The backwave is dead.Long live the back wave.

[Ztatic]

Gigantic point source?

Thanks, George. Perhaps more accurately than saying KLH Nines are point sources, especially considering their size, I should say, they operate not as line arrays. I did not want to seem as contentious as I really am by putting it that way, in view of a statement I noticed somewhere that ESL's are all line sources, but what I said instead about the Nine in particular was not exactly true. I shall try to put this to rest by simply describing the KLH Nine as briefly as I can.

The KLH Nine is a two-way speaker. The crossover is at about 800 Hz.

Shown in your posting is one of the woofer panels. There are ten of these in each speaker, creating a 24" x 66" woofer array that does not have a high enough aspect ratio to operate as a line source.

There is also a single tweeter to one side, with its center 44" above the floor (photo of tweeter attached with a U.S. nickel coin as a size reference). The tweeter's radiating area measures about 4" x 4", which is relatively large, so its sound is rather directional, but still, I think it can be said to operate as a point source.

Put together, in the very near field, the Nine can be considered a plane source, and in the very far field, a "point" source, albeit a large one. In-room, one is generally situated in the mid-field, and when the speakers are aimed as intended, and not at the listening position, the sound is distributed by room boundaries in such a way that that the listener experiences an unusual combination of plane, point, and diffuse sources. The effect is interesting, engaging and much like live.

 

[kach22i]

Listening to KLH Nines is now on my "bucket list".

 

[Ztatic]

Architects are designers

Listening to KLH Nines is now on my "bucket list".

You know, George, seeing as how you are an architect, I should have mentioned that the KLN Nine's I.D. was done by an architect named William H. Barton, a close friend of my father, now retired and living in Concord, MA. He was also responsible for the original KLH Eight table radio design, although the wood was thinned and the corner joints simplified by Henry Kloss for cost reasons before it went into production. Kloss must have really liked the design, based on a look at the modern Tivoli radio.

 

[kach22i]

I.D. was done by an architect named William H. Barton

That is an inspiration to me, as I have a desire to expand my design pallet and get into designing things other than buildings.

I think Rogue Audio also used an architect for the Industrial Design of their equipment. The Sullivan like arch is a dead give away.

http://archidialog.com/tag/mario-botta/

http://www.positive-feedback.com/Issue4/rogueaudio66.htm

Back to backwaves....................

None here.
http://www.scienceclarified.com/A-Al/Acoustics.html

A scientist at Bell Telephone Laboratories in 1965 listening to music in a specially designed room that does not produce echoes or reverberations. (Reproduced by permission of
AT&T Bell Laboratories

Read more: Acoustics - humans, examples, body, used, process, life, type, energy, gas, system, air, parts, waves, change, principle http://www.scienceclarified.com/A-Al/Acoustics.html#ixzz0phmhoNb8

 

[nsgarch]

That is an inspiration to me, as I have a desire to expand my design pallet and get into designing things other than buildings.

Believe it or not, most architects are NOT designers (not a criticism BTW) if by design, one means the solving of physical/technical problems but in an aesthetically attractive way. Like many design architects, I have have been closely involved with creating objects, graphics, logos, advertising collateral, and even audio equipment. George's avatar reminded me that in days long gone (along with the company itself) I designed the logo for M&K speakers for my friends Jonas Miller (M) and Ken Kreisel (K). A time when the learning curve was so steep for everyone in the industry, there was simply no occasion/reason for the bitchiness and shameless, conscienceless hype that infuses audio today.

Which brings me "Back to backwaves......." and puts me in a reflective mood (couldn't find the "Reflective Mood" forum ;--) In the early 70's, Jonas Miller owned one of the first two or three true audio showrooms in LA County (Beverly Hills to be specific) and was the first person on the West Coast to carry (though not exclusively) dipole speakers -- three to be exact -- Quad 57, Magneplanar Tympani, and KLH 9, followed later by Apogee, Martin Logan, and probably a couple other brands I'm forgetting. He also carried Beveridge and Infinity IRS (not technically dipoles IMO.) And interestingly, no JBL's or Altec's, though he came up in radio and pro sound. The interior of the store was vast as I remember -- at least big enough that each of the speakers I mentioned could have their own generous piece of real estate, and one could stand in the middle of the store and turn, like a locomotive on a roundtable, and listen to each system as a separate entity (visually and acoustically) and no one ever worried about the backwave, or acoustical treatments, or anything like that; and yet everything sounded great -- no, make that SPECTACULAR -- to all of us. So riddle me this: have we become insensitive to the miracle of reproduced sound, has the hardware and software (for all its "technical" improvements) become less capable of engaging and stimulating us?; or are we living so fast and so distracted, that it has become impossible for us to truly be still? And without drugs or alcohol,to relax and become fully immersed in the experience? I can still do it, but I have to work at it a bit and prepare. It used to "just happen".

