Subwoofer doubts: crossover setting for 60hz speakers


Hello there. I’m about to add a subwoofer through “high level” inputs to my stereo system, and I have some doubts. Nominally my speakers (Cabasse Riva) go down to 60hz. According to the stricter books, this means I should set the sub’s crossover to 120hz. Which would be a problem, since -from what I read- sound becomes “localizable” over 80hz, and my only spot to place the sub is a corner of the room. I guess that would severely affect soundstage, which is a deal-breaker for me. 

So my questions: 

1) Would it be ok if I set the sub’s crossover to 80hz? or would I be risking to create some kind of “gap” between sub and speakers? Do rememeber that I’ll hook the sub through “high level” inputs, so there'll be an increasing overlapping of frequencies above 60hz. 

2) Or would I be better off adding 2 subs instead of just one and setting them at, say, 100hz? Many audiophiles on the web advocate for double subs... 

Keep in mind here that my current options are: 1 excellent Velodyne spl1200r (that reaches 20hz), or 2 fairly good Focal sw700w (that reach only 40hz). If the answer to question 1 is "yes" -ie. if I may set the sub's crossover to 80hz without noticeable gap and preserving soundstage- I'll definitely go with the Velodyne.  

Thanks for ANY help -I need to move fast!


fedocable
Two subwoofers are a very good idea. Corner placement can be problematic, but can work. Trial and error in most cases, is how matching your mains to a sub(s), unless some automatic DSP is in the loop.

I can't really advise you as to which sub to buy, the one Velodyne, or the two Focal, but there is no hard fast rule as to what setting you use, just what sounds the best, and combines the sub/stereo speakers in the most seamless fashion.
Thanks for the reply. The problem here is that I cannot test the subs in my system before buying. And worse than that: I have absolutely no experience with subs. So, before taking the blind leap, I'm hoping to figure something out from the forum's audioholics. 
One other thing I should add is that I'm using a low power single ended tube amp -Unison Research's Simply Italy. Beautiful sound but, of course, not very strong on the bass.

Hi fedocable,  I don't know anything about stricter books, but I've set a bunch of subs over the years. Bass does become directional between 80 and 100hz.  There is no absolute answer to your questions. Room nodes and woofer placement cause or correct most problems with bass. I've never heard of a normal procedure of placing a sub an octave above the rolloff of the main woofer. 

As for a single or double woofer?  Double woofers are harder to place and if a single woofer is done correctly, a double woofer won't help much, but if you are trying to achieve the ultimate, a second woofer takes you the rest of the way there. 

I would start with a single woofer, I'd cross it around 100hz, placing it away from the corners, between speakers would be good, get your gain as close as possible for a smooth transition. You will get very close to getting the woofer right or you will find a bass peak somewhere that won't go away. Either way, once your gains are good,  I'd then take the crossover down to 60hz and see how the blend is. Depending on the room, you could still be dealing with a bass peak and may need to cross even lower.  My guess is that it will be decent. Start dialing in frequency and phasing until you are a happy camper. If there are bass peaks that won't go away no matter what, see if you have a phase dial and start working on phase, if you still have peaks,  you'll need some sort of bass traps in the room to absorb unwanted nodes.  I hope this helps,  Tim

Thanks a lot, Tim. Extremely informative, just the kind of feedback I was hoping to get. I'll go with the Velodyne, no more doubts.
IMHO, the main reason so many people have issues integrating subs into their system is that they try to cross them over WAY too high. If your -3dB point of your speakers is 60 Hz, I'd begin experimenting with a sub crossover point of 0.7 x 60 Hz = 42 Hz. Unless you are using a Vandersteen sub, you want the sub to just come up underneath your monitors...and usually not all the way up to the -3dB point of your speakers. 
All the more reassuring. Thanks!
IMHO, the main reason so many people have issues integrating subs into their system is that they try to cross them over WAY too high. If your -3dB point of your speakers is 60 Hz, I'd begin experimenting with a sub crossover point of 0.7 x 60 Hz = 42 Hz. Unless you are using a Vandersteen sub, you want the sub to just come up underneath your monitors...and usually not all the way up to the -3dB point of your speakers.
nrenter has it right if you are looking to add to what the main speakers can't physically reproduce. That's a good starting point and may need to increased. By setting the sub to 80hz you will add the lows your speakers can't do but also add to what they will do (huge hump in the 50 - 90 hz region). But if the sub is out of phase with the mains you'll end up with a suckout in that 50 - 90hz range. Phasing is very important because you don't want the added lows leading or lagging the lows from the main speakers. I have a Rel B3 which has a phasing switch - 0 or 180 degrees. So you may have to move the sub to get it correct. A couple of inches can make a pretty big difference.

That said my speakers are rated to 40hz and I set my sub to 32hz to get the best blend when I use the sub. I say when 'I use the sub' is because when I stream from the internet music the lows are already exaggerated.
Thanks a lot, xti16. I'm already free from the annoying idea of setting the crossover as high as 120hz. I'm convinced 80hz or even less will work fine. That means I'm going with the single subwoofer option.
As for it, I just found a third challenger, at a very nice price: a Phase Technology "Power FL-10"; comes with a 10' woofer plus a passive radiator. It goes down to 26hz, decent enough. The seller claims it's new. There are a couple reviews on the web, and they are all very flattering. And, best of all, the price is cheaper than retail in USA! -that is quite extraordinary here in Argentina.
So, new question: has anyone heard of it, or at least of Phase Technology? Thanks in advance!
Fedocable,

Every time I've added a sub, or subs to my system, I've had all sorts of challenges getting them to integrate properly.

My last struggle was integrating a pair of JL subs in a new, larger "man cave", where the room had all sorts of obnoxious resonances.

Using a sound pressure meter and a CD with sweeps I was able to improve things (helped me place bass traps in the room), but the system still didn't sound right.

Then I discovered a program to download, "REW" (Room EQ Wizard) and a " miniDSP UMIK-1 USB Measurement Calibrated Microphone" (thank you Amazon), and with those tools was able to get the crossover point, crossover amount and volume adjusted, and now the system sounds awesome.

You would need a PC (not sure if REW works on a Mac, bet it does, it's a Java app), and the microphone plugs into the standard USB port on the computer.
You would need a PC (not sure if REW works on a Mac, bet it does, it's a Java app), and the microphone plugs into the standard USB port on the computer.

REW works just fine on a Mac.  Absolutely fantastic tool for subwoofer integration.