Do mambers believe in or follow 90HZ crossover?

[chadnliz]

I am just curious how many follow these "rules" invented by Lucas films, this thread is mostly aimed at folks who run full-range speakers or ones capable of low bass. Now I know many follow this rule and champion the hole THX rules but it makes no sense to me when I see folks with 2, 3, 5, or even 7 speakers capable of far greater low level performance crossing the rig over at the 80HZ mark and sending all other info to a sub (and in many cases a poorly performing one. It is my belief that if you have the ability to adjust your individual slopes wether it be 30, 40, 60 or even 70HZ, capable amps with power reserves AND efficient enough speakers that can comfortably handle deeper bass you should be all means set your Processor/Reciever accordingly for a more entertaining and dynamic experience.
My mains run full (capable to 16HZ), or sometimes 40HZ based on my mood swings, center at 40HZ and all 4 surrounds at 80HZ along with a sub.......what do you guys think?
I understand somebody had to come up with a standard and given space and price issues 80HZ makes sense but, after more then a few years in the HT game and more advanced and adjustable equipment the rules have changed, atleast for me........thanks for the time.

 

[chadnliz]

sorry I meant 80HZ...DARN TYPOS!

 

[MDS]

The standard isn't arbitrary. As a general rule you want the xover to be 1/2 to 1 octave above the F3 point of the least capbable speaker. This is because the xover is not a brickwall but rather a slope that gradually attenuates the signal towards the xover point. With speakers that go down to 40 Hz, an 80 Hz xover is ideal.

Remember if your xover is 80 Hz, the high pass will start below 80 Hz and gradually attenuate the signal so that 80 Hz or so is essentially unchanged. Likewise, the low pass will start above 80 Hz and attenuate the signal so that 80 Hz is essentially unchanged.

If you were to plot the frequency response of the main speakers with respect to the xover you would see that the goal is to make the two graphs intersect at the xover point for a perfect hand-off at that point for a seamless transition between the two.

 

[bandphan]

I am just curious how many follow these "rules" invented by Lucas films, this thread is mostly aimed at folks who run full-range speakers or ones capable of low bass. Now I know many follow this rule and champion the hole THX rules but it makes no sense to me when I see folks with 2, 3, 5, or even 7 speakers capable of far greater low level performance crossing the rig over at the 80HZ mark and sending all other info to a sub (and in many cases a poorly performing one. It is my belief that if you have the ability to adjust your individual slopes wether it be 30, 40, 60 or even 70HZ, capable amps with power reserves AND efficient enough speakers that can comfortably handle deeper bass you should be all means set your Processor/Reciever accordingly for a more entertaining and dynamic experience.
My mains run full (capable to 16HZ), or sometimes 40HZ based on my mood swings, center at 40HZ and all 4 surrounds at 80HZ along with a sub.......what do you guys think?
I understand somebody had to come up with a standard and given space and price issues 80HZ makes sense but, after more then a few years in the HT game and more advanced and adjustable equipment the rules have changed, atleast for me........thanks for the time.

what mains are you using?

 

[TLS Guy]

I am just curious how many follow these "rules" invented by Lucas films, this thread is mostly aimed at folks who run full-range speakers or ones capable of low bass. Now I know many follow this rule and champion the hole THX rules but it makes no sense to me when I see folks with 2, 3, 5, or even 7 speakers capable of far greater low level performance crossing the rig over at the 80HZ mark and sending all other info to a sub (and in many cases a poorly performing one. It is my belief that if you have the ability to adjust your individual slopes wether it be 30, 40, 60 or even 70HZ, capable amps with power reserves AND efficient enough speakers that can comfortably handle deeper bass you should be all means set your Processor/Reciever accordingly for a more entertaining and dynamic experience.
My mains run full (capable to 16HZ), or sometimes 40HZ based on my mood swings, center at 40HZ and all 4 surrounds at 80HZ along with a sub.......what do you guys think?
I understand somebody had to come up with a standard and given space and price issues 80HZ makes sense but, after more then a few years in the HT game and more advanced and adjustable equipment the rules have changed, atleast for me........thanks for the time.

