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First reflections with corner placement question.


Ray_pierrewit

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Just a couple of quick questions. I've almost completed my new listening room/artist's studio, 16'w x 26'l x 10'h. It was built using SIPs, 1/2" OSB on the outside , 4" of insulating foam and 1/2" plywood inside and on the ceiling. I'm now ready for some room treatment, namely for the echo. The room is amazingly air-tight.

 

I've decided to try corner placement, on the short wall, for my Lascala (after having read the PWK 8 cardinal points) and initial listening impressions tell me I love it. The image is rock solid and very wide, the added bass reinforcement is welcome as well, I've also done the port mod.

 

Now, I'd like to address the first reflection points, how is this done with a 45 degree angle in the corners?

 

Also, I'll likely make some polycylindrical diffusers, as I've seen in the Dope from Hope. I won't be able to put in as many as Artto (I believe his name is), but will concentrate them in the upper portion of the room. Does anyone have experience using coroplast rather that masonite? It's lightweight, bendable, yet gets really taught and stiff when curved. Also, my tests tell me it doesn't resonate like wood does, tapping it when taught gives a type of dull thud. 

 

** Edit: I've just looked at a bundle of room pics with Khorns and it doesn't seem people treat the reflection points at all??!

 

Thanks for any advice!

Daniel

 

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The reason you don't see K-horn setups with sidewall treatments is that placing a K-horn (or a LaScala, for that matter) in a corner with proper toe-in spills relatively little energy beyond the outside walls of the MF and HF horns. Typical direct-radiator speakers need 1st-reflection treatment because compared to a well-designed horn they spray sound all over the place (even if placed in corners with proper toe-in, although that would considerably reduce reflections created by the spillage).

 

Diffusion at at the 1st-reflection points will almost always sound more natural than absorption. If the 1st-reflection points are really causing problems in your setup, you can begin by placing something portable with an irregular surface (a small bookcase would be ideal) at the first reflection point, which would act as a diffuser. The reason I recommend starting with something portable is that you may very well find that you prefer the sound without the treatment. If the treatment does make things better, you can replace the bookcase or other temporary doohickey with a purpose-built diffuser, for which a Google search will reveal tons of options.

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8 hours ago, Ray_pierrewit said:

Now, I'd like to address the first reflection points, how is this done with a 45 degree angle in the corners?

You probably know this, but some don't. Angle of reflection equals the angle of incidence.  And it is the same with all waves. angle_of_reflection_3b.png.6fa2948ee0bd8d7ec4b619621ec3075c.png

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45 minutes ago, hsosdrummer said:

The reason you don't see K-horn setups with sidewall treatments is that placing a K-horn (or a LaScala, for that matter) in a corner with proper toe-in spills relatively little energy beyond the outside walls of the MF and HF horns.

 

This is what I thought. Inasmuch as the current sound is concerned, well, it sounds a little cavernous which is why I'm thinking of those Polycylindrical diffusers. I read of many accounts where they all but eliminate echo in rooms such as mine. Does anyone have any opinions on using coroplast rather than the typical 1/8" masonite? As I mentioned, I had some pieces lying around and temporarily tried to curve them into a Poly. They become much more rigid than I anticipated and look really cool to boot.

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See Chris A's post on this forum on "Corner Horn Imaging."

 

Chris A

The is the third in a series of FAQs ("Frequently-Asked Questions") , the first of which was the Klipsch serial number FAQ, and the second is the Active Bi-amping/Triamping FAQ. This thread discusses corner-horn loudspeaker imaging, in particular, how to achieve outstanding imaging, and typically encountered issues with corner horn imaging.

 

Klipsch currently makes two corner-horn designs (i.e., the Klipschorn and the Klipschorn Jubilee), and has made smaller corner-horn speakers in the past (e.g., the Shorthorn series). Other manufacturers make or have made corner horn speakers (e.g., Voight, ElectroVoice, JBL, and smaller companies like Pi and Decware, etc.).

 

"Can I get Outstanding Imaging from a Corner-Horn Speaker?"

 

Yes. Good corner-horn imaging can be "unsurpassed".

 

"What are the Advantages of Corner Horns?"

 

A corner horn is designed to be used in a corner of a room or outside structure (such as an outdoor stage backstop). While this type of speaker is not new, it is not often seen in today's audiophile circles. Many misconceptions about corner horn potential performance and proper setup exist:

 

1) They provide dramatically lower bass distortion, in particular, modulation distortion, than non-corner-loaded loudspeakers(Part I and Part II). Bass modulation distortion has been found to be quite audible.

 

2) They provide much greater low frequency dynamic range without resultant woofer compression or other forms of distortion, which limits achievable sound reproduction fidelity of other types of speakers

 

3) They have the potential to achieve full range controlled directivity in-room if designed/produced carefully

 

"What are the Disadvantages of Corner Horns?"

 

1) They require good room corners to fully achieve their lf response, or a large footprint in order to accommodate "false corners"

 

2) They are physically large and heavy speakers if they are to reproduce all needed low frequencies (e.g., piano, organ, string bass, etc.)

