Author Topic: Subwoofer discusion thread - suggestions, tips and info  (Read 49531 times)

Offline lwm99

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #15 on: August 05, 2008, 21:19 »
For the guy with the Ascend Sierra-1 asking for advice, you may want to check this thread where the person shared his experience in setting up his HT with Sierra-1 and other subwoofers. He stack up his Sierra-1 speakers and subwoofers to get the effect he wants.
http://forum.ascendacoustics.com/showthread.php?t=3350

He has recently changed his subwoofers to 4 (or 8?) Hsu ULS-15. If you are interested, you can read up more about his setup in AVS.

Offline CiakSaiOng

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #16 on: August 07, 2008, 12:00 »
 its impossible for me to find that much money hehehe.. but thanx alot for your suggestion and help.. will certainly read the link u provided
« Last Edit: August 07, 2008, 12:02 by CiakSaiOng »

Offline petetherock

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Bass Management and the LFE Channel
« Reply #17 on: September 13, 2008, 18:48 »
A good read on this:

http://www.ultimateavmag.com/howto/805bass/

Some points:

Quote
Although we would like to have frequency-agile filters, fixed-frequency filters are not all bad. An extensive survey conducted in Europe showed that 80Hz is the best all-around choice for fixed-frequency filters. In the survey, the vast majority of humans began to distinguish subwoofer directionality at a mean frequency of 185 Hz, and 80 Hz was the absolute minimum case below which no one heard directionality. This has led most manufacturers to choose 80 Hz as the frequency for their fixed filters.


Quote
Myths and Confusion
Now that we understand a little bit about bass management, it's time to dispel a few myths and examine common areas of confusion that relate to bass management, the LFE channel, and bass reproduction.

1. Low bass is NOT directional. If I had a penny for every time someone has told me they can hear bass directionality down to 20 Hz, I would be writing this article while flying to the French Riviera in my private jet. Yes, we can hear the overtones of bass instruments above 120 Hz, and those overtones should definitely be played by the main speakers correctly located in the room for proper imaging. However, we cannot-I repeat cannot-localize bass below about 80 Hz.

The most important thing we can do with non-directional bass frequencies is to produce them in locations in a room that don't favor strong coupling with standing-wave resonances. These resonances turn a bass punch into an event that takes two seconds to decay-that's bad, that's mushy, that's slow. Attempting to play stereo bass in a listening room without regard to 2-second-long bass resonances, which completely swamp any sense of separation, is pure madness! Of course, that's only my theory; others can draw their own conclusions. This is largely a free world despite what some may want us to think!

2. Full range speakers are NOT an excuse for eliminating bass management. In order to render bass management unnecessary, each full range speaker must have a 15-inch woofer (or dual 12-inch woofers) with 200 watts of power driving it. Anything smaller will simply overload on loud scenes. Also realize that each one of these behemoth speakers must be carefully placed so its interaction with the bass resonances of the room is optimized. Believe me, it's darned near impossible to place seven speakers in a room so that each speaker identically loads bass resonances. The result of improper loading is grossly uneven bass. Some speakers are cranking out thick and inarticulate bass, while others seem downright anemic.

The right way to handle this dual problem is to implement bass management and strategically place subwoofers in the room for optimized resonance loading. Research has shown that some locations in a room yield predictably good results after all is said, done, and installed. One of the best layouts is four subwoofers in a cross pattern (see Fig. 6).

 

3. The LFE channel is NOT a "subwoofer channel." The LFE signal should be thought of as a path for super-loud bass that would otherwise overload the main channels. Sound designers use this path when the main channels just can't put out enough bass to rock the house. Remember that in movie theaters, the volume control is fixed at a reference level. At that volume setting, the peak sound pressure level from the recorded medium should be 105dB in the listening area. In the mid-frequency range, 105dB is good and loud, but in the deep bass region, it just isn't enough to get the impact we all expect from big A-list titles with he-man characters wielding limitless firepower.

