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trioid

Bi-amped Cornwall III's

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Greetings from AZ -

For those of us obsessed with experimentation,....last night I tried bi-amping the CWIII's. Those now have the double terminals in back ,and it is quite simple and easy to bi-amp.

Result: I paraphrase the wife* - 'I can can hear a 3 dimensional head singing right in the center'. 'The bass is nice and clean'.

* Character reference - she is not easily impressed. sings in a band, has a ba in music, and phd in biochemistry

Setup:

- triode strapped 6L6 amp hooked to the HF (running Class A, PP, fixed bias)

- Parasound SS current amp running the LF, output adjusted to balance with HF

(bottlehead FPIII preamp, Shanling tubed output CDP)

Try it if you have some spare equipment laying around - you might like it [:D]

jim

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Very intresting.

Some folks can hear a difference, others can not.

What is your amp setup and what type of wires did you use?

I just got done switching back and fourth from bi-wire to single wire, from lamp cord to premium wire for a period of about 2 weeks of each. On my ss setup, the bi-wire/premium cable sounded more open and detailed than single wire premium or any combo of lamp cord.

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Hi speakerfritz:

A brief history. Prior to the bi-amping experiment above, I did have the CWs bi-wired. I did not do enough comparisons to really answer if it make much of a difference. What I had (have) is 21 Ga magnet wire in a dual twisted pair. It is unterminated - no banana or spade plugs, just stripped and used as is. It sounds just fine. The magnet wire is not CCC, it is the stuff you can get from Antique Electronic Supply. Sometime i will get higher quality mag wire and make new speaker wires.

I will tell you this: the mag wire sounds one whopping bit better than the 'Munster' Cable (the thick grey rope stuff) that I had there before. Much higher detail level (also true according to the wife). Sure would like to have you give it a try if you are so inclined! It is a cheap experiment, but will probably take you an hour or so to get the wire stripped and attached.

The current setup: The HF portion (tubed amp) is the 21 Ga magnet wire. The separate LF is being run from the SS amp to the woofers via the old 'Munster Cable''.

I would like to stay tuned and hear about your results!

So far I am oK with the cheap mag wire, but someday will need to make some improvements. Right now that is especially for the LF range in the bi-amped version - Note that the new Cornwall woofer goes all the way up to something like 800 Hz, so one is well into a freq. range where quality counts. I need to get something better in there.

Cheers,

jim

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I have heard of using magnet wire but have not tried it.

I have also heard of using autoformers to increase the impedeance an amps sees. I have tried that, and have found most of the claims made to be consistent.

I re-call the magnet wire actually has vey high impedance, so it may also be a variant of an impedance multiplication concept.

What tap setting are your tube amp output transformers set to?

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Yes - the autoformers are still under consideration.

I am not sure about the impedance being high on the mag wire. It is just plain copper, with a heavy insulation. If you go look at the current carrying ablility of 21 Ga Cu, it is pretty high, and should be quite sufficient for this application. Resistance should be minimal for these voltages, currents and frequencies. (I guess, anyway)

Now, the tube amp is running just the HF, so I may go back to the 8 ohm tap on my amp and impedance should be pretty well matched.

By the way - these really are BI-AMPED. the new Cornwalls allow that from the configuration of the XO. That was confimed by Steve Phillips at Klipsch.

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Are you using an active crossover network?

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Nope - letting the passive XO on the CWs do all the work. Straight run from the SS to the LF terminals, likewise straight from the tube amp to the HF terminals.

I thought about an active, but why do that? The XO's (LF, HF which must be separated) in the speaker should be fine -- do you agree?

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Using the attached schematic to discuss (this is not the cornwall III schematic), when the bi-wire jumpers are removed (the 2 x's), you are seperating the woofer low pass section from the squakers bandpass and tweeters high pass section.

If you send full range sound to both the LP and the HP section, there is no place for the HP signal you sent to the LP section to go, as well as no place for the LP signal you sent to the HP section to go.

This results in an abnormally high impedance load seen by your 2 amps. On some SS amps, loads grater than 16 ohms, can cause some damage.

post-22082-1381930776631_thumb.jpg

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Agreed! That was why I talked with Klipsch support. The old style XO circuit would not work with bi-amping without modification.

They would not give me the new XO circuit.[:'(]. But, again, Steve Phillips, who is very helpful, assured me that bi-amping is A-OK with the new CWIII. [:)]

later

Jim

Oh, and by the way, I stuck a VOM across the two negative terminals on the LF and HF and found no connection. That is how this whole thing got started with the desire to bi-amp these things. Talk about one thing leading to a another (no pun intended).

