[ricardojoa]

It seems the general rule is to crossover at 80hz in the case with Avr. But as far as i know, this is the roll off point. Why would someone want to cross at their roll of point? Woulndt that create xcess energy at 80hz or create a null when out phase with the main. If the fronts are rolling at 80, wouldnt be better to have the sub roll at around 60-50hz, assuming at the rate of 12 db?

[JerryLove]

You can create a null: that's why there's a phase inverter (or phase dial) on most all amps.

The crossover setting is intended to be the spot where the plots from the two drivers in question "cross over" or meet... so it should be the same for both.

I think 80 is actually a THX standard.

[JohnR]

It's not always best to cross over at all: http://www.hifizine.com/2011/06/bass-integration-guide-part-1/

[JLM]

80 Hz is the THX standard, so all A/V receivers will follow it.  The crossover should work like any other in that the sum from both sources should add to produce a flat frequency response (the drop offs start on either side of the stated crossover frequency).

The size of sound waves must be considered as it relates to phase issues.  The equation is 1130 ft/second divided by the frequency in Hertz (Hz).  Example: an 80 Hz sound wave is 1130 / 80 = 14.1 feet long.  So at that length phase issues are quite secondary.  Higher frequencies are shorter, lower frequencies are longer.

It is generally agreed that below 100 Hz, the direction of sound is not discernible, so it's OK to combine channels.  (Unfortunately most have taken that to mean that one sub/system or room is also OK, which it definitely isn't for obtaining a flat frequency response, as referenced in JohnR's link.  Considering bass sound waves being 20 - 60 feet long and equating them to large waves in a bath tub you can see how the waves will easily add or cancel out, creating huge variations in the space.)

[ricardojoa]

You can create a null: that's why there's a phase inverter (or phase dial) on most all amps.

The crossover setting is intended to be the spot where the plots from the two drivers in question "cross over" or meet... so it should be the same for both.

I think 80 is actually a THX standard.

Jerry,

i understand that the xover point should be the same for both the high pass and low pass, after all this is where the high meet the low. What im confused is, if the avr is stating 80HZ xover, that could be either the roll of point or xover point  or both at the same time. In the case of both at the same time, the xover point would be at 0db. But in case if that is the roll off point, and in the case where the sub low pass is set to 60-50HZroll of, the crossover point would be at different and at different db. It is essentially blending both(mains+sub) at a lower db xover point.
Does that make sense? If one is xover at 80HZ at 0db that would create too much ovelap at 80hz.

[ricardojoa]

this graph shows what im talking about.

[ricardojoa]

It's not always best to cross over at all: http://www.hifizine.com/2011/06/bass-integration-guide-part-1/

Thanks for the article.
Based on the article, it seems that the xover point just hapeend at much higher point. In many case, the abudant overlap doesnt work well in home invironment or does it? And that would be assuming that the sub and main are at the same phase but this is probably the bigger issue with integrating sub because sub it is always in phase lag.

[ricardojoa]

80 Hz is the THX standard, so all A/V receivers will follow it.  The crossover should work like any other in that the sum from both sources should add to produce a flat frequency response (the drop offs start on either side of the stated crossover frequency).

The size of sound waves must be considered as it relates to phase issues.  The equation is 1130 ft/second divided by the frequency in Hertz (Hz).  Example: an 80 Hz sound wave is 1130 / 80 = 14.1 feet long.  So at that length phase issues are quite secondary.  Higher frequencies are shorter, lower frequencies are longer.

It is generally agreed that below 100 Hz, the direction of sound is not discernible, so it's OK to combine channels.  (Unfortunately most have taken that to mean that one sub/system or room is also OK, which it definitely isn't for obtaining a flat frequency response, as referenced in JohnR's link.  Considering bass sound waves being 20 - 60 feet long and equating them to large waves in a bath tub you can see how the waves will easily add or cancel out, creating huge variations in the space.)

So when an avr state 80HZ xpoint,  does that mean that is the roll of point? Thats what im confused.

[JLM]

Or just dump those nasty crossovers and buy truly full range single driver speakers (rare).

Crossovers are, at best, necessary evils.  They reduce efficiency, introduce phase and intermodulation distortions, and obscure the amp from "seeing" the simple/pure load from a single driver.  The best crossovers are found in active designs (one amp dedicated to each driver) where they only handling low level signals and so can be more sophisticated and made of premium parts.