To get real chest-pounding bass, we need to get up to 115dB. The main channels are missing 10dB of headroom, and that's where the LFE channel comes to the rescue. With 10dB of extra headroom, it can really get a person's body bouncing around in the seat. LFE is only used during high-octane action with lots of bass; during the rest of a movie, the LFE channel has no content. The LFE channel may be fed directly to subwoofers in most systems, but there's no directive that it must be. An exceedingly large home theater (dimensions greater than 40 feet) with massive main speakers could theoretically run the LFE channel to those speakers and have no subwoofers at all!

4. There should be ONE, only ONE, and nothing but ONE audio connection between an AV controller and powered subwoofers. Some AV controllers offer an LFE-only output in addition to the subwoofer output, and some subwoofers offer multiple line-level inputs. Controllers with both LFE-only outputs and subwoofer outputs may tempt us to connect a separate subwoofer to each output and run one subwoofer for the LFE channel and another one for summed main-channel bass. This is an exceptionally bad idea in most cases, because we need both subwoofers playing the same thing, working together to cancel bass resonances. The most effective use of two subwoofers is to have them play the sum of the bass from the main channels and the occasional LFE hit. Bass character stays consistent throughout the movie, and the subwoofers are used to their full potential.

This brings us to subwoofers with multiple line-level inputs. The concept of a subwoofer with multiple inputs that have various filtering and summing functions makes no sense in light of our discussion of bass management. In a multichannel audio system with bass management, a subwoofer needs one input, a polarity switch, a power switch, and that's all folks! Those other things-diverse inputs with misleading names, a stereo summing input, a lowpass filter, a volume control, etc.-are only useful in a stereo system without bass management and just add to the cost and complexity of a subwoofer. It is the job of a custom installer or end users to search out the right input for the bass-managed feed from a controller, and that's not always an easy task.
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Offline petetherock

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #18 on: September 13, 2008, 18:48 »
Quote

( I have run into situations in which the gain of the subwoofer is such that the bass level setting in the preamp-processor or AV receiver has inadequate range on its own to properly set the subwoofer level. Because of that, I personally prefer to have a level control on a subwoofer.—TJN)

5. There are NO clear rules governing the bandwidth of the LFE channel. The production statutes applied to LFE channels are so varied that determining the upper LFE cutoff frequency for a playback system is often an exercise in futility. Some LFE channels contain no content above 50Hz, while others (usually due to an error in mastering) are full range! The generally accepted safe approach on the playback end is to lowpass-filter the LFE channel at 80 Hz. However, some AV controllers do not apply a lowpass filter to the LFE channel at all, meaning that highly directional bass on some recordings could potentially be produced by the subwoofers. Beware of these controllers, as there is usually no way to add an external lowpass filter without serious repercussions to the main-channel bass.

6. The ratio of the LFE level relative to the level of the bass from main channels should NOT be adjusted in the AV controller. The ratio should be such that LFE signals are 10dB louder than signals of equivalent level in any other channel. A few early DTS music releases contained LFE channels that were 10dB louder than the industry standard. For this reason, some controllers include a DTS music mode that reduces the LFE channel by 10dB. There is no other logical reason to adjust the level of the LFE channel separately from the main channel bass. Doing so irreparably alters the mix intended by the sound engineer.

7. There is NO NEED for an LFE channel in the vast majority of music applications. There continue to be multichannel music recordings released with content in the LFE channel when the bass in the main channels isn't even close to overload. Inexplicably, some music-recording engineers think that they must put something into the LFE channel so that end users will hear sound coming from their subwoofers.

Frankly, that's terrible logic because the subwoofers in bass-managed systems (which represent the overwhelming majority) receive the LFE channel and the sum of the main-channel bass. Users and installers of multichannel systems don't really need to worry about a music recording with an LFE channel as long as they set up their systems correctly with bass management. At times, however, bass-managed playback systems dig up bass that recording engineers didn't hear because their monitoring systems weren't bass-managed and their monitor speakers weren't full-range. This unmonitored bass sounds ultra-funky, and there's absolutely nothing users can do about it without reconfiguring their systems every time they switch discs. It's time for us to lodge some complaints with the production community!

