I reverse engineered the Vandersteen 2Ci back in 1994 and am posting the crossover
schematics here in order to help others that have problems with burnt out resistors and
for general educational purposes. I never intended to post these in public and never
redrew them with CAD tools. I chose to show how component values were built up from
smaller values, obviously it can be redrawn with some simplifications.
Don Keele's extensive review of the 2Ci in the June 1992 issue of Audio page 73 in the .pdf:
https://www.americanradiohistory.com...io-1992-06.pdf
Stereophile measurements of the 2Ci unfortunately before he got better measurement gear:
Vandersteen 2C loudspeaker Measurements | Stereophile.com
The 2 series has gone through several model revisions over the years including parts
changes even with the suffix retained such as 2Ci. From what I remember speaking
to RV the rear plate has Model 2 written on it but the serial number will end in a letter
if it is a later model. My serial numbers end in i for example.
Mine have 1" Audax ferro fluid cooled tweeters, Peerless poly cone mids that look
exactly like the 821615, custom Vandersteen 8P2C woofers and a stamped frame
acoustic coupler. Both woofers have rubber edges and the mid has a plastic edge - no foam.
TWEETER - out of production:
The tweeter is an Audax DTW9X8T25FF8, the 9X8 is the rectangular face plate size in
cm, 25 is the dome size, FF indicates ferro fluid, and 8 for the 8 ohm version. There were
many versions of this tweeter, the DTW100 was the 100 mm round version, there were
4 ohm versions, and I think big and small magnet versions. This has a small face plate
and was probably the small magnet version. This has a hemispherical dome, the next
version in the evolution had a catenary shaped dome. This is the current production of
the big magnet, catenary dome version with a bigger rectangular face plate:
https://www.madisoundspeakerstore.c...-12x9-1-textile-dome-tweeter-with-ferrofluid/
I have the data sheet around here somewhere for the correct tweeter and will try to find it.
MiDRANGE - out of production:
Peerless 821615 midrange spec sheet:
http://www.madisound.com/pdf/peerless/821615.pdf
WOOFER - custom by Vifa:
I was working on a design inspired by the 2Ci around the time that I did this work,
and I ordered a pair of the Vifa P21W020 which were the closest stock Vifa to the
custom 8P2C. This Vifa woofer has been brought back by Scan Speak under the
same P21W020 part number and the spec sheet and response curves look like a
cut and paste from those from Vifa:
https://www.madisoundspeakerstore.com/approx-8-woofers/scanspeak-classic-p21wo20-8-woofer-poly-cone/
What is interesting is that I measured the 8P2C and the Vifa woofers and the Fs of
the Vifa s measured higher than spec and Vas lower making them very close to the
8P2C. Visually they look the same except for the edge being slightly wider in the
8P2C. They sounded the same with the 8P2C handling very slightly more Xmax.
MID/TWEETER CROSSOVER
First is the mid/tweeter crossover, it can be seen to be a simple 1st order cap to the
tweeter, one ohm fixed resistor pad, an Lpad, a shunt 20 ohm fixed R, and an RLC
with a resonance at 918 Hz - very basic.
The mid also has basic HP and LP first order filters with an Lpad and some shunt
resistance to flatten the driver impedance.
WOOFER/ACOUSTIC COUPLER CROSSOVER
Second is the woofer/coupler crossover with a 2.8 mH inductor providing some baffle
step and a total of 554uF HP to the main 8" woofer and a huge 20 mH inductor to the
10" acoustic coupler (AC) assist. They share a common air cavity with the AC coupled
like a passive radiator but with drive to boost the output. Keele, in his Audio Review
confirmed this by disconnecting the AC and noting the change in output level around
Fb the box AC resonance. That was 38 Hz from memory with 5 dB of boost. The AC has a
thermal switch that trips at about 5 minutes into a bass heavy track played at a level that I
like, it is also close to the displacement limit of the main woofer. Some say that the switch
doesn't age well and the trip point lowers and suggest removing them. Note that in
the next post the picture of the woofer inductor has the number 3 on it and I seem to
remember it being 3 mH and I'm not sure why my notes have 2.8 mH instead.
Edit: Notice the date on my notes of 1994 so that was a while ago, when I wrote the above
I forgot that the picture below is of the 2Ce that probably has a 3.0mH inductor but thinking
back I now trust the 2.8mH value in the schematics for my 2Ci s.
ACOUSTIC COUPLER MEASUREMENTS:
PICTORIAL XO LAYOUT
Third is a pictorial layout of the double sided circuit board which is glued in and very
difficult to remove so I didn't. I used an ohm meter to confirm how the traces are
connected.
CABINET SIDE VIEW
Fourth is a side view where I measured the driver offsets in order to enter them into
CALSOD, the program I used to model the system.
CABINET FRONT VIEW
Fifth is a front view providing the height positions of each driver also for use in the
CALSOD program.
CROSSOVER BOARD PICTURES (2Ce burnt resistors)
Next is a snapshot of a 2ce crossover board, not this model but looks exactly like mine:
And the back:
schematics here in order to help others that have problems with burnt out resistors and
for general educational purposes. I never intended to post these in public and never
redrew them with CAD tools. I chose to show how component values were built up from
smaller values, obviously it can be redrawn with some simplifications.
