Q150 hums!

Discussion in 'Home Cinema Speakers' started by Jon Weaver, Dec 7, 2001.

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  1. Jon Weaver

    Jon Weaver
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    I installed my Q150 last night and am VERY happy.

    This evening my girlfriend kept looking out of the window and complained of "a car running outside".

    She said that she heard this last night too.

    We finally pinpointed the source of the noise.. It was the sub.. Its constantly generating a low frequency hum. Its not very loud, but very noticable.. But as its a VERY low frequency, its hard to hear..

    But once you switch the sub off, you know it was there..

    Even with teh cables remove (except the mains) it still does it and the controls has no effect.

    I really hope that my unit is fault and I can get it replaced.. But if its a general problem, there is no way that I can live with it.

    Its not like I can switch if off when its not in use as its located behind the TV and totally unaccessable.

    Can any other Q150 users confirm that they DONT get this.

    I am not happy now!!!!!
     
  2. Stuart Wright

    Stuart Wright
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    Sounds like a mains earth loop. Search for previous posts containing 'humming', 'earth loop' and such.
     
  3. Jon Weaver

    Jon Weaver
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    I would but the search facility is not working on this site, is it?

    When people talk about 'earth loop', do they mean a problem with the electrics in the house, or within the device?
     
  4. Jon Weaver

    Jon Weaver
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    OK. So the search facility works now.

    I did a search and found people with similar problems.. But there is a MAJOR difference.

    My sub hums with NO CABLES CONNECTED to it.

    I have even turned off my entire system, unplugged it and plugged the sub into a socket on its own (still with no cables connected) and it still happens.

    I am very hopeful that I am just unlucky and have a faulty unit.
     
  5. Stuart Wright

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    Sounds faulty then
     
  6. Ian J

    Ian J
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    Jon,

    My Q Bass makes no noise whatsoever except that which it is supposed to make so I presume that yours must have a fault.

    Bit of a pain when it is tucked away like that.
     
  7. Timmie Boy

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    Just bought mine yesterday and yes I get that humming sound too! BUT only when the switch is selected to Slam mode. Select depth and it goes away. Jon, you've got me thinking whether there is a fault! It is noticeable when you are fairly close by.
    Might go back to Sevenoaks and ask whether their demo model does the same.
    I'll let you know what I find.
     
  8. Stuart Wright

    Stuart Wright
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    You should never use slam mode. IMO.
     
  9. Timmie Boy

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    Spectre,
    Why not use the Slam mode? If its there it must have a purpose. Its no good saying never use it unless you've got a very good reason.
    After paying 500 quid I want all the features to work.
     
  10. Jon Weaver

    Jon Weaver
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    Mine is definatly worse in 'slam' mode, but there is still a hum in 'depth' mode too.

    Whilst its quieter, late at night, you can definatly hear it.

    If it was only coming from the PSU, then I would say that its normal.. But the fact that it comes from the driver makes it worse..

    Its not loud enought to hear all the time.. But when its quiet, it starts to annoy me until I have to switch it off..

    I am worried that 'Timmy Boy' has the same problem.. Perhaps REL have a bad batch?
     
  11. Jon Weaver

    Jon Weaver
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    REL have a solution.. I think (I hope) that they might be right.

    In the past, all boxes were 'earthed'

    However, in a home-cinema setup, its common for the sub to be some distance from the amp.

    Now, if the Amp AND Sub are earthed and are a fair distance appart, you can get an 'earth loop' which will make the sub hum.

    So, REL decided to 'double insulate' their products and remove the earth.

    This will stop 'earth loops'.. BUT!

    Around the same time, ALL manufactuers started doing this too.

    So, in a modern system, its very likely that your system will have NO earths! (Like mine)

    REL have recommended that I earth my kit and they are sure that this will solve the problem.

    My fingers are crossed!!
     
  12. Skid Solo

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    When you say 'earth my kit' do you mean only the REL Sub or your amp as well, I think from the contents of your post your are talking about the sub only.

    I will give this a try as I am expericing exactly the same probelm, one thing I have noticed however is that if I am playing a movie in either Dolby Digital or DTS then I the hum disappears, I think becuase there is a singal from the amp at this point. What I also notice is that the hum reduces when the amp is turned off.
     
