B&W 802 s3 Up-Grade
A client brought in these B&W 802 s3 speakers for a possible upgrade of
crossover. Not necessarily a new crossover, but at least a replacement
of existing components with the best possible coils and caps within a
decent price range, hence this article on how to up-grade your nineties
Download 802 s3 manual here.
What seen above is the simulations and performances performed from as-is crossover and an experimental crossover, the latter producing a more flat response. The thing is the the "perfect" crossover makes a too forward sounding speaker, too much right in your face. I link this to the overall power response being excessive in upper mid/lower treble from the "flat" crossover due to dispersion of the small midrange driver. Sometimes this goes well, sometimes it doesn't, and the sad thing is that we're unable to predict this alone from the dispersion characteristics of the midrange driver. It must be tried and the overall voicing of a speaker system depends on listening tests of a wide range of musical genres trying to balance power response with a proper tonal balance.
Above to the left: SPL from drivers measured at 0.5 meter distance with an input equal to 2.8V/1meter. Sensitivity of the bass drivers is around 87 dB, where the middriver is highly efficient with around 92 dB/2.8V. Tweeter level a little uneven, but around 87 dB possible due to the 10-20 kHz range. The small midrange cabinet makes a serious bump around 700-1500 Hz, not an easy response when it comes to crossover. Above to the right mid and tweeter with different scaling.
Above and below horizontal dispersion of tweeter and midrange driven directly without crossover. Both units display good dispersion, which may account for the need to suppress lower-treble range to balance the overall presentation. The midrange bump at 1 kHz poses a problem in terms of crossover design and not fully flattened out, puts its make on the overall voicing of this system.
Final results from up-graded crossovers.
PICS from the workshop
All wires are replaced by 1.3 mm silver plated copper in Teflon sleeves. We can't replace than last 3-4 centimeters to the tweeter, but what's seen above will do. Make sure you get driver polarity right. Tweeter red is PLUS, tweeter blue is MINUS.
Above left: For the bass drivers the terminal to the right, when seen up-right, is PLUS (original yellow wire). Right: Midrange driver with the PLUS terminal to the right when seen up-right. Replace like seen above and ditch the connectors and solder wires directly to the terminals.
Left: The midrange driver is mounted with metric screws and a rubber grommet
is inserted to reduce vibration. Nice details. Right: When you have pulled new wires through the hole to the bass
cabinet, make sure adding a lot of filler to eliminate any ventilation
to the bass cabinet. I used the same stuff as I use for mounting
crossover. The mid cabinet is closed and completely
filled with damping material. The midrange cabinet appear to be made
from low-resonance material and is attached to the bass cabinet by a
single threaded rod allowing wires to go through and the cabinet to be
rotated. The latter may not be such a great idea as it allows the mid
cabinet to rock slightly. Ideally insert a robber wedge at the rear
between the two cabinets to reduce rocking once optimal position has
Left: Removing the bottom panel with the crossover may take a little
help from a 6 mm screw and a plier. Gently loosen the base plate. Right:
To enable removing the bottom panel you have to cut the two fasteners
holding the wires in place behind the bass drivers.
Left: Cut all wires from this terminal block, pull out the crossover and de-solder all wires including those from the binding posts.
The original crossover with electrolytic cap for the midrange and Bennic for the tweeter. Coils are not necessarily bad, but the midrange coils are not baked (backlack/self-binding wire) as should be to reduce vibration. New coils obviously are either baked or the tightly wound foil coils.
Pull out the rear middle section damping material and insert the bass crossover. Push up to the lower bass driver hole and fasten with two screws.
Above to the left the base plate holding the original crossover. The area that can be used for the new crossover is ~183 x 229 mm. To the right first time set-up of new crossover allowing me to AB test the two speakers. Quite a difference in sound I must say.
Above, left: The mid-tweeter section is the easy part. Connect input to
terminals and connect mid and tweeter.
There are some hidden information in the list below to avoid any dealer to do a copy-paste, and that's the series resistance of the coils. These need to be fairly accurate for some of the coils. For the bass coils I have chosen two coils with a lower series resistance compared to original. This doesn't impact sonics, but does increase power handling a little. The original tweeter coil uses very thin wire to reach desired DCR, where I have chosen to use a coil from thicker wire and add a series resistor to make the required total DCR. This coil is very important for the tweeter roll-off. I have added two resistors for possible tweeter attenuation. The 26 uF mid series capacitor is made up from 22+3.9 uF Superior-Z caps. I haven't made any middriver attenuation options, but should you want to try a slightly lower midrange level you may try 2.2 Ohm in replacement of the current 1.65 Ohm made up from 2 x 3.3 Ohm. It's not really necessary to use 20 watt resistors here. A single 10 watt resistor will do.
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I decided to split the crossover for the sake of space at the bottom and for getting the heavy bass coils as far away as possible from the midrange tweeter section. The bass crossover is placed as seen on photos in between the bracings behind the bass drivers.
Above crossover board for midrange and tweeter. I have added two optional resistors for tweeter attenuation, 0.47 Ohm or 1.0 Ohm. If you don't want to use these, connect C1 directly to the input point. See wiring below.
I've already commented on the sound in the intro to this article and
what you get from primarily replacing poor electrolytic caps for the
midrange and mediocre BENNIC caps for the tweeter is significant
increase in overall transparency and resolution. The compressed sound of
the electrolytic caps is gone. What stood out from the new crossover was
what I first experienced some 10 years ago when I first tried super
caps, the initial confusing experience of music being darker and
brighter at the same time. The resolution of super caps allows you to
focus on individual aspects of the music in a way poor capacitors don't.