artto's Klipschorn Room

[Cody_Mack]

Yes, that's correct. We would have had the mains on the long wall, and sloped the ceiling the other way, but that would have required much more of a stuctural change to the house and we would not have been able to back up far enough, so we were afraid that -- even with a Belle Klipsch center -- the sound stage would have been so wide (in degrees from listener position) that there would have been holes in the image between the Belle and each Khorn.

So, you mean you couldn’t sit far enough back from the front
wall; you were worried that the direct sound coming from the K-horns would be behind
you? Should they always be both pointing directly at you when you are in the
sweet spot? It would really depend on the size and shape of the room whether
that could be realized, huh? I have heard others talk about how when they had
them on the long wall, without a center speaker, that the Khorns just
disappeared, creating a perfect center stage. I don’t have any dimensions to go
along with those comments, nor where they were sitting in relation to the
Khorns. I have experienced that with Mallette’s setup; where your ears are dead
center between the Khorns,and they do indeed disappear. But
I would also consider the setup he had then as near-field. So I am wondering,
in a large to very large room, do you still try sit in that directional sweet
spot? Simply said, what is the geometry factor for the listening chair when
listening to Khorns?

I think that is very cool how you mounted the Belle. I will definitely
remember that. I will probably have a large space behind the front wall; planning
for infinite baffle subs, and maybe also built in equipment racks.

Rick

[artto]

Yes, that's correct. We would have had the mains on the long wall, and sloped the ceiling the other way, but that would have required much more of a stuctural change to the house and we would not have been able to back up far enough, so we were afraid that -- even with a Belle Klipsch center -- the sound stage would have been so wide (in degrees from listener position) that there would have been holes in the image between the Belle and each Khorn.

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So, you mean you couldn’t sit far enough back from the front
wall; you were worried that the direct sound coming from the K-horns would be behind
you? Should they always be both pointing directly at you when you are in the
sweet spot? It would really depend on the size and shape of the room whether
that could be realized, huh? I have heard others talk about how when they had
them on the long wall, without a center speaker, that the Khorns just
disappeared, creating a perfect center stage. I don’t have any dimensions to go
along with those comments, nor where they were sitting in relation to the
Khorns. I have experienced that with Mallette’s setup; where your ears are dead
center between the Khorns,and they do indeed disappear. But
I would also consider the setup he had then as near-field. So I am wondering,
in a large to very large room, do you still try sit in that directional sweet
spot? Simply said, what is the geometry factor for the listening chair when
listening to Khorns?

I think that is very cool how you mounted the Belle. I will definitely
remember that. I will probably have a large space behind the front wall; planning
for infinite baffle subs, and maybe also built in equipment racks.

Rick

I've had my Khorns with a Belle center on a 28' wall (19' deep) and have never had any issues with imaging between the Khorns and Belle. To me, the Belle added more depth to the sound stage (on appropriate recordings of course). It would be nice if you could just set the volume level of the Belle at one spot and forget about it. For some people that may be adequate. I've found I had vary that from -0db to -6dB. Eventually I added a Behringer DEQ2496 so I could put some delay in there to time algin the midrange driver with that of the Khorns. And quite frankly, getting the best out of that setup (wide-stage/long wall) IMHO has more to do with the room acoustics, especially because of the way Khorns radiate sound into the room. Its important to keep early reflections off the walls, ceiling and floor but still keep the room and corners "live". Personally I've never liked the way Khorns sound with a lot of absorption around them which is why I chose to use Masonite polycylinders around the upper part of the front and side walls to scatter the mid and treble sound.

And as far as the listening position goes, in stereo, there is (unfortunately) one and only one ideal seat. It's the nature of the beast. Also, where that center line sweet spot is will probably depend on the recording, your personal preferences and the room acoustics. I've found that on some recordings that are strident (like high strings of violins) I prefer to sit behind the "crosshairs" of the flanking speakers. On other recordings I might want to move my seat backward or forward to get more or less bass (room modes interacting with the speaker). It just depends. You have to experiment. Listen and take some measurements and record them and take some notes so you know what you're listening to and can easily go back if you want to.

[garyrc]

So, you mean you couldn’t sit far enough back from the front

wall; you were worried that the direct sound coming from the K-horns would be behind

you?

When one of the two short walls is the

"front" wall (i.e., has the Belle in the middle of it, with the Khorns

flanking) we can sit far enough away, and that's the way we have it set

up. When one of the long walls is the "front" wall, we were

concerned that there might have been perceptual holes between the Belle

and the Khorns. Upon experimentation, we found that from the one and

only (see Artto's post, just above), center, perfect, sweet seat there

wasn't a problem with the Khorns on the long wall, with the disks we

tried. The Khorn tweeters were pointed right at us as seen from that seat. But, we wanted to accommodate five of the narrowest possible

couch seats across (it took a long time to find them), with the

possibility of all five listeners being critical ones, so we put the array on the short wall. We decided

against the option of two rows of seats, as seen in many home theaters, because of the considerable difference in sound (SPL, bass, image and highs) we found in the two rows.

