PRECISION CROSSOVER ALIGNMENT

As anyone knowledgeable about speaker design will tell you, the crossover is the heart of the system. A crossover is an electrical circuit that separates the different bands of the audio spectrum and directs each band to its appropriate driver. All SP Technology products are designed with crossover alignments that include the "acoustic" response of the individual drivers in the final transfer function. Textbook approaches are never blindly taken as each and every design is painstakingly researched, repeatedly tested and modified to obtain the ideal summed driver responses. As much, if not more, time is invested in this single aspect of design as there is in any other area.

Filter theory has been researched extensively over many years and is now, for the most part, a complete science. It has been shown that each alignment has its own individual advantages and disadvantages. Our position is to use what ever works the best in a given application. While it is true that we prefer to use the Linkwitz-Riley alignments due to their superior phase properties, we will not be restricted by academics in our quest for excellence. From time to time we may choose to use other alignments as well -- form always follows function. Natural Law will not permit any other approach and we ARE bound by it both philosophically and practically.

It is a costly and very time consuming fact that we go to extremes in order to guarantee that every aspect of performance under the control of the crossover is optimized. Impedance compensation at critical points is always implemented. Often this has secondary benefits in the area of power handling that is often overlooked by those who consider such techniques to be of minimal value. Thermal time constants are modeled and conjugate solutions are implemented where appropriate and practical. It is at this point we will invoke our privilege and limit any further specific details as we are not intent on educating the competition. The final response is all that matters to you, the prospective customer, anyway.

We are philosophically committed in certain other technical areas though. One is that we insist upon "in phase" relationships between drivers at the crossover frequency. Theoretically speaking, there are certain alignments that are characterized by the fact that they do provide an in-phase relationship between drivers. The first-order Butterworth and the Linkwitz-Riley types are known to offer this advantage. That's one reason many engineers argue for their use.

We agree, but only from the standpoint that the final acoustic transfer function must exhibit this targeted response. In practice, textbook formulas almost never give accurate results. Some would argue that the point is moot and to a certain degree, we agree. We only make mention of the fact for the benefit of those that are of legalistic persuasions. In the end, all that matters is that the final response is in-phase. This requirement is often in stark contrast to many designs on the market.

It is a common observation that many consumers and apparently designers, believe that a flat frequency response on-axis is all that matters, overlooking the effects of dramatic frequency response variations off-axis. We do suppose that this might not bother some listeners who seemingly don't mind sitting in the "sweet spot," with their head in a vise. Objectionably, we can scarcely imagine paying good money for a loudspeaker that demands such a committed audience.

But even if this wasn't an issue, then an even greater problem occurs when the drivers are not in-phase. Whatever the entire radiated spectrum of sound may be, you can be sure that the surfaces of the room will be reflecting it. That energy ultimately returns to the listener in the form of a reverberant field. If the reflected energy of the reverberant field does not have a similar spectrum or "signature" as that of the direct energy from on-axis, a very artificial soundstage will be the result.

Many a novice and would be home recording engineer has found this out the hard way. It would be curious to know how many hours have been spent installing and then shortly thereafter removing most of the acoustic foam and egg cartons from the walls of garage recording studios. Countless young zealots have made the mistake of thinking they had to "deaden" the room to make a quality recording. A speaker that has a flat response on-axis but is not In-phase and has an erratic off-axis response will produce similar, albeit less dramatic of a response as the scenario above.

In stating this, we would be remiss if we gave the impression that a flat frequency response was not an important objective. Quite the contrary, a response free of significant frequency amplitude variations is vital in any product being promoted for professional use. Where we take issue is that with all of the modern analysis equipment at an engineer's disposal, it should not be as difficult as it appears it must be to achieve a flat magnitude response within the passband. To be honest, we're not playing fair here though. Our waveguide technology and its inherent linearity make it relatively easy for us to offer an extremely flat frequency response, amongst a few other critical characteristics.

Still, we never cease to be amazed at all of the exotic and highly priced systems being offered by others that exhibit mediocre (at best) linearity in their magnitude response. This might be acceptable if it was for the fact that tradeoffs were being made in order to provide improvements in say…the time domain or dispersion characteristics. All too often though, these same designs have little to offer in those areas as well. With such exorbitant prices being commanded, one would think (and should expect) that these products are nigh unto perfection in all respects.

It must be that a little silver solder, a few exotic crossover components, over priced drivers and enclosures made from the mass equivalent of depleted uranium … more than make up for these QUANTIFIABLE shortcomings. It could be just as true though, that there are many consumers with more excess disposable income than education or hearing ability. But that, dear ladies and gentlemen, is the beauty of free enterprise. We suspect there are many established manufacturers providing such consumers these wares. We also suspect they would struggle generating profits by any other means. Caveat Emptor.

But we digress. Let us just state the following and put an end to the rhetoric. The components used in our products are all of a "high grade" in critical signal pathways. Polypropylene capacitors, air core inductors and precision resistors are used where there is a benefit to do so. All components are hand soldered and inspected. Final crossover adjustment to achieve a response of +/- 2dB (typically +/- 1dB) is performed on the production line for each and every enclosure. A "Proof of Performance" graph of the magnitude and phase response is included with each enclosure.

CREATURE FEATURES

VALUABLE USER FEATURES

All SP Technology Loudspeakers products provide the end user with a convenient and meaningful set of features. A tweeter level control is provided on the back panel for use in accommodating the speaker to various environments. The user will find that it is a very useful tool when the speakers are placed close to the wall behind them. The amount of "boost" to the tweeter in order to compensate for the gain at low frequencies from the wall is the perfect complement.

This feature is included as a correction for the frequency response when the system is "soffit" mounted in a wall, as is the practice in recording studios, or simply located on or very near a wall in the home. A truly flat setting along with a very usable "cut" setting are both provided as well. That feature, along with a professional Neutrik ® "Speak-On" connector is included as our systems are designed for professional use as well as for in the home.

The positive lock that a Neutrik connector provides is an excellent safeguard against intermittent and accidental disconnection.

Bi-wiring capability is included by the use of individual gold plated binding posts for both the woofer and tweeter section. A relatively modest but inexpensive improvement can be obtained by using different interconnect cabling for each of the high and low frequency sections. Passive bi-amping may be realized using them as well and this offers substantial improvements if implemented properly. For further information regarding this configuration, we advise the customer to seek the assistance of a qualified SP Technology Loudspeakers dealer.