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Discussion Starter · #1 ·
Anyone know where I can find discrete .1 LFE test tones from about 10-15Hz up to about 100-120Hz?

I prefer 1 Hz increments, but 1/6 octave would do.

Thanks!
 

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Discussion Starter · #4 ·
Actually... I need combined 5.1 test tones.

In other words... I need a 20Hz .1 LFE tone combined with a 20Hz non-LFE tone.

I need both outputting at the same time. Is that possible... do they make test tones like this?
 

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Discussion Starter · #5 ·
To further clarify... I need 5.1 channels outputting from 10-15Hz up to about 120Hz. I need all six channels to be outputting the same tone at once.

What I have is a unit that is equalizing the .1 LFE frequency separate from the equalized and redirected sub-80Hz low frequencies from the other five speakers.

REW does not output a .1 discrete signal in its sweep, to I am unable to test the equalization of the unit in question without the .1 discrete signal along with the combined redirected signal as well.

I know... who in their right mind would make such a unit.
 

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Elite Shackster
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Actually... I need combined 5.1 test tones.

In other words... I need a 20Hz .1 LFE tone combined with a 20Hz non-LFE tone.

I need both outputting at the same time. Is that possible... do they make test tones like this?
As far as I know, that isnt possible. Any system that can process a dedicated sub channel, is either separating the .1, or isnt running in bass management mode, i.e pure audio or with speakers full range, so no .1 present. Some AVR's do allow you to run LFE to the speakers at the same time as the sub, but that is all done on board the processor itself, not within the source material.

I need to get a better grasp of the exact issue you seem to be having with the unit. I will get to it ASAP.
 

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Discussion Starter · #7 ·
Actually... nearly all material has LFE and non LFE bass. So having both is possible.

There is .1 discrete LFE and there is redirected bass below the crossover frequency.
 

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Sonnie,

So basically if you are playing a 120hz test tone in 5.1 and your sub is crossed at 80hz then you would expect most off the audio going to the 5 speakers and very little through the sub. The higher up the frequency band you go it just then comes out off the speakers and not the sub.

Can I ask what is the reason you want this for.

Also if it is to calibrate in some way wouldn't the Avia calibrating disc be better.

Sent you a PM regarding finding some software to convert the single audio format to 5.1. Just googled it and people have done it, just need to find out what they used.

cheers

Graham
 

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Elite Shackster
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Actually... nearly all material has LFE and non LFE bass. So having both is possible.

There is .1 discrete LFE and there is redirected bass below the crossover frequency.
That would depend on system set up though wouldnt it. LFE is 120hz and below, so in theory, if you were running 80hz crossovers, there is potential for 40hz ish of lfe being sent to speakers etc. It would also depend on the source. Some movies (a lot actually) dont bother with LFE over 80hz due to the guideline set up of 80 crossovers.

Redirected bass and LFE are different in the mind of the processors, but the idea is the end result is the same as far as our ears are concerned. When you run a film though, which is proper .1 discreet, you only have LFE and non LFE, and the only potential is that speakers might play LFE material, not that your sub would play non LFE bass. I do realise there is potential for the sub to play non LFE bass.
 

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Elite Shackster
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Sonnie,

So basically if you are playing a 120hz test tone in 5.1 and your sub is crossed at 80hz then you would expect most off the audio going to the 5 speakers and very little through the sub. The higher up the frequency band you go it just then comes out off the speakers and not the sub.

Can I ask what is the reason you want this for.

cheers

Graham
Subs are big, which they need to be to produce the lowest frequencies. People generally only have one as a result. To keep the bass so you cant localize it, the frequencies it reproduces are kept to those your ears cant pin point, which is widely accepted as 80hz and below. This then allows that single sub to be placed anywhere in the listening area, further increasing the ease of incorporating it into your home environment.

If you have a dual or more sub setup, with the subs separated like your front speakers are (ideally wider than your mains and set back a touch), then its possible there is some benefit from running your LFE upto 120hz, and letting the subs take care of all the LFE right upto that frequency. Trying it is the key to answering if you would like it or not.
 

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Discussion Starter · #11 ·
So basically if you are playing a 120hz test tone in 5.1 and your sub is crossed at 80hz then you would expect most off the audio going to the 5 speakers and very little through the sub. The higher up the frequency band you go it just then comes out off the speakers and not the sub.
Yep!


Can I ask what is the reason you want this for.
I am doing some testing of a .1 discrete LFE channel and REW does not provide a .1 discrete signal... and if it did, I still would not have the proper digital setup to pass it to the processor. So... I am stuck with having to test it manually the old fashioned way... with test tones and an SPL meter.

You will hear more about this later, but I don't want to get to deep into it right now.


