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Bass Management - Am I mad to think it should work?

Discussion in 'AV Receivers & Amplifiers' started by Easybourne, Apr 25, 2005.

  1. Easybourne

    Easybourne
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    Hi Chaps,

    I Have a long and convoluted query, please bear with me!

    I have a Yamaha DSP A5, Mission 780s, 78C, 77DS and REL Q150 sub.

    I have a bass management issue.

    With all speakers set to small, and bass out set set to sub, I am missing a lot of bass I think should be there.

    If I change my mains to Large, bass is routed from the other channels correctly to the sub.

    I thought this was just a "characteristic" until I borrowed a copy of Digital Video Essentials. When playing the bass management test tones section I found that bass was correctly sent to the sub when a single channel was playing; but when the "Half-Left or Half-Right" tones were played, bass would all-but disappear from the sub. If I then changed the main speakers to large, the bass would be correctly routed to the sub.

    The best way to explain it is: bass that is half way between two channels is lost - bass that is present in a single channel only is correctly routed. But when main speakers are set to large, all bass appears correctly routed.

    I've checked, and I'm certain that nothing is out of phase. But, I don't want to have to run my mains as large, because I've already had to replace their drivers!

    Does this sound familliar to anyone?

    My worry is that this is something in the specification of the average bass management circuit and I'm stuck with front speakers as large. But, if my amp is indeed at fault what would you reccommend to me as a suitable match for my speakers and sub?


    Thanks in advance!
     
  2. SBanga

    SBanga
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    Don't know if it's the same on your Yamaha as mine, but when set to SWFR on mine, it sounds awful too. Do you not have a BOTH setting from the Bass Out menu?? This seems to work perfectly on my amp.
     
  3. Easybourne

    Easybourne
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    Thanks for the reply,
    I'm not sure about using the BOTH setting as I'd rather avoid setting the mains as large. Do you set mains as large or small using this setting? - the manual is unclear as to whether the bass routing is affected by the large or small setting when SW is set to BOTH.

    When you said yours sounds awful when set to SWFR; in what respect? Too light on bass? Or too much?

    Entirely subjective, of course!

    Thanks


    Darren
     
  4. Jase

    Jase
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    The Half Left, Half Right test tones on DVE are to make sure the imaging is correct on your system. It's not a bass management test as such. Ideally, all tones should read 75db on a sound meter so you get almost perfect surround sound imaging. If all speakers are set to small and all bass is sent to the sub you shouldn't get any output from the sub with any of those tones (including front left, centre etc) if your bass management is working correctly. The only time the sub should work is when you play the 40-80hz tone.
     
  5. Jase

    Jase
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    Just to add. If your speakers are set to small then you shouldn't get the option to send the bass to Both. That option should only appear if your speakers are set to Large.
     
  6. Easybourne

    Easybourne
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    Hi Jase,

    These were specific bass management tones (noise that includes low frequencies below 80? Hz) these are on the disc to specifically test the bass management. Put your ear to the sub when playing them, you'll hear it.
    Another way to explain the problem is: I play a CD in stereo with mains set to small I get plenty of bass through the sub. If I switch to ProLogic - most of the bass disappears. If I them switch mains to large while still in PL, I get plenty of bass again.

    Something is going awry somewhere.

    The question is whether the amp or the bass management specification generally is wrong?
     
  7. Jase

    Jase
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    Are you using the correct tones? You should be using the 5.1 (or 6.1 if you have an EX setup) Band Limited Pink Noise tones in the Reference Materials section. My sub is silent when using these, which is as it should be otherwise the sound meter will be picking up on the sub as well and throwing the readings out.
     
  8. Easybourne

    Easybourne
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    Hi Jase,

    Not being picky or anything -

    I'm talking about the tones in the bass management/system response section - these AREN'T band limited - they are full range and specifically for the purpose of testing bass management.

    I can't remember exactly where they are on the DVD (I only borrowed it), but they are there - probably buried somewhere in DVE's appallingly designed menus, but they are there!

    Anyway, question is why is there no re-routed bass from half-left or half-right positions when main speakers are set to small?

    I've checked, re-checked and triple-checked, can anyone help?


