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Multi-Way Conventional loudspeakers with crossovers

Dunlavy SC IV schematics ?
Dunlavy SC IV schematics ?
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Old 24th December 2018, 01:14 PM   #11
Cask05 is offline Cask05  United States
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Quote:
Originally Posted by Old'n'Cranky View Post
These speakers really do a lot very right. Far more than almost any other speaker I've heard...I have zero plans on changing any component values. Just updating the solen (shudders) parts for more modern, better manufactured items...And yes I know some out there are reading my posts groaning and yelling at the screen

I'd just verify what you're doing using measurements of the resulting response, particularly step response. If you really pull off this key measurement performance by swapping out parts, then you've got an issue to deal with via tweaking. I'd recommend doing one loudspeaker with new parts and keep the other stock until the measurements and tweaks are complete on the first one without deleterious effects.

Last edited by Cask05; 24th December 2018 at 01:17 PM.
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Old 24th December 2018, 03:39 PM   #12
mark100 is offline mark100  United States
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Dunlavy SC IV schematics ?
Related, permissible swerve i hope .....pls ignore if not

What does step response show, over and above, or better than, mag and phase curves?

(with room reflections out of the equation) thx
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Old 24th December 2018, 04:22 PM   #13
wesayso is offline wesayso  Netherlands
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It's just another way of looking at the same data.
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Use Science to design your speakers and they will sound like a piece of Art...
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Old 24th December 2018, 05:25 PM   #14
Dmitrij_S is offline Dmitrij_S  Europe
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Quote:
Originally Posted by Old'n'Cranky View Post
Update.
Friend asked me to babysit these speakers.
And after getting his blessings I removed one crossover and took many pics.
I have also now drawn up the crossover.

Due to technological advances, there is much room for improvement.
If he decides to go that way that is.....
It's seems, that there was several revisions of the crossovers. I took the SC-IV crossovers photo when a colleague asked to replace damaged tweeters. Although revision printed in the PCB looks the same, however the crossovers physically looks slightly different (mine have more capacitors and coils).

Click the image to open in full size.

Click the image to open in full size.
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Old 24th December 2018, 05:46 PM   #15
mark100 is offline mark100  United States
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Dunlavy SC IV schematics ?
Quote:
Originally Posted by wesayso View Post
It's just another way of looking at the same data.
Yep, that i understand.
I was just wondering in what situations, what tuning tasks, would folks prefer to use step response.


I look at it, but really only for additional confirmation of having achieved good tuning.
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Old 24th December 2018, 05:57 PM   #16
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by mark100 View Post
Related, permissible swerve i hope .....pls ignore if not

What does step response show, over and above, or better than, mag and phase curves?

(with room reflections out of the equation) thx
"First, the time and frequency domains are related to each other, mathematically; sometimes in a simple way and sometimes in a more complex manner. For example, events in the time domain (such as changes of signal amplitude with time) always produce events in the frequency domain, with components that are generally related by the reciprocal of the variations in amplitude with respect to time. Further, a short impulse in the time domain contains implicit information regarding frequency response, phase response, step response, etc., all of which may derived by FFT analysis of the impulse. (Doug Rife's now famous MLSSA system is an excellent example of using FFT analysis of an impulse to determine most loudspeaker performance attributes.) Once understood, the step response (merely the integral of the impulse response) provides a quick visual evaluation of several time and frequency domain properties of a loudspeaker.

Of course, most audiophiles, without an appropriate technical and math background, probably cannot visualize how so many of these seemingly diverse performance properties can be so directly related to each other - but they are! The only exceptions are the impedance, radiation patterns and non-linear distortions (THD and IMD).

