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Autoformer Attenuation


Deang

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Thanks. Yep, same one I have. Time to call Al!

Those of you with newer networks are getting 3619-ET units and the networks have been rewired in such a way to allow for 1dB increments. I just did the same with the Super AA network - so no more gaps in attenuation. Still, you get -12dB or -13dB, there is no -12.5 with either autoformer or wiring configuration. I'm sooo confused. I'm also trapped in my car with just my phone and a bad memory!

Hmmmmmmm how about TOLERANCE? Literally and figuratively.

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Mike, by the time an autoformer starts to saturate, you're going to be deaf. If you haven't already, read PK's "The Problem with Attenuators". Roy mentioned the problems associated with phase, but I believe an autoformer will have considerably less distortion than an L-pad.

The percentage of hysteresis from the core is fairly consistent...it's not like it only starts happening after a certain threshold is reached. I'm not talking about the effects from core saturation. The magnitude of hysteresis with larger signals is certainly larger, but the signal itself is also larger. The ratio of signal to hysteresis is the more important figure of merit when discussing parasitic behaviors.

A resistive Lpad can always have less distortion than an autoformer - and be cheaper and smaller at the same time. I would be more than happy to provide measurements if you have a particular autoformer in mind.

You are correct to point out that the electrical impedance of the autoformer isn't going to be the same as the Lpad....those differences can be compensated for in different ways if you think those differences in particular offer significant sonic benefit. It's the nonlinear effects that we should be worried about - all the rest is just a matter of straightforward design principals.

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"Parasitic behavior", "non-linear effects"? Wow Mike, I think you might be an audiophile.

How does one go about measuring hysteresis?

A certain, rather well educated gentleman suggested that I move away from the autotransformer. He says resistors will have less distortion and sound better too.

I have no trouble giving up an autotransformer for you to use to settle this question.

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PWK's original comments on "L-pad distortion" had nothing to with comparing to the hysteresis and non-linear behavior of autoformers (phase shift related). It was strictly a peak/trough ratio of AMPLITUDE being slightly greater. Roy Delgado, PWK's "golden boy" and prolific horn designer prefers resistors because they have linear phase and none of the other anomalies of autoformers. The inductor is the least perfect component (most parasitics) ever invented, so avoiding it's use except when absolutely necessary is a good thing.

Edited by ClaudeJ1
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So Paul Klipsch, who was notorious for finding the least expensive way possible of meeting an engineering goal, chose not only the most expensive part out of the available choices, but the one producing the most distortion.

When Al started working on the first Universal, he was going to dump the autoformer because he thought it was just an expensive way to accomplish something he could do for less than a dollar. After he finished his testing, he adopted the autoformer.

It looks like you guys might be on the wrong side of this one.

Sorry Roy.

Edited by DeanG
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So Paul Klipsch, who was notorious for finding the least expensive way possible to meet an engineering goal, chose not only the most expensive part out of the available choices, but the one producing the most distortion.

When Al started working on the first Universal, he was going to dump the autoformer because he thought it was just an expensive way to accomplish something he could do for less than a dollar. After he finished his testing, he adopted the autoformer.

It looks like you guys might be on the wrong side of this one.

Sorry Roy.

Personally, I avoid the whole thing by tri-amping through a single capacitor per horn (active rolloff on the woofer bin, so no inductor at all). The tweeter picks up where the mass rolloff occurs in the K-402/K-1133. Having discrete gain control for each driver tweaks up the final db or so, after which global room EQ takes over.

Al K trashes PWK's "constant K" network. I remember from the "Dope from Hope" papers where a Heresy showed less amplifier distortion than an 8 ohm resistor when looking at a spectrum analyser BECAUSE it had a rising impedance at higher frequencies, not to mention 11 ohms on the woofer, but I digress. Al doesn't like varying impedance and uses a swamping RESISTOR across his autoformer, which is higher quality than Klipsch's. So I guess he's on both sides.

I'm on neither side, as I prefer only one cap for passive networks with judicious efficiency and rolloff matching of each section and matching disperions angles for each respective band (took 5 years to evolve). My next step my be NO CAPS and go strictly active with PEQ and time delays with either first or fourth order. Let the ears and measurements decide.

Edited by ClaudeJ1
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That doesn't sound right. The DBB should be giving you a little less than a Klipschorn does, and everyone without exception (until now) is knocking that thing down at least 12dB. Sure about those settings? BTW, it's coax, and if you're using the tweeter, it's a three-way.

I'm really just trying to see if there is a consensus with some of the more popular setups. K-402s excepted, it would appear that 12 -12.5dB is pretty much where everyone is at.

So, who is using 8 ohm versions of these drivers (BMS 4592-mid, DCM50)?

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Yes, I'm very certain only -3db for what I just described above. I've been up and down the setting scale and have used measurements as well. I was surprised myself that's all it took. I'm getting big time bass out of the DBBs. I am also using the crossover that came with the BMS drivers (along with my ALK ESNs), which should next to nothing to do with this.......but that's how I get 3-way "driver-wise", but 2-way "speaker/horn-wise".

Initially, I had no autoformers in my ESNs because I used them years ago with K402 on top of MWMs. No need for them. Well, that didn't work in this setup. The horns needed attenuation, but not very much as it turns out.

The ESNs sat on the shelf for years until I got these DBBs.

Basically, I'm in a position to someday replace the DBB cabinets with Jub bins........and change nothing else.

