recent hifi experiance + humming from my sub

Discussion in 'Subwoofers' started by 5tatman, Jan 17, 2008.

  1. 5tatman

    5tatman
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    sub is a recently purchased mj acoustics pro50 mk2 :)smashin:)
    i moved house late november and in doing so my celsetion s10 sub decided to plrrrp. i boxed it in the box it came in moved 10mins down the road then it just started pharting when ever a signal came on. with moving house and my job getting buiser during xmas, i decided to leave it to the new year to sort it out.

    apprently it's a common problem with this sub and a few others that use the same part. £££ to get repaired so i decided that i would go and get a new set of s/s speakers as i had really started missing my hifi sound. walked in to my (relitivly) local superfi to see about the wharfdale diamond 9 package seemed to get good reviews.
    the guy wasn't willing to sell them to me due to me stating i wanted them for hifi purpose as much as films. so he demod a pair of floorstanders with the pro50. it was incredible.i never realised those kind speakers missed so much low end. so he sold me the sub and i promise di'd go back and replace my front speakers with floorstanders when my budget alowed!!!!!

    i'm really enjoying listening to my music again but i am getting a hum fro the sub when i use the coaxil lead from the amp to the sub if i take it out and use the speakon lead it disapears so not sure how to get round this. at presant i'm just using the speakon lead, which is fine for music, but doesn't seem as 'good' when it's not in use for films. i am using a 10m leanth cable and it's as far is can get from the tv etc. any pointers would be great

    list of current hifi/av

    Panasonic 32pl10
    Arcam Alpha 7 cdplayer
    Yamaha DSP AX 750SE
    Panasonic DMR-ES30V
    Celestion avp 305 (minus sub)
    sky+
    MJ Acoustics Pro50 MK2
     
  2. chrisgeary

    chrisgeary
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    ok its either a ground loop or the sub cable's shield is partially broken.

    you can work it out by plugging the sub cable into the sub but not the amp. does it hum? if so, the shield is shot.
    if it only hums when plugged into the amp, its probably a ground loop. try plugging the sub into the same mains socket as the amp (with an extension to test), does the hum go away?
     
  3. 5tatman

    5tatman
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    cheers matey will give it a test later and get back to you.:thumbsup:
     
  4. 5tatman

    5tatman
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    right - as mentioned i have been using the speakon lead for the last week or so. and when i plugged the coaxil back in there was still a hum but very low(quiet), nowwhere near as loud as it was. not sure why ?

    anyway there is definatly a hum there and when i'm listening between the tracks i can still hear it. what lead would you recommend?

    i'm currently usuing an Ixos First XFA01
     
  5. majorwedgy

    majorwedgy
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    hey there,
    I notice you have the same ill fated avp305 package I have - or at least the damned S10 which is in fact a KEF PSW2000. What are the symptoms of your problem? I only ask as I am currently in process of trying to fix mine and should I succeed I will be more than happy to forward the info on to you.

    Cheers

    Ant
     
  6. chrisgeary

    chrisgeary
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    so when you plugged in the phono lead, the hum returned. was it connected to your amp as well?
    does the level of hum change with the gain control for the low level input on your sub?

    do you have any other leads you could try in its place to rule it out?
     
  7. 5tatman

    5tatman
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    hey there,
    I notice you have the same ill fated avp305 package I have - or at least the damned S10 which is in fact a KEF PSW2000. What are the symptoms of your problem? I only ask as I am currently in process of trying to fix mine and should I succeed I will be more than happy to forward the info on to you.


    it's like a very fast loud rumble but noit's not very nice sounding. when you turn it on for the 1st time it does nothing but as soon as you send some sound down it that's when it start and wont stop!!!!


    so when you plugged in the phono lead, the hum returned.
    correct

    was it connected to your amp as well?
    yes and no - the hum was there for both.

    does the level of hum change with the gain control for the low level input on your sub?

    errmm - just went to see and it's not humming? just turned all the units on and off and it's not humming at all!! :confused::clap:

    might see about getting a better/diffrent cabel anyhoo, but yeah no humm

    hmmm just need to sort out the xover points becasue one thing i'm happy then it's too boomy. will see over the weekend and see what i can do.

    are you allowed to upload pictuers on here?
     
