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Rectilinear XIa


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Another Rectilinear project, although I probably spent too much on them. It's a long story. These are the XIa, the improved version of the XI that I describe here: 

The XIa is a 2-way ported design with the model W-11 10" cloth-surround woofer and the T-11 3-1/2" paper tweeter. The crossovers consist of an audio choke (inductor), resistor and capacitor. It's the same woofer as the XI but a different tweeter (the XI used a phenolic ring) and it is crossed over at 1,000Hz instead of 1,800 like the XI.

The cabinets are 23" x 12" x 10-1/2" deep (about 1" smaller than an AR-2 series in every direction) and are made of 5/8" stock with nice walnut veneer. Nominal impedance is 8 Ohms and Rectilinear claimed the actual impedance never dropped below 7.5 Ohms. Very efficient--the sales lit said a 10 watt amp can drive them to "window-rattling levels."

When I got around to them I discovered the woofers were bad! :angry:. Thought about a DIY project using GRS 10" woofers and CTS PR tweets  but after some procrastination found a complete set of drivers, with xo on ebay. Had everything in storage until last week. Here's the restoration project:

Cabinets needed a couple of chips filled with brown epoxy. I then sanded VERY lightly with 220 grit paper but some scratches were left.

The xo had a 12uF black & red PVC cap. One wasn't too bad (about 14uF) but the other was over 18uF. Replaced them with some Madisound Surplus Caps: 10uF & 2uF in parallel.

The grille cloth was kind of ratty and one Masonite frame was broken, so I tore the cloth off and replaced it with some linen left over from another project. I had also bought some Mod Podge for the other project and noticed it is virtually identical to Aleene's Tacky Glue but thinner, so I used that to attach the linen to the grille frames. Spritzed them with water and left them out in the direct sunlight and they tightened right up.

These are ported speakers, so no stuffing, but I know from working on other ported speakers that the cabinets are often lined with sound deadening material like acoustic foam. I had used a foam mattress topper from Walmart for the Rectilinear XIs and had some of that left so the back, sides, top & bottom got an application of foam. I cut out the foam behind the port so it would not block it.

The recess for the tweeters had been filled with what I believe is Bondo (previous owner was a car guy) but not too smooth so those had to be sanded down a bit. Some of the holes for mounting the woofers were over-sized so I filled them all in with epoxy, then rotated the woofers a bit and made new holes. Woofers and tweeters were installed using Parts Express deep thread screws. The tweets were caulked with electrical duct seal and the woofs received PE self-adhesive foam gaskets. No need to be air-tight on these ported speakers but I didn't want any rattles.

All done. They sound good but I have no place to use them so they'll go down to my favorite electronics store to be sold (I hope) on consignment. Some pictures below.

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06 22 16_0478 copy.JPG

06 22 16_0479 copy.JPG

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Thanks David. Sound is excellent. In my shop I have 2 pair of reference speakers: AR-91s for "big" speakers and Cizek KA-1s for "small" speakers. The Rectilinears compared very favorably to the AR-91s and better, IMO than the Cizeks. They have a more convincing bass than the Cizeks although, when compared with the ARs the Rectilinears "may" have a slight mid-bass emphasis but not bad. I played a variety of music: Mozart, "Jazz at the Pawnshop", "Graceland" and all sounded quite good.


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Nice to see a new Rectilinear thread again. Nice job on those, Kent, and thanks for noting the differences between the XI and the XIa, and the light grille cloth looks very good. Reading your initial post here made me curious about the pair of XI's that I mentioned in your earlier XI thread, and yep, my ported specimens are sort of half filled with wads of cotton batting. I am sure this batting is original because I have seen the same material inside an early Rect. Mini-III. Since the woofer was out, I took the opportunity to remove the awful little original fasteners that had hex nuts on the outside of these threaded nails. The little ears under the nail head were meant to grab from below much like a T-nut, but they are not very effective. I will replace these with either T-nuts and machine screws or a heavy-duty threaded wood screw as you have mentioned.

Nice project. These speakers are sleepers in the marketplace.   

XI stuffing.jpg

XI fasteners.jpg

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