TAS 195: Spendor SA1 Mini-Monitor

King of the Midgets

For over 40 years Spendor has produced audiophile-grade loudspeakers. The new SA1 represents its latest thinking on small-footprint sealed-box monitors. Spendor has plenty of competition in this crowded category—I can’t think of many speaker companies that don’t make at least one mini-monitor. So how do the SA1’s stack up against all the competition? Splendiforously!

Built the Same, But Different

At first glance the Spendor SA1 speakers don’t seem dissimilar from scores of other diminutive wooden boxes stuffed with a pair of drivers and a crossover, but inside they are very different. The SA1 uses a SEAS 22mm “wide surround hybrid” synthetic-silk dome tweeter that allows for a longer throw with less distortion and more linear response at its excursion limits than a conventional silk dome tweeter. The new Spendor 15cm (6") diameter ep38 polymer cone midrange/bass driver sports a magnesium-alloy chassis, advanced surround material, and a large-excursion motor system. It is assembled entirely by hand at Spendor’s East Sussex factory specifically for the SA1. According to Spendor’s owner Philip Swift, “The 15cm drive unit has a flat frequency response up to almost 10kHz. So we are able to cross that speaker over at a high frequency (4.8kHz). We don’t have the crossover down at the usual 2kHz, which is generally the worst area of operation for the tweeter.”

The SA1’s crossover uses Spendor’s own precision-tapped inductors that are mounted on circuit boards with gold through-hole plating for better conductivity. Philip Swift believes that Spendor’s inductors are clearly superior to other types. “With the circuit topology we use in our crossovers, having the facility to design the inductors like this gives us tremendous control over the way we shape the frequency response of the crossover network. Using an analog crossover, as we do, you can bend or shape the frequency response in a very elegant way.” Spendor employs a second-order 12dB/octave slope on its midrange-woofer and a third-order 18dB/octave slope on the tweeter crossovers. To keep the two drivers in phase the leads on the tweeter are inverted.

Spendor employs a special methodology to mount its drivers to the cabinets, which its calls “dynamic damping.” With dynamic damping a rigid visco-elastic damping material is clamped between the drive unit chassis and the cabinet to dissipate micro-vibration. Any energy flowing into the cabinet from the drivers is turned into heat by this special material.

Silver-plated pure copper wire with halogen-free dielectric and gold conductors are used for all the internal wiring. Unlike many dynamic-driver speakers which employ a double pair of connectors to allow for bi-wiring, the SA1 uses only a single pair of WBT five-way binding posts, flush-mounted on the back of the speakers. Spendor doesn’t offer bi-wiring on the SA1 because it feels that it’s better to use one run of the best speaker cable you can afford rather than two runs of a lesser cable for the same total investment. Also the SA1’s two drivers have been balanced so precisely that using two different cables in a bi-wiring setup could actually degrade the overall sound quality.

While the SA1’s drivers and crossover include substantial amounts of proprietary technology, the speaker’s cabinet ranks as its most distinctive feature. The vast majority of speakers, regardless of size or type, rely on some form of mass damping to reduce internal resonances, but Spendor employs a different approach, which it calls “thin-wall damped panel design.” Rigidly braced, the cabinet is constructed with three different panel thicknesses. Each panel has a specific resonant characteristic, and their different natural resonances combine evenly to dissipate vibrations. According to Philip Swift, “‘If you make a cabinet four inches thick, what you’re going to do is push the coloration down to very low frequencies, but you are still going to hear it. Even if you do push it right down to the tens of Hertz, you are still going to get second and third harmonics of that. So getting rid of it, that’s the answer!” Spendor believes that the even dissipation of cabinet resonances through its thin-walled design is more efficient and effective than other methodologies.