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O'Shag
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The Awesome KEF 207/2

I've been reading Stereophile for some time, and get the impression that JA is a man of fewer superlatives than average, which I admire. I might be wrong, but could sense in his review of the KEF 207/2, that he was ready to gush, but managed to hold back. The 207/2s are truely wonderful speakers, the second greatest KEF has ever built - and I'm not talking about the Muons.

Perhaps someone can answer a question that has been puzzling me, which is this. It is common practice to toe-in speakers. How does this not affect the imaging? If soundwaves are projected straight from the drivers, and both speakers are positioned drivers facing forward equilaterally from the listening position (this designed to form a solid stereo image with performers accurately positioned across the soundstage, then how is it that toeing-in the speakers does not implode or distort the image to a certain degree?

Elk
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Re: The Awesome KEF 207/2

Toe-in absolutely can affect the image.

Whether this affect is an improvement of a detriment depends on the radiation of sound from the speakers. Some speakers do their best with them pointing straight ahead; others, pointed toward the listener, etc.

Interesting to think about whether and when this is a form of distortion.

dcstep
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Re: The Awesome KEF 207/2


Quote:

Perhaps someone can answer a question that has been puzzling me, which is this. It is common practice to toe-in speakers. How does this not affect the imaging? If soundwaves are projected straight from the drivers, and both speakers are positioned drivers facing forward equilaterally from the listening position (this designed to form a solid stereo image with performers accurately positioned across the soundstage, then how is it that toeing-in the speakers does not implode or distort the image to a certain degree?

Too much toe will collapse the sound stage, as you suggest. Some of the drivers are particularly directional, so that toe helps get the listening position into the sweet spot. Toe also reduces some early boundry reflections, which can muddy the sound and disturb imaging. The rake or tilt of the speakers will also have a very significant impact on the openness of the sound. So lock in a stable image with toe and then open it up with rake.

Dave

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Re: The Awesome KEF 207/2

Great thread and ideas, guys!

As for your comment about JA's reviews, I think your point about the true value of JA's typical understatement is extremely well made. JA doesn't run into the "bestest turntable, ever!" all that often, or the latest monthly permanent reference amplifier in every other review, so when he does write a review like this, its impact is given proper authority.

That speaker would rise right to the top of my audition list if I was shopping and had the budget.

Now, we have trickle down to look forward to!

You do know there is a downside to this. By liking that speaker, JA has just caused a dozen or so audio tantrums that will lead to letters from a few too-tightly-wrapped subscribers cancelling their subscriptions. I hope the magazine survives their loss.

Kudos on one of your highest quality reviews, JA, and that's saying alot.

O'Shag
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Re: The Awesome KEF 207/2

Thanks for the response.

I still have a bit of trouble reconciling the concept of toe-in, while maintaining the integrity of what the microphones capture. It does make sense that more clarity can be accomplished when directing the drivers toward the listener, and correct rake-angle is important with respect to time-alignment.

Imagine that the performers are drawn out across the surface of a page. The drummer left, the bass player mid-left, the piano center, the guitar player mid-right, and the brass to the right. The main microphones in this hypothetical situation are at mid-left and mid-right. Now fold that piece of paper in half and tear it down the center. The left speaker projects the image captured by the left microphone and visa versa, thus forming a complete seamless image. Now if one toes-in the speakers, would it not be similar to turning the two pieces of paper inwards, where the performers are turned more sideways, the result being that the full width of the sound space, placement of players and projection of sound are now placed differently.
The center has now collapsed into a v shape, and the furthest left and right points of the sound space are now closer to the listener than the center, where the image has been 'sanwiched' the most. I can understand that very moderate toe-in (a small amount) might not do too much to effect the integrity of the image captured by each microphone, but so often I see many setups where the drivers are pointed directly at the listener at an extreme toe-in angle. It would seem, according to many reviews I've read, that pin-point imaging can be attained where outlines of performers etc can be imagined. Is this possible with more extreme toe-in? Is it more effective to bring the speakers closer together without toe-in?