 

3) They require amplifiers of high quality for the critical "first watt" of input power to achieve full potential

 

4) They require careful placement of objects and/or acoustic treatments in-room in order achieve their full imaging potential

 

"What is Different About Corner-Horn Imaging?"

 

Corner-horn imaging performance is a strong function of the room they're in, i.e.,

 

1) The room's absolute and relative dimensions, its shape (including the ceiling), and the uniformity of the walls next to the Khorns (i.e., front and side walls near the speakers)

 

2) The placement of the speakers within that room on the boundary (e.g., tailpiece-to-corner fit to seal the two mouths of the bass bins, the length of the corner extensions from the bass bin on front and side walls, and whether there are any intrusions into the room by bricks and other architectural details (yes, brick fireplaces and mantles can significantly affect imaging...)

 

3) The absence of near-field furniture or equipment that reflect acoustic energy, and

 

4) The judicious use of acoustic treatments (...it usually doesn't take very much, but it usually takes some).

 

5) The quality of the "first watt" of amplifier power driving them

 

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Chris A

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"How Do I Set Up Corner Horns to Increase Their Stereo Imaging Performance?"

 

One commonly heard complaint from corner horn users is that their speakers seem to have trouble achieving the same imaging performance as free-standing speakers. Example cases of this include the Khorn vs. the La Scala or Belle, Cornwall, Palladium or Klipsch Reference series, etc. When La Scala or Belle owners would profit in greatly increased bass performance and much lower bass IMD of their speakers if they were placed in the corners of the room, toed-in to the listening position. When these same owners are polled about where they place their speakers in-room, invariably the answer is either "along a wall" or "a few feet from the front and side walls". Why would this occur? PWK himself stated:

 

"The conclusion is pretty obvious. Whether you are using KLIPSCHORN loudspeakers, or speakers of some other make or type, you will get best stereo geometry and best tonality with corner placement of the flanking speakers (whether you use a center speaker or not). and the corner placement should be with the flanking speakers toed-in at 45 degrees." (Taken from Dope from Hope, Vol. 15, No.2, 01 August, 1975)

 

There is something involving room acoustics and corner horns that is critically important to achieving excellent corner-horn imaging. It turns out, the psychoacoustic effect that comes into play in this is a special case of the Precedence Effect of listeners, called the Haas Effect, and the issue is early reflections of high mid-bass and midrange frequencies (i.e., about 250-4000 Hz) off the walls of the room closest to corner-horn midrange and high mid-bass horns.

 

Here is a correspondence from the co-inventor of the Klipschorn Jubilee (Roy Delgado):

 

"Imaging and creating it by having two varying acoustic signals is an interesting undertaking. I have found that a smooth, unobtrusive boundary between the two speakers works very well with well-behaved and consistent polar patterns [of speakers]. The other thing that I have noticed that works well is no boundaries--like playing the speakers outside. Both do a very good to excellent job of accomplishing the imaging goal, but the caveat is that no boundaries forgives non-consistent polar patterns while a smooth boundary is a strict enforcer of consistent polar patterns. Pretty cool how that happens."

 

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These early reflections should be controlled (i.e., a "Zero Reflection Zone" that one acoustic panel manufacturer uses) in order to achieve much greater imaging performance with speakers in corners of rooms (especially corner horns). What is the easiest way to control these reflections? Have a smooth boundary between the speakers (i.e., nothing between the speakers) and smooth front and side walls.

 

If this is not possible for your room and setup, the next easiest fix is to employ absorption panels. Many companies make "fuzz" panels and tiles that can easily be placed along side walls and front walls of the your listening room. How much? It turns out (from the Haas Effect) that controlling the early reflections should be done for about 10-20 milliseconds of delayed reflections from side and front walls. This translates into about 11 to 22 feet (3.4-6.8 meters) of total path length at room temperature.

 

One way to determine how much absorption you need about the midrange horn mouth area on the front and side walls is to draw a plan view of your room (i.e., looking down on the floor plan), and draw circles from your listening position in increments of 12, 14, 16, 18, and 20 feet (4.9, 5.5, 6.1 meters). Then draw circles of 2, 4, 6, 8, etc. feet (0.6, 1.2, 1.8, etc. meters) from your midrange horn mouth locations in-room. Where the circles intersect along the walls with total path length of less than 11-22 feet (3.4-6.8 meters), mark those areas with a highlighter, then go open a bottle of wine with your spouse. Wait until the wine takes effect, then start the negotiations on how much absorbent tiles/panels are acceptable (...hopefully, the answer isn't "zero"...). I use about 2 feet (0.6 meters) of absorption at the side-wall exit area of my corner-horn midrange horns: YMMV.

 

Depending on your room geometry and listening position in relation to the corner horn placement (i.e., the included angle of the speakers relative to the listener--typically 90+ degrees included angle), the width of the midrange horn acoustic coverage laterally (~60-100 degrees included angle), and assuming that your corner horn midrange horn controls its polar response down to its lower crossover frequency*, the area that you should cover with absorption panels could be on the order of 2-10 feet along the front and side walls. I find that 2 feet of absorption along side walls works very well for Klipsch K-402 horns (i.e. Jubilee), and ~7 feet across the front wall, measured from the exit of each midrange horn's mouth.

