If a subwoofer's frequency response is 28Hz on the low end, what does it really get to? - AVS Forum
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post #1 of 92 Old 01-19-2013, 04:10 PM - Thread Starter
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If a subwoofer says it goes down to 28Hz, does is it really go down to that level? Does that deteriorate over time, if the driver is in good shape?

edit: is that low end all marketing?

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post #2 of 92 Old 01-19-2013, 05:57 PM
 
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Our eighteen year old ported (with radiator) sub was spec'd at 28Hz and pretty much, that was all it was good for and then it dropped like a stone. It would play lower but the more energy that was applied, the flappier the woofer got. Don't recall flappy and subwoofer being used together being a good thing. tongue.gif

Recently, I replaced the driver and radiator in both boxes and currently, we're going through a fifty hour break in period to loosen the new drivers up a bit. Once the break-in period is over, I'll dial things in using a sound meter, DSPeaker, Anti-Mode, 8033S II and Audyssey, MultEQ XT. From there I'll be able to do some measured room sweeps with REW and compare the differences.

Here's a graph of the old dialed in woofers being used at the same time. The sweep parameters were set to: 15Hz - 200Hz. Both subs are spec'd for 28Hz - 120Hz. The dip on the left is expected for a ported sub using a radiator. Don't know why but that's what I read.

If the new drivers and radiators don't correct the null on the right, I'll either have to accept it or hope placing an acoustic panel in the one location I have behind the null position will correct the problem. Currently, all speakers are crossed over at 60Hz, so the rest of the speakers will help with filling in the hole.

Hope the above helps with your question.

Graph of our 28Hz to 120Hz subwoofers:



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post #3 of 92 Old 01-19-2013, 06:23 PM
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If a subwoofer says it goes down to 28Hz, does is it really go down to that level?
If a subwoofer says it goes down to 28Hz, then it really goes down to that frequency, and very likely even lower. A couple of qualifiers:
- If the variance is -3dB, then SPL at 28Hz is still useful/usable. The greater the variance, the less useful/usable the output. (DefTech, for example, lists very ambitious extension figures with no variance. It is highly unlikely their subs extend down to anywhere near the rated frequencies.)
- The variance is usually stated at a test level of output. As output increases, the range within which the sub will play at +/-3dB (and the lowest frequency it will play at -3dB) may change.
- A sub's in-room response may differ anywhere from minimally to significantly compared to its measured response (usually ground-plane).
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Does that deteriorate over time, if the driver is in good shape?
It shouldn't, or not significantly.
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post #4 of 92 Old 01-19-2013, 06:37 PM
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Originally Posted by BeeMan458 View Post

Our eighteen year old ported (with radiator) sub was spec'd at 28Hz and pretty much, that was all it was good for and then it dropped like a stone. It would play lower but the more energy that was applied, the flappier the woofer got. Don't recall flappy and subwoofer being used together being a good thing. tongue.gif

Recently, I replaced the driver and radiator in both boxes and currently, we're going through a fifty hour break in period to loosen the new drivers up a bit. Once the break-in period is over, I'll dial things in using a sound meter, DSPeaker, Anti-Mode, 8033S II and Audyssey, MultEQ XT. From there I'll be able to do some measured room sweeps with REW and compare the differences.

Here's a graph of the old dialed in woofers being used at the same time. The sweep parameters were set to: 15Hz - 200Hz. Both subs are spec'd for 28Hz - 120Hz. The dip on the left is expected for a ported sub using a radiator. Don't know why but that's what I read.

If the new drivers and radiators don't correct the null on the right, I'll either have to accept it or hope placing an acoustic panel in the one location I have behind the null position will correct the problem. Currently, all speakers are crossed over at 60Hz, so the rest of the speakers will help with filling in the hole.

Hope the above helps with your question.

Graph of our 28Hz to 120Hz subwoofers:



-

If you're using a 60 Hz crossover, who cares about a null at 90 Hz in the subwoofer output?

The null at 90 Hz is NOT caused by the subwoofer. It is room induced, not driver induced.... but I'll ask again... if you're using a 60 Hz crossover, who cares about a 90 Hz, room induced null from the subwoofer?