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I sold my old cornwall 2's recently and am buying cornwall 3's. Any noteworthy difference in sound, quality built, etc. They weight about 8 pounds more.

Appreciate your feedback.

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Agreed! That was why I talked with Klipsch support. The old style XO circuit would not work with bi-amping without modification.

They would not give me the new XO circuit.[:'(]. But, again, Steve Phillips, who is very helpful, assured me that bi-amping is A-OK with the new CWIII. [:)]

later

Jim

Oh, and by the way, I stuck a VOM across the two negative terminals on the LF and HF and found no connection. That is how this whole thing got started with the desire to bi-amp these things. Talk about one thing leading to a another (no pun intended).

Very true.

Bi amping is not a problem as long as the LF and HF ckt are not common ground.

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Howdy Link:

Sorry, the CWIIIs were my first Cornwalls - can't compare with CWI or II. Can compare with several other types of satellite/sub and acoustic suspension speakers, and there is no comparison. They win every catagory.

You can look at the pictures of how the CWIIIs are put together. The fit and finish is excellent on mine, and they are solidly built from my poking around them. Check this out (if you haven't already) for further info on the bulid: http://www.cyclonecj.com/dtel/Dtelcorns-small/index.html

FWIT: I would buy them again in an instant.

Jim

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Keep your eye on the amp attached to the HF section. It may get hotter than normal, and may start smelling funny, especially if played at high levels

//////////////////////////////////////////////////////////////////////////////////////////////////////////

This is as simple as I can make it.

Lets focus on the portion of the audio band that is attempting to pass thru either the coil in the case of the LF section or the cap in the case of the HF section that is out of band. We will call this the out of band material since it is being blockec by an inductor or a cap and has no where to go. This becomes a reactive load (inductive or capacitive) and is reflected back into the amp. .

At the extreme end, consider a load which is completely reactive (i.e. inductive or capacitive). The voltage and current are 90 degrees out of phase with each other, and no power is consumed by the load - even though there is voltage and current present (and measurable). Assuming a voltage of 20V and a current of 2A, the actual power is zero, so the amplifier must dissipate not only the normal internal losses inherent in all power amplifier designs, but the 40 Volt/Amps reflected back from the reactive load. (Volt/Amps - or VA - is roughly equivalent to Watts - but only when the load is resistive, implying that work is performed).

If you review SS amp schematics, you will notice in most cases a 5watt resistor on the emmittor of the output transistors. The reactive load will probally disapate thru that 5 watt resistor until it fries, followed by blowing of the amp's output stage.

You can infer the likely hood of blowing the amp attached to the low pass section will be less likely since less out of band material is being reflected back due to the lower percentage of the audio material being in the high pass range. This means the amp attached to the HP section is at greater risk, since a larger percentage of the program material is actually in the lower band, which in the case of the amp attached to the HF section, is now out of band material and is being reflected back into the amp.

/////////////////////////////////////////////////////////////////////////////////////////////////

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Hi speakerfritz:

Thank you for bringing this up. It is a worthy concern and topic.

I believe you are addressing the issue of use of an active XO, prior to the amps. Using one of those would eliminate your concern. In this case we would need to use it at pretty high frequency, like around 600 - 800 Hz, I believe. If I were to do that, each amp would receive only the frequency spectrum for the speaker it was driving. For the HF section, > 800 Hz (nominal) and LF, < 800 Hz. Doing that is fine, but you do not want to run both the passive and active XO. You would want to bypass all passive XO components in the Cornwalls. I do believe it would sound great. Each amp would be doing only what it is called to do. It would sound better than letting each develop all freqencies and throwing away a portion of a audio spectrum.

However, as you know, I am using only the passive XO on the Cornwalls. Now, addressing the concern. (No one likes fried amps, and I am glad you spoke up!). I am not going to get into AC theory, or calculate phasors, or anything like that. I am in no shape to do that now. Here is my argument: The reflected portion of the band (< 800 or so Hz for the HF tube driven section) may provide some unwanted noise, but I do not think there is any significant additional power to dissipate. There is no load for the < 800 Hz frequency band; no load, no power that needs to dissipated. It is reflected 'stuff' that is not wanted and certainly does not help anything. It will create some small level of noise. That is my speculation. I have run these amps to pretty high power with this setup, and each is running as cool as ever, and not complaining in the least. And it sounds very tasty. Note that the tube amp has zero negative feedback, is transformer coupled, and the tubes are biased to class A anyway. In otherwords, it is already operating at near max plate dissapation even without music playing. I have rumbled the house with this setup, so that act should have pushed it over the edge and smoked if the amp if reflected power was an issue.

