Double Filtering Sub Consept (IMO)

scottvamp

This double filtering is getting me.

I am still trying to understand this concept.
I understand why people would think this but I think it is not really happening.
Sort of saying that people are getting a double crossover.
I am talking about running powered subs out of the recievers LFE output. Why would this be double filtering? This is the way the HT industry intended it to be. Almost all powered subs have a built in crossover and some a varable--hence a subwoofer not a full range speaker. The LFE out on a reciever is not a full blown crossover signal. It is a dedicated track on a DD DVD (5.*1*).
It is sent from your DVD through the processer in your reciever and sent to the LFE output. There is no crossover converting it. It is a direct signal specifically made for low bass effects. Your sub then gets the signal and plays it. May seem like a double filter but I think we are confusing it with having a double (crossover) .I looked in my Onkyo manual and other manual specs and they never mention a certain freq. crossover for the LFE.
I have my PSW1200 --my two rt1000's-- and my rear sub all hooked to the LFE output in parallel. Useing Monster Bass cable with Monster Y's on the front and rear subs using both left and right inputs on the sub's. It sounds amazing. I can adjust freq.'s on the sub's.
Is there a better way to do this?
I have been wrong before but this is my theory and it works.
I do not notice any problems with this setup. The bass is clean and accurate. Works well with music and movies even DSP'S. I have experimented and have not found a better way yet. Any input on this subject would be appreciated.:)

goingganzo

your lfe is set to a certan f aka 80 hz and down the cross over on your sub is for if you feed a full range sigonal to it but if you are using your lfe you turn your sub to full range.

sgtgto

Hi:

Nothing wrong with your setup that I can see. A sub does not have a left and a right, to my understanding. It has a dual voice coil, thus the two inputs. My Denon 4802 has a variable crossover for the lfe out and my sub also has a variable crossover. Nothing wrong with that. Set the lfe on my receiver where I want it and I set the crossover on the sub where I want. No problem, loads of base, can only have sub volumn at around 11 oclock.

I have Polk RT2000s for front, CS400 center, FX300i for rear, and Infinity BU2 sub. Denon 4802 receiver, B&K 200W X 3 to power front, and a lot of other equipment. Sound is awesome.


Gary

trubluluc

My question would be:

Do all LFE signals have the same frequency response? What is it? 88..120..?
Say it is a standard.
Then it would come to the receiver.
Some receivers can adjust the signal, or filter it to a specific frequency. Some fix it at say 88.
If you can pass the signal through your receiver at the same frequency it arrived I would say it is unfiltered.
The signal heads to your sub. My sub (psw450) has an unfiltered jack in, which I use.
It also has a limiter (filter) that can adjust the signal.
I have it set all the way up, because my yamaha says to do it that way, do the the receiver presetting the level to 88 I think it was.
Subs do a great job of playing bass, but a lousy job of playing music, (so I've been told) so it is best to limit their range to only the sounds your main speakers just reach, or can't reach.

then again I could be wrong.



-luc

CHRIS

Almost every receiver is set at 80Hz on the sub out. Both the lfe out and the sub pre out are fixed at 80Hz unless they are variable. Thanks ‘THX’! If your sub dosen't have a none filtered input, like Luc's 450, then it s filtered again. Read the review of the LSi's!
Now I have my ‘R’ and ‘L’ pre-out going to the ‘R’ and ‘L’ of my sub all speakers set to small except for the fronts and the sub set to NO works great. Of all the ways Polk suggested this worked the best for me. With the crossover set at 40-45Hz since my fronts will go to 32 or 36Hz. When the signal was getting double filtered it was not as clear now it is music is far better also. When I conected the DVD direct it was not right with out a high pass filter which I was useing before, with the signal running through a pre-amp with a high pass, then it did work. The pre is pulling stereo only duty now.
Thanks Scott it is appreciated, buddy!

scottvamp

Thanks for the info. guys-good stuff to know.
What got me on the subject was the review on the LSI's also and the talk here. Thanks again,scott

gidrah

I applaud your bravety for bringing up a subject that has been hinted to on other threads. IMHO, my $.02, etc. are as follows. Your first filter is your one and only filter on any given signal. In the case of subs., if your first filter is set at 80hz(-12db/octave), any subsequent filtering in the <80hz(or so) range doesn't exist and therefore cannot be manipulated and/or distorted by any secondary filter. I haven't come across ANY filters that introduce distortion within their given ranges.

