[randog]

I was reading through the Marchand xo user guide and it sez:

When the crossover frequency is below 100hz there usually is no stereo information present from the sound of the subwoofer, and a common subwoofer can be used.

Now, I know many of you who use subs for music prefer 2 subwoofers and I always assumed it was for stereo. Is it for stereo? Can you hear stereo? -OR- is it for better seamless placement? I.e: less directional?

If you set your main speakers to xo at 100hz, is that typically where your sub is xo's as well, or do you set in some overlap?

In the case of the Panasonic XR-45 which has only one sub-out, assuming you cannot place the sub between your mains, would it be better to split the mono signal between two subs or use one sub?

Thanks!
Randog

[randog]

Forgot another question as well...

What's the opinions of front-firing vs. downfiring?

[ooheadsoo]

In my experience, I can't really tell exactly which speaker bass under 70-100hz is coming from at low volume.  However, if you turn it up, sometimes you can sense the pressure coming from the direction of the subwoofer.  It doesn't help if you have the sub turned up for home theater, etc.  If you split the left and right signals and have the left sub only producing bass played on the right, and vice versa, it'll probably help your imaging in a slight subtle way, especially at higher volumes.

Technically, front and downfiring shouldn't matter too much except that downfiring subs have a slightly limited xmax depending on the strength of the surround and spider, and that downfiring woofers have their mass distributed evenly across the area, while front firing will have larger xmax but unevenly distributed mass due to the cone shape.  Supposedly even mass distribution will help limit distortion...Either type can sound good.  There's a forumla available somewhere (I think partsexpress has it on their page) that lets you determine if the strength of a woofer's surround and spider are strong enough to support down or upfiring woofers.

[Carlman]

To me getting the right 'feel' is important in a sub.  I think ooheadso's description is accurate.  

2 subs for stereo have a visceral impact that is important to me.  I have a small room and I only need 1 small sub to do what I need... however, it is front firing and directly between the speakers.  

The downfiring sub vibrated my hardwood floors a LOT.  Moving to front firing has helped the 'feel' of the bass seem more correct than downfiring in my room.  I think downfiring sounds the same as front firing but makes for a different impact.

I've never seen a downfiring sub that's shallower than the excursion of the sub.  Sounds like a product of poor planning.

I have found the most important aspects of picking a sub is how it will work with the monitors.  For instance, I have first order crossovers in my speakers and 4th order xover in my sub.  For some reason this makes it really hard to integrate.  I was told the reason by Roy Johnson but it was a bit over my head.  I'm still learning in the crossover department.

I did find the Von Schweiker VR1's to integrate quickly and perfectly.  They use 4th order crossovers, though.  There's merit to Roy's comments.

That's what I've learned so far.  Hope it helps.

[nathanm]

If you have only the single sub I would center it between monitors w\very low XO point (40-60Hz).  For my system I let the mains overlap the sub but it will depend on what kind of bass your main speakers put out on their own.  Personally I disagree with the omnidirectional bass idea.  You have to factor in the visual and psychological factor of the sub being off in the corner by itself; your mind is going to expect bass to emanate from there even if you may not necessarily be able to locate it blindfolded.  If you had two subs I could see using a higher XO point, otherwise I would keep it as low as possible.

I'd also agree with the comment about the pressure coming from the direction of the sub.  Definitely is a factor.

[ooheadsoo]

It's a matter of physics.  The same driver front firing will have a smaller xmax when it's hanging down because of gravity.  This happens to every driver.  Those used in downfiring subs are drivers that have a strong enough suspension that the loss in xmax is negligible.  

From what I understand, having matching slopes on sub and speakers is important for good FR matching.  You don't want one to fade and drop off the map while the other is still gently tapering away.  Typical subwoofer amps use a 2nd order slope, that I've seen at any rate.  This matches with the natural acoustic rolloff of a sealed cabinet, which is usually around 1st to 2nd order.  A ported speaker has a much sharper rolloff after the port frequency, so that matched your 4th order subwoofer crossover.  It's good to know what the sub's crossover slope is.

[randog]

Thanks. And welcome to AC ooheadsoo  

I have found the most important aspects of picking a sub is how it will work with the monitors. For instance, I have first order crossovers in my speakers and 4th order xover in my sub. For some reason this makes it really hard to integrate. I was told the reason by Roy Johnson but it was a bit over my head. I'm still learning in the crossover department..

