OPEN BAFFLE SPEAKER PROJECT
the final conclusion of part II, I said:
best part of the surprising performance of this design is that A)
it can be enjoyed stand-alone and B) it can be used with your typical
sub. I fully expected this design to require a broadcast system
to be usable. A system that would include 2 high quality microphones,
a high quality microphone preamp, a second stereo amplifier and
a second pair of woofers in their own respective cabinets placed
somewhere in the room.
intend to continue to implement the broadcast system to see what
happens, but it now clearly becomes optional for those who have
the money and want to pursue it."
it can be enjoyed stand-alone on certain music sounding better than
real while sounding painfully thin on certain music. B) it can be
used with your typical sub, yes. However, when implemented true
to it's original design concept with the broadcast section both
A and B would by comparison sound like a complete joke. Therefore
while it could be used stand alone if you don't like a lot of bass,
or with a sub, after hearing it with the intended broadcast system
we will officially discourage both A and B !!!
NOW APRIL 2008
taking 6 months off and deliberately not listening to these speakers
I was feeling in a far more objective mood than when I left off. Allowing
the proud papa syndrome to wear off as well as the desire to have
this speaker fly stand-alone, I was ready to pick up where I left
off and give these things a real objective listen once again as
stand alone open baffles.
used stock CD player as a source - this will handicap things a bit
and let me hear what the worse case scenario is going to be. I
picked up a Neil Diamond CD that I knew didn't have a bass heavy
mix, in fact typical of many rock recordings it always sounds thin
on any system. (*Side note: because of this I have never taken the
CD seriously and rarely ever played it.)
put one of my 6 watt triodes on them and let it warm up for a bit.
My ears are now someone else's (a nifty side effect of taking
6 months off to see if you still like something) and I'm ready to
hear everything wrong with it.
plop the disk in and press play. Now trying not to like them I had
to admit the clarity was surprising. However this thin sounding
recording was just screaming for some meat on it's bones. Within
3 or 4 minutes I had made a clear decision that this wasn't going
to fly and turned it off. A few minutes later after some disgust
wore off I turned it back on because I wanted to hear the sound
inside the cavity again. I placed my ear near the opening
and was instantly entranced by how rich and clean the bass lines
were and found myself really enjoying the CD.
DECISION TO MOVE FORWARD
think my exact words to myself were something along the lines of
"quick screwing around and finish the damn project so you can
hear it work" Yes, let's stick to the original design
and complete it. On to the broadcast system.
is where things get really interesting so if you've read this far,
you'll probably want to continue. Again, to experience worse
case (real world) performance rather than use $600.00 microphones
on exotic tube mike preamps, I dug up some cheap Audix drum
mikes and fed them into a $200 Berringer mixer feeding an old Ross
solid state amp. If this concept actually works as well as
I predicted - it should have livable results even with junk
gear. If the test fails or sounds like crap with the junk gear than
something is fundamentally wrong and the best good gear would do
is make it almost right.
TALK ABOUT REAL SOUNDING BASS - EPIPHANY NO. 1
setting the up the electronics for the broadcast system I made several
fascinating discoveries and actually had a couple of epiphany's
that I'll never forget. The first epiphany came after listening
to the non-compressed natural bass of the cavity against the same
thing coming out of a pair of typical box speakers. This comparison
would be all but impossible for most audiophiles to make because
you would need a cavity design that closely copied the Zen Open
Baffle and to date the design hasn't been released so nobody has
spent 30 years listening to box speakers of all kinds as well as
every other kind and well understand the colorations associated
with boxes. My full
range direct driven Acoustats
make all but the very best box speakers sound silly and the most
obvious difference shows up in the bass clarity. That coloration
werew hear with boxes is gone. I've designed a few speakers
and up until this design I thought that coloration was cabinet resonance
and the standing waves inside the cabinet etc.
