# Big D' s Folded Horn Speakers w Fostex Full-Range Drivers



## Big D

*MY DIY FOLDED HORN SPEAKERS WITH FULL-RANGE DRIVERS*​
After toying with different plans to build two speakers for my two-channel room, I finally decided to make two folded horn cabinets with 8" Fostex full-range drivers and Fostex super tweeters. I have owned many different type of speakers, but never a folded horn cabinet with full-range drivers. These types of speakers are ideal for music and two-channel applications, including tube amplifiers. I planned to use the speakers in my two-channel room and that was the main reason I decided to make them.

*Fostex Full-Range Drivers:*

Some of you do not know Fostex drivers. Fostex is a Japanese company and one of the largest speaker/driver manufacturers in the world. Most of their sales are for the OEM market. Although Fostex speakers are well known in Japan and Europe, they were never mass marketed in America. Fostex is one of the most well-known and well-respected makers of full-range drivers. Fostex speakers sound extremely natural and musical. They are by far the best speakers for two-channel music such as Jazz and Classical.

*With a full-range driver, there are no separate woofer, midrange, tweeter and a crossover is not necessary. Without trying to blend different sizes and types of drivers together, there is a purity of sound that cannot be achieved in multi-driver systems. Also, all of the distortion and phase shifts produced in other speakers, when a crossover changes from one driver to another, are eliminated.* Best of all, the music does not pass through the element of a crossover: inductors (coils), resistors, or capacitors. A crossover is a necessary evil in all other speaker systems. With full-range drivers, there is no crossover to deal with.

In most designs, only one full-range driver is used per cabinet. This gives perfect point-source imaging. *When someone sings, sound does not come from their mouth, their chest, and their knees like it does in so-called "normal" or as you said it "obvious" speakers. In addition, there are no time alignment problems (one driver being farther from the listener than another)*. You will be surprised at the stereo imaging of a full-range driver.

You can find information about full-range drivers, DIY plans, and companies that sell speakers with full-range drivers in the following links.

*Full-Range Drivers, Plans, and Speakers*
http://www.fullrangedriver.com/singledriver/drivers.html
http://www.fostexspeakers.com/fostex.html
http://www.commonsenseaudio.com/fostextech.html
http://www.tektondesign.com
http://www.teresonic.com/index.htm
http://www.tonianlabs.com/tonianacoustic.htm
http://www.unityaudio.ca/
http://www.fritzspeakers.com/index.asp
http://cardersound.tech.officelive.com/PurchaseInfo.aspx
http://www.decware.com/newsite/speakers.html
http://www.madisound.com/manufacturers/fostex/fostexcabinets.php

*Some User Comments:*


> Tonian Acoustics TL-D1, Wideband 8" Fostex driver augmented by ribbon supertweeter
> 
> These are by far the best speakers I have ever owned regardless of price. *I just sold my Dynaudio special 25 speakers. The Dynaudio's sound very uninteresting when you listed to these speakers for a whole week.* These speakers are very open, detailed and fast. These are spectacular with classical and jazz music. They have very natural, life-like sound to them. I would highly suggest anyone looking for another speaker, or thinking about improving their electronics to get better sound, to audition these Tonian Labs speakers. You will be surprised how live they sound!





> Tekton Uruz
> I am the original owner and have had them for 6-7 months. Have about 500 hours on them. I went to a set amp about 2 years ago and since than have owned Klipsch Heresay & KG3.5, Omega Superhemp, Zu Druid, and Coincident Super Conquest. I had the Zu for about a year when I bought these Uruz. I like the Zu because they were good or very good with all the styles of music that I enjoy. Read some great words from Tekton owners and Eric (of Tekton) convinced me to give the Uruz a try. 30 days later *I sold the Zu Druid, the Uruz are that good.*
> 
> The Uruz excel with vocalists, jazz, acoustical, chamber, and SACD's. If you prefer this type of music or use sacd's you will love these speakers. (The best jazz & vocalist speakers I have ever owned) They are somewhat omnidirectional in nature (need to be 36" from the front wall).


*Folded Horn Design*
Folded horn design enables the enclosure to contain a longer sound path which amplifies the bass frequencies while keeping the cabinet small in size. These horns, with the rear of the driver loaded by a bass horn, help a full range driver produce more bass with less work.

*Folded Horn Speakers:*
http://www.pispeakers.com/catalog/default.php/cPath/1
http://www.planet10-hifi.com/FH-flatpak.html
http://www.tnt-audio.com/casse/thehorns_e.html

There are many pictures of DIY speakers with full-range drivers and horn loaded cabinets in the following links:

http://www.quarter-wave.com/Gallery/Gallery.html
http://www.frugal-horn.com/gallery.html


*MY DIY SPEAKERS*​
This is the plan from Madisound that I used for the cabinet.










