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Need help with subwoofer setting

Old 01-16-02, 06:19 AM
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Need help with subwoofer setting

On my Sony SA-WM40 subwoofer, there's a setting for "cut-off frequency," and it ranges from 50 Hz to 170 Hz. What should mine be set at? (My fronts and rears are PSB Alpha A/Vs, and my center channel is a PSB Center.) Right now it's just somewhere in the middle.
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Old 01-16-02, 09:54 AM
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It doesn't matter if you're using a line-level input from your receiver, i.e. the RCA cable from the "sub" output of your receiver. With the line method you're using your receiver to function as the crossover.

If you're using the less optimal method of "all speaker wires go to sub then out from sub to satellites" then you'll want to adjust the cutoff freq to the lowest frequency that your satellites can handle.

You can test how well this works using the low frequency sweep on a THX setup DVD.
 
Old 01-16-02, 10:29 AM
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Originally posted by Gomez
It doesn't matter if you're using a line-level input from your receiver, i.e. the RCA cable from the "sub" output of your receiver. With the line method you're using your receiver to function as the crossover.
True that he's using the crossover in his receiver, but are you sure that this method would bypass the crossover in the sub? In other words, if he set the sub's crossover to 170 Hz, wouldn't the sub be missing the signal from whatever his receiver's crossover is set to (say, 120 Hz) to 170 Hz?

Either way, you can't go wrong in this situation by setting the crossover as low as possible (50 Hz), so that the sub definitely gets all of the LFE from the receiver.
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Old 01-16-02, 10:41 AM
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So are you saying I should trust the LFE seettings from the amp?
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Old 01-16-02, 10:45 AM
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I see your point, but I think you have it backwards. If using line out from rcvr then rcvr sends freq lower than "x" to sub. If sub freq cutoff set to a number lower than "x" then sub might only play freq below where the freq cutoff is set.

However, the cutoff decides not how low it will play, but instead what the highest freq it will play.

"Either way, you can't go wrong in this situation by setting the crossover as low as possible (50 Hz), so that the sub definitely gets all of the LFE from the receiver." - I believe this is patently false...

If you did that and the receiver has an internal xover set at 100Hz then you would not hear anything from 50-100Hz. Bad. So, if the sub's freq cutoff is in fact active when using the line in (I doubt it but you never know), then you would want to make sure you set the sub's freq cutoff above or equal to where the rcvr's internal xover is set.

The idea behind using an xover in a sub is so that the sub does not have to produce frequencies higher than needed which will "muddy up" your sound. That said, you want your sub to xover as low as possible while ensuring that higher frequencies go to the satellites and also that the sats can handle what's being sent to them.

As a starting point, 80-100Hz is fairly standard. If this guys receiver is using a line out to the sub then it couldn't hurt to set the sub's freq cutoff to its highest setting, but it COULD cause a response gap by setting it to the lowest setting if the freq cutoff is active even when being signalled by a line in.

Again, freq cutoff and xover frequencies dictate the highest frequency that will be played by the sub.

Last edited by Gomez; 01-16-02 at 10:47 AM.
 
Old 01-16-02, 10:51 AM
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Oh yeah - my subwoofer (harman/kardon 10" 100w) disables the freq cutoff knob when being fed a line level input which is what I use.

If you're using line level then couldn't hurt to set freq cutoff to highest level, but might create response dip if set too low.
 
Old 01-16-02, 11:10 AM
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Glad I made my post in the form of a question.

While this subwoofer stuff isn't my strong suit, I definitely had a brain lapse when I recommended using the lowest cutoff setting on the sub instead of the highest.
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Old 01-16-02, 11:34 PM
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OK, so what's the consensus guys? Yes, I am running a line out from my receiver to my sub...and my other five speakers are connected directly to the receiver.
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Old 01-16-02, 11:42 PM
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Originally posted by criptik28
OK, so what's the consensus guys?
I agree with this:

Originally posted by Gomez
If you're using line level then couldn't hurt to set freq cutoff to highest level, but might create response dip if set too low.
Set it at 170 Hz.
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Old 01-16-02, 11:43 PM
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So what exactly does it mean if I set the cut-off frequency to its highest setting, 170 Hz? Does that mean all sounds below that frequency get sent to the sub?
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Old 01-16-02, 11:47 PM
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Originally posted by criptik28
So what exactly does it mean if I set the cut-off frequency to its highest setting, 170 Hz? Does that mean all sounds below that frequency get sent to the sub?
If you were sending a full-range signal to the sub, all sounds above 170 Hz would be cut off, and only sounds below 170 Hz would be played.

