Setting Sub Crossover Freq

I have speakers that have rated sensitivity of 89-90dB
and a frequency range of 45-22000/50000Hz.

Anyone have any suggestions where to set a sub crossover frequency given these specs ?
Depends on their in-room response and their placement.

I like a slight overlap of 10-15 hz. any where from 55-60 seems like a good starting point for the frequency of your speakers. Placement of the sub and of the speakers is critical. If your sub is in the corner then you'll have more bass but not the best bass. If the sub sounds boomy then pull it away from the corner. Also, and this is personal taste, find a song that you're familiar with on the bass and turn the sub volume down until it's not enough and then start turning it up until the bass notes are to your liking. I like my bass to be an enhancment to the mains instead of thundering and overpowering. But thats just me. Hope this helps. Zmanastronomy
Thanks very much. I see that if you roll the freq back, you sort of need to roll the volume up...
Not neccesarily. What happens is that the frequency changes to a lower and less used freq. Once the music hits the lower freq it will still have the same volume just a lower freq responce. Play around with it and you'll get it just to your liking. It takes time, several weeks or more to tune a system in. Aiming the mains is very critical for stage and imaging. Tweek and listen for a while and tweek somemore and when you get something you don't like just go back to were you had it before.
If you get and use a copy of RoomEQ Wizard so that you can measure what the speaker(s) are actually doing in the room, setting crossover frequency, slope and levels is pretty easy. It may also give you an insight into better positioning of the speakers/subs.

Doing it by ear is hit-or-miss unless you have a lot of experience in this endeavor.

80 hz..............
80Hz. The universal solvent. ;-)
80HZ, I like this...this is the Ron Popeil solution: set it and forget it.
Potential for lots of overlap, bloat, & slurring with crossover up that high. For comparison try 40hz at both 12db/octave and steeper 24db/octave roll-offs. This may clarify the critical mid-bass and shift the transition between bass drivers into less audible LF region. Less can be more...
I agree, you have to set the crossover point LOWER than the bottom of your regular speaker. Then adjust the integration using the sub's volume control. Don't forget to check the phase of the sub also.

I agree that a sub sounds better out of a corner for music. Corners make for bigger THUMPS, which may be fine for home theater but loses character and texture on music.

If you can hear the sub then it is probably too loud. The integration should be seamless and not noticeable, else it's not set right.
>03-11-10: Ptmconsulting
I agree, you have to set the crossover point LOWER than the bottom of your regular speaker. Then adjust the integration using the sub's volume control. Don't forget to check the phase of the sub also.

I disagree. You have to set the cross-over point high enough that

1) You don't run out of linear excursion on the main speakers. For a non-ported speaker you get 12dB of head room (you can handle 16X more power) with each higher octave. 5-6" drivers in two ways often need 100Hz+ cross-overs to get good performance at reasonable output levels. Obviously this often calls for fourth order slopes and perhaps stereo sub-woofers.

2) You want cross-over points to work around the first SBIR null from the main speaker (where it's 1/4 wave length from the front wall thus causing a null; for instance at 4' you'll get the first null around 70Hz) and room modes stimulated by main speakers and sub-woofers (for instance you might want a 60Hz low-pass on the sub-woofer and 80Hz high-pass on the main speakers to work around resonances in the 70Hz range).

Achieving good integration is a separate issue which may call for options not available in most consumer gear like asymmetric cross-over points. With subs close to main speakers you may benefit from being able to replace the speaker's inherent high-pass function with a different one using a biquad with digital or analog (Linkwitz Transform) realization.
I found going a little lower than the output of my speakers with a little more volume to be much better than the other way around. Mine works best (seamless) out into the room and not in the corner.
For more thoughts, look at

FWIW, there is anecdotal evidence that some receivers still cut off the LFE at the crossover frequency.
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Thanks all for your input. I the case of polarity...I'm having trouble. Is there a precice way to know, other than by lisening for "more bass" ?
Mjmch, are you running through a high-pass crossover to main speakers and a low-pass crossover to sub, or are you instead letting the main speakers run full range and connecting the sub via line-level or speaker-level inputs from preamp or amp? These are two very different approaches. If taking the latter approach, you are only adjusting HF roll-off of sub, and would therefore want to do so at a frequency at or beneath the useful bass output of your mains.
Dgaarretson, I am running RCA outs from my pre into the RCA inputs on the Sub. (I'm running balanced from the other pre outs to my amp, which is then powering my speakers--full range).
This is an excellent way to go unless one has a high-quality full-function outboard crossover to perform high-pass hand-off to main speakers. Mediocre electronics of high-pass crossovers typically found inside sub cabinet are likely to degrade sound and cause more problems than are solved. You might first try the low 40hz point with a sharp 24db/octave roll-off. After you have experienced how clean things sound up into the mid-bass and mid-range, experiment with more gradual roll-off and higher crossover points for comparison. I bet you will find roll-off at higher frequencies is muddy.
Thank you !!
As far as polarity goes it's 0 or 180 according to the room. Have someone switch the polarity while you listen to a song with constant bass and choose the polarity based on which one has the most sound pressure. The loudest pressure is the correct phase.
I have set it to about 50-55 on the low end, althoug it's tought to tell with the rotary dial and now the volume is at about 2 o'clock. Seems to been pretty decent. i get some nice low end extention, where the speaks drop off.

Worth nothing, the speakers are ACOUSTIC SUSPENSION (no ports)
My brother (not on a'gon) opined:

"Who knew the level of dorkdom in the world? U do need to turn the power up with lower frequency settings. Reason being, wider, slower waves need more watts to reach the same amplitude of percieved loudness. 80 hz is a little muddy to my ears for a sub. I'd try around 65 hz. Keep in mind that the frequencies are actually notes, so you may want to tweak it based on what key the music you are listening to is in. To figure out notes, keep in mind 110 is an "a" and use pythagorean fractions to tune down to the key you are in. 55 is also "a" ...."

If you take only ONE THING from this thread, make sure it's point #2 from Drew.

I should clarify a bit. IMHO, the greatest benefit you'll get from a(n) (optimally installed) sub occurs ABOVE 70hz. This benefit is the ability to address the quarter wave null and the "hump" that so often occurs about half an octave to a full octave above that.

That's why I highlighted Drew's observation. His crossover scheme in point #2 may work well for the 1/4 wave null, but there is another approach to the issue, too. You may find it easier to sharply low cut your main speakers and cross to your sub above the 1/4 wave frequency. You can then address the problem effectively by optimizing the sub's placement in the room.

Stereo subs crossed even higher (app. 120hz to 140 hz) will allow you to address the "thickness" that often occurs in this range. BTW, "bassbusters" or other hemholtz devices can also be used to deal with this issue. If you don't want to go that route, IME, you can usually place stereo subs such that imaging is unaffected despite the high x-over point and frequency response will much, much smoother through the most troublesome ranges.

Good Luck

I second the use of REQ Wizard. My Maggies are rated to about 45HZ, but the in room response according to the room EQ wizard is 65hz. I was running my sub crossed over at 45 and I felt like I had a gap in the low end, this is was prior to running the REQ Wizard and want prompted me to run in in the first place. I bumped my crossover up to 65HZ and all is good now. The optimal setting would be 80hz but the sub was a bit too localized at that setting, this may or may not be an issue with your set up, it just depends on the placement of the sub in your room.
Does the software require much in the way of miking, etc ?
One mic, preferably but not necessarily, calibrated.