Are you missing part of your LFE track?

cnjvh

If you set your crossover lower than 80hz, you might be. Setting your crossover to say 60 causes all freqencies below 60 to be redirected from your mains to your sub but here's the kicker: frequencies above 60 in the LFE track are not redirected to the mains - they are simply lost. This is why THX recommends the 80hz settings. Their findings found this to be the best compromise between localiazable bass and frequencies that were actually found in LFE tracks.

In the majority of surround sound processors and receivers, FULL RANGE copies of all channels set to "Small" are combined together with the LFE channel, and the sum is low-passed. Think about that. Strictly speaking, any* such processor with a sub/sat crossover frequency set lower than 120 Hz is "discarding" the upper end of the LFE channel. THX units are NOT exempt from this. With the standard THX 80 Hz 4th order crossover, the top of the LFE channel gets chucked.

Don't panic. This has been going on since day one, and virtually nobody has noticed . . . with good reason. I've said many times before, and I will say it again: THX did not pull their crossover out of thin air. It is the product of much development, and, when used in concert with THX speakers (or others which exhibit the correct roll-off), represents the best overall compromise of minimizing localization, extending dynamic range, and as it turns out, minimizing LFE truncation. When Dolby Digital was coming to the consumer marketplace, THX looked at an inordinate number of modern 5.1 soundtracks and guess what they found in the LFE channel: not much at all in the region of 80 Hz - 120 Hz, making their original choice of 80Hz rather fortuitous. Dolby Digital's LFE channel has a digital brick wall at 120 Hz, not a roll-off, so content creators almost always roll-off their stuff, usually somewhere around 80 Hz. Therefore, chucking the top band of the LFE is no big deal but the argument here is that a standard SSP crossover set much lower than 80Hz or so may actually be costing you bass content."

Article here:

http://www.hometheaterhifi.com/volume_9_3/feature-article-multiple-crossovers-9-2002.html

Skynut

Good info, thanks

bknauss

Good info. Since LFE is a discrete channel, its only going to send certain info to the sub and not the other channels.

engtaz

Thanks

cnjvh

No problem. This is an obscure issue that never even occured to me until coming across the article. I've alway run as low as possible without going below my mains+surrounds -3db point but after coming across this info I will be revisiting 80 again :-)

jakelm

Thats why when using the Auto EQ on my HK635, the reciever keeps setting my main left and right to 120hz and sets my sub to 120hz. When I clearly know my Polk 7b's can go way below that. But in turn sets my center to large....

HMMMMM..Interesting.....

Maybe my HK635 is THX certified...wooohooooo

PolkThug

Interesting. I wonder if this varies on different AVR's.

jakelm

Well it has always and continues to baffle me why my 635 would set my mains to 120hz and my center to large. I have 2 12" subs, one Dayton and the other SVS, yet the HK continues to set them as 10's with 120hz crossover.

I quit trying to understand the logic in EZ EQ.....

This write up just adds more question....

Lowell_M

jakelm wrote: »

Well it has always and continues to baffle me why my 635 would set my mains to 120hz and my center to large. I have 2 12" subs, one Dayton and the other SVS, yet the HK continues to set them as 10's with 120hz crossover.

I quit trying to understand the logic in EZ EQ.....

This write up just adds more question....

HMMM.... My 635 crosses my RTi70's over at 60hz and my 12" at 12"s. i tweak the settings a little after going through the setup. (set the sub a few db's hotter, adjust the center crossover etc.), Overall, though, I'm quite happy with the results from the EasyEQ. The resultant bass management is quite impressive in my room. I get deep, but tight bass with no localization.

jrlouie

cnjvh wrote: »

If you set your crossover lower than 80hz, you might be. Setting your crossover to say 60 causes all freqencies below 60 to be redirected from your mains to your sub but here's the kicker: frequencies above 60 in the LFE track are not redirected to the mains - they are simply lost. This is why THX recommends the 80hz settings. Their findings found this to be the best compromise between localiazable bass and frequencies that were actually found in LFE tracks.

