LFE over x-over freq discarded for 1066, 1065, & 1055?

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  • BleakShore
    Member
    • Oct 2003
    • 59

    LFE over x-over freq discarded for 1066, 1065, & 1055?

    I'm told that the BM in the 1066, 1065, & 1055 discards the LFE above the crossover frequency. That is, if you set your speakers small, and chose to set the sub crossover freq at, say, 60 Hz, anything above 60 Hz in the LFE channel is simply discarded.

    Now, this doen't sound like it ought to be this way. One can lose a lot of information. Or do we? Is there much stuff over 60 or 80 Hz in the LFE channel?

    Is throwing sway stuff like this a common practice?
    Is it like this for the 1098?

    I sure hope this can be addressed in the new products. I doubt this can be fixed for the current line. I imagine Rotel chose to implement a single LPF to feed the sub after summing the signals from the small speaker channels and the LFE.

    Aside:
    One feature I like to see added is separate level setting for the LFE channel, and the signal that has been low passed from the small speaker channels. My old SONY had this feature. Although I did not use it, it may be useful as movies nowadays can have incredibel amount of bass energy.

    If you are the sort that likes bass for music listening, and have a tendancy to turn up that sub level, that could result in a rather excessive LFE reproduction when viewing movies.

    Cheers,
  • will1066
    Senior Member
    • Aug 2003
    • 660

    #2
    That's how bass management works. There's both low-pass and high-pass filtering done at the crossover frequency. The filtering is not a brick wall anyway, but rather a gradual slope. You're not losing any information since the speakers are playing it. The sub handles only what you set it to play -- information below 60 Hz. There's nothing that needs fixing.

    The Rotels also have separate level settings for the subwoofer channel. It's in the Sub Setup area of the OSD menus. You can set different levels for Dolby, DTS, Stereo, multichannel input, etc.

    Comment

    • BleakShore
      Member
      • Oct 2003
      • 59

      #3
      Originally posted by will1066
      That's how bass management works. There's both low-pass and high-pass filtering done at the crossover frequency. The filtering is not a brick wall anyway, but rather a gradual slope. You're not losing any information since the speakers are playing it. The sub handles only what you set it to play -- information below 60 Hz. There's nothing that needs fixing.

      The Rotels also have separate level settings for the subwoofer channel. It's in the Sub Setup area of the OSD menus. You can set different levels for Dolby, DTS, Stereo, multichannel input, etc.
      I don't think you understood either of my questions. Please read carefully.

      Yes, I agree the LPF and HPF filters redirect high and low freq contents to the "small" speaker and to the sub. But that is not what I am talking about.

      I am talking about the LFE channel. The sub should always get the full LFE signal (I believe the THX spec is 120 Hz and below?). But by setting the cross-over freq for "small" speakers, the LFE signal is also run through the LPF, resulting in only the spectral contents below the cross-over frequency being reproduced in the sub, and high spectral contents over the cross-over freq is *discarded*. I know this - Rotel responded so as such.

      For the 5 channels, that is front, center, and the surrounds, the sub gets the redirected low ends and speakers get the high ends. Nothing is lost. That is what the BM is supposed to do, and Rotel does it correctly. I hope you see the difference?


      Secondly, I am also aware of the options in OSD for different LFE setting levels for different modes. But That is not what I am taling about. What I am talking about is being able to mix the LFE signal and the redirected bass signal at different levels relative to each other. For example, currently, I suspect, that the LFE signal and redirected bass from the "small" speakers are mixed at equal levels, i.e., the signal power ratio between the two are 0 dB. I'd like to see the ability to suppress/boost the LFE by, say 3 dB, relative to the redirected bass from the "small" speakers. It is a different concept. What is in OSD is surressing/boosting the bass level in the sub which applies equally to the LFE and redirected bass for different modes of viewing. See the difference?

