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Modded Kef 65ds to bipoles.

Discussion in 'Home Cinema Speakers' started by Tim Cooper, Feb 8, 2003.

  1. Tim Cooper

    Tim Cooper
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    Hi all,
    I've never really been a fan of di-pole speakers, i'm more of in-yer-face chap:D so i set about my speakers & reversed the phase on the out of phase cones ( the ones facing the rear wall as you look at them).
    I must say that they sound rather good, being some 1.3 meters away from the the rear wall & me sitting in the "null" position i hear more now....not so vague.
    Anyone else done the mod? Tell us what you think.
    Tim
     
  2. ilkand

    ilkand
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    How do you do this then? Is it easy? I'm a bit bored with my system at the moment, so might be up for some fun:D
     
  3. Tim Cooper

    Tim Cooper
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    Ilkand,
    Remove the speakers from the wall, loosen the mounting bracket & pull your speaker wires under the mounting bracket, pull off the shiny plate from the bottom of the speaker, remove the Kef badge (important) & pull the speaker stocking over the top of the speaker (you can't remove it fully due to the mounting bracket) now this bit's crucial & you must get the orientation right, the cone that fires BACK is the one you want to remove (the right hand cone for the right speaker, the left hand cone for the left hand speaker assuming you have the speakers set correctly on your wall i.e right to right left to left) remove the two phillips screws & gently remove the cone, remove the wadding from behind the cone, the wire on my speakers is blue, if you look carefully where the wire terminates on the cone you will see plus & minus near the where you will have to resolder.
    The wire with the black stripe is the negative, desolder the wires & reverse them (the black stripe wire to the positive) be v.careful not to overheat the solder blocks or you will ruin the cone.
    Et-voila a pair of Kef bi-poles for no money & half hours work:D
    Cheers.
    Tim.
     
  4. ilkand

    ilkand
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    Right, where's my soldering iron:D

    Thanks for the reply,

    Andy
     
  5. Tim Cooper

    Tim Cooper
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    Hi Andy,
    How did it go, did you mod yours at all?
    Been listening to mine the weekend & i'm well pleased with the mod, i can here a lot more in the rears now...nice & clear.
    Wonder if anyones managed to put a switch in to flick between bi/di pole...
    Anyone had/got the bottle to do a pair of kef TDM34's:D
    Cheers..
    Tim.
     
  6. Matt F

    Matt F
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    So you're saying that with a little bit of work with a soldering iron I can make my lovely (£700) TDM34DS's sound like my old (£150) Eltax HT-2 bipoles? Mmmm, it's very tempting but, tell you what, I think I'll give it a miss ;)

    I know it's a personal thing but having had both I consider bipoles to be a cheaper alternative to dipoles i.e. they diffuse the sound but they don't do it as well. Each to their own though.

    I seem to remember that some manufacturers do offer speakers that can be switched between bi and di pole (Polk possibly?).

    Perhaps the ultimate solution is M&K Tripoles - the best of both worlds?

    Matt.
     
  7. ilkand

    ilkand
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    Tim,
    Started it, never got round to finishing it. You know the score, you think you've got time on your hands and then somebody else thinks you shouldn't have. Hoping to finish it tonight.
    Just one thing, I have my speakers a lot closer to the back wall than yours. Is 1.3 meters the optimum distance for them? Would making them bipoles allow you to move them further towards the wall?

    Cheers
    Andy
     
  8. Tim Cooper

    Tim Cooper
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    Hi Matt,
    The sound from my now bi-poles is very good, not quite direct sounding but not quite a di-pole either, somewhere in the middle. The beach sequence on saving private ryan has more "guts" (sic) to it now, the sound is enveloping like a di-pole but with a bit more directionality so i've got the best of both worlds.
    Can't say as i'd blame you for not modding a set of £700 speakers, i'd love to hear them after though or maybe put a switch in then you could have the best of both worlds:smoke:
    If they were mine i'd def give it a go, & change all that cheapo internal speaker cable as well (well it looks cheap inside my 65's).
    I seem to remember that di-pole speakers were originally developed for vanilla DPL to diffuse the sound coming out of the rear channels. I think bi-poles are more suited to DD, DTS et-al IMHO.
    The best sounding rear wall hung speakers i have heard,are the M&K SS-150 tri-poles closely followed by a switchable Polk speaker (can't remember the model number...something 1000 i seem to recall)
    Come to think of it.......i may modify the 65's again to a set of tri-poles:D
    I think at the end of the day you pays your money.....

