Georgia Tech Audio Lab -Leach, 3-way Loudspeaker

Description

We have started with a recommended “baseline” for components. You may select upgrades or downgrades based on your preferences.

Recommendations:
Capacitors: The default for the single tweeter capacitor is from the Obbligato Copper Series, where the higher-tier capacitor will provide the most benefit.  The default for the mid circuit capacitor is from the JB JFX line, and the woofer (shunt position) starts with the JB JFGA, which is also a polypropylene capacitor. Additional options are offered, but capacitor upgrades are not critical for the woofer and mid circuits. The addition of bypass capacitors to those positions would be a more cost-effective gain, and the inductors on those circuits should receive upgrades before replacing the comparatively large capacitors with expensive upgrades.

The in-line tweeter capacitor should have first priority to receive additional upgrades. No “premium” upgrades are offered for the woofer and mid capacitors, as the JB JFX offered is already a high-quality capacitor. Upgrading those capacitors is best achieved through addition of bypass capacitors.

Additional upgrade efforts after the tweeter capacitor, should be directed to the woofer and mid inductors.

Note: the original schematic specifies capacitors of 40uF on the mid and 50uF on the woofer circuits. Those values are more common for cheap electrolytic capacitors, but less common in quality film and Polypropylene based capacitors, especially the 40uF variant. a 39uF is being used in place of the 40uF, which is a common and accepted substitution. The JFGA offered for the 50uF shunt position is a 47uFm the JFX is a 50uF. There is no negative tradeoff from any of these substitutions. The capacitors provided will be measured and paired to ensure they are as close to the desired value as is available, and any small variance is well within the manufacturing tolerances from the requested value. Even if selecting the 47uF JFGA for the stated 50uF position, that small variance will not create any perceivable change. That shunt role in the woofer circuit controls the severity or slope of the low-pass filter, and that tiny variance (very inaudible) would have only minimal but unperceivable affect upon the bottom edge of the cutoff slope. It is of no consequence and will not alter the frequency response.

Bypass capacitors: Small 0.1 uF bypass capacitors are offered as default for the woofer capacitor. Options are offered from the Obbligato Copper and Silver Series . These are high-quality, fast, clean, and resolving capacitors, representing a great value at $3.50 each for the Copper Series and $4.50 each for the Silver Series. You may skip this option, or may add bypass pairs for the large woofer and mid circuit capacitors.

Inductors: 18-gauge is offered as default in the tweeter circuit and is already a premium inductor which does not need to be upgraded. Larger gauge provides less benefit in the tweeter circuit than it will in the woofer and mid.

16-gauge is offered as default in the mid-circuit and woofer. For the most budget conscious, downgrading to 18-ga on the mid circuit would be completely acceptable. Upgrading the mid inductor to 14ga is not necessary and only for the true “top-shelf, no-limits build”. The woofer inductor should stay at minimum 16ga if possible, and 14ga would bring benefits, but should be second in priority, only after having upgraded the tweeter capacitor to Obbligato Silver Series or Clarity CSA, and having added bypass capacitors to the mid and woofer capacitors.

Abbreviated version: 18ga is plenty for the tweeter circuit. 16ga is plenty for the mid-circuit and down-grading to 18ga would be acceptable. 16ga is a strong baseline for the woofer, but upgrading to 14ga would bring benefits. Both can be done simultaneously, downgrading the mid to 18ga, and upgrading the woofer to 14ga, which could be a good strategy to maximize the benefit on the woofer, with minimal impact to the mid.

Resistors: We have kept it very simple here. High-Quality resistors are very affordable. We are providing GR-Research branded 10-watt resistors ($4 each). We don’t see a need for $30 boutique or even $10 versions in this design but if you feel that need, email us and we can modify a package for you.

Internal wiring: 15 ft of each color is plenty for any basic internal wiring needs for this design, connecting drivers to crossovers. You may also purchase the kit without our wire.

We do think our wiring is the best value available. It is a premium wire without the traditional markups. We offer 16ga solid strand, high-purity OFC, Polyethylene insulator, made in the USA. Wire details are here.

Crossover assembly options:   Complete assembly of your crossover boards is also available. $165 assembly fee includes the crossover boards and all small incidentals (zip-ties, heat shrink as needed), as well as the additional shipping costs, due to the larger packaging size. Assembly is for the pair of crossovers only. Assembly capacity is limited, with a 3-week estimated turnaround time, and is only offered as an add-on. For details related to our assembly services, review this link.