The crossover is the heart of any high-end speaker design. The number of crossover topologies and options that are available to the designer are endless, and development of a successful design can take years of patient effort - even with the assistance of modern measuring techniques.

We have concentrated particularly on achieving an exceptionally flat in-room frequency response, especially off-axis, and superb phase coherence - especially through the difficult crossover region. This encourages optimum room response in the majority of listening spaces. Lenehan Audio loudspeakers have only medium efficiency, but their smooth and moderate impedance with low capacitive phase angle response throughout the frequency range presents a relatively benign electrical load. This enables the use of a wide variety of partnering amplifiers, either tube or transistor, though those with output power below 20 watts or thereabouts may well suffer a reduced maximum volume capability.

Let's first talk about the individual components that make up a crossover.

Inductors.

Our experience proves that inductors need to be air-cored, and as large a gauge as can practically be achieved. We cannot buy inductors that meet our high standards, so we wind our own - a time consuming process, as the tension in the wire must be kept low - and then double-stabilise them in motor winding varnish. Importantly, it also allows us to tolerance them to a precision that commercially-produced components could never match. Compared to the tiny, low cost examples that most manufacturers utilise, our inductors are vastly more reliable and durable, can handle enormous amounts of power, and have very low resistance and distortion.

As a general rule, a serious high-end speaker should use a bass circuit inductor that weighs at least as much as the bass driver itself. Otherwise, there is insufficient damping of the bass driver, which reduces the control that the amplifier has over the cone. Imagine a boxer whose glove is connected to his elbow with a rubber forearm - he cannot jab with speed or punch with power, and that's the effect of a typical small-gauge inductor.

In the ML1, the bass driver weighs 1.05 Kg and the bass inductor 1.2 Kg. We would happily acknowledge those rival manufacturers who also observe this rule of good audio engineering practice … but we don't know of any!

Capacitors.

Top quality capacitors certainly make an appreciable difference to the sound of the finished loudspeaker, but they don't come cheap! Have we made any compromises? Of course not!

We use only audiophile-grade metallised polypropylene capacitors from Erse.

Resistors.

Again, resistors are very important items and … you guessed it … using top quality components is absolutely crucial to the final result. How can that be?

Simply, normal commercial grade (ie. cheap) resistors compress dynamic range. Typically, they will have temperature coefficients in the 250 to 750 ppm (parts per million) range. Imagine that we have a resistor attenuating the tweeter in a loudspeaker. When a musical transient suddenly arrives and hits the resistor (as a sharp electrical pulse), the resistor will momentarily heat up and increase its resistance until that transient has passed ... at which point it can hopefully cool down again. The increased resistance, of course, works to compress the transient - just what we don't want. The higher a resistor's rated temperature coefficient (in ppm), the greater the temperature increase and the greater the compression.

At Lenehan Audio, we use only high power wire wound resistors, all of which have temperature coefficients in the 30 to 40 ppm range. This represents a tenfold improvement over the components typically used by our competitors.

Connections.

The easiest, quickest and most "cost effective" means of building a crossover is to solder the components to a PCB. But a soldered connection is far from optimal - solder is convenient and does the job, but it is a poor conductor, and PCB tracks are far from ideal for the best signal retention and transmission.

We have no interest in the easiest or cheapest methods; only in the best. All of our crossover components are hardwired, component lead to component lead, and crimped at high pressure to produce a low contact area cold weld. The joint is then sealed using Eichmann 5% silver solder. Connections thus formed offer the maximum achievable conductivity and stability, and will retain those qualities indefinitely.

The completed crossover.

The end result of our fanatical attention to detail is a crossover of truly exceptional build integrity, offering the following proven benefits:

• Consistent, stable, long-term performance
• Enormous power handling
• Superb damping and control of individual drive units
• Complete on- and off-axis frequency integration
• Amplifier friendly impedance and phase characteristics

Tolerancing and pair-matching the crossovers.

Designing a great loudspeaker is one challenge - producing it commercially is quite another! The problem is that all of the crossover components, and particularly the drive units themselves, have electrical properties that differ from sample to sample … and, to make things even worse, those values continue to change as the speaker settles down during its first 50-100 hours of use. The net effect is that, without careful adjustment of each individual crossover before and during this break-in period, some speakers in a production run will have a frequency response that differs very audibly from the designer's intention. Furthermore, it is absolutely critical to a stereo system's ultimate imaging and soundstaging capabilities that the output of each speaker is matched precisely, within a tolerance of +/-0.75dB.

So, how do our competitors manage to address these concerns? That's simple - they don't! Magazine reviews have shown in the past that different samples of even very costly, well-regarded speakers can measure quite differently; and if you're the customer who buys a poorly-toleranced pair, then that's just bad luck. Perhaps we shouldn't be surprised; after all, the time and effort consumed by burning-in, measuring, disassembling the speaker (possibly multiple times) and adjusting the crossover is a punishing and costly overhead for the manufacturer, all for a difference that the customer will never see. That's right - you'll never see the result of all that work but, be in no doubt, it's a difference that you WILL hear! At Lenehan Audio, of course, we have never spared any effort to ensure that every pair of speakers leaving our factory meets our design parameters (and we supply our speakers with an individual response trace to prove it!) … because we believe that's what our customers deserve. There was one small detail, though, that always irked us, as it was the only factor we couldn't control. Although we burn in our drivers before assembly, and adjust the completed speaker after the first few hours of use, it was still possible that the electrical properties of the crossover could change minutely while it continued to burn-in at the customer's home.

Now, though, we've come up with an approach that we believe to be unique in the industry - one that allows us to ensure perfect tolerancing and pair matching of our speakers, far more quickly and accurately than before. After being completely assembled, each speaker is burned-in on the workbench for 100 hours using music signal. Then, with access to the crossover provided by a tuning bay behind the Serial Number plate on the cabinet's rear, measurements are taken and the precise adjustments required are quickly performed - after which a fully burned-in loudspeaker, with a frequency response identical to our reference, is ready to be shipped!