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In Reply to: RE: ROGUE CRONUS MAGNUM KT120 INTEGRATED posted by tomzcentral@aol.com on January 30, 2015 at 17:38:50
It's a tube amplifier with different taps for 8-ohm speakers and 4-ohm speakers. Wouldn't a tube amplifier have a damping factor of one? I thought they used transformers to match the amplifier's output impedance to a speaker's impedance in order to deliver maximum power. If this is the case, its damping factor into 8-ohns from the 8-ohm tap would be one, and from the 4-ohm tap it would be two. Damping factor is speaker impedance divided by amplifier output impedance.
Best regards,
John Elison
Follow Ups:
Wouldn't a tube amplifier have a damping factor of one?
Not as a rule. Your formula is correct, but the output impedance is typically not 8 ohms even with highish SETs.
My VTL's range from between 1.3 and 1.7 ohms depending upon triode/tetrode setting giving you a DF between 5 and 6. Similarly, the Audio Research REF75/REF250 amps are around 8.
The Citation II Harman-Kardon amps have a damping factor of 18 or better.
.
Thank you.I guess my real question is,
How will the Rogue match up with a pair of Klipsch Cornwall IIIs?
Some encourage SS amps for this speaker but,I have a Magnum w/KT-120 tubes & thought it would match well with the Cornwalls....
Regards,Tom
My guess is that the Rogue Cronus Magnum KT120 Integrated would match well with Klipsch Cornwall III speakers. I don't know this for certain, but the Cornwall's are fairly efficient speakers and the Rogue Cronus Magnum KT120 Integrated seems to have more than sufficient power. Can you try the combination without committing to the purchase? If that's possible, I think its worth a try.
Good luck,
John Elison
Thanks John.
I agree.Power,isn't my concern.I was following a write up found on this forum about the Cornwalls.
The post had a link to a review of the Cornwall IIs.This guy really used hi-end test equiptment & measured different tolerances of the speakers.He compared a tube to SS & mentioned dampning factor & a certain area where the Cornwalls actually,put some serious load on the amp.In all fairness,the tube amp was a small Unison 2 (1 el-34 per side).
Anyway,I have a chance to get a pair of these speakers(of which I always wanted to try).I know,careful what you wish for,LOL!
Regards,Tom
The problem as I see it with tube amplifiers is that because of their low damping factor, voltage across the speaker will vary as the speaker's impedance varies. Frequency response will therefore increase when impedance rises and fall when impedance falls. Do you know what the impedance curve of the Cornwall III speaker looks like? I could find only the impedance curve of the Cornwall II. It looks as though the Cornwall II will play loudest between 1.5-kHz and 5-kHz where the impedance curve increases dramatically. This will give the speaker a lot of presence and also cause it to sound bright. It might not sound good to you.
If, on the other hand, you use a solid state amplifier with high damping factor, the voltage across the speaker will be constant and the frequency response will be much more uniform. With a solid state amplifier, there shouldn't be a rise in loudness when the impedance rises. You really need to audition the Cornwall speakers with your own amplifier to know whether or not you will like their sound. If that's not possible, you will either have to take a chance or else pass. I don't know what else to tell you.
Good luck,
John Elison
John,
Very well put.That is exactly what I thought after reading the same article.Thx again,I will call Rogue on Monday to verify the dampning factor in my amp.I was trying to stay with a american made speaker so,I was looking at the Cornwalls.
Funny,Hi-Fi Heaven sells the Rogue & points to the IIIs as a related product to use.In the past,I have had different tube amps from KT88 push pull & 845 set amps.The Cronus Mag w/KT120s tubes sounds closer to a SS amp(punchy) than any of my previous amps.
Regards Tom
...listen first. When I started to get serious about this hobby Klipsch was all I read about. I visited a dealer who carried all of them and sat for hours with all sorts of amplification driving them. I decided it wasn't for me, and then found out I'm not alone in that. Not attacking them and there's no shortage of fans, but they aren't for everyone.
That's why there is a dedicated upgrade path. Diaphragms, crossover, etc.
.
I'd rather have tubes with efficient Klipsch like the Cornwall.
E
T
My KT-120 based Cronus Magnum drives my not so efficient Thiel CS2.4 surprisingly well with great dynamics and clarity, even in a larger listening room.My concern would be noise or hum from a tube amp driving very efficient speakers, not that I've heard hum or noise from my Cronus Magnum, not even with my more efficient Tannoys.
Edits: 01/30/15
Yes, its a good amp. I'd lift the safety ground and do other things if noise were a problem. It is more power than one needs "generally" for an efficient speaker like that.
Rogue is nice stuff though in my experience.
E
T
Hi Abe,
Even though your CS2.4's impedance hangs around 3-ohms, it is exceedingly flat above 100-Hz as shown by the solid line in the graph below. In my opinion, it would probably sound very good with a low damping factor tube amplifier using the 4-ohm tap. The impedance rise in the bass region would bring out the bass and probably make it sound even better. Thiel speakers have some of the flattest impedance curves I've seen, especially in the region above 100-Hz.
Best regards,
John Elison
Good info. Thanks John. One of the first things I did when I got the Rogue amp was change it's output taps from 8 Ohm to 4 Ohm. It made a big difference with the Thiels.
Another data point would be the Cronus Magnum driving the Magnepan 1.7 speakers. In this case the 100wpc Rogue amp sounded a little compressed as in lacking dynamics and a bit flat or dead compared to a much more powerful SS amp.
We did this comparison at a friend's house using his large 300wpc SS monoblocks vs the Rogue tube amp. While the Rogue sounds great on my Thiels, it was struggling on the Magnepan 1.7s.
I'd be curious to know what the impedance chart looks like for the Magnepans. They sound great with more power but 100wpc from the Rogue tube amp was not enough.
> I'd be curious to know what the impedance chart looks like for the Magnepans.
Well, I could find only the MG1.6/QR. It has a big hump in the middle. It doesn't go below 4-ohms, but it goes up to 19-ohms at 600-Hz.
I think tube amps work better with flat impedance curves and very few speakers have flat impedance curves. Thiel is an exception to the rule as well as an exceptional speaker.
Interesting. Thanks! I've owned two Thiel speakers including the smaller and older CS1.5. That was my first Thiel and it did well with tube amps, as well as SS. Same for my CS2.4.
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