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Klipschorns and ASC tube traps


wpines

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For 2 channel listening. I currently have 7 ft x 16" ASC tube traps in the front 2 corners(a 3ft stacked on a4 ft), with Belles. If I got Klipschorns, where would the tube traps go? There are no suitable back corners because in the back wall there is a door at each corner.

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Hi wpines. What did you pay for these if I may ask. As you know I have 8 ASC tube traps I may be selling. I put them tight against the KH's when I had them. Try them on inside then outside and maybe a bit away from the KH's.

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I paid $450 for 2-4'x16" ASC tube traps, 2-3'x16" ASC tube traps, 2-2'x4' Panels and 1-2'x6' panel. The improvement in the room is remarkable. I'm buying 88 Klipschorns. Your advise to put it in front of the horn is probably good advice. Maybe a 3 ft in front and a 4 ft on top in the corner?

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For 2 channel listening. I currently have 7 ft x 16" ASC tube traps in the front 2 corners(a 3ft stacked on a4 ft), with Belles. If I got Klipschorns, where would the tube traps go? There are no suitable back corners because in the back wall there is a door at each corner.

Treatments are different in my room now versus when I took this picture but here is one option for Traps Placement.

mike tn[:)]

post-14473-13819334442968_thumb.jpg

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The prime spots are in the two rear corners standing vertically, as well as in the front two corners standing vertically above the speakers.

Additionally, you can add then in the rear wall/ceiling intersection adjoining the upper corner as well as in the front.

Just be aware that many tube traps are tuned.

A cheaper most effective trap is made of 2x4 ft sheets of 4" 705 Owens Corning semi-rigid fiberglass insulation cut into 4 identical triangles (cut each 2x4' sheet in half into 2 - 2x2' squares, and then diagonally bisect each piece) and stacked in the vertical corners (above the corner speakers in the front). Each full 8' tall corner will require 6 - 2'x4'x4" sheets and each 4' half corner will require 3 sheets (and likewise a 2' quarter corner would require 1.5 sheets). These traps can then be framed in various ways - the easiest being the use of triangular molding strips attached to the wall on either side of the fiberglass, covered with stretched and stapled unbleached or dyed muslin or burlap. Fancier Guilford of Maine acoustic material in various colors is available for ~ $20 a yard.

In addition to these bass traps, the ceiling/wall intersection in the back and sides can be utilized by making a triangular tube of 705 Owens Corning SR fiberglass - with 1 foot wide lengths of the material attached to the ceiling and wall running along the intersection. A third piece is then mounted in a covered frame across he front forming the hypotenuse and enclosing the 'tube'. And alternative suspension method is to employ triangular mounting trim strips and to hold the fiberglass in place by intervals of piano wire stretched from one trim piece to another, with material stretched from trim piece to trim piece.

Still another cheaper and slightly less efficient alternative to the above 'tube' method, is to build an external .5"x 4" frame around a 1.5' by 4-8' long 4" thick 705 Owens Corning SR material covered with stretched material. This panel is mounted diagonally across the wall/ceiling intersection effectively forming the hypotenuse of the corner. If you like, a slightly narrower strip of fiberglass can be mounted behind the first increasing their total thickness, efficiency, and lowering the effective tuned frequency.

In addition to the above, tuned membrane or slotted Helmholtz resonators can also then be used to address anomalies that have not been adequately addressed, and are placed next to the rear corner traps on the vertical walls as needed.

Also, before buying pre-made tube traps, you should consider making them from Sonotube for a fraction of the price. With measurements, you can more accurately and appropriately tune them (narrowly - more effective, or broadly - less effective) to address the actual problem. These will effectively address low frequency standing waves. But tuning and placement are critical for them to be effective.

For anomalies above 300 Hz, please do not make the mistake of thinking that absorption does the same job as diffusion! It does NOT. Absorption moves you closer to anechoic. Diffusion moves you closer to a large space. And generally speaking, you only want to use absorption only for the 1st order early reflections that directly impact the 'sweet/listening' spot. Everything else is diffused.