Elk
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Re: The Awesome KEF 207/2

If I understand what you are positing, I think that you are correct as to what would happen with toe-in if the sound coming from the speakers had no or extremely limited dispersion - like a laser beam of light.

However, good speakers radiate sound equally (ideally) for a fairly wide angle. Thus, if the sound is coming out of the speakers in a 30 degree angle and the dispersion characteristics were absolutely uniform for every angle it would not matter how much toe-in you used as long as you sat within this thirty degree arc.

However, speakers do not disperse their sound perfectly. Additionally, the listening room's walls reflect sound, etc. Thus, adjusting toe-in does affect the characteristics of the sound that the listener receives. In my experience, toe-in does not change the width of the soundstage. Rather it helps lock in the soundstage more precisely. Adjusting toe-in can also help tonal balance, especially in the high frequencies.

The distance between the speakers relative to the listening position has an impact on the presentation of the recording's soundstage however. You can stretch and compress the width of the soundstage with different speaker width placement. You can also place the speakers too far apart and lose the center image while pushing all mid-center instruments to their respective far sides.

dcstep
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Re: The Awesome KEF 207/2


Quote:

I still have a bit of trouble reconciling the concept of toe-in, while maintaining the integrity of what the microphones capture. It does make sense that more clarity can be accomplished when directing the drivers toward the listener, and correct rake-angle is important with respect to time-alignment.

The mic capture is seriously manipulated in most recordings. Hardly ever are you listening to a simple stereo-pair. I only comment on that lest we get too fixated on what the mic hears as somehow being "perfect." Those of us that try to actually place mics find it incredibly hard to match what we hear with our ears with what comes through the mics.

Elk, did a wonderful job of answering your question in other regards.

Have you tried toe-in? I'd be curious to read if you're hearing something at odds with what we're saying.

Dave

O'Shag
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Re: The Awesome KEF 207/2

I am now grasping the concept better. First, that given the dispersion characteristics of speakers in general, the image remains, for the most part, unchanged if one sits within the maximum degree angle of a speaker's characteristic dispersion pattern. Second, that microphone setup is a lot more complex than the simple left/right example, so the page/microphone scenario I described is not typical. I think I will have to do some more placement and toe-in experimentation. Thanks much Elk and Dave for the helpful explanation.

I also have further clarification from reading an article on stereo imaging by John Atkinson:
http://stereophile.com/asweseeit/1286awsi/

dcstep
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Re: The Awesome KEF 207/2

Remember also that the roll-off as you move off-axis is often (most likely) not linear, but accelerating as you get further and further off-axis. Yes, you want to widen the "sweet spot" as much as practical, but most speakers will describe a limit which you'll hear if you have someone change the toe as you listen.

Start with the toe that you see a sliver of the inside edge of the cabs from the prime listening position. Next have someone move the toe in and out a degree or two at a time as you listen, using some music with a lot of midrange content (a simple female vocal is a really good subject for this testing).

When you really get the speakers driving together AND coupled well with the room for maximum bass, but minimum nodes and resonances, the image will hold together over a wide range of positions, not just the sweet spot. It'll even sound better in the next room. There's a very complex set of speaker-to-speaker and speaker-to-room interactions going on that are hard to address here in word. I'll just leave it at, there's no formula of X-inches from the back wall, X-inches from side wall and X-degrees of toe and X-degrees or rake that'll give you ideal positioning. All these factors are important.

Dave

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Re: The Awesome KEF 207/2

I have my speakers toed in to quite a serious degree with the ribbon tweeters almost facing the outside of my ears.

I sit about 8' away amd my room is 14' x 10' x 8'. I get an extremely focused soundstage with vocalists dead center usually. On some well recorded CDs the soundstage can be vast with the instruments placed distictly in space. But have come to realise recorded music is never going to sound like live when replayed, and to enjoy as it is recorded and replayed. I have a large collection of dense multilayered, wall to wall sound, vocal, instrumental music. Most of it studio work that took literally 1000's of hours to create.

