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A651

The A651 is a 2-way design using an Audax HM170Z0 6.5" HD-A woofer and an AW025S3 1" Aluminum dome tweeter. This enclosure is computer optimized for a vented QB3 type of response yielding an F3 of about 55 Hz. Although the A651 could have been placed in a somewhat larger enclosure and the F3 reduced to a lower frequency, this volume provides maximum damping for bass detail and produces an output of 100dB, remaining linear down to 40Hz.
CROSSOVER DETAILS

The crossover is also computer optimized (using LEAP 4.51) as a 4th order Linkwitz-Riley type at 3kHz which yields an overall efficiency of about 86.5dB. To achieve this, the low-pass section of the crossover incorporates a modified third order topography which produces a transfer function that begins contouring the woofer response at 200Hz. This technique is used to create an anechoically flat response up to 3kHz crossover frequency and then produces an acoustic slope that is between 3rd and 4th order. The high-pass section also uses a third order topography to achieve a 4th order acoustic response and is configured to produce a shallow knee in the high-pass transfer function. When other sections are summed together, the final response of the speaker is 55Hz - 19kHz +/-2.2dB with a very flat off-axis response profile.

SPEAKER LOCATION

The A651 speaker is designed to be placed on a high quality well damped speaker stand approximately 26" in height. This places the tweeter at 39" above the floor. Although the bass extension of the HM170Z0 is typical of many high quality 6.5" woofers and is more than adequate for most listening, this speaker makes an ideal satellite speaker for use with a powered subwoofer, or bi-amped with a separate amplifier and subwoofer.

CONSTRUCTION INSIGHTS

The enclosure is damped interally using acoustic foam (ACI foam or equivalent) placed directly behind the woofer covering the back and side walls from the area below the internal brace (which is placed between the woofer and tweeter) to about 1" above the port location. Additional damping material such as Dacron or Acousta-Stuf is placed in the upper area above the brace (sufficient to fill about 30% of this area with "teased" material) and directly behind the woofer (use enough material so that is is held in place by the foam and does not fall downward and interfere with the operation of the port). The port tube should be constructed of 2" ID ABS plastic pipe.