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....

[a_mattison]

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]

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

[a_mattison]

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]

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]

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]

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]

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 (http://ubb.outlawaudio.com/cgi-bin/ubb/ultimatebb.cgi?/ubb/get_topic/f/34/t/001300/p/1.html#000013)

Sorry if I mislead anyone about the 990.

[McLoki]

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 (http://ubb.outlawaudio.com/cgi-bin/ubb/ultimatebb.cgi?/ubb/get_topic/f/34/t/001300/p/1.html#000013)

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]

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.

[Lancito]

Sorry, I just do not know how to send a PM at the moment.

I appreciate your help kuntasensei.

1. I'm using Monitor Audio BR2 for my fronts, Monitor Audio BRLCR for the center, and Wharfedale 9.DFS for my rears. SVS 25-31PCI tuned to 20Hz for my subwoofer. My system is pretty much very simple especially with the room size limitation that I have.

Could you be kind enough to let me know at which crossover points you would set my system if you were in my shoes?

2. I have done a full 8 position run through Audyssey using a tripod. It detected my fronts and center as full range but I set it to small with 80Hz XO. The rears were detected small and were set to 60Hz which I manually adjusted to 80Hz as well. I only have a choice of 60Hz, 80Hz, 90Hz, 100Hz, etc. No 70Hz.

My subs is tucked in a corner...literally tucked in. It is only about an inch or 1 1/2 inches from the adjoining walls made of concrete. No space to move the sub around. The Xover disabled from sub amp and set to 80Hz which used to be 120Hz but too boomy.

I hope to receive your inputs and I will run Audyssey again while waiting for your reply.

Thanks buddy.

[Eric Wong]

This was part of the rationale behind the original "polk" wiring method using the speaker level outputs to feed the powered subwoofer and disabling the LFE output (subwoofer = no) and main front speakers to large. When the subwoofer was set to "no" the LFE channel was summed into the main channels, so you won't miss any of the LFE track.

On my personal system I do bass management in an unconventional manner. I use an external crossover set at 62 Hz, 24 dB/octave high and low pass Linkwitz Riley configuration between the preamp's front L and R out and the main amps to feed the subwoofer. The subwoofer output is disabled on the preamp to redirect the LFE channel to the front L and R, then the external crossover does the filtering. IMO when setting the preamp processor's "small" setting on the main speakers, I didn't like the rather shallow 12 dB/octave high pass filter.

[kuntasensei]

Lancito, I have a general rule'o'thumb when setting system crossovers. Because of the gradual transition (the slope that Eric is talking about above), I like to start with a crossover setting about a half octave above the speaker's lower -3dB point and see how it sounds. Basically, take the -3dB point in the speaker's specs and multiply by 1.5. I've had good luck with that rule thus far because speakers usually extend slightly lower than their anechoic specs when they're actually in your room. The exception to this rule is that regardless of what you get with that formula, you want to avoid setting any speaker over 100Hz crossover if you can help it. You don't want to sacrifice directionality.

With your BR2s, you get extension down into the 40s. Accordingly, 60Hz would be a good crossover point for that speaker. The center channel, however, hits -3dB at 60Hz, making a 90Hz crossover seem ideal by the above rule. However, you definitely want to keep mid-bass in the center for deep voices, so I'd stick with 80Hz for center. The Wharfedales are small driver speakers, and the specs use a -6dB point of 70Hz, which makes things interesting. For a good transition, I'd normally say go 100Hz with those because bass directionality is slightly less important in the surrounds, but I think 90Hz might work better for those speakers. You might even get away with 80Hz since Audyssey's detecting 60Hz for the in-room response.

If you can set each channel separately, I'd go 60Hz mains, 80Hz center, and 90Hz surrounds to make sure you don't lose any bass to any speaker's natural rolloff. The important thing is that you never set a crossover LOWER than what Audyssey detected, because Audyssey only EQs down to its detected -3dB point.

As far as your subwoofer placement, putting it that close to the wall presents its own acoustic problems. You normally want to give a sub at least 2-3" space from the wall, even when corner loading. The normal issue for people with drywall is that placing the subwoofer too close to a wall can make the wall surface effectively act as a passive radiator (especially with rear-ported subs - not the case with your downfiring SVS). With concrete walls, you have a whole other issue - slap reflections off the wall surfaces. If you could get away with it aesthetically, you might consider some sort of acoustic treatment behind the subwoofer to tame the harshness of reflections off of the concrete. If you can't, Audyssey should help mitigate the effects, though it's not ideal.

Make sure you have the crossover on the SVS turned to its maximum or bypassed if possible. Active crossovers can induce delay that will throw off Audyssey's distance detection.

When running Audyssey, make sure that none of the 8 positions fall too far outside of the front soundstage. For instance, don't place the mic past the left or right main when doing your mic placements. Envision about a 45 degree cone of sound coming from each speaker and make your mic placements so that the mic is within the cone of each of the front three speakers at all times. If your left and right listening positions don't fall within that general visual guideline, consider angling your mains inward slightly so the entire listening position falls within those imaginary cones.

Position 1 should always be the main listening position, centered up with the center channel. Raise the tripod up so the capsule on the end of the mic clears the headrest of your seating by about an inch to prevent the absorption of your seating from affecting the equalization. Position 2 should be several feet to right of center while facing forward. Position 3 should be several feet to left of center while facing forward. For positions 4-6, mirror positions 1-3 about 2 feet further into the room, IN FRONT OF YOUR COUCH.

The idea with Audyssey is to not only give it a reading of the acoustics at the seats, but also to give it a reading further into the room away from room boundaries so it can assess how the room affects low frequencies. For positions 7 and 8, place the mic somewhere in the middle of the rectangle formed by positions 1-6. I use this pattern:

6-4-5 <-- 2 ft. in front of 1-3.
-7-8- <-- Tripod placed against front edge of couch.
3-1-2 <-- On couch.

[Lancito]

I appreciate your help, kuntasensei. I will run Audyssey again per the mic positions you recommended above. Also, I will set the XO 1.5 times its rated +/-3db points. As for the LFE, iL try setting it to 100Hz and see if it blends well with my mains.

I definitely learned a lot from a very helpful Polk member probably from the other side
of the globe.

Best regards.

[joe.inom]

Actually you see , i have never dealt with these stuffs cause long before my big brother had his settings done , and what i did was changed it to my style and finally burned teh tweeters , thus you see it is better to keep the stuffs in default.