  13. Jon Weaver

    Jon Weaver
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    Because all the devices are connected together by phono leads, what ever you earth, will pass on the 'common' earth to all the other devices.

    So, in theory, you could earth the Sub, and then when the amp is connected to the sub, it would be earthed too.

    But the best solution is to earth the amp, because its the central point of your system.
     
  14. Skid Solo

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    Okay, I understand the theory of earthing the AMP, however on Denon 3802 (which I have) there is a 2 core cable attached to the amp and thus no earth is present, in the cable.

    I do not really want to start taking apart an amp that is only a week old to install and earth cable, if there is such a earth point within the amp anyway.

    Are you using a seperate cable to earth the body (casing) of the amp ?
     
  15. Jon Weaver

    Jon Weaver
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    I should have said that what you want to avoid is having several devices earthed at un-common points.

    So, if like me your DVD,CD, AMP and Sub isn't earthed, then choose ONE to earth (amp in my case).

    But if your amp is already earthed, then don't start earthing everything else, or you will get loops and that will make things worse.
     
  16. Timmie Boy

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    Just hang on a minute. After paying out 500 quid you've got to modify your own kit to get it to work? REL are having a laugh.
    I'm disappointed with REL even the manual is a total disgrace. They use the same manual for all the Q models. The diagrams are appalling. Most cinema amps have only the one LFE output, the manual dosen't even show this, it presumes you have 2 outputs for the sub.
    You would think after shelling out all that money you would get a nice glossy colour manual.
    There is no methodical process of setting the sub up. Just huge long paragraphs of technical jargon
    I phoned REL and they recognise the characteristic hum of the 150 (they won't tell you its a fault) REL blame the other manufactures for going double insulated on their amps!!! In future they are going to build an earth switch to get round the problem of the hum. What a joke!
    Taking my 150 back to Sevenoaks and try something else.
     
  17. Skid Solo

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    Last night tried the sub both with and without and earth connections, made no difference to the hum. Sounds like a different sub may be the answer.

    What I have however noticed is that the hum is worse when the amp is turned on and when in pro-logic II or stereo, the hum (and I dont really know how to describe this) pulses, which is more annoying than just a constant hum.

    Any other suggestions for resolving this would be gratefully appreciated.
     
  18. Jon Weaver

    Jon Weaver
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    Its not good.. The Earth has definatly helped.. When I connect it directly to the Sub, the hum went away (or so I thought).

    The same was true when i connected it to the amp.

    I was well chuffed and explained to my other half that it was fixed.. An hour later, she started complaining of a rumbling again.

    To be honest, I really couldn't hear anything, but when I unplugged the sub, I could tell that something was there.

    There was one definative test which is to use the spectrum analyser which I have for the PC.

    It produced some interesting graphs.

    I want to stress that the amplitudes quoted here are not calibrated, as the microphone was right in front of the sub, everything was constant duing my test, so they can all be referenced together.

    With the sub off, I had a bunch of 'noise' around 0-50hz.. Which you would expect.

    But when I switched it on, I saw signals at EXACTLY 50 hz intervals!

    50, 100, 150, 200, 250, 300, 350, 400, and 450!

    There was nothing in between.. Just spikes on the graph at these frequencies.

    However the amount and strength of these signals was different under each test:

    Un-Earhed, Depth Mode

    50hz -30db
    100hz -35db
    150hz -40db
    200hz -40db
    250hz -35db
    300hz -50db
    350hz -45db
    400hz -55db
    450hz -50db


    Earthed, Depth Mode

    50hz -20db
    100hz -40db
    150hz 0
    200hz -55db
    250hz -55db
    300hz -50db
    350hz 0
    400hz 0
    450hz 0

    So with the amp earthed, the higher frequencies reduced/disappeared.. But there is a larger 50hz signal!

    Un-Earthed, Slam Mode

    50hz -20db
    100hz -20db
    150hz -30db
    200hz -40db
    250hz -40db
    300hz -50db
    350hz -50db
    400hz -55db
    450hz -55db

    Earthed, Slam Mode

    50hz -20db
    100hz -40db
    150hz -45db
    200hz -50db
    250hz -40db
    300hz -55db
    350hz 0
    400hz 0
    450hz 0
    500hz 0

    Again, the earh has cleaned things up, but there is a larger signal at 50hz..



