Offered for your consideration is a pair of vintage CTS Alnico magnet 10 inch woofers removed from my walnut-clad Ohm Model D two-way speakers, USA-manufactured in 1972.  As you probably know, CTS was a major supplier to the domestic speaker industry from the early 1960’s through the 1970’s. Based on the EIA source/date codes on the magnet covers, “137 7248,” these mid/bass drivers were made by CTS (137) in the 48th week of 1972.

So, please see my large photos, measurements, and read the remaining description to decide if these capable CTS Alnico mid/bass woofers are correct for your needs.

This pair of CTS 10” woofers is in clean, very good condition. The sturdy textured paper cones are structurally flawless and the voice coil dustcaps are also perfect.  Also, the bronze-tone anodized baskets are in good shape with just some factory machining scratches, a pair of tiny dings on one flange edge, and some whitish oxidation on the magnet keepers.  Plus, they have aluminum dust shields on the magnet covers’ sides, which adds a nice touch.  And, the “double-type” +/- terminals are marked for polarity (red dot side = positive) and I’ve retained a good length of the input wires, neatly bound, for the new owner’s convenience in splicing-in to their speaker.   Most importantly, the aged original polyurethane foam suspension was just replaced with quality polyether surrounds that have the correct flat-attach, inverted roll profile.

The main drawback to most U.S. and foreign-made speakers from the early 1970’s to mid 1990’s was the use of foam for the woofer surrounds. Though foam offers excellent cone excursion, it invariably rots and/or disintegrates in 12-20 years no matter what climate you live in. These woofers were no exception—the surrounds were dry and cracked, with pieces missing, and took the Ohm D speakers out of service for the last 25 years.

Some of you have replaced woofer surrounds before, so you know that it’s a time-consuming process that takes a great deal of patience and a steady hand. First I removed the hard paper flange gaskets, which were in bad shape and subsequently discarded.  Then I cleaned the cone edges/basket flanges carefully to remove the old gummy foam and stubborn factory adhesives, which took some time to do thoroughly, then glued the inner surrounds to the cones.  Next, I glued the outer surrounds to the basket flanges after careful centering to ensure no voice coil rub.  Then I installed new four-segment paper chip gaskets to the flanges to complete the factory appearance.  Overnight drying of the glue was allowed for each step of the process to achieve the clean and perfect results you see here.  Now these woofers are in great shape once again—perhaps even better than new with the improved polyether foam surrounds of today.

Naturally, they’ve been fully tested after refurbishing and sound great—very strong and clear with detailed lower midrange, solid low-end, and the special warmth of tone that keeps Alnico magnet speakers in such high demand.  Plus, I tested their DC resistance at a well-matched 6.7 and 6.9Ω, consistent with a nominal 8 ohm driver rating.  Lastly, the baskets measure 10¼” in diameter, they stand around 5¼” tall, and the mount holes are spaced 7” adjacent / 9¾” diagonal part, c-t-c (common to most all U.S.-made 10” drivers).

These are a great find for someone restoring their Ohm Model D speakers or many other domestic brands that used this type of 10” woofer.  Plus, they’d make a super choice for a vintage driver speaker project for tube or modest-power solid state applications.

As pictured and described, this great-sounding pair of CTS 10” Alnico magnet woofers is offered at a competitive price.

I encourage interested parties to ask any questions they may have about this listing before committing to purchase.  Payment is due at checkout by PayPal or other accepted methods. U.S. mailing addresses will pay $19.95 for very carefully packed shipping via U.S. Postal Service, FedEx, or UPS with tracking and delivery confirmation. International purchases accepted only from those who are able to pay with PayPal including shipping by U.S. Postal Service Global Priority Air Mail—fast but costly—no exceptions. Thanks for looking!

*The woofers will be placed face-to-face, with a piece of cardboard between them, and secured with wire or nylon ties at four mounting holes. Then they’ll be wrapped with bubble sheets and placed in a sturdy box with additional protective materials. This will ensure the cones, surrounds, terminals, and magnets are fully protected and that there are no disappointments!

For anyone that's thinking, “...well, that’s a lot of money to spend for some 50 year-old refurbished woofers,” I urge you to go to ohmspeaker.com.  It appears that Ohm is still in business, or the company was resurrected by some new folks? I don’t know.

Study the screenshot I’ve provided below, and, as they say, I hope you’re sitting down. Evidently, Ohm will sell you refoamed original woofers—woofers identical  to the ones I have listed here—for a ridiculous $295 each. In addition, you must pay to mail your original woofers to them, so they can refoam and resell them to somebody else in the future.

So, ask yourself, is it prudent to spend well over $600 (shipping, sales tax) for a pair of woofers that were probably hurridly refoamed by a student working part-time? Exactly. So, if you’re restoring your Model D’s, but don’t want to drop the equivalent of a solid car payment to do it, you’ve found the right listing!