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On the Stereophile site you can get their first 3 test cd's for $24 and an analog SPL meter from Radio Shack for $44.. This is where I am now, waiting for the Cd's to arrive. Google on stereophile test CD 2 and look at the stereophile site. Don't know if I will learn what I need to know to get the room tuned but I'll have an interesting time trying. There is a lot of good info on the Real Traps site as Colin mentioned. Mike has an 11' tube where I was saying for his Klipschorn in the pic above.

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I desperately needed absorption to start out with but now, how do I find out what my room mode issues are. Is there a beginners setup that includes all of the neccesary materials and is layperson oriented?

This post scares me. [:P] (BTW, I am not picking on you! I am simply using this as a spring board for a more common and pervasive general attitude!) Rather I am addressing 'all of you'.

I will tell you why...

Absorption for what?

Unfortunately people do not know what modes are of interest which DO need absorption and instead everyone goes for magical foam (and folks, of all the available materials, foam is the least effective!), magical wall coverings, and Spiderman beach towels to control the out of control reflections which they have heard are causing so many problems.

We seem to have gotten far enough that people acknowledge that SOMETHING in the room is wrong. Which is great. But now we are grasping for straws. EXPENSIVE straws. And unfortunately we seem to have gotten only as far as "absorption".

Please STOP!! This is the path of disaster! You can add 1000 ridiculously priced absorbers (and isn't it fascinating just how most sites only have fancy absorbers?) and after all is said and done, and the big bucks have been spent, all you will have is a very small sounding dead room.

I suspect the problem is that you do not have a plan. You have heard that you "need absorption", and off we go searching for solutions without a plan as to exactly what you need to absorb (and also what you most definitely do NOT need to absorb!) Absorption is absorption is absorption!

You ONLY** need absorption in '2' 'places'.

The first place is for room modes below 300 Hz. The process I mentioned above will address 90% of them without measurements. For the rest you need measurements and tools in the form of specialized Helmholtz resonators..

The second place is to address the first order reflections involved in establishing the Initial Signal Delay Gap. These are a very limited set of reflections and they require surgical treatment - NOT broad wall covering 'let's catch them all' absorption!

The rest of the room requires DIFFUSION. Not simple scattering and redirection of specular reflections as was the common practice with curved poly cylinders that were effectively replaced and supplanted by quadratics.

What many are systematically building are dead rooms. And while dead is a bit more intelligible, it is not a nice room. A dead room is what probably has Paris Hilton going crazy! OK, maybe her problems are just a bit too large to blame on absorption, but I suspect that it may be a small part of it! ;-) Dead rooms are fatiguing and, well, down right uncomfortable.

Instead, the goal is to redistribute the energy in a controlled manner that conveys 'space' - a way to make a small room seem LARGE. A small acoustical space lacks a true reverberant field, and our goal is to try to simulate one! {And why do I now fear someone suggesting using some fancy expensive box to add what is labeled in the LCD window as 'reverb'!? [:(] }

I wish folks would think that they need DIFFUSION complimented by the use of surgical absorption. ...Not the other way around - as they would do far less damage.

And folks, please quit running to the over priced and under-performing foam sales all over the web![:S] (And I especially like the 'paintable' acoustic foam!)

For the most part, you can build better than you can buy.

But for those who feel you need a $10,000+ turntable or CD player, go for it. If you can hear the difference in those players considering the limitations in the source material, you will love the foam you can buy![:P]

Oh, and folks, test CDs are not sufficient to tune a room. I don't' mean to be a curmudgeon here, but you need the right tools. And test tones and an SPL meter or a fancy multi-band-SPL meter known as an RTA aren't sufficient except for a very limited range of problems, and most of those have to do with equipment, not rooms.

**With very rare exception. {Note: Any absolute is suspect! Including this one!}

OK, bring on the folks with pitchforks and torches! [:D]

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A cheaper most effective trap is made of 2x4 ft sheets of 4" 705

Owens Corning semi-rigid fiberglass insulation cut into 4 identical

triangles (cut each 2x4' sheet in half into 2 - 2x2' squares, and then

diagonally bisect each piece) and stacked in the vertical corners

(above the corner speakers in the front). Each full 8' tall corner will

require 6 - 2'x4'x4" sheets and each 4' half corner will require 3

sheets (and likewise a 2' quarter corner would require 1.5 sheets).

