Skip to main content

Jensen Ultraflex Cabinet for 8" Speaker

Today is the end of a long weekend commemorating the 150th birthday of our national hero Dr. Jose Rizal. I can't help but wonder whether he as well as our other national heroes died in vain... I am quite confident our current president is a sincere man who wants to get rid of corruption and lead us towards progress but there are elements in government as well as sectors in our society who don't cooperate. ;o( 

But mulling over matters beyond my control is a waste of time and energy. It's best to turn time and effort towards productivity. ;o) When I lived in the USA holidays were spent building projects to avoid heavy traffic and crowded places, so...

Years ago I wrote fondly about the Jensen Duettes as SE amp friendly budget speakers. I am not abreast with current pricing on these drivers and wonder if they still qualify as budget specials?

 Influenced by the article my buddy Rofiel collected a few Jensen and vintage Japanese drivers and wanted to try a bigger cabinet so I sent him the plans below. A few months later a pair of Ultraflex cabinets built from 1/2" phenolic plywood arrived at my doorstep.

Meanwhile these Ultraflex cabinets sat in a storage bin in the attic for over a year so a week ago I dropped by Joey's shop to cut holes on the front baffle with his router.

High quality plywood is expensive and hard to find in Manila. The closest affordable option we have available is phenolic faced plywood for industrial construction.

Simple crossover using a 2uf paper in oil cap + generic 16 ohm L-pad to the RP103 tweeter. 

Damping material for top and bottom panels as recommended on page 2 of the plan. Initially I was listening without any damping material and it was fine in free space standing on glass blocks. The moment I placed it in a corner, the bass tended to boom. Since there's no Walmart (my old source for Dacron) in Manila, I cut up an old foam pillow. That controlled the bass boom but I may have to experiment further with material and amount of damping...

Bogen B62 (Lenco L70) - stock arm fitted with a Pickering 380 or Shure M7D (coils connected in series) for Stereo LPs played in mono + Velvet Touch viscous damped tonearm with GE RPX---> JE Labs/PAS preamp - Telefunken 12AX7 phono + 12SN7 linestage (only one channel used)---> JE Labs SE71A amp.

Evolution of a mono hi-fi system in the study room...


  1. How do you find/are you enjoying that Pickering 380, by the way?


  2. The 380 is a darker sounding cartridge compared to the M7D. Better or not, will solely depend on the system context.

    IIRC, I've exchange messages with you a while back...thanks for dropping by and happy listening!


Post a Comment

Popular posts from this blog

Altec 2-way horn system redux

Truth be told, I was never fully satisfied with the performance of the Altec 2-way which is why I never uploaded the old article in the Arkiv.
Let's recap how the 2-way horn system evolved...

The project was conceived in mid 1998 because I needed a monitor system that was more efficient than the OB/755 so I could listen to SE amps with 2 watts output and below.
I commissioned my cabinet maker neighbor to build 614 bass reflex cabinets and loaded them with Altec 419A 12" drivers + 811 horns (early version/heavy sand cast) and 804A compression drivers gathered from hamfests and radio shows. Crossover was a textbook 1st order/6dB/octave hinged at 900 hz and the horn padded down to match the sensitivity of the low frequency driver.

Eventually I acquired proper 12" woofers - Altec 414As, which lack the upper midrange nasties of the 419As. The 414As have great midrange quality even if they lack the bass end of their larger 416/515 brethren.

802D compression drivers replaced t…

2017 Update: Hi-Fi Room

One year progress report

Garrard 301 + Ortofon RMG 309/SPU GME or SME 3012 + Denon DL103 Altec 4722 MC step-up
Digital line level sources processed  through UTC A20 transformers

JEL Stereo Preamp DX
JEL Stereo SE2A3 DX amp with Tango NY15S OPTs
Altec 2-way Altec 414As in 3.5 cf bass reflex enclosures + Altec 32A horns with 802D compression drivers
Mono Neat P58H 4 speed idler turntable + Velvet Touch viscous damped tonearm with Denon DL102 or GE RPX cartridges

je2a3 mono integrated amp

Stereo > Mono Line Level Mixer

Mixing line level stereophonic signals into full dimensional monophonic ;)
Here's a DIY project for mono aficionados that's so basic, I should have uploaded it many years ago. But other things got in the way.

Just like an MC step-up, these are entirely passive devices. 

The simplest way to convert stereo to mono is to connect left and right channels via a Y connector. But there's a more elegant way than just shorting two channels.

Resistors can blend two signals into one better by...

...using Allen-Bradley carbon composition for warmer sound ;)
We can end the mixing quest here but...

...the most elegant way of mixing two channels as was done in the studios by audio pros of yesteryears was through transformers.

This single UTC A-20 transformer was in a box lot of tubes and parts I picked up at a radio show. It's a high quality transformer designed for mic, mixer or line matching applications. Instead of trying to find a mate for MC step-up duty, I repurposed it for a g…