The approximate size is H: 35", W: 13", D: 17".

I ordered the full-range drivers and the super tweeters along with some capacitors and binding post from Madisound. They were delivered in one week. Usually, finishing the cabinets and deciding on the color is the most difficult part of the project.


*Fostex FE206E 8" Full Range Driver:*

*Frequency response:* 39Hz to 20kHz
*Sensitivity:* 96dB









*Fostex Fostex T90A Horn Super Tweeter:*

*Frequency response:* 5kHz to 35kHz
*Sensitibity:* 106 dB










I intended to let the Fostex driver run full range and cross the super tweeter at 13,000Hz with the help of the ClarityCap 1.5 micro farad (µF or mFD) capacitor.





















These are some of the parts for my DIY folded horn speakers.










This is a sneak preview of the cabinet before any gluing. I had to dry fit them to make sure all the pieces fit.










The following pictures show all the steps I went through to glue the pieces for the first cabinet. I used ordinary wood glue without any screws. It takes a while for glue to dry out, but after a few hours, it becomes harder than wood.






























The first cabinet was finally finished. Here are a few more pictures.








































Here are some pictures of the Japanese beauties out of the box before I attached them to the cabinet.





















Temporarily, I put the finished speaker together. I didn't even bother to add polyfill. After the second one is finished and the weather gets nicer, I will take them outside, sand and stain them, and I will then assemble them properly.










Here is a picture of the DIY speaker next to the vintage Polk RTA-15TL that I purchased in 1991. The super tweeter on the Polk speaker is the LCY 100K.









I decided to test the speaker. It sounded unbelievably good. I never heard highs and midrange like that. I stuck my head in the opening in the bottom to check the bass and I was blown away. Who needs a sub driver? 

I finally finished the second speaker. Surprisingly, the second one was a lot more difficult to build as some of the pieces wouldn't fit as well as the first one. I guess practice makes you imperfect. 

I cannot describe how good they sound. I can probably say that they are perhaps the best musical speakers I have ever owned.









Let me tell you that these DIY speakers have one of the best midrange and high frequency detail and imaging that I have ever heard. The folded horn design of the cabinets generates impressive bass. The Fostex full-range drivers are running full-range and the Fostex super Tweeters are running above 13,000 Hz to 35,000Hz. I had them attached in series with ClarityCap 1.5uF capacitors. I am hearing crickets in my two-channel room.


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## Big D

I decided to order two Audio Nirvana full-range drivers and experiment with them and compare them to the Fostex full-range drivers. I have plans to build another pair of full-range speakers for my family room to be used with the big 73 inch Mitsubishi TV. I also decided to upgrade the Fostex drivers. I haven't decided which pair of drivers I will use for them.

Here are some pictures.




















The gold colored part in the middle is called a phase guide. The Fostex driver comes with a whizzer cone and vented dustcap. On more expensive drivers that reproduce higher frequencies, you typically find a phase plug instead of dust cap. The bullet shape of the plug is designed to reduce the phase cancellations that may occur between the dust cap and the driver's cone. By reducing the phasing issues at these higher frequencies it is possible to improve and flatten the frequency response, resulting in more clarity and depth in the sound stage.

The DIY speaker upgrade consisted of two phases:

*Phase 1.* Initially, I had put the speakers together because I was in a rush to hear them. I finally decided to take the speakers apart and use, wood glue, caulk, wood putty, and anything else I could find to properly seal all the joints of the horn cabinets so that there are no leakages. I also added a thick layer of foam on the inner wall directly behind and around the driver and stuffed them loosely with polyfill. Because of this little tweak, the low frequency bass sound of the Fostex drivers became tighter and the midrange/high frequency sound became slightly more clear and detailed.

This was important specially because the folded horn design of the cabinet made the wall behind the driver too close to it (see picture below). The cone of the Fostex driver is paper thin and as a result some of the reflections off the back of the driver were coming through the cone and slightly affecting the sound, particularly in the midrange area.










*Phase 2.* I decided to replace the Fostex drivers with Audio Nirvana drivers to experiment and investigate the results. The Audio Nirvana drivers have bigger magnets, phase guides, and accordion style surrounds. On paper, they have slightly better high and low frequency extension.

I had to modify the screw holes on the cabinet to fit the new drivers and played some music through them for a few hours to test them out. The jury finally came in around 4:00 in the morning. I wish there was some way of going back and forth between the two drivers with an A/B switch. Unfortunately, I had to rely on my memory of the Fostex drivers and we all know that human memory is not very reliable. I have summarized the results in the following.

