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Subwoofers | LFE vs Speaker level inputs

Mi_10

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I understand that typically subwoofer users for HT use the AVR's LFE output which makes a good case if you are using any type of Correction and Calibration (Audyssey /Dirac etc...) for subs; and Generally people connecting subs to stereo setup use either Preouts ( if their CD player has one) or use Stereo Amplifier's speaker output to draw a parallel connection to sub. The LFE warrants the use of an optical cable whereas the latter type of connection is done via XLR / RCA or speaker wires.
Have anyone tried switching between the two types to see if there is any difference in content played ? Technically both are signals, but does a LFE (Low Frequency Effects) anything more than what will be heard of a 2.1 setup ? Assuming both are playing the same content.
 
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arj

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I believe LFE is not an Optical cable but a regular RCA. With an LFE, your AVR is sending the signal to the speakers and Sub as per the configured crossover point but at speaker level you are using the subwoofers High pass settings which may not be so accurate and very placement sensitive to integrate the two

For most AVRs the LFE is what should be the right approach.

For stereo its a different matter as most stereo amps do not have a sub out and hence varies by Amp / subwoofer.
 

Kannan

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The LFE warrants the use of an optical cable
I doubt this, this is usually a normal phono cable (RCA post DAC) given to an active subwoofer with the bass management done on the receiver as you have mentioned.
If indeed your receiver has a digital LFE output (toslink as you mention) in your receiver, then you would need a subwoofer with an optical input and an inbuilt DAC.

Is bass management better on the AVR or the Sub. Probably it is better to do it on the AVR as the rest of the channels are also managed in the AVR. Also gives flexibility of using the calibration mic and the remote on the AVR to tweak easily.
But again the same can be set on the active subwoofer also, depends on the DSP flexibility of your AVR and crossover options on both the AVR and the subwoofer.

In my stereo setup, I use an active sub which has a pair of input and output. I run a RCA pair from the preamp to the sub input and another RCA pair from the sub output to the power amp. The crossover is set on the subwoofer.
When the sub is on, the output of the sub is high passed at my crossover point set on the subwoofer and when the sub is switched off, the full signal is passed from input to the output.
 

MaSh

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I understand that typically subwoofer users for HT use the AVR's LFE output which makes a good case if you are using any type of Correction and Calibration (Audyssey /Dirac etc...) for subs; and Generally people connecting subs to stereo setup use either Preouts ( if their CD player has one) or use Stereo Amplifier's speaker output to draw a parallel connection to sub. The LFE warrants the use of an optical cable whereas the latter type of connection is done via XLR / RCA or speaker wires.
Have anyone tried switching between the two types to see if there is any difference in content played ? Technically both are signals, but does a LFE (Low Frequency Effects) anything more than what will be heard of a 2.1 setup ? Assuming both are playing the same content.
Which sub or source are you using that needs an optical connection to the Sub? Most subs would need an RCA connection for LFE and Pre Amp input. LFE is a Separate channel in a Multi Channel Audio Signal. Some subs in addition to this have speaker level inputs too.

So I guess you want to check the difference between the Pre Amp input Vs Speaker Level input to the sub. I personally would prefer the Pre Amp input.

MaSh
 

Mi_10

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My bad ! i was under the impression that LFE is a Digital Coax output. Thanks for clarifying. and Yes, basically it boils down to the difference between PreAmp input vs speaker input. I am asking this question since i am running a slightly convoluted setup.

