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/Archive-All-Audio/Archive-Audio/90s/Audio-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.
Peerless 821615 midrange spec sheet:
http://www.madisound.com/pdf/peerless/821615.pdf
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.
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 and the boost was something
like 3 or 5 dB - I have to look it up to confirm. The AC has a thermal switch in series
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. I'm not sure why my notes have 2.8 mH instead.
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.
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.
Fifth is a front view providing the height positions of each driver also for use in the
CALSOD program.
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/Archive-All-Audio/Archive-Audio/90s/Audio-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.
Peerless 821615 midrange spec sheet:
http://www.madisound.com/pdf/peerless/821615.pdf
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.
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 and the boost was something
like 3 or 5 dB - I have to look it up to confirm. The AC has a thermal switch in series
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. I'm not sure why my notes have 2.8 mH instead.
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.
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.
Fifth is a front view providing the height positions of each driver also for use in the
CALSOD program.
Attachments
Last edited:
Don Keele's extensive review of the 2Ci in the June 1992 issue of Audio page 73 in the .pdf:
https://www.americanradiohistory.com/Archive-All-Audio/Archive-Audio/90s/Audio-1992-06.pdf
He notes that the newer 2Ce model is about to come out so these are very late model
2Ci s.
I always enjoyed reading Don Keele's speaker reviews in Audio because of his excellent
measurements and in depth analysis. It is interesting to note Vandersteen's rated on axis
frequency response of 28 to 29 KHz +/-3 dB and 32 to 21 KHz +/-1.5 dB. This is very
optimistic but not uncommon for manufacturers, Keele writes:
"Salient points of the on-axis curve include a somewhat rough overall response, a gentle
peak-dip combination at 250 and 500 Hz, and a sensitivity of 86 dB, moderately lower
than rated. The curve fits within a fairly tight, +/- 2.5 dB window from 70 Hz to 20 KHz
and is 10 dB down at 35 Hz. Below 40 Hz, the response rolls off at about 18 dB/octave.
A right/left comparison revealed a close, +/- 0.5dB match except for a narrow band
between 3 and 4 KHz, where the levels differed by +/- 1 dB. Note that all measurements
were taken with the grill on, as it is not designed to be removed."
Later in the review Keele does an experiment where he disconnects the Acoustic Coupler
on the rear and vector sums the outputs from the two woofers. He finds that the Acoustic
Coupler drive boosts the output at box tuning of 38 Hz by 5 dB. This is very similar to a
B6 alignment where a peaked high pass provides 6 dB of boost. The -3dB frequency of the
woofer system is lowered from 51 to 43 Hz.
I grew up building my own speakers so these were the first high end speakers that I ever
owned and lived with for several years. My impression of the bass is that it is about equal
to a Large Advent that is also a few dB down in the low 40s, however I often felt that when
the bass notes hit the Acoustic coupler range it seemed as if the source moved to the back
of the system - just a minor annoyance. In time I felt that the 2Ci had a very complicated
woofer system to get bass about the same as a Large Advent. I also felt that they should
reach lower given the spec of -3dB at 28 Hz.
The 2Ci does not pass the sit down stand up test as Keele measures and is well known for
1st order systems with non-coincident drivers the vertical off axis response is quite bad.
So these are only for seated listening.
Keele does his distortion measurements at 50W (20 Vrms) input where the system
produces 96 dB at 41.2 Hz, 101 dB at both 110 and 440 Hz.
Keele does a test where he applies a very high power (kilo Watts) short term burst in order
to explore the displacement limited output without worry for thermal limits. The system
does very well in this test Keele writes:
"With room gain the system exceeds 110 dB above 55 Hz and 120 dB SPL above 180 Hz."
Those are good numbers, the 120 dB figure is not usable because it requires so much
power, and Keele notes that the system is taking 300W just above 38 Hz in the bass
range. I would expect these speakers to work well with a 200W/ch amp except for the
thermal cutout activating with long bass passages.
The problem with the bass is that the thermal switch limits the useful level in my
experience, Keele writes:
"The woofer-protection circuitry was triggered above about 18V rms (46.3W into 7 ohms)
at 38 Hz. From a cold start, at this frequency and level it took about 20s to engage." He
mentions LEDs on the front illuminating, my 2Ci s do not have LEDs.
I'm not sure but I believe that the LEDs and perhaps the thermal cutout were deleted in
later 2C revisions.
It is clear that they do not want you driving this system very hard, the 10 ohm resistors in
the midrange path are only 2W and there are reports of them burning out. RV knows he
can up the wattage on those but I think that they are a way for him to know when a system
has been over powered. He asks customers to return them in such cases which is going to
be very costly just for shipping.
Keele states that the phase fits a window of +/-45 deg from 180 Hz to 20 KHz but it seems
to me that it fits about +/- 25 deg from 200 Hz to 20 KHz - much better.
https://www.americanradiohistory.com/Archive-All-Audio/Archive-Audio/90s/Audio-1992-06.pdf
He notes that the newer 2Ce model is about to come out so these are very late model
2Ci s.
