My INF10 subwoofer has almost always performed to my
satisfaction. Almost. It had one particular problem that could be quite
annoying at times. Whenever it was called upon to reproduce a fairly large
low-frequency signal, the driver would respond with a loud cracking noise (caused most
likely by the voice coil former slamming into the back plate). This might have
something to do with the driver being theoretically capable of handling only 60W in this
particular alignment and I was driving it with a 270W amplifier!
time I've been looking for a replacement driver that will work well in the box I
built for the INF10 (2.5 cu.ft. tuned to 21 Hz), but most of the 10" drivers I came
across either had too high an Fs, too low a Vas or Xmax, or were simply to expensive
(>US$100) to consider as a suitable replacement.
My luck changed a few months ago when ACI announced a sale on their subwoofer
drivers. I've always been interested in their SV10 10" driver (with a rated Xmax of
16mm!), but the price was just a little to expensive. However, the sale brought the
price down to $99, so...
Physically, the SV10 is a beast - it makes the INF10 look very wimpy in
comparison. Specs-wise, the drivers' published parameters compare as follows:
Some points about the specifications that might be of interest:
||The lower Vas, Fs and Qts of the SV10 result in a
driver that is just over 4 dB less efficient than the INF10. However, as the SV10's
impedance is less than that of the SV10, the difference in sensitivity works out to
considerably less - just about 0.3 dB.
||The SV10's Xmax is twice that of the INF10, and its
Vd works out to be roughly that as well.
||Because of the greater Vd, the SV10 driver can absorb
considerably more power (225 W compared to 50 W) before reaching its theoretical excursion
limits in a 2.5 cu.ft. box tuned to 21 Hz. As its sensitivity is almost identical to that
of the INF10, the SV10 will produce at approximately 3dB and greater peak linear SPL at
all frequencies, as the graph below suggests.
||The SV10 will produce a response that's 3dB at 20.5
Hz in the given alignment. This suggests that low frequencies may be exaggerated (as
compared to the INF10 in the same alignment) when "room gain" is taken into
effect. But this of course depends on how much the "room gain" of my
living room actually adds to the subwoofer's response at low frequencies.
Shown below is the predicted frequency response of both systems up to their
theoretical peak SPL limits (note: I have not included an adjustment for room gain, so the
"modified response" plot is the same as the theoretical plot without room gain):
I initially thought that "upgrading" my subwoofer would be a
simple issue of matter of removing the INF10 and inserting the SV10 in its place.
After all, they're both 10" drivers, right? Wrong! While they are both rated as
10" drivers, the SV10 requires a larger mounting hole than that of the INF10. Not too
much of a problem - I simply made a mounting template for the SV10, marked out the
required hole diameter on the box and enlarged the hole accordingly using my jigsaw.
A router would've probably produced better results, but I don't have access to one at the
Shown below is a picture of the box with the SV10 installed. Constructing a
proper protective grill for the front of the speaker has always been on my "To
Do" list, but I've never gotten around to it :-).
The theoretical response of the INF10 and the SV10 in this alignment is fairly
close down to about 40 Hz. However a simple before/after listening test suggests to me
that the SV10 produces a more "solid" sound than that of the INF10. And
it's power handling at higher SPL levels is certainly better than that of the INF10 - the
SV10 is apparently able to handle the peak output from my subwoofer amplifier, all the way
down to the alignment's Fb. At lower frequencies, the SV10 exhibited greatly
increased excursion (a characteristic of all vented systems), but did not exhibit any of
the harsh cracking noises that characterized the INF10's response to such frequencies at
those levels. Great!
Overall I'm very satisfied with the upgrade, which leaves one question..
What to do with the INF10 driver?
As mentioned previously, the INF10 will produce loud cracking noises if
driven beyond its limits, but sounds quite clean up to that point. Evidently what is
required is an alignment that ensures that the potential for over-excursion is reduced.
This suggests a small sealed box will probably work best. Or perhaps a 4th order
bandpass box tuned for higher SPL. In fact, that's exactly what I
tried - you can read about that project at the following link: