filtered or unfiltered input

[bkuttemplon]

Which is the difference between the filtered and the unfiltered input? I have a Yamaha RX-V496 that includes a LFE output, but I’m not sure if this signal is filtered or not. In which input do I have to connect the output? If the answer is unfiltered, do I have to use a Y to connect both inputs (left and right)???

Best regards,

[nascarmann]

The Yammie is filtered.....just run cable to the unfiltered in on the sub....

[jgido759]

My Yamaha RX-V595 is filtered at 90Hz. Works well with my PSW350 connected to the filtered input and the crossover knob set to max.

[nascarmann]

Works well with my PSW350 connected to the filtered input and the crossover knob set to max.

Why would you want to double filter? I dunno.....just don't seam right to me.....

[weavercr]

Double filtered??? maybe to avoid peaks in the 90 to 45 hz range from the mains

[nascarmann]

maybe to avoid peaks in the 90 to 45 hz range from the mains

OK.....help me out with an explanation?

[scottvamp]

"Double filtering"
It is a major "GOOF" in the HT subwoofer business. If you use the lfe (the way DD is intended) there is not really a choose. I just read an artical about it in the Q and A section of one of my new HT mag's.
Some of the new subwoofers on the market have taken the steps to have a bypass for there internal crossover. This should have been done from the beginning.
The purpose of most recievers having a filtered lfe was an effort to stream line DD and make it "easyer" to setup.
All of my sub's are "Double filtered" but they still kick A$$.;)

[mantis]

Its a common mistake,
crossover in the receiver and crossover in the sub.
Yamaha has a non adjustable point at 90hz,even there brand new rxz1 can't be changed,I feel Yamaha needs to get on the ball and put an adjustable crossover in there receivers.For better control over the system.
You can get around it and use the sub's,just run left and right pre outs and crossover the sub where it blends the best.
In Yamaha's setup menus, you can send LFE to the mains.
So thats cool.

[jgido759]

I was unaware that I was "double-filtering" using this connection method. The Yamaha manual tells me to connect the LFE OUT (which is filtered) to the LFE IN on the sub. The Polk manual for the PSW350 says that the LFE IN connection accepts a filtered signal from the source (This is NOT Polk's recommended set-up). The suggestion to turn the crossover knob to "Max" was the general opinion on many of the message boards on the net to avoid "double-filtering".

Forgive me if I an wrong, but I always thought that an LFE IN connection on a subwoofer was not affected by the sub's internal crossover and that the "Line Level" inputs used the sub's crossover.

[danger boy]

okay. do some receivers feed a full LFE output? or are all LFE outputs from the receiver filtered? I can't find any info about my Marantz SR5000 about the LFE being filtered.

[scottvamp]

My understanding is that most ARE filtered and no most reciever manuals do not go into any detail about it.

[RBreak]

I was under the impression that the LFE was a discreet, seperate signal consisting of only very low frequency sounds (under approx. 80Htz) anyway, thereby not really needing any high frequency filtering. If you only send the LFE signal to the sub, a filter at either end (receiver or sub) seems unnecessary. Filtering on the sub (using the subs built in adjustable filter) would only be necessary if you wired the sub in a way that was sending it a full range signal (line level from the main speaker pre-outs maybe). This is of course dealing with a 5.1 or 6.1 dvd, if you were listening to 2 channel music (stereo), or using a VCR, or just a T.V. signal, then the receiver would have to filter the low signals itself and send them out to the sub through the LFE line. It would also have to use it's filter to send the low signals from any channel you specified as "small". This is where it would be good if the receiver's manual were clear as to where it's filtering point was. My receiver (Denon) gives me the option of filtering at 80, 100, or 120 Htz., but I'm not sure about Marantz or some of the others. I'm still fairly new to all this so I could be missing some things, most of what I have learned has come from reading (and hopefully understanding right) from this group here at the polk forum.

[nascarmann]

I was under the impression that the LFE was a discreet, seperate signal consisting of only very low frequency sounds (under approx. 80Htz) anyway, thereby not really needing any high frequency filtering.

Yes that's right........the receiver has ALREADY "filtered" the signal..........

[RBreak]

Yes that's right........the receiver has ALREADY "filtered" the signal

So what your saying is that the LFE (the .1 in 5.1 or 6.1) on a DVD is not a pre-mastered signal containing only low frequencies, but rather a signal that contains higher frequencies also (like what is sent to the mains?) that the receiver has to filter? If that is the case, then the same DVD would have a different LFE output, and therefore sound different, from one receiver to another depending on where the receiver's filter is set. I understand that you can use the receivers filter to control where the mains, center, and surrounds cut off at, but I didn't think this affected the LFE signal being sent to the sub. I was thinking the LFE was low frequencies pre-determined by whoever digitally mastered the audio on the DVD, and coming from the DVD not needing to be filtered by the receiver (the signal wouldn't have any frequencies high enough to need filtering). Hmmmm.

[GuitarheadCA]

Also, you need to consider Bass management into the picture. In a 5.1 system, bass is not as easy as the .1 track into the sub. There also has to be both high and low pass filters involved to route the bass IN to the sub. In this case the low pass filter in the reciever becomes very neccesary.

[Dr. Spec]

RBreak:

You are correct about the LFE signal. It only contains "pre-mastered" low bass, and does not require filtering.

The only filtering done by the receiver is when you select your speaker size and/or x-over point. If you select small (and set your sub to yes), it routes bass from the center, mains, and surrounds to the subwoofer below a certain frequency (usually 80 Hz but it varies and is also adjustable on some receivers). The sub will also get the LFE channel. This is the most common HT configuration with passive (i.e., unpowered) mains, and a powered subwoofer.

If you select large for your speaker size (and set your sub to yes), none of the low bass present in the mains, center, and surrounds channels is routed to the sub. The sub only gets the LFE channel. Unless you are running full range speakers in your center, surrounds, and mains which are all capable of handling and delivering deep bass with authority, the large setting is not recommended for most HT applications.

If you select large for your speaker size (and set your sub to no), none of the low bass present in the mains, center, and surrounds channels is routed to the sub. In addition, the mains will also receive the LFE signal. No signal at all will be sent to the sub in this configuration. This configuration is only appropriate if you have no sub at all and awesome mains with really robust powered subwoofers (the RT3000p comes to mind). This configuration is also appropriate if you are connecting to your sub with "speaker level" inputs (i.e., speaker wire from the mains), and you are manually selecting your x-over at the sub - in this configuration, the receiver does not filter anything, so you must do it at the sub.

As far as double filtering goes, if the sub has a dedicated LFE input, this always bypasses the sub's internal x-over filter, to avoid "double filtering". That is why the LFE input jack on the sub is labeled "Unfiltered". If you are plugged into the LFE input jack on the sub, adjusting the sub's x-over filter will have no effect whatsover.

If your sub does not have a dedicated LFE input jack, and only L/R RCA inputs and/or speaker level inputs, THEN you have to worry about double filtering (unless the sub has a defeatable x-over filter switch). If you are connecting to the L or R RCA input or the speaker level inputs, select the highest x-over available on the sub, so it will not "filter again" the already filtered signal from the receiver. This is assuming you have already selected small for your speaker size and have a x-over to the sub at around 80Hz.

Doc

[RBreak]

Dr. SPec,
Thanks for clarifying, it sounds like I had it right about the LFE. I was pretty sure I was right, but when Nascarmann wrote that the receiver "filtered" the signal, in effect creating the LFE, it confused me a little. I think what he really meant was that the receiver "directed" the LFE signal to the sub from the audio source, not creating it by filtering. Thanks again.