charlie...
1. if you set the speakers to small, where does the 950's x-over choke them?

2. what is the advantage to using the 950's x-over and not the sub's?

am just curious to know...the subject interests me, and you seem to be on top of it.

harp795,

You can do everything you are currently doing with the 950, except when using the 5.1 inputs.

Telling the 950 set "no sub" and mains to "large", all the bass will go through the mains, which you can then crossover using the speakers levels signals at the sub. That is what I plan to do with my Vandersteen sub, which effectively makes my mains completely full range.

For the 2 channel analog bypass, you get full range through the 950, with double bass on the .1 output. Since you have nothing attached to the .1 output - no double bass. Easy.

Finally though, is you use 5.1 inputs from a SACD or DVD-A player, you would lose any information on the .1 input. Hooking a sub to the .1 output, and you get double bass since the low bass goes to the sub and the mains. The only way around this, I think, is to use an ICBM (or some other bass management in the player) to fold the bass from the .1 channel into the mains. That way you don't lose it, and with no sub attached to the .1 output, no double bass.

So I don't see any advantage to using the .1 output on any reciever or pre/pro as long as you are happy with the results you are getting using the speaker level crossover in your sub.

I guess double bass can be addressed also by always using the .1 channel and always running the mains full range. Then the sub and bass levels can be tweaked to sound balanced and consistent for all sources. The disadvantage is extra distortion due to driving the mains full range when they don't really want to play the lowest notes. Plus this requires a more powerful amp since the mains will suck much more power playing over their entire bandpass vs. being rolled off around 80 Hz.

It's been a while since I read the 950 manual, but IIRC it has adjustable xovers from 40Hz up to ????. 40 hz seems to be a logical choice for speakers that extend to 30 Hz, esp. if the SPL they can produce at that level is limited.

I like the concept of using the xovers in the processor 'cause I can twiddle easier and it also takes care of matching the low and high pass sections auto-magically.

Actually, supposedly it is recommended that for the best flat response and mix of speakers and sub, you should choose a crossover at approx twice your spec'd low freq response of your speakers. For me, my speakers are spec'd at 24Hz but I've found that my ideal crossover is around 40 Hz. As you mentioned, if your amplification is not stout enough to drive those 10" drivers in your speakers to low Hzs and high SPLs, then you may be better with an even higher crossover if your subwoofer is driven more stoutly.

I love the 950s triple crossover for movie viewing... my 950 yearning is for a straight wire 5.1 and 2.0 analog bypass without any bass processing at all if switched off. Ideally, that's what the 950 (and 1066) should do.

And the amp isn't everything - many (most) 'bass' drivers cannot actually generate high SPL at low frequencies without exceeding their limit of linear excursion - result - lots of distortion.

Charlie: yup... and when you consider that that single, for most folks, amp feed drives up to 4 drivers in each speaker... it isn't hard to imagine that an independent subwoofer will do sub-bass better...

My mains have six independent drivers each... Yeah, having a sub helps.

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Matthew J. Hill
matt@idsi.net

Yes. The rule of thumb I heard is the crossover should be at least twice the -3db point of the low frequency range. The -3db point may sometimes be more stringent than the low frequency range. Some speaker makes say the low frequency range is the -6db, -10db or even -15db point.

As a rule of thumb distrust all rules of thumb.

Moving the xover up an octave will attempt to do the xover in a range where the first part of the slope can be controlled better, but if you use the correct slopes and points this is not really beneficial.

OTOH the volume of bass available may make you want to cross over even higher - every case will be different.

I always thought that the reason why you wanted to be (at least) one octave up from the - 3 dB point, was that if that point is too close to the slope itself the crossover provides (where the mains are still audible), that you can get the effect of cascading filters.

For example, let's say you pick the -3 dB point as the crossover point. Well, the crossover drops that another 3 dB so you start off -6 dB in the hole already with the mains compared to the sub at - 3 dB (increasing).

I suppose the *steeper* the crossover slope for the mains, the less danger there is in putting the crossover freq closer to the mains - 3 dB point.