Measuring the in-room response of a sub tells you a lot... about the room... not so much about the subwoofer. If you want to learn about the baseline response of the subwoofer, you need to take it outdoors where the room has no impact on the response. You have referenced the Data-Bass measurements in other threads. Their measurements are all performed outdoors, groundplane. That is the only set of measurements that can tell you anything about the performance of the subwoofer itself. Once you know the baseline performance of the sub, you can then place it in your room and measure it at your listening position and see what the room does to it.

But again, if it is LPF'd, (crossed over), at 60 Hz and the speakers are generating the energy at 90 Hz, why would you care about a room induced null at 90 Hz on the subwoofer output?
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Originally Posted by likemovies View Post

If a subwoofer says it goes down to 28Hz, does is it really go down to that level? Does that deteriorate over time, if the driver is in good shape?

Does the sub in question also specify a -3 dB point? If that is 28 Hz, then the sub will have useable, audible output to 28 Hz. If it doesn't specify a -3 dB point, then there is no knowing how low it actually extends without good measurements. What sub is this?
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Originally Posted by likemovies View Post

edit: is that low end all marketing?
IMO, absolutely NOT! Deeper extension is always better. My system will do 10 Hz without strain. You'll need to spend some $$$ to get that kind of extension, but It is very noticeable and worthwhile when the content contains that kind of extension.

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post #5 of 92 Old 01-19-2013, 06:53 PM
 
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LFE, THX Reference, 0.1 channel information, 20Hz - 120Hz. (nuff said)
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post #6 of 92 Old 01-19-2013, 07:09 PM
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Originally Posted by BeeMan458 View Post

LFE, THX Reference, 0.1 channel information, 20Hz - 120Hz. (nuff said)
There is very little content in the LFE channel above 80 Hz. Nuff said.

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post #7 of 92 Old 01-19-2013, 07:17 PM
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Originally Posted by BeeMan458 View Post

LFE, THX Reference, 0.1 channel information, 20Hz - 120Hz. (nuff said)

Lots of ~20hz content. Nuff said.
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Originally Posted by sputter1 View Post

Lots of ~20hz content. Nuff said.

And the above has what to do with an ~90Hz null and content encoded above 80Hz in the LFE channel? ...confused.gif
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post #9 of 92 Old 01-19-2013, 07:24 PM
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Originally Posted by BeeMan458 View Post

Quote:
Originally Posted by sputter1 View Post

Lots of ~20hz content. Nuff said.

And the above has what to do with an ~90Hz null and content encoded above 80Hz in the LFE channel? ...confused.gif

That's your response? lol nvm then.
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post #10 of 92 Old 01-19-2013, 07:28 PM
 
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Originally Posted by sputter1 View Post

That's your response? lol nvm then.

What's to say? Your comment followed an exchange regarding a 90Hz null and according to one, the apparent uselessness of reproducing >80Hz material in a channel spec'd for up to 120Hz. If a sub is not spec'd for <28Hz, and 20Hz is outside it's useful reproduction range, then what's to say?
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post #11 of 92 Old 01-19-2013, 07:36 PM
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Originally Posted by likemovies View Post

If a subwoofer says it goes down to 28Hz, does is it really go down to that level?
Unless you see a measured SPL chart you have no way of knowing. IME there are only two reasons for a chart not being posted: they don't have one, or they don't want you to see it.

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post #12 of 92 Old 01-19-2013, 07:43 PM
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Originally Posted by BeeMan458 View Post

LFE, THX Reference, 0.1 channel information, 20Hz - 120Hz. (nuff said)
To be more exact, with DD and DTS, the LFE channel is "specified" to be 3 Hz to 120 Hz. With the lossless codec's, Dolby TrueHD and DTS MA, the LFE channel is a full range channel specified as 3 Hz to 20 kHz.

Still, there is very little content in the LFE channel above 80 Hz in any of those codec's. Recording engineers just don't put that content there.