 

[kach22i]

and no one ever worried about the backwave, or acoustical treatments

Could all those large flat panels in the store be acting as absorption (like drywall flex)?

become less capable of engaging and stimulating us?

I just got caught up on a VCR tape recording of the Autoline Detroit PBS TV program. They had executives from the big three and the dean of CCS on the panel. The topic was the future of the automobile and transportation in Mega Cities (which NYC barely qualifies). However what they ended up discussing was the fact that young people today do not crave things/material possessions, they crave experiences. Owning a car for some of these young people is not on their wish list, they would rather travel or share experiences with their friends.

Link to “Elbow Room” video:
http://www.autolinedetroit.tv/autoline/archives.php

My point being that the market for stereo equipment, cars or other consumer goods is changing. Watch the video and see what they say about telephones, the i-phone and other things.

 

[MylesBAstor]

Not sure if this link will work. For those into AR speakers.

http://www.audioevo.org/dan-muzquiz/photos/stuff/photo.html#photoid=1253

 

[bwraudio]

Maintaining ambience

The way I handle the back wave of Martin Logan Summits is to absorb, diffuse and place the speakers well away from the front and side walls. I also disconnect the woofers on the Summits and use Magneplanar Tympani IV bass panels. The Magneplanars dipole radiation matches the Summits electrostatic dipole radiation and between the two, provides great depth and realistic ambience. Placing large ASC tube traps 6' behind the Summits and Magneplanars reduces comb effects and provides diffusion as well. The wall behind these speakers has a total of 12 large bass traps and also directly behind and below is hard wood flooring, which aids ambience. All early reflections have been eliminated, giving one great detail and because of the large distance from all surfaces, a huge soundstage. The remaining reflections are are late in time and add to the overall sound, giving one
great ambience. Buy absorbing all the back wave information, one loses efficiency, kinetic energy, ambience, and a large soundstage.

 

[JonFo]

I belong to the 'kill it' camp.

After extensive measurements and tests, it became clear that the rear wave of dipole electrostats interferes more than helps in terms of a concise, focused soundfield.

So, my room has over 45 commercial sound treatments from RealTraps, plus several custom acoustic treatments to manage the energy in the room.

Then on top of that I overlay Audyssey Pro room correction. The result is a stunningly focused soundfield that resolves multichannel and 2-ch music with scary accuracy.

The room supports the cleanest bass I've personally ever heard. The big Infinite Baffle sub plus the woofers are all well integrated with the room.

 

[karma]

HI All,
Not wanting to "gooble up" the rear wave on my CLS IIA's I opted for another solution for control. Behind each speaker, against the wall, I placed a wide band diffusor. It's dimensions match roughly the the size of the panels.

I had found that putting absorbing material behind the speakers changed the in-room tonal qualities to the point where the sense of acoustical space was reduced and the the overall acoustic became too dark. So, I eliminated the material.

With the diffusors, I could do two things. The uneven surfaces gave effectively a random set of reflection angles and any comb filtering between the speaker and the wall was eliminated. Reflections coming off the diffusors were not only randomized but also had no resonant dimension within the limits of the diffusors natural bandpass. Effectively I had removed the wall as a rear boundary (within limits).

The overall effect was an acoustic that was smoother and the acoustic space appeared larger. It seemed less like a room while maintaining its carefully adjusted tonal balance using more traditional means. That's the beauty of a diffusor. It will not change the frequency response of the room as is caused with sound absorbing materials.

I consider this to be a successful experiment. It looks crazy good too in a high tech sort of way.

Sparky