Also if it is to calibrate in some way wouldn't the Avia calibrating disc be better.
I don't have an AVIA disc, but IIRC, it only has pink noise and sweeps. I am not sure if it has .1 discrete LFE test tones or sine waves, but maybe I need to check and see if it does, if in case I do not find them elsewhere for free. :bigsmile:

Thank you for helping me find a solution... it is most appreciated... :T




That would depend on system set up though wouldnt it.
Naturally... yes... if you happen to be someone who has speakers that can handle full range bass and do not crossover your speakers, there is obviously no redirected bass going to the sub, just LFE from the source. However, this can create difficulties in equalizing the low frequencies. For example... if you have your sub handling LFE frequencies up to 80Hz and your other speakers are also playing up to 80Hz, it is like have multiple subwoofer scattered around the room. There is no way to equalize all of the sub-80Hz frequencies together... you would have to equalize them separately... an near impossible feat. It is really better to have all the sub-80Hz bass redirected to the subs so that you can equalize it all together.


LFE is 120hz and below, so in theory, if you were running 80hz crossovers, there is potential for 40hz ish of lfe being sent to speakers etc.
LFE is discrete and only routed to the subwoofer, so there is no possibility, regardless of your crossover, for any LFE to pass to the speakers.


Redirected bass and LFE are different in the mind of the processors, but the idea is the end result is the same as far as our ears are concerned. When you run a film though, which is proper .1 discrete, you only have LFE and non LFE, and the only potential is that speakers might play LFE material, not that your sub would play non LFE bass. I do realise there is potential for the sub to play non LFE bass.
LFE is discrete and only routed to the subwoofer, so there is no possibility for any LFE to pass to the speakers.
 

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Sonnie said:
What I have is a unit that is equalizing the .1 LFE frequency separate from the equalized and redirected sub-80Hz low frequencies from the other five speakers.

REW does not output a .1 discrete signal in its sweep, to I am unable to test the equalization of the unit in question without the .1 discrete signal along with the combined redirected signal as well.

I know... who in their right mind would make such a unit.
Are you trying to EQ your bass post processor or in the processor? If post, it won't matter whether your processor is giving you just an LFE signal or LFE plus redirected bass, as your subwoofers are in fixed positions and bass at your seat will behave the same no matter what the source.

If you are trying to EQ your bass in the processor, and it is only using the LFE channel, that's going to be difficult. Even if you find LFE sine waves and confirm/deny it is doing it's job, how then would you go about EQ'ing the redirected bass? On top of that, I don't believe I have ever seen a processor do a decent job of EQ'ing bass with capable subwoofers, as they usually build in a highpass and roll off the low end.

Or am I missing your intent entirely?
 

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Discussion Starter · #14 ·
So then, if you have a movie with LFE in the 80-120hz region, where does it go, is it lost? This is one point Ive never actually taken the time to look into.
Well... as you suggested earlier, there may not be a lot of recorded information in the LFE encoding between 80-120Hz, but if there is... and your receiver or processor allows a low pass crossover for the LFE channel and you set it to 80Hz... yeah... anything between 80-120Hz would be lost. LFE is intended for the sub channel, so having it redirected to the main speakers would have it localized to those speakers and perhaps express something that is not originally intended.
 

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It is possible to do this. I know of one source with all discrete tones over 5.1, but no more than one per channel. If you want tones with the same wave sent to the LFE, and say R & L mains channels (or all of them) at the same time you will need to roll your own.

You will need a tone generator, a Dolby Digital encoder, and a multi-tracking wave mixer/editor. To put them onto a DVD you will also need DVD software that allows DD ac3 files to be included.


The cheapest way to go would be to buy an older copy of Sony Vegas Pro online. You can still find ver 8 for ~$300. This has the multi-tracking wave editor, a DD encoder, and the DVD software all in one.

You will still need a good tone generator, and I would suggest a good wave editor for working with the tones before placing them into Vegas, as it is more of a mixer with editing tacked on. An old version of Cool Edit (or Pro) will work great for this.

Adobe bought CE out and reworked it into Audition 3, but it is a GUI nightmare. I have it, but still prefer CE Pro 2.

The tone generator is kinda open. I will caution you to check out the output with a wave editor before deciding on one. Some put out distorted tones, believe it or not.

You will also need to watch the levels very carefully. Everyone always tries to do 0dBFS tones, but passes through encoders do not like them. On my old disk the .5dBFS Peak LFE tones were pure from the generator, but after passing through the wave to ac3 encoder they were not anymore. This is when people start chiming in about digital is digital, and how it makes no sense. Then you have to remind them that .wavs are lossless, and .ac3 is lossy. There will be minor changes to the signal, and if you don't watch it they will be audible. Using the DVDs audio sample rate throughout the chain will help some.
 

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That would make me question a couple things. If movies no longer bother with LFE over 80hz, why do we need the LPF at all, and what is there to be gained from setting it at 80hz rather than 120, other than to make sure you do lose anything over hz should it be in there to prevent localisation issues or unwanted hum (according to Onkyo). I kinda assumed processors would simply allow the speakers to play LFE frequencies above the LPF, but then I never honestly really thought or worried about it.
 

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Discussion Starter · #17 ·
If you are trying to EQ your bass in the processor, and it is only using the LFE channel, that's going to be difficult. Even if you find LFE sine waves and confirm/deny it is doing it's job, how then would you go about EQ'ing the redirected bass? On top of that, I don't believe I have ever seen a processor do a decent job of EQ'ing bass with capable subwoofers, as they usually build in a highpass and roll off the low end.

Or am I missing your intent entirely?
No... you are almost dead on spot here. The unit I am testing has built-in auto equalization (each channel can be adjusted independently after the auto equalization). The "Subwoofer" channel of equalization is only equalizing the .1 LFE signal... and does not include the summed bass that is redirected from the output below crossover point of the other speakers. Believe it or not... the redirected bass is equalized and passed on, creating extremely flawed equalization.

The purpose of the requested test tones is to see what the "Subwoofer" equalization is doing to that LFE signal... and to further prove that the method used is flawed.
 

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Discussion Starter · #18 ·
It is possible to do this. I know of one source with all discrete tones over 5.1, but no more than one per channel. If you want tones with the same wave sent to the LFE, and say R & L mains channels (or all of them) at the same time you will need to roll your own.

You will need a tone generator, a Dolby Digital encoder, and a multi-tracking wave mixer/editor. To put them onto a DVD you will also need DVD software that allows DD ac3 files to be included.


The cheapest way to go would be to buy an older copy of Sony Vegas Pro online. You can still find ver 8 for ~$300. This has the multi-tracking wave editor, a DD encoder, and the DVD software all in one.

You will still need a good tone generator, and I would suggest a good wave editor for working with the tones before placing them into Vegas, as it is more of a mixer with editing tacked on. An old version of Cool Edit (or Pro) will work great for this.

Adobe bought CE out and reworked it into Audition 3, but it is a GUI nightmare. I have it, but still prefer CE Pro 2.

The tone generator is kinda open. I will caution you to check out the output with a wave editor before deciding on one. Some put out distorted tones, believe it or not.

You will also need to watch the levels very carefully. Everyone always tries to do 0dBFS tones, but passes through encoders do not like them. On my old disk the .5dBFS Peak LFE tones were pure from the generator, but after passing through the wave to ac3 encoder they were not anymore. This is when people start chiming in about digital is digital, and how it makes no sense. Then you have to remind them that .wavs are lossless, and .ac3 is lossy. There will be minor changes to the signal, and if you don't watch it they will be audible. Using the DVDs audio sample rate throughout the chain will help some.
This is what I was afraid of hearing and confirming about the combined signal.

I do not plan to spend any money on it... so my next goal will be to simply find discrete .1 LFE tones... and I am assuming those are available from somewhere.



That would make me question a couple things. If movies no longer bother with LFE over 80hz, why do we need the LPF at all, and what is there to be gained from setting it at 80hz rather than 120, other than to make sure you do lose anything over hz should it be in there to prevent localisation issues or unwanted hum (according to Onkyo).
Good questions... and your answer may be the most beneficial reason for using the LPF.

I am not sure of what the trend is with limiting frequencies of encoding LFE, but it might answer some questions.
 

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Regarding the LFE bandwidth, just because you set your subwoofer crossover at 80hz doesn't mean your sub automatically isn't still getting the full LFE channel. Processors with a richer feature set usually give you fine control over the LFE channel, and by default, they tend to feed the sub the full signal regardless of your redirected bass crossover point. You can reduce the bandwidth of the LFE channel if you desire in stated processors, but why would you?

There can be quite a bit of bass in the LFE channel from 80-120hz assuming the scene calls for it.
 

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This is what I was afraid of hearing and confirming about the combined signal.

I do not plan to spend any money on it... so my next goal will be to simply find discrete .1 LFE tones... and I am assuming those are available from somewhere.
If you can find my old disk it has the LFE from 1-20Hz in one hertz increments, and then 25-120Hz in five hertz stops. All other 5. channels are 20-120hz in five hertz stops.

I have popped out custom test signals in raw ac3 for computer playback with multi-tracked tones, but I don't have any links.

I could run you some myself, if I ever get that computer back up and running again. Anyone with a old spare ATI 9800 Pro 256MB, or better AGP x8 card laying around unused? :D
 
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