 

Another approach is to place diffuser panels along the same areas, but note that the use of diffusers in the "Hass effect areas" will likely not achieve the same level of corner-horn imaging as the use of absorbers. More on the reasons why later.

 

If your listening position is more than 11 to 22 feet (3.4-6.8 meters) away, you probably have little work to do. If you are like me, and sit within 10 feet (3 meters) of your corner horns, you will find that the effect of using absorbent panels along the walls is spectacular in increasing your stereo imaging performance.

 

* More on the subject of horn polar control and imaging performance later.

 

"But What About the Equipment/Racks, Architectural Details, and Speaker(s) Between by Corner Horns?"

 

Again, the most straightforward way to deal with this is to simply remove all objects between the speakers, leaving smooth wall. If this is not achievable, the alternatives are the same as above. I use absorption tiles on the side and top of my center Belle, on the masonry on each side of my fireplace, and a quilt-based cloth fabric on the mantlepiece to control these early reflections.

 

"But What About the Television Between My Speakers?"

 

This one is easy: place a temporary quilt, comforter, or acoustic absorption tiles in front of the screen when you listen in stereo music-only (i.e., no video) mode.

 

"But What About the Floor Next to My Speakers?"

 

Something as simple as a thin area carpet around each corner horn or even wall-to-wall carpet will suffice. This carpet does not need to be very thick or "fuzzy".

 

"But What About the Ceiling?"

 

If your ceiling is relatively high, you probably don't have a problem. If it is lower than about 9 feet, and especially if you have Khorns, you should think about either putting absorbent material around the top/bottom mouth of the K-400 midrange horn or place diffusers/absorbers on the ceiling around your speaker's midrange horn mouth (especially if you sit relatively close to your corner horns). More on the reason for this later.

 

"What If the Amount of Absorption Recommended Above Just About Covers My (Small) Listening Room?"

 

Then you are probably one of those unfortunate corner-horn owners that would greatly benefit by placing your speakers in the corners of a larger room: this is a large portion of the argument, "...Khorns require a large room...". If you are using Klipschorn Jubilees, then you can use them in a smaller room than Khorns. More on the reason why this is--later.

 

"Is All This Really Necessary?"

 

If you are trying to increase your corner-horn imaging performance: the answer is "yes" if you sit within 15 feet (4.5 meters) or so of your speakers. If you sit further back, then you probably don't have many imaging issues.

 

Next up: discussion about amplifiers and corner horns...

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Start with carpet and furniture.  Use heavy insulated curtains on the windows and see what you get.  Work up from that.  Persian rugs on a wall can do an amazing job of killing and absorbing reflections, esp when spaced off the wall a touch.  Can be higher in WAF than many wall treatments, too.  

 

Look into these sorts of wall treatments, too.

https://www.parts-express.com/cat/acoustic-foam-wall-treatments/1907

 

 

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The primary reflection point can be determined by sitting in the listening position and having someone holding a mirror, sliding it against the wall on each side of the speaker's top hat. When you can see the front grille of the top hat in the mirror that is the location for absorption. Use diffusion toward the rear of the room.

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On 10/19/2018 at 5:11 AM, Khornukopia said:

 

Coroplast corrugated plastic sheeting is much lighter, so your curved panels will be easier to hang on the wall. 

 

Yes, that's exactly it. Is there any reason it shouldn't work? Like I mentioned, they will likely be placed in the upper portion of the room to reduce echo. Coroplast is easy to cut with a straight edge and xacto knife, it bends easily and gets nice and rigid when bent the proper way.

 

Thanks for the extensive message garyrc (and Chris A)! Just the type of info I was looking for. Lots of things in there that compel me, lots of things I've already done (smooth walls between speakers, 45 degree corner flanking... 

 

Being an artist's studio there isn't much carpet nor furnishing to be placed. I do have a Persian rug in front of the speakers though, that's a given.

 

I was listening to music the other night and decided to try my decibel meter (iPad app). It wasn't uncommon for me, in my previous setup, to listen to music with peaks above 95db. In the new space it seems a comfortable level is more around 87db peak. It may be because the echo is causing a little discomfort as I raise the volume, or perhaps it's the ultra low noise floor by being a totally independent structure without anything else generating noise. Having said that though, 87db seems very loud in here.

 

I will get this room treated in the next few weeks and gladly post my pictures/impressions.

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On ‎10‎/‎24‎/‎2018 at 8:13 AM, Ray_pierrewit said:

Being an artist's studio...

 

 … and gladly post my pictures/impressions.

 

Look forward to seeing pictures of your speakers and studio. You have got me wondering if I would use dado slotted wood, or extruded aluminum channel to mount some

Coroplast in my place, if your listening test results are good. I am curious about your aesthetic plan to mount or retain the ends of your curved, tensioned Coroplast panels. 

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