The only problem you might get is if your first filter is higher than your second. This will create a hole of -db. Your first filter (high pass) stops all fq. @ -12db/octave at 80hz. Your 2nd (low pass) stops all fq. above 40hz (KILLER sub). This leaves a hole between 40hz&80hz.

You CANNOT filter and therfore distort any signal that has already been negated by a previous filter. It'd be like hooking up a sub harmonic synth. to your tweeter.

Aaron

I think there's two parts to this: 1) you don't want to muck up your signal by passing the signal through an additional filter and 2) you don't want to create an uneven response. I think the second issue is the more important one and is typically what happens. Most receivers are low-pass filtered around 80Hz. (unless adjustable). This is your first filter and creates a say a -12dB/octave slope in the frequency response. Then the crossover in your sub is set to say 50Hz. So now you have a frequency response slope that's -12dB/octave from 50Hz. to 80Hz., but then the receiver's filter kicks in and your slope gets steeper with a -24dB/octave slope at 80Hz. I would think this uneven roll off would create a frequency response anomaly.

Aaron

RuSsMaN

Don't know about you guys, but the steeper the roll off (esp on the 2 lowest bass octaves), the better, at least how my ears hear it.

Aren't most subs 2nd order, active, 12db/octave or better? At least good subs? I do see the point, of not wanting to 'double filter'...from a simple stance, it seems to me the fewer chokes or caps you have to go through, the better.

Cheers,
Russ

Aaron

Don't know about you guys, but the steeper the roll off (esp on the 2 lowest bass octaves), the better, at least how my ears hear it.

Yeah, but I don't think that's the point. I think the point is that double filtering creates an uneven rolloff. Re-read my post above; I corrected mistakes and clarified a bit.

Aaron

CHRIS

When a receiver is set to ‘NO’ sub it passes the LFE signal to the front ‘L’ & ‘R’. Hook the pre-outs for the fronts up to the sub and set all speakers but the fronts to small, which sends all the LFE signal to the fronts from the surround speakers and NO LFE filter from the receiver it thinks there is no sub. The crossover on the sub is set to 45-50Hz because my fronts will go below 40 Hz and makes a best match up to the sub set there. No slope problems no role of poblems no holes or gaps in the bandwidth. I can't figure were you think there would be gaps between 40-80 Hz, slope, role off problems etc.. The only filter being used is the subs, in this case. It sounds great now and the slate works great too.

scottvamp

Chris, what main speakers do you own? I asume that they are Polk's with powered subs. You should be getting a FULL freq. response to your main speakers subs with your setup. Verses maybe not as much bass in a standard 5.1 setup. But if you are chooseing NO for sub on your reciever ---how are you getting a signal to your seperate sub? I use the LEF output for ALL my subs. It works well with ALL video and sound formats. You would be missing out on all the LFE intended for DVD's and other comparable formats.

Aaron

Chris:
I understand what you're saying, but there's two problems with that. For one, not all receivers have L&R preouts. The other problem I have with using the L&R preouts is that you're forcing your mains to try to deliver all their channel's bass plus the LFE. While this configuration will give you the highest bass output, I don't think it is a good idea unless you have monstrous speakers and a good amp or a powered tower. If it's a passive speaker, I think you would be sacrificing some overall sound quality (e.g. midrange clarity) by forcing the speaker to reproduce so much bass. The other really big problem I have with this configuration is that it doesn't give you as good of control over the bass volume in DD. For example, during a movie I typically turn the subwoofer's volume up for greater dynamics (I think this is fairly typical). However, if you're using the L&R preouts to feed the sub, when you turn the sub's bass up not only are you turning up the LFE bass, but also the L&R bass. This results in an overemphasis of the bass in those channels. It can be quite annoying sometimes when things are boomy that aren't supposed to be.