It seems like I have heard this before. I thought what I had found is that cross-overs are applied to your mains/center/surrounds, but not to your LFE signal. So, the whole LFE signal always goes to your sub, even if it is above your cross-over point. At least, that is what Outlaw told me about my 990.

jrlouie

here we go...
http://www.polkaudio.com/forums/showthread.php?t=39509

Lowell_M

jrlouie wrote: »

It seems like I have heard this before. I thought what I had found is that cross-overs are applied to your mains/center/surrounds, but not to your LFE signal. So, the whole LFE signal always goes to your sub, even if it is above your cross-over point. At least, that is what Outlaw told me about my 990.

That's what I thought also.

jakelm

a_mattison wrote: »

HMMM.... My 635 crosses my RTi70's over at 60hz and my 12" at 12"s. i tweak the settings a little after going through the setup. (set the sub a few db's hotter, adjust the center crossover etc.), Overall, though, I'm quite happy with the results from the EasyEQ. The resultant bass management is quite impressive in my room. I get deep, but tight bass with no localization.

Think there might be something wrong with my HK?

cnjvh

I suspect, as PolkThug hinted at, this could be very avr/pre-pro specific. I believe DVE has a 40-120Hz LFE sweep. I suppose one could set their crossover at 80 and see what happens when the sweep goes above 80.

cnjvh

In DVE under Program Guide -> Title Index -> 10. System Response -> 16. LFE there is an LFE only 15-150 sweep with an on screen display showing what freq. is being played. You could play this with your crossover at it's lowest and highest setting. If you here a drastic difference, your AVR is applying the crossover to the LFE. If it sounds no different, your AVR is ignoring the crossover for LFE.

jakelm

cnjvh wrote: »

In DVE under Program Guide -> Title Index -> 10. System Response -> 16. LFE there is an LFE only 15-150 sweep with an on screen display showing what freq. is being played. You could play this with your crossover at it's lowest and highest setting. If you here a drastic difference, your AVR is applying the crossover to the LFE. If it sounds no different, your AVR is ignoring the crossover for LFE.

I ran this, my subs have a pretty flat responce all the way to 130hz before they clearly rolloff. On my HK I can specifically set the sub size and xover. I have them set to 60hz on the avr. I dont understand this.

Gaara

I remember reading about this a while back and it only effects certain units. I am not sure if it is just a rcvr thing but I had the LFE cutoff issue with my Yamaha HTR-5590 way back when, but don't currently with my B&K Ref 50.

Jared

cnjvh

When I ran the LFE only sweep with my crossover set at 40 and 150 the result was identical. With the crossover set at 40, I could clearly hear the entire LFE sweep so my AVR (Denon 3805) does not truncate the LFE based on crossover.

This may not the the widespread problem the article makes it out to be but definatley something to be aware of. The article is 5 years old so it's probably something that many manufacturers have corrected.

jakelm

cnjvh wrote: »

When I ran the LFE only sweep with my crossover set at 40 and 150 the result was identical. With the crossover set at 40, I could clearly hear the entire LFE sweep so my AVR (Denon 3805) does not truncate the LFE based on crossover.

This may not the the widespread problem the article makes it out to be but definatley something to be aware of. The article is 5 years old so it's probably something that many manufacturers have corrected.

I had the same results, though I dont think its a problem. I heard the enitre sweep to 130hz. I was dissapointed at first, but after another very small volume calibration, I watched ROTK and it was an amazing experience once again. I guess HK knows what thier doing. No "boom" (like I thought it would be), just a smooth, dynamic sound.

In regaurds to my other post about the HK and its crossover settings. I turned to crossover on the subs as high as they can go. 160hz on the Rythmik amps. I closed the distance of the mic from my mains, about 2' (from 18' to 16'). I reran the EZeq and PRESTO. Mains are now 80hz, center and surrounds are 100hz. What a difference 2' and bypassing the plate amps' crossovers made.

4 months I have had this AVR and all that time I have tweaked it in every way. But for 4 months, I have been doing it wrong....

Live and learn....

Dr. Spec

Some AVRS will low pass the LFE channel along with the speaker channels, and other AVRs will not.

Most AVRs won't low pass the LFE channel because doing so will send that information into electronic oblivion.