The stated crossover point is where the signals cross in the above diagram.

[ricardojoa]

Or just dump those nasty crossovers and buy truly full range single driver speakers (rare).

Crossovers are, at best, necessary evils.  They reduce efficiency, introduce phase and intermodulation distortions, and obscure the amp from "seeing" the simple/pure load from a single driver.  The best crossovers are found in active designs (one amp dedicated to each driver) where they only handling low level signals and so can be more sophisticated and made of premium parts.

The stated crossover point is where the signals cross in the above diagram.

That would need anothr topic on xover.
 On the same topic. Is the xover setting on most avr, the roll off point or it is actually the xover point.
Todays avr actually have different over setting for mains and subs, so that make things confusing.

[JohnR]

Thanks for the article.
Based on the article, it seems that the xover point just hapeend at much higher point. In many case, the abudant overlap doesnt work well in home invironment or does it? And that would be assuming that the sub and main are at the same phase but this is probably the bigger issue with integrating sub because sub it is always in phase lag.

The overlap can work well. The graph I was thinking about is actually in part 3 - http://www.hifizine.com/2012/06/bass-integration-guide-part-3/ - Figure 17. The idea is that by increasing the effective number of sources you may be able to smooth the response in the overlap region. However, the only way to know is to measure it.

There are tradeoffs - depending on the mains, they may be better off being highpassed.

I find that the simplest way to do the subwoofer crossover is to use delay to align the impulse responses of the subs and mains and EQ to extend the response past the crossover point. Then use a symmetric crossover filter. However if the mains are rolling off at the same frequency then the sub lowpass will (may) need to be steeper. And if you have a lot of room interaction around there then adjusting the crossover points/slopes can be used to smooth things out.

Hope this helps, I'm not quite sure of what your question is

[medium jim]

The overlap can work well. The graph I was thinking about is actually in part 3 - http://www.hifizine.com/2012/06/bass-integration-guide-part-3/ - Figure 17. The idea is that by increasing the effective number of sources you may be able to smooth the response in the overlap region. However, the only way to know is to measure it.

There are tradeoffs - depending on the mains, they may be better off being highpassed.

I find that the simplest way to do the subwoofer crossover is to use delay to align the impulse responses of the subs and mains and EQ to extend the response past the crossover point. Then use a symmetric crossover filter. However if the mains are rolling off at the same frequency then the sub lowpass will (may) need to be steeper. And if you have a lot of room interaction around there then adjusting the crossover points/slopes can be used to smooth things out.

Hope this helps, I'm not quite sure of what your question is

Absolutely High Pass the mains....

Jim

[ricardojoa]

The overlap can work well. The graph I was thinking about is actually in part 3 - http://www.hifizine.com/2012/06/bass-integration-guide-part-3/ - Figure 17. The idea is that by increasing the effective number of sources you may be able to smooth the response in the overlap region. However, the only way to know is to measure it.

There are tradeoffs - depending on the mains, they may be better off being highpassed.

I find that the simplest way to do the subwoofer crossover is to use delay to align the impulse responses of the subs and mains and EQ to extend the response past the crossover point. Then use a symmetric crossover filter. However if the mains are rolling off at the same frequency then the sub lowpass will (may) need to be steeper. And if you have a lot of room interaction around there then adjusting the crossover points/slopes can be used to smooth things out.

Hope this helps, I'm not quite sure of what your question is

Well,
the reason why i suddenly came up with this question is because of my current main and sub setting.
I have marantz avr crossover at 80hz with rythmil 15 setting at 50HZ/24. The recommended settings from rythmik for those using avr is actually to have ext/12 on the rythmik sub and just use the avr internal crossover. Yet, in my case, i have the front cross at 80HZ while my sub are rolling at 50HZ. I find this setting to have much better bass definition and extension. I was onlyale to use my iphone db meter(haha, yea i know), and the response from 100 down was decently flat. i did not find any null like alot of people find. i did have some bump around the 50-60hz which i use the peq to tame it. I will find a real meter and do a back to back measurements. I guess the room played the overall response.

[ctviggen]

Absolutely High Pass the mains....

