be a mixed ambient sound feild, room reverb+reverb in recording, and removed a good portion of it. You are left with the sound of the room the recording was made in, and to me, that's the goal right! So, a bit more volume, not that much really, is necessary to bring the detail on the recording up to a level that convinces your brain that you are in THAT space and the information is adequate that your brain has no issue with it. When that happens, at moderate, confortable, volume, you really feel you are there and you really here detail....I now know what detail is in a much more significant sense.

I also know that when I hear folks talk about detail, and I see bare walls and hardwood floors, there is no possible way to have detail under those circumstances, no matter how expensive the gear....and it's a shame because I see so many pictures of super expensive systems set up in terrible rooms, and I can hear in my mind how much smearing there is and how much bass bloat there is no matter what those 8 x 12 inch driver inspire visually.

A couple more things I thought I'd mention. The pseudo-diffusor in back of my listening position is more for looks than as an actual mathematically designed element. A real skyline diffusor has specific depths and arrangments for each "block', this was an experiment just for fun and it likely has limited effectiveness. In general, diffusion of any type, QRD, Skyline, or Poly, needs more space from the listener. I may attempt to build a couple of polycylindrical diffusors to place on either side of my absorbers in back of my chair, not so much that I need them but I would like to try a build and since they will not absorb any more they can only improve the overall room response. They would be positioned on the wall not far off axis so would be diffusing at a good first reflection point.

I also plan to put a half "superchunk" trap behind my rack in that corner, I did an experiment with adding one of my OC703 panels to that corner and made comparisons in my vinyl playback with and without the panel acting as a bass trap across the corner. The concern was that my turntable was close enough to the corner to be effected by bass buildup, as you can see I have placed the TT as far out on the rack from the corner as possible but did notice quite a difference with the panel, there was less mud to a great degree. So, I will built the bass trap and possibly have one panel across the brick to prevent reflection across the range from that wall to the rack. As you can see my rack is an ikea butcher block affair, it is sturdy and with a 100lb marble slab on top plus my 100lb Lenco TT it has quite a bit of mass keeping it stable, that's not to say that it does not have some resonant frequencies that could be diminished from adding some obsorption behind it....just in case.

[thaimusic]

First, thanks to all who contribute here. We’ve found this forum a valuable and refreshing resource. We hope some of you may be able to assist us better understand, and potentially tame, some or the errant sounds in our proposed listing space.

As illustrated in the attached sketch, we have a large L-shaped open floor plan (13m x 8m with 2.4m ceilings), the corner segment of which we would like to curtain-off during listening sessions.

The room/house is very active: plaster over brick walls, tile on concrete floor, ¼” gipson ceiling (vaulted over proposed listening area) and very little soft furniture or curtains. The curved wall may also be an issue.

We are presently keen on the HL5 and yet to be determined integrated amp and DAC. We realize, however, we’ve gotten ahead of ourselves as our proposed listening space may be ill-equipped to deliver the advantages of such an investment.

So we are interested in feedback, especially on the value some floor-to-ceiling curtains to cordon off the area might offer in improving the presentation. Our listening interests are jazz, classical and traditional music, generally presented at moderate volumes.

Other treatments contemplated are curtains or other acoustically beneficial window coverings for the room and an area rug in front of the loudspeakers. Possibly something with the ceiling as the segment over the proposed listening area is already of a different design from the adjacent areas, so architecturally might be easier to modify.

Thanks

[Don Leman]

I always think the left and right speaker should have similar environments. Would it be possible for you to rotate the couch and speakers 45 degrees counter clockwise?

[BAS-H]

That's not my experience Don. http://www.harbeth.co.uk/usergroup/a...3&d=1294410769. The sound sounds perfectly balanced and even, here. Perhaps that might be due to my room being pretty sound-sympathetic in the first place, though.

[thaimusic]

I always think the left and right speaker should have similar environments. Would it be possible for you to rotate the couch and speakers 45 degrees counter clockwise?

Wow, folks are thinking. Thanks. We actually did give this some thought awhile back. Unfortunately, there are french doors on the curved wall opposite the short 8m stretch. Also, if you look at the image, the gradient is a stairway headed up, with a small hallway to a bathroom adjacent.

It's never easy.

[Paul G Smith]

For recording radio drama we used to use a large studio similar in size to your living area, but without the rounded corner. Using VERY heavy curtains suspended from the ceiling we used to achieve a very good separation between the "live" end with it's wooden floor, and the "soft" area with a carpeted area. We then had to use plexiglass reflective screens to face the curtain into the "live" area!
OK, now this was to create two differing acoustics for actors to work in but I think that there are areas in common with what you want to do. The floor to ceiling curtains we had to use to achieve a sufficient amount of sound absorption were very heavy. The outer curtain was a very heavy lined velvet cotton drape and there was an inner separate curtain as a fireproof liner. These worked incredibly well but cost a small fortune.

I think that no matter which seating arrangement you use, you may need floor to ceiling drapes as heavy as you can afford to retain a low reverberation time in the listening area as the reflections from the hard plaster will need absorbing before they can reflect again. If you were to curtain off the reflective window that would help enormously too.
One advantage of such a large room is that the bass performance should be very smooth, the curtains absorptive effect diminishes with frequency.

Once the curtains are in place you could juggle with the position of speakers and listening position before making them permanent.

[thaimusic]

Thanks Paul,

Very helpful, encouraging. Nice to know there is some potential. Fortunately, the still functioning textile industry here and mom and pop shops doing all manner of industrial sewing and curtain jobs, we should be able to get some functional drapes for far less than the cost of a single Harbeth. Were that not the case, don't think we would be pursuing this at all. Just need to figure out that inner drape material. Here it could still be asbestos. I've read that wool is quite good for sound insolation?

[Paul G Smith]

Weight is what you need!

I don't think it matters much if it's in one layer or multiple layers. The surface facing the listening area should have the more absorbent finish. The inside liner in the studio was there to comply with the strict fire regulations.

good luck and good listening.