As others have stated, the best way to tell is with an LFE channel sweep. Set your speakers to Small with a very deep XO (like 40-50 Hz) and then run the LFE channel sweep. If you still get equal volume bass at the highest frequency of the sweep (usually 100-130 Hz depending on the DVD), then AVR is not low passing the LFE channel.

cnjvh

Welcome back, Dr. We haven't seen you around for a while!!

Dr. Spec

Thanks - I've been BTTW in Sales and Tech Support, but CP has always held a soft spot in my heart and it's one of the best audio forums on the internet IMO. I'm trying to make the rounds more diligently lately. :^)

jrlouie

jrlouie wrote: »

It seems like I have heard this before. I thought what I had found is that cross-overs are applied to your mains/center/surrounds, but not to your LFE signal. So, the whole LFE signal always goes to your sub, even if it is above your cross-over point. At least, that is what Outlaw told me about my 990.

Turns out I was told wrong by Outlaw. There currently is a thread going on in their forum about this. I decided to run my own tests. The 990 does truncate the LFE signal.
Outlaw Thread

Sorry if I mislead anyone about the 990.

McLoki

jrlouie wrote: »

Turns out I was told wrong by Outlaw. There currently is a thread going on in their forum about this. I decided to run my own tests. The 990 does truncate the LFE signal.
Outlaw Thread

Sorry if I mislead anyone about the 990.

The NAD T163 will truncate the bass as well. Therefore I have all crossovers set to 80hz. (works better in my room since I have my bass shaped with a BFD anyway)

Michael

Dr. Spec

A 120 Hz XO just to preserve the entire LFE channel is probably not needed.

While Dolby does indeed spec the LFE channel to 120 Hz with brick wall filter, in reality there is very little content in the LFE channel above 80 Hz. Mixing engineers do this deliberately because they know most people use an 80 Hz XO when setting the speaks to Small.

John K.

Well, JR, my "hopefully correct" comment(about an Outlaw reply) in the thread from last year which you linked was apparently appropriate, since your tests appear to conclusively show the opposite. As Ed points out, and I also mentioned last year, although the LFE channel in theory extends to 120Hz, in practice little or nothing in actual content is there above about 80Hz . No need to adversely affect other matters by using a 120Hz crossover, since the 80Hz crossover provides for essentially all of the LFE.

Lancito

I have a few questions regarding what is discussed here in this thread.

1. If the LFE channel is theory extends from 80Hz-120Hz, why does the DENON 2808 have its LFE extend up to 250Hz?

2. Why do I get different LFE setting recommendations from SVS 120Hz, HSU 90Hz, and other people who want LFE strictly to stay at 80Hz?

120Hz for me sounds too boomy. I think somewhere between 80Hz to 90Hz works best.

Face

It depends on the size and tuning of your speakers and sub(s). Some small speakers can't handle below 120-250Hz, just as some large subs sound terrible over 60-80Hz.

kuntasensei

Lancito, your Denon doesn't have its LFE extend to 250Hz. LFE = the low frequency effects channel. Your Denon is asking for the crossover frequency, i.e. the point at which bass is redirected to the subwoofer from the other channels. Subwoofer does NOT equal LFE. The subwoofer channel as output by your receiver equals redirected bass from the other channels + LFE. The ability to set the system crossover up to 250Hz is just to maintain good sound with smaller speakers, though it does make the subwoofer more easy to localize if you run it that high. The proper setting for this depends on the capability of your speakers as well as how your room interacts with them. Fortunately, your Denon's Audyssey setup should do a good job of detecting a good system crossover if done properly (i.e. with the mic on a tripod at the main listening position for the first position of detection, at ear level with the mic slightly above your seating's headrests).

And since we're reviving this long dead thread, I disagree with people who say there's little above 80Hz in the LFE channel of surround mixes. Many surround tracks have significant energy above 80Hz in the LFE channel, even if only the harmonics for the sub-80Hz material (Sorry, Ed! Don't make me chart some discs digitally like I did DVE!). Though the bass above 80Hz may not be as important as far as the goal of producing low frequency effects, the harmonics above 80Hz do affect the perceived tone of material placed in the LFE channel. My Onkyo 705 lets you independently adjust the LFE cutoff separately from the individual speaker crossovers. The default is the THX conceit of 80Hz. I've found that there is a definite though subtle difference by running the LFE cutoff at 120Hz, though I'm crossing my individual channels over at lower points than that.