So - let's get more discussion and thoughts here, as I think this is very important, and not trivial. I sure do not want to fry my amps! Furthermore, I would hate to see someone follow this, try it, and fry their amps!!

Inputs? Opinions from experts in 'the electrics'?

Cheers,

Jim

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Sounds like you guys need to use Acurus and/or Aragon amps!

Bi-amping a speaker with passive network should not hurt the amplifier at all. There are many of us around here who have bi-amped for years with no harmful results USING passive xo. In fact, I talk to people daily that do this very thing. We have never brought an amp in for repair due to bi-amping. Unless of course a woofer shorted, xo issue, or another cause. The xo will typically cause higher impedance at the frequencies being crossed over, thus freeing the load on the amplifier, the main reason to bi-amp. Amps are affected in a negative manner when too much of a load is presented, 2ohm on an 8ohm rated amp that can't handle a 2ohm load.

Over 16 ohms will hurt a SS amp? How? What amp, and why? You do realize throughout the frequency response of many speakers, including KLIPSCH, the impedance reaches much higher than 16 ohms? Why would this cause the amp to get HOTTER? It should make it run COOLER. At least according to the tests we have performed and from our own experience.

Is an active xo better? ONLY if you know what you are doing, typically best left in the hands of a professional. Otherwise, it's likely you will end up with poor sound quality.

To sum it up: you should experience no problems bi-amping/bi-wiring our speakers and using the passive xo. If this were truly a problem, do you think we would offer the ability?

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I forgot to mention, if you tear apart one of our speakers to remove the passive xo to add and active xo, you will void out the warranty! If still under warranty, of course.

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Wow, I guess you learn something new everyday. I would never nor have never fed an amplifier full bandwidth and then put a passive xover on the output with one end of the spectrum unloaded. But then again I don't own anything new technology (within the last 5 years) I have seen what inadequate gauge speaker wire can do to an amp let alone being unloaded. I have used active xovers for years.

Speakerfritz, I would have agreed with your take on the matter, but then I am no expert

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Anyone who has ever connected an amplifier to one of our speakers has done this. The LF and HF are separate circuits. The LF does not send the higher freqs it xo to the HF circuit and vice versa.

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Anyone who has ever connected an amplifier to one of our speakers has done this.  The LF and HF are separate circuits.  The LF does not send the higher freqs it xo to the HF circuit and vice versa.  

That's the point. Once the bi-wire jumper is disconnected, the LF and HF are seperate circuts.

In the case of the HF, only place LF material has to go, is back to the amp.

In the case of the LF, the only place the HF material has to go is back to the amp.

Need to look at this from an amp perspective rather than a speaker one.

This is discribed in detail in my below post.

Take it under advisement, update your manuals if you think this is a good implementation, right now manuals only discuss bi-wiring using these terminals.

Klipsch has a lot of support mysteries especially when it comes to amplified products, pro-media line is good example, every day a new post about spooky stuff going on. I would not consider this implementation an amplifier best practice.

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You are stating this is going to harm the amplifier(s). It indeed should not. Is passively bi-amping the best way to go? Perhaps not. We know and realize this. However, there are those out there who want to and don't want to deal with an active xo. It's perfectly fine to do. Will there be an audible diff? Some think so while others do not. Some like to tube the top (HF) and ss the bottom (LF). So be it. It's all about preference. But, if you don't know what you're doing with an active xo, you will end up with poor results.

I see you've quoted Rod Elliot. As I stated to you, we are familiar with his work and his theory is valid, we have found in the real world, consumer applications, it does not present a problem.

If you want to see what we have available for anyone to see regarding bi-amping, look in the FAQ's. http://www.klipsch.com/customerservice/faq.aspx?id=20&view=9

You are cetainly welcome to have your opinion whether passive bi-amping is the way to go or not and by alls means give your opinion and help others set up correctly with an active xo, if you know how, but please do not state that SS amps are going get fried if you passive bi-amp. It's not the typical case and I've NEVER seen it with all my dealings with Aragon and Acurus amps. In fact, none of the engineers have either on the amp/electronics side OR speaker side.

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