Multi-Flare Structure

The 3D-Spiral Horn Speaker Building

Added on 17. Jan. 2008
Updated on 21 Jan. 2009

Helix-MF140 : for 8 cm driver

mounted with PARC Audio DCU-F101W

mf140

mounted with SA/F80AMG

Helix-MF140 mounted with Fostex's 3" FF85K has a multi-flare structure with two front openings.
The sound passage has several turnoff points and flares like funnels.

A damping material was not used, but it may improve sound quality.
Apparently, smoothness of a sound passage is not essential for a good sound.
Rather, filtering out a higher region with kinks and flares formed by slanted plates attains high quality bass output.
The slanted plates may prevent a harmful standing wave.

The sound quality is similar to the "Z" series. But, MF140 is not boomy for a high Qts driver such as SA/F80AMG and FE87E. Therefore, the applicability of multi-flare may be wider than "Z" series.

For19 mm MDF, the gaps between the fins should be maintained.
The gaps are 5 mm (=20-15).
Then, for example, right hand side dimensions should be 30, 25, 99, 24, 64 and 24.
The total hight should be 304 (=280+4x6).
The upper dimension (30,25,110) can be increased.

The performances on a lower region are affected significantly by drivers.
The most superior driver is PARC Audio DCU-F101W, and the next is SA/F80AMG.
FF85K is inferior.

Although I did not try, someone said that TangBand, HIVI M4N and CSS FR125S were very good, but ALTEC and Fostex F120A were inferior for spiral speakers.

Details of MF140

Helix-HMF140 : for 8 cm driver

Added on 9 Jun. 2008
hmf140

mounted with Fostex FF85K

Helix-HMF140 mounted with Fostex's 3" FF85K has a "horizontal" multi-flare structure with a rear opening.
The sound passage has several turnoff points and flares like funnels the same as MF140.

A damping material was not used.

Details of HMF140

Helix-HMF170 : for 10 cm driver

Added on 20 Jun. 2008
hmf170

mounted with Fostex FE103E

Helix-HMF170 mounted with Fostex's 4" FE103E has a "horizontal" multi-flare structure with a rear opening.
The sound passage has several turnoff points and flares like funnels the same as MF140.

A damping material was not used.

Details of HMF170

Helix-HMF160 : for 8 cm driver

Added on 10 Nov. 2008
hmf160

mounted with Parc Audio DCU-F101W

Helix-HMF160 mounted with Parc Audio DCU-F101W has a "horizontal" multi-flare structure with a rear opening and a bigger cabinet than MF140.
The sound passage has several turnoff points and flares like funnels as MF140.

A damping material was not used.

The bass output of HMF160 is much superior than MF140. I feel no need for a subwoofer to boost lower region.
It is not clear whether the cause of the superior bass output owes to a bigger cabinet or to a different driver.

Details of HMF160

Helix-HMF160a : for 8 cm driver : improved version-a

Added on 28 Dec. 2008
hmf160a

mounted with Parc Audio DCU-F101W

The gaps of three flare necks are 8 mm, and 6 mm for the last (4th) one.

This is the improved version of the above HMF160.
The principal improvements were making "R" on the edge of the fins, and enlarging the angle of the flare a bit.
Other changes were displacement of the baffle hole and the rear opening respectively, and usage of an aluminum tube for cable insertion.

The same driver, Parc Audio DCU-F101W, was used.
No dumping material was used.

There was no major difference between HMF160 and HMF160a on the frequency characteristics, but it was perceived that there is improvement on the resolution of the lower region.
And, there was big difference on the impedance characteristics, but I couldn't interpret its meaning.

Details of HMF160a

Helix-HMF160b : for 8 cm driver : improved version-b

Added on 31 Dec. 2008

The gaps of three flare necks are 13 mm, and 8 mm for the last (4th) one.

This is another improved version of the above HMF160 with shorter fins by 1.5 cm than HMF160a.
The configuration of HMF160b is the same with HMF160a except it has wider gaps of flair necks.
The same driver, Parc Audio DCU-F101W, was used.
No dumping material was used.

The distinctive feature of HMF160b on the frequency characteristics is that the SPL of its higher region, 4k to 8k Hz, is lower by 10dB than HMF160a.
Therefore, the sound is mild without stimulating sensation.
The lower region has a sufficient SPL extended to 40Hz.

Details of HMF160b

Helix-HMF200 : for 10 cm driver

Added on 21 Jan. 2009
hmf200

Mounted with Fostex FE103E

The gaps of three flare necks are 8 mm, and 6 mm for the last (4th) one.

This is a scaled up version of HMF160a for 10 cm drivers.
The principal changes were the extension of the depth of air chamber by 10 mm and the expansion of the width of the box to 200 mm.
The angle and the length of the fins were not changed.

The measurement of the frequency characteristics indicated HMF160a was superior to HMF200 with bigger driver. It is not clear whether the difference of performance between HMF160a and HMF200 is caused by drivers or by box configurations.
I have tried to put DCU-F101W on HMF200 for clarification.

Details of HMF200

Helix-HMF200-test : Experiment with an 8 cm driver

Added on 21 Jan. 2009

How is the performance of HMF200 with DCU-F101W, an 8 cm driver?

The distinctive feature of Helix-HMF200 with DCU-F101W on the frequency characteristics is that the SPL of its higher region, 4k to 8k Hz, is lower by 10dB than HMF160a.
Therefore, the sound is mild without stimulating sensation.
The lower region has a sufficient SPL extended to 40Hz.
These features are analogous to HMF160b.

The lower backpressure caused by wider gaps or big volume may be the reason of the above features.

A driver with lower Qts, for example FE103E, may not be better suited for a Multi-Flare.

Details of HMF200-test