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| RFT BR26 Classic |
I purchased a pair of RFT BR-26 speakers from a garage sale
in the spring of 2008 or 2009 with the intention of using them in the workshop
I share with my father. I had not heard of RFT before and was not able to
listen to the speakers prior to buying them, but made the purchased based
mostly on the appearance of the drivers and the mass of the enclosure. I was
able to buy the pair for $10, so it was not a great gamble. Unfortunately once at home and set up, the foam on one of the woofers began to deteriorate and after a few minutes of operation the surround was damaged to the point that voice coil rub was noticeable at moderate
levels. I sighed and stuffed the cabinets onto a shelf in the corner and forgot
about them. My set of Celestion SL-6 bookshelves made their way into the
workshop and were paired up with a Yamaha CA-610 integrated amp, and then later
with a nice Denon unit. In the summer of 2012 I suddenly had a lot of free
time, and took interest in the RFTs.
Initially I began a search for replacement foams for the
woofers with the intention of fixing and then selling the speakers. Finding a
source with the correct roll dimensions proved to be difficult, but eventually
I found a few potential candidates.
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| Damaged Foam - 5" Woofer |
The
reconingspeakers.com “
RFK5 Angle”
refoaming kit with two foam surrounds, 1.6” dust caps, glue, and shims for
$16.00 seemed like best bet – until I noticed the shipping
cost of $27.75. I’m not willing to pay $43.75 + tax for a set of new foams. The only
other option which matched the dimensions that I could find was on ebay from
“Audiofriends” out of the Netherlands. These foams are specifically marketed
for the RFT BR-26 but again, the cost was beyond what I consider to be reasonable. For
reference, the dimensions I measured from the speakers are as shown below.
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| Woofer foam surround dimensions |
Having spent some time listening to a friend’s pair of
BR-26’s with good condition foams, I was impressed by the high frequency
performance but completely underwhelmed by the bass produced by the original
woofers. As a result, it seemed like a perfect opportunity to plan a potential
upgrade by substituting a modern 5” woofer for the existing faulty one. My
original goal was to find a low cost replacement (ideally a $15 MCM), but
finding an inexpensive 4 ohm 5” woofer proved difficult, and almost impossible
with sensitivity in the realm of 86-87 dB. In the end, the Visaton W130S was
identified as the best candidate (though at $25, it is more than I had wanted
to spend).
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| BR26 Crossover - Note Foil Inductors |
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| Textile dome tweeter with small waveguide |
The BR-26 is crossed over at 2k with a 12dB/oct electrical
slope on the woofer and 18dB/oct on the tweeter. There is a zobel on the woofer, and the tweeter has a notch filter and
overload protection in the form of a 21W light bulb. The Visaton W130S’s
response is smooth up past 3K, with a slight dip around 2100Hz, and in the
pursuit of simplicity (and low cost) will be integrated at the existing 2K Hz
crossover frequency. Fortunately the W130S should work nicely in the existing 8.5L (net
volume) enclosure if converted to a sealed arrangement. This is convenient as
the existing port is located on the front baffle which needs to be replaced
anyways. Sealed alignment yields a Q of 0.73 and an estimated f3 =80Hz
(f6=61Hz) with a nice smooth 12dB/oct roll off.
The new woofer crossover has not yet been designed... I plan to prototype with a miniDSP, prior to buying passive components.
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| Peeling baffle out/off for replacement |
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| Empty enclosure |
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| Back Side |
