CAOW1 Speakers

CAOW1 Speakers

Completed 9-2009

These speakers are based on Dennis Murphy's published CAOW1 design here. I choose this version over his MBOW1 here (which uses a different woofer) for its ability to play a bit lower, as I plan to use it without a subwoofer most of the time. Dennis's website is highly recommended, and Dennis is known in the speaker community as a very talented designer, and he graciously shares many of his designs on his website.

The CAOW1 uses the Hiquphon OW1 tweeter (info here) and the Seas CA15RLY (also known as H1216-08) 5" mid-woofer (info here) in a ported enclosure.

Rather than build a traditional bookshelf speaker and then mounting it on stands, I built the speakers as floorstanding units so no separate stand is required. Dennis's cabinet plans are here.

Drivers

Above: the OW1 tweeters. Each matched pair comes with individual frequency response curves.

Above: The Seas CA15RLY woofers

Construction Details

Above:The cabinets under construction, before the front baffles were attached. Note the 2" hole that will contain the port on the rear panel. The speaker cabinet is the top third of the box, the middle third will house the crossover (accessible thru a removable panel on the rear), and the bottom third will house ballast material (20 pounds of kitty litter). The cabinets are built of MDF for the sides and top/bottom, with front and backs laminated from MFD and baltic birch ply.

Above: The front panel, before assembly, rear view. Note the chamfering around the rear of the woofer cutout. The tweeter cutout was done after assembly and veneering, as it was recessed thru the veneer. The woofer is surface mounted with no recess.

Above: Damping material applied in top portion of cabinet. I used a 1.25" 3 layer damping material called Sonic Barrier from Partsexpress.com.

Above: To attach the grilles, I mounted neodymium magnets (from Woodcraft.com) under the veneer so they don't show. This photo shows one magnet recessed into the front panel and super-glued in. I filled above them with wood putty and sanded smooth before veneering.

Above: Completed cabinets, ready for driver mounting, showing rosewood veneer. The veneer was finished with about a dozen coats of Waterlox high gloss finish (rub-on, tung oil based), which took weeks to dry over the oily rosewood. Notice the grill mounting magnets don't show.

Above: The base, showing oak trim (painted black) and SoundCare SuperSpikes (info here) which contain both spikes and an integrated floor protector.

Above: Rear panel with terminals and attached crossover.

Above: The completed crossover. The resistors are Mills 1% 12watt, the tweeter cap is a Sonicap Gen 1 with a Vishay MKP1837 0.01uf bypass, the other caps are generic polypropylene. All the caps are selected within 1% of target values (and of course, the other channel). All the coils were either selected or unwound to also be within 1% of target values. I spent some time determining the layout (as the chokes are close together) to eliminate any crosstalk between the chokes, using the technique shown here.

Above: Finished speaker. The veneer wraps around from one side across the front and to the other side in one large piece. The top has solid rosewood edges that were routed to match the radius on the speaker sides.

Above: The other speaker, front view.

Above: Rear view showing port at the top and access panel for crossover.

I later added handle to aid in moving the speaker and a custom aluminum name tag to the rear of the cabinet to label the speaker. The labels are from Burton (very helpful) at https://www.ebay.com/str/audiotagsiowa

Measurements

I made some measurements to verify performance using a Liberty Instruments IMP and a calibrated Mitey Mic microphone.

Above: Frequency response (time gated above 300 Hz to eliminate room effects). Note the response is within about 1.5db of flat.

Above: Impedance curve (low frequency only) showing box tuning frequency of approximately 55 Hz.

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