Linear signal distortions, such as a poor impulse/step, large variations in the modulus of amplitude and phase Vs. frequency, etc., can directly affect the "perceived realism" of complex musical waveforms reproduced by any component within the audio chain, including the loudspeaker. The acoustical reflections from the floor, ceiling, walls, etc. of the listening room add another set of "time and frequency domain distortions" onto those of the audio equipment, though with a very different signature in the time domain. The difference is that most time-domain distortions created by equipment, including loudspeakers, typically occur within a time window of less than a mSec, compared to several milli-seconds for an average "floor reflection" and even longer for wall and ceiling reflections within most rooms.

Also, a property of human hearing, known as the "fusion time" (which is the interval of separation between short transients required to perceive whether one or two transients are present), permits a "critical listener" to discern between room reflections (normally arriving more than about 5 mSec after the direct sound) and time-domain distortion created within audio components, including the loudspeaker (which occur within a time window typically much less than 0.5 mSec.). Thus, fusion time helps us to become familiar with and ignore most reflections from room boundaries, while letting us discern time domain distortions produced by equipment/loudspeakers as a blurring/smearing of musical transients or an alteration of spectral balance, etc.

With respect to your question as to what "... blind music-playback tests you and your colleagues have performed with the ***only*** variable being changes in "phase" behavior, with results showing a preference for one kind of behavior over others?", we have conducted quite a wide spectrum of tests during the past 20-plus years. We spent the time and money to do the research for two reasons: 1) it appeared to have been ignored by other investigators, and 2) it represented a unique technical challenge, was intellectually interesting and potentially commercially rewarding. (Commercially rewarding in the context of permitting us to better understand certain design goals and performance constraints, leading to better performing and more salable products.)

With regard to the audibility of changes in phase Vs frequency of a loudspeaker (or any other audio component, for that matter), our investigations have tended to show, pretty conclusively, that small changes of less than about 30 degrees per octave are probably not audible - except when listening to certain complex signals such as impulses and square waves. However, phase changes exceeding 180 degrees within an octave (or less), created by a loudspeaker crossover network, non time-coherent drivers, etc., are usually audible with complex waveforms and musical transients, when compared to the unaltered original signal. This is especially true if the 180 degree phase shift occurs within a octave or less within the frequency range from about 200 Hz to 5 kHz (often referred to as the mid-range region of most loudspeakers). I could go on and on about this interesting subject but time presently is not available to do so. It is shame that more investigators have not explored this generally neglected but very important ground.

Last, but not least, I would like to remark that if I had to choose but one measurement of a loudspeaker from which I would be required to determine and describe most of its performance properties, including frequency response, phase response, impulse response, etc., it would be "step response". For those familiar with step response and what it has to reveal about so many important properties (at a mere glance), it is a true gem in disguise.

Best regards, John Dunlavy"


From : Archives: John Dunlavy (rec.audio.high-end forum posts 1997-2001) -

Techtalk Speaker Building, Audio, Video Discussion Forum



Some editorializing on my part:

Curiosity got the better of me a few years ago, so I sold my sedan, bought a CUV, and rented a pair of SH50s. Then I listened to them and measured them up against my Gedlee Summas and a set of Lambda Unity horns that a forum member has. To my ears, all three speakers sound very different, and I think a lot of it boils down to the crossover. There's lots to learn from those old posts from John Dunlavy. They don't get a lot of mileage because they predate the world wide web.

Click the image to open in full size.

Click the image to open in full size.

Here's the SC-IV and it's step response

Click the image to open in full size.

Here's the step response of a Wilson Watt Puppy, which uses higher order filters.

It is possible to get good step response with higher order filters, like this : http://www.melaudia.net/zdoc/jml_crossovers_etf04.pdf

Last edited by Patrick Bateman; 24th December 2018 at 06:16 PM.
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Old 24th December 2018, 06:11 PM   #17
Cask05 is offline Cask05  United States
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I suppose if you read the linked Stereophile articles, you would've answered your own question. However, judging from how you asked your question (which may or may not be an actual question), I gather that what Dunlavy said about the subject doesn't really meet your approval.