      Regards,

      Comment

      • SomaJoe
        Member
        • Jul 2003
        • 56

        #4
        Bleak, you are correct. The BM really should not be filtering the LFE channel. I'm not sure what the 1098 does, but the easiest solution I found for my 1066 was purchasing an Outlaw ICBM unit (and also having the resistor cut fix). I set all my speakers to large in the 1066. The LFE channel passes through unchanged, the other 5 channels bass signals are summed (each with a separate crossover) and you can set the relative levels of the mixed LFE and summed bass like you want.

        -joe




        Joe's HT
        Joe's HT

        Comment

        • BleakShore
          Member
          • Oct 2003
          • 59

          #5
          Ahh.. Thank you. Nice to be understood.

          Thank you, too, for pointing out the Outlaw ICBM. Will look into it.

          All I was thinking was that it would've been really nice 1) if Rotel did this to begin with, and 2) if they could release a firmware fix if do-able.

          Regards,

          Comment

          • will1066
            Senior Member
            • Aug 2003
            • 660

            #6
            Yes, I see what you're saying now. My apologies, Bleak. You do pose an interesting question. If indeed true, it's then surprising that Rotel would LPF the LFE, which should be completely discrete and go untouched.

            On your second point, what you're asking for is specialized and probably beyond the processing power of those Rotels - and many commercial processors for that matter. I don't think the 1098 is even able to do what you're asking.

            Plus, please read this, which basically explains the way discrete LFE and bass from the surround channels are mixed into the subwoofer signal. This is taken from a Secrets article:

            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. This does NOT mean we should be striving to emulate the cinema sound system setup!

            Despite the stigma in the cinema that 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, one subwoofer system. 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 and those that do only allow it to be attenuated as a measure of protection for subwoofers that can't handle the full meal deal.

            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 which as we said is pre-set to play 10 dB higher will come along for the ride at the right level. 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.

            Comment

            • BleakShore
              Member
              • Oct 2003
              • 59

              #7
              Originally posted by will1066
              Yes, I see what you're saying now. My apologies, Bleak. You do pose an interesting question. If indeed true, it's then surprising that Rotel would LPF the LFE, which should be completely discrete and go untouched.
              Yes. It should be left alone :!:; hence my original post.

              Originally posted by will1066
              On your second point, what you're asking for is specialized and probably beyond the processing power of those Rotels - and many commercial processors for that matter. I don't think the 1098 is even able to do what you're asking.
              My inexpensive Sony STR-DE925 (which I upgraded to 1055/1075 combo) provides this functionality. I guess I should mention that I don't miss this function much, as Rotel provides another effective solution. It was just "why not" thing.


              Regards,

              Comment

              • Andrew Pratt
                Moderator Emeritus
                • Aug 2000
                • 16507

                #8
                As far as I am aware this treatment of the LFE track is part of the Dolby specs and is how most if not all AV processors work. There's a good paper written by someone in the know that I saw recently but I don't currently have the time to track it down...its likely on the secrets site though as I think it was one of those guys that wrote it. I'll try and post it later on.




                Comment

                • Andrew Pratt
                  Moderator Emeritus
                  • Aug 2000
                  • 16507

                  #9
                  here it is...
                  Link




                  Comment

                  • will1066
                    Senior Member
                    • Aug 2003
                    • 660

                    #10
                    Andrew, you need to edit the link. :LOL:

                    Comment

                    • Andrew Pratt
                      Moderator Emeritus
                      • Aug 2000
                      • 16507

                      #11
                      Its not the link its the server software messing up the link.




