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February 2013 Issue
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World mail February 2013 issue

 

Write to us!  E-mail –>     This e-mail address is being protected from spambots. You need JavaScript enabled to view it

 

Letters are published first in the magazine, then here in our web archive. We cannot guarantee to answer all mail, but we do manage most!

 

Or  comment in the Comment section at the bottom of each page.

 

Your experts are -
NK 
Noel Keywood, publisher; PR Paul Rigby, reviewer; TB Tony Bolton, reviewer; RT Rafael Todes, reviewer (Allegri String Quartet);  DC Dave Cawley, Sound Hi-Fi, World Design, etc.

 

 

ELECTROSTATIC CABLES

My system comprises SME 10 turntable, Graham 2.2 Unipivot tonearm, Ortofon Jubilee cartridge, Leben RS 30 EQ Phonostage fed by 1:20 step-up transformers, LSA Standard Integrated amplifier and a set of Kingsound Prince 11 Electrostatic speakers.

   After reading your review of the Kingsound Prince speakers I saved up my pennies and bought a pair and can only agree with your review.

My question is one of speaker cables. You did not say what you used and if you tried bi-wiring as I have found it makes a big difference to them. I see you had some trouble getting any volume out of them but a company at www.sandersoundsystems.com seems to have the answers to some of the problems with large electrostatics. Their site is a mine of information regarding amplifiers and cables.

   I have found myself that cables do make a huge difference to the amplifier’s ability to drive them. I have tried many types, from shop-bought to home-made including normal 2.5mm twin and earth and flexible 2.5mm cables - they make it easy to drive the speakers but lose some focus. 

   At present I have a set of bi-wire QED 25th Anniversary cables in use which are a good compromise in being relatively easy to drive and giving a good sound. 

   Reading on the site mentioned above that a speaker cable with a low inductance and capacitance is a must for an electrostatic speaker as they act more like capacitors than inductors; hence the need for more volts, not current to drive them.

   I  know the company above sell cables but can you suggest a British company who could help? I have asked a few dealers but they tend not to do much with electrostatics.

Kind regards,

Robert Gardiner

 

The Kingsound Prince II electrostatic loudspeaker, a revealing design.

"Cables do make a huge difference to the amplifier’s ability to drive them"

says Robert Gardiner.

 

The need for volts is down to high impedance at low frequencies. Your (lovely) Prince IIs reach a massive 450 Ohms at 25Hz our impedance analysis shows, so a 100 Watt amplifier can push just 2 Watts into them here. But electrostatics are dramatic things; at 20kHz your Prince IIs have fallen from 450 Ohms to just 2 Ohms. Now, a 100 Watt (transistor) amplifier will deliver 450 Watts, or try to, possibly blowing up in the process.

   That's why electrostatics are difficult to drive: they demand high peak currents at high frequencies and this can blow power transistors, because current protection circuits in amplifiers are usually slugged so they don't operate too quickly, to avoid  relay chatter. It's an almost insurmountable problem for amplifier designers. So electrostatics do demand current – that's the problem with them. 

   Your Prince IIs are inductive up to 25Hz, resistive at 25Hz and capacitive above 25Hz. By 10kHz their impedance has sunk to residual resistance, probably from the step-up transformer windings. So they are not just capacitors, that is a too-simplistic model.  

   That closely spaced, parallel cables are inductive or capacitive (i.e. reactive) I am unsure – I have asked Chord to answer this. As a twisted cable pair has enormous analogue bandwidth and forms the basis of most high analogue bandwidth / digital data rate cables, from Ethernet through USB to HDMI, taking in Thunderbolt on the way no less, I can’t help suspecting that looking at the physical structure of a cable can be misleading. I suspect we will hear more about this from engineering readers or cable manufacturers! 

   All the same, that electrostatics need special matching cables is an interesting idea. We deliberately use very short cables around 1.5 metres long, from amps sited between the loudspeakers to minimise cable influence. I cannot recall what was used in our Kingsound Prince II review (April 09 issue) but I do remember that they were impressive electrostatics, if hard to drive. 

 

 

 

LSA Standard hybrid amplifier, a U.S. design that uses tubes and transistors.

It delivers 150 Watts per channel.

 

 

I have no experience of the LSA amplifier, but I see its transistor Class A/B output stage is rated for delivery into 1.3 Ohms (800 Watts!), and this suggests it has been designed with electrostatics in mind, the Prince IIs reaching 2 Ohms at 20kHz according to our measurements. 

   But Robert, I have never heard a transistor amplifier I would choose to use with electrostatics – and boy have I tried! Electrostatics open up and relax with a good valve amplifier and you hear into the music, rather than into transistors. No disrespect to the LSA, which looks like a great hybrid amp., but I would suggest you get a demo of a valve amp. sometime. As the Kingsounds are imported by Icon Audio, I am sure they can help you get a demo to hear for yourself. Their MB190 MkIIm monoblocks would be suitable. 

    Generally, look for at least 80 Watts per channel from paralleled KT88 power valves, or perhaps good quality KT90s / 120s. 

Valve amps have far less feedback than transistor amps, important when driving a capacitive load, and they shrug off a low load at 20kHz, where transistor amps can go into transient instability, current limiting or just blow up. But let your ears be the judge. NK

 

 

Icon Audio MB190 MkIIm monoblocks deliver 110 Watts and will drive

electrostatic loudspeakers like Kingsound Prince IIs.

 

 

... AND CHORD CABLES SAY

Comments on the Sanders Sound website are interesting, but some we would agree with and others we would take issue. Their comments about capacitance and inductance we agree with. With the work we’ve done with loudspeaker cables over the years we have come to the conclusion that there is a set of capacitance and inductance parameters. If the loudspeaker cables fall within this range, then to some extent their effect alone on the performance of the system that they are used in is pretty negligible. 

   We would also agree with their website in pointing out that cables that fall outside of these parameters will affect the performance, and particularly the tonal characteristics. These types of cables though are relatively unusual and the vast majority of cables fall within the parameters we have mentioned above. 

    Like you, we have an ongoing fascination with electrostatic loudspeakers. One of the most compelling demonstrations that I experienced of what an electrostatic loudspeaker can do took place at a dealer in Chicago. Without wishing to disagree with Noel about the merits of valve versus solid-state amplification, the system was an LP12, Naim pre-amp and 250 power amplifier, driving a pair of Quad ESL 57s. The song was “The Wind that shakes the Barley” by Dead Can Dance.  It was absolutely extraordinary.  

   I can obviously only speak from our experience so I can tell you that Chord Odyssey and Chord Epic are both extremely popular cables for use with electrostatic speakers and also valve amplifiers.  Auditioning both of these cables (manufactured completely in the UK) would let you hear exactly why we choose to use high frequency effective shields on so many of our cables, Epic being a screened version of Odyssey. In terms of measurement they strike a happy medium (or a good compromise) between capacitance and inductance. Both cables use multi-stranded silver-plated conductors, arranged in a twisted pair configuration.  

   There is another important point I would like to make. Obviously you have an extremely transparent set of speakers. Frankly, the better the speaker cable, the better the sound. I would suggest that you look at some of the higher end cables that are available. Better still, listen to them in your own system. From here I would echo Noel’s words – let your ears be the judge. 

Nigel Finn, Chord Cables.

 

Chord Odyssey 2 cable suits electrostatic loudspeakers, say

The Chord Company. 

 



 

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