8. Analog signals from a DVD-Audio or SACD player that are input to an AV controller through its multichannel analog inputs may NOT be bass managed inside the AV controller. Unlike a digital input, where the incoming signal is run through bass management (which is always performed in the digital domain) before it is converted to analog, an analog input must feed its signals through the controller's analog-to-digital (A/D) converters before they can be sent to bass management. A/D conversion might be okay for some analog signals, but not those from high-resolution formats like Packed PCM (PPCM) or Direct Stream Digital (DSD).

Thus, most controllers do not convert their multichannel analog inputs to digital, or run them through bass management. This task is left to the disc player, most of which don't have enough DSP horsepower to provide filters as advanced as those in controllers. In fact, some players do not even provide the option of setting all the main speakers to Small-the front speakers are often restricted to Large. Furthermore, the digital-to-analog (D/A) converters on disc players' subwoofer outputs often do not have enough headroom to output bass at sufficiently high levels. The level of the subwoofer output is usually reduced by either 10dB (for a player without bass management) or 15dB (for a player with bass management), with the expectation that the signal will be boosted by the controller. This is all well and good except that many controllers are not set up to apply that boost to their analog subwoofer inputs!

The current solution to both of these problems is to set all the outputs of a disc player to Large and insert an external bass-management device between the player and the controller. (Bass-management devices are available from Outlaw Audio and Miller & Kreisel, among others.) It's not a very appetizing thought, but it's a heck of a lot better than lacking highpass filters for the front speakers or having bass that's 15dB too low!

Fortunately, there is another solution on the horizon. Universal digital interfaces, like FireWire, that can carry PPCM and DSD are appearing on the latest crop of disc players and AV controllers. If the external bass-management box is a turn-off, reach for these new players and controllers, which bass management for PPCM and DSD works just like it does for other digital-audio formats.

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Offline petetherock

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Calibration and the ruler flat response...
« Reply #19 on: October 19, 2008, 18:12 »
There is a sticky above with calibration tips, but it has been discussed and I remember the duo "J" gurus chipping in to express their opinions that we may actually Not want a ruler flat freq response and many owners esp those who have SVS subs like to 'bump' up the 40-20 Hz area where the 'thump in the chest' sensation occurs.

So for the new HT owners, have a listen if possible to a properly set up home, and hear but more importantly FEEL the difference as compared to the pathetic showrooms in large eletronic stores.

See the SVS section and look out for the bass meister... he won't bite and often invites nice bros, newbies and all to his home... bring earplugs... ;)
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Offline petetherock

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #20 on: October 22, 2008, 19:11 »
A cheap way to get a bass shaker effect:

If you have a small sub, place it under your seat, and literally feel the vibrations. I use 2 subs and placing the Velodyne under my seat adds to the whole visual, aural and tctile feel!
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Offline petetherock

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #21 on: November 20, 2008, 18:29 »
And we have to bring this up once in a while in case the search button is disabled... :)

For setup with SPL meter tips:
I found yet another site:

http://www.dtvforum.info/index.php?showtopic=31720
Plus a few I pasted in the sticky above....

Quote
Quote:

Excerpt from "UNDERSTANDING SURROUND SOUND - 5.1 And Beyond..." writen by Mark Techer, July 2000
SYSTEM CALIBRATION.

AUDIO ADJUSTMENTS.

A well designed controller will have a few standard items. Apart from different surround sound decoding algorithms, your audio processor should have level trims for all channels including the FRONT LEFT and FRONT RIGHT.

For those systems that do not, you will need to find the level where the Left channel that reads +75dB and remember or mark the master volume at that point. That number will your 00dB level, even though it may not be close to 00dB.

Also, not all volumes display in relative (negative dB figures), some display in “absolute” (number that increase with the loudness). If your system is such, then choose a “round” number and then adjust each channel trim to read +75dB on the meter.