                      Comment

                      • BleakShore
                        Member
                        • Oct 2003
                        • 59

                        #12
                        Here, I fixed the link:

                        link

                        I'll read and get educated. See what it's got

                        Comment

                        • BleakShore
                          Member
                          • Oct 2003
                          • 59

                          #13
                          Originally posted by Andrew Pratt
                          As far as I am aware this treatment of the LFE track is part of the Dolby specs and is how most if not all AV processors work.
                          Andrew,

                          Thanks for the article. After reading the article, I do not think it is a part of "Dolby specs" to throw away the LFE signal above the cut-off freq. The article states

                          Originally posted by Secrets
                          ...Strictly speaking, any* such processor with a sub/sat crossover frequency set lower than 120 Hz is "discarding" the upper end of the LFE channel. THX units are NOT exempt from this. With the standard THX 80 Hz 4th order crossover, the top of the LFE channel gets chucked.
                          But the good news is (this is part of the answer I was looking for in my original post)

                          Originally posted by Secrets
                          ...THX looked at an inordinate number of modern 5.1 soundtracks and guess what they found in the LFE channel: not much at all in the region of 80 Hz - 120 Hz, making their original choice of 80Hz rather fortuitous.
                          with the caveat
                          Originally posted by Secrets
                          ...Therefore, chucking the top band of the LFE is no big deal but the argument here is that a standard SSP crossover set much lower than 80Hz or so may actually be costing you bass content.
                          So if I have my xover set at 40 Hz (hypothetically), then I'd be chucking LFE signal between 40 Hz to 80 Hz! Which is not good.

                          You've undoubtedly seen the scene where Neo and Trinity detonate the flame bomb in the elevator shaft after the famaous corridor shoot-out scene? When the flame explodes, it throws some extreme low frequency effects. Pretty cool. The point here, though, is that I noticed a varying degree of sound effects depending on how my speakers (small, large) and crossover freqs are set. Which makes me wonder if I am experiencing some of the "chucking" effects.

                          Also, another interesting article:

                          Originally posted by Home Theater Sound
                          ...The majority of processors today either discard, under-power, or over-power bass in the LFE channel either via mistake or trying to save money by keeping the bass-management circuits as simple as possible. Digital bass management done correctly should produce a more consistent and better overall surround-sound presentation for every home theater.

                          SoundStage
                          Please don't get me wrong. I am pretty happy with the Rotel. I just wanted to understand what I got, so I can use it to its full potential as well as avoid pit falls

                          At least I learned there isn't a whole lot going on in between 80 Hz and 120 Hz. Mine is currently set at 60 Hz. Hmm..

                          Cheers,

                          Comment

                          • Mike Hayes
                            Member
                            • Mar 2003
                            • 73

                            #14
                            It will be interesting to see if you perceive a big difference between the 60Hz and 80Hz crossover in terms of lost LFE between 60-80Hz when using the 60Hz crossover. I am also using the 60Hz crossover. It's good to know that not much is lost between 80-120Hz but I've always wondered about the 60-80Hz region. For overall seamlessness, I really like the 60Hz crossover. I am using B&W N805s, an Adire Rava sub, and the 1066/1075 combo. I really like the N805 mids and so, have been willing thus far to compromise a bit with the crossover in terms of the LFE. However, I think I will do some A/B with the 60 and 80Hz crossover and the scene from the Matrix that you referenced just for kicks.

                            Comment

                            • Kevin D
                              Ultra Senior Member
                              • Oct 2002
                              • 4601

                              #15
                              I've got a spectrum analizer on my LFE out.. I'll play some scenes through it with the crossover set at normal sub, speakers large, and 40hz vs 120hz and see if the LFE out is different..

                              Kevin D.

                              Comment

                              • Andrew Pratt
                                Moderator Emeritus
                                • Aug 2000
                                • 16507

                                #16
                                With my Rotels I've always set my speakers to small and used an 80 hz cross over for all HT modes and simply run my mains as large for music with no sub so for me its less of an issue but it is good to know there's not much going on above 80 anyway in the LFE channel. Really we should just drop the LFE channel all together and let the BM do its job.




