Round Tractrix

[Chris A]

I thought I would have a lot of trouble with reflections off the top of the cabinets, but it hasn't been a problem for me. I even tried different materials on the top of the cab, to see if I could hear a difference. No change.

Let's think about this:

1) What is the reflection coefficient for frequencies above 4.5+ KHz off the top of the La Scala cabinets (i.e. at the steep vertical angle from the tweeter's horn)?

2) Where is the probable centroid of the reflected polar located in the vertical dimension? (I.e., it is pointed at the ceiling?)

3) What is the ratio of the second reflected wave magnitude from the ceiling to the direct wave from the tweeter? (I bet it's very small at 4.5+ KHz.)

Chris

[Guest David H]

I decided to move it to the back, to align it with the K55. BOOM!!! The imaging became cleaner, tighter, with the soundstage now HUGE.

I also time aligned a pair of speakers but I used an active crossover to take my measurements, then I adjusted the drivers placement until the the delays were zero. Surprisingly the magnets were very close to perfect alignment. Next I designed and built the speaker boxes to compliment the drivers placement.

I would think time alignment by ear would be no more than a guessing game, however magnet alignment seems to have some relevence.

Dave

[Al Klappenberger]

Dave,

What network where you using when you did that?

I really want to get to the bottom this, but moving the drivers around is NOT conclusive to spite how obvoius it might seem.

Al k.

[Chris A]

I would think time alignment by ear would be no more than a guessing game,

For the tweeter/midrange alignment, +/- 1/2 inch is pretty close (0.037 ms = 37 us).

For the woofer/midrange (crossed at ~450 Hz for the La Scala), the alignment is less critical, probably on the order of 0.4 ms or ~5 inches, IMHO.

Chris

[Marvel]

Marvel,

What networks in in your LaScalas?

AL K.

I am using some DHA2 crossovers, designed by John Albright. Since I am using 2A3 amps, I wanted a very simple crossover.

btw, John had loaned me a pair of your crossovers for me to use until I got mine built. At the volumes I listen, with one of yours on one side and a DHA2 on the other, they sounded very close to each other.

Bruce

[Guest David H]

Dave,

What network where you using when you did that?

I really want to get to the bottom this, but moving the drivers around is NOT conclusive to spite how obvoius it might seem.

Al k.

Digital active crossovers.

Dave

[Marvel]

decided to move it to the back, to align it with the K55. BOOM!!! The imaging became cleaner, tighter, with the soundstage now HUGE.

Bruce,

You know that this makes you the new poster child for the "time-aligned" crowd... This is very interesting that it works well just as you have implemented it.

If I were you, I'd make patent application ASAP...

Chris

[]

[Guest David H]

For the tweeter/midrange alignment, +/- 1/2 inch is pretty close (0.037 ms = 37 us).

I certainly understand what you are getting at here, but how do you know how many ms delay you need unless you are taking electronic measurements?

Dave

[Al Klappenberger]

Ok.. Here's what I am getting at..

The fact is that I hear this exact conclusion from people who have installed extreme-slope tweeter / squawker networks. The stereo image improves and the sound is clearer. I believe there are two factors here. The fact is that not many of us are willing to mount the tweeter a foot on top of the cabinet and to the rear. And what do you do to align the midrange to the woofer? You drill a hole in the wall! RIGHT!

When a tweeter is closer to you than the mid-range using a gentle slope crossover you are getting sounds meant for the mid-range into the tweeter and tweeter energy in the mid-range. If your tweeter is closer to you, as most are, you get energy on both sides of the crossover first from the tweeter than you get it again from the mid-range. This is perceived by the brain as an echo. It screws up the stereo image and it causes a smearing and comb efects. This I can hear with my own ears. It went away when I installed a crossover that let only the correct driver make the sound it was intended to. In this case each driver is making only one sound. The only alignment you do by lining up the drivers in this situation is to align the high set to the low set of components of a complex waveform. Until these are so out of time that you hear them a separate entities there is nothing to align! My experiments with multiple generators proved to me that I can not hear phase misalignment between complex components even if they are continuously changing on a fixed tone. This is all that is left when you have only a single source generating each component (harmonic). Moving a driver while using a gradual slope crossover does not tell you what is important. Is it the double occurrence of everything, or the phase errors becoming individual entities to your perception? Moving drives like that will not answer the question, You are moving both at once.

Another point: I read someplace where PWK did a similar test moving the high end of a Khorn to establish if alignment between the woofer and high section was important. His conclusion was that it was NOT! This is what he WANTED to conclude though. Preconceived notions are very important here. If you believe a sugar pill will relieve your pain, it probably will! Assuming he was right. At what frequency does this time alignment become important?

