3.3 Turbo not needed?

[bsoko]

I got this tread off of Iikka's HSU VTF-3 MK3 test. It was posted by a gentleman from Cairo, Egypt who says:

Re: HSU VTF-3 MK3 with Turbocharger
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.

If this is true, why is the Turbo being sold as an improvement?

Bill

[thsmith]

Bill, I suspect your question is for Pete. Here is a link with some test results on the HO Turbo. Not sure they apply to the 3 3 T but I would think so.

http://www.hometheaterhifi.com/volume_13_1/hsu-vtf-3-ho-subwoofer-3-2006-part-1.html

keys points from article cut and pasted.

The Turbo is not really necessary to have a good experience, but it adds a bit of whoomph below 20 Hz if there is any material there. Most likely, it would benefit from something like pipe organ music.


by the time you get to 30 Hz and higher frequencies, THD+N with the Turbo is the same as without it.



With no Turbo, the measured room response rolls off below 20 Hz.
http://www.hometheaterhifi.com/volume_13_1/images/hsu-vtf-3-ho-subwoofer-room-response-no-turbo.gif
But, with the Turbo, the room response is flat to about 12 Hz. This is superb. Remember though, you do pay a price in terms of THD+N for that extension at the low end. You have to decide what is best for you. As for myself, I would use the Turbo, since I really like that < 20 Hz stuff. http://www.hometheaterhifi.com/volume_13_1/images/hsu-vtf-3-ho-subwoofer-room-response-with-turbo.gif

[Pete_Hsu]

Bill, don't forget that in that test case, the VTF-3 MK3 was measured sideways with woofer facing the mic, in an orientation where the driver and port centroid were not equidistant from the mic. This ends up underestimating output near the port tuning, so naturally very little difference will be seen between port plug and turbo. In reality, with turbo the subwoofer can play significantly louder for a given level of port noise compared to the port plugged mode. Sure, in some cases the subwoofer will not be limited by the cross-sectional area, but with pipe organ music and some other material the turbo can make a noticeable difference at higher playback levels.

Sincerely,

[cacihome]

Bill, don't forget that in that test case, the VTF-3 MK3 was measured sideways with woofer facing the mic, in an orientation where the driver and port centroid were not equidistant from the mic. This ends up underestimating output near the port tuning, so naturally very little difference will be seen between port plug and turbo. In reality, with turbo the subwoofer can play significantly louder for a given level of port noise compared to the port plugged mode. Sure, in some cases the subwoofer will not be limited by the cross-sectional area, but with pipe organ music and some other material the turbo can make a noticeable difference at higher playback levels.

Sincerely,

For my experience with it, it is exactly what I found...On pipe organ material like programming is where you noticed the audible differences the most...But definately less port noise in any material played...YEP.

[lradden]

About a year ago I took some measurements of the VTF-3 HO with and without the turbo. At 16Hz the turbo made a 2 or 3 dB difference and from 15Hz and below it made about a 6 or 7 dB difference. To put that into perspective to play a sub 5dB louder you would need two subs stacked on top of each other to get the same increase. So the turbo is allowing the HO to play as loud as two HO's without a turbo in the low stuff. IMO the turbo is doing exactly what it was designed to do. It allows the HO to play louder at the tuning point.

Also there are a lot of legacy DD and DTS movies with bass in the 15Hz region during action scenes. For movies this kind of low bass performance is a great benefit and the new HD audio fortmats like DTS-HD MA, uncompressed PCM ,and TrueHD just increase the need for this kind of low bass performace even furthur.

http://pages.cthome.net/lradden/ht/VTF-3%20HO%20Comparisons_files/image008.gif