Scott:
If you set your L&R speakers to LARGE and subwoofer to OFF, the LFE channel and all bass from speakers set to SMALL will be redirected to the L&R channels. Thus if you wire your sub to the L&R preouts it will get all the typical subout bass plus the bass from the L&R channels.

Aaron

scottvamp

Ya, that makes cents but why would you want to do that in a Dolby Digital setup? That is what I was getting to.

sgtgto

Guys:

I'll say it again. There is NO left and right on a singular sub. The two inputs are for a dual voice coil speaker. Also, if you set your receiver lfe out crossover to 80Hz and then set your sub to say, 50Hz all that is happening is your receiver only passes low frequencies from 80Hz down and your sub will only be active on frequencies 50Hz down. Simple as that.


Gary:p

Aaron

I'll say it again. There is NO left and right on a singular sub. The two inputs are for a dual voice coil speaker

Nobody has disputed this point.

Also, if you set your receiver lfe out crossover to 80Hz and then set your sub to say, 50Hz all that is happening is your receiver only passes low frequencies from 80Hz down and your sub will only be active on frequencies 50Hz down. Simple as that.

While I don't claim to be an expert in this particular area, I believe that you are incorrect.

Aaron

ntculenuff

scottvamp..i own a onkyo rcvr (777) and your right there is nothing in the manual about the lfe being crossed over, so i emailed onkyo and asked the ?, and yes the lfe is crossed over at 80hz..i assume that yours is probaly to.
best way to check is play with your sub crossover, turn it up pass 80hz and you will notice that there is no really no change in the bass as you would notice a difference if it was getting a full range signal

the whole issue with using pre outs vs lfe..
use both buy a second sub..i did sounds great
my setup:
mains: rt800's- large
center: cs350ls- small
surround: rt f/x- small
lfe: definitive 12" psw-sub crossover turned all the way up (rcvr lfe crossed over @ 80hz) gain about 1 o'clock
2nd psw: definitive 10" connected to the L&R pre-out on rcvr-sub crossover set @ 120-125hz gain @ 12 o'clock

CHRIS

This is it is one of Polk's recomendations. I don't think they are wrong. I have 2 pair of Monitor 12 series 2 fronts powered by Adcom GFA-555Mk IIs, bridged, through the pre-outs which have ‘Y’ conectors as to Polk's recomendations again. With each having 4-6 1/2s making 16 total for the front, the mids are very detailed. What got me thinking this way and reading sub setup again was in the LSi review Paul was going to set them up this way but did not have time. Polk has added quit a bit of info to the sub section since I was last there several new types of hookup recomendations.
You guys make sub hookup much harder then it really is, you just need to find the right setup for your system.
Any info on this will tell you double filtering is not good. If your happy with the way your system sounds going through two filters, however you have them set is all that counts. No matter where you have them crossed it is still 2 filters. All Onkyo receivers are set at 80 Hz as with most other receivers unless you can set the crossover. This is a THX recomendation not thinking subs are crossed I would guess. That part maes no sence to me or why the makers do this.

Aaron-You can't make a speaker handel more then it can or over load them. This is where their crossover comes in. Think when it was just 2 channel stereos, all the signal went to the speakers but you only heard what they cold play. You didn't over load them that is impossible unless it is wattage, to much or to little. Same thing here they get all the signal and the subs take over where they drop off which is around 40 Hz. I did not say all receivers have pre-outs, I have been talking about mine, and how it is hooked up now. The whole point is to send all the info to the fronts so the subs get all the info. I also don't change speaker or sub volume alone, they are set. I will turn up or down the whole system. I don't mess with the sub once the system is calibrated or setup how ever you want to call it. It was set to 85 Hz with an SPL and there they stay.:)
If I sounded like I was mad or had an attitude in this post I didn't. I was just trying to answer the possed questions or saying what I wanted to get accrossed in the post. All meant to be taken in the best of ways and no hurt feeings!:)

TrappedUnder Ice

very interesting thread indeed!
I have thr Rt2000i's and a velodyne CT150
I have my CT of the sub out put of my yammie..and full wired the 2000's. my CT150 is cut on its xover at 60hz and the sound is great.... Most subs sound nasty at 80hz...if you ask me!