I believe the only way to determine how much time misalignment is acceptable between components of a complex waveform is to use a ACTIVE extreme-slope crossover with a variable delay in one channel of a 2-way system having a high crossover frequency. That's a tall order! One person listens while another moves the delay. Note that there must be NO OVERLAP of energy between the drivers, If there is, you are back to the double exposure thing you will have by just moving a driver!

A third point: When I hear comments like "wow" and "boom" and "within 1/2 inch" my red flag goes up. Audio just isn't like that, but preconceived notions are. PLEASE MAKE NO MISTAKE ON THIS POINT. It is not an insult or an attack on anyone's integrity or honesty. It is human nature! This is why double-blind trials exist. A single persons opinion is valuable as just that, a single opinion! I really would like to know what amount of delay the ear can tolerate between "harmonics" before each become individual entities but I can not accept sliding a tweeter at you is conclusive of anything but that there is SOMETHING important going on. There have been enough single persons observations to convince me of that point. The question that I want answered is exactly what!

Al k.

[Guest " "]

didn't Mr Klipsch do a blind test in which he had an audience sit in front of a curtain and behind the curtain there was some driver movement to determine if the audience could tell a difference and he concluded that they could not. is this another version of the old saying my imagination is my reality. If I warm up my car on a cold day before taking off it will run better. if I warmup my stereo before I get into serious listening mode it will sound better. If I move drivers around, it will sound better.

[Al Klappenberger]

Fritz,

Thank you! That is exactly what I was referring to in my last post. My memory wasn't fooling me. The implication is that it is importnat to fix the timing problem between a tweeter and a mid-range but maybe not between a woofer and mid-range. Maybe becasue of the wavelength relation to the speed of propagation. Maybe it's just human ear / brain comprehension too!

Al k.

[Marvel]

Another point: I read someplace where PWK did a similar test moving the high end of a Khorn to establish if alignment between the woofer and high section was important. His conclusion was that it was NOT! This is what he WANTED to conclude though. Preconceived notions are very important here. If you believe a sugar pill will relieve your pain, it probably will! Assuming he was right. At what frequency does this time alignment become important?

Because of the longer wavelengths, it probably isn't as important as the alignment between the mid and tweeter.

believe the only way to determine how much time misalignment is acceptable between components of a complex waveform is to use a ACTIVE extreme-slope crossover with a variable delay in one channel of a 2-way system having a high crossover frequency. That's a tall order! One person listens while another moves the delay. Note that there must be NO OVERLAP of energy between the drivers, If there is, you are back to the double exposure thing you will have by just moving a driver!

A third point: When I hear comments like "wow" and "boom" and "within 1/2 inch" my red flag goes up. Audio just isn't like that, but preconceived notions are. PLEASE MAKE NO MISTAKE ON THIS POINT. It is not an insult or an attack on anyone's integrity or honesty. It is human nature! This is why double-blind trials exist. A single persons opinion is valuable as just that, a single opinion! I really would like to know what amount of delay the ear can tolerate between "harmonics" before each become individual entities but I can not accept sliding a tweeter at you is conclusive of anything but that there is SOMETHING important going on. There have been enough single persons observations to convince me of that point. The question that I want answered is exactly what!

Al k.

So, are you saying that physical alignment isn't acceptable and audible but using delays to accomplish the same thing is ok?

Having a lower slope crossover makes it even more obvious when the drivers are aligned. Moving the tweeter is no more difficult than focusing a lens/telescope. Using tools is great, more power to you. If you can't hear the difference, your tools don't mean anything. Obviously, your extreme slope crossovers sound good, because people can hear the difference they make.

If you still haven't tried this, then Dennis is correct. and you shouldn't be commenting on it. For me, moving the tweeters was a no brainer. The cost was zip, so my only investment was time.

[Johnny's Jill]

When a tweeter is closer to you than the mid-range using a gentle slope crossover you are getting sounds meant for the mid-range into the tweeter and tweeter energy in the mid-range. If your tweeter is closer to you, as most are, you get energy on both sides of the crossover first from the tweeter than you get it again from the mid-range. This is perceived by the brain as an echo.

The perceived echo I believe is exactly what is causing the smear, resulting in poor imaging.

I have buit time aligned speakers, I have used digital time alignment, and I have used the Extreme Slope Networks, all seem to resolve echo in question.

On all Klipsch Heritage speakers physical time alignment would be very difficult unless you are using a coaxial driver like the DCX-50 (Covered in another thread).

Active time alignment is certainly possible but it is difficult to set up and is expensive.

The Passive ES network are a simplest solution, although they are not time aligned they eliminate the echo, and improve imaging.