    This would all explain why, when the system is earthed, the hum disappears (audiably), but you can still feel it.


    There is clearly something wrong with my sub, and the fact that 2 others have reported the same, makes me think that they have a general problem.

    I have no choice but to send the sub back... Which is a shame, as I am REALLY impressed!
     
  19. Skid Solo

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    Tried an experiment last night, not to the detail that Jon managed, but wanted to confirm somehting to myslef. Using a sound pressure meter the Sub is set to 76db as per the test tone from 3802, as are all other speakers.

    With the amp turned off, but the sub turned on, the noise level from the sub was 59db (measured 1" from the front mesh)

    With the amp turned on and PLII selected but the volume set low, but not off the noise level from the sub was 68db, this sound however was a hum rather than sounds generated by PLII

    With amp turned on, but the volume muted, the noise level from the sub was 59db again.

    I tried this also with a different sub (from my old Sony pro logic system) and got similar results, althought the hum was not a noticable from the Sony sub.

    This leads me to belive that :
    The REL Sub is working better than the Sony one, which is a good thing.
    There must be a single from the 3802 when the volume is above zero.
    Therefore the problem either lies with the amp or the compatability of the amp with the sub
    Or is there a problem with my cable, it does touch earthed metal at one point during its route from the Sub to the Amp, perhaps this is a probelm ?
     
  20. Jon Weaver

    Jon Weaver
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    I don't know what happened to my post.. I definatly typed a reply.

    I was bascially saying that REL have said that they have tested a Q150/200 in their factory and can hear a slight hum.

    However, in a mail today, they said that this should go away if there is a connection from the amp and a decent earth.

    But in may case, even with an earth and connection, there is still a slight hum.

    They are actually looking into the cause, but I don't know whether this means that it will be fixed.

    Hopefully, they will find the problem, fix it and produce a new revision of the Q150.

    I am going to do some 'blind' listening tests tonight to be sure if that I CAN hear the hum.

    What was funny, was that I went to 'Severn Oaks' to look for a replacement.

    The 'boy' there told me that my hum was caused by "Bad Mains".. Even when I explained that REL have seen the problem and believe it to be a design fault, he told me that "REL have bad mains too.. Transformers hum worse when you have bad mains and this is what I am hearing".. I wouldn't even expect this kind of talk from Dixons!! I almost punched him!!

    I am really hopeful that REL do look at this problem and do fix it... Maybe I am just being fussy, but I can't believe that a sub can actually produce a 50hz hum.. Not one which costs £500.

    Even my £150 Yamaha makes a sliught hum, but thats a transformer noise (which you get with all electrical kit) and does't come out of the speaker.
     
  21. Jon Weaver

    Jon Weaver
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    I spoke with REL again yesterday and they have confirmed that they can hear a hum from their Q150/Q200s.

    But they argue that its so quiet, that they are surprised that you can hear it.

    Maybe they are right? I am going to do some 'blind' listening tests tonight to be absolutely sure if I can hear it.

    They implied that they will try and fix the problem.. But I don't know whether this means they will fix it in a future release of the Q150, or a future model...

    What was funny was that I went to Severn Oaks to see what I could buy instead..

    I told the guy about my problems and he butted in and said that I had "Bad Mains".. I explained that REL have confirmed the problem at their end, and was told "They have bad mains too".

    I almost walked out!!

    I checked my old Yamaha sub and that 'hums' too, but its a transformer hum which doesn't come out of the driver.. A few colleageus also checked theirs and confirmed the same..

    I don't know what to do now.. I love the sub.. I want to keep it, but I can't live with the hum.

    Earthing the WHOLE system at ONE point (and only one) has definatly helped.. But its still not perfect..

    As people have said before.. For £500, you should expect perfection!!
     
  22. Jon Weaver

    Jon Weaver
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    Oh.. There it is.. But my 2nd reply came before the first one.. Sorry to repeat the same thing twice.
     