Don Keele's extensive review of the 2Ci in the June 1992 issue of Audio page 73 in the .pdf:
https://www.americanradiohistory.com...io-1992-06.pdf
Stereophile measurements of the 2Ci unfortunately before he got better measurement gear:
Vandersteen 2C loudspeaker Measurements | Stereophile.com
The 2 series has gone through several model revisions over the years including parts
changes even with the suffix retained such as 2Ci. From what I remember speaking
to RV the rear plate has Model 2 written on it but the serial number will end in a letter
if it is a later model. My serial numbers end in i for example.
Mine have 1" Audax ferro fluid cooled tweeters, Peerless poly cone mids that look
exactly like the 821615, custom Vandersteen 8P2C woofers and a stamped frame
acoustic coupler. Both woofers have rubber edges and the mid has a plastic edge - no foam.
TWEETER - out of production:
The tweeter is an Audax DTW9X8T25FF8, the 9X8 is the rectangular face plate size in
cm, 25 is the dome size, FF indicates ferro fluid, and 8 for the 8 ohm version. There were
many versions of this tweeter, the DTW100 was the 100 mm round version, there were
4 ohm versions, and I think big and small magnet versions. This has a small face plate
and was probably the small magnet version. This has a hemispherical dome, the next
version in the evolution had a catenary shaped dome. This is the current production of
the big magnet, catenary dome version with a bigger rectangular face plate:
https://www.madisoundspeakerstore.c...-12x9-1-textile-dome-tweeter-with-ferrofluid/
I have the data sheet around here somewhere for the correct tweeter and will try to find it.
MiDRANGE - out of production:
Peerless 821615 midrange spec sheet:
http://www.madisound.com/pdf/peerless/821615.pdf
WOOFER - custom by Vifa:
I was working on a design inspired by the 2Ci around the time that I did this work,
and I ordered a pair of the Vifa P21W020 which were the closest stock Vifa to the
custom 8P2C. This Vifa woofer has been brought back by Scan Speak under the
same P21W020 part number and the spec sheet and response curves look like a
cut and paste from those from Vifa:
https://www.madisoundspeakerstore.com/approx-8-woofers/scanspeak-classic-p21wo20-8-woofer-poly-cone/
What is interesting is that I measured the 8P2C and the Vifa woofers and the Fs of
the Vifa s measured higher than spec and Vas lower making them very close to the
8P2C. Visually they look the same except for the edge being slightly wider in the
8P2C. They sounded the same with the 8P2C handling very slightly more Xmax.
MID/TWEETER CROSSOVER
First is the mid/tweeter crossover, it can be seen to be a simple 1st order cap to the
tweeter, one ohm fixed resistor pad, an Lpad, a shunt 20 ohm fixed R, and an RLC
with a resonance at 918 Hz - very basic.
The mid also has basic HP and LP first order filters with an Lpad and some shunt
resistance to flatten the driver impedance.
WOOFER/ACOUSTIC COUPLER CROSSOVER
Second is the woofer/coupler crossover with a 2.8 mH inductor providing some baffle
step and a total of 554uF HP to the main 8" woofer and a huge 20 mH inductor to the
10" acoustic coupler (AC) assist. They share a common air cavity with the AC coupled
like a passive radiator but with drive to boost the output. Keele, in his Audio Review
confirmed this by disconnecting the AC and noting the change in output level around
Fb the box AC resonance. That was 38 Hz from memory with 5 dB of boost. The AC has a
thermal switch that trips at about 5 minutes into a bass heavy track played at a level that I
like, it is also close to the displacement limit of the main woofer. Some say that the switch
doesn't age well and the trip point lowers and suggest removing them. Note that in
the next post the picture of the woofer inductor has the number 3 on it and I seem to
remember it being 3 mH and I'm not sure why my notes have 2.8 mH instead.
Edit: Notice the date on my notes of 1994 so that was a while ago, when I wrote the above
I forgot that the picture below is of the 2Ce that probably has a 3.0mH inductor but thinking
back I now trust the 2.8mH value in the schematics for my 2Ci s.
ACOUSTIC COUPLER MEASUREMENTS:
Vandersteen 2Ci Acoustic Coupler Info
Came across these notes from 2005 and thought they might help if anyone needs to replace one. One of the acoustic couplers in my 2Ci s had the spider joint broken right at the voice coil. I pried up at the glue joint for the outer edge of the surround and it broke easily, so I removed the...
www.audiokarma.org
PICTORIAL XO LAYOUT
Third is a pictorial layout of the double sided circuit board which is glued in and very
difficult to remove so I didn't. I used an ohm meter to confirm how the traces are
connected.
CABINET SIDE VIEW
Fourth is a side view where I measured the driver offsets in order to enter them into
CALSOD, the program I used to model the system.
CABINET FRONT VIEW
Fifth is a front view providing the height positions of each driver also for use in the
CALSOD program.
CROSSOVER BOARD PICTURES (2Ce burnt resistors)
Next is a snapshot of a 2ce crossover board, not this model but looks exactly like mine:
And the back:
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