I realized is that the pressure created during lower frequency cone
excursions not only compresses the air inside the cabinet but also
seems to be compressing the distance between wavefronts and changing
the pitch. These altered waveforms work against the cone causing
smearing across the original phase angles of the driver. They
also slow it down.
resonant cavity of the Zen Open Baffle has roughly 1/10th of the
energy in it's panels as it would if there were a driver mounted
in it like any box speaker. Therefore when you hear the sound
inside the cavity, there is no distortion from panel resonance to
is also almost zero pressure inside the cavity so the sound inside
is not aggravated or compressed by the pressure.
a box speaker, even with the worlds best crossover, there will be
sound inside the cabinet that falls well above the cabinets resonant
frequency. These mid's and low level highs inside box speakers
leak out of the ports and through the speaker cone and by the
time they leave the cabinet through either of these two mediums
their phase angles no longer match the wavefront coming off the
front of the cone. This is where open baffle speakers have
such an advantage. There is no pressure, and there is no cabinet
to poison the speaker cone. However, open baffles have no bass per
say unless using multiple drivers or large drivers in large baffles.
That means most open baffle speaker systems use a sub that
can't sound as good as the open baffle because it's in a box. It
also means that if your not doing that, you've lost your single
point source by using more than 1 driver and along with it probably
small size making the front of the baffle nothing more than a large
sound mirror for reflecting sound from the room back to the listener
- making it hard for the speakers to completely disappear. If
you kill the point source conflict from multiple drivers by pasively
crossing one over to reproduce only low frequencies, then you have
poluted the puzzle with a crossover.
bass inside the resonant cavity of the Zen Open Baffle is seeded
by the single
8 inch full range driver (DFR-8).
That means the sound inside the cavity is virgin or pure
in the sense that some other driver or electronics or both didn't
create it. Because of this, it is seamless and perfect in
it's coherency with the main driver - on an order of magnitude better
than the best implemented subs (which I have).
HIGH DEFINITION BROADCAST SPEAKERS
is impossible for a typical box speaker to reproduce bass as realistically
or accurately as the bass that is found inside the cavity. Again,
the only thing that sounds like what's in the cavity are my
Acoustats / but to own something as good today would start
at $100,000 and require a large room and your willingness to live
inside the sweet spot.
the sound inside the cavity is properly broadcast into the listening
space it would be like hearing the single 8 inch full range driver's
own bass in any proportion necessary to achieve the desired frequency
balance. The trick to that is the transducer. The speakers
used for the broadcast need to be anything but a conventional box
speaker and capable of the incredible speed that is only possible
in an enclosure by having nearly perfect dampening like a straight
horn. Regrettably such a device would be too large too expensive
and create room treatment issues just by it's size. The only
other design up to the task is the HDT cabinet because of it's tremendous
speed. The HDT cabinet is a cross coupled multi-chamber design
with 5 tuning frequencies across over 2 octaves creating a death
grip on the woofer cone. The wide band dampening makes it
one of the most linear box designs I know of. If we used anything
less, such as a simple reflex cabinet, be it sealed or ported, it's
own colorations would mask the beauty of the cavity sound to the
degree where you would loose 90% of the benefit.
the HDT's used as the broadcast speakers it is possible to accurately
capture the magic of the cavity and seamlessly allow it to escape
into the listening space. The broadcast signal is relative
to the mic placement, type and so on. The mic will pick up
background levels of high frequency information coming off the rear
of the driver as tiny amounts are entering the cavity . This
allows a natural shelf to develop between the low frequencies of
the cavity and the cut off of the driver in it's baffle. By
having this small trace of full range ambient sound up to about
5kHz and between 12db and 18dB down from the reference level of
the Zen Open Baffles, the harmonics of the bass lines in the recording
remain in tact from both positions on the arc. I'll talk about
the arc soon. Anyway this is not possible with a sub approach
and I find it to open up the music in a way so vivid that it has
me questioning my Acoustats. I believe this must be a pretty
natural form of desirable ambience in just the right trace amounts
to lock in some really jaw dropping playback.
TALK ABOUT HOLOGRAPHIC IMAGING - EPIPHANY 2
few people I know have been fortunate enough to build a pair of
Imperial SO's and use them as the bottom end behind a pair of good
box speakers. Not just for reference quality 20 cycle on up response
but because of what it does to the imaging and scale of their main
speakers. It takes the sound stage and explodes it in size
and makes everything sound more logical and coherent. The imaging
always appears far more organized and locked in space giving breath
taking focus. You can see them behind the Zen Open Baffles
in the picture below. Over the years I've tried more speakers
in front of these 28 cubic foot horns than I can remember, and the
majority of them gained this superior imaging and scale every time.
scale in particular I've always attributed to the size of the wavefronts
from these big monsters, and the imaging I theorized was the result
of the mid and high frequencies being somehow organized by the large
fundamental wavefronts. I was apparently wrong on both counts.
the perfect placement for the broadcast speakers (HDT's) turned
out to be on the outside edges of my listening arc. That put
them about 1 foot away from the walls, but towed in true to the
arc as are the open baffles. The picture below shows the 115
degree arc proportional in my listening space.