                                Comment

                                • BleakShore
                                  Member
                                  • Oct 2003
                                  • 59

                                  #17
                                  Mike, as I mentioned I also have mine set at 60 Hz. I like it better there. At 80 Hz, it sounded just a tad "fatter". At 60 Hz, it sounded, to me, a bit tighter and less muggy. Very subtle difference, however. I sat down for about an hour for a few days switching between the two x-over settings. Finally I settled on 60. Of course, I could be hallucinating as it was not a DB testing.

                                  So, if Kevin can do his magic with the spectrum analyzer and perhaps quantify some of our speculations, it would be cool. At least we will be educated.

                                  And, I agree with Andrew, but I guess backward/industry/legacy compatibility kind of gets in the way. DOS, Windows, and TV formats being some of examples. So LFE may be here to stay for quite some time.

                                  Well, it's Saturday, so I am going to forget all this and enjoy a movie or two tonight! :P

                                  Enjoy, everyone!

                                  Comment

                                  • Kevin D
                                    Ultra Senior Member
                                    • Oct 2002
                                    • 4601

                                    #18
                                    All right... Drum roll..........

                                    The crossover settings have NO EFFECT on the LFE output. Regardless of the setting, the LFE out remains virtually unchanged (the slight variances are on account of the pink noise tendancy to fluctuate) The key is to look at the slopes and notice that they are all the same.

                                    The graph shows with all speakers set to large, sub YES, but even turning speakers to small, there was no change in the LFE levels..

                                    Comment

                                    • Andrew Pratt
                                      Moderator Emeritus
                                      • Aug 2000
                                      • 16507

                                      #19
                                      Very interesting!




                                      Comment

                                      • BleakShore
                                        Member
                                        • Oct 2003
                                        • 59

                                        #20
                                        Originally posted by Kevin D
                                        ...The crossover settings have NO EFFECT on the LFE output. Regardless of the setting, the LFE out remains virtually unchanged ...
                                        Wow... this IS interesting. I didn't expect this. Quite puzzling. Your findings show that it really does not matter what freq we set the crossover at. The LFE is down 3 dB at 80Hz. So it looks like it has a fixed 80 Hz LPF filter. Might as well take the sub crossover setting off the OSD? Hmmmm... :huh:

                                        And, to think that all this time, I thought I was hearing a difference when I changed the crossover setting. I swear I heard a difference. Tuh...

                                        Need to digest this. Can you fill us in as to how your test set up was exactly to obtain these curves? It will help us understand the beast better, I am hoping.

                                        Great job and effort though, Kevin.

                                        Regards,

                                        Comment

                                        • Kevin D
                                          Ultra Senior Member
                                          • Oct 2002
                                          • 4601

                                          #21
                                          Test setup is a 1066 feeding a Behringer DSP-8024 unit. It has a spectrum graph that is either mic or input fed.

                                          Test tones were from Avia speaker setup, 5.1 channel tones in sequence with announcements.. The test tone might have a 80hz LPF built into it. Since I technically have another hour to kill tonight, I can pipe a full range pink noise signal into the .1 multi-channel input and see if I see a crossover slope. It might be different circuitry that it goes through, but if there is a LPF on the output, it might show up there too.

                                          I suppose I could run the DVD players built in DD output straight to the Behringer to better analize the .1 tone for a built in slope..

                                          Any one know of another way to get a known full tone out the .1 channel?

                                          And keep in mind the crossover frequency still does have an effect on the LP & HP filters on all the other channels and the bass that gets sent to the sub. Unless all your speakers are set to large, there could be more bass from the channels set to small throwing off your preference tests..

                                          Kevin D.

                                          Comment

                                          • Kevin D
                                            Ultra Senior Member
                                            • Oct 2002
                                            • 4601

                                            #22
                                            Ok, piped through from the DVD players DD .1 output, results are the same (although REALLY LOUD, make sure to turn off your sub amp before you try it). My graph didn't show it, but 31.5hz was down about the same as 80, so the bell curve appears to be built into the test tone, not the sub output..