    Andy,
    I measured the distance & it's a meter,not 1.3 as stated.
    Idon't think there is an optimal position, as long as your sitting in the "null" position the di/bi-poles were devloped to fire longitudally down & up your room check out Kef's site.
    I don't think making them bi-poles makes any difference as to placement,although if it was me i'd make sure the speaker cone facing the back wall had at least a couple of feet to let the speaker "breathe"
    Cheers.
    Tim.
     
  9. ilkand

    ilkand
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    Tim,
    Have had a go and am most impressed. A good improvement for me, in my smallish room. Still don't understand it though. Why only change the phase on one driver? Is this really a bipole now? I never really got the dipoles to work in my room, but when I auditioned them they did sound great. Perhaps it was the electronics.
    What to change next?

    Cheers
    Andy
     
  10. bob007

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    Yipee, someones mentioned Polk. :clap:

    You are spot on Matt, Polk have included a switch on certain models so you can manually switch between di/bi-pole, in fact I have the Polk F/X500i's which have the said "switch". :)

    Damn fine speakers, Polk. :smashin:
     
  11. Tim Cooper

    Tim Cooper
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    Hi Andy,
    Nice 1....knew you would like that.
    Di-poles are made with the rearward facing driver out of phase this is done deliberately to give you a diffuse un-directional sound,
    you don't know that they are connected, until you disconnect them, they are more for ambience than effect.
    Bi-poles are the compromise not as directional as a conventional speaker then not as subtle as a di-pole.
    Size of the room i reckon plays a role in why the speakers sound better at dealers plus I usually find that they crank up the rears too much.
    Do you set up your speakers with a sound meter? because if you don't may i suggest you get one, you can't set the levels by ear alone.
    How far are your rearward drivers from the rear wall?
    I'm seriously considering making some tri-poles from the 65's.... watch this space.
    Tim.
     
  12. Tim Cooper

    Tim Cooper
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    Hi Bob,
    Polk mentioned twice methinks:clap:
    Tim.
     
  13. bob007

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    Yes indeedy they were mention twice :) but as Matt mentioned them 1st I posted his quote ;) but as you have mentioned them in the same sentence as M&K's and it is your thread thought it was only far to post this, plus it gives Polk another mention. :D

    The Polk F/X300i's/500i's/1000i's can all be maually switched for di/bi-pole operation, the difference being the F/X300i's switch is located on the back of the speaker were as the F/X500i's/1000i's are on the side.

    Also the new range out now are all switchable as well, F/X50i's/F/X30i's LSiF/X

    Did i mention that Polk are a damn fine speaker. :)
     
  14. Tim Cooper

    Tim Cooper
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    They are indeed....i would love those fx1000i's but at a grand too rich for my blood mind you that was a couple of 3 years ago...hmmm i wonder how they would sound with my kef front sound stage.....if only kef would bring out some decent bi-poles or even tri-poles....did i mention that kef make a damn fine speaker:devil:
    Cheers Bob.
    Tim
     
  15. ilkand

    ilkand
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    Hi Tim,
    I must admit I don't have a sound meter. I set them by ear, but found that I often changed the level as sometimes the sound was in yer face loud and at other times almost non-existant. Quite annoying really. I also have some 70's which I tok to using instead.
    The drivers are about 80cm from the rear wall, which I reckon should be just about enough to stop reflections.
    How do you make tripoles then? Sounds like advanced engineering that. Might be out of my league.

    Cheers
    Andy
     
  16. Babylon

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    Tim,you say that di-poles are made with the rearward facing driver out of phase as a matter of design,so would I be right in saying that you would have a left and a right speaker,because I'v got a set of Kef Q2ds's and they are not marked left and right.
     
  17. Tim Cooper

    Tim Cooper
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    Babylon,
    The Kef 65DS' were made with left & right clearly stamped on the speaker, so i can't comment as to why the latest from kef has not got the stamps.
    Does the instruction manual state the orientation of the speaker? i.e a front & a back.
    Cheers.
    Tim.
     
  18. Jase

    Jase
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    Might be on the serial number i.e 4236L for Left, 4236R for Right. That´s how Kef label their THX Dipoles.
     
  19. Babylon

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    To me it dose feel as if the Q2ds's were a bit of an after thought for Kef,the manual is the same as you get with the other Q series speakers with just an Addendum sheet for the Q2's.It tells you were and how high to put them,and how to wire them up,but that's it,no specific left of right marking anywere,not even the serial numbers,will give Kef a ring.
     
