Bob, Dean, and Al... x overs

[John Warren]

alk goes on and on about "constant" this and "constant" that.

it's all on the signal side.

For loudspeakers, the criteria is "constant acceleration" of the acoustic mass since the acoustic mass is essentially constant for most loudspeakers. That's how you get a flat frequency response. This criteria places boundary conditions on the input signal.

the alk imposes a "fixed" impedance onto the amp. How does this design topology, used to optimize the conditions in microwave transmissions "alter" and "effect" the constant acceleration rqmnt for flat frequency response?

[sunnysal]

The only benefit I can think of for constant impedance in a crossover network would be as an easier load for a tube amplifier to drive, this can have positive results in system´s sound (and health).

BUT

If one choses as a design goal flat impedance then I cannot see a positive correlation/result for speaker/transducer frequency response.

They seem to me like two different approaches, optimizing the impedance presented to the amplifier and optimizing frequency response of the speaker.

No?

Tony

[Al Klappenberger]

Guys,

There is two seperate things goin on here. The first is a natural tendency for a conversation (which these threads really evolve into) to progress from one thought to another. It's normal to digress from the original thought. You just need to look back once in a while at the original thought to see what it was you stated talkling about in the first place!

The second thing is a person who knows a lot of quotes from experts that he has read about and has them all memorized but doesn't understand a bit of it but thinks he does and starts to inject unrelated stuff to make the conversation digress even faster! This reminds me of my mother. she had a heart of gold and a head of wood. She was a Jehovah's Whitness and had all the teachings of her church memorized. She didn't understand any of them but would recite them perfectly every time you tried to talk to her about religon. You quickly learned to avoid the subject. An intelectual conversation was impossible. It was like talking to a tape recorder. She whould simply "Play" one of her prerecorded lines no matter if it answered you thought or not!

Al K.

[John Warren]

I'm done with this discussion.

That should make you happy Al, you can go back to pontification without substantitation.

Tony-

You are asking the relevant question.

[dodger]

Al,

You are correct in the transitition of the thread.

In a manner this would be a nice topic for General Questions so that more could read the amount of work involved.

That is also for Dean and Bob also.

There is enough with Tony's question to split two more threads off and keep them here in Technical.

John your input would be welcomed also.

If we could keep a relaxed non-personal thread, that would be even better.

But in the absence of that, Dean, Bob, Al for whatever you all feel it's worth I thank you and I am sure that others that have read the question, the answers and if inclined, the beyond.

For all of you, your time is appreciated.

Win dodger

[colterphoto1]

Gentlemen,

Kindly return to the root of this thread and ask youselves, 'have we answered IndyKlipschFan's question?'

I believe he was asking for a simple explanation of your methodology, costs and impact on the sound. He, like myself and probably several others, have numerous Heritage speakers and would appreciate a non-engineering, simple manner to compare the various crossover update approaches.

Much of this thread is way above my head and I consider myself a fairly sophisticated listener and audiophile. No I cannot rebuild a Crown amp to 300 watts per channel using only a ding-dong wrapper, but I do know which end of the soldering iron to hold.

Thank you.

Michael

[Speedball]

I bet they gave him something to think about.

[sfogg]

Tony,

"The only benefit I can think of for constant impedance in a crossover network would be as an easier load for a tube amplifier to drive, this can have positive results in system´s sound (and health).

BUT

If one choses as a design goal flat impedance then I cannot see a positive correlation/result for speaker/transducer frequency response."

Actually one of the main reasons you want a flat impedance to a tube amplifier (or any amplifier with a highish output impedance) is so that the amp and speaker don't interact with each other and alter the frequency response of the signal coming out of the amplifier before it even makes it to the speaker by effectively creating a voltage divider between the two.

Transcendent has a decent explanation of this here:

http://www.transcendentsound.com/amplifier_output_impedance.htm

Shawn

[Al Klappenberger]

Guys,

To try to address the question that started this thread directly I will try

to sum up MY thinking in terms of guidelines for selecting which network

upgrade to go with. I don't like people trying to tell everybody what my

thinking is and I apologize if it get it wrong trying to give an overview of

someone elses. With that having been said, here goes:

1 - If you want to stick with the original PWK type AA design and simply

believe that your 30 year old AA network simply needs its capacitors replace,

I recommend Bob Crites switchable A to AA clone. As Bob has said, the

components he uses are quite adequate for this design. Wasting money on fancy

parts like Hovland MusiCaps and spiral inductors is a total waste of money.

Using them for the 13 uF capacitor has been tried many times and makes no

audable difference at grate expense. The spiral inductors in particular are

WAY overrated in general. The losses are lowest at the WRONG frequency! When

you do this kind of substitution you are looking for an "upgrade". That isn't

the AA!

2 - If you want an upgrade but you subscribe to the "Less is more" school of

thought, you want the DXA network designed by John Albright and built by Dean

Wescott. It is a true, 1st order multiplexer. If I had designed it, it would

have come out almost exactly the same way.

3 - If you want a higher order network that is still in keeping with the

"conventional wisdom" of 6, 12 and 18 dB / octave slopes and where careful

attention has been paid to what specific parts need to be first quality. Then

you want my "Universal type A replacement".

4 - If you want to blow your wad on the best there is, I believe my extreme-

slope networks are what you want. These are true, constant impedance

multiplexers. They virtually eliminate interference between drivers and

therefore the need for "time alignment". This results in the best stereo

image possible for a 3 way loudspeaker.

