Crossover Roadshow

[Budman]

Muel, are these absurd things in your possession. where's the pictures. we want pictures

[Deang]

Descriptive/generic - source of power. Good catch, I should use different verbiage.

[muel]

Don't have them yet... have they shipped, Dean?

[Deang]

He'll no, blame that thread. Just finished them last night. I almost shipped after work today, but then remembered they would just spend the weekend in a 100+ degree UPS truck.

[kaiser SET say]

Good call, there will be no "UPS" yours for Muel!

[mikebse2a3]

This increases the current demand from the amplifier and without question makes it work harder.

I don't agree with this statement. An amplifier is a current source, it's job is to deliver current -- delivering more current doesn't mean it's "working harder", it just means it's doing more of what it was designed to do in the first place. An amplifier is working more, not harder, and I don't think "harder" comes into play unless you begin running the amplifier near the limits of its operating parameters.

Dean you might not agree with the statement but you would also be wrong![]

I can easily prove the statement is true if you would like.

When you step on the gas pedal of your car is the engine working harder the more you step on the gas? If you load the car down with more weight does the engine work harder? So it is when we ask the amplifier to deliver more current and yes eventually you will reach it's design limits. With impedance compensation I have measured as much as -3db reduction in the SPL in the frequency areas affected by the compensation. This reduction of -3db also means maximum output in this region will be reduced by -3db from any given amplifier. So if we are using a low wattage amplifier such as a 2A3 SET amplifier then reducing the power available in the affected area from for example 4w to 2w (ie:-3db) it is something to take into consideration because there is the real possibility that some might not be able to reach their previous maximum SPL preferred on some recordings. I experienced this issue myself (mostly on vocals in some very dynamic recordings) when I used the ALKs versus the AK-3 networks in my Khorns.

The only benefit is as you stated the less frequency variation due to impedance interacton between amplifier and network/loudspeaker. miketn

I wouldn't trivialize this as the benefit is significant. I deal with owners of single-ended, zero feedback amplifiers quite a bit, and all report a subjective improvement in the sound.

I certainly didn't trivialize this aspect and while without a doubt the SET amplifier's frequency response will be less influenced by a more constant Z network/loudspeaker's load there is still (due to all the complex variables in the total sound reproduction chain) a real possibility that someone might prefer the tonal shifting interaction of networks without constant Z. For proof of this tonal shifting preferences by listeners one need look no farther than the variation in listeners preffered tap db reduction choices of the autotransformer in the ALK networks as a good example.

Less anyone try to use this to bash low power SET amps all I can say is all amplifiers have flaws and this tonal shifting potential that they have can be a very forgivable one and some what correctable where as other type of flaws exhibited by high power tube and solid state amplifiers aren't so easily accepted in my experiences. Bottom line IMHO what's important is to understand as much as possible the pros and cons of any technology so that we can use it to reach our goals with our music systems.

miketn

[Marvel]

Sticking my nose in once more.

What's the net loss of efficiency with the swamping resistor?

I don't know the answer to that, but years ago we talked about a loss off efficiency with the constant impedance networks. For me, the trade off was/is well worth it, even with my 3.5 watt amps. It works for me and that is what is important.I don't think htere is as much loss in the DHA2 and SuperAA as in Al's extreme slope crossovers, but that's only what I have heard other people mention.

I prefer not to have the tonal shifts, thanks. It's one less thing to juggle. Unless I'm going to buy snake oil cables to shift it back.

Bruce

[mikebse2a3]

I don't know the answer to that, but years ago we talked about a loss off efficiency with the constant impedance networks. For me, the trade off was/is well worth it, even with my 3.5 watt amps. It works for me and that is what is important.I don't think htere is as much loss in the DHA2 and SuperAA as in Al's extreme slope crossovers, but that's only what I have heard other people mention.

Exactly Marvel..!

My main point was to dispell any misconception that a constant impedance network is making it easier on the amplifier when the opposite is the truth.

The second point is by knowing this fact a listener needs to test his system to make sure that he will still be able to acheive his desired playing levels when switching to these types of networks while using a low wattage amp.

