Getting Sidetracked When You're Already
Sidetracked
I'm sure I'm not the only one who gets a little distracted by other
projects while trying to work on just one. My intentions about 4
months ago was to kick off a pair of Swans M3 tower speakers. Then
about 1 month ago I began working on a pair of mini monitor
speakers. Then about 1 day ago, I built myself a pair of bipole
surround sound speakers. I pretty much designed them, built them
and finished them all within one weekend. Who says I can't finish
a project when I start one? So without going into any detail on
its design, I'll just show off all the pictures of it. Tomorrow
I'm going to paint them and finish them entirely. For now, this is
what I've got. Now I'm not sure exactly if they're really dipoles,
or what kind of surround category they fit into. They've kind of
got the Bose direct-reflecting thing going on. Similar design to
PSB's 10S surround sound speakers also. They should work great for
just basic surround sound and ambient effects. I suppose they'd
really suck for just music. But then that's not they're
intent. Enjoy the pics. They're big in size but small in
bytes. Well around 50K small. The fleck paint was my
wife's idea. I've wanted to use the stuff it the past, but never
wanted it to totally mess up a pair of speakers that were months in the
making. These were a good pair to try it out on. My initial
thoughts are that this stuff is awesome! It goes on so easy, and
has a very rustic look to it. It should also fit the decor of the
room. More to come later!
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Some Theory on Bipolar Surrounds
First thing everybody is wondering is, "So are the drivers wired
in phase or out of phase??" Right now they are wired
in-phase. There is no acoustical null when listening directly over
the center of the speaker. This is why they are bipole surrounds
and not dipole surrounds. I will not be placing them exactly to
the left and right of my couch either. So to explain why I have
gone with a bipolar design and not a dipolar design, I will look towards
PSB and their 10S surround speakers which I mimicked in my design here.
"... It is a bipolar design that combines two
identical panels that employ the Image 5-1/4-inch woofer and the Image
1-inch aluminum-dome tweeter. The angling of these two panels outward
creates a diffuse soundfield, and the connection of the two speaker
arrays in phase also aids localization of sound when sharply placed
effects are present on a soundtrack or a music recording field.
Over the past few years, the growing dominance of Dolby Digital surround
recordings has created a need for a speaker on the surround channel that
would be neither a conventional direct radiator nor the dipole design
that came into being during the Dolby Pro-Logic era. The dipole created
a welcome diffusion of sound, but it was designed and placed to create a
"null" at listeners' usual seating position because there were
and are no directional effects in Pro-Logic's monaural surround channel.
This became increasingly unwelcome to most of us as Dolby Digital took
over, because the directional effects that appeared in these recordings
weren't sharply registered by the dipole design. And while conventional
direct radiator surround speakers do handle the need for pinpointing
some surround effects, many listeners miss the ambience of the dipole's
diffused surround field.
The Image 10S offers the best of both worlds. Its surround ambience is
very convincing, thanks to the way the two speaker panels are angled to
radiate indirectly. But because the speakers are wired in phase, in a
bipolar design, rather than out of phase in a dipole array, they also
provide all the localization needed for soundtracks with directional
surround effects. Surround recordings of music also profit greatly from
the soundfield of the 10S, and small rooms sound much "larger"
than they do with direct radiator speakers. The more demanding you are
about surround sound, or the more demanding your listening conditions
are, the more we think you will appreciate what the 10S has to
offer."
I couldn't have said it better myself. So
bipoles they are. There are some other factors that go into a
dipole as well that I didn't want to have to worry about. First of
all each driver needs its own enclosure. I didn't place a dividing
barrier between the two drivers. They share the enclosure.
Also the bass response in dipoles is minimal at best unless you place a
high pass filter on one of the drivers, so that only the other driver is
producing the lower frequencies. Then there's placement of dipoles
and making sure that the in-phase drivers point forward toward the main
speakers. There's just a lot more to the dipole. I have
tried out the speakers as dipoles and they do a marvelous job of
creating that "where's the sound coming from" feel. It's
quite amazing actually. It's as if your ears were deceiving you
the way the sound seems to reflect off everything and doesn't appear at
all to actually come from the speaker itself. At any rate, I like
the bipole design better.
Updated 09-27-03
After several months of listening to these surrounds in a bipole
configuration, I decided to try out the dipole side of things.
This is where the woofer and tweeter that face forward are wired out of
phase with the woofer and tweeter that face toward the rear. This
configuration works best when you can mount the speakers at ear level
exactly on either side of the listening position, which is how I
currently have it set up in my home theater. Compared with the
bipoles, I love the dipole quite a bit more. They truly do give
the real effect of a ((surround sound))). Since there is little or
no directionality to the speaker, due to the out of phase drivers, the
surround effects just appear to come out of no where. It's really
pretty awesome sounding. Not to mention that since the cabinets
were so small, the two drivers were constantly fighting for air space.
Now that they are wired out of phase, the nasty hump around 100 Hz (that
I could constantly hear) is gone. There's probably massive dip in
that same spot instead, but these speakers were never meant to provide
any substantial low frequency anyway. I'll take the softer
sounding dip over the boisterous hump any day.
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