Bottom line, if you want to concern yourself with a null at 90 Hz from the subs, changing drivers and PR's is the wrong approach. I can guarantee you that the null is not in the baseline response of the subs. It is induced by the room. Instead, try moving the subs and/or the listening/measuring position. Otherwise, just don't worry about it. It simply doesn't make much difference if you're using a 60 Hz crossover on your speakers. There will be very little 90 Hz content sent to the subs anyway.

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post #13 of 92 Old 01-20-2013, 08:02 AM
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Quote:
Originally Posted by craig john View Post

Quote:
Originally Posted by BeeMan458 View Post

LFE, THX Reference, 0.1 channel information, 20Hz - 120Hz. (nuff said)
To be more exact, with DD and DTS, the LFE channel is "specified" to be 3 Hz to 120 Hz. With the lossless codec's, Dolby TrueHD and DTS MA, the LFE channel is a full range channel specified as 3 Hz to 20 kHz.

Still, there is very little content in the LFE channel above 80 Hz in any of those codec's. Recording engineers just don't put that content there.



Craig


Most of the time there is plenty of content recorded on the LFE channel that goes up to 120 Hz.
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Originally Posted by J_Palmer_Cass View Post

Most of the time there is plenty of content recorded on the LFE channel that goes up to 120 Hz.
Not according to Rodger Dressler. He's so convinced of this that he sets his LPF of LFE at 80 Hz.

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post #15 of 92 Old 01-20-2013, 08:41 AM
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Originally Posted by craig john View Post

Not according to Rodger Dressler. He's so convinced of this that he sets his LPF of LFE at 80 Hz.

Craig

That I don't understand. Isn't it true that regardless of whether content is mastered up to 60, 80, or 120 Hz on the LFE channel, anything you don't allow from that channel to play on the sub is just lost? This is not like the crossover points for the other speakers, where content below it is not tossed but is redirected.

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I distinctly recall stating THX reference (standards), not DD or DTS with any mention of CODEC's.

If the boss (THX) says up to 120Hz, what do I care and it sounds like those who LPF their subs at 80Hz are being ego bound (stubborn) as opposed to being flexible as 80Hz or 120Hz, what does it matter if the LFE channel (the subwoofer) is set to 120Hz? Sounds more like Rodger is digging in his heels to support his "personal" thesis as opposed to trying to get along with THX reference standards.

As to the null, I know it's the subs interacting with the room's acoustics, so stop going there. Some have reported that simply changing subs in the same location has cured their null so there's a bit more to the whole, sub, room, interaction thingy than some are willing to deal with. In the meantime, once the new drivers are "BROKEN IN," I'll do some room sweeps, dial things in and have my wife stand around with a big thick love seat pillow (yes, furniture seating cushions do have absorptive properties) and see what REW has to report back.

Some like to discourage and say don't bother going there because I know everything. Others like to encourage and say, here are the facts as I understand them so what the heck, it's all good; have a good time with your journey.

(And for the record, I'm not trying to reinvent the wheel. I'm busy learning about the wheel being used.)

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post #17 of 92 Old 01-20-2013, 09:38 AM
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Quote:
Originally Posted by craig john 
Quote:
Originally Posted by J_Palmer_Cass 
Most of the time there is plenty of content recorded on the LFE channel that goes up to 120 Hz.
Not according to Rodger Dressler. He's so convinced of this that he sets his LPF of LFE at 80 Hz.
Perhaps things have changed since 2000, but according to this article:
Quote:
Dolby Digital's LFE channel carries additional bass information from 120 Hz on down. This is not a roll-off but a digital brick wall (i.e., no 121 Hz info), so the content is usually rolled off by the sound engineer starting around 80 Hz for a smoother blend.
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post #18 of 92 Old 01-20-2013, 09:51 AM
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Originally Posted by BeeMan458 View Post

I distinctly recall stating THX reference (standards), not DD or DTS with any mention of CODEC's.

If the boss (THX) says up to 120Hz, what do I care and it sounds like those who LPF their subs at 80Hz are being ego bound (stubborn) as opposed to being flexible as 80Hz or 120Hz, what does it matter if the LFE channel (the subwoofer) is set to 120Hz? Sounds more like Rodger is digging in his heels to support his "personal" thesis as opposed to trying to get along with THX reference standards.