My Stereo Speakers (bookshelves) also doubles up as fronts for HT. Am able to do that because of two features;
My Amp supports HT bypass.
My AVR has front preout Option.
Currently the my Subs are wired direct off the Amp via speaker level connections.
The Active Sub's filter are set with its own inbuilt Amp; This allows me to use the 2 Ch Stereo with subs (2.2 ch) without the need to turn on the AVR.
only grouse being i cannot really highpass the Front Speakers and they will try to play frequencies outside their comfort zone. Which is still fine, since the LF content in the music i play at the volumes i hear is not a matter of concern

Issue is when i am using the AVR. Because i have not used the preout of the sub, it doesn't detect the sub and doesn't allow me to High pass my Front speakers. So sending in full range signals the speakers. Unlike Music, movies have lot of LF content and even at moderately high volumes, the front speakers are caught off guard ! I foresee that very high volumes of unfiltered content can damage small speakers easily.
However i am very happy with the current state of tune and blend of sub + speakers of my front stage.
If i have to use the AVR, then i have control over the freq getting into my front speakers, however, i cannot use my Stereo setup (2.2) without switching on the AVR ! ! (More components + longer chain is not a desirable position for any audio lover )

Hence asking if there will be a considerable difference if i have to use the AVR's preout for this.
 

yogibear

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For stereo I use speaker level inputs as it gives my subs a flair of tube sound too and actually intergerates well for a 2 way.
 

MaSh

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My bad ! i was under the impression that LFE is a Digital Coax output. Thanks for clarifying. and Yes, basically it boils down to the difference between PreAmp input vs speaker input. I am asking this question since i am running a slightly convoluted setup.

My Stereo Speakers (bookshelves) also doubles up as fronts for HT. Am able to do that because of two features;
My Amp supports HT bypass.
My AVR has front preout Option.
Currently the my Subs are wired direct off the Amp via speaker level connections.
The Active Sub's filter are set with its own inbuilt Amp; This allows me to use the 2 Ch Stereo with subs (2.2 ch) without the need to turn on the AVR.
only grouse being i cannot really highpass the Front Speakers and they will try to play frequencies outside their comfort zone. Which is still fine, since the LF content in the music i play at the volumes i hear is not a matter of concern

Issue is when i am using the AVR. Because i have not used the preout of the sub, it doesn't detect the sub and doesn't allow me to High pass my Front speakers. So sending in full range signals the speakers. Unlike Music, movies have lot of LF content and even at moderately high volumes, the front speakers are caught off guard ! I foresee that very high volumes of unfiltered content can damage small speakers easily.
However i am very happy with the current state of tune and blend of sub + speakers of my front stage.
If i have to use the AVR, then i have control over the freq getting into my front speakers, however, i cannot use my Stereo setup (2.2) without switching on the AVR ! ! (More components + longer chain is not a desirable position for any audio lover )

Hence asking if there will be a considerable difference if i have to use the AVR's preout for this.
Yeh I understand the situation you are in. I am using a similar kinda setup. I have connected my Sub to the AVR for the LFE and bass from the crossover. My speakers are connected to my NAD amp which makes my speakers pump out enough bass for music.

In your case, with receiver not seeing a Sub, is not putting out the LFE signal which like any other signal such as front right or rear left signal.

My suggestion, if your speakers can do 40Hz let them run off the Stereo amp and connect the Sub to the receiver so that while watching movies and loud volumes, the speakers are not pushed hard and all speakers do what they are designed for.

MaSh
 

arj

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What about if you change your AVR setting to have No Sub and the front speakers as full range ? My understanding is that all the low frequencies will be sent to the front speakers.

Anyway am no too much into HT and I only have a basic AVR with a bose 3.1 setup so above is my guess . But since I usually dont have the sub on ,have made my fronts as full range and it seems to work ok.
 

Mi_10

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For stereo I use speaker level inputs as it gives my subs a flair of tube sound too and actually intergerates well for a 2 way.
Exactly what i am feeling too!

Is there no low level inputs and outputs in your sub
Yes they have low level input but no output ! :(

What about if you change your AVR setting to have No Sub and the front speakers as full range ? My understanding is that all the low frequencies will be sent to the front speakers.
This is what is happening, and i dont want full range signals from movies to be sent to my fronts!