                                            I can do another test real quick on the Matrix scene, speakers set to large and sub to yes. I'll set peaking bars to on and start at 40hz. If it's doing anything, the peak bars should go up on the higher frequencies as I increase the crossover..

                                            Kevin D.

                                            Comment

                                            • BleakShore
                                              Member
                                              • Oct 2003
                                              • 59

                                              #23
                                              Originally posted by Kevin D
                                              ..The test tone might have a 80hz LPF built into it.
                                              This may explain why all the curves are rolling off at 80 Hz, but it does not explain why it does not roll off at lower freqs. That is, if I set the crossover at 40 Hz, I expect the LFE output down 3 dB at 40 Hz ald being attenuated at 12dB/octave from then on.

                                              Originally posted by Kevin D
                                              ..Since I technically have another hour to kill tonight, ..


                                              Originally posted by Kevin D
                                              And keep in mind the crossover frequency still does have an effect on the LP & HP filters on all the other channels and the bass that gets sent to the sub.
                                              Good point. That explains the sonic difference I am hearing with different crossover settings.

                                              Maybe I will get my lazy butt off the sofa and make some measurements myself, if nothing, for an independant verification. I do need to get a source that will feed a white noise in the .1 channel. I will run the output of the 1055 sub preout into the PC sound card line-in, and use SpectraPlus to see the spectrum. One of these days...

                                              Comment

                                              • Mike Hayes
                                                Member
                                                • Mar 2003
                                                • 73

                                                #24
                                                Just to make sure that I have it straight so far :?

                                                The crossover chosen effects the amount of redirected bass going from the mains, surrounds, and center to the sub but has no effect on the amount of LFE going to the sub? In other words, no matter which crossover is chosen, all of the LFE is sent to the sub so that in effect, no LFE is chucked if you choose a lower crossover setting? But the amount of redirected bass varies with the crossover? This seems like a good thing to me if I am reading this correctly as it means I don't have to worry about losing LFE but rather, can focus on the amount of redirected bass that sounds good to my ears.

                                                Mike

                                                Comment

                                                • Mike Hayes
                                                  Member
                                                  • Mar 2003
                                                  • 73

                                                  #25
                                                  BTW Bleak,

                                                  I am hearing exactly what you are hearing regarding the perceived difference in redirected bass at 60HZ (tighter) 80Hz (fatter). I did some A/Bs with different types of music last night and found that I liked the tighter 60Hz crossover for jazz & classical but liked the fatter 80Hz sound for stuff like Missy Elliott and Bjork. The difference was subtle, as you suggest, but definite to my ears. I really need to check sub output with an SPL meter when changing from 60Hz to 80Hz because I am wondering if I'm hearing/feeling a change in overall sub output when changing crossovers. 80Hz definately seemed heavier/fatter/thicker etc.

                                                  Mike

                                                  Comment

                                                  • Kevin D
                                                    Ultra Senior Member
                                                    • Oct 2002
                                                    • 4601

                                                    #26
                                                    Mike,

                                                    You understand right. The LFE output is not effected at all by the crossover frequency. However, keep in mind, LFE is just the .1 output on DD and DTS sources.

                                                    When you say you hear differences on different types of music, you are probably not listening to DD or DTS sources. Keep in mind that PLII and probably other surround modes utilize full range signals on all channels.

                                                    Even with mains set to large, sub to yes, but rears to small, I get alot of sub output (taken from the rear channels) which is effected by the crossover setting. Everything set to large and sub to yes I get no sub output (unless a digital source).

                                                    I ran through the Matrix scenes with everything set to large, sub yes, and the frequency peaks were all the same on the LFE out, regardless of crossover setting. Surprisingly there was alot of info above 80hz, and even on into 150hz and beyond.

                                                    Kevin D.