From bands like 10CC, King Crimson, and Pink Floyd to modern work from Moby, Air, GoldFrapp, Spitiualized, etc etc.

I do have a small 'sweet spot" but then again, I only have one listening chair in the room and it is in that spot.

I have found whether with soft domes or ribbon tweeters, I prefer them to fire directly at my ears for utmost clarity in the high end. I think like most things audio, its down to prefence.

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Re: The Awesome KEF 207/2


Quote:
I have found whether with soft domes or ribbon tweeters, I prefer them to fire directly at my ears for utmost clarity in the high end. I think like most things audio, its down to prefence.


Absolutely!

Plus, unless really well treated, each room sounds different.

I have additionally found that ribbons - as well as planar speakers - have smaller sweet spots. But this may just be my experience.

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Re: The Awesome KEF 207/2


Quote:
Second, that microphone setup is a lot more complex than the simple left/right example, so the page/microphone scenario I described is not typical.


The various types of microphones, their pick-up patterns and placement are all massive topics. Fascinating stuff. There are some decent short articles on the web if you are curious.

O'Shag
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Re: The Awesome KEF 207/2

Thanks Dave. I'll try out the procedure you suggest. As Colin indicated, I want to acheive maximum clarity, with focused images, while maintaining a wide soundstage with lots of depth. Not asking for much, am I?

Incidentally Elk, I am interested in learning more about microphone placement, and how it affects the capture and reproduction of recorded information. I have a friend who is a singer well-known in the Afghan community. His name is Amhad Walli. Much of his music is beautiful and full of vibrancy. He wanted to learn more about high-fidelity recording to CD-R. In an effort to help him, I would love to give him some meaningful information and even try my hand at the recording process, although I know its a lot more difficult than it might seem. Thanks for the heads-up.

Elk
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Re: The Awesome KEF 207/2

Very Cool!

Recording a singer is both simple and difficult. Simple in that there is a single mic. Difficult in that the choice of this mic and other equipment, the room, the distance of the singer from the microphone and a number of other factors determine the sound that you will obtain.

To start you obviously need a microphone. I suggest one of the standard microphone workhorses, a Shure SM58. These are about $100.00 street price. It is rugged, well-known, has a frequency response tailored to vocals, and is a dynamic microphone - meaning that it doesn't need any power source to operate - just plug it in and you are set to go. Of course, you will need a mic stand and a microphone cable.

Then you need a microphone preamp and a way to record the sound. The most cost effective for most people is to use their computer. There are many recording interfaces. There are card-based interfaces that you install in your computer, as well as stand alone boxes that connect via USB or firewire.

On the affordable end of the scale a great choice for the PC is the E-MU 0202 AudioPod. It is around $130.00. It connects via USB, contains a microphone preamp (also switchable to line level input), another line input, two 1/4" outs, a 1/8" stereo out for connecting to computer speakers, etc. and a headphone out. It comes bundled with a bunch of useable software, including multi-track recording software. Thus, you would have enough hardware and software power to record two tracks at a time (perhaps a vocal and an accompanying instrument), add more tracks if you want, mix, process, etc.

This would easily get you going.

Don't be disappointed when your recording sounds dry, and "unprofessional". Singers have an incredible dynamic range and you will need to learn some compression to tame the vocal. You will learn what reverb and other processing sounds good. If you are lucky you can record in a great sounding space that complements the sound of his voice.

Play with microphone distance - close (within inches of the mic) sounds very different than 6" or 12" or 3 feet. Not only are different characteristics captured, most microphones have a "proximity effect" that boosts the low end when the sound source is within six inches. This is often very flattering to the singer.

Recording vocals as turned into a detailed science and high art. Learning how to record takes a lot of work and the equipment used on top recordings is incredibly expensive.