Craig

[Al Klappenberger]

"So, are you saying that physical alignment isn't acceptable and audible but using delays to accomplish the same thing is ok?"

No.. What I am saying is that moving the drivers is not acceptable to most loudspeaker owners. The WAF and all that! Stereo fanatics like us will do anything! That's part of the fun.

"you still haven't tried this, then Dennis is correct. and you shouldn't be commenting on it."

When I have a point of view based on facts I have insight into I have a right to comment as I please. Do you have a point of view on mercy-killing for example? Should you try it before you comment if that were the subject of discussion? I won't try something I believe is not conclusive when I believe there is a better way to accomplish the same thing. Maybe he should not have commented about time aliment until he tried extreme-slope crossovers.He was talking from within his experience as am I. I say he should not have suggested that I should shut up! Fact is, I considered it offensive.

"For me, moving the tweeters was a no brainer. The cost was zip, so my only investment was time."

ABSOLUTELY! I agree totally!

Oh yeah.. One other point. Your tweeter, sitting back like that, is only time aligned horizontally. You still have error in the vertical plane. That causes trouble too. I doubt it's as big a deal as direct path timing though. It will still cause comb effects if both drivers are making the same sounds.

Al K.

[jwc]

SF...

Your signature cracks me up everytime I read it.

[Chris A]

For the tweeter/midrange alignment, +/-1/2 inch is pretty close (0.037 ms = 37 us).

I certainly understand what you are getting at here, but how do you know how many ms delay you need unless you are taking electronic measurements?

I'm not sure what you are asking - if you can hear a change in imaging, and that happens when you place the tweeters in approximate physical alignment with a midrange driver, what more is needed? This alignment technique is fairly precise, as stated above.

For those of you not using physical alignment but using an active crossover to make the correction--the speed of sound in air is approximately 1132 ft/s at room temperature. It's not difficult to calculate the delay correction or to simply "walk it in" using an active crossover like the Dx38. If you have an anechoic chamber (like they have in Hope) or an acoustic measurement setup at home that you use, then it's even easier to get very good alignment. That is one reason why Klipsch maintains its anechoic chamber in Hope.

If you are talking about woofer-midrange alignment: I've heard the difference with 2-way Jubs and that delay is on the order of 2 ms, which is smaller than the 3.5 ms delay on my Belle midrange-woofer. The delay correction is apparent during impulsive source material. Once heard corrected in A-B fashion, I find that I like it corrected. And it's very easy to do that...

Chris

[Guest David H]

I'm not sure what you are asking - if you can hear a change in imaging, and that happens when you place the tweeters in approximate physical alignment with a midrange driver, what more is needed? This alignment technique is fairly precise, as stated above.

Aligning the magnets in close proximity will certainly get you in the ball park I agree. My preference is digital measurements.

[Guest David H]

Time aligned Heresy, WAF=0 [] Looks like Big Bird

[Chris A]

My preference is digital measurements.

I'm not sure that instrumented measurements can yield better results in practice.

For illustrative purposes: are the listener's ears located vertically on the centerline between the tweeter and midrange drivers, or are the listener's ears typically higher or lower than the drivers? Wouldn't this affect the "correct" delay needed? How much closer than a
few microseconds do you need to be?

"Measure with a micrometer, mark with chalk, cut with an axe..."

Chris

[Nat Denkin]

For those of you using digital active crossovers, a simple experiment should be possible.

Configuration A: setup as described in http://freerider.dyndns.org/anlage/LeCleach.htm (very easy to do if you are using a DCX2496. This setup uses 18 dB/octave Butterworth shapes and requires the -3 dB points to be spearated and the measured delays to be shifted. It's all in that link including square-wave responses.

Configuration B: use the steepest slopes supported at each crossover, for example 48 dB/octave Linkwitz-Riley using the same crossover frequencies .

The crossover frequencies should be within the ranges supported by the drivers and equalization and output level should be the same.

Now, go to your sweet spot (the point where you want optimum performance) and listen to the same track using Configuration A and Configuration B (both should be stored in memory so each can be easily recalled). Listen for any differences in percussion and voice. If done properly, Configuration A should have the delays between drivers set to produce much less phase variation across the band than is typical. Configuration B minimizes the overlap between drivers (ok, not as sharp as extreme slope). Have someone else switching (or fakining it) and see if you can consistently tell them apart and prefer one.

Are the differences (if any) the same when you move away from the sweet spot and repeat the experiment?

NOTE: the results may depend on what you are listening to and whether the sound engineers who set up the microphones and did the mixing knew what they were doing! So try several tracks of different sources.

Any takers?

Thanks,

nat