*Audio Nirvana Full-Range Drivers*

Bass was deeper and stronger.
The drivers had more oomph.
Although I did not run any test tones to verify this, it is possible that the high frequency extension was better.
Slightly warmer sound.
The drivers are very detailed.
Very efficient.
They are not as attractive as the Fostex drivers
*Fostex Full-Range Drivers*

The bass is not as deep, but it is tighter.
They did not have as much oomph and dynamics, but may have been more musical.
Fostex drivers are extremely detailed and revealing, particularly in the midrange. I give the edge to them.
Slightly brighter sound.
Very efficient.
The high frequency may not have been as extended as the Audio Nirvana.
They are more attractive.


















*Final Decision*
It is a close call. They both are extremely efficient and play very loud with little power. Both of them are extremely detailed and revealing that makes them a bit bothersome. I hear things on albums that I am familiar with that I never heard before. The downside is that if the quality of the recording is not very good, the album will not be enjoyable at all. Some of the CD’s that I liked before are not very pleasant anymore. The positive is that the good albums with good music have become more enjoyable.

What is the final verdict? I like both of my children. :hug: If I have to pick one, I would pick the Audio Nirvana for HT applications and the Fostex for music applications. The good news or the bad news is that I sent my Fostex drivers to be upgraded. I don’t know what to expect anymore. I hate this job. 

*Warning:* Do not trust everything I said. This was not a scientific test and I had to rely on my memory. These were my casual impressions that were made late at night in less than perfect room with less than perfect ears.

***********************************************************************

A while ago, I sent my Fostex full-range drivers for my DIY speakers to Decware for an upgrade. Steve Deckart at Decware sells upgraded Fostex drivers and upgrades the Fostex 206E drivers for $100 a pair. It upgrade includes the following:

Installation of a phase guide.
A new suspension system.
Cone treatment to improve timbre and voices.
Dampening of the spokes behind the cone.

They came back after a couple of weeks and they sound smoother and more enjoyable. These are the pictures with the stock versus upgraded drivers.


*The Original Drivers*












*The Upgraded Drivers*



















The main upgrades that he performed and the benefits are summarized below. You can also check the links at the end for more detailed information.



> *Active phase guide*
> Besides damping the frame and some minor cone treatments, the biggest modification to the original Fostex driver was the phase guide that was installed in place of the dust cap.
> 
> Our new High Definition Tower speakers are using a modified Fostex full range driver, model FE206E. A respectable sounding driver in it's stock form, a giant killer with the proper modifications. It comes stock with a whizzer cone and vented dustcap. On more expensive speakers that reproduce mid and high frequencies it's common to find what is typically called a "phase plug" located in place of the dust cap. The bullet shape of the plug is designed to reduce the inherent phase cancellations that occur between the dust cap and speaker cone. By reducing the phasing issues at these higher frequencies it is possible to improve and flatten frequency response. From a more subjective perspective it helps add depth and clarity to the sound stage with less beaming.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> *Active suspension system*
> The original FE206EM used an inverted roll cloth surround that is attached to the under side of the speaker cone. The cloth is treated, but not air tight making it impossible to create a truly sealed diaphragm between the inside and outside of the speaker cabinet. The cloth has the advantage of being low mass, strong, and quick. It offers no damping like butyl rubber but then butyl rubber is high mass, less strong, and slow.
> 
> We have added a specially matched positive roll polyether foam surround to the top of the cone, while leaving the existing inverted cloth surround in-tact. This creates a more linear resistance on the cone in both directions.
> 
> The suspension system also offers tighter bass control and enhances low frequency power handling by a notable amount.
> 
> *Cone treatments*
> We use a polyacrylic diluted with water and apply it to the cone under a high rotation. As the cone gets wet the fibers expand and the top layer of fibers are re-animated and brushed in the direction of the rotation. When the moisture evaporates from the cone, the polyacrylic encapsulated fibers are locked into position. The reason we do this is to remove the stress locked into the paper cone when it is pressed. The untreated cone is glass smooth to the touch while the treated cone has lost the gloss and developed a subtle texture. The improvement you hear in the sound of the paper itself when rubbed also shows up in the timbre of instruments and voices. A final benefit this cone mod brings is a stronger cone and one that is less effected by changing humidity.
> 
> *Other tweaks*
> The basket has felt lined spokes behind the cone, and each spoke is also dampened on the outside with viceoelastic foam pads. There is also a small 1/2 inch square pad added to the back side of the cone opposite the lead wires to offset the mass of the lead wires and damp ringing from the neck joint.
> 
> *Listening tests*
> When you listen to a 1kHZ reference sine wave on the FE206EM it sounds like any other decent driver would, but when you listen to a 1kHz sine on the DFR-8, it actually has tone, sounding more like an instrument than an oscillator. This was a rare observation made during testing. In the listening room, the driver is far smoother with noticeably better top end. The focus is better, and the sound projects better as opposed to sounding like some of the sound is coming out of the speaker cabinet itself. The ability of the cabinet to disappear has greatly improved.


