Fig
8 - ZA14 Response with Passive Crossover (Blue trace)
The Blue trace in Fig 8 is the acoustic response of the
ZA14 with a 3rd order network. The network has been adjusted
to follow closely the acoustic properties of the ZA14 Hybrid
Response (Red trace) shown in Fig 3. |
XT25SC90
with Passive Network
Fig
9 - XT25SC90 Response with Passive Crossover (Blue trace)
The
Blue trace in Fig 9 is the acoustic response of the XT25SC90
with a 3rd order network. The network has been adjusted
to follow closely the acoustic properties of the XT25 Response
(Red trace) shown in Fig 4.
|
Frequency Response of Swift-II with Passive Crossover
Fig
10 - Frequency Response of SWIFT-II with Passive Crossover ( 2.25kHz
| 18dB/oct)
Fig
10 above shows the summed response of the ZA14 and the XT25
with a full passive crossover. Acoustically, the ZA14 and
the XT25 cross at about 2.25kHz. There is a slight dip in
the response from 1.5kHz to 3.5kHz. I left this uncorrected
as our hearing is most sensitive in this region.
Fig
11 below are the plots of the Swift-II with the XT25 connected
In-Phase (Blue trace) and connected in Reversed Phase (Black
trace). The symmetry and depth of the notch at the crossover
point are indicative of proper acoustic summation.
|
In-Phase
and Reversed-Phase Responses
Fig
11 - SWIFT-II InPhase and Reversed Phase Summing
Swift-II Passive Network
Fig
12 - SWIFT-II Passive Network (18dB/oct)
The
crossover components are shown in Fig 12. Recommended types
are Polypropylene Capacitors, Air-Core Inductors (minimum
18 awg) and preferably Non-Inductive 10 Watts resistors.
To save cost, the 50uF can be a Non-Polar Electrolytic Capacitor.
Fig
13 is the impedance of the Swift-II. The lowest impedance
is about 3.5 ohms at 3.0kHz. This correlates to the Re of
the XT25SC90. The Swift-II should be matched with a power
amplifier rated for 4 ohms Nominal loads.
|
Swift-II
Passive Network Impedance
Fig 13 - SWIFT-II Impedance (18dB/oct)
Swift-II
Box Modelling
Fig 14 - SWIFT-II Simulated Box Tuning (13 Liters Bass Reflex)
The
Swift-II prototype box is 13 Liters Internal Volume, tuned
for Fb= 54Hz with a 2" Diameter PVC tube of Length
5". Fig 14 shows the simulated box tuning.
I
opted for a slightly larger box with a F3 of 47Hz. In the
event if the Swift-II is used without a Subwoofer, the lower
F3 will come in handy. |
Sound
of Swift-II
How
does the Swift-II sound like? If you're fortunate enough
to own the renowned AKG K240DF, the headphones that are
the mainstay in Recording Studios, Swift-II sounds remarkably
similar. It is neutral, transparent and revealing. Excellent
for Nearfield Monitoring use.
|
