DIY Subwoofer with Lambda Acoustics SB12 driver

Finished building this monster subwoofer a few months ago. This is part of my HT system; the quest for which is described in this thread. http://www.hifi-foru...rum_id=60&thread=327

DRIVER
I used the highly acclaimed Lambda Acoustics SB12. Made in USA but no longer in production. It was a premium product which unfortunately could not continue due to its high price. I was lucky to get a piece some years ago. Its huge and heavy at about 10kgs.





The Lambda SB12 driver is designed for sealed enclosure. It has a high xmax, stiff poly cone with stiff poly dustcap, coated and sealed foam surround, 12 spoke aluminium basket, dual stack 120oz magnet, gold binding post, military spec coatings and glues. It is a high excursion, very low distortion, super tight bass driver. Recommended maximum crossover point is 500Hz, rated power handling is 500W. 2.83VSPL = 88.6dB

Specs
Size: 12"
Motor : PL (overhung)
Magnet : 3.4Kg Ceramic 5
VC diameter : 51mm
VC Former: Black Anodized Aluminum
VC Wire: 2 Layer Copper Roundwire
Basket : Cast Aluminum 12 Spoke
Cone : Mineral Filled Hard Poly
Surround : Doped Foam, 2 layer treatment
Dustcap : Hard Poly
Spider : Hard stiffness Nomex
Faraday : Copper
Terminals: Gold Plated Binding Posts
Weight : 10 Kgs
Fs : 20.9 Hz
Qms : 4.23
Qes : 0.64
Qts : 0.56
Vas : 160 Liters
Cms : 0.4 mm/N
Mms : 145 grams
Sd : 531 cm2
Rms : 4.5 Kg/S
Pe (nom) : 300 Watts
Pe (max) : 500 Watts
Pe (transient) : 1000 Watts
Air Gap : 14 mm
VC Length : 38 mm
Linear Xmax : 14 mm (peak)
Mech Xmax : 20 mm (peak)

AMPLIFIER
Along with the Sub driver I had also bought a high power Marchand MOSFET amp and their excellent active XO in Kit form. However I later realized this was a complicated route to follow. The XO would not permit all the function I wanted in a sub. A costly mistake. Particularly as they all came from USA.

Later a friend imported a pair of the famous OAudio BASH 500 watts plate amp from the US. This amp has all the control one will ever need to perfectly integrate a subwoofer in any environment.






Here is the linK to manufacturer’s website:
http://www.oaudio.com/500W_SUBAMP.html

And here is a review
http://www.audioasyl...ks&n=117881&review=1

ENCLOSURE
With a VAS of 160 liters the required box is BIG! A proper sealed box would have been about 10 liters.

Since it needed to live in our bedroom, the size had to be reasonable. A compromise was sought. I did not want to loose out on those really low notes such as pipe organs and starwars fx effects.

After a lot of modeling with spreadsheets and keeping in view the required goals a size of about 4cuft was decided. Its still huge almost the size of a small washing machine. But just about ok.

CONSTRUCTION
I used up one full sheet of 8ft x 4 ft MDF. The construction was done in “sandwich” style. Internal braces were used. From this close up pic you can see the wall thickness that is the result of sandwiching two panels of 22mm each. Together they become almost 2 inches and heavy as granite.



Its filled 80% by thermal glass fibre and the internal are lined with a very expensive acoustic liner. You can also see the “ducktail” type of edge joints for added rigidity. The joints were sealed with silicone compound.



The result is a box is dead quite and needs about 3 people to lift. This was a huge construction. I was assisted by my daughter and a jack-of-all-trades type of guy. The panel are glued to each other and screws were used to tighten the panel. Once the glue set it the screws were removed. Only the glue holds the box together. Needed about 15 U and C clamps for temporary bracings.

Here is the cutting layout for anyone interested.



The exterior was lined with DURIAN brand veneer. But I goofed up on the finish. I guess I will get a professional to undo the polish damage and put a fresh layer. These require skill and sadly I can’t be a good polish guy.

FINISHED SUB

With the front grill removed. The CD is for size reference





PERFORMANCE
I live in a detached property. The next home is about 50 meters away. The first night of testing I unknowingly rattled our neighbour’s fancy window pane with a 20hz test signal. Next morning he was mumbling something about mild earthquakes and wanted to know if I too felt that.

I don’t wish to sound biased but I am yet to hear a better sub (not OB type) at any price point that even comes close to this.

I am very pleased with this sub.

Hi Ashok,

Thanks for the ebay link. The amp is not available for sale any longer on ebay, but I think I will be able to contact the seller.

I completed my subwoofer build with the Eminence Lab 12 driver. Did some initial testing with by driving it using my Stratos AMP - it sounds pretty good.

I can't wait to get an AMP and finish the project.

I will post pics and Graphs on a seperate thread this weekend.