                                                    Comment

                                                    • BleakShore
                                                      Member
                                                      • Oct 2003
                                                      • 59

                                                      #27
                                                      Wonder how the spectral contents above 80 was coming through so well when you were testing Matix. According to your pink noise test results, there as a significant attenuation at 150 Hz (almost 20 dB down from 60 Hz).

                                                      But, yes, if xover setting has no effect on the LFE, it is a good thing. As we don't lose anything.

                                                      KevidD wrote:
                                                      .. When you say you hear differences on different types of music, you are probably not listening to DD or DTS sources. Keep in mind that PLII and probably other surround modes utilize full range signals on all channels
                                                      I don't quite get this; for all music source, the sub crossover will redirect the bass to the sub, and send high passed sig to small speakers. So, regardless, changing the sub crossover will make a sonic difference.

                                                      Ya all had a good weekend, I hope?

                                                      I generated some heat on my amp last night.
                                                      Played a lot of my old vynils.. Dave Mason, Little Feat, Cream, Traffic, Allman, Bowie,.... even ABBA

                                                      Hope I didn't scare my neighbors. It was near ear bleeding level.
                                                      Happy to report my ears, the amp, and speakers are all fine and doing well.

                                                      Comment

                                                      • aud19
                                                        Twin Moderator Emeritus
                                                        • Aug 2003
                                                        • 16706

                                                        #28
                                                        Okay...reading all that just made me a little dizzy...lol

                                                        So let's see if this works... If I run my speakers at large and set my crossover to 60Hz:

                                                        -The LFE still get's anything in the LFE signal, below or above 60Hz, plus everything under 60Hz from the other channels?

                                                        -The rest of the channels play everything down to 60Hz sending anything below that to the sub?

                                                        Is this all correct?

                                                        J.R.




                                                        Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide
                                                        Jason

                                                        Comment

                                                        • BleakShore
                                                          Member
                                                          • Oct 2003
                                                          • 59

                                                          #29
                                                          That's right.

                                                          So nofin to worry about, ah hope...

                                                          Comment

                                                          • Kevin D
                                                            Ultra Senior Member
                                                            • Oct 2002
                                                            • 4601

                                                            #30
                                                            Originally posted by aud19
                                                            Okay...reading all that just made me a little dizzy...lol

                                                            So let's see if this works... If I run my speakers at large and set my crossover to 60Hz:

                                                            -The LFE still get's anything in the LFE signal, below or above 60Hz, plus everything under 60Hz from the other channels?

                                                            -The rest of the channels play everything down to 60Hz sending anything below that to the sub?

                                                            Is this all correct?

                                                            J.R.
                                                            If you set them to 'small' you get the above results. Anything set to 'large' will get a full signal with nothing sent to the sub. (unless sub is set to 'max' in which signal below the crossover point will get sent to both the sub and the speaker)

                                                            HTH,

                                                            Kevin D.

                                                            Comment

                                                            • Mike Hayes
                                                              Member
                                                              • Mar 2003
                                                              • 73

                                                              #31
                                                              Just want to clarify, I was listening to redbook CDs via the optical out from a Denon 1600 to the 1066. The 1066 was in 2 Ch mode. All my speakers are set to small. I was jumping back and forth from the 60Hz to the 80Hz crossover and noticed what seemed to be thicker bass at 80Hz with more detailed bass at 60Hz.

                                                              Subsequently, I measured overall sub output via the 1066 test tones at both 60 and 80 and found that overall output increased by 2Db when going to the 80Hz crossover. I reduced the sublevel by -2DB in stereo mode at 80Hz via the sublevel and went back and forth while accounting for the 2Db difference. The crossovers seem very similar when accounting for the difference.

                                                              I took it a step further using the Sound and Vision test disc just to make sure that the 1066 test tones are accurate. The results of the 5 speaker level balance test via the S&V disc were almost identical to the 1066 test tones. However, the sub level via the S&V disc is reading 5DB lower than the 1066 subwoofer test tone! It does not matter if I am using the 60Hz or 80Hz crossover when using the S&V disc - I get the same result - a dramatically lower reading (5DB) as compared to the 1066 tone. Which one should I believe or should I try another disc?

