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HELP!!!! Subwoofer knocks out centre speaker

Discussion in 'Subwoofers' started by compusolve, May 8, 2001.

  1. compusolve

    compusolve
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    Hi

    Can anyone explain to me why my system.

    Denon AVCA1
    B&W HTM Matrix Centre MonoBridged NAD 216THX Driven.
    B&W CDM9NT Mains
    B&W P4 Surrounds
    Pioneer 737 DVD
    Pioneer 925 Laser
    Millenium DTS Decoder
    Cables Nordest Solar Wind

    M&K VX7
    M&K V75 MKII

    Room 25ft Long * 14ftWide

    The V75MKII removes so much detail from the surround experiance especially the centre, The VX7 just sits in a corner and does the job without loss to the centre channel.

    Things I have tried, you may ask why to subs, I started with the VX7 but wanted more oomph so along came the V75, I normally run a sub via the phono input mono left, placement near the front mains in the best bass corner available, the other sub I have been running in the rear off the rear amp output on the Denon.

    I have also tried cabiling via speaker wires to the V75 off the front main bywire connector on the rear of the Denon.

    I have just removed the V75 and left the smaller VX7 in the front off subwoofer output and the sound is controlled and detailled. The new CDM9NT seem to handle a lot of what the sub used to so the result is good. Mind you if I put the fronts on large and leave the centre and rear alone on small it sounds better.

    Settings for the sub has been bypass set to about 89Hz and volume around 75-80db along with the settings in the Denon menu with a Sound Level Meter.

    Do I get rid of the V75 or could you tell me a better way for it to be intregrated into the system, so that it does not interfere with the overall quality of the system now and rather adds to the presentation?

    Also while im on what do you think of an upgrade of the AVCA1 to the new Denon AVCA1SE
    if ive got the model number right. What benifits would I reap?

    Thanks for any help.

    Gaz
     
  2. compusolve

    compusolve
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    Thanks Army Bloke

    I do realize some of the facts you mention, and yes the amp is THX certified, If I remove the smaller Sub which does have a smaller amp than the V75 and just plug in the V75 the centre seems to be not as involving, this is with the sub positioned slightly behind the rears and some 18ft from my listening postion.

    What I have been trying to achieve is to have a main sub with a surround sub connected through the surround out on the Amp located at the back of the room, mainly to use both subs. All speakers in small mode.

    At present I might as well sell the larger M&K V75 and settle with the VX7 and maybe later go for a B&W asw2000 or the like, but it still confuses me why a loose so much detail with the sub in place,

    Still any further ideas would be welcome.

    Garry
     
  3. Family Guy

    Family Guy
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    If you connect a sub to the surround out terminals on your amp, you will be feeding it a full range signal - including all high and mid band frequencies. A sub that is connected to the SUBWOOFER OUT terminal only, in THX mode, has all frequencies above 80hz filtered out. I believe (and I may be wrong here) that if you have the sub connected to the rear outs as you say you have, and the sub is active, then it may just be acting as another speaker. If you have all speakers set to small, this sub is only going to be recieving frequencies ABOVE 80 hz, which it wasn't designed to do.
    Connect bothe subs to the sub out terminal on your amp. If it only has one terminal, you can buy splitters cheaply from places Sevenoaks and balance your speakers using a Sound Pressure Level Meter which you can buy from Tandy's for £15.
    Failing that, let me know how much you want for your M&K!! ;)
     
  4. Arthur.S

    Arthur.S
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    I've also got 2 un-matching subs - a Rel Q50 & a Q200. I had a lot of probs getting them integrated too. If you turn off the older sub, do things sound better? It could just be a matter of positioning. For my tuppence worth, I'd suggest moving both to the front, in the corners if possible. I've got the smaller one firing into the corner, & the Q200 firing into the room. Both should be connected to the .1 channel. (use a splitter if need be)
    Set your amp as Rears & centre to small, fronts to large. Army bloke is right - normal bass is non-directional. Now the tricky bit is getting the 2 un-matched subs 'level'. Set them to about 5 decibles higher than the rest of your system. I don't think you can do this properly without an SPL. Once you've done that, hopefully things should be much better.
     
  5. Family Guy

    Family Guy
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    Your post is a little confusing but I will try to help if I can.
    For starters it dosen't help that you are using 2 different subs. I am not familiar with the models you describe but if the drivers are different sizes, amp's have different outputs etc, this will all contribute to your sound being wrong.
    If you set the centre and rear sizes to large on the amp, then all bass will come through these speakers minus the .1 channel, which will come through the sub.(providing you have told your amp you have a sub connected)! in a 5.1 soundmix. If the speakers are not large enough to output that much bass, then the soundstage will collapse.
    For bass to be routed to the subs, you need to have them BOTH connected to the subwoofer out jack on the amp, set all speakers to small and away you go. Setting all speakers to small will send all frequencies below 80hz to the subs.(I believe your amp is THX certified)
    Placement of the subs is vitaly important. Just because you want the bass from the rears to come from the subs, dosen't mean the sub has to be behind you. Bass is non directional, and, if a sub is set correctly, the human ear should not be able to hear where its coming from. i.e. Listening to the Starship Enterprise on DVD or LD, the rumble of the ship appears to come from behind you even though the sub is to your front. This is because the bass is intended for the rears, but, because you have them set to small, the bass is routed to the sub but still appears to come from the rears.