    Thanks everyone
     
  9. Jase

    Jase
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    DVE has different tones, Band Limited Pink Noise, Full Band Pink Noise, Bass Management Test sweeps etc etc. I'd assume you were using the Full Band Pink Noise as only those and the Band Limited Pink Noise have tones for Half Left, Half Right etc.

    The tones are effectively a split between the two speakers either side of it eg Half Left is a mix of the Left and Centre speakers working together to produce a phantom tone. As to why there's no bass when the speakers are set to small, bass to sub, I'd assume it's something to do with that. Maybe the bass management can't cope with it because they're not dedicated channels. Bit strange really.
     
  10. Easybourne

    Easybourne
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    Yes it is a bit strange - counter to how you think it should work.

    This is what I can't figure out! It can reproduce bass that's split between two channels when listening in stereo with speakers set to small, so why not when you switch surround on.

    Do you think it's just my amp, or does your amp lose the bass from the "halfway" positions as well?

    Once you notice something like this, it quickly becomes infuriatingly personal!

    Thanks,

    Darren
     
  11. Jase

    Jase
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    I've not tried the Full Band Pink Noise on my system as I've always used the Band Limited Pink Noise tones for setting up the channel levels. I don't think your system is wrong, it's just that it's not expecting to have to do bass management on phantom test tones. It's setup to deal with re-routing bass from Front Left, Centre, Front Right etc.

    Don't happen to have the AVIA setup disc do you? That has some excellent test tones on it to make sure your bass management is working as it should. It has tests that include alternating Sub Level/Front Left, Sub Level/Centre, Sub Level/Front Right etc etc as well as Low Frequency Pink Noise that pans around the five main speakers. :)
     
  12. Jase

    Jase
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    Did some testing last night with DVE. All speakers set to small, all bass to sub, crossover on the amp set to Fixed THX (80hz). Basically shot my phantom imaging theory out the window. :oops:

    I tried both the Dolby and DTS tones on both the 5.1 and 6.1 tests. With the Band Limited Pink Noise tones the sub wasn't active on any of the tests until the 40-80hz tone. For the Full Band Limited Pink Noise tones the sub was active for all the tones. The only time the sub level dropped off slightly was between Front Right and Surround Right on the Dolby test. This was fine on the DTS test but it dropped off between Surround Left and Front Left instead. I'll check this again with AVIA later as it maybe a glitch in my system's bass management.

    Did discover a couple of odd things for the Dolby 6.1 test. I use a power amp for the five main channels so switched it off to hear the sub easier on the tones. When the test tone between Front Right and Surround Right played I got some pink noise out of the Surround Back Right speaker. This also happened on the test tone for the Surround Right only speaker but the pink noise from the Surround Back Right was louder. Same thing happened on the tones for Surround Left & between the Surround Left and Front Left. Pretty sure this shouldn't be happening. The DTS tones were correct, no bleed from any channels into the Surround Backs.

    So I'm now on a mission to find out if the Tones are duff or my Dolby EX decoding has a problem. Serves me right for playing about! LOL :suicide:
     
  13. kit1cat

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    Hi,

    I may of missed some thing here, but I use to own a Yamaha DSP A5 amp and it only surported Dolby Digial 5.1, no 6.1 or Dolby EX decoding. Could this explain your problem?

    Barry
     
  14. Easybourne

    Easybourne
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    Thanks for looking at that Jase,

    I think you can see what I'm getting at now. No bass redirected to sub in Half-Left or Half-Right positions. The weird thing is, when I switch the Mains to large, the bass is properly directed to the sub and front speakers as you'd expect. But I don't want to use my fronts set to large...

    Am I expecting too much from the bass management circuit or what?!

    Looks like I may need to get a new amp, but I want to be sure that the Bass management is all in order - got any ideas?

    Thanks for looking in to this, much aprreciated!


    Darren
     
  15. Jase

    Jase
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    No worries.:) It's a bit of a strange problem to have. Can you doublecheck it again just to be sure? Might be worth having a word with Yamaha and see what they think??

    Bass Management varies from system to system, some offer a fixed crossover, others have multiple choices, others have multiple choices per speaker etc etc etc. It has improved over the years. As for a new Amp, what sort of budget are you looking at? There's plenty of decent Amps around now.
     