                                                              Comment

                                                              • Mike Hayes
                                                                Member
                                                                • Mar 2003
                                                                • 73

                                                                #32
                                                                Also, I ran the sub level test via the S&V disc for both DD and DTS. The overall sub level output was 5 to 7DB lower depending on whether I was using the 60Hz (about 7DB lower than the 1066 test tone) or 80Hz (about 5DB lower than the 1066 test tone) crossover as compared to the output level of the left main speaker regardless of using the DD or DTS menus via S&V and yet the 1066 test tone would lead one to believe that overal sub output is in balance with the rest of the speakers. Not sure which to believe. :?

                                                                Comment

                                                                • BleakShore
                                                                  Member
                                                                  • Oct 2003
                                                                  • 59

                                                                  #33
                                                                  Mike,

                                                                  I'm glad you are working hard on this!

                                                                  Well, at least the 2 dB difference was consistent in both cases, either using the test tones or the SV disc.

                                                                  Assuming full .1 bandwidth pink noise (or bandpassed white noise from 20 Hz - 120 Hz), the signal bandwidth (bw) getting to the sub at 60 Hz crossover is 40 (=60 - 20) Hz. The signal bw at 80 Hz crossover is 60 Hz. The signal power ratio is the same as the bw ratio (assuming flat power spectrum), so 10 log(60/40) = 1.7 dB. Pretty close to what you have measured (2 dB). So, that's nice.

                                                                  However, I think that although the sub power level went up by ~ 2 dB at 80 Hz crossover, the output power from the small speakers went down (by the same absolute power difference) as they do not get the signal from 60 Hz to 80 Hz. Either way, the overall signal power spectrum remains "flat" (ideally).

                                                                  So, it is my opinion that you should not be making the 2 dB compensation when you are switching the crossover freqs. I think the perceived fatness is due to other parameters than the louder sub level (which should have been compensated by the drop in pwer in small speakers). Like, complex combination of crossover attenuation slopes, driver characteristics, etc. I think, it might be more of a coincedence that you and I are experiencing the same perceived difference. Others may not with different speakers.

                                                                  Now, if the main speakers were set as large, then, by all means, the sub level should be decreased according to the crossover freqs if we were to keep the power constant. This is a different situation in that we are adding a copy of low-passed bass to the main large signals.

                                                                  As for the discrepency between the SV disc and the test tone level, I am at a loss as I do not have the SV disc (I should buy one).

                                                                  Ideas, anyone?

                                                                  Regards,








                                                                  Comment

                                                                  • Mike Hayes
                                                                    Member
                                                                    • Mar 2003
                                                                    • 73

                                                                    #34
                                                                    Wow, what an awesome response, Bleak. I will take your word on it and not try to compensate for the 2Db

                                                                    Has anyone noticed discrepencies with the internal sub test tone on the 1066 or 1055 as opposed to a test disc like S&V, VE, etc.?

                                                                    Comment

                                                                    • aud19
                                                                      Twin Moderator Emeritus
                                                                      • Aug 2003
                                                                      • 16706

                                                                      #35
                                                                      Originally posted by Kevin D
                                                                      Originally posted by aud19
                                                                      Okay...reading all that just made me a little dizzy...lol

                                                                      So let's see if this works... If I run my speakers at large and set my crossover to 60Hz:

                                                                      -The LFE still get's anything in the LFE signal, below or above 60Hz, plus everything under 60Hz from the other channels?

                                                                      -The rest of the channels play everything down to 60Hz sending anything below that to the sub?

                                                                      Is this all correct?

