Advanced Loudspeaker Application Development Project

Multiple-Degree of Freedom Cavity Resonator System

Project MCAP-CR

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 MCAP-CR Applications with Feastrex 5" Driver

Here are MCAP-CR application examples with the most fantastic Feastrex 5" driver. This is my challenge to highest quality loudspeaker systems.

There are three models in this page. You will find the newest model here.

D5e TypeII (Left) / Nf5 Ex (Right)
D5e TypeII (Left) / Nf5 Ex (Right)
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Feastrex's Full-Range Drivers

Feastrex is probably the most fantastic full-range driver manufacturer in the world.
It is located in Yamanashi, Japan. I recently found that this manufacturer exists in audio industry in Japan.

Feastrex supplies field coil magnet drivers as well as fixed magnet drivers.
I bought a pair of their Nf5 Exciter drivers. Nf5 Exciter is a 5" full-range driver with field coil magnet. It is their lowest priced field-coil driver model, still it costs more than three thousand US dollar per unit. It is exceptionally high price among all full-range drivers.
Regenerated sound from their drivers is really fantastic. I cannot explain how it is fantastic even in my native language. I dare to say it sounds like the minimum distortion of all I ever heard. And also it sounds clear as if we could "see" real sound itself. It does not require any tweeter drivers or woofer drivers with my original MCAP-CR enclosures.

Well designed enclosure is essential to make the best performance of Feastrex driver. Some enclusures are recommended by Feastrex. Pipe resonators by Mr. Tanaka were reported as good perormance. Also backloaded horn enclosures are employed by some Feastrex users.
I do not prefer their standard simplly vented boxes, because they cannot help regenerating lower frequency pressure waves. I think that one of the advantages of Feastrex drivers is that they are powerful enough to drive hard loaded enclosures like back-loaded horn or pipe resonator. I believe that the best enclosure for Feastrex's field-coil drivers is MCAP-CR.

Feastrex's Nf5 Exciter Driver with MCAP-CR Enclosure

MCAP-CR enclosure is recently developed by myself. It stands for Multiple Chamber Aligned in Parallel Cavity Resonator. MCAP-CR is designed to undertake multiple characteristic frequency. MCAP-CR enclosure consists of main chamber, subchambers, inter-chamber ducts, and open-air ducts. An inter-chamber duct connects main chamber and a sub-chamber. Thus MCAP-CR enclosure get multiple characteristic frequency. Detail of MCAP-CR enclosure is explained in the separate page (see this for more details).

The reasons why I think MCAP-CR enclosure is the best for Feastrex's field-coil drivers are:
I tested three MCAP-CR encloasure models with Feastrex Nf5 Exciter driver. Tested models were TR130b, TR130c and TR130d enclosures.
Each specification of enclosure models is in the following table:

Table-1 Specification of Each MCAP-CR Enclosure
Specification TR130b TR130c TR130d Note
Number of  Sub-chambers 3 3 3
Number of Ducts 6 6 6
Main Chamber Volume [L] 9.0 15.0 13.6
Sub-Chamber #1 Volume [L] 9.7 10.0 14.0
Sub-Chamber #2 Volume [L] 9.6 14.0 14.0
Sub-Chamber #2 Volume [L] 10.5 16.0 16.0
Cross-Sectional Area[cm2] / Length of Ducts[mm] 16 / 40
16 / 80
16 / 100
10.9 / 260
10.9 / 180
10.9 / 260		 21.2 / 50
21.2 / 92
21.2 / 110
13.0 / 120
13.0 / 150
13.0 / 240		 36.0 / 115
36.0 / 132
36.0 / 260
15.2 / 50
15.2 / 100
15.2 / 200		 TR130b was designed for Tangband's 5" driver W5-1611SA.
TR130c was designed for Feastrex Nf5 Exciter driver.
TR130d was modification of 8" enclosure model TR200a. TR130d's open-air ducts are located in rear side.
Characteristic Frequencies [Hz] 30
37
49
67
85
94		 27
37
49
60
73
96		 32
49
69
51
75
80		 Charactersitic frequencies of TR130b and TR130c were calculated using eigen value calculation, and ones of TR130d were calculated using simple estimation method.
Assembly Drawing Link
Schematics		 Link Link All PDF files.
See schematics of TR130b You will see the structure.
Remarks

* Tweeter driver Fostex FT96H is installed to TR130d; however, this tweeter is not connected.

It was difficult to say which the better enclosure after listening music sources.

TR130b is the smallest enclosure of the three, yet showed best matching with Nf5 Exciter driver. Excitation voltage with TR130b may be lower than with the other two. I preferred 10V for most music sources, but 14V was better for "Rite of Spring" by Stravinsky. High frequency like strings with TR130b sounds really vivid compared with other two enclosures. 31Hz pipe organ sounds really strong, yet a little less strong than other two drivers. TR130b may be the best of all three.

TR130c was originally designed for Nf5 Exciter. It showed good performance with Nf5 Exciter. TR130c with Nf5 Exciter sounds more flat frequency responce than TR130b. On the other hand, high frequency like strings sounds a litte supressed compared with TR130b. 31Hz pipe organ sounds great with TR130c! Overall performance of this combination will be scored higher than TR130b and Nf 5Exciter, because TR130c sounds more natural.

TR130d was originally designed for 8" drivers as model TR200a; however, I became reluctant to hear Fostex's 8" driver FE206Sigma, after becoming owner of Feastrex Nf5 Exciters. Performance with Fostex was not bad, rather very good, but I cannot compare Fostex with Feastrex. Resolution of music sound with Fostex driver sounded a bit rougher.
Remodeling TR200a to TR130d resizing open-air ducts, fantastic loudspeaker system was born! Every music sources became live and low frequency sounds strong. 31Hz pipe organ sounds strong enough. My impression of TR130d is similar to TR130c; TR130d has sub-buffle to install 5" driver where 8" driver was installed. This made Feastrex D5e drivers possible to install. Feastrex D5e driver has higher specification for sound maniacs as well as music fans. D5e driver has stronger magnetic circuit and ability to drive enclosure is much more than Nf5 Exciter driver. I do not afford D5e drivers, because price is more expensive than Nf5 Exciter drivers.

My overall impression of these three enclosure is:

TR130b enclosure is the most suitable for Nf5 Exciter driver. Excitation voltage for this system would be 10 - 14 volts, depending on which music we hear. 10 volts is enough for most music sources and 14 volts is suitable for some musics like Stravinsky. This TR130b enclosure is enough for Nf5 Exciter driver. Bigger enclosure like TR130c and TR130d have some advantage to boost low frequency; however, level of low frequency of TR130c and TR130d may be more than enough. TR130c and TR130d may be more suitable to higher performance driver D5e Type I / II / III rather than Naturflux models. This will be tested at Feastrex using TR130d enclosure.

Why don't you try MCAP-CR for Feastrex? You will be really surprized at the performance. MCAP-CR is true multiple-degree of freedom cavity resonator.


Model TR130b (above)
TR130b has one more open-air duct in rear side.


Model TR130c (above)
TR130c has one more open-air duct in rear side.


Model TR130d (above)
TR130d has three open-air ducts in rear side.

Also read newest Feastrex application model TR130e2.

  MCAP-CR is patented by Japan Patent Office (patent# 5083703).
  It is not for commercial use without contract.
  Try one of applications and make sure that MCAP-CR is good for highest-end applications, if you are interested in commercial use.

  This is personal small laboratory. Any kind of financial assistance is appreciated.
 
  Contact me at: mcapspeakers@gmail.com .

  Author: Shigeru Suzuki
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