  16. Easybourne

    Easybourne
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    It is a strange problem to have. I did try emailing yamaha a while back, but got no joy.

    As for a budget, I suppose £300 - £500 would be about what I'd want to spend - the difficulty I have is being sure that the bass management issue won't be a problem. It may be a bit much to test it fully before purchase. It would take fairly extensive testing (not to mention patient staff) to find out in a demo situation.

    I guess what I'm trying to get at is whether my particular problem is just with my current amp or with equivalent amps generally.

    As for replacement amps, do you think I should avaoid Yamaha? I like the basic sound of my amp - but if all Yams implement their bass management in a similar way, I should perhaps look elswhere.

    Hmmmm...
     
  17. Jase

    Jase
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    I don't think you should avoid Yamaha as the newer models are much more flexible with their options. With the older models you're stuck with a fixed crossover of 90hz when you set all speakers to small and that's it. Personally I like Denon gear and their bass management options and they've always done well in technical tests that go into their bass management in terms of distortion and whether things are doing what they should. THX certified Amps are also worth checking out as they have to adhere to pretty strict rules with regards to bass management. You'd probably need to look at older models or opt for 2nd hand though.

    For new gear, a proper dealer should let you spend as much time as you need to when it comes to demoing a unit. Although it shouldn't take too long to spin up DVE and check out the test tones etc. :)
     
  18. Easybourne

    Easybourne
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    Thanks for your help and advice.

    I'll try to explain just how vital good bass management is to my better half, cross my fingers and brace for impact.

    Cheers once again.


    Darren
     
  19. missionman

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    Don't worry about this too much. Dolby EX derives the Back channels from matrix encoded analogue data inserted in Pro-Logic format into the Front Centre channel. Therefore a test tone appearing between front and rear may also have some out-of-phase info appearing in the centre which will come out of the Back channel. How loud this is will depend on the accuracy of the matrix decoder in your amplifier. A really good amp will have fine tuned the matrix decoder to reduce such spuriae below audibility compared to the 'wanted' sound.

    You won't hear this in DTS because the DTS channels are all digital discrete.

    Mr Mission
     
  20. Jase

    Jase
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    I'd understand this if the signal format was DTS ES Discrete but the DTS tones on DVE aren't, they're DTS ES Matrix. This is what's confusing me. DTS ES Matrix processing has no bleed at all into the Surround Back channels when the Surround Left or Right test tones are playing. It only happens for Dolby EX. If it happened on both Dolby EX & DTS ES (Matrix) then I wouldn't be too fussed about it to be honest.
     
  21. Easybourne

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    Sorry chaps, but my query was to do with bass management on a 5.1 amp, not 6.1

    The bass drop outs were more noticeable on the front 'half-front-left and half-front-right positions, but probably in the surrounds as well.

    The best way to explain the problem is to give this as an example:

    If I play a STEREO source such as a bass-heavy CD - in stereo only - with the mains set to small and bass out to SW, I get to right amount of bass set to the sub.
    If I switch the amp to ProLogic, the bass sent to the sub is DRAMATICALLY reduced, and the whole thing sounds emasculated. If I then leave the amp in ProLogic, but switch the mains to LARGE, the bass sent to the sub is approximately the same as it was in STEREO mode with the mains set as small.

    In discrete 5.1 sources, bass sounds OK with mains as small, but better when set to large, though this probably due to the .1 channel.

    The problem seems to be when bass is shared between more than one channel - almost as if there is a phasing issue. This phasing issue appears to be within the decoder/bass management circuit more than in the wiring of my speakers as I've checked and re-checked this.

    Does this make any sense?


    Darren
     
  22. Jase

    Jase
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    I can set mine to 5.1, 6.1 or 7.1. I ran the test tones in 5.1 mode as well and got the same results in terms of bass management. :)
     
  23. dazed&confused

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    Hi.

    I didn't really follow much of this as it was all rather technical. Howver I do have a query abot the post which syas one shouldn't have the "bass out: both" option with front speakers set to "small". I thought this was exactly the set up I do have on my Yamaha amplifier (DSP-AX750SE). Am I mistaken?
     