The worst case scenario will be a unit that does not offer either trims on the front left and right channels or a master volume displayed in absolute values…

In this digital age, usually both the trims and the master volume control will be digital and the trims should be in half dB adjustments. Full dB adjustments are too course and may not allow total precision.

All well designed decoders will also have an internal noise generator. The tone emitted from the noise generator will be equivalent to an audio tone recorded at –30dBFS for film sound (18BIT) which is the same as 105dB – 30dB or +75dB. Using a Sound Pressure Level meter and these tones, you will be able to precisely adjust the acoustic output level of your system to equal that of a cinema or dubbing stage.

The end result will be that you will hear the sound track they way it was heard in the studio that created it both from channel to channel sound as well as absolute volume level.

The SPL meter should have an analog display. The use of the analog model is preferred as reading can be under 1dB and depending on the type of level trim on your system, totally accurate.

The radio shack SPL meter is the same type used by the film industry. Independent tests revealed that this meter was the most accurate model from a group of meters tested including more expensive models.

The new meter from JAYCAR is more expensive, but it has a calibrate feature. Whilst this meter is digital, it does display in 1/10th of a dB.

USING THE METER.

The meter has a rotating “range” dial and two switches. The range dial provides the SPL range you would like to measure in decibels starting form 60dB to 120dB. There is also a battery check “BATT” position just next to the “OFF” position.

The two switches are labeled “WEIGHTING” and “RESPONSE”. Set the “WEIGHTING” switch to the “C” position and the “RESPONSE” switch to the “SLOW” position.

Set the dial to the 70dB range. This will now allow you to read SPL from 60dB to 76dB.

EDIT: Position the meter in the prime listening position.

Hold the meter at arms length from the body. The meter should be at seated ear height, pointed up and slightly forward.

DO NOT POINT THE METER AT ANY ONE SPEAKER.

I use a tripod to hold the meter and move well away so that reflections from my body are not read by the meter and give false readings.

Activate the test tone generator on your surround sound processor. Well designed processors will default to a 0dB reference level position regardless of the actual volume position and start at the LEFT front channel.

Observe the level reading. It should be reading at +75dB/C/SLOW. If the audio level is too high, the meter’s needle will “peg” and you will have to reduce the trim level for that channel to read the desired +75dB/C/SLOW. If the audio level is too low, adjust the trim to read the correct level.

PEGGING OF THE NEEDLE IS NOT ADVISED AND MAY ACTUALLY DAMAGE THE METER.

Once you are satisfied with the level, proceed to the next channel, working in turn around the room.

SUBWOOFER AND LFE LEVEL.

While the standard level for all main channels (including the Surrounds) is +75dB/C/SLOW, setting the level for both the subwoofer and the LFE channel is a little more complex.

Ideally you would use a Real Time Spectrum Analyzer. The level of the Subwoofer can be set with the SPL meter by the following method. The level of the Subwoofer should also read +75dB on the meter, however the tone for the Subwoofer is a “Warble” and the level will very along with the frequency. It will be difficult to set the level at the 70dB range.

Turn the dial to the 80dB range. If your processor has a Sub test warble, adjust the trim to read an average of +79dB/C/SLOW with the lowest part reading at –5dB on the 80dB scale. The level difference will be around just 4dB and is equivalent to the average level of +10dB when using the RTA.

DO NOT SET THE SUBWOOFER TO READ 10 DECIBELS HIGHER THAN A MAIN CHANNEL WITH THE SPL METER.

The LFE channel is a fixed value in reference to the subwoofer level. That is if you increase the Subwoofer level, you will also increase the level of the LFE channel. Some decoders offer a separate trim for the LFE channel. It should be set to the same level as the Subwoofer. If the SUB trim is 0dB, then so is the LFE trim.

