sound practices reading club /49

From today we will be dealing again with speakers, after a couple of first stabs, it is now time for refined choices. And you can’t get more refined than a pair of Quad electrostatics. We are reading Good Old QUADs by Haden Boardman, from sound practices issue 7. In it, Haden introduces the original Quad electrostatic, then moves on to their cons and pros. After advising what you should pay for a pair of Quads (in 1994), he troubleshoots everything that can and will go wrong with an electrostatic. The final section of the article is Haden’s guide to Quad tuning.

teaser quote: ‘There are few, if any loudspeakers that raise as many passions as the QUAD electrostatics. Like the DECCA cartridges, Linn LP12, Tim de Paravicini, LS3/5a and other quirky Brits a relationship with a pair of QUADs is either [a] pure love or pure hate relationship.’

my take
The Quad electrostatics are one of those rare products that created a whole new product category from the moment they were introduced. Yes, the technology existed for ages and products along the same lines had been released before it—and flopped. But once this product was introduced it ‘all makes sense’ and suddenly ‘everyone is making them.’ In this sense the Quad electrostatic is comparable to the Fender Telecaster, Fender electric bass, the iPhone and iPad.

Not very efficient (84dB/W/m I read) and difficult to drive too. Why is the Quad electrostatic featured in sound practices, and by extension, in the reading club? I had to ask myself that in the last couple of days. The answer is that there was never any doubt in my mind that this article should be in my reading club selection; Quad electrostatics belong to the ultra-fi world. Somehow I think that it felt the same for Joe Roberts when he decided to publish the article.

So much for intuition, now some rationale. First, looks like the Quads were designed with the good, old-fashioned idea of ‘get the midrange right (and the rest will follow).’ Second, the Quads seem to really need 15 Watts to sing (I read everywhere), so with the 7 Watts of a single 300B one should experience ‘close, but no cigar,’ let alone with 2W or so of flea power. 15 Watts, but not much more as Haden writes and also this charming, contemporary review points out:

‘Specific Amplifier Requirements

1. ‘When adjusted to a fixed suitable output tap, the amplifier should be capable of delivering at least 15 watts at low distortion when a resistive load is varied between 30 ohms and 7 ohms.
2. ‘The amplifier must be statically and dynamically stable completely regardless of the resistance or reactance of the load. An inductance of up to 10µH may be inserted in series with the load during these tests.
3. ‘With a 30 ohm resistive load, the amplifier should at no time be capable of producing more than 35 peak volts across the loudspeaker terminals.
4. ‘The source impedance of the amplifier should be not more than 2 ohms in the frequency range 100-5,000 c/s and not more than 6 ohms in the range 40-20,000 cls. Ideally this impedance should be equivalent to a 1–2 ohm resistor in series with a 40 µH inductance.’

And this requirement for a modest amplifier transports us back to the late 50s in a way, before or beside the power race. This is natural tube amp territory and I am sure the soft clipping also does not hurt either—literally. Looks like a worthy project to design an amp specifically for above requirements.

bonus tracks
See the role the Quads play in It Will Stand by Herb Reichert, and how ‘Arthur [Loesch] keeps a pair of of Quad ESLs as a reference’ in No Stone Unturned. And then there is next week…

practical note: how do these electrostatics work? Haden writes that the DC is on the rigid plate(s) and the music AC is on the flexible plate. The schematic in the article and other sources tell a different story: the flexible plate is charged with DC and is moved by the AC on the fixed plates.

Now go and read the article, see you next week.