Jim

I used to crossover the mains, now I never do.  More bass spread throughout the room can be good. The only time it's bad is if the bass for blurays/DVDs gets sent to mains, but that's not the case in my system.   I have two subs I've attempted to place in "random" positions (as random as I could put them). 

[JohnR]

Absolutely High Pass the mains....

No, not necessarily...

Yet, in my case, i have the front cross at 80HZ while my sub are rolling at 50HZ. I find this setting to have much better bass definition and extension.

I suspect it's probably related to the delay/phase shift between your subs and the mains. And a crossover filter has its own phase shift, so changing the frequency can make changes to the response that are more dramatic than just the amplitude slope would suggest. But, it's the final response that counts 

[medium jim]

No, not necessarily...

I suspect it's probably related to the delay/phase shift between your subs and the mains. And a crossover filter has its own phase shift, so changing the frequency can make changes to the response that are more dramatic than just the amplitude slope would suggest. But, it's the final response that counts 

JohnR:

You are right, it all depends on the system....in my case, to highpass was a must!

Jim

[James Romeyn]

I used to crossover the mains, now I never do.  More bass spread throughout the room can be good. The only time it's bad is if the bass for blurays/DVDs gets sent to mains, but that's not the case in my system.   I have two subs I've attempted to place in "random" positions (as random as I could put them).

Scroll down to my sub's setup instructions HERE.  It adapts Bob Carver's setup advice for one sub (the most effective "null point" with the least bass output) to a Distributed Array.  Least bass output has the least modal effects, the exact opposite of putting a sub in the corner.  Users can continue, step by step, up to any quantity of subs, two in your case, four in my case.  I call it "Progressive Null Points." 

Depending on how similar or different is the bass output of your subs vs. mains, you might increase smoothness by inverting the polarity of one sub.  The down side with only two subs is you'll almost certainly loose too much low bass energy.  This is one of the benefits of four subs (better even than three). 

In my room, with horrific modes, one sub ideally located at the ideal null point yields a 13 dB response window 100-20 Hz (-6 dB @ 20 Hz).  Four subs properly setup per instructions yields a 6 dB window (-1.5 db @ 20 Hz), both cases no EQ/no bass treatment.  The benefit of using no EQ for this moderately tight 6 dB window is very similar response everywhere in the room, including corners.  With your ear 1" from any sub you can not tell it plays unless you physically contact the sub, even at maximum output.       

In my case main speakers are sealed, rolling off in the high-50 Hz range, active high-pass crossed 2nd order @ 80 Hz.  So the HP filter starts 2nd order @ 80 Hz then increases to 4th order around 57 Hz.  Conversely the bass LP starts 4th order @ 67 Hz then increases to 6th order @ 80 Hz. 

Really dig the ability to remotely tune bass level up/down by 1 dB steps below 80 Hz.

[josh358]

Jerry,

i understand that the xover point should be the same for both the high pass and low pass, after all this is where the high meet the low. What im confused is, if the avr is stating 80HZ xover, that could be either the roll of point or xover point  or both at the same time. In the case of both at the same time, the xover point would be at 0db. But in case if that is the roll off point, and in the case where the sub low pass is set to 60-50HZroll of, the crossover point would be at different and at different db. It is essentially blending both(mains+sub) at a lower db xover point.
Does that make sense? If one is xover at 80HZ at 0db that would create too much ovelap at 80hz.

Ricardjoa, the way crossovers work they should sum to unity at the crossover point (well, not always quite, not all crossover curves are maximally flat, but that's the general idea). In other words, when you set your crossover to 80 Hz, neither the signal to the sub nor the mains are flat at 80 Hz; rather, each is rolled off at 80 Hz so the summed response is flat.

[James Romeyn]

Ricardjoa, the way crossovers work they should sum to unity at the crossover point (well, not always quite, not all crossover curves are maximally flat, but that's the general idea). In other words, when you set your crossover to 80 Hz, neither the signal to the sub nor the mains are flat at 80 Hz; rather, each is rolled off at 80 Hz so the summed response is flat.

IIRC, for symmetrical LP/HP filter, the pole frequency indicates the -3 dB point on the two slopes.  So, -3 dB @ 80 Hz (low pass) plus -3 dB @ 80 Hz (high pass) sums to 0 dB...or, two identical signals @ -3 dB (@ 80 Hz) sum to = 0 dB @ 80 Hz.