Lucas is a film man, and his priority is movies. For music an integrated system is best. Now if you have a generic crossover, you won't get a seamless splice.

All drivers roll off differently. to say nothing of the loading. Ported are 24db roll off/octave and sealed 12db roll off. However all of the drivers will have unique features to their roll offs. To make a seamless crossover you have to specifically design the high and low pass crossover slopes to sum with the driver slopes to achieve the order of crossover you desire. In addition you have to decide whether the the crossover will be constant voltage or constant power, depending on your situation. Now that won't happen with brand A speaker, Brand B sub and Brand C crossover.

If your speakers are really good, which they appear to be, I would run them full range and just send the LFE for Hollywood's whizz bang to the sub. I have heard many a good speakers not performing well because of slavish following of the THX rules.

I designed my speakers as an integrated system. I don't use a sub per se, and you probably don't need to either if your mains can reach 16 Hz. I have a way of blending the LFE channel into the mix.

Bottom line, if you have nice speakers with a deep accurate last octave, don't spoil them with an unnecessary crossover. Crossovers are the root of a large number of loudspeaker ills.

By the way my system stills sounds excellent for movies, and you certainly don't need chair vibrators!

 

[3db]

Lucas is a film man, and his priority is movies. For music an integrated system is best. Now if you have a generic crossover, you won't get a seamless splice.

All drivers roll off differently. to say nothing of the loading. Ported are 24db roll off/octave and sealed 12db roll off. However all of the drivers will have unique features to their roll offs. To make a seamless crossover you have to specifically design the high and low pass crossover slopes to sum with the driver slopes to achieve the order of crossover you desire. In addition you have to decide whether the the crossover will be constant voltage or constant power, depending on your situation. Now that won't happen with brand A speaker, Brand B sub and Brand C crossover.

If your speakers are really good, which they appear to be, I would run them full range and just send the LFE for Hollywood's whizz bang to the sub. I have heard many a good speakers not performing well because of slavish following of the THX rules.

I designed my speakers as an integrated system. I don't use a sub per se, and you probably don't need to either if your mains can reach 16 Hz. I have a way of blending the LFE channel into the mix.

Bottom line, if you have nice speakers with a deep accurate last octave, don't spoil them with an unnecessary crossover. Crossovers are the root of a large number of loudspeaker ills.

By the way my system stills sounds excellent for movies, and you certainly don't need chair vibrators!

But aren't the filter settings on the receiver digital? How do these filters behave? Are they modelled after Butterworth, etc?

 

[TLS Guy]

But aren't the filter settings on the receiver digital? How do these filters behave? Are they modelled after Butterworth, etc?

Who knows. I doubt they are digital, that is new technology and relatively expensive. I suspect they are analog op amp crossovers digitally switched. Orders I suspect are either second or fourth, but who knows. It is generally not stated. As to whether they are Linkowitz Riley, Butterworth, Bessel, Chebychev or something else who knows?

Digital brick wall filtering may come of age. However if you have a nice set of speakers with a nicely balanced low coloration low end, it is probably best to use it. B & W are on my team with this one by the way. So I do have soem respectable company. Whatever else they may be, Lucas Labs are not designers of superb loudspeakers.

 

[3db]

Who knows. I doubt they are digital, that is new technology and relatively expensive. I suspect they are analog op amp crossovers digitally switched. Orders I suspect are either second or fourth, but who knows. It is generally not stated. As to whether they are Linkowitz Riley, Butterworth, Bessel, Chebychev or something else who knows?

Digital brick wall filtering may come of age. However if you have a nice set of speakers with a nicely balanced low coloration low end, it is probably best to use it. B & W are on my team with this one by the way. So I do have soem respectable company. Whatever else they may be, Lucas Labs are not designers of superb loudspeakers.

I guess it would depend where in the signal path teh filtering starts. If starts to get filtered as it enters the receiver as a raw bit stream, then I would guess digital filtering would be employed. *L* Conversely after the D/A conversion..blah blah blah.

 

[no. 5]

It is my belief that if you have the ability to adjust your individual slopes wether it be 30, 40, 60 or even 70HZ, capable amps with power reserves AND efficient enough speakers that can comfortably handle deeper bass you should be all means set your Processor/Reciever accordingly for a more entertaining and dynamic experience.

