Department - March 2013
The Minus-K isolation platform
How I became involved:
Out of the blue there was an e-mail from Dave
Kushin, a media relations consultant representing
Minus-K asking if I'd be interested in a demo unit
for review. This offer having to do with a page on
my website titled "What's Under Your Turntable"
and my inclusion of a Minus-K isolation platform on
that page. I said: Holy cow yes!!, I'd love to sample
and review one of these. Then there were more email
exchanges this time with Steve Varma of Minus-K and
then a telephone conversation with Steve. This lead
to the selection of a 150 BM-1 as the model for review
in context with my equipment and listening room
What it is, origins etc.:
Minus-K isolation platform. Model: 150 BM-1. Designed
to support and isolate from their surroundings sensitive
instruments like scanning electron microscopes and
other "nano technology" devices, (working
way,,,,, way down to atomic structure levels of magnification),
high powered telescopes, laser holography, and.........as
a side benefit, it turns out that it works really
well with record players. List Price: $4200
But what is it and how does it work...? Minus-K
refers to their technology as "Negative Stiffness".
It is passive. It does not use air or electricity. Rather
than try to describe what does not (at first) seem intuitive
to me, I offer the diagrams below taken from the Minus-K
Who are they: Minus K Technology Inc.,
Vibration Isolation Systems. 460 S. Hindry Ave., Unit
C Inglewood, CA 90301, Tel: 310-348-9656 Fax: 310-348-9638
The platform isolates what stands on it from
the surrounding structural environment as follows: horizontal
isolation to 1/2hz or less.......vertical isolation to 1/2
hz with some variation depending on setting the device up.
In other words, bang on the walls, stomp on the floor and
no matter how badly the building structure vibrates, motion
on top of the platform is restricted to 1/2 hz vertical
and 1/2 hz horizontal (rotation). Please note I have yet
to try the Minus-K during an earthquake event. Yet, I presume
that it will provide substantial benefit during one of those
as well. ;^)
It was Monday evening. Around 6:30pm. Home from work and
I had just finished a modest microwave dinner, sigh......
then there was a knock on the door. It was the UPS driver.
I knew it was UPS because he always knocks the same. I opened
the door and noticed he was empty handed. He said "I
just wanted to make sure somebody was home before hauling
this thing up the stairs". Good thinking, I said and
made note that I was expecting a 90 lb package. Yup, he
said, that would be the one. Using a hand truck, the driver
wrestled the rather large cardboard box up to my unit. Just
after I got the Minus-K inside the remainder of my Monday
evening was spent setting up the platform in hopes of getting
in a preliminary listening session before it was time for
But you know, one really should follow the
instructions on the "Quick Start installation and adjustment
guide". I was tempted to ignore these but always found
myself coming back to the guide!! It's not complicated.
But read the guide first.
Important parts: What you put on top of the
platform needs to meet the weight requirements of the model.
This unit I have is the 150 BM-1. Designed to carry
90 to 155 lbs. The load 'center of mass' needs to be well
centered to the platform or adjustments won't be successful.
As it turned out in the beginning, I either had too much
weight, or not enough. That meant I could not use my granite
surface plate beneath the TT plinth (too heavy) Then I found
that the Double layered solid and massive slate plinth supporting
the Thorens TD124 was almost but not quite heavy enough
to meet the minimum weight requirements. So....I went out
to the garage and rounded up some lead plate remnants I
keep around for various elaborate and nefarious projects
of my own.
In total I had about 20 lbs of lead plates
cut into 7 or eight clean individual smaller pieces. I put
these segments over cork pads to protect the finish on the
Minus-K. This allowed me to add and -strategically- locate
the weights over the platform surface until a decent adjustment
of the unit was achieved. Whew! It did take some work moving
the weights around, adjusting the level screws on the bottom
of the Minus-K. But when in the zone, I found that the adjustments
for vertical and horizontal position finally did work out
as advertised. And then the vertical stiffness adjustment
is used to alter the frequency of vertical oscillations.
And this did dramatically adjust vertical oscillation from
about 3 hz, when I first got the thing working, and then
finally down to what must be close to the 1/2 hz goal.
When finally adjusted I noticed that slight
finger-tip pressure on top of the TT plinth resulted in
a very, very slow vertical (up and down) motion and, at
the same time, some very very slow horizontal rotation.
I also noticed that, as I walked around the unit without
touching any part of the TT stand, my footsteps would trigger
this type of very slow motion. This was very telling. The
TT stand without this isolation was constantly being disturbed
by the room's occupants and their walking around. But up
on top of the platform, these disturbances were reduced
to 1/2 hz motion in both horizontal and vertical planes.
Thinking about the benefit;
Thinking of the size of the record groove in the
stereo Long play record. Thinking of the job that the tonearm
has to do in order to allow the stylus, itself microscopic
in size, to maintain its geometric orientation while, at
the same time, tracking and reading the terrain of the groove.
Thinking of the forces applied to that stylus in order for
it to remain in the groove. And then thinking of how small
of an external force it would take to even slightly disturb
this process. Not much force. Now, think if all external
forces were removed from the record playing process and
all the stylus and tonearm had to cope with was the record
groove itself. Don't you think sound quality might improve...?
My answer would be; "of course it should".
Listening and operating
This is the fun part. Once the Minus-K is dialed-in
for load I get to play many many records over many, many
First things noticed: Background noise is
lower. Micro detail better articulated. Slightly deeper,
better defined bass notes. Tones and textures seem very
slightly enhanced. The record player now articulates more
of what resides within the groove. Did I mention that I
can now jump up and down next to the record player with
nary a skip? Perhaps in some listening rooms that would
be the largest, most obvious benefit. But sound quality
improvements are another benefit.