  23. Skid Solo

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    I haven't actually contacted REL, but I will do so, also when I first purchased the unit from Sevenoaks and suggested there was a problem, there response was that it was an earthing problem also.
    Don't know how to improve the earth connection in my house, but what I might try is putting the sub power plug into the same socket as the amp power as I read somewhere the problem is caused by the earth in two sockets not being the same (not sure I belive this).
     
  24. Jon Weaver

    Jon Weaver
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    Do me a favour and don't mention that I told you about the earth, or about the fact that you have read about my problem.


    I seem to have built up a good relationship with REL over the past few days but I am not sure if they will apprecaite the fact that I broadcast this problem on this forum.

    But I am not sorry about doing that... I spent a lot of money on this sub and I want what i payed for.. But I would prefer that REL get a number of unrelated queries about a the hum problem.
     
  25. Skid Solo

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    Jon,

    I have already spoken to REL and I did not mention the fact that I had been in any communication over a forum, for exactly the same reason as you stated.

    I also found them very helpful and hopefully between us we can get resolution to this problem.

    I will let you know if I manage to solve this problem, with there suggestions yesterday I managed to reduce the hum by around 4db, may not sound much but it did make a big difference to hjow noticeable it was.
     
  26. Jon Weaver

    Jon Weaver
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    What suggestions did they give you?

    Did they mention that they had heard about this from other sources?

    With regards to your earth problem... As default the sub isn't earthed, and its possible that you amp isn't either.

    So, moving connetion to another mains socket won't make any difference..

    With your hum reduced by 4db, is it now acceptable to you?

    I was at home at lunch time, and I couldn't hear the hum.. But I have do doubt that later on tonight, when it quite and I am relaxing, I will be able to feel/hear it.
     
  27. Skid Solo

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    Jon,

    REL did confirm that there seemed to be some problems with a hum from the Q150.

    The suggested resolution was again to earth the sub (as none of my system is earthed), which I did by conecting the outer connection of the 0db input connecter to earth (via a 13a plug and socket).

    I look at this as a very tempory resolution.

    With respect to is it acceptable to me, it probably would have been, however as I know its there I can still just about hear it, but I still get a pulse noise from the sub during PLII and stereo, even without a source. If I put a sound pressure meter in front of the sub, although I cannot see the difference in actual db, as the pulse emits from the sub, the bar at the bottom of the spl moves up and down 1 diviion, so it is there is a rythmic/pulse theme to the hum on my sub.

    Have you noticed this pulse effect on yours ? as I say turn on the amp select a source on the amp that does not have anything connected and then select either PL or PLII and I can hear a distinct pulse from the sub. You can hear it with a real source connected in either PL or PLII but it is not so noticable as there is a sonds being emmited from the sub anyway.
     
  28. Jon Weaver

    Jon Weaver
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    I too have had the same advice about earthing the Sub, and this sort of worked.

    HOwever, I don't think it worked as well as I originally thought, as now that I have recheck adding/removing the earth does little to the hum in 'depth' mode, but it does make a difference in 'slam' mode.

    I too have heard something like a pulsing, but I am not sure if I am imagining it...

    Whats the frequency of the 'pulse'.. I am sure that I can hear/feel a throbbing sound with around 5 secs betten the pulses.. Is this the same as you...

    What are you doing about the problem over all? Are you going to live with it? Are you optimistic that REL will address the problem?

    My suppler is still going to send a replacement, as REL have advised that in their tests, the sub is TOTALLY silent when there is an earth and amp connection.

    Somehow I don't believe this.. But am going to take a replacement just in case... If that has the same problem, then I don't know what I am going to do.
     
  29. Mike Dando

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    Any more news on this?

    I have just bought a Q150. I had a shop model for a week while my new one was ordered. The shop model was silent. No hum.

    My new Q150 was dead on arrival. Did not work at all, made a very large humming noise and the rear panel went red-hot in 5 minutes.

    My second Q150 works although it has the humming problem. I am in a similar dilemma to others here. Love the sub but cannot live with the hum, and for £500 I dont expect to have to fiddle around with earthing.

    I also agree with someone else here in that the manual is very poor.

    :mad:

    Mike.
     
  30. fabryuk

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    thought I might join in for a bit of discussion. I noticed that the above only mention Q150, what about Q201, Q200 or evem other model or brand? Is it a common problem with sub or just Q150
     
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