But, you're not sending a full range signal to the sub. You're sending a (estimated, and this varies by receiver) 120 Hz and below signal to the sub. Since everything you're sending to the sub is below the cutoff point you set on the sub, the sub will play the entire signal it is given by the receiver.
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Old 01-16-02, 11:51 PM
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Originally posted by stevevt


If you were sending a full-range signal to the sub, all sounds above 170 Hz would be cut off, and only sounds below 170 Hz would be played.

But, you're not sending a full range signal to the sub. You're sending a (estimated, and this varies by receiver) 120 Hz and below signal to the sub. Since everything you're sending to the sub is below the cutoff point you set on the sub, the sub will play the entire signal it is given by the receiver.
Ah, I see, got it.

One more question - I used a Radio Shack Analog-Display Sound-Level Meter to calibrate my speakers and sub. However, I heard that the sub output shouldn't be as loud as the other five speakers. Is this true? On my receiver settings, I think I currently have the fronts on +0, the center on +1, the rears on -1 and the sub on +8 or something crazy like that. How much softer should the sub be?
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Old 01-16-02, 11:56 PM
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Originally posted by criptik28

One more question - I used a Radio Shack Analog-Display Sound-Level Meter to calibrate my speakers and sub. However, I heard that the sub output shouldn't be as loud as the other five speakers. Is this true? On my receiver settings, I think I currently have the fronts on +0, the center on +1, the rears on -1 and the sub on +8 or something crazy like that. How much softer should the sub be?
You're going to have serious problems using that meter to calibrate your sub. From what I've read, they really aren't accurate for sub-type frequencies.

I'd suggest using the meter results as a starting point, and then using trial and error to set the sub to your liking.

Other than level and cutoff, placement is a huge issue with subwoofers (as you may or may not know already). Have you tried playing around with various placements? Do you have a lot of flexibility in that department?
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Old 01-17-02, 12:05 AM
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If your sub is +8 you may wish to look on the back of the sub for a knob to turn it up instead of your reciever's sub trim.

Ditto on the placement issue. Subs seem to have the most punch when placed in a corner, maybe 6-12" away from each wall. An alternate and improved method of placement is to put the sub where you usually sit to listen, then walk around the room and see where the bass sounds best. That spot is where your sub should go. Bass sound wave propagation is a complex animal but the "place the sub where you listen and walk around" method works well.

There's a lot of good information on speaker placement at the Dolby website under consumer products / surround systems as I remember. I'll bet dollars to doughnuts that over 90% of us have improperly placed our rear surround speakers...
 
Old 01-17-02, 01:15 AM
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Yeah, I've looked at that Dolby website, thanks.

I did try the whole "put-the-sub-in-your-listening-spot-and-walk-around-the-room" trick, and ended up putting the sub left of the left front speaker, about 3-4 feet away from the corner of the room. It faces the couch.

I thought that whole speaker calibration thing wasn't working very well when the sub had to be turned up REALLY high. I ended up just fiddling around with the level knob and the receiver setting anyway.

Thanks for all the help!
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Old 01-17-02, 10:28 AM
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Mine is pretty close into the corner and souynds great. Click the link in my signature to see pics.
 
Old 01-17-02, 07:07 PM
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I have my WM40 volume set at 1/3, and the receiver at -5 to get it set at +4 db above my reference (72db). I find this is pretty good for 5.1 and DTS encoded movies, but I have to bump the output up to 0 or +2 for music. I used the Ratshack meter to calibrate, but you will get ballpark only.

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Old 01-17-02, 07:30 PM
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So if I'm reading correctly (which I'm prolly not) u say that if your sub's plugged into your receiver via line that the xover on the sub don't really matter (unless it's less than what your receiver is set at). Why then does mine get louder and deeper when I turn it up on the sub (Sony SA-WM40) to 170hz?

And what should I set my receiver xover to? It has 80, 100, and 120. Then there's an LFE ATT. that can be set to 0 or 10db. I dunno what any of this stuff does! Also an "Input ATT" option that can be set to Normal or ATT ON.

And finally, I've heard about a lot of people modifying there Sony sub. Anyone ever do that and see good results. Like putting some stuff in it or sumtin.

Thanks in advance for helping the Home Audio Illiterate!
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