  20. gmt steve

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    I might try this with my TDM34s, I'm not sure how it complicates things by their being a tweeter and a mid range on each face, do I reverse both or just the mid-range?
    As far as Kef owners manuals go, even the Refrence range has those poxy booklets. Great speakers, awful manuals.
     
  21. Tim Cooper

    Tim Cooper
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    Steve,
    I'm not quite sure but i think the midunits on the TDM34's are ALL in phase it's just the rearward tweeter thats out of phase. PERLEEZE be careful with the soldering iron:smashin:
    Cheers.
    Tim.
     
  22. Babylon

    Babylon
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    Ok,I phoned Kef and they said it dosen't matter,well to start of with the bloke was surprised that they weren't marked,he said some of the other models were maked L and R or it was in the Serial No,so he took them to check I had a pair,which they were so he said he would find out as he needed to no himself.

    Well basically this has been done so that the speakers arn't restricted to just the Left or Right and I can put them on the back wall if I wish or something like that,but what he did say that I found odd, was that I could just swap round the speaker cable at the crossover and change what speaker is out of phase that way,so a bit of experimentation for me one thinks.
     
  23. gmt steve

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    Tim I had a look indide the TDM34s last night and ended up a little confused.
    All the wires are on the same terminals vis-a-vis + and - on both the front and rearward firing drivers. What I mean by that, is that on both drivers the wiring is identical and not reversed on one or the other. So I left things as is.
     
  24. GaryG

    GaryG
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    A simple test to determine the phase is to pull the sock down so that you can see the drivers and connect a 1.5v (9v at a push) battery across the input terminals. If they are in phase all drivers will move in the same direction (outwards).
     
  25. Tim Cooper

    Tim Cooper
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    Steve,
    It was the same on my 65DS' the wiring looks correct but in fact the rearward firing unit must be out of phase at the crossover, so the wires must be reversed, in my case a blue wire with a black stripe to the positive solder block.
    The 65DS's are different from the TDM34's in that they do not have the tweeter in the middle of the mid/bass unit (they are a one peice mid/tweeter unit...el-cheapo looking in fact :( )
    I think i read some where that the TDM34's rearward firing tweeter is out of phase, the mids being in phase.
    Do you have four wires going to the tweeter/mid unit?
    Cheers.
    Tim.
     
  26. gmt steve

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    I used to have the 65DS, so I know what they're like. As far as the wiring goes you're spot on Tim. Four wires going to the terminals on the driver's basket:
    HF+; HF-; LF+ and LF-
    Then two much finer wires leave the connection block and go to the tweeter mounted in the mid-driver's center.
    Before I went ahead with the mod I'd like to confirm whether or not high and mid are both out of phase or just the high. I'm inclined to think it's both, since in the 65DS the single driver covers mids and highs. I'm think it's only the bass that's in phase.

    Gary, I'm aware of the 9v battery trick for finding which wire goes to which speaker, but the drivers move too quickly and not enough to assertain which direction they are moving in.
     
  27. gmt steve

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    Tim, can you remember exactly where you read about the TDM34s and which drivers are out of phase?
     
  28. Tim Cooper

    Tim Cooper
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    Hi Steve,

    All i can recall it was on some forum about a year ago wasn't a member so i never bookmarked it sorry m8.
    You won't do any harm to the speakers if you reverse the wires, the danger is if you linger with the soldering iron you could de-solder the fine driver wires & they are a bugger to re-solder.
    I done a google search but nothing i'm afraid...why don't you give Kef a call to find out they are generally helpful...IIRC there used to be a bloke from Kef who used to post to these forums but i haven't seen any post's from him for ages.
    I'll have a troll around the weekend.
    To rub salt....i'm well impressed with 65's as bi-poles the jet crash in Behind Enemy Lines in DTS is Fabaroo luverly.....i'd love to hear the TDM's after they have been modded....in fact i'm going to make it my next purchase & i think i'll put a switch in hmmmm:smashin:

    Cheers.
    Tim
     
  29. gmt steve

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    I'm not worried about damage Tim, I just don't want to waste time gettng it wrong. I thought of phoning Kef, but look at the advice they gave Babylon. If he follows that advice he'll just end up with one speaker out of phase relative to the other, which will certainly cancel out a lot of the bass. So I don't want to depend on their advice. I'll probably give it a go this weekend. I let you know how I get on.
     
  30. ilkand

    ilkand
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    Did anything ever come of this? I am interested in making my rear 34ds more directional.

    Thanks
    Andy
     

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