THE LFE TRIM WILL NOT GO ABOVE 0 REF DECIBELS. IF THE LEVEL IS NOT HIGH ENOUGH AT THE 0 REF DECIBEL LEVEL, INCREASE THE GAIN ON THE SUBWOOFER WHERE POSSIBLE.

PLAYBACK.

Once your system has been calibrated, you can enjoy a film. The 0dB reference level is the level you should watch films at. You may of course reduce this level if it is too loud.

DIALNORM may be seen on some format decoders. It is a part if the Dolby Digital coding and will advise you of the average level of dialogue in a program. If the DIALNORM reads a plus figure EG “DIALNORM +4”, you must reduce the level of the master volume by 4dB. When used correctly, you will find that the level of dialogue remains consistent across a wide range of program material. The peak levels however will vary occasionally resulting in some very high Sound Pressure Levels.

Enjoy your films and music…






EDIT:

A small difference in SPL readings will be quite acceptable actually. However to correct a larger difference will need a proper equaliser, a BFD or even deploying more than 1 subwoofer. Or ask one of the bass gurus to vist your place...

Cheers
« Last Edit: November 20, 2008, 18:32 by petetherock »
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Offline petetherock

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Audyssey and setting up the subwoofer
« Reply #22 on: December 08, 2008, 07:38 »
Many new models have Audyssey built in, so this might help:
From Audyssey thread:
http://www.avsforum.com/avs-vb/showthread.php?p=14456895#post14456895
Quote


III. Subwoofer Setup
A. Determine the optimal placement of the subwoofer within your room using common accepted practices. (location, location, location)
1. Here are some useful references for subwoofer setup:
a. Audioholics subwoofer placement article: http://www.audioholics.com/tweaks/get-good-bass/bass-management-basics-2013-settings-made-simple/
b. Harman multiple subwoofer placement white paper: http://www.harman.com/wp/pdf/multsubs.pdf
B. Disable the Low-Pass Filter (LPF) on the subwoofer, if allowed.
1. Disabling the LPF will result in more accurate subwoofer distance measurements.
2. If the LPF cannot be disabled, set it to the highest frequency allowed.
C. Ensure the subwoofer(s) are at least 3 – 5 inches (7 – 13 cm) from the wall.
1. Reverberating walls may result in inaccurate subwoofer distance measurements.
D. Set the subwoofer polarization (0 or 180 degrees) using common accepted practices.
1. If you have two subwoofers, ensure their polarization settings are the same.
E. If the subwoofer has a phase control (in addition to the polarization control), set it at “0”
1. Phase controls on subwoofers apply "delay" at one frequency rather than the needed group delay that is frequency independent. So, it is best to just leave them at “0”.
F. If the sub has an EQ system, use it to tame large peaks before calibrating with Audyssey.
1. Narrow peaks or dips in the response below 100 Hz that are 1/3 or 1/6 of an octave wide can be improved—but not eliminated—by Audyssey Mult EQ XT.
a. In these situations, the built-in subwoofer EQ systems might be useful.
2. Velodyne’s SMS and JL Audio’s ARO are two examples of EQ systems.

G. Calibrate the subwoofer volume
1. Set the volume control on the subwoofer at the middle of the adjustment range allowed.
a. Please note this “starting point” may not work with all subwoofers.
2. Place the microphone at the primary listening position (the center of the listening area) and run through the calibration process for the first measurement—until all speakers have been measured once.
3. After the first measurement process is complete, select "Calculate", then "Save" or "Store", then go to "Check Parameters".
a. Audyssey will calculate the speaker distances and trim levels from this first measurement.
b. Each manufacturer has a slightly different interface, so the terminology may not exactly match.
4. Check the subwoofer trim levels in the receiver / processor menu.
a. If the subwoofers trim level is at the maximum limit of the cut or boost adjustment range allowed, you need to adjust the volume control on the subwoofer and repeat step #2. Specific instructions will follow.
b. For example, Denon receivers have a trim adjustment range from -12dB to +12dB.
c. Trim adjustments are a tool used to achieve the goal of producing a specific SPL from each speaker / subwoofer when the system is played at reference level.
5. If the subwoofer trim level is at the maximum boost, turn up the subwoofer volume a bit and repeat step #2
6. If the subwoofer trim level is at the maximum cut, turn down the subwoofer volume a bit and repeat step #2
7. A suggestion for tweakers is to set the subwoofer trim level in the range of ±3 dB.
a. This is only a suggestion for the tweaker who likes to play around.
b. Audyssey’s position is to perform steps 4 to 6 above.

• Note: This process is for checking the trim levels only. After you have completed the subwoofer setup, be sure to start the measurement process over, following the guidance in section V to use all six or eight measurement positions available.
[/size][/quote]
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Offline petetherock

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Hum.... or mai hum...
« Reply #23 on: December 10, 2008, 16:49 »
Posted this in the sticky above too

Not this hum:



But this:

Subwoofer hum:

http://www.xtremeplace.com/yabbse/index.php?topic=37335.0
http://www.xtremeplace.com/yabbse/index.php?topic=30491.0
http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz/?searchterm=hum

Quote
When two or more devices are connected to a common ground through different paths, ground path noise, or a ground loop can occur. Thus, a system grounded at two different points, with a potential difference between the two grounds can cause unwanted noise voltage in the circuit paths. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum in audio or video equipment. The ground loop can be eliminated in one of two ways:


Remove one of the ground paths, thus converting the system to a single point ground.
Isolate one of the ground paths with an isolation transformer, common mode choke, optical coupler, balanced circuitry, or frequency selective grounding.


The most practical and usually most cost effective method for consumer audio applications is to use an isolation transformer. An isolation transformer is a device which, in the case of cable signals, allows all the desired signals to pass freely, while interrupting ground continuity, hence breaking ground loops. By using an isolation transformer, the ground noise voltage will now appear between the transformer windings and not circuit input. The noise coupling is primarily a function of parasitic capacitance between the transformer windings and can be reduced by placing a shield between the windings. This is an effective method to implement assuming the transformer has sufficient bandwidth, isn't too costly or bulky, and a direct DC signal path is not required for the application.

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Offline petetherock

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LFE
« Reply #24 on: January 07, 2009, 16:29 »
Some interesting information on LFE aka Low Frequency Effects



"Bass Management and the LFE Channel"

http://www.ultimateavmag.com/howto/805bass/index1.html


From Dolby

http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/38_LFE.pdf

Quote
In contrast to the main channels, the LFE channel delivers bass-only information
(<120 Hz) and has no direct effect on the perceived directionality of the reproduced
soundtrack. Its purpose is to supplement the overall bass content of the program or
to ease the burden on the other channels. The LFE channel was originally devised
for 70 mm movie productions to deliver a separate bass signal to one or more
additional subwoofers placed behind the movie screen. This allowed deep bass
effects to be added to movie soundtracks without having to upgrade the existing
speakers and amplifiers in the three main screen channels. It also meant that the
headroom of the 70 mm magnetic audio recordings would not be taxed at low
frequencies, which would have detracted from their loudness capability at mid and
high frequencies. Finally, no additional frequency crossovers would need to be
retrofitted into existing cinema processors to redirect the bass from the main left,
center, and right channels to the subwoofer(s). Taking advantage of the available
channel capacity on 70 mm prints to deliver a separate bass effects signal proved to
be the most direct, convenient, and economical way to supplement the lowfrequency
capability of movie soundtracks.


"The Misunderstood 0.1 LFE Channel in 5.1 Digital Surround Sound"

http://www.hometheaterhifi.com/volume_7_2/feature-article-misunderstood-lfe-channel-april-2000.html


The crossover frequency is where the main speakers hand over bass reproduction to the subwoofer and the LFE RCA output is usualy how the connection is made. If your main speakers can only handle down to 80Hz, crossover at this, or let the auto-setup of your new amp help you.

Quote
LFE in the home

With bass management (the ability to strip bass from one channel and send it to another) as a standard part of all our Dolby Digital home equipment, it would have been conceivable for the home delivery to do without the LFE track.  But again, for the sake of being able to transcribe a cinema soundtrack directly to DVD or Laserdisc, the LFE channel remains part of the system.  Despite the stigma that in the cinema the LFE channel is 'the subwoofer' channel, most home subwoofer(s) will be asked to voice bass from both the main channels and the LFE track.  Two different sources, two different settings.  The LFE channel and the subwoofer are not really synonymous or interchangeable from that point of view. 

Stop!  Before you run home and set your subwoofer 10 dB higher than you’ve already set it, you need to read on and find out why this is not necessary.

For consumers, we want things to be simple.  Up until recently, only serious enthusiasts would use an SPL meter to set the levels of their home theater equipment, let alone ask everyone to remember to set the LFE channel differently.  For this reason, home Dolby Digital equipment is pre-set to play LFE data 10 dB higher than a main channel (or 10dB higher than the bass from a main channel).  It is only necessary to set the subwoofer relative to a main channel and the LFE level will be correct.  Very few processors allow direct manipulation of the LFE level. That is why the menus on most receivers say "Subwoofer Level" rather than "LFE Level".

We home users don’t use an RTA to set-up our systems, but if we did, it could look something like Figure 4.  Bass which is redirected from a main channel would be balanced with the output of that channel, and the LFE data automatically playing 10 dB higher.  Most of us don't have an RTA so an SLP meter (sound pressure level) has to do.  There are numerous sources of test tones for setting the subwoofer level (different from LFE level), all optimized for a simple SPL measurement (AVIA, Video Essentials, and Delos Surround Spectacular, to name a few).  It is very important to realize that if the subwoofer level has been set correctly using one of these tools to match a screen channel, the LFE data will be at the appropriate setting without any further adjustment.  If you were to raise or lower the subwoofer level, the LFE level would rise or fall with it, tracking it at +10 dB.  Processors that let you manipulate the LFE level independent of the subwoofer level are few, and most of these only let you reduce the offset to protect a less capable subwoofer from undue stress.



DTS's LFE channel in consumer applications, unlike its cinema counterpart, is discrete but still has a few 'special' considerations.  In the early days of mixing 5.1 for DTS CDs, the studios were not being calibrated correctly, with the end result of the LFE channel being set too low.  When the material is played back on a correctly calibrated system, the LFE channel is way too high.  THX was forced to introduce DTS Music and DTS Movie playback modes which distinguish between a correct LFE setting and a -10 dB setting to compensate for material assembled under mis-calibrated circumstances (though not all THX processors offer this convenience).

In Utopia again, a home theater would have all three screen channels capable of true full range playback, which includes deep bass, and do so with the prescribed 105 dB peak.  This is almost never the case in the real world.  We need to ask our subwoofer to do more than just voice the LFE channel.  To quote Miller & Kreisel, bosses of bass, “never send only the LFE to your subwoofer”.  No, they’re not just trying to sell you a sub. There are very sound reasons for this advice.  Some have to do with the software (the movies on the DVDs), some with the hardware.

One reason not to send a subwoofer the LFE channel alone is that there may not be anything on it or there may not be an LFE track at all.  When coming out with the DVD format, it was important that consumers be able to always see and hear the program, without extra hardware like 5.1 decoders.  This is why there is always an AC-3 or PCM soundtrack: Either can be played by any DVD player.  Even a 6-channel AC-3 mix can be played without a 6-channel decoder because of the DVD player’s internal downmixer.  This takes the soundtrack and downmixes it to a 2-channel Pro Logic output.  Important is the fact that the LFE channel is not part of this downmix and gets discarded.  Production facilities know that unless they provide a dedicated two channel soundtrack, nothing important should be exclusively put in the LFE channel: Depending on the playback system, it may not be heard.  When done right, essential information (which can include deep bass) will be put in the screen channels.