If you already have a computer (PC or Mac) you can get going for about $300.00, put together some nice sounding recordings, burn CDs and have a blast!

If you really get into it, there are some luscious $10,000.00 microphones I can suggest.

EDIT: I forgot to mention Reaper, a very reasonalbly priced full-function piece of multi-track recording software. It is shareware, with only a $50.00 license for non-commercial use.

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Re: The Awesome KEF 207/2

Elk,

can't thank you enough for sharing that great information. I am first going to check into the software you suggest. I think my friend already has some good microphones, so hopefully they will suffice. Your information on mic positioning is excellent. I'll talk to Ahmad about this information.
Many thanks

johnmarks
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Microphone theory

Hi-

If you are recording a singer and an ensemble, I'd recommend using two cardioid-pattern mics angled outward at 110 degrees and spaced 17 cm., the so-called ORTF pattern. I have a very simple rule: always track vocals in stereo. Bruce Swedien, who engineered the best-selling record of all time, tracked everything on "Thriller" in stereo (except direct feeds); even the squeaking door hinge was recorded in stereo.

If you want to dive into the deep end of microphone theory, the standard reference is Everest and Streicher's "The New Stereo Soundbook." Perhaps your local library can get it for you.

http://www.posthorn.com/Sbook_3.html

Regards,

JM

Elk
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Re: Microphone theory

Thriller does have great sound. Fascinating to learn that even solo instruments and voices recorded in the studio were recorded in stereo.

John is vastly more knowledgeable than I. However, I can second the book recommendation. It is excellent and accesible.

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Re: The Awesome KEF 207/2

How much toe-in is definitely a function of your own set-up -- your listening room dimensions, where you placed your speakers relative to the side and rear walls, your preferences in music, and, yes, even your amplifiers and source electronics.

Most of all, it all boils down to what you are trying to accomplish. Are you after a particular "sound?" Do you attend a lot of live concerts? If so, do you want to try to simulate what you have heard at those concerts? Some people couldn't care less -- they are after a particular sound that appeals to them. Others, like me, want to re-create the live acoustic, if at all possible. There are no rules.

You have to experiment. The suggestions posted are all "correct," but you have only yourself to please. You ought to be aware of what it is you are after, but, beyond that, your system interactions with your room are the ultimate arbiters of what you get out of money spent.

Try straight ahead. Then try toed-in radically. Note the differences. Then work the middle ground.

I hope you have a strong back and relatively managable speakers.

When in doubt, experiment. That's part of the fun.

Elk
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Re: The Awesome KEF 207/2

Do try "extreme" toe-in where the axis of each speaker actually crosses in front of you. That is, you can see a bit of the outside of each speaker. This works very well in some setups.

O'Shag
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Re: The Awesome KEF 207/2

Elk, Clifton, Dave, JM and Colin - thanks all for your helpful advice. There is a difficulty because of the wieght of the speakers, the KEF Reference 109, the Maidstones. They're really big, wide and heavy so difficult to move easily. But I've already begun experimenting.

John, thanks for the info on the recording handbook. I'll find one.

Cheers

Colnmary
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Re: The Awesome KEF 207/2

Have fun. My speakers are close to 90lbs each and I usually move them alone on a hardwood floor with a tape measure in my hand.

When everything snaps together and your jaw drops open when you hear the music pplays, all that sweating and hard work is worth it!

Elk
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Re: The Awesome KEF 207/2

Mine are 190 lbs each.

You can do it!

Elk
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Re: The Awesome KEF 207/2


Quote:
I still have a bit of trouble reconciling the concept of toe-in, while maintaining the integrity of what the microphones capture.


I had looked for this article at the time this thread was active. I happened to come across it now: Microphone placement and stereophonic imaging

This may be of interest as it addresses how microphone placement affects the image which is captured. It begins with the premise that the typical listening position as at one corner of an equilateral triangle.

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