With five narrow seat cushions across, the center seat is still the

best, but not quite as good as it was in the other room orientation, the

next two cushions on either side of the center are pretty good, with a

little displacement, but the center holds, as they say, and the outside

two seats are adequate. For music listening, the image seems more

touchy than with a movie. When we put a movie on, the imaging seems

fine, and movies made from about the mid nineties on sound terrific --

even the goofy ones. They seem to be made with more care, i.e., better

recordings than on many of our music disks, especially the classical and jazz we love. I hope this is a coincidence, and that I'm wrong about

this. Classic movies of the multichannel magnetic era are a different story. For example, both we and the Home Theater reviewer think Lawrence of Arabia has sound (on BD) that is too bright. For movies, and occasionally music, we have Heresy IIs surrounds. They can be used with music SACDs that are 5.0 or 5.1. With a few music recordings the Heresy IIs are used for

ambience with a Lexicon environment processor (attached to the surrounds

only). A very great deal depends on the recording for all of this.

[Cody_Mack]

Thanks again Gary and artto! I have my work cut out for me. On the plus side, we may indeed be building from scratch so I have lots of freedom.

I have to admit, though, that y'all are making me nervous with all that talk of EQ, DSP, delay, Audessy, etc., etc. I am and have been pretty much a 2-channel guy, preferring use of gear with not much more than a tube, a couple of capacitors and resistors, and a volume control. Heck I cringe if my amp has tone controls! Up until now, I have had pretty good success using that gear, but I suppose if I am going to step up to a much larger room and build my system around Khorns or Jubes, I am going to have to get some big-boy gear to go with it?

Rick

[DizRotus]

Art's room is amazing. The space is too often igored or underated in the quest for excellent reproduced sound.

Admittedly far from ideal, but ,in the 70s, I used four 8 ohm Speakerlab SKhorns (factory built, plywood, aluminum 350 & T35), with enclosed backs, wired in parallel for 4 ohm load on a Dynaco ST400, thus 300 watts/channel, in a DJ biz. In large spaces I'd have the channels diagonally, therefore going clockwise from corner to corner, left, right, left & right. You could walk around in the center and get an interesting experience.

Repeatedly people would say it was the best sound system they'd ever heard. As my late father used to say, that's damning with faint praise.

As you can imagine, the acoustics were usually dreadful, from the high ceilings of a gym to the low ceilings of a cafeteria. But fill the space with people and 600 watts of horn loaded sound, and a good time was had by all.

The T35 tweeters and my hearing took a beating. A call to EV would quickly produce replacement diaphragms, EV wasn't able to help with my high frequency hearing loss.

[garyrc]

... I have to admit, though, that y'all are making me nervous with all that talk of EQ, DSP, delay, Audessy, etc., etc. I am and have been pretty much a 2-channel guy, preferring use of gear with not much more than a tube, a couple of capacitors and resistors, and a volume control. Heck I cringe if my amp has tone controls! Up until now, I have had pretty good success using that gear, but I suppose if I am going to step up to a much larger room and build my system around Khorns or Jubes, I am going to have to get some big-boy gear to go with it?

Most AV preamps, AVRs, etc have "bypass" to take tone controls, Audyssey, etc., out of the circuit. Some have "pure." I know "pure" is not as pure as the proverbial "straight wire with gain," but it's pretty pure. After you apply processing galore, you can switch back and forth between "bypass" and your selected processing, and determine which option you like the best. I was surprised that the one I usually like best is "Audyssey Flat" (makes the frequency response about as flat as possible using the mystical "fuzzy logic" -- supposedly a good thing -- combination of the response at 8 microphone positions). For a few CDs that have too much above about 8k .... or too much distorted garbage above about 8K ... I like regular Audyssey (as opposed to Audyssey Flat), which incorporates about a 2 dB cut at 10K, and maybe a 6 dB cut at about 20K. This conforms to many theater reference curves, adjusted to a smaller room. But, to me, it cuts too much of the shimmering high frequency response with a good disk, but it can be useful with the bad ones. For a few once beautiful movies of the '50s,60s, & 70s that were put on disk from the original, pre-mix, sound elements without restoring the filmmakers' final (primarily bass) EQ in the new mix by the disk people, I try Audyssey Dynamic EQ (not to be confused with the traitorous "Dynamic Volume") --- but with good disks, it sounds pretty terrible. It was intended to provide something like a sophisticated, Hi Tech, 21st Century loudness control for people who play their movies well below reference SPL, but I use it very occasionally to put the bass back in a bass shaved recording as a very last resort. In our rig, Audyssey Flat does not apply a gargantuan amount of EQ, but up to about 7 dB in just the right places. Subjectively, music sounds a lot less "alive" without it, IMO.

