Axiom Home Page Forums General Discussion Home Theater Stupid Sub Question

Hello all! Well last year at Christmas I bought my first set of REAL speakers...M60's. Now this Christmas I just bought my first REAL sub...SVS PB10-ISD. I had actually been on the waiting list for an STF-2 but was just informed by someone on this forum that a PB10 was available in B-Stock from SVS.

Anyway, the STF-2 had the ability to set the cross over on the sub, however, from looking at pictures of the PB10 it does not appear to have a cross over setting on the sub.

I have a Sony DTS reciever which has a sub out but it doesn't have the ability to change cross over (not even sure what the default is). I haven't recieved the sub yet so I haven't been able to play around.
Should I just set my M60's to small, connect my sub, make sure the sub is turned on in my receiver and just assume the signal is cross over at whatever the default of my reciever?

That would work. But, if I'm not mistaken most Sony's with a fixed crossover are fixed at 120hz. Your M60's can play well below that. I would probably try setting the 60's to large and play the sub as well. I think on the Sony's you would use the "AFD auto" button.

My advice would be, when finances allow to upgrade the reciever with an adjustable crossover down to at least 60hz or get an Outlaw ICBM.

Yep...sounds like it's time for a new receiver.

Haha. Hey thanks for the replies. Yeah, I figured a new reciever is probably my next upgrade...maybe next Christmas!! Thanks

RD, some of the older Sony receivers have a fixed 100Hz or 120Hz crossover, which is higher then usually suggested. However, in my view your best option is as you say to simply set all speakers small and use that crossover. If the PB10 is roughly the same direction from you as the M60s localization shouldn't be much of a problem. A new receiver would be nice.

Ok, I have one vote to leave speakers set to large and one to set mains to small. I guess I'll have to wait for it to arrive so I can listen.

Can someone explain the large/small main speaker concept? If I leave speakers set to large, will the bass be equally sent to the sub and main speakers or will less be sent to the sub and more to the mains? If I set mains to small and my reciever has a built in crossover at 100Hz or 120Hz everything below the cross over will be sent to my sub right? Do you thing a quality sub...HSU, SVS, Axiom etc...will sound good even with such a high cross over?

You know...honestly this can be confusing. The de facto standard is to set them to small if you have a subwoofer. Period. What happens with some receivers though is the crossovers work differently. For instance, my friend's Denon 3803 did crossover differently than my H/K 630 did.

For him small or large much of the information still was sent to the subwoofer. So he could have large, but information was being sent as if it was set to small. Where as the H/K was different. If you didn't cross it over, the sub never got the signal. This could be due, in part, to the H/K's more robust crossover capability where it can break up small/large and crossover number settings for fronts/surrounds/center.

In either case though I'd recommend small. Unless your subwoofer is sub-par and your speakers would do a better job...the sub is meant to take those low signal Hz ranges...and the benefit is your amp has less strain on it, and there's more ampage for the rest of the spectrum to shine.

It's a win-win in my mind.

I agree with Misfit. In most cases, it's a good idea to set all your speakers to small if you have a good sub. A case where that might not be a good idea is if you prefer the way your speakers handle bass in the sub 80Hz range over the way your sub handles it. Depending on your room configuration and your sub's location, bass could simply sound more natural and better integrated into the soundstage when your mains handle all they are able to.

Really, we can keep talking at you forever, but the final judge for the best setting is you. Try both and see which one you like best.

I like the part of Peter's answer about deciding with your own ears.

My perspective (which probably does not help at all with the crossover-less PB10) is a little different. I have M60's and a PB12-ISD. I found that I very much prefer the way the M60's handle the 40-80Hz range; the soundstage is better, the response is smoother and the lower range is not localized to the sub. So, like a few others here, I run the M60's full range. I also have the crossover on the sub set down way low, so that it ONLY handles about 40Hz and lower.

I understand that I am underutilizing the sub amp and robbing myself of some headroom on the mains, but that's what works for me, in my room, right now.

RD, the large/small decision isn't based on the physical size of the speakers involved and to a large extent it shouldn't even be determined by the ability of the speakers to reproduce the lowest bass frequencies. The idea is that a good sub should do a better job with the lowest frequencies than even a speaker(such as the M60)which has good bass. If it doesn't, the sub hasn't been set up correctly or simply isn't good enough compared to the mains.

The receiver doesn't send "everything" below the crossover point to the sub, but rolls off the response of the mains below the crossover point(nominally at 12dB/octave)and rolls off the sub(24dB/octave)above the crossover point. Tests by THX and others indicate that the best compromise crossover frequency is around 80Hz, being high enough to take a significant part of the load off of the mains and their amps(a form of true biamplification)and not so high as to easily localize the sub. However slightly higher crossovers at 100-120Hz are usable if the sub has good response there and localization shouldn't be a problem if the sub isn't located in a different direction from a main speaker. Note that the response curve on your PB-10 shows smooth and flat response up to about 200Hz, so that factor shouldn't be a concern. Set your M60s small, don't worry about the crossover much, and enjoy the music.

Thanks all for your replies. This is a great forum and I always end up learning an aweful lot just by reading through all the posts...can't say I understand them all but I learn what I can!

I'll put up a post once my sub is delivered and I have a chance to play around with it. Right now I"m trying to figure out what I"m going to listen to first in order to test it out. Matrix I or II? Led Zep DVD? Roger Waters In the Flesh? Some good bass heavy TOOL? Maybe I'll just take a day off of work and listen to them all at once!