Al K.

[3dzapper]

Al, That is probably the best post in this thread. Definative without complicated technical jargon.

[BEC]

Al,

Good post. I might add, that rebuilding your old AAs using good caps is also an economical way to get most of the gain in performance. That is inexpensive and I would encourage people to first give PWK originals a try when they are back in spec so that they can see what the old Heritage speakers sounded like when they were new.

If you are using original type A or AA crossovers, you are not hearing them sound as good as they can sound because the caps have gone resistive with age. I have rebuilt dozens of pairs of AAs and have NEVER found a good (on ESR) 2 uF cap in any of them. Most of the old ones have around 2 ohms of ESR in the tweeter circuit.

Bob Crites

[colterphoto1]

Thank you Al, that was very clear.

You spoke of the components and design philosophy, what audible changes could be expected? I understand that this might be somewhat subjective, but as a designer, what results are you shooting for?

I have Cornwalls with the B networks, would the changes be approximately the same for me?

1. simple repair/replace out of spec components (capacitors)

2. slight redesign with higher quality components

3. massive redesign with highest quality components and different xover slopes

I get confused with the nomenclature used A, AA B and numbers are Klipsches original identifiers, right? Then Al and ALK are your designs, on license to Dean, correct? Do you have a redesigned B type for Cornwalls?

Thanks,

Michael

[Colin]

yup. great post ALK!

are they B or B2 Micheal?

B2s defitely need correcting...

[dodger]

Thank you Al.

This is what I had asked for earlier and had tried to elicit.

There is one question that now 4 people have asked me to re-post - I don't know why, it has not been answered or touched upon yet:

Do ANY of you feel that it is more needed to worry about the K-Horn, Belle or LaScala crossover than the other.

Or do you all feel that it is of equal importance?

Thank you all for your participation, your answers, your time and thoughts.

Thanks,

dodger

BTW: Dean you have a PM and Email.

[colterphoto1]

Colin, I have B3 for my 85 set of components, an original set from 1974 and 1963, so it's probably a pair of each I should imagine. The inductors on the 1963 are HUGE, looks like they were wrapped with massive 16 ga wire around an orange juice can, just enormous.

I have so many, I'm thinking of just doing Bob's repair work for starters and then see how it goes. I can always have more mods done later or perhaps replace some components on my own if the guys will share.

Michael

[BEC]

Dodger

I would say that it depends more on the type of crossover rather than the speaker it is in. A speaker with the Type AA probably benefits more from a rebuild or replacement of its crossover than does a speaker with a Type A. Simple reason is the higher parts count in the AA. More parts to go bad likely means more bad parts in an old crossover. Imagine some day when the AK-4 has some age on it.

Bob Crites

[Colin]

It is not only that $1 to 2K speakers are wirth the cost of the crossover upgrade, BUT also that thew commitment of the audiophile to put up with such big ole horns that require unique amplification and placement MERIT better crossovers than the stock or aging versions...

[Al Klappenberger]

Guys,

Weeelll......

Trying to get more specific about what crossover mods to make without getting

back into the technical stuff and in a general way can be tough. It is also

tough to do it without being totally subjective about it. Like I said

earlier, I don't want to try to explain somebody elses philosophy since I get

upset when people try to explain mine!

As far as predicting what you expect to hear with various changes is nearly

impossible. I think the addition of better quality parts simply reduces

losses. This tends to make everything louder and since most of the parts are

in the tweeter filter, a louder high end means a crisper sound. It also makes

for a tighter coupling between the amplifier and the driver. That, I think

should result in a "tighter" sound. But then, can you define "tighter"? I

really can't!

I also believe that presenting a constant resistive load impedance to an

amplifier allows it to work more efficiently and with a flatter frequency

response (as Shawn point out). This is probably of greater importance to the

guy with the lesser amp. I will get killed for saying this, but I believe the

SET amps belong in that category. If you have a two-million dollar mono block

rack-crusher on each speaker it probably won't make that much difference, but

it will not hurt! I suspect the resulting improvement would be a "smoother"

sound. Again though, define "smoother"!

As to the network types, there has been the "A" series, the "B" series and

the "E" series. The "A" series went in the Klipschorn (AA and the AK-_). The

"B" series went in the Cornwall. That was B, B2 and B3. The Belle Klipsch had

the AB, AB-2 and AB-3. Last but not least was the AL series in the La Scala.

AL, AL-2 and AL-3. Of these the dogs were the AL and AB. If there was an AK,

it was probably a dog too since I have never heard of it before! The E series

was in the Heresy, and I have paid enough attention to that one to list them!

All of the older ones suffer from age and the use of paper-in-oil caps where

crummy and still are even when new! All they do is create loss and make the

sound dull. Some people would call that "mellow". I prefer "dull"!

Al K.

[Colin]

nobody should kill you ALK for stating what tests show, that the response of tube amps ON speakers, not test benches, often reflect the impedance curve of the speaker, not the nice flat line of the amp!

[sfogg]

"I will get killed for saying this, but I believe the

SET amps belong in that category"

No feedback SETs absolutely have higher output impedances and will have greater frequency response swings into speakers that have varying impedance.

For example this is the FR of a Cary 300B integrated amp into a straight 8ohm load and then into a speaker simulator load which has a varying impedance.

As shown here:

http://www.stereophile.com/amplificationreviews/398/index4.html

Also discussed here comparing different amplifiers into the same actual speaker.

http://www.stereophile.com/reference/810/index.html

Shawn