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Elite Shackster
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Discussion Starter #1
Manufacturer: HSU Research
Model: VTF-3 MK3 with Turbocharger
Provided by: Ilkka
Manufacturer link: HSU Research
Price: $799

Manufacturer specs:
• Amp Power (RMS): 350 Watts
• Bass Extension (max extension mode): 18 Hz
• Bass Extension (max output mode): 25 Hz
• Woofer Size: 12 Inches
• Crossover: Bypassable 24 dB/Oct, continuously variable 30 - 90 Hz low pass
• Ports: Dual flared 4 Inch
• Phase: 0/180°
• Inputs: speaker level (2), line level (2)
• Power Outlet Requirement: 430 W, 120/240V
• Ship Weight: 90 Lbs
• Dimensions: 21.5”(h) X 17”(w) X 25”(d)
• Warranty: 7-years on the subwoofer, 2-years on electronics

Configuration as tested:
Phase: 0 degrees
Tuning frequency: ~17.2 Hz (no port blocks, maximum extension mode)
Crossover: Bypassed
Orientation: Woofer facing the mic, ports facing left

 

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Honestly accroding to Ilkka's measuements, there is very minimal variation in output, compression and THD (if any at all) between the maximum extension mode and the turbocharger. Nevertheless, with turbo port resonnance at 120 Hz make me feel bad. This indicates the subwoofer is not limited by port area to begin with, thus making not beneficial the addition of turbocharger to inscrease an already good port area. Maybe the Turbo would work better for smaller area ports, but not this one.
Last point..... I trust Ilkka's measurements ;)
 

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Honestly accroding to Ilkka's measuements, there is very minimal variation in output, compression and THD (if any at all) between the maximum extension mode and the turbocharger. Nevertheless, with turbo port resonnance at 120 Hz make me feel bad. This indicates the subwoofer is not limited by port area to begin with, thus making not beneficial the addition of turbocharger to inscrease an already good port area. Maybe the Turbo would work better for smaller area ports, but not this one.
Last point..... I trust Ilkka's measurements ;)
:bigsmile::T
 

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Elite Shackster
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Discussion Starter #11
is it just me or does the max extension mode and these results look pretty much the same i.e max output and power compression? (meaning, there isn't really more output with the turbocharger)

edit: found ilkka's comments
http://www.hometheatershack.com/forums/subwoofer-tests/5747-subwoofer-tests-round-4-5-6th-may-2007-test-summary.html#post45289

but does that mean, it make no sense to get the turbocharger for the 3.3?
It's not just you. The turbocharger doesn't really add that much output because the output is limited by the amplifier and driver. A single 4" port is already large enough for the power and excursion available so that extra port doesn't give one that much additional output.

I also tried a subjective test where I played multiple movie scenes with both configurations (with and w/o the turbo using same tuning) at close to maximum output levels, and I couldn't tell much difference when it comes to output or port noises.
 
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