New White Paper posting

[durwood]

Originally Posted by markus76

Don't think so. Stereo will always be a subset of multichannel.

Multi-channel relies heavily on a center channel, this is not true stereophonic. I'd say here in the US surround sound is more common than stereo and being that it costs more to put together surround sound then people ARE willing to pay more for something that sounds more believable.

In the early days 2 channel beat out 3 channel purely because it was economically feasible back then. The 1930's-50's was a very different era compared to today. You have to remember LOTS of things had to happen with limited tech to double the number of channels, so 3 was out of the question.

[durwood]

Originally Posted by markus76

Hi Patrick

You stated that a couple of times in the past and I'm curious what the problem here might be. Are there any measurements that would show where the Summa's far field begins? Words like "smoother", "faithful" and "articulation" don't mean much to me when talking about loudspeaker performance.

In small rooms the big Summas should perform even better because of their higher directivity down to lower frequencies.

Best, Markus

In real life sound is not so controlled. Our hearing needs a certain amount of ambiance/space interaction to believe what we are hearing is normal instead of forced.

[gedlee]

Originally Posted by durwood

I don't agree it's the same. Your dispersion pattern is very simple and uniform and does not alter the directivity shape. Using DSP the dispersion pattern is specifically shaped between different frequency bands. You can find this type of practice in the pro audio world with array steering. While your method might be simpler, you can do the other method for about the same price (or cheaper) and maybe get better results.

You can't be serious about cheaper. As I said that paper was about ten years old and we haven't seen a product. If there ever is one then I'll take a look.

Perhaps you haven't noticed the market increase in "soundbar speakers" from yamaha, philips, marrantz, etc etc? While these may not be exactly like what is proposed, it is still being investigated/researched in many universities too. Stereo is and will die a slow death. It is the reason multichannel has overtaken the market and preferred over 2 channel. The problem with the current soundbar speakers is the same as with many vanilla commerical offerings...the speakers are too small to deliver the dynamics neccesary for realism.

I have heard many of those "soundbar speakers", you have got to be kidding to think this has any future except for novices who only care about audio for TV. Not one of them that I have heard (most) was worth having.

Yes, they are all too small, but you can't do that with bigger speakers, at least not inexpensively.

What I do is not a hypothetic "university research project". Its a real product with all the warts and practical compromises already built in. As I have said, vaporware is always the best design.

I don't think your responses here are realistic "stereo is dead", "soundbars are the answer". We are certainly not after the same things.

[Key]

Maybe I need to clarify what I meant about the delay compensation thing. I am aware that you can on a traditional stereo adjust the volume and delay to make the stereo imaging remain stable if a listener is off axis. This is used in Meridian DSP loudspeakers. But what does this accomplish? You still have one sweet spot for one person and if you fix the imaging for the person on the right side then the center and left side has altered imaging. So I don't see this as much of a problem solver. I guess it's a nice gimic but good luck getting someone to where a head tracker so that it "works".

I am all about Surround Sound and Quad. But I think there is something about stereo. How easy it is to setup and how effective it is in it's simplicity. And ime a lot more real rooms - not dedicated listening rooms - are compatible with stereo than surround sound. BUT I tend to think a lot of the improvements audiophiles seem to be on a life quest to find are easily attainable with surround sound. If you are going for realism with stereo I am afraid you will never get what you are looking for. At least not without a healthy imagination/suspension of disbelief.

[Patrick Bateman]

Originally Posted by markus76

Hi Patrick

You stated that a couple of times in the past and I'm curious what the problem here might be. Are there any measurements that would show where the Summa's far field begins? Words like "smoother", "faithful" and "articulation" don't mean much to me when talking about loudspeaker performance.

In small rooms the big Summas should perform even better because of their higher directivity down to lower frequencies.

Best, Markus

I know subjective descriptions are frowned on a bit around here, but I can't help but note that there's a audible difference when you sit too close to a speaker with a large center to center spacing. As I see it, there are two easy ways to sidestep the problem: Sit further back, or use a smaller spacing. In the drive for larger and larger waveguides, people seem to have neglected that they need a big ol' room to sound their best.