  24. Easybourne

    Easybourne
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    The whole Both/SW/Main issue for bass out is not very well explained by Yamaha's manual.

    It makes sense that all bass for the front left and right is sent to both the sub and mains when mains are set to LARGE. The redirected bass from centre and rear channels is also sent to the sub along with the .1 channel.

    What the manual doesn't say is where the bass from the mains goes if you set them to SMALL and bass out to both - surely there's not much point setting them to small and then telling the bass management to send the bass to them anyway. You'd think the amp shouldn't allow you to set mains as small and bass out to both, but it does.

    Methinks Yamaha need to work on their Bass management policies , their manuals or both!
     
  25. Jase

    Jase
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    Just downloaded a Yamaha manual (DSP AX750) for a look at the bass management options. Does appear strange that you can select BOTH as an option for the LFE/BASS OUT when the front speakers are set to small.

    If it were me I'd set all speakers to Small and route all bass to SWFR and set the Amp's crossover to 80hz (if the crossover is adjustable). Or if you have a pair of floorstanders or front speakers that have decent bass output, set the front left and right to Large, all others to Small and route the bass to BOTH.
     
  26. Easybourne

    Easybourne
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    It looks like we've come full circle! We are in agreement over what should be the best way to set up the amp. I'm now 100% certain that the amp is no good. Thanks for your input chaps!

    To sum up
    My amp presents me with this dilema:

    Set all speakers to small and bass out to sub and lose out on a lot of bass resulting in a very luacklustre and thin performance.

    or

    Sets mains to large, get a better sound and risk popping the drivers again.

    or

    Spend
     
  27. Jase

    Jase
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    Just an afterthought. If you set the speakers to Small and then select LFE/BASS OUTPUT as BOTH have you checked that it doesn't automatically default the front left and right speakers back to Large?

    Out of interest what mode have you set your Rel to? If you're using the standard phono input connection it should be set to mode 2 or 4.
     
  28. Easybourne

    Easybourne
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    Yes, if I have mains set to small and bass out to both, it does appear that the mains get fed a full-range signal. Seems a bit daft that the amp doesn't say they are large in this case - the display will tell you they are small, when clearly they aren't.

    The REL is set to position 2.

    I did have it wired with both high and low level inputs, but I want to get away from running the fronts as large , so now I've changed it to being fed only from the amp.

    Can I ask: if you play a bassy CD in stereo with speakers small, bass out to SW and then switch to pro-logic, would you expect the bass from the sub to remain approximately the same. Am I missing something?
     
  29. dazed&confused

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    Hi sorry to hijack the origin of the thread with my own question but reading this post has got me a bit worried.

    On my Yamaha 100 watt per channel DSP AX750SE amplifier, I have my front speakers (75 watt Castle Compact; "overall frequency range", according to Castle, being 80HZ to 40Khz) set to 'small' because I thought this would protect them. I have my Castle subwoofer crossover turned up full on the speaker itself (in according with the amplifier instruction's advice) and the crossover on the amplifier set at 80Hz.

    However I also have bass out set to 'both' rather than to 'subwoofer' (this is actually the default setting and using this setting doesn't alter the setting of the spekaer size by the way).

    Am I risking damaging my speakers by doing this?

    I don't know if this makes any difference to the whole equation, but even though the fronts are 8 ohm, I have to have the amp on the '4 ohm' setting because the centre is only 6 ohm.

    Any advice would be great.

    Thanks.
     
  30. Easybourne

    Easybourne
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    If your amp behaves like mine, then yes, even though the mains are set to small, if you set the bass out to BOTH, bass for the main channels is sent to the sub AND the mains. However, if your amp's bass management works as it should, then you should set bass out to SUB in order to keep the mains running as if they are small.

    This is very counter-intuative if you ask me.

    As a Yamaha owner, could you tell me if there is a bass drop off when switching between stereo and Pro-Logic when listening to a bass heavy CD with bass out set to SW and all other channels set to small.

    I use the pro-logic example as this is easier to hear what's happening to bass that should be directed to the sub.

    I would assume that you should be getting about the same amount of bass from the sub as you would in stereo - this is where mine seems to fail.


    Thanks for your help.
     

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