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I have asked VSA the following question:The manual says:
Impedance: 8 ohms nominal (Midrange/Tweeter). 4 ohms nominal (Woofers). 6 ohms average.
I am not a technical person, but from high school Physics, should the overall (average in your term) of impedance be calculated as:
1/R = 1/8 + 1/4
1/R = 3/8
R = 8/3 = 2.6666 ohmsThe overall impedance (2.6666 vs 6) is important to me in choosing a power amplifier.
But VSA seems not understand what I meant (was I wrong?) and just re-stated that, overall impedance is 6ohms.
Follow Ups:
I've got mine bi-wired with two pairs of single wire. I've got the tweeter/midrange hooked to the 8ohm tap, while the woofers are connected to the 4ohm tap. It all works very well for me.My amps are Canary CA160's--100wpc triode/140wpc UL--and I've also run the VR4jr's with 50 and 60wpc tube amps and a big 250wpc SS amp--all with good results. It was my experience with the big SS amp that convinced me I needed to try a high-powered set of tube monoblocks, which hit the spot for me. The VR4jr's have responded well to the more-powerful, higher-quality amplification.
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The crossover network effectively disconnects each driver out of its operating band so your amplifier only sees a single driver in each portion of the frequency range. The standard, parallel resistance calculation you performed is invalid for this configuration.If they say it's a nominal 6 ohm system impedance then it probably is.
You can generate an impedance plot of the speaker yourself but you need to add a resistor in series and then measure across it at various points throughout the frequency range and plot the results.
The crossover network raises the impedance of the tweeter section in the woofer's passband, and raises the impedance of the woofer section in the tweeter's passband. This is how the crossover keeps the out-of-band signals from reaching the drivers.The amplifier never sees the woofer and tweeter in parallel.
If it is any help to you, The VR 4JR's are easy to drive.
I have a pair, and so did my friend Kurt, until he went to Vandersteen 5A's.
I own the VR 4jr and agree that it's easy to drive.Just curious to know its actual impedance.
Um ... actually I'm thinking whether a 300B power amp can drive it.
A 300B amp will not drive them well, Coloration in mids and low power.
Ran canary ca 339 clipped the %^&* out of it at times.
With the variable impedance mentioned in even the manual/document you cite, which is far from telling how varied, this will not be the best pairing with a SET of the 300B variety. Wide swings in impedance result in wide magnitude of output across the frequency spectrum. Tap at 4ohm and bass might be good, but mid/treble could be wacked, Tap at 8 ohm and bass will most likely run out of steam
That is a good question ?
As you know, the VR 4 JR's are a pretty warmly voiced speaker.
As such, they really don't "need" a majic amp to make em sound good.
Like many dynamic speakers, they like some current to control the woofers.I ain't saying SET won't work, but I think that you might be better off with a nice sounding solid state amp, or a medium powered tube amp.
That is just my opinion, and I have not tried SET with the VR 4 JR's.
Probably only at background levels.......
Von Schweikert Jr. recentlty told me to not run dual runs of cable from Amp to the top and bottom VR Speakers.
Instead he said to run a single cable from my Amp to the top and a use a jumper cable from the top to the bottom.
He says that how they wire theirs.
Now , I wonder if he was referring to perhaps the impedenace thing you guys are talking about.
I didnt do it because he really didnt sound like he knew what he was talking about.
Was he on to something?
Thanks all for the information, opinions, and advice.
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