Everything works perfectly right now.

One thing I should mention that probably affects this a lot is that I am using an outboard EQ (on tape loop of Peach) to EQ the K402 and it has a huge smile in it from 600-5K and peaks at around -12.5 at 1.25K. That must be it.

Edited by mark1101
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"Parasitic behavior", "non-linear effects"? Wow Mike, I think you might be an audiophile.

How does one go about measuring hysteresis?

A certain, rather well educated gentleman suggested that I move away from the autotransformer. He says resistors will have less distortion and sound better too.

I have no trouble giving up an autotransformer for you to use to settle this question.

Do you think Bob's autoformers are representative of what could be expected distortion wise? I bought a set to experiment padding down my QSC horns, but I've not gotten around to it yet. Nevertheless, I could post the hysteresis and distortion curves.....give me several weeks though - it's concert season right now, and then I've got a big deadline in January . Or if you want, I'd be glad to measure other devices at the same time. I could even hook them up to my speakers and look at the resultant output distortion too and compare to resistors.

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All of the various models built by Universal Transformer have the same quality factor. Yeah, that would be great if you'd be willing to do that.

"Hysteresis" is an interesting effect to read about. I don't know what to conclude about it.

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All of the various models built by Universal Transformer have the same quality factor. Yeah, that would be great if you'd be willing to do that.

"Hysteresis" is an interesting effect to read about. I don't know what to conclude about it.

It's like handling a piece of paper spayed on both sides with 777 tacky adhesive.

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"Hysteresis" is an interesting effect to read about. I don't know what to conclude about it.

What do you mean? Are we trying to convince ourselves it's a non-issue, or trying to understand the audible implication?

The beauty of the air core inductor is the lack of ferrous material to be magnetized - which means very little if any hysteresis. If you want to compare the effects of hysteresis audibly, then you could build an air core to match, and then add a resistor in series with your iron-core to match the inductor Q's.

The problem with these generalities is that sometimes the electrical behavior surrounding a non-linear component can make its non-linearity a very small portion of the total system's behavior. For example, a diode is incredibly non-linear - but they're used all the time in power supplies and you definitely have audio signal currents running through the diode. But in a power supply, that non-linearity gets smoothed by the power supply capacitor. The incorrect conclusion would be that a diode can go anywhere in the audio path and not create problems - sometimes I think parallel arguments get made about the type of inductors and type of capacitors being used in various circuits.

All that to say, I would encourage you to find (with your ears) when magnetic hysteresis matters. Or if you want to be an engineer, you can just calculate out how much rejection a particular circuit will give you.

Also keep in mind that speaker motors can exhibit hysteresis as well. I would recommend conducting your listening with speaker with low magnetic hysteresis. If you subscribe to Voice Coil magazine, they periodically publish Klippel test results of various drivers and you can find the linearity of the driver there. Basically, anything without a shorting ring is usually bad....Klipsch typically doesn't use shorting rings on the principal of trying to use a horn to minimize driver motion (they gotta offset the cost of the horn somehow....) - except for maybe their higher end subwoofers.

So ya, to really isolate hysteresis you can't be using amplifier with output transformers, or speakers with non-linear motors...and then it becomes readily audible when you drop that iron-core inductor on the woofer to lowpass the signal.

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So Paul Klipsch, who was notorious for finding the least expensive way possible of meeting an engineering goal, chose not only the most expensive part out of the available choices, but the one producing the most distortion.

PWK was not always correct.

Also keep in mind that most of his publications that most often get referenced were from a long time ago when the industry was very different from today.

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So Paul Klipsch, who was notorious for finding the least expensive way possible of meeting an engineering goal, chose not only the most expensive part out of the available choices, but the one producing the most distortion.

PWK was not always correct.

Also keep in mind that most of his publications that most often get referenced were from a long time ago when the industry was very different from today.

I agree wholeheartedly with this. Having spent an entire day of my life with him at the factory, private club, and his home, I can say he was "set in his ways" to put it politely. He hated CD's and ANY commercial recording, referring to it as "dilute stereo." Although, I admit, the music he played for me at his home though his Khorns and center Belle sounded really good. He had false corners in a huge living room, which had much to do with the sound.

He was right about many things and hard to convince about change of any kind. This had good and bad aspects. Fred Klipsch bought the company and increased sales 7 times beyond what Paul ever did and the reason why this community even exists today!

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"...trying to understand the audible implication?"

Well, that would certainly be the one I'm interested in.

The effect of hysteresis was well known and understood during the time PWK was designing his filters - I have trouble with the idea that a mental giant like Paul Klipsch wouldn't have accounted for it while making choices that would be critical to his design.

I did enjoy that last post though, interesting stuff to think about.

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"...trying to understand the audible implication?"

Well, that would certainly be the one I'm interested in.

The effect of hysteresis was well known and understood during the time PWK was designing his filters - I have trouble with the idea that a mental giant like Paul Klipsch wouldn't have accounted for it while making choices that would be critical to his design.

I did enjoy that last post though, interesting stuff to think about.

Well he didn't think time alignment was important either, on speech and music, even though a Khorn's bass is 8 milliseconds behind the tweeter. PWK did a lot of really great things, the Khorn bass bin being one of them, but he wasn't perfect. Hey he was human. He farted in his couch during the demo I was litening to, but it didn't smell though. I was on the other couch.

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