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Crossover Question and Servo 15

Discussion in 'Home Cinema Speakers' started by Stewart C, Oct 9, 2002.

  1. Stewart C

    Stewart C
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    Strange one this.

    I bought the Servo 15 a couple of weeks ago now without the X30 crossover. The subwoofer has been performing tremendously well in it's LFE mode but I was getting a poor music performance and what seemed like an over bearing bass sound.

    My AV Amplifier was set to THX Fixed crossover and I was hoping that 80Hz and below was being fed to the subwoofer. I calibrated the test tone to 75-78dbs so everything was ok.

    As I said the sound just was not right. I then borrowed an X30 crossover from one of the nice people on the AVForum (it really is a wonderful place to get help and information). The transformation was amazing. I set the crossover to 80Hz on the sub's X30 controller and all of a sudden I had lost the overbearing and quite frankly unattractive bass to a note that I was familiar with, with my M&K subwoofer.

    What should I set the X30 to becuase as as far as I can see this is essential for me, however I really didn't think I would have needed it considering my Amplifier has a crossover built in. Others don't seem to need it.

    All I can think of is the fact that the THX crossover did not work but my amp has a variable crossover at 80Hz which may work without the X30. I need to try that before buying an X 30.

    I am not sure what is happening to the sound at all.

    What would be the ultimate setting using the X30 and amplifier setting without the X30.

    Thanks
     
  2. Jase

    Jase
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    Hi

    Only thing I can suggest is just trying the different crossovers, on the amp and also playing with the X30.

    Could be down to the crossover itself, there are varying types from what I gather, each with different characteristics, fast rolloff etc. Need someone with more technical knowledge than me though to explain it all!

    For what its worth I use the Fixed THX crossover on my amp and the sub crossover is bypassed. Works very well for me.
     
  3. Stewart C

    Stewart C
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    Yeah but without the X30 controller the Servo has no crossover.
     
  4. Jase

    Jase
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    Your amp has different crossover settings so try that first, if there´s no joy then you´ll have to get yourself an X30.
     
  5. Lowrider

    Lowrider
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    Do you have all speakers as small, and bass to sub only ?
     
  6. JohnS

    JohnS
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    Hi Stewart

    I've been struggling with my servo15 also, same sort of problem which is overbearing bass. I was lucky enough to get an x30 when irecieved my sub but have finally reached some settings that are ok without it.

    My amp for info is a Sony 940 which you can set the crossovers with speakers set to small at either 60, 90, or 120. I've comprosed on 60 for my main and rears (celecstion C3's which go down to about 42hz) and 90 for the centre (C4c which goes down to about 75hz). the dial on the servo 15 is set about 60, dolby lfe on the amp to -3 and subwoofer on the amp to +9.

    I've got to be honest and say that I haven't quite worked out what difference adjusting each of the above parameters does to each part of the sound but I did download some sin-waves and an excel spreadsheet which I got from http://www.snapbug.ws/bfd.htm which was discussed on this forum a while ago. What i found by running the tests is that you could turn something down and increase the volume of the bass at certain frquencies:confused: but by spending all day plotting graphs at various setting I managed to find the best compromise which for me was the settings I posted above. Not scientific but I've managed a result I'm reasonable happy with.

    Not wishing to hijack Stewart's thread but I'd be grateful if someone could explain what I've been adjusting and why.:confused: I can't be the only one that doesn't know:blush:
     
  7. Lowrider

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    You should switch off the xover in the servo, or set it to the maximum...

    Setting it to 60hz you will loose some info from the center channel, up to 90db, plus the .1 (lfe) that goes up to 120hz...
     
  8. JohnS

    JohnS
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    Lowrider

    Are you sure its a croosover control on the servo15, I was under the impresssion that it was volume related and the 60 is just a value, not a crossover point?
     
  9. Lowrider

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    I don´t know your sub, my sugestions are general, but as you said 60, I assumed it was a xover freq setting, if it is volume, then forget what I said... :blush:
     
  10. Couch Potato

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    John,

    Try PM'ing Nic Rhodes or SteveEX, they're the resident Servo experts, Nic's got 2 of them and Steve's got 4 :eek:

    I dont think either of them use the X30.

    For what its worth, I think the dial at the back is a "volume" control, set this inb the middle and use the "Sub level and crossover" in your amp to fine tune and callibrate.

    I spent at least 2 days playing sine waves and plotting graphs until I got happy.

    Also bear in mind you could have a room resonance issue with certain freq's creating a "room induced" boom. Ways around this are to move the sub or use room treatments ie diffusors/abfusors/absorber etc or get a parametric equaliser like the Behringer feedback destroyer about £100. That was my last route and I've now got 16-80hz +/-5dB :D

    Hope this is of some help.

    Steve
     
  11. Nic Rhodes

    Nic Rhodes
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    Stewart

    I have been thinking on this one over the weekend. To be honest I am a bit confused by it all. All I can come up with is:

    X30 filter is a third order slopes for high pass and low pass. Denon filtering is likely to be 24 dB/Octave if it is like my Tag. So if your crossover in receiver is set to say 50 Hz it should be -6 dB at 50 Hz and -24 dB at 100 Hz. [THX expected rate of 12 dB/octave typical for a sealed box below resonance]. The first may be far more beneficial to you?

    I have noticed that some Denon receivers were less than good at sub redirection / filtering. Basically making a mess of it. This has also been reported by Miller in HiFi Choice. I do not know you model however other than reputation so can’t comment on it’s performance (many will however, despite never even seeing a product!). Could it be that it it is not performing as advertised. It would not be the first time Denon has done this!

    How about the Denon ‘modes’, Stereo, Stereo + sub, Direct, Direct + sub. Are these getting mixed up and sending sub info to both L and R and sub? The Denon ignores your speaker settings when in Direct mode and sends full range signals to the front left & right channels. It also has subwoofer output which might be the cause of the confusion as when you use the X30, the Denon thinks you have no sub.

    Any further on?
     
  12. Stewart C

    Stewart C
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    I don't understand what the 24bd/octave information is all about. Maybe someone can enlighten me.

    My M&K sub has a variable switch and a Bypass switch for a THX controller which I have, I just set it to bypass and the M&K sub outputs 80Hz and down, without any problem.

    The Servo without the X30 does not seem to 'understand' this signal and as I reported earlier gives an unnatural and heavy bass. The X30 has cleaned the bass up alot but maybe now sounds a tad light.

    ARGHHHHHHHHHHH. I am tearing my hair out.

    To the Beekeeper. Do you use the X30 controller in your system or is your TAG doing what my denon does and sit at fixed THX crossover straight into your Servo 15? If you do use the X30 what are your X30 settings.

    Thanks for your help guys.

    Regards
     
  13. Nic Rhodes

    Nic Rhodes
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    I have found the X30 is redundant with my Tag equipment. It added nothing but the Tag is good at this bass thing. With a Denon 10se (friends) and 3802 (borrowed) I prefered the X30. When I put distortion meters on the output, levels were high on LFE with the settings we used (mixture of large and small settings). The X30 got around this limitation.
     
  14. Stewart C

    Stewart C
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    Thanks for that. I think I have come to the conclusion that I need the X 30.

    To the person who allowed me to borrow their X 30 for a couple of weeks. I will return to you as soon as possible (I haven't forgotten). It has been a great help.

    Thanks again.

    Regards
     

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