  8. 5tatman

    5tatman
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    Just purchased one of these, should be with me tomorrow. should keep the humm at bay :smashin:

    BLACK RHODIUM RHYTHM SUBWOOFER INTERCONNECT 10 M CABLE
     
  9. chrisgeary

    chrisgeary
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    nice work! so maybe it was your gain control then. glad you got to the bottom of it.

    yes you can upload pictures. click on the attachments button and it will give you sizing guidelines.

    xover. usually you'd set the amp to 80hz and disable the sub's crossover. however, most rooms require some sort of tweaking to iron out the worst of room resonance. without an EQ device, you can achieve something by using the sub's crossover and the amps (still at 80hz) if you are lucky that your main or secondary room mode is around that frequency.

    remember, less is more! if you can hear the sub, its probably too loud. if it blends seamlessly, you have it right.
     
  10. 5tatman

    5tatman
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    after reading most of the faq+tips at the the top of this page - (very insightful thanks):thumbsup:

    i would just like someone to confirm i have my stuff set-correctly, and i didn't seem to find too much for when usiing a sub for hifi.

    avp305 freq 90hz+
    Yamaha DSP AX 750SE
    mj sccoustics pro50 mk2

    i have the LF going to the sub from the amp via a coxil lead and the crossover set at 90hz on the amp the LF xover on the sub all the way up.
    speaker size all small

    i have a HF spekon lead connected to the front speaker sockets and the xover on the sub set to aprox 90hz.

    the problem i seem to be having is the bass just seems too boomy when i put the amp on to 'pure mode'. seems great for 5.1 movies but as soon as i stick it on to direct for when i'm listening to music i just can't seem to get the right levels.

    gettign a little peeved but having spent what i did on this set-up and actually having the time to sit and listen now. i want ot get it right. also i hope to replace my front two avps with floor standers in the not too distant future so i want to make sure i've got everythign set-up right as i replace each piece.



    Cheers
     
  11. chrisgeary

    chrisgeary
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    usually when you put an amp into pure direct mode, it ignores the speaker setting size 'small'. the outcome is you get full range bass to your main speakers and your speakon cable feeds the sub. your 90hz crossover is now gone on the amp and you are getting two lots of bass, one from your mains and one from your sub. some subs have two crossover settings, one for the coaxial input (which is normally bypassed) and one for the high level input to address this situation. if you don't have the high level crossover, then i would advise you don't use pure direct or the speakon connection.

    OR you set your main speakers to large and use the crossover on the sub. personally i'd do the former. usually you connect dvd players, cd players etc using their digital outputs (if your amp has good DACs) so the bass management process tends not to affect the final presentation. unlike using analogue sources which then have to undergo a DA to AD conversion when doing bass management.
     
  12. 5tatman

    5tatman
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    this is what i thought happened as the words pure and direct meant to me that there was no processing at all. it sent the full range to the front speakers, as the sub is also wired to the front it takes a full range signal, you then use the subs xover to find the cut off point.

    mine has the 2 seperate inputs, line levels and xovers

    I have been doing the former:thumbsup:

    my cd player (arcam alpha 7) is connected to the amp with analouge interconnects my dvd with a digital. i thought as i was using the amp in 'pure' mode for hifi, that if i used a digital lead it would cause the amp to do more processing, than an analogue lead, thus it being not so pure.!!!! am i missing something here:confused:
     
  13. 5tatman

    5tatman
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    i think i've sussed me boom out during the hifi bit....


    i think the line level at the sub end was too high. it wasn't up a huge amont only about 9'oclock, (starts at 7) but i've since turned it down a little adjusted the xover a little and i seem to be getting there.

    my mate is coming over later to sit a listen whilst i twiddle me knobs !!:nono: saves me getting up and down. he has a fairly good ear for sound so shouldn't be too bad.

    will report back :)
     
  14. chrisgeary

    chrisgeary
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    yeah it helps to have another pair of hands.

    as you know, digital media has to be converted to analogue somewhere. whether you do this in the cd player (and use its analogue outputs) or in the amp depends on which sounds best to you. if the amp is worth its salt, its DA process will be post bass management and not subject the audio to any unneccessary extra conversion steps. I've used my processor to do DA for years now because I want bass management full time and EQ for room correction. Using high level isnt an option for me. the fact that you want to use pure mode and your arcam's analogue outputs is just as valid as my approach.

    i was going to suggest that you adjust the crossover down a bit on the high level input, but you're already there :)
     

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