Dual Subs Experience

Chris Huber · 02-08-2007, 07:30 AM

Hey guys, can you try and convey what adding a 2nd sub into a good system with a large 7,000 cu ft room would be?
I have a SVS PC+ right now, and the quality is very good. I know with a 2nd sub, levels go up 6 db, right? We'll other then that, how did it make your system feel?

Vader · 02-08-2007, 07:53 AM

Chris,

I started with a single 20-39 PC+ last spring, and found that it would cry uncle on "WotW" and "The Incredibles" during certain sequences. Working with Ron at SVS, I ended up going with dual cylinders. After which the sound was noticably smoother (presumably due to less THD), and neither sub even broke a sweat during the same sequences. My airspace is about half of yours (~3200 ft^3), and I tend to listen at about 10dB below RL (on average).

Chris Huber · 02-08-2007, 08:38 AM

Cool, thanks for the heads up... Whats THD btw? Did you co-locate? I am wondering if I can just hook the added sub to my 2nd channel on the BFD and copy the 1st channel settings to the 2nd...

anyone elses experience?

Arthur S · 02-08-2007, 09:29 AM

Quote:

Originally Posted by Chris Huber

Cool, thanks for the heads up... Whats THD btw? Did you co-locate? I am wondering if I can just hook the added sub to my 2nd channel on the BFD and copy the 1st channel settings to the 2nd...

anyone elses experience?

Hi Chris

THD mean Total Harmonic Distortion...to add 6 db you would need to place them basically side by side...otherwise you may end up with as little as 3db of increased bass...I have used 2 subs for a couple of years and I like them separated because you can get a sort of "wall of bass" effect if they are properly set up...your mileage may vary. please keep in touch.

Tobe · 02-08-2007, 10:00 AM

Chris

I agree with Arthur in the "wall of bass" effect. It's difficult to describe but when I added a second sub, there was a definite added dimension or smoothness. I also separated mine. When I co-located, even after making numerous adjustments, there was less "presence" and less "perceived" output. You know all rooms are different. Didn't even need to get out the meter. I find my wife is a much more useful tool than the meter sometimes.

Great thing about duals is multiple combinations to find the best sound. If you got the money go for it.

**HTF Ads**

SVS-Ron · 02-08-2007, 10:04 AM

Chris,

Others that actually know how to use a BFD correctly will have to help on that point, but the most critical aspect of dual sub setup is indeed that question about "co-location". If you set two subs side by side, you TEND to get (not always) better mutual "coupling" of the subs by virtue of the ability to keep them in perfect phase. Setting them (co-located) with phase dials in the same position will get you about right out of the box and make using the BFD much easier too (since they would be EQ'd as one).

If you do keep them side by side, and calibrate them the same (say, to 75dB same as your mains) and they are in perfect phase, you will get that perfect +6dB increase in gain, across the operating bandwidth of the sub (probably into the 15h-18hz range at least with nominal amount of room gain down low). If you separate your dual subs, then that's where the PC+'s variable phase becomes really helpful. Do each sub's calibration separately first (to 75dB, one sub on at a time), then switch them BOTH on. Chances are good if they are separated you won't see anything approaching +6dB (or 81dB) unless you tweak the phase while test noise is playing for the subs, even then the overall gain increase might not rise above 4-5dB, depending on your room's sonics. Best to have a helper do this phase adjustment in small steps, while you measure from your room's sweet spot. Keep in mind that if you get +6dB it's still an average response that's been optimized.

You might tweak your blended response with the BFD after that stage, but by all means (if you don't co-locate) spend a few minutes getting phase right before diving in to EQ.

In either case, depending on your use of a single sub, twins can be a startling change, or quite subtle. By the way we always recommend using like subs so differences in frequency response don't negatively affect your sound. If you are keeping to the clean operating limits of a single sub (not pushing it into "compression" where signal dynamics [peaks] are no longer accurately rendered), and not simply overdriving it and causing loads of distortion (less than 10% is generally considered ideal for bass frequencies) then adding a second sub won't help your sound.

But it's fairly rare in this day of massive swings in amplitude and depth from Hollywood blockbusters or even a lot of music now, that hard-driving enthusiasts looking to create a true theater or concert experience have enough depth and power to cleanly play back all the depth and dynamics one might require. Adding a second sub, IF you are prone to pushing your first sub to its limits can be a revelation however. Lower distortion, better extension (subs tend to limit first down low where the physical requirements of making bass are harder) and far better dynamics allow for both cleaner more natural sounding bass when you approach theater/concert levels are all part of the "deal" if you will.

So if you are already happy with the overall performance of your sub, and don't ever sense it's running out of steam so to speak, then a second sub is not a good investment. But if like many (if not most) "power users" in theater/music audio, have a large room (space eats bass) you'll marvel at the newfound bass that twin subs can yield.

Drop us a line if you have more questions about ordering a second sub (or at least mention that you did, so we can apply the usual small discount we give to returning customers).

Best regards from SVS,

Ron
SVS

Chris Huber · 02-08-2007, 10:50 AM

Right now with the setup, I know I can just drop a 2nd PC+ right behind the current one, for co-location. If I wanted the bass wall effect of separating subs, I'd have to put them right behind the couch on each side. My room has wierd shapes, so EQing 2 subs will be hell I'm affraid.

I am in search for more tactile feel down low and stress relief at higher vol, and I think an added PC+ in a 7000 cu ft basement might do this, right?

Thing is, I don't want my bass over-bearing up in mid/high range.

John Garcia · 02-08-2007, 06:09 PM

I've got two subs currently and I think you would be able to achieve what you're after without overpowering the rest of your system. Under normal conditions, it doesn't even sound too much different in the lower midbass, but when it comes to output, especially down low, it is very apparent to me. It is a lot of fun, but to be honest, I like the sound of just one or the other better. You being in a basement is a different proposition though, as that can definitely create issues with really "feeling" the bottom end. Just another thought, how about a single Ultra (the new one) or even something like a Plus/2?

Chris Huber · 02-09-2007, 09:19 AM

Quote:

Originally Posted by John Garcia

I've got two subs currently and I think you would be able to achieve what you're after without overpowering the rest of your system. Under normal conditions, it doesn't even sound too much different in the lower midbass, but when it comes to output, especially down low, it is very apparent to me. It is a lot of fun, but to be honest, I like the sound of just one or the other better. You being in a basement is a different proposition though, as that can definitely create issues with really "feeling" the bottom end. Just another thought, how about a single Ultra (the new one) or even something like a Plus/2?

Thanks for your input John. However, I can't justify selling my PC+ and getting a ultra when i can just add a 2nd PC+ for some great power... So you where saying that you actually like the sound of one sub better then 2?