Maximum Clean Output from Subs

[mojave]

There is a thread at AVSForum about dual MFW-15's vs a VTF-3.3/MBM-12 combo. Since I upgraded from a VTF-2.3/MBM-12 combo to dual MFW-15's I decided to participate in the thread. I referenced Craig's output measurements from his subwoofer review thread. Pete from Hsu responded with the following:

I don't agree with that assessment on the VTF-3 MK3's output capabilities. Dual VTF-3 MK3's in the max output mode will have between 124-128db max "clean" output capability (using CEA 2010 tone bursts and stepped distortion limits) from 25-100Hz, and 118db max clean output capability @ 20Hz (measured @ 1m distance, outside).

Note that a single VTF-3 MK3 in max output mode has an average of 3db more distortion-limited output from 20-100Hz compared to the VTF-2 MK3. So dual VTF-3 MK3's would give up to 9db (!) higher output capability compared to a single VTF-2 MK3. To put that into perspective, it would take three VTF-2 MK3's to match the clean output capabilty of dual VTF-3 MK3.

Pete's numbers are at 1m vs 2m for Craig's tests. Ilkka also measured the VTF-3.3 (at 2m) with results posted at the HomeTheaterShack. How is Pete getting such high numbers? Can any changes they might have made to the VTF-3.3 really produce such a high output?

For disclosure, I own 4 Hsu subs and 3 av123 subs. I hope to compare the VTF-2.3/MBM-12 combo again against the dual MFW-15's (if I ever get the time).

[LoudandClear]

How is Pete getting such high numbers? Can any changes they might have made to the VTF-3.3 really produce such a high output?

You said it yourself. Measured at 1 meter vs 2 meters.

Also manufacturers usually tend to inflate specs where they can. Not saying this is the case here though. :no clue:

[Jethro]

It's a good 12" sub with some major output. Tough to compete with the big boys using 15" drivers however.

[SnowmaNick]

I could be wrong (and probably am) but when I read Pete's comments I figured he was referring to in-room response. Obviously the results would be significantly different than a ground-plane output test.

[JimP]

Does anyone know the conversion factor for going from 2 meters to 1 meter?

[Mike_TX]

Does anyone know the conversion factor for going from 2 meters to 1 meter?

I may be wrong (I would search...just off the top of my head) but I think 6 dB decrease vs 1m?
:scratchchin:

Mike

[craigsub]

Hi guys - When going from 2 meters to 1 meter, one would add 6 dB to the SPL in a Ground Plane setting, and adding a second subwoofer would also add 6 dB.

In order for Pete Hsu's claim to be true, a single VTF-3.3 would have to deliver 106 dB at 20 Hz at 2 meters groundplane.

That's a lot of output from a single 12 in a moderate sized cabinet, and definitely more output than we got here by about 4-5 dB.

It's still a great subwoofer, though. :huge: