Cloning the Okara - 2-way reference Speaker

[sunilj]

The Okara is a 'North Creek Music' 2-way bookshelf design. It uses the legendary Vifa P13 mid-woofer and Scanspeak D2905/9500 tweeter. SDS labs went a step further and re-designed the Okara with the Vifa XT-25 ring radiator another great tweeter.

I've been using the P13's for a long time and love the mid-range they're capable of. With an fs (resonant freq.) of 60 and Vas of 10, it does not go very deep but more than makes up in dynamics & sound. I'm a believer in 3-way with the woofer de-coupled from the Tw/Mid using active crossovers. Crossed at ~100hz, I've found this combination to be un-beatable with outstanding dynamics, power capability and sound. Crossing at 100Hz removes the low frequency energy from the bookshelves so they're not distracted from doing what they do best. Lets not start to discuss the merits of "NOT" requiring a mega-power amp because the gainclones drive them very well.

I also have the P13 & laid my hands on 2 pairs of the XT's on ebay, so decided to clone the Okara with the SDS' design. Here we go.

 

[sunilj]

Preparing the enclosure

The enclosure is a basic MDF box. I'm a firm believer in tar sheets for damping enclosures and sure enough that's what I did first.

Pic1: The tar sheet sandwiched between two plastic wrappers.
Pic2: Remove one of the wrappers and expose the tar (bitumen) layer
Pic 3: The bare MDF box
Pic 4: Fevicol SR applied with a wooden spatula to the tar sheet
Pic 5: Prime the box surface with the same SR glue

 

[sunilj]

Pic 1: Tools of the trade - a small wooden hammer and piece of wooden reaper to tap down the tar sheet

Pic 2 & 3: The completed box

 

[sunilj]

Wiring a crossover

The crossover shown here is not of the Okara but I thought I'd put it here for others to see how easy it can be.

Pic 1: Start with a bare wooden sheet of MDF /Ply /Wood
Pic 2: Layout the components based on the crossover and wiring
Pic 3: Mark components and drill the holes for tying down
Pic 4: The connectors go in (not necessary to be done first...but I did)

 

[sunilj]

Wiring a crossover II

Pic 1: The first component gets tied down and conenction soldered
Pic 2: Completed crossover

 

[ukjeyaraj]

Nice work there.

 

[santhosh]

Way to go Sunil!!

When can I drop by for a listen?

 

[GeorgeO]

Very neat work, Sunil

 

[Gijo George]

Thanks for the pics Sunil . I've used the tar sheets myself in my center channel as you suggested but didn't use SR though. It stuck pretty well even without it. Used three sheets on e top of the other.
Gijo

 

[sbg]

Good work!

solderless connections! on crossover and wiring - absolutely good idea when you try to mix and match various comp and testing.
Do you plan to keep it that way , or have it finally soldered.

 

[sunilj]

The electrical connectors will remain that way. The components are soldered. The actual Okara x-over is a 3rd order electrical, a lot complicated than the one shown and two separate boards for each leg.

 

[kaushik]

nice build

 

[t.antony]

Good going Sunil, neat job with the crossover.

What is the thickness of the tar layer?

 

[cmsajith]

Great, another serious build coming up...

I think the tar sheets can be held to the enclosure by slightly heating it and paste it before it hardens.

 

[kaushik]

i am very happy to see diy section is shining ,with the hurdles still being in place.
Sunil, where to procure the tar sheets and what parameters we need to see [bangalore shop? ] , if this works may be my speakers will look more like speakers inside than a blanket

 

[sunilj]

Thanks guys. Encouraging words there.

TJ,

The sheets are 3mm thick. I use SR so it melts the tar and if padded down proper, it bites into the MDF/Ply so well, if you try to rip it off, a part of the MDF will come with it. The two materials sync well as 'ONE'

Kaushik,

I picked this up from some hardware store in SP road. Its available pretty easy. I can give you a sample if that will help, but it is available in a LOT of places. Funny thing is I had to buy something like 10m......because thats how they sell them and it cost Rs.200 or something. The first lot I bought was from Corrson, some Dubai based surplus, but first class. I had to pay a premium though, after SP raod, never looked in that direction.

Status on the build:

Cat5 cable braiding (X-over internal) in progress, fingers are numb and its a P.I.A 4x2core@24AWG = 16Gauge

I want to wrap this up this weekend....hopefully.

Regards,
Sunil

 

[sunilj]

The finish - teaser shot

I hope this gets a WTF reaction. I wanted to do something different and funny. Reminds me of a large African Horse...

 

[Kannan_madhu]

@Sunil
is the xover components sourced locally or is it imported

 

[sunilj]

Hi Kannan,

The x-over parts are from Madisound. I got them while I was in Melbourne last year. Except for the inductor coils, which you can wind, the caps and resistors we get here will give you as good sound and terrific value for money.

continuing where we left off on the Okara's....

The x-over interconnects are braided cat-5, 16gauge approx. Hard to do, but definite value for money.

I've finished my build but can't upload any more photos. Hmmm, got to figure this 250KB limit. Any ideas what i need to do ?

 

[har297]

we can upload pics in image shack and give the link here...

Regards
Harsha