Aaron

You can't make a speaker handel more then it can or over load them. This is where their crossover comes in.

The crossovers in your configuration are not limiting the bass to your mains at all. You're feeding them the full-rage L&R channels plus the LFE channel.

Think when it was just 2 channel stereos, all the signal went to the speakers but you only heard what they cold play. You didn't over load them that is impossible unless it is wattage, to much or to little. Same thing here they get all the signal and the subs take over where they drop off which is around 40 Hz.

I understand that, but you're missing the point. Let me explain it a different way. Say your mains a small bookshelf speakers. Now, if you feed them a full-range signal they obviously won't be producing anything usable under 50Hz. So in your explanation that's not a problem, because the sub will take over at that point. The problem, though, is you're still forcing the speaker to produce those frequencies, and it will, albiet at an inaudible level. You're also sapping a lot of extra amplifier power trying to produce these frequencies. Because the drivers are producing these frequencies and using more power, you will experience an overall degredation of sound, often times noted as a muddying of the midrage. You also won't be able to drive your speakers as loudly, either.

I also don't change speaker or sub volume alone, they are set. I will turn up or down the whole system. I don't mess with the sub once the system is calibrated or setup how ever you want to call it. It was set to 85 Hz with an SPL and there they stay.:)

See, I like to have separate control of my LFE bass and my L&R bass. I have settings marked for music and movies. I generally juice the bass a bit on movies.

I guess the point I'm trying to make here is there is currently no ideal sub hookup option. The ideal option would be if a receiver had an unfiltered sub out. Maybe there is a receiver or preamp/processor that has one of these. If so, that's the way to go.

Aaron

johnnyamerika

To be honest I haven't experimented too much on this stuff. I've hooked up subs via the LFE and via front speakers, and really haven't noticed too much difference. I have kind of an odd setup, with 1000is as 'large' mains, a 400i as a 'small' center, and two JBL 4310b's as 'large' surrounds. I've been debating hooking up the LFE way, right now I'm using 12AWG as a jumper on the 1000is.

My only guess is that if companies like Onkyo and Denon make their recievers with x'overs at 80 Hz, they do it for a reason. Especially since even the high end models have it. Common sense would tell me that the have a good reason for doing this. It would be interesting to find out 'why'!

Since no one here has had experience with a reciever w/o the 80hz x'over (unless someone stands up!) how do we know that freq. above this value will be beneficial for the subs at all? I'm more curious than anything!

CHRIS

Aaron you are wrong, sorry to say. You can't hurt change the quality characteristics or anything else with any kind of signal you send to them. A speakers crossver will only allow the ability of the speaker to pass through, you can't over load it with a signal that is rediculous. Yes if I'm gonna start pushing so much power they start to clip they won't sound good. Other wise no they don't get muddy even over 100 SPL. Your acting as if the speakes have no crossover of there own and are going to let to much bass or low end though to the drivers, it doesn't work that way. That is why subs are ajustable so you can match them with your speakers at the point were they drop off. So far we hav been talking about my setup. I don't have small book shelf speakers either. I have speakers which will go to 35Hz which is better then the PSW450 and the 650 goes to 28 Hz not far off. I don't think they have a problem handeling any bass coming their way. Hell my M7s go to 40 Hz at their lower limit, that is the same as the PSW250 and they are bookshelf. These aren't the speakers made today which don't go low.
Even if you did have smaller bookshelf speakers it would not happen the crossover in the speaker stops it and you set your sub slightly above were the speaker drops off. Even if the sub were hooked up to the LFE, the speaker if set to large gets the full signal just because you have 4 others sending signal to it dosen't change the equation they are just getting bass from another area. If you set your system to 3 channels or even 2 the fronts get the full signal and the speakers crossover stops anything the speaker can't handel or as you say will make the mids muddy.

