As I recall the '63' has an impedence droop to 3.5 ohms in the bass. If so using a 16 ohm tap sould seem counterintuitive. I used a 4ohm taps with mine, but I never used a 16 ohm tap so I can't comment on any real differences.
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Sorry to disagree, but the ESL63 has an impedance that increases with sound level in the bass. At levels over 100mV the impedance never drops bellow 8 ohm in the bass. People usually measure impedance with a 1000 ohm series resistor, using levels between 10 and 50 mV, and assume that impedance does not depend on level. This is not true for the ESL63 and was published in the original HIFI NEWS review in 1981.
I have owned (and still keep) ESL63 and always used them with the 8 ohm tap of jadis, conrad jonhson and audio research tube amplifiers.
I believe the impedance of the 63's is north of 16 ohms in the bass and about 2 at 20k. That's why many amps roll over and play dead with'em.
Which tap to use is amplifier dependent. Experiment with your amp and make your own assessment. My ARC D115MkII sounds best with the 16 Ohm tap by far. I get tremendous bass response with this setup.
That's right Sbrown .. also my friend is getting tremendous bass response at 16 ohms taps but if you take a look at the Quad ESL63 impedance graphic ..
... you are gaining from 0 hertz to 600/700 hertz but you are losing from here to the 15.000 hertz and above
While theoretically with the 4 ohms tap you should gain between 600/700 hertz to the whole rest band expecially in mids and highs area .. the most important to our ears .. and where we have the most important part of musical message.
4est, you are discussinging the Quad ESL63 with the same ideas that are usually applied to electrostatics such as SoundLab and Martin Logan, but the ESL 63 is a different case. SoundLab and MartinLogan have impedances that can be as low as 1 ohm, but the ESL63 never goes lower than 4 ohm, being 5 ohm at 10kHz. Unless you listen to a lot of heavy rock and electronic music the power of music at frequencies above 5 kHz is much lower than average power - I have measured it with a spectrometer. Some versions of Shostakovich symphonies or some challenging test disks have peaks that are exceptionally rich in high frequencies, but most of the music some one typically listens in ELS63 is not a problem. Remember Peter Walker designed the ESL63 for the Quad 405 that was also current limited.
May be you prefer the 4 ohm tap because with this tap the damping factor of the amplifier is more adequate for your taste and listening environment.
I did some research and plenty of measurements on electrostatics because I own an amplifier that sounds lovely with electrostatics but it is current limited - the Dartzeel.
If someone has interest in the original HifiNews 1981 measurements I will be pleased to email them.
I'm happy for you Philjolet
We are trying the 4ohms taps on the JA30 KT880 monoblocks .. and as Detlof wrote above .. bad registered Cds sound really tiresome with disturbing highs
But apart this the Quad ESL63 sound more open and with unbeliveable largest soundstage than with 16ohms taps just loosing a bith depth
In few words at 4 ohms they are gaining from 500/600 hertz to the audible limit .. while they are loosing a bit the tight low frequencies we got at 16 ohms
in 4 OHM mine sounded a bit thin in the mids but the bass seemed to jump out more. I was trying to cut back on bass but now, in 8 OHM, bass is softer not fuller, and the emphasis is on the midrange, which I like
I realize this is a Quad post (so I will stop hogging your space) but it is just funny to me Audio Note speakers and Audio Note amps work this way together, I presume 8 OHM is the intended hookup
Well Guys .. it seems we are in consert to agree the best ohms taps for tube amps paired with Quads ESL63 are the 8ohms.
Now we (me and Opera) are curious to know if you have experiences with OTL amps driving these speakers.
We never listened or tried OTL amps (like Atmasphere) but theoretically .. based on electrical impedance observational .. should be the best choice even over the Tube Amps (not OTL)
What do you think about?
You will have to borrow a pair of Atma-Sphere amplifiers to try with the Quads.
Natural sounding vocals are very high on my list.
With good recordings the illusion of a physical presence in the room is startling with the Atma Speres amps.
I used the Atma Sphere M60s with a refurbished pair of Quad 63s for a few years.
Tenor OTL amps I have also heard on the Quad 57s, just astounding.
Years ago the late Harvey Rosenburg bought the rights to the Futterman Otl amplfiers, re-worked the amp and used them exclusively on the Quads.
The Quad 63 has always been a great match with our M-60 and MA-1 amplifiers. The speaker has an impedance peak in the bass that is well over 40 ohms and many amplifiers, especially transistors, don't make a lot of power at that impedance. OTLs, OTOH, once you get above a certain impedance (depending on the size of the OTL) will exhibit a sort of 'constant power' characteristic, so their output power does not drop significantly in the bass.
Unlike a lot of box speakers, the Quad's impedance curve has nothing to do with either crossovers or resonant peaks. It has mostly to do with the inductance of the matching transformer and the capacitance of the panel. The result is that a constant power characteristic in the amplifier is desirable if you want to get the most out of the speaker.
for more information.
With transformer-coupled tube amps, the trick is a moderate-powered amplifier that does not use a lot of negative feedback, usually set on the 8 ohm tap. With an OTL of course, you just hook it up. Since the 1950s, Quads and OTLs have always been the ideal match. The speaker is quite transparent and getting rid of the output transformer is very noticeable! Later Quads seem to be following the same path as Martin-Logan, by having very low impedances, in order to get them to work with transistors, but IMO/IME this tack never works- if you really use it with transistors it will be too bright and no bass. IOW tubes are still the ideal method with newer ESL designs but you have to use a set of ZEROs (http://www.zeroimpedance.com) to make them work.