I've been playing records from every genre
within my library. Full scale symphonic, to chamber music
to rock & roll to small combo jazz. Everything I like
to play, I've been playing during this period of review.
In every case I heard small but noteworthy improvements
in the quality of reproduction.
Sibelius/Burglund on EMI.
Mahler/Abravanel on Vanguard
Beethoven String Quartets/ Quartetto Italiano
Bruckner/ Haitink / Philips
Santana / ST & Abraxas on Columbia
Led Zeppelin II & III (Classic Records)
Miles Davis / J. Coltrane from the Mosaic
Brubeck / Time Further Out, Time In (
Roxy Music / Avalon /(Warner Bros)
Pentangle - Basket of Light (Earmark /
Cat Stevens - Tea... ( A&M )
Beatles - Sgt. Peppers ( on Parlophone)
From Bach to Rock. From Miles to The Beatles.
Every genre benefits from the less perturbed, more placid
stylus-groove interface that the Minus-K provides. At first
I thought that classical music recordings would be the obvious
benefactor because performances show the largest dynamic
range. Those recordings operate from near silence to full
blast bombardments of musical content. And these recordings
do benefit. The more silent backdrop offers this music in
greater relief and definition. And then every other musical
genre I sampled seemed to benefit similarly. And not just
the delicate near silent bits. Very loud hard rock recordings
were also reproduced in greater resolution and focus. The
word "sharper" seems to be a descriptive term
that matches my impression. As noted above, the sound quality
differences were subtle but notable. If footfall is a problem
you're trying to solve, the improvement should be much more
than subtle. This device, properly set up should provide
the ultimate solution.
Operating note: Touch the turntable and
everything on top of the platform goes into motion.
If touched gently, movement is small. If touched more firmly,
movement is larger in proportion to the force from your
hands. This takes a little getting used to. Probably the
biggest trial is brushing the stylus clean. I use a stiff
stylus brush each record side. This requires a bit more
effort and close attention in order to control the hand
operation.....and it is always possible to bend or break
a cantilever if you have an accident while attempting to
brush it clean...! One should not have too many shots of
bourbon prior to doing this.......
So far, so good. I may adopt a different stylus
cleaning regimen. The Onzow Zerodust cleaner allows one
to place the pad on record (not spinning) and simply drop
the stylus on it, then lift off without moving the pad.
That works fine with the TD124 which has clutch mechanism
that lifts the upper platter off the spinning flywheel beneath
and parks it stationary. With a different turntable, the
platter would need to be stopped using this particular cleaner.
It took me more than one adjustment
session to get the Minus-K operating near its advertised
1/2 hz operating frequency. But now that I have some
familiarity to the needs of the Minus-k I would be
more adept at the next setup session
Perhaps it might be useful to compare
the before and after befits with regard to having
the Minus-K in my system. The "After' comparison
tends to include the addition of a deeper vision into
the micro detail parts of the recording. The faintly
articulated bits, while still faint, now appear in
sharper focus. The Macro bits also have sharper focus
as well and appear more solidly described. There is
a sense that bass performance is slightly enhanced
in terms of bass impact, slam and also the sense that
tone and timbre at this frequency are resolved in
slightly higher resolution. Perhaps the idea that
this device helps us to gain a slightly deeper view
of the music within the groove is an appropriate way
to describe the benefit it provides. Because with
it we are allowed to peer further into the recording.
In case there was any question in my mind
whether or not this platform would provide an audible benefit
within my system, I am now satisfied that there is a benefit.
Perhaps that benefit is a subtle one. But it is a benefit
that I value.
Appearance: This platform is
a piece of laboratory equipment and looks like it belongs
in a lab rather than a listening room. So be it. The unit
I have; 150 BM -1 is designed to carry from 90 lbs up to
155 lbs on its top plate. Looking within the unit, (with
the back outer cover removed) we can see why the unit is
so large. The mechanism is scaled up to a size capable of
carrying its load. Smaller more compact models of the Minus-K,
like the BM-8 series will have a much lower profile and
a smaller area foot print. But they must carry lower weight
loads. So, if your turntable weighs, in total, less than
30 lbs, there might be a more compact and lower priced model
within the Minus-K catalog of platforms that would meet
photo: Around 100 lbs of TD124 and a solid slate plinth
standing on the Minus-K.
I did ask for permission to remove an outer
cover so that I could take a peek inside and actually view
the internal parts of this model. Permission was granted
and so I have the following photographs:
While taking the above photos it occurred
to me that it might be useful to take a video of the platform
Next is a link to an Apple Quick-Time video
I took of it. Just click on the "In motion" text
to view the video.
Appologies in advance; My video is low-resolution
(vga) and peers through a rather cheap lens of a 'point
and shoot'. But you should be able to see the speed with
which this suspension oscillates.
More Photos and notes:
transit plugs. These fit down into the 4 holes, of
which one is seen to the right, and use the allen
bolt to thread into the fixture beneath. With the
four transit plugs installed the suspension system
is immobilized for safe shipping and storage. These
have to be removed at installation but come in handy
when loading and unloading the platform because they
---immobilize-- the suspension during setup procedures.
With the transit plugs removed, the allen bolts are
threaded back into the fixture, to serve as a visual
guide for loading adjustments.
Vertical position indicator and the crank below it
for that adjustment.
looking at the vertical stiffness adjust
The listening continues................. and
a good time was had over at chez The Analog Dept. :-)
version of this article