I always enjoyed reading Don Keele's speaker reviews in Audio because of his excellent
measurements and in depth analysis. It is interesting to note Vandersteen's rated on axis
frequency response of 28 to 29 KHz +/-3 dB and 32 to 21 KHz +/-1.5 dB. This is very
optimistic but not uncommon for manufacturers, Keele writes:
"Salient points of the on-axis curve include a somewhat rough overall response, a gentle
peak-dip combination at 250 and 500 Hz, and a sensitivity of 86 dB, moderately lower
than rated. The curve fits within a fairly tight, +/- 2.5 dB window from 70 Hz to 20 KHz
and is 10 dB down at 35 Hz. Below 40 Hz, the response rolls off at about 18 dB/octave.
A right/left comparison revealed a close, +/- 0.5dB match except for a narrow band
between 3 and 4 KHz, where the levels differed by +/- 1 dB. Note that all measurements
were taken with the grill on, as it is not designed to be removed."
Later in the review Keele does an experiment where he disconnects the Acoustic Coupler
on the rear and vector sums the outputs from the two woofers. He finds that the Acoustic
Coupler drive boosts the output at box tuning of 38 Hz by 5 dB. This is very similar to a
B6 alignment where a peaked high pass provides 6 dB of boost. The -3dB frequency of the
woofer system is lowered from 51 to 43 Hz.
I grew up building my own speakers so these were the first high end speakers that I ever
owned and lived with for several years. My impression of the bass is that it is about equal
to a Large Advent that is also a few dB down in the low 40s, however I often felt that when
the bass notes hit the Acoustic coupler range it seemed as if the source moved to the back
of the system - just a minor annoyance. In time I felt that the 2Ci had a very complicated
woofer system to get bass about the same as a Large Advent. I also felt that they should
reach lower given the spec of -3dB at 28 Hz.
The 2Ci does not pass the sit down stand up test as Keele measures and is well known for
1st order systems with non-coincident drivers the vertical off axis response is quite bad.
So these are only for seated listening.
Keele does his distortion measurements at 50W (20 Vrms) input where the system
produces 96 dB at 41.2 Hz, 101 dB at both 110 and 440 Hz.
Keele does a test where he applies a very high power (kilo Watts) short term burst in order
to explore the displacement limited output without worry for thermal limits. The system
does very well in this test Keele writes:
"With room gain the system exceeds 110 dB above 55 Hz and 120 dB SPL above 180 Hz."
Those are good numbers, the 120 dB figure is not usable because it requires so much
power, and Keele notes that the system is taking 300W just above 38 Hz in the bass
range. I would expect these speakers to work well with a 200W/ch amp except for the
thermal cutout activating with long bass passages.
The problem with the bass is that the thermal switch limits the useful level in my
experience, Keele writes:
"The woofer-protection circuitry was triggered above about 18V rms (46.3W into 7 ohms)
at 38 Hz. From a cold start, at this frequency and level it took about 20s to engage." He
mentions LEDs on the front illuminating, my 2Ci s do not have LEDs.
I'm not sure but I believe that the LEDs and perhaps the thermal cutout were deleted in
later 2C revisions.
It is clear that they do not want you driving this system very hard, the 10 ohm resistors in
the midrange path are only 2W and there are reports of them burning out. RV knows he
can up the wattage on those but I think that they are a way for him to know when a system
has been over powered. He asks customers to return them in such cases which is going to
be very costly just for shipping.
Keele states that the phase fits a window of +/-45 deg from 180 Hz to 20 KHz but it seems
to me that it fits about +/- 25 deg from 200 Hz to 20 KHz - much better.
Last edited:
It is a 10" stamped frame woofer in the same box, so acoustically coupled, to the 8" woofer
in the same way as a passive radiator. It is weighted like a PR and resonates with the box
volume. They drive it such that it provides about 5dB of boost over a passive radiator.
in the same way as a passive radiator. It is weighted like a PR and resonates with the box
volume. They drive it such that it provides about 5dB of boost over a passive radiator.
Hey Pete, as far as you know, are there any reasonably close drop-in replacements for the Peerless 821615 midrange in the old 2Ci? I have a pair of 2Ci with one garbage mid. Rather than try to find a good match from an honest seller, I'd be satisfied with dropping in something that physically fits and is electrically a close match (DCR, Impedance, SPL, frequency response). LOL, I know... that's asking a lot, but I don't mind making some crossover adjustments if necessary. 🙂
Perhaps the SEAS Prestige MCA12RC? A little small, but looks like it could work. Considering how many of these Vandys are out there, you would think there would be a word of mouth drop-in suggestion that has been vetted with use.
If I may ask, why is the midrange driver bad? If the foam surround is going bad, you can test with a func generator and sweep thru the mid freq. If you hear buzzing, the foam is likely deteriorated.
Sorry to be so late responding here.
The Peerless 821615 is a very unusual driver with a very high fundamental resonance.
You'd have to use a very small chamber on any driver that you choose to duplicate it.
Also, Qtc goes up as you raise Fc so that is also something to consider.
From memory the Peerless 821615 has ferro fluid which probably helps to lower Qtc
and also with power handling.
The thing is that with 1st order systems you want a very low Fc but somehow RV got
it to work.