Can I Get The Definitive Answer about Crossover Settings? (1 Viewer)

[WilliamG]

There seems to be differing opinions on this w/different equipment, however I don't seem to find the right answer for my situation yet.

I have the Onkyo TX-SR600 receiver and the JBL PB12 sub. Where do I need to put the receiver crossover setting vs. the sub's?

 

[Dustin B]

Sub should be cranked as high as it can go (getting it out of the way). All speakers should be set to small, sub to yes. And unless Onkyo has changed it since the 575 the crossover is 2nd order and fixed at 80hz.

 

[WilliamG]

Dustin,
Please explain "2nd order" for me - it's been a lonnnng day!:b

 

[Chris Tsutsui]

I don't know either but I think it has something to do with how fast the volume drops off after the crossover point.
By setting the subwoofer crossover very high you are then relying on the receiver's crossover to separate the bass from the rest.
I guess this could be "best" but I never owned a receiver either.

 

[Dustin B]

http://www.hometheaterforum.com/htfo...602#post523602
It's the slope of the filters, 12dB/octave.

 

[Chris Tsutsui]

You gotta explain this so people like me would understand.
2nd order is describing the how fast the crossover filters out the sound. So a 4th order filters out sound faster while a 1st order filters sound slower.
So it's just a label that says at 80hz, the crossover will begin to filter out loudness at a rate of 12 decibels per octave (octave is a way to space the frequencies apart).
So at 80hz the speakers are playing 100% volume
At 40hz the crossover subtracts 12 decibels
at 20hz, it subtracts another 12 decibels.
and so on.
So while the speakers are lowering in volume by the crossover, the subwoofer increases in volume to form an overlapping "seemless" transition from high frequencies to bass.
I'm i'm wrong then Dustin's crossover FAQ didn't do me any good.

 

[Dustin B]

Nope, your right, except that both filters will be down 3dB at 80hz so that they sum properly.

 

[Doug BW]

both filters will be down 3dB at 80hz so that they sum properly.

Dustin, why is it that the filters are down 3dB and not 6dB at the crossover? If two speakers are playing the same signal equally loudly and in phase, than the combined sound should be twice as loud (+6dB SPL) as a single speaker.

For example, let's say we play an 80 hz test tone that's supposed to be 75 dB SPL. If the crossover sends a 72dB signal to the main speaker and a 72dB signal to the sub, they should combine at the listening position to be 78dB, or 3dB too loud. Yes? No?

(In fact, I just looked at the graph from your tutorial, and it appears that the two speakers ARE down 6dB at the crossover. But everywhere I've read, I've always seen the 3dB number quoted, so I'm really confused!)

 

[Dustin B]

Well, this is starting to get past my knowledge level. There are a bunch of different types of crossovers. Various orders of Linkwitz Riley and then a bunch of other names I can't remember. The Linkwitz Riley (most common I believe) are down 3dB and there is another type that is down 6dB (not sure how this works).

3dB is a doubling of acoustic power, 6dB is a quadrupling. But for us to percieve a doubling you need up around a 10dB increase.

 

[Doug BW]

(Dustin, it's a whole lot easier to get past my knowledge level than yours!)

I do know, though, that not all dBs are created equal. When dBs are used to refer to "power" things like watts of electricity or acoustic power, then 3dB is a doubling. When dBs are used to refer to "pressure" things like SPLs or voltage, then 6dB is a doubling. (This relates to the fact that often "power" is proportional to the square of "pressure". For example, to double the voltage across a fixed resistence requires a quadrupling of the power.)

Perhaps the crossovers used in loudspeakers between the different drivers sometimes have to deal with drivers that are somewhat out of phase with each other and so a "down 6dB" crossover would be excessive??? But the considerations might be different for bass management crossovers since people can tweak their subs to be right in phase with their mains?? Just some idle speculation....

 

[Dustin B]

Well it doesn't take long when you get down to the details of the electronics stuff. You only learn so much from a first year physics class with that stuff :p)

Hmm, where's Patman or Danny when you need them.

 

[WilliamG]

Dustin,

I checked, and my receiver defaults to 80hz; but other options are 100- and 120hz. Am I correct in thinking that 80hz is where I need to be, because if set any higher then more is filtered out?

Thanks!

 

[Dustin B]

What speakers are you using besides the PB12? It will be either 80 or 100 hz you'll want to use I imagine.

You won't cut more out with a different crossover frequency. All the info will still be there, the crossover just happens at a different point. The concern is if the crossover point gets to high, as then you can localize the sub. Lower frequencies are non-directional (why you can get away with a single speaker for the sub). High frequencies aren't. It will depend on the room and individual a bit when things will become directional. Properly setup there should be no problems with localization with an 80hz crossover. At 100hz there might be and at 120hz I'm sure there would be.

But if your speakers can't play done to 80hz with enough omph, an 80hz crossover does you little good as it will leave a hole in the response. So it's a trade off, if your speakers aren't capable of playing down to below 80hz with omph. Do you want a hole in the response or do you want to be able to localize the sub.

