Fostex 168z – A Wonderful Full Range Driver

The Fostex 168z (older style with whizzer) is one of my favorite full range drivers. I’ve tried it in several cabinets but enjoy it most in a large ported box. It has a midrange heavy sound but when you bring the bass in line with the midrange it sounds beautiful. It doesn’t need a tweeter on axis but I prefer the sound slightly off axis and with a rear mounted tweeter.

Fostex 168z in Large Ported Box (42L)

Nagoaka Tetsuo designed a 46 liter cabinet for this driver and even tho it doesn’t simulate very well (not flat) it sounds great! Years ago I built the 46 liter cabinet but lost them during my divorce. Fortunately, I came across a pair of large AR cabinets left out for trash, brought them home and refinished them. You can see the shape they were in. With a little elbow grease I was able to restore them. They look great sitting in the corner of my apartment. They are 42 liters but certainly close enough. They are tuned to 59Hz.

As for the sound, it’s just as I remembered. The bass really bounces along. It’s full and rich without any strain. They are not perfect but always make me smile and produce an engaging sound. It’s a bit full in the bass (which can be adjusted to taste with more stuffing) but everything else is wonderful up until the treble where they roll off. I may put a tweeter on the rear to add extra sparkle. Otherwise, these are great examples of how a full range driver can sound in a simple ported box. If you already have these drivers, or come across them used, I can’t recommend them highly enough in large ported boxes.







Fostex 168z in a Back Horn (BK161)

My son, Jeremy, standing beside a not too successful back horn project.

Pros: Jump factor, big sound.

Cons: Hollow sounding, impossible to move around due to the MDF construction and sand filled voids. I’ll never do this again.




Fostex 168z in a BIB

Much better sounding than the back horn above. The BIB sounded great in corners retaining all of the drivers positive traits. It’s certainly one way to go with this driver but I prefer the large ported box because it’s smaller and has a bouncier, more fun bass. The BIB is dryer sounding and probably more accurate (flatter).


My boys, Jeremy and Jason, helping me build a BIB!




Fostex 168z in Ported Box (24L)

It sounds good up against a wall or in a corner but never fully satisfies since bass extension isn’t great. It’s ok and can be satisfying but does not allow this excellent driver to reach its potential. Build it if you lack space and can’t build the larger box otherwise, I’d say the overall performance is only average. The box is tuned to 62Hz.




Fostex 168z on Open Baffle 

Certainly a good performing speaker. It satisfies on many levels but can sometime sound dry. Although I like this speaker I still prefer this driver in the large ported box. Here I have mine set up on top of H-frames (Alpha 15). Just about anything sounds great on top of H-frames! The baffles are 18″ squares. Using Thorsten Loesch’s Open Baffle Spreadsheet (speakers two feet from the rear wall) my simulations predict a rolloff around 250Hz (the red line is for the Fostex 168z). Clearly there are better choices for open baffle but I was curious and happily listened to these for months before taking them apart.

OB-freq-18x18-baffle fostex-168z-open-baffle


TangBand 1320 projects

The cone of this driver is made of bamboo fibers. It’s a very nice driver and well made. I have been enjoying them on open baffles (on top of H-frames for bass support) lately. They sound great if you like a darker sound. I prefer these with tweeters but they have an extended treble response that’s muted and soft. Overall, one of my favorite drivers. In a small ported box it sounds like a a good two way speaker. Occasionally I feel the driver has a mechanical sound that separates it from the best drivers I’ve heard.




Fostex 127e projects

The Fostex 127e is regarded as an excellent performing full range driver. It’s no longer in production but the newer Fostex designs using similar nomenclature likely follow suit and offer similar (probably improved) performance. The 127e has a Qts of .43 making it suitable for ported boxes. With careful calculations this driver will provide good bass but many will find a subwoofer a nice addition. Personally, I prefer it without a super tweeter. Some are bothered by the treble break up. A tube amp goes a long way in taming this excitable driver.


Fostex 127e in a Small Slotted Box

I built this small slotted box and believe it’s a good size for smaller apartments. Rather than a flat alignment, I’ve bumped up the bass slightly. It’s simple to build using standard sized lumber. This cabinet is only 5″ deep and sounds best close up against a wall giving it a fuller sounding bass.






Fostex 127e in a Straight Pipe

Not too successful. It looks beautiful but is lacking in bass. Essentially, I see this as simply much too large box for the 127e causing the bass to roll off early. The Straight Pipe is a very nice cabinet for an appropriate driver.



Fostex 127e in a BIB

I could not find my picture so used Uvellani’s 127e BIB pic. Currently in storage, I plan to use them when I have an appropriate room to put them into. To my ears a BIB is the way to go with the Fostex 127e because it balances out the bass response really well. You can tuck these into corners and have a beautiful sounding system encompassing all of the elegance of a full range speaker without much compromise. These won’t play super loud but they will fill a small to medium sized room with sound that won’t leave you wanting. One of my personal favorites.