So, on some soundtracks, sending only the LFE to your subwoofer could leave it with nothing to do while your mains struggle.  While some people like to feed a full range signal to their main speakers, they should in addition send those channels’ bass to the sub so it can fill in the extreme bottom octave information that might be in those tracks.  Mains which can reach as low as a dedicated subwoofer are few.  Unfortunately this flexibility is not always available on consumer equipment; setting a main speaker to ‘large’ often excludes the subwoofer from getting a share of that signal.

On the flip side, you don’t need a subwoofer to hear the content of the LFE track.  If your mains are of substantial mettle, and you don’t have a sub, bass management can usually re-route the LFE to your fronts.

Therefore, the subwoofer jack can contain only LFE (not recommended), a mixture of LFE and bass from the main 5 channels, or nothing at all.

Please post instead of sending a pm, so more can learn.

My gear:
http://peteswrite.blogspot.com/2019/04/my-setup-42019.html

Offline jonlee

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #25 on: January 08, 2009, 00:31 »
Pete, to summarise:

1. Using the receiver test tone, set all speakers to 75db on the spl meter..

2.  Set sub to 79db on the spl meter.

3.  If receiver allows, set front speakers to full range + double bass (ie bass to be sent to both front and sub).

Correct?

Offline petetherock

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #26 on: January 08, 2009, 09:44 »
There are 3 ways to setup the subwoofer these days, bass gurus like Jason Yeo & Jag will have even more tricks up their sleeves.


Plan A - simplest - let the auto-setup do its work - MACC, YPAO, Audyssey and other flavors. Then tweak the settings to your liking.

Plan B see below



Pete, to summarise:

1. Using the receiver test tone, set all speakers to 75db on the spl meter..


I believe Jason recommends 10 db louder than your normal listening volume
2.  Set sub to 79db on the spl meter.

I use both 80 and 70 depending on the above setting, my analogue Radio Shack sets in 10s


3.  If receiver allows, set front speakers to full range + double bass (ie bass to be sent to both front and sub).

This depends very much on the size of the front and centre speakers. Most small home owners have bookshelves, and unless it is a 805s from B/W, let the sub handle things for HT, and use Source Direct for music.


Correct?


Plan C - get a disc with test tone frequencies that go from 10 to say 20 khz. Then play it back in the mode you use most, eg PL IIx on a Cd or DVD source. Then use a SPL meter to look for defiencies and areas of boost.

Of course if you have a PC to make a waterfall, BFD etc, things get even more fun....

Cheers
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Offline petetherock

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Subs in Singapore
« Reply #27 on: January 08, 2009, 09:49 »
Firstly
REL is now carrried by KEC as well


There are subs for < 1k, but after a few months, you will feel rather unhappy and a need to upgrade, so why not do it right the first time.

**** these are my personal opinions and are in no way endorsing certain brands, nor do I get money from them for this ***

Most cost 1-2k

- small form factor subs - Velodyne SPL 1000i, 800i or the remote versions

- Rel - nice for music, decent for HT but try the SVS for more grunt, SPL and depth

- SVS - HT monsters PB 12 + or the PC equivalent (needs importing - see the MO thread)

- HSU - VTF 3 + turbo (also needs importing)


Edit: Note some are not available locally, and each has its virtues. RELs are tight and have traditionally been the choice for subs. But SVS do better in HT IMO. But they do not suit Instant Gratification Folks who want their kicks immediately.


« Last Edit: January 08, 2009, 09:59 by petetherock »
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Offline t1m3ch453r

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #28 on: January 08, 2009, 09:53 »
Pete - you havent heard the Storm 5 I guess :P since you are indicating it doesn't have enough grunt.

Offline petetherock

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Re: Subwoofer discusion thread - suggestions, tips and info
« Reply #29 on: January 08, 2009, 10:45 »
You have not my SVS I guess if you indicate the REL has more grunt.

Pete - you havent heard the Storm 5 I guess :P since you are indicating it doesn't have enough grunt.
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