But what he said speaks volumes to me because I've found that it's spot on through experience. When one tries to adjust for reasonable step response, typically he/she finds that they're juggling PEQs, polarities, and delays iteratively in a way that they find to be stressing of his/her skills. He/she will also wind up using first order crossover filters (if using IIR-only filtering).

I get a ton of insights as to what's really happening by using step response as the measure. Sure, I look at the other plots for further understanding of what's occurring, but it's the step response that shows me if I'm there or not.

The subjective results--when done successfully--are pretty much breathtaking on my setup (which is fully horn loaded). YMMV.

Quote:
Dunlavy: It may come as a surprise—this is giving away a trade secret—but when I design a loudspeaker, I first design it by looking at the step response. I find that by playing around with the crossover network while observing the step response in real time, any change I make is immediately available. When I get the step response right, everything else goes along. It's implicit. It goes along for the ride.

Atkinson: The perfect on-axis impulse response will also give you a perfectly flat amplitude response on that axis. But with most loudspeakers in the world, even if they have perfect, flat amplitude responses, that doesn't mean they have perfect impulse responses?

Dunlavy: That's right. You can go one way but not the other. Flat on-axis response provides very poor correlation, in general, with what you hear. On the other hand, if you have near-perfect impulse and step responses, it follows that you must also then have from that a near-perfect frequency response on-axis. And using a first-order crossover network is the only way you can achieve accurate impulse and step responses. As soon as you go to a second-order crossover, the impulse response is hideous.

...Designing with higher-order crossover networks greatly simplifies the blending task between drivers. But what most people don't realize is that one of the really great difficulties in designing with higher-order crossovers is that they store energy. That's very visible when you look at the impulse response of a speaker that has a second-, third-, or fourth-order network. And the step response also looks terrible.

Of all of the measurements that we take that come more close to predicting, or most close to predicting how a speaker is going to emulate a properly recorded live performance, it's step response. Everything is implicit if you know how to interpret a step response...if my life depended upon my describing what I thought a speaker was going to sound like, all other factors being equal, I would choose step response. And feel very confident that I would be spot-on.
Chris
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Old 24th December 2018, 06:34 PM   #18
Patrick Bateman is offline Patrick Bateman  United States
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I love Dunlavy, but what he's saying about first order xovers isn't 100% true. It *is* possible to get good step response with higher order crossovers.

I didn't know this for AGES. I still have my Vandersteens, which I purchased when I was under the misconception that you must use first order filters to get a good step response.
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Old 24th December 2018, 06:57 PM   #19
mark100 is offline mark100  United States
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Dunlavy SC IV schematics ?
Thanks everybody.
I think the discussion has turned more complicated than what I was asking...
I was trying to ask, how do you read, what do you see, in a step response ...that then leads you to alter your design.
IOW, when, why, and how do you judge a step response?

I know what a good step looks like, or at least I think I do ....
I've included an example that I'm used to achieving, of a 4-way.

So far, for me to get a good looking step, I work with mag and phase and get both as flat as possible.
That of course means dialing in x-overs, levels, timing, etc...all of which adjustments I can see pretty easily, with mag and phase under dual FFT.

But I couldn't start to look at step and know what to alter.

Is there some material that shows examples of funky step functions, and how to read them?
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File Type: jpg REW2 4way step.jpg (62.3 KB, 71 views)
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Old 24th December 2018, 07:03 PM   #20
mark100 is offline mark100  United States
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Originally Posted by Patrick Bateman View Post
I love Dunlavy, but what he's saying about first order xovers isn't 100% true. It *is* possible to get good step response with higher order crossovers.

I didn't know this for AGES. I still have my Vandersteens, which I purchased when I was under the misconception that you must use first order filters to get a good step response.
Agreed !
The 4-way step I just posted used 16th order LR's for all the x-overs.

But I do think, if using passives, that lower order is practically essential to maintain the flat phase that's inherent in a good step response.
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