The good thing is Dean is giving people a chance to experience this without any risk (other than shipping cost).

I prefer not to have the tonal shifts, thanks. It's one less thing to juggle. Unless I'm going to buy snake oil cables to shift it back.

It always makes me laugh when people are open to the fact that capacitors can make a difference in sound but cables can't have an influence.

miketn

[Marvel]

It always makes me laugh when people are open to the fact that capacitors can make a difference in sound but cables can't have an influence.

I understand, and know that there can be an influence. However, my wallet isn't too fat, so I can't even begin to go down that road. Have you ever talked to anyone at Klipsch about all the esoteric cables they use?

Bruce

[mikebse2a3]

It always makes me laugh when people are open to the fact that capacitors can make a difference in sound but cables can't have an influence.

I understand, and know that there can be an influence. However, my wallet isn't too fat, so I can't even begin to go down that road. Have you ever talked to anyone at Klipsch about all the esoteric cables they use?

Bruce

Who said cables have to cost alot to have an influence? Not I...!

Klipsch doesn't use expensive capacitors either does that mean they don't have an influence? Does an increasing cost of a capacitor always correspond to an improvement in sound? Cost isn't a good or complete indicator of performance in any product or given situation.

Edit: I have found that construction and materials can to some degree be used as an indicater of a good cable in my experience based on my listening experiences.

Have you ever talked to anyone at Klipsch about all the esoteric cables they use?

No need Marvel....I've done my own research and came to my own conclusions and implemented what I've learned into my system.

miketn

Edit: I sure hope my equating capacitors and cables having potential audible influences doesn't wake up the mighty Thebes...I see he is lurking on the forum this morning.![]

[jcmusic]

No need Marvel....I've done my own research and came to my own conclusions and implemented what I've learned into my system.

miketn

Mike do you mind sharing a little about the type cables you use???

Jay

[Deang]

"Are you getting shipping info through pm's?"

Sure. PMs, email, makes no difference to me.

"What's the net loss of efficiency with the swamping resistor?"

Mike said "...with impedance compensation I have measured as much as -3db reduction in the SPL in the frequency areas affected by the compensation." I'm certainly curious about the process which was used to reach this conclusion -- we're talking about half of the amplifier's available power. Regardless, I get it, there's no free lunch -- but the issue was whether the amplifier was "working harder" or not. You maintain that an increase in current demand from the amplifier equates to making it work harder -- well, maybe with your amp.

I just read that the purpose of the output transformer is to match the tube's output to the loudspeaker impedance, which is why there are taps coming from the transformer's secondary so you match the different impedances. I also just once again read the great article by Transcendent Sound on output impedance -- everything I've read and learned indicates that what makes a SET amp "work harder" is a mismatch in impedance between the output transformer/tubes and the loudspeaker (load). To be honest, I'm a bit out of my realm here when it comes to the tube amplifier end of things, so I'll go ahead and just concede the point. However, I don't believe a 2a3 based amp drops to a 1.75wpc amplifier with these networks. Aren't SET users really chasing the perfect first watt? Sounds like I'm in there regardless.

It may or may not surprise you to learn that I don't always recommend these type networks to SET users unless 1) they tell me they don't like the sound with the stock networks, or 2) they plan on experimenting with different drivers and horns -- in which case having the ability to attenuate on the fly is not just a useful or interesting feature -- but a necessary requirement.

SET users are normally minimalists and prefer the less is more approach. I appreciate that. I've made no secret of the fact that my personal favorite network is the PIO Type A. I've had the Wright WPA 3.5s in my house as well as the Wellborne Apollos -- and I preferred the Type A with both. At any rate, customers are individuals, each with a unique set of requirements based on many factors, and I may or may not suggest a constant impedance design to someone.

How and why did cables make their way into this discussion? I've never said cables don't make a difference, I just don't think they make as big a difference as what the network is built with.

"When you step on the gas pedal of your car is the engine working harder the more you step on the gas? If you load the car down with more weight does the engine work harder? So it is when we ask the amplifier to deliver more current and yes eventually you will reach it's design limits."