As to the null, I know it's the subs interacting with the room's acoustics, so stop going there. Some have reported that simply changing subs in the same location has cured their null so there's a bit more to the whole, sub, room, interaction thingy than some are willing to deal with. In the meantime, once the new drivers are "BROKEN IN," I'll do some room sweeps, dial things in and have my wife stand around with a big thick love seat pillow (yes, furniture seating cushions do have absorptive properties) and see what REW has to report back.

Some like to discourage and say don't bother going there because I know everything. Others like to encourage and say, here are the facts as I understand them so what the heck, it's all good; have a good time with your journey.

(And for the record, I'm not trying to reinvent the wheel. I'm busy learning about the wheel being used.)

-

Two members with far more knowledge than you (or I) provided information on this topic and your response is to denigrate them? And suggest some personal agenda trumps their honesty? The two members have a lot of credibility on AVS, credibility they have earned over the years.

Then post that you expect randomly changing a subs drivers will address a room null and that any kind of measurements taken while someone holds a pillow have value.

I think I'll side with Craig and Rodger on this one.
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I think I'll side with Craig and Rodger on this one.

Even though that's not what I did, I support your decision to do so.
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So if my XO for my fronts are set to 110hz it would be wise to just leave the LPF at 120hz on the sub right?

No subwoofer I've heard has been able to produce the bass I've experienced in the Corps!

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post #21 of 92 Old 01-20-2013, 03:24 PM
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So if my XO for my fronts are set to 110hz it would be wise to just leave the LPF at 120hz on the sub right?

Yes
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post #22 of 92 Old 01-20-2013, 03:48 PM
 
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So if my XO for my fronts are set to 110hz it would be wise to just leave the LPF at 120hz on the sub right?

Yes. To change that setting will short change the LFE recorded material. Because of there being little content in the >80Hz part of the LFE channel, others will argue that it's okay to do so. But for the life of me, there's no sense doing that for if a standard is 3Hz -120Hz (THX = 20Hz - 120Hz), then without argument, go with the standard. Otherwise, what's the purpose of having a stated standard?

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Movies, music and games are featuring more deep bass elements than ever before. To accurately recreate the roar of the jet engine or the sound of a freeway bridge collapsing, THX certification requires bass from all channels, including LFE, be redirected to the subwoofer. For this reason, THX Certified Subwoofers must extend to 20Hz (-6dB) to handle the very highest bass levels with ease.

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post #23 of 92 Old 01-20-2013, 03:59 PM
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Not trying to be argumentative here but why would you guys want to set the LPF on the sub to 80hz? I know you are saying that there is barely any >80hz content in the lfe channel but what if there is on certain mixes? Is there a benefit to setting the lpf to 80hz? It's like saying there is some sub 20hz content in mixes but since there's not a lot than all those crazy people trying to get flat to 10hz are...well just crazy lol. Might as well just set an hpf at 20hz?

Like I said, not trying to be argumentative. Just want to see what is the pros of setting the lpf to 80hz

No subwoofer I've heard has been able to produce the bass I've experienced in the Corps!

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Originally Posted by pokekevin View Post

Not trying to be argumentative here but why would you guys want to set the LPF on the sub to 80hz? I know you are saying that there is barely any >80hz content in the lfe channel but what if there is on certain mixes? Is there a benefit to setting the lpf to 80hz? It's like saying there is some sub 20hz content in mixes but since there's not a lot than all those crazy people trying to get flat to 10hz are...well just crazy lol. Might as well just set an hpf at 20hz?

Like I said, not trying to be argumentative. Just want to see what is the pros of setting the lpf to 80hz

Here's what I found on the matter, it has to do with localization. A problem exists. Our ability to locate sound, drops off after 80Hz and there's no placement standard for subwoofers. So if content above 80Hz is played through randomly placed subwoofers, the sound or mix engineer has no way of knowing where the sub is going be located yet the standard for the LFE channel goes up to 120Hz. Hence the conflict. So in the end, some engineers do, some engineers don't, yes it can be pot luck and that's what I found.