I got this set up and listened to it I realized quickly that I was
getting the same sense of scale and improved imaging as I did with
the Imperials on other speakers. In fact the sound was so
similar it was like having the imperials on. There was one
difference that stood out, and that was the imaging and something
absolutely magic about the bass. Far and away the cleanest,
most open natural sounding bass, and fast, fast, fast. Deep
and Rich with non-congested weight and scale that made the presentation
far superior to the imperials in combination with these or any other
speakers I've tried - something I never expected to top. Yes, it
was the magic of the cavity and the implimentation of the arc that
took the bass to this new reference level.
this blew my theory about the large wavefronts somehow organizing
the mids and highs into a more coherent 3D image. The epiphany
was realizing it's the width cues that we get in real life
that are missing in almost all 2 speaker setups. Low
frequencies that emanat from the same location as mid and
high frequencies in real life, such as a band, always find the boundaries
of the venue and wrap back in on the listener so the ear expects
to hear these low frequencies come at it from the sides and
arced back to the center. If the listening arc is too small,
this is impossible.
two subwoofers placed at the outsides of the arc will not accomplish
the effect I am hearing. The speakers must be able to coherently
play not only the low frequency information at the same level as
the Zen Open Baffles but also reproduce the harmonics of those low
frequency's for at least 8 octaves with high frequency content
at background levels. Then there is the natural ambience of
those frequencies that escaped from the main driver into the opening
of the cavity to consider. This is the source of the high
unbelivably real imaging.... perhaps it's the width cue that releases
the brain from processing why information is missing from this area
and lets it better process what is at the focal points.
interesting is that the Zen Open Baffles do a fantastic job of imaging
by themselves, but when the broadcast is added it simply transforms
the imaging of the ZOB to jaw dropping heights and floats in the
room independent of the speakers and regardless of where you sit
or stand. It's just happening. In that respect it is performing
like our Radial
should be understood also that you do not hear the broadcast speakers
until you get your ear around 1 foot away from them, so they are
never directly noticed. I've had several people listen to
the setup without knowing anything about it and no one realized
the broadcast speakers were on. Their level is of course adjustable
based on the gain setting of the broadcast amp giving us a much
needed tone control for listening to lean recordings. You
can have as much or as little weight as you want, the imaging remains
unchanged. Adding a little extra weight to a recording in
this manner does not thicken up the bass or mud it up like it tends
to on typical box speakers. Regardless of the level you are
struck by how incredibly clean and open the bass is, and how richly
it layers out without ever showing even the slightest hint of strain
or compression or distortion.
only way to really present this design is in it's entirety. It
is a 4 speaker system. ZOB for the mains and a
pair of HDT's for
the broadcast. And when marveling at this combo it occurs
to me that I have never heard my amplifiers sound this good and
since the sound you will hear from this design will only be as good
as the weakest link, it makes sense to also offer a 4 channel amplifier
with a built in microphone preamp (all tubes) to run it. That
is my next step, developing the electronics. I have every
confidence that this system would represent the flagship of everything
I've done to date so it should be approached from that perspective.
Someone who wants the very best there is...
already been bombarded with the knee jerk statement, yea but its...
four speakers! Like this is somehow a problem. My response
is always the same... you already probably have 2 pairs of speakers
in your possession now, yet you can only enjoy one pair at a time.
Sell it all up and try this, it's the best way I know to make
every dollar you've spent on audio gear count for something.
it is possible to have good results with lower cost electronics
for the broadcast, anyone owning a great sounding amplifier and
willing to build their own ZOB array from plans will have an
opportunity at the completion of this project.
new name for this project is now going to be called:
ZEN OPEN BAFFLE ARRAY.
BTW: The Neal Diamond CD turned from a less than pleasing
recording that was avoided for years into an absolutely incredible
sounding live experience. It felt and sounded totally real
when played on the array and turned out to be a most impressive
recording. Finally a system that can make everything sound
right. Instead of listening to 10% of my music collection
I can now enjoy 90% of it. When you can strike the right frequency
balance, it is surprising how many bad recordings were actually
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