For additional information, check the following links.

*Fostex Driver Upgrade:*
http://www.decware.com/paper79.htm

*Phase Guide:*
http://www.decware.com/paper46.htm


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## Anthony

Nice build! Thanks for sharing the pics!


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## Big D

Anthony said:


> Nice build! Thanks for sharing the pics!


Thank you. I updated post #2 with more information and pictures.

I had heard speakers with full-range drivers before at audio shows. However, I never realized how good they can sound, particularly with music. I have become a convert.


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## mdrake

Thanks for sharing!!!!!!!!!!!!!!!!! I bet those sound awesome. I have loved full range drivers for as long as I can remember. If you get a chance you should check out the Mark Audio drivers and see how those compare to the Fostex drivers. 

Matt


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## Big D

mdrake said:


> Thanks for sharing!!!!!!!!!!!!!!!!! I bet those sound awesome. I have loved full range drivers for as long as I can remember. If you get a chance you should check out the Mark Audio drivers and see how those compare to the Fostex drivers.
> 
> Matt


They do sound awesome. I have fallen in love with full-range drivers. They are very musical and enjoyable. I can listen to them for hours without getting tired. Also, they are very efficient and need only a few watts.

I have many old and new speakers in the house. I am already thinking about replacing them with full-range speakers. Unfortunately, I am afraid that my wife will kill me. :foottap: addle: :rofl:


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## angelod307

very nice. i am going to buid a set of folded horns to a set of CSS SDX7 and a set of the carver type small ribbons. were did you go in search of the box design. this will be my first folded horn, and your setup is what i had in mind. nice job on those, thanks angelo.


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## Big D

angelod307 said:


> very nice. i am going to buid a set of folded horns to a set of CSS SDX7 and a set of the carver type small ribbons. were did you go in search of the box design. this will be my first folded horn, and your setup is what i had in mind. nice job on those, thanks angelo.


Sorry, I did not respond earlier. I have been away for a while and just trying to catch up on my email and other chores.

Anyway, you can find speaker designs and kits from the following list:

https://www.madisound.com/store/index.php?cPath=178
http://www.decware.com/newsite/speakers.html
http://www.pispeakers.com/catalog/default.php
http://www.linkwitzlab.com/Wood Artistry LL-home.htm
http://www.woodartistry.com/speakers/index.html
http://www.steinaudio.com/fostexpage.html
http://www.craftyhands.net/Audio.htm


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## angelod307

thanks for the links. i am coming to the realization that some one is going to have to hold my hand in this design as i am kind of lost in how to go about determining what to do first as it pertains to the box itself.


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## Big D

angelod307 said:


> thanks for the links. i am coming to the realization that some one is going to have to hold my hand in this design as i am kind of lost in how to go about determining what to do first as it pertains to the box itself.


If you have never build speakers/subwoofers, you will be much better off buying a ready-made kit from Parts Express, Madisound, or Occam Audio and put it together. Starting from scratch requires knowledge of speaker design, crossover design, good carpentry skills, and availability of tools and space. You won't necessarily save any money. The advantage of the kits is that all the speaker cabinets are precut. You can buy them with or without drivers/crossovers. The speaker cabinet kits from Parts Express are pretty cheap.

Watch the videos at the end of the first link:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-702
http://www.parts-express.com/wizard...AT&srchCat=769&CFID=33689097&CFTOKEN=76228419
http://www.parts-express.com/wizard...ce=&srchCat=603&srchMfg=&srchPromo=&srchAttr=
http://www.occamaudio.com/shop.html
https://www.madisound.com/store/index.php?cPath=178


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## angelod307

i have never build a folded horn speaker. i have indeed build more subwoofer boxes and all thing car audio with a high degree of knowledge around power tools. i have build many home theater audio cabinets as well as tower and monitor boxes for home too. it is the actual design around a specific woofer that i am in need of help. i have seen that it is not like a ported box that is kinda universal when designing. from what i have read, the folded horn cabinet has many things to be considered when building it. the woofer that i mentioned above was brought to my attention when i was looking through some open baffle designs using the carver 6" ribbon. well, i though that i would take this a step further and do something different to get a more natural and fuller sound, something that indeed has added lower end without the typical boomy/box sound. something that i would hope has more of an open baffle yet an increased punch and impact that most baffles lack. that is what i am after anyway, what i would get may be a whole different set of apples. i am open to the idea of buying a kit, but again, on a scale of 1 to 10 of how good i am with box building, i give myself a 9 only because i don't want to pat myself on the back too much. the only people that can do it better, do it daily and just simply have more practice. i have been wook working for almost 25 years now as well as being into high end car audio and home audio for the same amount of time if not longer.


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