"Arny Krueger" wrote in message ...
"dangling entity" wrote in message
om

"Arny Krueger" wrote in message
...


Here's a link to Nousaine's "bag end" post:

http://www.google.com/groups?selm=20...6%40mb-m23.aol
.com

I think you'll find it interesting.



OK, thanks. I'll check it out.

The Sunfire drive is basically designed to "live" in a small box (in
conjunction with a similarly aspiring passive radiator), inherently.

I don't think so. The box is so small that the system resonance is closer to
50 Hz than 20.


Everything is relative. True 50 Hz is not that low, but consider that
it is relatively low compared to where other typical 10" woofers would
end up if put in that same box. For all its worth, it does "live" in
an unusually small box for a 10" woofer.

Whether or not there is EQing involved, I'm not exactly sure. It's
really just an extreme take on a conventional vented design, AFAIK.

AFAIK it needs lots of eq.


OK, fair enough.



Well, I wouldn't say Sunfire drivers are exactly lacking in the Xmax
category. When considering 20 Hz output however, just about anything
short of a large diameter driver is going to stress the Xmax
capability at even moderate SPL's.

Not quite. There are some drivers in the ca. 12" category that have soooooo
much Xmax that they can move more air than just about *any* 15 or 18 inch
driver. Here's an example:

http://www.jlaudio.com/subwoofers/pdfs/13W7_MAN.pdf


Yes, you are correct. I did not mean to say that there were
absolutely no instances where the contrary exists. The W7 design
represents far beyond the regime of a typical woofer, you must agree.
It is more the exception than the norm, no? Of course, the 13W7 you
link to *is* essentially a 15" woofer as far as physical measurements
of the actual active regions of the driver. (The typical 15" woofer
often includes a good 2" total of space dedicated to gasket and
mounting region) That was a primary influence behind the nonstandard
size of the design.


It's got 1.25 inches of linear Xmax in each direction. 2.5 inches or 64 mm
p-p two-way Xmax. Yup, the cone strokes 2.5 inches with low distortion!


....low distortion not only from the generous motor and suspension
accomodations, but also from the FEA-based optimizations that address
aforementioned motor modulation issues under high current loads. Hey,
I wasn't intending to make a shameless JL Audio plug, but you did it
for me by bringing them up!

I think the Sunfire subwoofer
products present a sort of odd paradigm between compact form and low
frequency capability. The compact form naturally leads to smaller
driver sizes, but those drivers tend to do well in the low frequency
range where other drivers of similar size would not. The particular
driver parameters in combination with the extreme box loading in a
Sunfire enable a capability that not just any 10" driver (for
instance) could do if slapped into a box of that size. That's one
source of the "mystique", I imagine.

The mystique comes from the advertising.


....as it is for a great many products on the market. This is not to
confirm that there aren't also solid engineering features in the
product.

Here's a fairly detailed review of the sunfire. It says that the drivers are
9 inches in diameter and have 30 mm p-p two-way xmax.

http://www.hometheaterhifi.com/volume_4_1/sunsubre.html.


They are 10" drivers in every sense as far as what "industry
standards" considers a 10" driver. The 9" determination was simply to
describe the actual active region of the driver (as would be typical
of most other industry-standard 10" drivers). If that sounded
confusing, all I'm trying to say is that them saying it is 9" in
diameter does *not* mean it is 1" smaller (or .5" on one side) than
any other typical 10" driver. 30 mm p-p isn't too shabby, either.
Maybe not impressive any more now that we are in the "W7 age", but
still decent. I guess it would be comparable to a W6 design, and that
design (though quite old these days) ended up being quite venerable
amongst its competitors for a *long*, *long* time- arguably even to
this day.

That said, a lot of people confuse that capability as a means for
"unlimited sub-bass output", regardless of room conditions. What the
Sunfire does, it does fairly well in a *smaller sized room* (which
would unsurprisingly benefit the most from a very compact subwoofer
design). Naturally, if you put it in a medium or larger sized room,
you will need more units to make that 20 Hz-ish range accessible.
That's just plain physics (not that I'm preaching to you), and there's
no way around that- not even for a Sunfire. I imagine a lot of people
had unreasonable expectations for the product when they put just one
in their medium sized room and expected to be palpitated with air
pressure waves. Naturally, just *one* Sunfire unit would find itself
overextended in such a situation, but people were evidently expecting
it to create miracles. That's my take on it, FWIW.

Finally, I think the one primary compromise to such systems is
increased modulation distortion due to the VC modulating the
permanent magnet circuit of the motor under high current drive
levels (as would likely be encountered with a system that
implements high EQ boosts in the lowest frequency range).

This doesn't seem to be a problem, at least with the Clark
implementation.

It's a phenomenon that effects virtually all VC style speakers.

See item 7 on page 2 of the JL Audio PDF.


From an insider's perspective, it has only been *minimized* to a
particular tolerance, not eliminated. I stand by my earlier
statement. VC's will have current flow, current flow will generate a
magnetic field, and that magnetic field will have an impact on the
static operation point of the motor circuit. You can do things in the
motor design to make it more or less sympathetic to the phenomenon
from there...

Some
are better at minimizing the effect than others, of course.
Naturally, there are few, if any, loudspeaker manufacturers that care
to expose that sort of information about their product (if they have
even bothered to discern it). I don't believe Clark's Duomax
measurements would necessarily reveal its effects, either, unless
studies are expanded to study (very) large signal inputs, rather than
just standard small signal inputs to determine motor strength.

The Dumax can fully stroke large woofers such as the JL Audio unit above,
which means that it can and does apply relatively large currents to the
UUTs.

It does so [the cone displacement] by air pressure (applied by another
woofer), no? Hence, there is no requirement to use large input
currents to get a motor reading. More likely, a very small signal is
used to get motor readings at the various displacements so as to give
the most stable results, unperturbed from unnecessary ohmic heating of
the VC. They *could* do high signal tests (with additional
limitations), but this is not a requirement, nor a default step in the
standard test, AFAIK.