Air temperature: 22 C (>30 C in the sun)
Atmospheric pressure: ~1035 hPa
Air humidity: ~40%
Wind speed: 1-2 m/s
I started planning this round approximately 3 months in advance, but soon after the registration was opened, it became very clear that we couldn’t measure all those subs in one day. The group was devided and now the test was a two day event, something I first dreaded, but now thanked. The final date was locked down around 1 month in advance, so after that I could only keep my thumbs up, because the spring weather in Finland can be a bit unpredictable. But luckily the weather held and the weekend couldn’t be any sunnier or warmer. The temperature was above 20 C on both days (in the shadow), in the sun probably way above 30 C.
Although this was the perfect weather for testers, not so perfect for the subwoofers itself. We recorded around 1-3 dB worse maximum output levels than during our previous rounds, which were held in a much cooler weather (especially the second one!). Of course it can not be generalized that all subwoofers will handle the changes in ambient temperature similarly, some may be almost immune to it while others suffer more (better VC cooling, different amp technologies etc.). Although the conditions were similar to all the subs tested now, it should be kept it mind that in a cooler weather one can expect 1-3 dB better max output levels (depending of sub).
The results were send to all the usual suspects (companies) (they are the only ones with such a huge interest) prior publishing. They were able to comment on them, but surprisingly very few of them did. Maybe they didn't find anything wrong in them?
We measured total of 22 subwoofers, 27 when counting two tuning options for some subs. I would have hoped more DIY subs, especially big ones, but unfortunately a guy with a Soundsplinter RL-p 15” and another with Adire Audio Tumult 15” ”chickened out” only a few days before the event…maybe next time. I would also like to develop the peak output testing. Since most of the real signals (music/movies) are quite short in time, 30 second sine sweep may not be the best possible option for max (peak) output measurements. I already tried TrueRTA's Quick Sweep this time, but its results weren't something I would have hoped. Shorter test signal may also reduce the effects of changing ambient temperature. Also some specific subs (especially all Genelecs) didn't like the long sweep I used and protested by the use of heavy SPL limiting at lower frequencies at high levels. This isn't probably a problem with shorter test signal or with real signals (music/movies).
SVS PB10-ISD was used as a reference subwoofer to ensure that the frequency response of the system nor the absolute SPL didn’t change between days. Here is the relative difference between the frequency responses measured each day. +/- 0.3 dB can be considered identical when noticing normal variations in background noise etc.
I will comment on each sub's results as soon as I have gathered my thoughts a bit. I will also update the results from the two previous rounds to match with these new ones and post them at here soon.
Thank you to all the guys who brought their subwoofers to the measurement session, I couldn’t do this without you. BIG thank you to Genelec, Marek Sound and MR Hifi for lending their subwoofers. Also thank you to people who helped me during measurements, and special thanks to Maukka for those excellent pictures. The next session is already in the planning stage.
Links to subwoofers tested on this round:
Audio Pro Sub Focus
Axiom Audio EP-600 (2nd test)
Chorus Vertigo XLS
DIY Chorus XP3 clone
DIY Diamond Audio 12”
DIY Infinity Kappa Perfect 12”
DIY Infinity Kappa Perfect w/ EQ and XO
DIY PA horn (XLS 12”)
Heco Celan Sub 38 A
HSU VTF-3 MK2 (maximum output)
HSU VTF-3 MK2 (maximum extension)
Magnat Betasub 38 A
Proson Stratego Sub 12+
REL Storm 5
SVS 25-31PC+ 25 Hz tune (dB12.2)
SVS 25-31PC+ 20 Hz tune (dB12.2)
SVS PB10-ISD (2nd unit)
SVS PB12-Plus/2 25 Hz tune (dB12.1)
SVS PB12-Plus/2 20 Hz tune (dB12.1)
SVS PB12-Plus/2 25 Hz tune (Plus 12.3)
SVS PB12-Plus/2 20 Hz tune (Plus 12.3)
No material may be reproduced in part or in altered form without permission. Copyright © 2006 Ilkka Rissanen and Mauri Eronen (pictures)