If most CDs, SCADs, DVDs and Blu-rays were made with tender loving care, I would probably prefer a "straight wire with gain." But they're not! Now that I have the choice, I find that Audyssey Flat, plus the occasional use of tone controls, improves most recordings in my room.

[artto]

A recent shot of the equipment racks & seating.

[seti]

A recent shot of the equipment racks & seating.

I dig the luxman's I'm running IBSlammin's MQ60.

[CECAA850]

Still have the K-horns in there?

[artto]

The acoustical saga that keeps going, and going, and going……………………………

 

As some of you already know, “artto’s klipschorn room” is not a “klipschorn room” anymore. I still have my beloved Khorns and Belle Klipsch but they are on the other side of the lower level of my house doing duty in the area with the HO model railroad. I must admit, it’s really nice to have some good sound over there. And if I need any life-like train or locomotive sound effects, they are certainly up to the task. LOL. Regardless, I think this particular exercise has benefits that should be shared.

 

I’m now using a pair of Danley SH50 as the main speakers in this room along with four Epik Empire subwoofers. Two are in the rear corners, and the other two are doing double duty serving as pedestals for the SH50.

 

THE PROBLEM

 

To paraphrase a Klipsch slogan, it’s called “pissing off the neighbors”. I don’t mind it, really. But then they complain (or call the cops) and end up disturbing my listening experience. And that in turn pisses me off.

 

These are suburban single family homes. The side yards between the houses are about 20 feet, which is the wavelength of about 55Hz, half the wavelength of 28Hz and getting near quarter wavelength of 16Hz, all of which make for nice resonant points between my and my neighbors house.

 

I also discovered that the low frequency sound pressure in the room was actually making the outside exterior wall act like a passive radiator, sort of a huge subwoofer. Outside the sound pressure level is as much as 10dB or more higher measured at the center of the wall than at the room corners. And interestingly, the most offensive frequency coming through the wall is 55Hz, the wavelength of the distance between my and my neighbor’s house. The wall was obviously moving. Opening the room door/hall doors to relieve room sound pressure helped a little bit but there was clearly still a wall resonance problem.

 

THE SOLUTION

 

Today there are many new products that weren’t available when I built the room in the early 80’s. One of them is Green Glue Compound. It’s not really glue. And it’s just barely green. There is also its companion product Green Glue Sealant. These are visoelastic “constrained damping layer” compounds for noise and vibration control.

 

There are basically four techniques for effective control of noise and vibration: 1) absorption, 2) barriers/enclosures, 3) vibration isolation and 4) structural damping.

 

If you’ve read my previous posts on this thread from the beginning you know I’ve implemented all of these in one form or another in various applications. In this particular problem, it is structural damping of the exterior wall facing my neighbor’s house that is the weak link. Considering that the original wall is multi-layered, essentially triple-wall construction one would not think it to be a problem. I certainly didn’t. But today we’ve learned that type of wall construction, referred to as triple-leaf cavity wall, is actually the wrong way to reduce sound transmission ~ at least at low frequencies it’s the wrong approach. It in fact does work very well at reducing sound transmission, but only at frequencies well above the cavity resonance. The air space(s) help decouple the wall at high frequencies, but have a negative effect around the resonant frequencies, and can actually make low frequency performance worse. To attain good low frequency performance the resonance must be as low in frequency as possible. In order to do this you must 1) add mass to one or both sides of the wall, 2) increase the depth of the air cavity (not an option here) 3) Add insulation if there isn’t any (no longer an option in my situation).

 

So, while a triple or quadruple leaf wall seems like a logical approach to reduce sound transmission, what it is actually doing is driving the wall/cavity resonance higher – exactly what we don’t want if low frequency sound transmission loss is the goal.

 

Since discovering how much louder the SPL was outside at the center of the wall I decided the first thing that needed to be done was to add more mass and improve its structural rigidity and structural damping. Yesterday we had plywood. Today we have orientated strand board (OSB) which is denser and heavier than dimensionally equivalent plywood, and less expensive, and has no knot hole cavities. And it’s also a “green” product.

 

A damping treatment consists of material or combination of materials applied to a component to increase its ability to dissipate mechanical energy. Its most useful when applied to a structure that is forced to vibrate at or near its resonant frequency. All materials exhibit some amount of damping. However some materials, even though being structurally strong and rigid such as steel have so little internal damping their resonant behavior can make them act as effective radiators, especially at higher frequencies (also what we don’t want here). But by bringing stiff, rigid materials that have good natural internal damping into intimate contact with a “dynamically stiff” visioelastic constrained damping material it is possible to control these resonances. We can kill two birds with one stone so to speak. The resonances are reduced or eliminated and structural strength/rigidity increased by a combination of increased mass (lowering resonant frequencies) in concert with constrained damping material between layers to dissipate energy via shear deformation in the damping layer(s).