                                                                      J.R.
                                                                      If you set them to 'small' you get the above results. Anything set to 'large' will get a full signal with nothing sent to the sub. (unless sub is set to 'max' in which signal below the crossover point will get sent to both the sub and the speaker)

                                                                      HTH,

                                                                      Kevin D.
                                                                      So if I understand this, with speakers set to large, the crossover becomes useless? I mean if the Sub is receiving the LFE and the speakers are receiving their full signals, then there's no info to crossover, correct? So it basically becomes irrelevant. I could set my crossover at any point with the speakers set to large and should hear absolutey no difference?

                                                                      J.R.




                                                                      Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide
                                                                      Jason

                                                                      Comment

                                                                      • jethro
                                                                        Junior Member
                                                                        • Oct 2003
                                                                        • 4

                                                                        #36
                                                                        I didn't follow the entire thread because I don't know the details of Rotel pre/pro's, however, the Bryston SP-1.7 has the same behaviour as bleakshore described in the first paragraph of the first post. I was surprised to find this out and somewhat disappointed. On the positive side, from what I understand, sound engineers don't normally include a lot of low freq info in the surround speakers, so if you have capable fronts and centers I would set all speakers to large, and set the crossover of the LFE to 120Hz.

                                                                        Comment

                                                                        • aud19
                                                                          Twin Moderator Emeritus
                                                                          • Aug 2003
                                                                          • 16706

                                                                          #37
                                                                          Originally posted by jethro
                                                                          I didn't follow the entire thread because I don't know the details of Rotel pre/pro's, however, the Bryston SP-1.7 has the same behaviour as bleakshore described in the first paragraph of the first post. I was surprised to find this out and somewhat disappointed. On the positive side, from what I understand, sound engineers don't normally include a lot of low freq info in the surround speakers, so if you have capable fronts and centers I would set all speakers to large, and set the crossover of the LFE to 120Hz.
                                                                          Why 120hz? Just a catch all?

                                                                          J.R.




                                                                          Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide
                                                                          Jason

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                                                                          • jethro
                                                                            Junior Member
                                                                            • Oct 2003
                                                                            • 4

                                                                            #38
                                                                            We went thru a similar LFE discussion on the Bryston/PMC discussion group on www.audiocircle.com ("Enhancements to Bass Management in SP-1.7" thread) a while ago. I was very surprised to find out how the LFE channel is handled on the SP-1.7. Anyways, James Tanner of Bryston indicated in the thread that the studios record the .1 channel up to 120 Hz (2nd page, first post on page). I guess you could set your LFE crossover as high as possible, if you are using large settings for all your speakers.

                                                                            Comment

                                                                            • aud19
                                                                              Twin Moderator Emeritus
                                                                              • Aug 2003
                                                                              • 16706

                                                                              #39
                                                                              Isn't the 100-120Hz range where humans start having bass localization issues too? Not to mention that your sub may lose some of it's deep bass capabilities if being asked to also play above say 80-100Hz at the same time?

                                                                              J.R.




                                                                              Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide
                                                                              Jason

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                                                                              • BleakShore
                                                                                Member
                                                                                • Oct 2003
                                                                                • 59

                                                                                #40
                                                                                Many sub/sat speaker manufactures say that below 120 Hz or so, we lose localization. IIMHO, this claim is marketing driven. Speaker manufacturerors who sell a bass unit (commonly and much errorneously a "sub") with tiny satellite speakers like B_se must claim that a speaker system like that won't lose any musical "goodness". That's what I think.

                                                                                But I remember reading a few articles that the frequency below which we lose localization is actually much lower than that. Below 60 Hz - 80 Hz range is what I vaguely recall. Maybe even lower.

                                                                                Comment

                                                                                • jethro
                                                                                  Junior Member
                                                                                  • Oct 2003
                                                                                  • 4

                                                                                  #41
                                                                                  The Dolby Labs website has a document http://www.dolby.com/tech/c.in.0011.LFE.pdf that says the LFE channel contains information < 120 Hz. As far as localization go, perhaps more than one LFE speaker is required - I need to learn some more.

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