A good example is the opening scene of the first Lord Of The Rings movie, where Sauron is killed. There's a bass sweep that happens. I can change between 80 and 120 for the LFE cutoff and it makes a very obvious difference in the way that bass sweep sounds. My system consists of a SVS 20-39CS+ running through a Samson 1,000w amp, with RTi70 mains (60Hz crossover on the Onkyo), CSi40 center (70Hz crossover) and RTi28 surrounds (80Hz crossover).

Lancito

kuntasensei wrote: »

Lancito, your Denon doesn't have its LFE extend to 250Hz. LFE = the low frequency effects channel. Your Denon is asking for the crossover frequency, i.e. the point at which bass is redirected to the subwoofer from the other channels. Subwoofer does NOT equal LFE. The subwoofer channel as output by your receiver equals redirected bass from the other channels + LFE. The ability to set the system crossover up to 250Hz is just to maintain good sound with smaller speakers, though it does make the subwoofer more easy to localize if you run it that high. The proper setting for this depends on the capability of your speakers as well as how your room interacts with them. Fortunately, your Denon's Audyssey setup should do a good job of detecting a good system crossover if done properly (i.e. with the mic on a tripod at the main listening position for the first position of detection, at ear level with the mic slightly above your seating's headrests).

And since we're reviving this long dead thread, I disagree with people who say there's little above 80Hz in the LFE channel of surround mixes. Many surround tracks have significant energy above 80Hz in the LFE channel, even if only the harmonics for the sub-80Hz material (Sorry, Ed! Don't make me chart some discs digitally like I did DVE!). Though the bass above 80Hz may not be as important as far as the goal of producing low frequency effects, the harmonics above 80Hz do affect the perceived tone of material placed in the LFE channel. My Onkyo 705 lets you independently adjust the LFE cutoff separately from the individual speaker crossovers. The default is the THX conceit of 80Hz. I've found that there is a definite though subtle difference by running the LFE cutoff at 120Hz, though I'm crossing my individual channels over at lower points than that.

A good example is the opening scene of the first Lord Of The Rings movie, where Sauron is killed. There's a bass sweep that happens. I can change between 80 and 120 for the LFE cutoff and it makes a very obvious difference in the way that bass sweep sounds. My system consists of a SVS 20-39CS+ running through a Samson 1,000w amp, with RTi70 mains (60Hz crossover on the Onkyo), CSi40 center (70Hz crossover) and RTi28 surrounds (80Hz crossover).

Thank you very much for your reply Kuntasensei.

I do not know whom to follow since some experts say one thing while the others say another. I have my bookshelf speakers, center, and surrounds crossed to 80Hz which is pretty good sounding. But setting the LFE to 120Hz is just way too boomy for me. I have an SVS 25-31PCI tuned to 20Hz. I do notice the higher frequency in LFE tracks 80Hz and above but they kinda hurt my ears. The blend between the mains and the sub isn't very smooth. My room is very very small. Around 12 square meters (approx. 130 sq.foot). I still feel something isn't right. All parameters were checked such as DRC, midnight mode, attenuation, cinema eq, etc.

Anyways, thanks for your input. Just getting confused by so many opinions.

kuntasensei

Again, you're not setting the LFE. You're setting the crossover for redirected bass going to the subwoofer. Denons don't have an LFE cutoff setting, and I believe the newer models all properly pass the LFE channel unfiltered regardless of the global crossover (unlike the issues stated here).

1) What speakers are you using? That will help you decide what crossover to use, though the Denon default of 80Hz is probably going to be a good starting point. Better to keep directionality down and lose a bit of the harmonics from the LFE channel than send too much to the sub.

2) Have you done a full 8-position run through with Audyssey using a tripod? If you're having issues with your ears hurting, it's usually due to mid-range to high frequencies more than low frequencies. Audyssey can help tame any acoustic issues in your room that may be aiding in hurting your ears. It will also carefully adjust speaker distance/delay settings so that the speakers blend well into the sub (because the distance control effectively acts as a phase control - Audyssey measures acoustic distance, including any delay in the signal chain, so its detected distance may differ from actual physical distance).

So we don't keep thread-drifting, shoot me a PM and I can help you sort out some of your issues.