Nuts & Volts - June 2007

SONIC REALISM

CENTER CHANNEL SPEAKER PARTS LIST

Qty. Description

■ 1 8” speaker three-way Pyle PLG8.3 (no Thiele/Small parameters available) from MCM (#51-1157) about $46/pair, 200 watts RMS

Allpanels are3/4” maple plywood, measurementsare outside dimensions, Top, bottom, and side panels have 45 degree miter cuts on two sides (see Photo 4). ■ 2 Front/back panels: 10” x 14. 5” (front panel has speaker cutout as required) ■ 2 Side panels: 16” x 8”

■ 2 Top/bottom panels: 8” x 11. 5”

Internal corner members ■ 4 6. 5” long 2” x 2” (nominal) pine (1.5” actual) ■ 4 1.5” x 11. 5” x 3/4” plywood ■ 4 1.5” x 7” x 3/4” plywood ■ 50 1.25” drywall screws (approx.) ■ 25 2” drywall screws (approx.) ■ 4 Speaker mounting screws ■ 1 Wood glue ■ 4 Rubber feet ■ 1 Speaker terminal

fact, the clearest example that, under certain circumstances, sonic reality can be achieved. It should be pointed out that the entire room was visible as she entered, so it was impossible for someone not to be seen. Additionally, the room was on the

second floor and she turned to look towards the outside wall. There was no speaker there.

Recording Hints

Not all recordings provide the

same realism. It seems that the simpler recording techniques, the better. Voices generally sound best if they are natural and free from electronic enhancement. Keeping the microphone about two feet away from the singer helps to create a more natural mix of high and low frequencies (less obvious pops and hisses). If possible, record individual instruments and voices with a single microphone or channel. For multiple people and instruments, use two closely spaced but directional microphones; one for the left and the other for the right channel. Multiple microphone mixing doesn’t seem to work too well.

There are several current commercial recording concepts that generally produce good results. These are “Binaural” recordings that use a facsimile of a human head with microphones buried in the ears. The other is the “Qsound^TM” from Archer Communications. There may be additional techniques, as well. However, it is difficult to find recordings grouped by the engineering technique.

BURIED TWEETER SPEAKER PARTS LIST ^■²Qty. Description

■ 2 Woofer speakers: Sony Xplod XS-L121P5, 4 ohm impedance, Rdc= 3, 2, Fs= 26. 4, Qts=0.42, Qes=0.44, Qms= 5. 86, Vas=1.96 cu. ft. Rated power=350 watts RMS, 1,200=watts peak, weight= 20 pounds.

■ 1 Tweeter driver: Motorola/CTS KSN1142A, 1.8 kHz-

30 kHz. Rated power=400 watts RMS.

■ 1 Diffraction horn: 10-5/8” x 3-7/8” x 7-1/4” with

1-3/8” diameter threads @ 18/inch # 54-290 from MCM ( www.mcminone.com)

■ 1 Crossover network (see Figure 1)

■ 4 Main vertical struts: 3/4” x 1.5” x 50. 5” (actual) maple

Side mounting arms: 9” x 4. 5”

All internal corner members are made from 2” x 2”

(nominal) pine (1.5” actual).

■ 8 Front/back members: 14. 25”

■ 8 Side members: 10. 5”

■ 1 Speaker terminal

■ 100 2” drywall screws (approx.)

■ 30 1.25” drywall screws (approx.)

■ 20 Speaker mounting screws (approx.)

■ 1 Wood glue 8 oz. (approx.)

■ 10 ft. “Frost King” vinyl foam weather-seal self-stick tape 3/8” wide, 3/16” thick (approx.) (see text)

■ 1 Grill cloth: 9. 25” x 60” (approx.) (optional)

■ 4 Mounting feet

All panels are made from 3/4” thick maple plywood. Measurements are outside dimensions. All panel edges (exceptthoseatspeakeropening and the woofermounting panels) are cut to 45 degrees.

■ 4 Front/back panels: 17. 25” x 21”

■ 4 Side panels: 15” x 21”

■ 2 Top/bottom panels: 15” x 17. 25”

■ 2 Woofer panel: 13. 5” x 15. 75” (with proper cutout for woofer)

Tweeter mounting pieces are made from 3/4” thick plywood, square cut edges.

■ 1 Back panel: 9” x 17. 25”

Materials/Parts Center Channel Speaker The center channel speaker is a more conventional box design ( 11. 5” x 16” x 8”). It is much easier to build and costs much less. The speaker selection was more arbitrary than for the buried tweeter design. Photos 3 and 4 show the basic design and construction method. A table saw is not required but it is helpful. Actual dimensions can be varied to some degree. Because the speaker has a four ohm impedance, a four-ohm resistor was added in series to increase the impedance to eight ohms. If your center channel amplifier can drive four ohms, then this resistor is not needed.