 

I decided I would build up multiple layers of 19/32” OSB over the existing wall with Green Glue applied between each layer. Since the interior walls are already multi-layered Celotex and Sheetrock I had to use 4” course threaded drywall screws to securely fasten the initial OSB layer to the load bearing outside wall studs. After the initial OSB layer I could then overlap the previous OSB layers with more OSB securing them to the previous layers with increasingly shorter screws. The third OSB layer would have screws going through all three OSB layers and into the former Sheetrock interior wall). All joints and seams will have Green Glue Sealant applied. All countersunk screw holes would be filled with Green Glue Sealant. At the corner for the adjacent outside wall I would overlap each layer so that the corners form sort of a finger joint so that there is no single butt joint with all layers butting up against the layers on the other wall.

 

Below are some pictures of the initial OSB/Green Glue installation along with SPL measurements taken inside and outside before installation. Green Glue has a curing period and takes about 30 days to reach peak performance so I won’t be doing any detailed measurements to confirm sound transmission loss until then. Initial subjective listening tests and using a hand-held Radio Shack SPL meter seem to indicate at least a -10dB improvement with the initial three layers of OSB/Green Glue. Bass heavy music with peaks of +107dB in the room measured -76dB or less outside and quite honestly I think much of that was simply ambient outside noise (AC, wind, street traffic, etc).

 

This will be a continuing project for a while so be sure to check back for updates on the low frequency sound transmission loss progress as each additional layer is applied. I anticipate a total of as many as nine layers of OSB plus the final layer of sheetrock. I checked with the Green Glue company as to what kind of SPL loss I could achieve with this type of construction but they said they don’t know of any installations with this many layers and this much mass in a single wall. Apparently I will be going into uncharted territory. Of course if I discover little if any performance increases after reaching a point of diminishing returns that’s where it will stop.

 

J

Edited June 25, 2015 by artto

[jacksonbart]

Please post some recent photos of your HO layout.  I have been limited to Trainz12.  Please!

[CECAA850]

Built like a bomb shelter it seems.  Pics will be interesting to see.

[artto]

I thought it might be of interest to see how the exterior walls were "sort of" constructed. I don't have pictures of the original construction but a couple years ago following a hale storm that caused damage to the aluminum siding I decided to have the two windows on the wall that faces my neighbor's house removed since this was the weakest link in sound transmission loss.

 

With the windows removed and a 2x4 stud in place I filled the space with Roxul 80 mineral wool insulation. In this first pic you can see the multiple layers of Celotex rigid insulation built up with 1x2 lath and lastly 5/8" sheetrock. Silicone caulk was applied to the wall studs and each layer of Celotex, 1x2, sheetrock. This is what is called a triple leaf cavity wall. It was pretty much standard practice in the early 80's and prior as "good to excellent" sound transmission loss. However, ironically, it's actually the worse thing you can do to reduce low frequency sound transmission. It works great at middle and high frequencies. So now the challenge is to improve the low frequency sound transmission loss and hopefully have the best of both worlds.

Edited June 27, 2015 by artto

[artto]

Here you can see the 2x4 stud that was installed were the window used to be. You can also see the air space between the two layers of Celotex.

[artto]

Green Glue applied to the 2x4 stud. I later found out that this is not necessary. It will not improve measurable performance. Green Glue is a constrained damping material and as such must be constrained between two large rigid surface areas of building material such as plywood, OSB or sheetrock. 5/8" thickness is recommended. 1/2" recommended minimum.

[artto]

Green Glue Sealant applied to edges where Celotex & sheetrock will be installed to create an air-tight joint. Leaking air is like a water leak in a fish tank. Where there is a leak water will get out. Where there is a crack, gap, or any air leakage sound will leak through.

[artto]

Green Glue Sealant applied over the Celotex and screw holes - over where the 2x4 stud is located.

[artto]

1x2 lath installed for the second layer of Celotex. Green Glue Sealant under all lath. All I'm doing here is simply re-creating the existing as-built wall in the removed window(s) cavity, the only difference being the use of Roxul 80 as opposed to R-11 fiberglass insulation. If I were building this room today I would have removed the R-11 and replaced it with Roxul 80 or had the house built that way.

[artto]

Here Green Glue is applied to the final layer of Celotex before installation of the final layer of 5/8" sheetrock. As mentioned above there is supposedly negligible performance improvement using Green Glue with porous building materials and soundboard is not considered rigid enough.

[artto]

With the 5/8" sheetrock installed and the wall/window cavity completely repaired Green Glue Sealant is applied to all the edges of where the 5/8" (19/32" actually) Orientated Strand Board will be installed.