In the final, if a subwoofer LPF is set to 120Hz and the Home Theater owner's >5.1 system is being played at close to THX reference (-15dB - +/- 0dB volume setting), personally, unless the recorded information is of an obtuse sound quality, with all the overlapping sound fields, I doubt anyone is going notice the >80Hz directional nature of recorded material being reproduced through a subwoofer such as the lingering sonic decay of an explosion.

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post #25 of 92 Old 01-20-2013, 05:44 PM
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Ok, back to the original question:

I know lots of subs say the low end +/- 3dB anechoic (eg: 28Hz +/- 3 dB). I thought, however, that the room can enhance the lower end so that the extension can go flat significantly below the specified low end. Thus lots of people with sealed subs claim extension flat into the teens despite the sub having a likely above 20Hz low end. All of this depends upon the room and where the sub is placed in the room, of course. Correct me if I'm wrong.
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post #26 of 92 Old 01-20-2013, 07:02 PM
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Quote:
Originally Posted by BeeMan458 View Post

I distinctly recall stating THX reference (standards), not DD or DTS with any mention of CODEC's.

If the boss (THX) says up to 120Hz,...
THX??? What makes you think THX is the "boss" of the LPF of LFE? THX neither specifies the inclusion of an LPF of LFE, nor do they make a recommendation on the setting. The only LPF THX specifies is the LPF of the subwoofer crossover, where they specify an 80 Hz crossover frequency, a 4th order roll-off on the LPF of the subwoofer, as well as a 2nd order roll off on the HPF of the speakers. Nonetheless, these have nothing to do with the LPF of LFE, or with THX.

The LPF of LFE is a Dolby requirement, not a THX requirement. Dolby started requiring a LPF of LFE in their decoders when they stopped brickwall filtering of the LFE channel at 120 Hz on encoding. That happened when Dolby introduced TrueHD and the other lossless codecs. The LFE channel became a full range, 3 Hz to 20 kHz, channel. Since it was no longer filtered on encoding/recording, the filtering had to be instituted on decoding/playback. The playback filter is not a brickwall filter, so a lower setting can be more effective. Take a look at this graph:


(originally posted by Roger Dressler)

There is significantly more higher frequency energy above 120 Hz allowed to pass by a 120 Hz LPF than an 80 Hz LPF. Nonetheless, this has NOTHING to do with THX.

Quote:
Originally Posted by BeeMan458 View Post

...what do I care and it sounds like those who LPF their subs at 80Hz are being ego bound (stubborn) as opposed to being flexible as 80Hz or 120Hz, what does it matter if the LFE channel (the subwoofer) is set to 120Hz? Sounds more like Rodger is digging in his heels to support his "personal" thesis as opposed to trying to get along with THX reference standards.

confused.gif Roger Dressler's "personal thesis"??? Do you mean THIS Roger Dressler who:
Quote:
"Helped Dolby launch its first Dolby Surround technology, and every one since, including Pro Logic, Surround EX, PLII, PLIIx, Dolby Digital, DD+, Meridian Lossless, TrueHD."

Roger Dressler's "personal thesis" would have been developed in his position as the Director of Technology Strategy for Dolby Labs for 26 years, (now retired), http://www.linkedin.com/pub/roger-dressler/b/879/336 If you mean THAT Roger Dressler, then yeah, I'll accept his "personal thesis" that the LPF of LFE should be set to 80 Hz. I've been doing that in my system for a long time.

Then there is what Mark Seaton had to say:
Quote:
I think many have a gross misconception as to the real difference between a 120Hz vs. 80Hz low pass. Personally I always have found I prefer an 80Hz setting. This isn't the difference of having a low pass or not having one. This is just setting the filter lower. If instead we look at the difference between a 120Hz vs. 80Hz low pass, we see it is in fact a shelf filter. Assuming a 4th order filter, moving to 80Hz has no real effect below 40Hz, reduces the 80Hz level by ~4dB, 100Hz by ~7dB, 120Hz by ~9dB and ultimately reaches -14dB somewhere above 200Hz. If the low pass filter is 2nd order, cut those differences in half.