These traps can then be framed in various ways - the easiest being the

use of triangular molding strips attached to the wall on either side of

the fiberglass, covered with stretched and stapled unbleached or dyed

muslin or burlap. Fancier Guilford of Maine acoustic material in

various colors is available for ~ $20 a yard.

Are

these corner traps most effective placed tight into the corners or is

there some benefit to leaving some space (3 to 4 inches) between the

trap itself and the corners?

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Mark, we have several types of diffusion panels in our listening rooms here at Klipsch. I"m sure they are not inexpensive. Plastic 2x2' moulded panels, styro 'city block' mini skyscapers, styro panels of varying thickness embedded in walls, etc.

I'm thinking of putting a 'small' Home Theatre in my basement, concrete floors, block walls (will be framed and drywalled), and plaster ceiling. Sounds HORRID in there right now, and I have several of the 4" wedge foam panel scattered throughout (in no scientific pattern, mind you).

Any ideas for homemade DIFFUSION panels? Can Doc's measurement rig determine where the problematic frequencies are so that I can tame this room?

Thanks,

Michael

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Michael,

I am assuming that the 'mini skyscrapers' you have are similar to the RPG Skyline http://www.rpginc.com/products/skyline/index.htm .

Also, the various sources that supply the RPG Hemifusor style http://www.rpginc.com/products/hemiffusor/index.htm (aka Space Array by pArtScience, distributed by Auralex) are also excellent.

Additionally. the classic Diffractal and the QRD, the quadratic residue diffusor - the first of Manfred Schroeder's babies, are also excellent diffusors.

This is going to sound a bit counter-intuitive, but you don't really have to worry about the problematic frequencies above 300Hz (above the frequency dependent LF standing waves/modes.)

In other words, after the low frequency (<300 Hz) standing waves/modes are addressed, and an Initial Signal Delay Gap is defined by taming the first order early arriving reflection, what you are going to do is to use diffusion to diffuse the rest of the acoustic energy back into the room in a controlled well behaved manner.

This controlled well behaved manner consists of breaking up the specular (focused) reflections (that are not the 1st order early reflections impacting the ISD gap), into a 'random' diffuse sound field that decays in intensity with time. In a small room you are going to have a more difficult time creating a long, well-behaved decay simply because there is a finite amount of energy and not enough space for the reflections to become truly statistically diffuse - hence why we do not have a true diffuse reverberant sound field. We desire to both create and shape the behavior of a semi-reverberant sound field.

In doing so we want to leave the high frequencies alone. The reason for this is that they are not overly abundant (the energy is finite) and they are of such small wavelengths that they are very easily absorbed, and little is left to diffuse. So, you might say that we generally don't worry about them except to say that we want to diffuse what is there. Our concern is primarily in the low mids and mids, where the reflections are still focused and and of sufficient gain to be audible. But having said that, we are most concerned with the acoustic energy and how it arrives in the time domain.

So, what are we concerned with if not frequency of the low mid and mid frequency reflections. We are concerned with time and intensity (gain).

If you look at the enclosed diagram of a room ETC measurement; After the ISD gap is concluded (and the reflections at issue in this time interval 'surgically' absorbed), we want to create/increase the degree of semi-diffuse sound field to and to shape it to decrease exponentially in a smooth, distributed manner (to the greatest degree possible).

Thus the goal is to reduce the gain (intensity) of the audible focused/specular reflections and to spread this focused energy out over time - in other words, to diffuse it. We are trying to remove the defined highly focused reflections of significant intensity through diffusive treatments. And the greater the number of the incident reflections that occur and with the diffusive 'spread' that a proper surface imparts, additional diffusion occurs, and subsequently the intensity of each reflection is reduced and the diffusion increases.

Take a look at the ETCs and see if they do not make what is going on a little more intuitive.

Note, in one ETC I have labeled the ISD and also indicated that this is the region that corresponds to the RFZ (Reflection Free Zone) that so many hear about in so many places.Just understand that the concept of the RFZ has no tailing semi-reverberant field as this diagram illustrates.

post-23237-138193347326_thumb.png

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