Hi guys, thanks for allowing me to answer questions about SVS when appropriate, much appreciated. From now on I won't link any information---I'll just post it here. (sorry about that Ian).
Here is a little feedback from me regarding some of the questions I've received on the "b4" to date.
Really it's nothing but a Blown BBC(Big block chevy) in a world busy putting a chrome air cleaner on their 4 cylinder. Just a big ported enclosure.
Could it be considered *under ported*? Absolutely, there are always design compromises that must be considered.The question here should be...at what output level will the ports begin to *audibly* compress and how will that relate to what the rest of the room will be doing at those levels?(walls and floor flex for example ) I'm not sure how it will look on *sims*---I've been experimenting with this design for over a year now and can't remember running a simulation on it yet. We've just been so damn busy actually building and rebuilding about 6-8 variations on this and then spending hours and hours measuring each---how *old school* of us
I think our Ultra design has been verified to offer good output? (see the independent objective data gathered by John Johnson and Brian Weatherhead for details).In ground plane testing using a 1500w amp(Crown K1 bridged) here is how the B4 compared to a single Ultra/500w.(running max output tests at each 1/3 octave using a 10% thd limit)
FYI ~We use Soundtechnology V4.32 with an assortment of LinearX and AudioControl mics for testing. We have 1/96th octave resolution and calibrated mics capable of 176dB readings.
Ultra set to 20hz/B4 with all ports open
20-80hz avg ~ B4 was +9.9dB
25-63hz avg ~ B4 was +10.4dB
Ultra set to 20hz/B4 with two ports blocked
20-80hz avg ~ B4 was +10.4dB
25-63hz avg ~ B4 was +9.6dB
Ultra set to 16hz/B4 with two ports blocked
16hz B4 + 6.4dB
20hz B4 + 8.0dB
Please note---most of the B4 output readings were limited by the amp. While the Ultra would max out at 10% thd at just about every frequency before the amp(half a S1000 gave out)...the B4 would routinely show <10% thd at the output levels listed above until the amp clipped. Since then SVS has purchased a 5 kilowatt Crown Macro reference amp to find the 10% limits of the B4 at every frequency/tuning configuration. I don't have that notebook in front of me(so I can't reference the exact data numbers)...but we only saw a 1-3dB increase in output levels before 10% thd was reached in just about every instance. Given that, I would recommend anything from 600-3000w is fine with this...and 1500-2500 is what I would call optimal.I've been running one of these in my HT room for a couple of weeks now with a K1 bridged and I think that is fine. Going from the 1500w K1 to the 2500w k2 would give you another dB or so of clean output...but I doubt that would be needed(or audible) unless the room is very large.
I also took 1,2,5 and 10% THD checks on the B4 at each frequency/tuning configuration. I'm note going to sit here and type out what amounts to a notebook full of info...but here is one example.
ULTRA(with 500w) with all ports open/40hz
B4(with 1500w)with all ports open/40hz
The B4 had 8.7dB more output at 1% thd than the Ultra had at 10% thd.
The frequency response is very good with all four ports open but begins to push the +/-3dB window with one port blocked. In MOST rooms, this unit will remain relatively flat with 2 ports blocked. I do recommend using a good parametric EQ with this unit though. This is so powerful, adding something like the PE17 is a natural progression imo.(like adding headers to a 454 chevy)...you are just able to maximize everything a little better. With the EQ, you can tame room induce peaks with a couple of channels AND use the other channels to really dial in the subwoofer for each tuning point---then use the adjustable subsonic filter to tweak everything and you are all set to enjoy a little bit of bass.
Tom V.
SVS