Even if the speakers can comfortably go that low, and the amplifier has the power, there is still the issue of the room. Even if all seven loudspeakers are identical, they will all have different in room low frequency response relative to each other.

Home Theater and Hifi had an artical on the topic of crossovers (the link to the Floyd Toole paper is broken, but the paper is here).

 

[chadnliz]

My speakers are VMPS FF3SRE in a Horizontal Bi-Amp with outboard active Cross-over, I get flat bass to 22HZ and down 10db at 16HZ.
One contributer pointed out my speakers can run full range which I have and do set them to but my question is how low is that potential information going to go to the fronts, does it cut of front L&R at 20Hz, or even lower?
My Rotel RSP 1068 has option for fullrange PLUS sub and at times I get a bit uncomfortable going full range choosing many times to roll off at 40HZ and let the sub takes the abuse, being a 2 channel music guy at heart I hate to think I over drive a woofer trying to pump out a 100db thunder burst. Thanks for the participation! Chad

 

[bandphan]

this is the responce one of the field techs gave to a client.


You should set your sub to around 80-100hZ. Even though your regular speakers go lower the purpose of the sub is reproduce not only what your mains can not but to produce the Low Effects as well. . . By putting your "movie bass" on a seperate channel you get the flexibility to set it where ever you like it best which ultimatly is the correct setting regardless of the number.

Typically the reason for crossing a sub as low as possible is to prevent localizing or finding it however if you stay under about 125-150hZ you are not going to find it anyway depending on room, placement etc.

Your subwoofer is in addition to your other speakers in HT so do not worry about your crossover point too much unless it is extremly high. Crossing your sub higher saves amplifier power and gives you cleaner sound as your mains find it easier to reproduce higher frequencies than the full range. Speaker builders are notorious about claiming their speakers play lower bass than they actually play. Most speakers with a 35-20KhZ rating are down quite a bit at the 35 point some as much as 12dB. Making that speaker's response flat from around 50 instead of the lower number.

You need the flexibility to set your LFE at a higher volume than is easy to do from your mains. Putting your bass and LFE on one channel makes it much easier, quicker and lets it come from a speaker designed to play those frequencies only.

My advice is set it where it sounds best to you, that is the correct point. It may take you a long time to get it right don't worry about it.

 

[TLS Guy]

My speakers are VMPS FF3SRE in a Horizontal Bi-Amp with outboard active Cross-over, I get flat bass to 22HZ and down 10db at 16HZ.
One contributer pointed out my speakers can run full range which I have and do set them to but my question is how low is that potential information going to go to the fronts, does it cut of front L&R at 20Hz, or even lower?
My Rotel RSP 1068 has option for fullrange PLUS sub and at times I get a bit uncomfortable going full range choosing many times to roll off at 40HZ and let the sub takes the abuse, being a 2 channel music guy at heart I hate to think I over drive a woofer trying to pump out a 100db thunder burst. Thanks for the participation! Chad

You have four voice coils handling the bass in each of those speakers. I would bet they have a far better bass response than 99% of subs available.
I don't think you will damage them, almost certainly they are more robust than your sub. I would definitely just sent the LFE with the Hollywood thunder to the sub if you are worried.

I would certainly set those to large. I have a Rotel preamp also. If you are worried about the other speakers you could set them to small and the bass of them to the sub. What are the other speakers in the system?

 

[Soundman]

The standard isn't arbitrary. As a general rule you want the xover to be 1/2 to 1 octave above the F3 point of the least capbable speaker. This is because the xover is not a brickwall but rather a slope that gradually attenuates the signal towards the xover point. With speakers that go down to 40 Hz, an 80 Hz xover is ideal.

Remember if your xover is 80 Hz, the high pass will start below 80 Hz and gradually attenuate the signal so that 80 Hz or so is essentially unchanged. Likewise, the low pass will start above 80 Hz and attenuate the signal so that 80 Hz is essentially unchanged.

If you were to plot the frequency response of the main speakers with respect to the xover you would see that the goal is to make the two graphs intersect at the xover point for a perfect hand-off at that point for a seamless transition between the two.

Excellent point!