selecting a crossover

The 950 offers different crossover frequencies for each speaker position. Should all speaker crossovers be set the same, or is it better to select a crossover which utilizes each channels ability to produce low frequencies. For example, with an Epic 80 system (which I own) do I set my Outlaw 950 to crossover bass to my SVS sub at the same frequency (100hz), or do I vary...setting the mains (M80ti) at 40hz, and the center (VP 150) and surrounds (QS-8) to 100 hz? Is there a magic frequency calculater (2X the -3db limit) that these frequencies should be set (which would be very high for the center and surrounds)? 80 hz seems to be too low for the center and surrounds, as they are well past their -3 db point before they get to 80 hz. On the other hand, 60 hz seems like I would be wasting 2/3 octave of available response from the M80s.

I previously had 5 identical speakers, so this question never came up. I always liked the idea of a triple crossover, but it seems that many people (who probably don't have the feature) say I should still set the towers at 80hz, even though they are only down 1db at 40 hz.

Help!?!?!


Bill Polley

[This message has been edited by willscary (edited September 27, 2003).]

Hi Bill,

I heard arguments about keeping your crossovers uniform, but I can’t recall the details now. I think you should play however.
There are rule of thumbs, and it seems to me, since I’ve starting trying to learn the subject the speaker response listed is often, to word it kindly, rather optimistic on many models as posted by their respective manuf in specs.

Because my life is hectic I’m a seventy percenter, I get about that far along the road (Knowing I should tweak for the extra 20 %) but run out of time to give it the attention it deserves. Cause sometimes ...it’s good enough when your life is crazy. I’ve had some good advice on setting crossovers here at Outlaw before, hopefully some familiar with the math of response and slopes etc, can be more specific to your brands.

I have had fun just systematically trying each setting with favorite and familiar passages in the past just to see what my ear likes best of the possible range of choices. Right now my systems out of whack needs calibrating and more.

But today I did the girl thing and shopped for something new to wear to the Meyerson. I’m very excited it’s unlike me to getting around to making plans to go do anything (I just always think I will). I read a blurb in last nights paper about Joshua Bell performing here, one portion of the performance to include John Corigliano's Red Violin Concerto (an expansion on the soundtrack from the movie “The Red Violin”) On Bell’s 290 yr. old Stradivari, one of the named violins the Gibson ex Hubermann

Bought tickets for tomorrow early this AM, I cant’ wait to hear this almost 300-yr. old violin …in person! It will prob. force me to tend to my business calibrating etc, when I come back home and pop in the soundtrack CD again


[This message has been edited by Smart Little Lena (edited September 27, 2003).]

Set them for each speaker's (set of speaker's) response. The arguements for a single crossover among all channels are weak. I can post more details if you like.

Do I set the M80 crossover at 40hz, the VP150 at 80hz, and the QS8 at 100hz?

Each of those speakers have responses that are close to flat at those points, and I like the idea of stereo bass from the mains (the triple crossover was a big reason for buying the 950, even though the speakers I had back then didn't utilize it).

I would think that the lower I can cross each one over, the less likely I am to have bass localization, and the better the overall imaging would be. MANY others have advised me that either ALL speakers should be crossed at either 80hz or 100hz (at the highest)or that speakers should be crossed well above their -3db point. I do not see the point in either of these views. Just looking for good reasons either way...most argue because "that's how they did it" and can't give supporting reasons.


Thanks Kevin


[This message has been edited by willscary (edited September 28, 2003).]

From Dr. Phil (Marchand), AKA 'the crossover Guru':

"The choice of the crossover point is a difficult one and often some trial and error is needed for achieving the best results.

With the 24dB/octave crossover a good rule of thumb is to set the crossover point at least 1/2 to 1 octave away from the cutoff frequency of the satellite.

Thus a satellite with a cutoff frequency of 40 Hz requires a crossover frequency of 60 to 80 Hz.

The subwoofer should then have a range exrending 1/2 to 1 octave above the crossover frequency. In this case, if 80 Hz was chosen, the subwoofer should have a range of at least 160 Hz."

The problem with bass management is that most have a 12 dB/octave high pass filter that is designed to affect sealed satellites which have a natural roll of of 12 dB/oct.

That combines to result in a 24 dB/octave slope which then matches the 24 dB/oct slope of the low pass filter that's applied to the subwoofer.

Most sats are vented (like your M80s) which have a natural 24 dB/oct roll off. With the 12 dB/octave filter applied, the result is a 36 dB/oct slope, which then doesn't match the 24 dB/oct slope of the sub. This results in less than unity gain at crossover, which causes a 'hole' in response.

This being the case, it is my own opinion that you should move the crossover point a bit closer to the sat's cutoff freq. when using vented mains (unless your pre/pro has the ability to change the LP slope, which the 950 does not).

In your specific case (M80), I would try a crossover of 60 Hz., as 40 is too low and there is no 50 Hz choice. Move up to 80 Hz, and compare the results to your ears.

With the center and surrounds, of course you should move the crossover up according to the F3 abilities of each speaker because 60 is too low for them.

Since there is no selectable 36 dB/octave slope for the LP filter, there is no solution to achieve unity gain at and around crossover.

Try 1/2 octave away from the F3 of your sats as a starting point, but realize that the higher points for center and surrounds will cause the sub to be more easily localized.

This, unfortunately, is the very short answer, but I hope it helps.

BoB is right on the money. No matter what the slope is (OK, I just ignore it anyway ), I cross mine over at similarly, anywhere from 1/2 to 1 full octave above the -3 dB point for each speaker. Same reasons: don't want the imposed slope of the 950's crossover "too close" to the natural roll off of the speaker.

Another interesting data point is that for a while, I had a very good, but very bass challenged center channel: the Vandersteen VCC Signature. (They limit the bass response on purpose to minimize the proximity effects to a TV screen.) I used a 120 Hz crossover, and while I never specifically listened for bass localization from the center channel to the sub, I never noticed it either.


[This message has been edited by Kevin C Brown (edited September 28, 2003).]

One more thing, another interesting data point. We all know that for best speaker performance, they should be some distance out from any wall.

I can do this easily for the 3 fronts, but 3 of the 4 surrounds and rears are within 6" of a wall. I do the trick of crossing them over at 100 Hz, (even though their -3 dB pt is 45 Hz), just to try to limit the "boxy" and "bloated" bass that's possible.

So I should crossover the M80's around 60hz and the center and subs at 120 hz?

What are the -3 dB points for each?

I believe the M80s -3db point is 34hz, the center is 85hz, and the surrounds are 95hz, according to the website. My house is all torn up and I have only TRIED the speakers in a small room to check them out, but I would say it is pretty close for the mains, but the center may go slightly deeper.

>> M80s -3db point is 34hz, the center is 85hz, and the surrounds are 95hz

Personally, I would start with 60 Hz for the mains, and 120 Hz for the center and the surrounds. But then move the values around for the center and surrounds to see if you can drop them at all. There are those freq sweeps on Avia, but to be honest, I always prefer real material that you're familiar with. I personally have used 120 Hz without any bass localization problems, but that is one thing to listen for. (Bass coming from the sub that should be coming from the center. The center will be easiest to tell, because of all the info sent there.) Let us know how it turns out!

I agree with this post. 60 and 120.