My suggestion, if your speakers can do 40Hz let them run off the Stereo amp and connect the Sub to the receiver so that while watching movies and loud volumes, the speakers are not pushed hard and all speakers do what they are designed for.
MaSh
Did the swap today and felt that the sub was lot more natural and blended in with the speaker level inputs. With the AVR's they sound a bit hard, a bit more punchy ! Probably because of the inbuilt filter of AVR (i just set it at LPF 80 Hz; not sure what slope or eq it is applying)

I am also contemplating to use one sub for stereo (via speaker level inputs) and one sub for movies (via AVR's LFE out) to see if can achieve a fine balance . will check that tonight
 
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elangoas

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I am also contemplating to use one sub for stereo (via speaker level inputs) and one sub for movies (via AVR's LFE out) to see if can achieve a fine balance . will check that tonight
How many subs do you have now?..

Did the swap today and felt that the sub was lot more natural and blended in with the speaker level inputs. With the AVR's they sound a bit hard, a bit more punchy ! Probably because of the inbuilt filter of AVR (i just set it at LPF 80 Hz; not sure what slope or eq it is applying)
No idea on the slope.. But EQ?.. Have you engaged Audyssey in your AVR?..

With a stereo amplifier and using speaker level output to sub you will face two issues..

- You will have no idea of the what lowest freq your main speaker is producing (Front L/R), and you will have to do guess work (by ear) on the sub-woofer crossover to align it to mains, which may be incorrect..

- There is every chance that the same freq is being duplicated by mains and subwoofer.. (Between 40 - 80Hz)..

When a sub is used with AVR, there are no such issues as above.. Easiest way to use a sub is with AVR.. More control of bass management.. You also get to set distance of sub from your listening position just like other speakers, which you wont be able to do with stereo amp..
 

Kannan

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Yes they have low level input but no output !
Since you have low level inputs on the subwoofer, why not connect the AVR LFE to it for HT and run it the same way as you doing through speaker-level connections for the stereo amp.
 

ssf

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I feel that it is better to connect the sub to the receiver via the sub out and lfe on the sub and set the crossover to max or override in the sub (In my Velodyne sub its called direct) and set all the crossovers in the AVR. That way, the receiver will have a better control over what goes to the sub and what is sent to the main speakers. The impact of additional electronics in the chain might be less than what you might get with same frequencies being reproduced both by the sub and the main speakers.

If you are connecting the sub via speaker level input, then the recommendation is that you set the crossover frequency in the sub to 10 hrz or so higher than the low frequency spec of your speakers and set the volume of the sub to just where it cannot be heard but will be missed if turned off.

Also, if you have two subs, you might get a much better result connecting both to the receiver and let it bass manage it. You are in a privileged position to try out everything and see for yourself though. :)
 
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Mi_10

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How many subs do you have now?..
2

No idea on the slope.. But EQ?.. Have you engaged Audyssey in your AVR?..
Yes have engaged Audyessey.

Yes i agree on the points you have mentioned when connecting via stereo Amp.


Since you have low level inputs on the subwoofer, why not connect the AVR LFE to it for HT and run it the same way as you doing through speaker-level connections for the stereo amp.
I feel that it is better to connect the sub to the receiver via the sub out and lfe on the sub and set the crossover to max or override in the sub (In my Velodyne sub its called direct) and set all the crossovers in the AVR.
Yeah almost like cascading Filter, but not exactly!
But got your point.

You are in a privileged position to try out everything and see for yourself though. :)
Oh Yes :)

Now experimenting with this option

One sub connected to AVR LFE with XO set at 80 Hz

The Other Sub connected to Stereo Amp with XO set ~55-60 hz.

So the options play this way:
For pure stereo, i dont even touch the AVR, i just play as below;
Sony Bluray -> DAC -> Amp -> Speakers and Sub
reasonably happy with the integration

For HT, i switch on the AVR and put the Amp in HT mode
PS4 -> AVR -> St Amp -> fronts + 1 Sub (XO 60 Hz); AVR Amps -> Rear (HPF 40 Hz) -> Center (HPF 150 Hz) -> Atmos (HPF 120 Hz) -> Sub (LPF 8- Hz)
With this mode, there is protection built for front speakers; Downside is i can only use one Sub during movies, which might be tad underwhelming

With report back with other option soon..
 
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