building subwoofer with a spiral horn

The 3D-Spiral Horn Speaker Building

Subwoofers

Newly added on 25 Dec. 2004
Revised on 17 Aug. 2005
sub100-125-75

Helix-sub75, sub100 and Sub125
My audio system

Helix-Sub125


Helix-Sub125 is the subwoofer with two horizontal spiral horns and a 12" driver. The aim of Sub125 is to enhance the frequency region under 50Hz for compensating the performances of other Helix systems. The subwoofer used is DAYTON 12" TITANIC MKIII (Q_ts=0.44) . Box volume is the same as the vented subwoofer design by Parts Express with a modification of hight/width ratio. Electronic subwoofer crossover, PYLE WAVE PLXR2 is used for input to the power amplifier exclusively used for Sub125.

Helix-Sub125

Uploaded on 25 Dec. 2004

Subwoofer	DAYTON 12" TITANIC MKIII
Height	600 mm
Width	443 mm
Depth	463 mm
Outer tubes	length 325 mm class=VP125 (JIS) inside diameter= 125 mm
Inner rods	length 325 mm wood rod outside diameter=18 mm
Air chamber volume	76.3 liters
Rotation number of spiral horns	1.5
Rotation number of partition plates	2.5
Cross sectional area of throat	56 sq.cm x 2 = 112 sq.cm

PVC Pipe Specifications (JIS=Japanese Industrial Standards)

Spiral passage (Unit of length: mm)
•Thickness of plywood is 21mm. •Crosspieces for reinforcement are made use of other plywood. Volume of crosspieces are 7.3 liters. •Acoustic absorption materials used are Thermowool® and felt. •Terminal used is CU-T40 ( Tritec ).

Helix-Sub100

Helix-Sub100 is the subwoofer with a vertical spiral horn and a 6" driver.

The aim of Sub100 design is to reduce the volume of the cabinet without deterioration of the performance as a subwoofer.

The woofer used is HI-VI M6A 6" ALUMINUM/MAGNESIUM MIDBASS (Q_ts=0.43) .

The electronic crossover and the power amplifier used for Sub100 are the same as Sub125.

It is confirmed that the reproductive ability of Sub100 in the bass region is almost equivalent to Sub125.
In contrast to Sub125, the spiral horn of Sub100 is clearly beneficial.

Helix-Sub100

Uploaded on 23 Feb. 2005

Subwoofer	Hi-Vi M6a
Height	500 mm
Width	220 mm
Depth	320 mm
Outer tubes	length 360 mm class=VP100 (JIS) inside diameter= 100 mm
Inner rods	length 360 mm wood rod outside diameter=15 mm
Air chamber volume	15.0 liters
Rotation number of spiral horn	2
Rotation number of partition plate	3
Cross sectional area of throat	36.5 sq.cm

PVC Pipe Specifications (JIS=Japanese Industrial Standards)

Spiral passage (Unit of length: mm)
•Thickness of plywood is 20mm. •Crosspieces for reinforcement are made use of other plywood. Volume of crosspieces are 2.0 liters. •Acoustic absorption material is not used. •Terminal used is CS1/G ( Rit).

Helix-Sub75

Helix-Sub75 is the low-cost compact subwoofer with a vertical spiral horn, a 5" woofer and a subwoofer amplifier. The spiral horn has a long sound passage for extending lower-limit to 30 Hz.

The aim of Sub75 design is to strengthen further the aim of sub100 and to incorporate a subwoofer amplifier for improving usability of the subwoofer.

The woofer used is DAYTON RS125S-8 5" REFERENCE SERIES SHIELDED WOOFER (Q_ts=0.44) .
The subwoofer amplifier used is DAYTON SA25 25W SUBWOOFER AMPLIFIER . The low-pass crossover is 60 to 180 Hz. The required electric source is 120V, 60Hz.
Both parts were purchased from Parts Express.

Description	Qty.	Price
SUBWOOFER RS125S-8	1	$21.85
25W SUBWOOFER AMPLIFIER	1	$31.49
UPS Worldwide Express (from US to Japan)		$57.80
Total		$111.14

Sub75 is small, but can reproduce very deep bass, which is almost identical with sub125.
The setting of low-pass crossover is critical. The optimum crossover is 60 Hz. If it is raised to 180 Hz, integrated sound of H75 and Sub75 become boomy.

Helix-Sub75

Uploaded on 10 Aug. 2005

Subwoofer	DAYTON RS125S-8
Height	400 mm
Width	170 mm
Depth	250 mm
Outer tubes	length 315 mm class=VP75 (JIS) inside diameter= 75 mm
Inner rods	length 315 mm wood rod outside diameter=15 mm
Air chamber volume	7.8 liters
Rotation number of spiral horn	2.5
Rotation number of partition plate	3.5
Cross sectional area of throat	17.1 sq.cm

PVC Pipe Specifications (JIS=Japanese Industrial Standards)

Spiral passage (Unit of length: mm)
•Thickness of plywood is 15mm. •Crosspieces for reinforcement are made use of other plywood. Volume of crosspieces are 1.6 liters. •Felt is used as an acoustic absorption material.

A soft tennis ball as a damping material for bass region

Clarity of the low bass region of Sub125 was not good enough initially.
I tried to improve it by putting four soft tennis balls into the cabinet.
The results have been excellent. Transient attacks have had superior definition and clarity.

Tozawa resonator is used widely in Japan as a damping material for bass region. But, a soft tennis ball is easy to purchase and may be more effective.

Perhaps, I am the first person in the world who has discovered the new application of a soft tennis ball.

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