Ooch. You lost me here. I had to look back to make sure I posted this in The Bonehea... er... The Starting Block. Is it too complicated to give me a rundown on X-order crossovers?

I didn't hear anyone mention stereo, so I'm assuming it is correct that you cannot discern stereo with two subs...

I'm beginning to believe the prudent thing to do is to start with one sub and move it around. My cabinet is square, so I can even play around with front vs downfiring. My floor is a carpeted slab which should work well either way, eh?

Randog

[ooheadsoo]

Thanks, randog!

"If you split the left and right signals and have the left sub only producing bass played on the right, and vice versa, it'll probably help your imaging in a slight subtle way, especially at higher volumes."  
-a reference to stereo subs.  2 subs = expensive though......

The order of the crossover refers to how many decibels the volume of the sound is down by 1 octave.  I've never seen it clearly explained (probably since I'm too cheap to buy any loudspeaker design books :p ) but the order just means multiples of 6db.  1st order is 6db down, 2nd order is 12db down, etc.  Phase issues aside (which I don't understand yet) it's important that the lowpass and highpass filters match slopes as well as possible, or you'll inevitably get areas where the two slopes don't sum up evenly.

I would leave your sub the way it was designed, if it's a front firing one.  Yours may not have a surround and spider strong enough to go downfiring, you never know until you check the parameters on the driver and run it through the equation.

[doug s.]

I didn't hear anyone mention stereo, so I'm assuming it is correct that you cannot discern stereo with two subs...

wrong.  listen to nusrat fateh ali khan/michael brooks "nightsong" cd.  on some cuts, you'll hear low-frequency stereo that moves all over the room.  

i have *always* been able to localize a single sub, even when crossed over wery low, unless it's centered *exactly* between the monitors.  and, soundstaging will suffer, unless crossed over at 40hz or lower, imo.  having two subs will *improve* soundstaging, imo..

for stereo, get two subs.  the room interaction will be better, due to two different sources of low frequencies, & at any given spl level, the distortion will be about half that of having one sub, for obvious reasons...

ymmv,

doug s.

[Psychicanimal]

wrong.  listen to nusrat fateh ali khan/michael brooks "nightsong" cd.  on some cuts, you'll hear low-frequency stereo that moves all over the room.  

i have *always* been able to localize a single sub, even when crossed over wery low, unless it's centered *exactly* between the monitors.  and, soundstaging will suffer, unless crossed over at 40hz or lower, imo.  having two subs will *improve* soundstaging, imo..

for stereo, get two subs.  the room interaction will be better, due to two different sourc ...

What Doug is telling you is absolutely correct.  I will add some more:

1) that the ear uses low level information for spatial clues--and a significant part of that is in the bass region.

2) just because you're using two subs does not mean that the x-over point can go up.  The person I bought my subs from also had a Marchand X9 like me and experimented with 70, 80 & 90 Hz modules, finding 80 to be the highest he could go w/out hearing midrange information (vocals) from the subs (slope is 24 dB/octave).

3) setups with one subwoofer can sound great, too.  A deceased friend of mine used ProAc Super Tablettes with a Janis 10" sub and matching Janis x-over/amp with great results.  He was using a Klyne preamp and a Conrad-Johnson tube amp.  Wonderful sound it was.

It seems to me that your receiver/integrated is not at the level where it can help you obtain a proper audio subwoofer setup--more like a HT kind of feature.  Getting proper bass is NOT cheap.  It's a decision that you will have to make.  We're talking extra sets of IC's (and good IC's are not cheap--I settled for Ridge Street Audio MSE Gen I's coming out of my x-over, as could not afford $700 for two more sets of Gen II's like in the rest of my system), two subs, another beefy amp (or monoblocks in my case), more audio grade power cords, filtration for the amp(s) & x-over, cones, footers, shelving, speaker wire.  It will take money to do it right.  Be warned.  It's better to stay away from the sub project unless you are willing and able to spend the money to do it right.

Now I reallize that with a multi format DVD transport, a Channel Islands passive, Jeff Rowland #1 amp and a pair of Madisound MTM speakers and RSA cables I could have assembled a killer system with much less expenses and complexities.  Better sounding than what I have?  No, but simpler and not too far away...

[randog]

I'm going 2.  

Thanks for the inputs.