If you have your subwoofers rising to say 3-6dB above the main speakers, the lower crossover point would have the 80-100Hz range pretty much in line with a flat calibration and a smooth rise below there, which many like the sound of.

In addition, FilmMixer, (Mark Fischman) http://www.imdb.com/name/nm0279892/ has stated that he always filters the LFE channel at 80 Hz, as do many other recording engineers. I can't find that quote right now, but you can ask him.... he's a member of the forum.

So... there ^^^ you have 3 real experts recommending an 80 Hz LPF of LFE, and THX, making NO recommendation whatsoever.

Edit: While I was looking for the above quotes, I see that you were also looking. You found the localization issue, and that is good information. The graph I posted above shows why it is important to reduce the content above 80 - 120 Hz to reduce localization. In addition, realize that any info above 80 Hz in the LFE channel will also be replicated in the main channels. Playing it back through BOTH the speakers and sub(s) will accentuate that content and make it sound overly prominent, and boomy, muddy or inarticulate.

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post #27 of 92 Old 01-20-2013, 07:22 PM
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Quote:
Originally Posted by beezar View Post

Ok, back to the original question:

I know lots of subs say the low end +/- 3dB anechoic (eg: 28Hz +/- 3 dB). I thought, however, that the room can enhance the lower end so that the extension can go flat significantly below the specified low end. Thus lots of people with sealed subs claim extension flat into the teens despite the sub having a likely above 20Hz low end. All of this depends upon the room and where the sub is placed in the room, of course. Correct me if I'm wrong.
Once the wavelength of a soundwave exceeds the dimensions of the room, there is no more "modal" response. The response below this point transitions to "pressure vessel gain" or PVG.

From a post by FOH in the the "Acoustical Treatments Master Thread":
Quote:
Typically, I'm more clear (read verbose) with regard to PVG, like I did in this excerpted post;

"Pressure Vessel Gain (PVG), or room gain, is the scenario whereby the longest dimension of the room can no longer support full propagation of the waveform. At this point, the acoustic propagation transitions to acoustic pressurization. A typical myth is a small cabin cannot support the lowest frequencies.... nothing could be further from the truth. The manner in which the sound is reproduced into the space changes from a normal cyclic propagation, to pressurization because the wavelengths are too big for the space. The frequency at which this occurs is approximately the point whereby half the wavelength of a given frequency is equal to the rooms longest dimension. So, a 20 hz frequency has a wavelength 56.5 feet. So half of that, 28.25 feet, is the point of transition. Any frequency below that point pressurizes the room, and any frequency above that point propagates freely. So in this room that's approximately 28 feet in the longest dimension, from 20 hz downward, the room gives back acoustically. This is room gain, cabin gain, or more specifically PVG...Pressure Vessel Gain.

At this frequency, the results are a gain in acoustic pressures in the room that grows as the frequency decreases. This acoustic support reciprocity, is theoretically 12db per octave. The percentage of the 12 db/octave gain one achieves, entirely depends on the integrity of the boundary walls and surfaces. If it was the theoretical concrete bunker, a full 12db/octave boost would occur. Typically, somewhere between 6-10 db octave could result. Also, in addition to the walls and surfaces flexing, other aspects may affect the point at which room gain begins. Furniture, cabinets etc, anything that consumes a certain measure of cubic feet, may slightly alter the transition frequency merely because the items take up space.

This acoustic pressurization, room gain, is the proverbial free lunch. It is essentially headroom that's thrown back into the system. And unlike horn subs, the distortions and non-linearities are not magnified. An IB sub system is a sealed alignment. Sealed alignments roll off second order. Room gain also is second order. So one can see how integrating a sealed alignment may offer substantial benefit when attempting to integrate the system to the room via time and frequency equalization. The -3db point of the IB, may typically be deeper than the transition point where room gain begins. Properly adjusted, this would result in substantial headroom added back in for significant capability for the big LFE effects."

