Project 7 (last update Feb. 2002)
Project 7 - first pic

The quickest project to date.
A friend called me and said: I saw your web page. I love what you do. Can you please make me a pair  of speakers?
And I really could not believe I said YES. Call it vanity . I am not used to handling flattering with a right dose of assertivity.

He told me the budget - 1500 USD a pair.
I thought this could be a great challenge.


The resulting design is this:
BASS: two Vifa M26WR-09-08 paper drivers, each in separate sealed 57 Liter enclosure
TWEETER: Revelator 9900 (I wanted 9700 for the sound but my friend insisted on 9900 for its sexy looks).
MIDRANGE: Scan Speak 18W 8542 paper mid woofer in open air baffle (sans box).

The key element is the box less midrange. It has been bugging me for some years now, that no matter what I do, my finished speakers never sound so good on voices as when I test the raw drivers unboxed and without XO. The box influence on sound can not be eliminated in any other way than eliminating the box altogether.
8542 seems just ideal for the job. It used to be my favorite midrange at any price. That's until I heard Alnico Saba. Shame it has been discontinued.


the beauty of this sealed bass / open midrange design is that the dimensions don't matter much.
Do it as it pleases you.
The things to observe are:
the center of tweeter must be at 100 cm height. Good tweeters are SS-9700, SS9900, and SS Ring Revelator.
The speaker width externally is circa 36 cm plus minus two
The depth can be between 45 and 55 externally
Inside - one shelve divides the internal volume for exact halves and it is airtight.
In biwiring - the mid and bass go together, tweeter is separately.
MDF thickness is 24 or 25 mm.
The midrange sits above tweeter as close as possible to the tweeter but not any closer.
Bass divers are roughly in the center of their volumes - on the front panel.
The midrange baffle has no side panels, no wings, nothing except flat baffle. It can be an extension of front panel.

It is advisable that midrange is mounted 18 mm in front of the tweeter. Such "step" can be made with 18 mm MDF or plywood. This is done for time alignment of the sound .


The result can be seen below.

 


This is the bass-high module, with two cavities for bass, separated by a sealed partition shelve.


The XO:


The coils are air core, wire wound. The caps are generic polypropylene, except the jensen for a tweeter.
After one year, the bass was improved by a slight reduction of midrange. I added an L-pad before the mid driver - 2,2 Ohm series and 18 Ohm parallel. Bass sounds absolutely awesome now.


The construction: 25 mm MDF with wood glue. With a good cutting job, the assembly is very easy. I did the boxes in two 3 hr. sessions. XO took me 1 hour making, 2 hours adjusting. The whole project can be had in one weekend ! And the result is guaranteed !
The only thing - you MUST have a router.

The sound.
first thing is the bass. It surprised me in a big way! I think that this Vifa is a FANTASTIC driver. IMHO better than scan speak 8565 !!!
The tonal purity of this bass driver when playing the midrange makes it suitable for a TWO-WAY !!! It is extremely fast and controlled. It behaves better than any driver I tried before, my ATC being the closest.
The highs from the Revelator are exceptionally good - everyone knows that - and again I confirm that fact. 5 stars with a bullet.
The midrange: the result of my experiment can be evaluated for a solid 10 points out of 10. Exactly what I wanted: an open sound, that stretches faaar wider than speaker base and faar deeper than the room back wall. The sound is TOTALLY free of the loudspeaker's placement. Totally hallucinogenic 3-d spectacle like the IMAX cinema, but sans goggles. The voices are so real that I laughed in disbelief.
Let me tell you: THERE IS NO MIDRANGE LIKE THE OPEN BAFFLE !

See the details of the midrange mini baffle (for the photo it was turned 90 degrees to show the rear opening.

The integration:  These drivers achieve the best integration of sound I ever heard in my designs. All 3 of the drivers are a match made in heaven.

Summary: I recommend these speakers as an exceptional value for money. I vote them my best design ever, and on my electronics - the one of the best sound from HI-FI  I ever heard. They win with Project 6 (and 5 as well) in almost every respect. What can I do ?

I can think of some interesting variations:

Full antique paper version: replace Vifa bass drivers with the natural match for 8542 - the 8562's. They look the same as the midrange and sound more refined, although cost twice as much.

Full carbon version - 8565 as bass, 8535 as midrange.

Full slashed version - both bass units and midrange can be the newest 18W slashed revelator.


WORKS IN PROGRESS


You can be jealous about how dusty can be the Kingston kitchen and WITHOUT WIFE COMPLAINING. I don't live there, remember?
 

RETURN