Eddie624

Isnt with like THX certified stuff have something to do with that 80 hz. I have read so much stuff the past week or so my brain is about fried.

Aaron

I don't know how else to explain it to you. It sounds like you have a basic misunderstanding of how a crossover works.

Aaron

RuSsMaN

This post needs to DIE!

If your crossover is a BANDPASS design, eg RT3000, the low end bass is limited. Very few speakers incorporate this design.

If you have, say an RT600, just for demo purposes, and I slap in my TELARC cd, and crank a pure 125 watts to them (well within their capabilities) playing 'Jurassic Lunch', you can kiss the voicecoils goodbye. They are now officially siezed. Why, because they were fed a signal they cannot handle (at a certain level of power).

If the XOVER is not a BANDPASS design, (looking at only the woof/midbass here), it will TRY to play whatever it is fed, even if that signal is say 20db down from its F3 resonant freq.

Look at response graphs, for 99% of speakers out there. You don't see a sharp cliff at the -6db down point, it tapers off, some steeper than others.

There is an answer, BIG FAAAKIN MAIN SPEAKERS.

Cheers,
Russ

CHRIS

Exactly Russ same thing I said before to much wattage or to little is the ony way it will but not just a signal. If you push to much wattage no matter what the signal they will freeze up blow tweeters what ever but anything you play has more signal then your speaker can reproduce. I know exactly how crossovers work. Aaron call Polk since they recomend this setup and argue with them. Paul was going to use it in the LSi setup and I use it with mine, it works great. Jeez people would be blowing speakers left and right if just a signal could do it. If what you say is the case if you didn't have a sub you would blow your mains. Iagree this post needs to be shot. I'm done call Polk.

avelanchefan

Ok all I have to say is that I have read this entire post and I feel like I just got out of Triginometry with a little bit of Calc. thrown in. I can rip apart a computer and pu it back together. I can build computers. But now I am starting to get into the audio area and I feel lost.

Good stuff though.:D

scottvamp

I come in peace. My posts half the time end up in crazy fun arguments but I do ask intreging questions and points. I am a HT enthuisust and I have spent many years building and planning my HT setups. My dedicated setup I have now cost me about $20,000. It suits me very well for both Music and Movies. I had a blast building it . Not to mention I probably make less than half the money of many Polksters.
NOW I have also got into aurguments with Aaron and we both made our points and sometimes I may be talking out of my A$$.
BUT the System Showcase was a very exciting thing for me.
I figured time to put your System where your mouth is. With all the for superior knowledge I have heard from people like Russman, Chris(who i agree with alot) and Aaron I have been waiting and ready to see your GOD-LIKE HomeTheater setups.
What is up with that!!!!!!!!!!!!!!!!
THIS IS GOING TO HURT. FIRE AT WILL GUYS!!!!!!:eek:

Aaron

Chris:
You're misinterpretting what I'm saying. We'll leave it at that.

Scott:
My home theater doesn't compare to yours; I can tell you that right now. You know what I have. Does that have any bearing on my knowledge? Nope. Unfortunately I have a more pressing expense right now: college. We won't even get into how much that costs compared to anybody's home theater system.....

Aaron

CHRIS

I think we both are Aaron peace man lets call it a truce. For all I know were saying the same thing but different ways. That is the problem when you are on forums you can't ask a question right back and loose your train of thought, IMO.

Scott-My Polks are in a bedroom system, neither Andrea or myself care to put picturers of our bedroom up on the show case.

Aaron

Who cares about the Polks, man. Bring on your killer system!

Aaron