The car analogy has been attempted before. I believe Bob once told me that using the swamping resistor is like having the engine put out a constant 100 horsepower and controlling the speed with the brakes. I kept Al's response to that one, and I think it applies equally here.

"Your automobile engine is a bad analogy, but trying to relate it to this case, a gas engine is not a constant impedance source like a power amp. In a mechanical system, low impedance would be high torque at low RPM. High RPM at low torque would be high impedance. As you know, a gas engine has a curve where torque comes to a peak. It will not provide constant torque at all RMPs. A stereo amp WILL provide a constant voltage at all currents. A gas engine in a car also requires steps of impedance transformation (it's called the transmission and a torque converter) to transform that peak torque RPM to varying road speeds. That's an impedance transformer! Consider what the "transmission" would be like if your engine would put out constant torque at all RPMs. You would not need a transmission at all! You would pick a single gear ratio for all speeds. Besides, if a power amp can easily deliver 100W into a woofer, it certainly doesn't mind delivering 2 or 3W instead of .02W at 2000 Hz! The power drawn by the swamping resistor is peanuts in comparison to what the woofer draws. I use a 10W resistor and it doesn't even get warm unless you are trying to annoy the neighbors! The power requirements on your amp at squawker frequencies is nothing compared to woofer frequencies. Trying to use your gas engine analogy again, that's like bitching about your car's air conditioning drawing power from your engine and messing up your gas mileage when keeping your windows closed reduces aerodynamic drag and actually increases mileage! "

What matters is the acoustic response -- the sound.

I appreciate all of the comments.

[Deang]

I actually understood most of that -- more progress. Thanks!

That's why I said doing more of which is was designed to do. "Doing more" may not be "working harder", but Mike makes a valid point nonetheless.

[Marvel]

I would think, even though a bit less efficient, that my 2A3 amps would be better matched to the speakers if the impedance seen through the crossovers stays more even. Not necessarily 'ruler flat'...

Bruce

[Marvel]

Dean... I need another address. Billy has agreed to jump out of line for now as his work load is through the roof.

Bruce

[BEC]

Here is what Paul Klipsch had to say about impedance. He was defending the use of the autotransformer which raises impedance instead of using resistive attenuation.

Bob Crites

DFH Impedance.pdf

[Marvel]

Just to add a couple of pics. Crossover on the left is the battery biased AA sent to me by Speakerfritz, the one on the right is Aletheia Audio's Super AA.

Bruce

[Deang]

The network on the left gives me heartburn. The network on the right gives Bob heartburn. It will give Al heartburn too since I didn't use Litz inductors. Okay Bob, with respect, using the resistive pad, TIM is -76dB down, and we should be worried about this why exactly? Besides, I thought it was your position that this type of low level distortion is swamped by other, higher level forms of distortion (diaphragm, etc.). There are advantages and disadvantages to both methods and what's cool about Al's way is that he uses both (autotransformer and resistor) to provide great sound and a very useful feature. Also, remember what Dennis said about this topic, and I don't think that issue should just be swept under the rug either. Al's short paper on the advantage of using the swamping resistor: http://www.alkeng.com/dload/swamper.pdf

[Deang]

I didn't want to say this, but so far, every person who has heard the hacked version (using parts left over from old projects and entry level capacitors) has placed an order - and people aren't playing around either - no one from the roadshow has purchased the base version. Here are Tom Keady's, who incidently does the casework for Craig's units.

[BEC]

"Okay Bob, with respect, using the resistive pad, TIM is -76dB down, and
we should be worried about this why exactly? Besides, I thought it was
your position that this type of low level distortion is swamped by
other, higher level forms of distortion (diaphragm, etc.)."

Dean,

That was PWK, not me. You know he was all about low distortion even to the expense of everything else. I just say, why does anyone want the impedance to stay the same all across the three (or two) drivers in a speaker. What exactly do we gain from that, (leaving out the ability to adjust outputs easily for a moment)?