IOW, the slower roll-off of a sealed alignment can combine with the inherent PVG of a room and add to the SPL's below the modal response. A vented sub will roll off to quickly to take advantage of this property. Of course, a sealed alignment will have less output to begin with, so it will need more augmentation by the room. However, adding more sealed subs can provide massive output at these low frequencies, where a vented sub will not add much below its' tune frequency in spite of the room gain, (PVG) it sees.

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post #28 of 92 Old 01-20-2013, 09:07 PM
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Hmmm...makes me wish I could set my XO to 80hz so I could set the LPF to 80hz... Audyssey keeps setting it to 110 for my room. Blah

No subwoofer I've heard has been able to produce the bass I've experienced in the Corps!

Must..stop...buying...every bluray release...
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Originally Posted by BeeMan458 View Post

First things first, there was no mention of LPF'g the LFE channel as the THX reference standard is set, my understanding, to a max of 120Hz.
I don't know how to make this more clear. THX doesn't specify the bandwidth of the LFE Channel, and they don't have a standard for the LOW PASS FILTER of the LOW FREQUENCY EFFECTS CHANNEL, (AKA the LPF of LFE.) THX doesn't specify a 120 Hz setting of the LPF of LFE. Nor do they specify 80 Hz or 200 Hz or any Hz. THX doesn't specify ANYTHING having to do with the LPF of LFE.

The only "LPF" that THX specifies is the one in the THX crossover, and that is set at 80 Hz and 4th order, per THX specifications. The LPF in the THX crossover is only applied to the re-directed bass bass from the main channels that have crossovers set. That is completely separate from the LFE channel. The LPF of LFE is only applied to the LFE Channel. You need to understand this fundamental difference before we can proceed with the conversation.

This is just like your description of an SPL meter as an "EQ Device". Just because an SPL meter can be used to set the levels of the speakers to be "equal" doesn't make the SPL meter an "EQ Device" as you claimed in another thread. You use the terminology incorrectly and expect the rest of us to understand what you mean.
Quote:
Originally Posted by BeeMan458 View Post

The only thing I'm doing with the LPF on the sub, is making sure it mirrors the THX standard. Anybody is welcome to characterize what I'm doing in in fashion they wish but I'm going with my descriptors.
Again, therein lies the problem. If you want to "communicate" with us, we all need to have standard definitions of the terms and descriptions. You can't have your own definitions and expect everyone else to conform to them. You won't understand us and we won't understand you. There will be no effective communication. Either conform to the standard definition of terms or go start your own forum where you can be the definer of the terms.

Edit... Wait, I just realized something. You said, "The only thing I'm doing with the LPF on the sub..." If you are talking about the LPF on your subwoofer, that is NOT the LPF of LFE. If you have an older receiver, you may not even have an LPF of LFE. That may be the whole communication problem. The LPF of LFE that I'm addressing is built into the receiver or pre/pro and is part of the Dolby or DTS decoder. The LPF on your subwoofer is something else entirely. The LPF on your sub is an internal low pass. If you are using the Bass Management in your receiver, you should bypass the LPF on your sub, or turn it up to it's highest point so it doesn't interfere with the filters in the Bass Management of your receiver.

Still, either way, THX doesn't specify any of this.
Quote:
Originally Posted by BeeMan458 View Post

As to other standards running up to 20kHz, considering the frequency range or capability of a subwoofer driver, isn't it a safe bet that any standard far exceeding a driver's capability, is being grossly ridiculous?
It's "defined" as a full range channel in the Dolby specifications for TrueHD. Get over it. You don't get to define what that means. Dolby has already done that for you.

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post #30 of 92 Old 01-20-2013, 09:17 PM
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Quote:
Originally Posted by pokekevin View Post

Hmmm...makes me wish I could set my XO to 80hz so I could set the LPF to 80hz... Audyssey keeps setting it to 110 for my room. Blah
If you're not localizing your sub, I wouldn't worry too much about it. If you are localizing the sub, there may be somethings you can do to to affect the crossover frequency set by Audyssey. What speakers and sub do you have?

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