 

[WilliamG]

I have the JBL NSP1's (4 ea. N-24's + 1 N-Center). I've had this setup for several months and localization of the sub frequencies has not been a problem. I decided after about 3 months of good, hard usage that I'd re-calibrate them, and MAN, did it do a world of difference! Don't know why, and I've read all about speaker 'break-in periods' and all that. All I know is that there is a presence now that was not there initially. I put in The Matrix a little while ago and was thoroughly impressed at the difference.

 

[Chris Carswell]

Dustin,
I like it how you tell him 1st off, without even knowing what speakers he has, to automatically set his speakers to small. Unless I missed something in another thread that you two have discussed (or there is something different about Onkyo) I would think for it to be more appropriate to find out what he is running before telling him how to set it up.
Heck, he might have a pair of large Paradigm monitors or something........
Yes you are right in telling him to set his JBL NSP1's to small although I would run it in large then set his sub to "PLUS" mode and compare the two.

 

[WilliamG]

Chris,
I already knew to set all speakers to "small" and sub to "yes" because of previous posts of other members. It took me about 8 months of research to decide what I wanted for my first HT because I wanted to have something I could be proud of. And I credit the folks here at HTF for my success in getting what I wanted. Everyone here has differing opinions on what to get/do for the most part and that's what I like about it. See, and I *still* get an opinion that I hadn't heard before when you suggest to compare the two.
I appreciate it, and will try it out, although the other setting works just fine for me.
Thanks!
Anyone else?

 

[Dustin B]

William, with N24 bookshelves, I'd set the crossover to 100hz.
To be honest Chris, if you have a good sub, I don't know of any speaker I wouldn't set to small in a home theater environment. 99.9% of the time it is the best thing to do, for a number of reasons. There are very, very few truely full range towers. And commercially you don't really see any until you get well past $2k a pair. And even most of these won't compare to a decent sub in the last couple octaves.
http://www.hometheaterforum.com/htfo...537#post739537
The only time I'd set a speaker to large is if it was a dedicated 2ch rig and I had the appropriate external crossover (either in the sub or purchased seperately).
What does this "Plus" mode you speak of do?

 

[Chris Carswell]

I sorta figured you already had gotten some info or had already spoke with Dustin. He is helpful and wouldn't steer you in the wrong direction. I just wanted to bust him up a bit, keep him honest
"if you have a good sub, I don't know of any speaker I wouldn't set to small in a home theater environment. 99.9% of the time it is the best thing to do, for a number of reasons. There are very, very few truly full range towers. And commercially you don't really see any until you get well past $2k a pair."
I am really going to disagree with you there. Granted most of the speakers that "say" they will play low don't. This is true. I still think they should be set to large though. I feel you miss out on some of the info. I do agree with you in the fact that I don't think most full range towers can compete with a sub specially in the last octaves (say 15Hz to 30Hz area), but to knock all the bass out of it? No way. Also there are tons of speakers under $2K that are up to the full range "Large" task but again a sub will do a better job in the low, low, low, last few octaves. I feel the need for a lower xover point necessary in situations like this. Something around 40Hz to 60Hz would be good. That way more use full info that is able to be properly reproduced is sent to the speakers instead of cutting its freq. range a little short.
This is why I like the "Plus" feature. It sends the full freq. range to your speakers as well as the same info to your sub (as if you had set your speakers to small). That way whatever isn't played by your speakers is picked up by your sub. I feel it is necessary in this case to cross over the sub as low as poss that way you don't get a big overlap in freq. and have a nice db boost in that area.

 

[Dustin B]

My problem is that plus setting is gonna do funky things to the response of the system. How does the processor know how the same output from the mains and sub is going to sum in room. Bass is very problematic in the room, and with three sources outputing the same signal (two of which can't play all of it) you will end up with loads of axial and tangental room modes as well as various cancelations and reinforcements between the three speakers and a sudden drop in output capability of the system once you get to frequencies lower than what the mains can play. Result will be a rather wild looking frequency response in the bass department.

A true full range stereo source played through a pair of true full range speakers is one thing. A 5.1 or 6.1 multi-channel sound track is another thing. The issues invovled in copying the LFE track and bass from other speakers around isn't trivial. Something like a Lexicon MC12 I might trust to get a more elaborate bass management scheme right. But for the majority of equipment I'd like to keep it simple. All speakers small. Last two octaves to the sub, 3rd is where the bulk of the over lap in the crossover occurs and 4th and up to the speakers (in other words an 80hz crossover, granted I'd like to see 4th order and most are 2nd order though). With all these problematic bass frequencies being summed and sent to a single source you then dramatically simplify room interactions (only one set of room modes and no interspeaker interactions). Much easier to deal with placement and EQ in this situation than in the other.

If you can localize the sub with an 80hz crossover or the bass seems anemic, it's not the crossover's fault, it's the sub's fault. It is either producing some bad harmonics/placed poorly or just isn't a good sub.

 

[Larry B]

Dustin:

The concern is if the crossover point gets to high, as then you can localize the sub.

Why is this considered bad? It seems that if our ear/brain is capable of localizing a given frequency, then you would want to do so in your HT. Or is the problem that the sub is in a different location from the actual event seen on the monitor?

Larry