As for measurements, I wouldn't be comfortable doing that. My mic is a lot cheaper than what Geddes is using, and I measure outside, so we're going to get different results. While I am no slouch at this stuff, he has about a hundred IQ points, twenty patents and thousands of hours of work that I don't

But the theory, that's easy to discuss.

First, the equation:

nearfield to farfield transition = r
array length in meters = l
radiation frequency = f

r = ((l^2)*f)/700

The equation above is from a JBL white paper by Mark Ureda, named Line Arrays - Theory and Application.

You can also rearrange Ureda's formula so that we can focus on the length of the array:

l^2 * f = r * 700
l^2 = (r * 700)/f
l = sqrt ((r*700)/f)

Now let's crunch the numbers, first for 1000hz:

r = ((l^2)*f)/700
r = ((0.8^2)*1000)/700
r = 0.9meters, or 36 inches
(array is 31", both woofer and waveguide are playing here.)

And now for 2khz:

r = ((l^2)*f)/700
r = 1.8meters, or 72 inches

And for 10khz:

r = ((l^2)*f)/700
r = ((0.38^2)*10000)/700
r = 2.1meters, or 82 inches
(This one assumes an array length of 15", the waveguide alone.)

Admittedly, the theory doesn't indicate that there will be a problem, as long as you stay at least seven feet back. To my ears, the distance to the array needs to be double or ideally triple of what the equation shows. I've also found that small arrays sound better than large arrays when you're seated closely.

[Key]

Originally Posted by Patrick Bateman

[font=verdana]I know subjective descriptions are frowned on a bit around here, but I can't help but note that there's a audible difference when you sit too close to a speaker with a large center to center spacing. As I see it, there are two easy ways to sidestep the problem: Sit further back, or use a smaller spacing.

What about toeing in further?

[Patrick Bateman]

Originally Posted by Key

What about toeing in further?

Rotating the array does not change it's distance to the listener, and that's what we're trying to increase. Alternatively, we can simply reduce the size of the array.

Keep in mind, this isn't a knock against the Summas, if anything it's a plug for the Nathans. I don't see any good reason for an 18" Summa, and even 15" is more than I need.

The thing about directivity is that even a 3db or a 6dB reduction in off-axis energy makes a huge change in the power response, so a moderately sized waveguide makes a bigger difference in the response than the graphs show.

For instance, if you have a six inch loudspeaker with a perflectly omnipolar pattern, and it creates a reflection on a nearby wall, it will create a peak of as much as six dB. That's the equivalent of quadrupling the power at that frequency. As you can imagine, very audible. OTOH, if the off-axis response is down by 6dB, the peak can be no louder than 3dB, or equivalent to a 100% increase in power (at that frequency.) As I see it, how you get there doesn't matter. There are a number of ways to control directivity.

This ignores masking, and phase, and all kinds of good stuff, but you get the general idea.

[markus76]

Originally Posted by durwood

In real life sound is not so controlled. Our hearing needs a certain amount of ambiance/space interaction to believe what we are hearing is normal instead of forced.

A loudspeaker can't be assessed as a real (natural) sound source. The whole reproduction chain from sound recording and mixing to the loudspeaker-room-system make up the illusion. The key is the indirect sound field (I stopped using the word "diffuse" because the sound field in acoustically small rooms is not diffuse). We still don't know enough to make the best out of stereo/multichannel, loudspeakers and rooms and there might be solutions that are mutually exclusive. All we know is that we're trapped in Audio's Circle of Confusion

Best, Markus

[Key]

Some of that circle of confusion comes from second guessing the quality of the audiences playback system imo. I also don't think it's a great idea to master and mix an album in a room with an abundance of absorption when the target playback room most likely will just have everyday objects and not any specific absorption. By using absorption it also brings the cost of an accurate playback system way up. And is it really necessary?

[markus76]

Originally Posted by Patrick Bateman

I know subjective descriptions are frowned on a bit around here

And there's a multitude of good reasons for that!

Originally Posted by Patrick Bateman

but ... the theory doesn't indicate that there will be a problem, as long as you stay at least seven feet back.

So we still don't know where the Summa's far field begins. Maybe Earl has data on that? He already showed so much pretty colorful and detailed data in his paper that the other (bad) boys don't show