    In my paticular set up. I have 2 REL Storms and use them as stands for the front L/R pair which are Bosto 555 THX certified and I have no problems at all with bass - Just ask the neighbours!! :confused:
     
  6. Black 5

    Black 5
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    Garry,

    Because the subs interact more with the room than other speakers, placement and accurate volume setting is essential. Setting the subs relative to each other is only half the battle - if one is more powerful, it will always handle high volume signals better than the small one and therefore you are almost bound to have to compromise on the overall sub volume settings. Having the subs set way apart from each other is asking for very different room resonances to be excited by each/either and for you to receive the very confused sound you seem to describe.

    If you persist with both subs, you then should take into account the relative phase of each sub, relative to the main speakers and each other as well as room nodes, where bass reproduction is particularly pronounced. If you don't have the measuring equipment and skill to do this you're probably destined to spend a lot of time fiddling, guessing and ultimately failing to get the best from your speakers unless you hit lucky. I have a pair of CDM9NTs and they sound magnificent - why anyone would want to buy a pair of speakers of that calibre and set them to 'small' is beyond me. IMHO, you should keep them set at large, just use the better of the 2 subs and work at a decent set up from there, experimenting with speaker placement a bit at a time. I use a REL Storm with mine and there is enough bass on tap to shake my concrete floor, yet it's plenty tight enough for excellent music reproduction. Sometimes, I think it's a case of less is more :)
     
  7. compusolve

    compusolve
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    Thanks for you comments
    Army Bloke
    Arther.S
    Black 5

    I understand Army Bloke about the use of the sub on the rears would act as normal speaker, and would recieve the highs and the lows through it. I will stay clear of that idea,

    As to Black 5 comments re Large on the CDM9NT I have tried this and I can say it is awesome, and they can handle a large spread of frequencies, I had tried this before and thought that I was moving away from the THX experiance so reverted back to small, from now on I will use large.

    Also I had a slight problem when using large the centre seemed to fade in and out with different volumes, I think I cured it turning on AC3 normalistion to ON. Correct me if this is wrong.

    So I am still stuck with the two subs and the imbalance of both as in size, at present the smaller M&K VX7 is online and things are OK, the V75 MKII is sitting in a corner,

    I have tried both as individual used subs the VX7 intergrates easily the V75 still takes the centre speaker away slightly in the form of detail and clarity.

    Any more comments would be welcome and I might well be selling the V75 so watch this space.

    Anybody else out there have any experience of M&K Subs?

    Regards

    Garry
     
  8. torimusic

    torimusic
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    Try this setup when you have some time:

    Place one sub against the front wall to the left and the other to the right just behind your main left and right speakers respectively. I assume your front main speakers are not too far from the front wall. From the left main pre-out jack (assuming your receiver has them) connect an RCA cable to the left/right (bridged with a Y-RCA adapter) line level input to the sub on the left and from the receiver main right pre-out jack to the sub to the right using another Y-adapter on its RCA line inputs.
    In your receiver setup, set front main speakers to 'large' and sub to 'off' or 'none'. This will cause the processor to route bass and LFE info to the front main pre-outs and on to the subs. Please let me know if you get any positive results. You can e-mail me at trevort@datavia.co.za
     
  9. shodan

    shodan
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    Stumbled across this thread. Please have a read of what Torimusic has posted and tell me what you think. Would this in fact give the same amount od LFE info the the subs as they are getting now, but in stereo? (I have a normal setup with sub sat system so the speakers are set to small and the 2 subs go from the sub out via a splitter system). And would the Front L&R be getting the same info they get now as well?
     
  10. JBL 4645

    JBL 4645
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  11. alexs2

    alexs2
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    Yes....but with the proviso that your front speakers,being set to large,will be subject to ALL of the LF information.

    Assuming the amp and speakers are up to the task,there should be little problem,but it may well result in unneccessary levels of distortion,and also run the amp/receiver harder than required.

    Essentially,my point is that a properly integrated sub will work in most cases,far better than this sort of arrangement,but you can of course try it and see,as it's simple enough to do.


    JBL...the thread to which you're referring(the original part of this,and not shodan's post above) is over 4 years old,and the poster is no longer a member.
     
  12. shodan

    shodan
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    Well I've given it a try and it works very well! Seem to have a lot better integration adn the definition and dynamics are a lot clearer. I think the subs were muddying things up before as I can now here the surrounds and rears a lot clearer as well. Its all good stuff!!!!
     
  13. eviljohn2

    eviljohn2
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    Excellent news Shodan, next time I move my equipment around I might just give it a try myself. :)
     
  14. shodan

    shodan
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    Definately worth giving it a try! If you don't prefer it, you can always change it back! At first I thought it was a great improvement on 2 channels but no bass on 5.1 etc. It was only after a few hours of listening and experimenting with the subs setting that I realised the bass was there and it was a better, cleaner, sharper bass.
     

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