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FYI: Pioneer AX5i & 4 ohms

Discussion in 'AV Receivers & Amplifiers' started by witters, Jan 2, 2004.

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  1. witters

    witters
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    I'm looking to buy a new receiver and his was on my list. My speakers are Kef THX ref's which have an impedance of 4 ohms. I have just rung Pioneer and spoken to their technical dept. I was told that in no way should the AX5i be used with speakers with a greater load than 6 ohms. He made it very clear that any damage done to the receiver would NOT be covered under their warranty.

    Bugger!

    Thought this may be of interest as I have seen the question on here before.
     
  2. Dimmy

    Dimmy
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    Interesting...

    Fortuately I have the most efficient speakers I've ever come across, in Mission's 77 series...

    I assume you're looking to use an A11SR with your speakers instead?

    Still risky - I think there's a risk of it shutting off at reference levels with all channels driven. Although I'm sure other will disagree with me.
     
  3. witters

    witters
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    Well I'm now wondering if I did the right thing in buying the Kef's off this forum. Looks like I'm going to have to part with more wanga than I'd like to get suitable amplification.
     
  4. Dimmy

    Dimmy
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    What amp are you using now?

    If your amp has pre-outs then just buy an RMB1075, which will be able to drive them pretty well.
     
  5. witters

    witters
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    I bought the speakers in a package with a Denon A1D which I have sold on. Consequently I don't have an amp at the moment. I would ideally like to stay with a THX amp/receiver but options appear limited. The only othe receiver for around a grand that will drive 4 ohms well enough is the new Sony 5000. Not only is it ugly it's aslo untried.
     
  6. Dimmy

    Dimmy
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    Were I you I'd follow my own suggestion (how contrived does that sound :laugh:?).

    Buy a budget A/V Receiver with pre-outs and use it as a processor for an RMB-1075.

    You'll lose a lot of processor power compared to the A11SR but you'll have no trouble driving your speakers, and can upgrade the processing accordingly.
     
  7. witters

    witters
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    Hehehe!

    You talk as if money is no object, but I'm afraid it is:(

    Might decide to sell on the Kef's and get some speakers that are easier to drive.
     
  8. Dimmy

    Dimmy
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    Second Hand you should get both for around £900. New, probably a smidgen over a grand.

    I think THX Ultra specs that a poweramp should be able to drive speakers of load as low as 3.2 ohms, IIRC. So on that premise, the A11SR should be able to cope.

    Of course, the problem arises in finding one in the Second Hand arena - and then getting the person selling it to let you have it for £850, which seems like no mean feat.

    I'll have a look at other amps available in the price sector you're looking at and post back should I find anything that looks likely to be comfortable with 4 Ohm Loads.
     
  9. witters

    witters
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    That's very good of you matey, and much appreciated. As a point of interest the Ax5i is THX, so why will that not drive 4 ohms? Is it because it's THX select, rather than Ultra?
     
  10. Dimmy

    Dimmy
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    Yes, THX Select's criteria and tests are less vigorous than the THX Ultra tests.

    Two likely candidates include Harmon Kardon receivers : The AVR4550 and 5550, which retail at £800 and £900 respectively, and appear as though they're going to be able to cope with a 4 Ohm load.

    The power output of both increases by about 1/3 with 4 Ohm loads with five channels driven, which is much better than most in those price sectors.

    The 4550 delivers 100wpc into 4 Ohms with all channels driven, the 5550 around 110wpc. Which should suffice. Of course, the downside is that the processing in Harmon kardon receivers isn't quite as advanced as you'll find in similarly priced Denons, Pioneers and Yamahas. And they're not THX Certified.

    Other forum members will recommend NAD AV receivers too, which apparently cope very well with 4 Ohm Loads. However I'm not familiar with the model numbers or specs at all, so will leave that to other forum members :D.
     
  11. Digger

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    Witters,
    see my post below. i too spoke to Pioneer today who gave me the same response but i have gone ahead and ordered AX5i anyway on the basis that my room is reasonably small, and that i also have a spare NAD319 amp that could be used for front speaker duties should the ax5 start going into hairdryer mode:)

    http://www.avforums.com/forums/showthread.php?s=&threadid=109934
     
  12. witters

    witters
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    hmmm - that's interesting. Mine too is a small room and I will only be using in 5.1 which means I can bi-amp the front speakers. I only live 3 miles from Empire's collection centre as well.:D
     
  13. antz

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    Hi Witters
    My AX5i is partnered with the following:

    KEF: 103/4 - 4 ohm
    KEF: 200c - 4 ohm
    KEF: TDM 34ds - 4 ohm

    The front stereo pair are bi-amped.

    I bought my AX5i from Creative in Shrewsbury and discussed the issue of the AX5i driving the KEF's before finallising the purchase; I was assured that this amp would have no problem!

    Experience has confirmed this. LOTR Two Towers at reference levels (-10db to -5db) for 3.5 hours sounded brilliant and absolutely no over-heating or any sign of the amp not coping.

    I have the cross-over set at 50Hz and the KEF 30b produces controlled bass in my 12 * 15 room. I really cannot recommend this set up enough.

    My only question is should I invest in power amps to bi-amp the centre?

    My advice is to go ahead and make the purchase....I'm no expert and can only speak from personal experience. Let us know what you do and how it sounds.

    Antz
     
  14. Dimmy

    Dimmy
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    I think Pioneer may have just been 'Playing It safe' in what they told you Witters.

    Judging from Lab testing of the AX5i it looks as though it'd cope with 4 Ohm Loads - not comfortably, but cope. The Biamping of the front L/R channels would only ease the strain on the amp.
     
  15. witters

    witters
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    Thanks Antz,

    It's nice to hear from someone who has practical experience at last:D

    I guess my room is about the same size as yours so I might give it a go.
     
  16. steve36

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    Witters,
    Any luck with the A11SR purchase?

    One comment, a high end hi-fi store said to me recently whilst trying to sell me an ARCAM AV8/P7 combo was that the Pioneer AX10i they had on demo kept overheating all the time.

    No-one has ever said this regarding a DENON A11 or A1 amp.

    They were driving front Nautilus speakers, with M&K rears.

    Steve
     
  17. witters

    witters
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    I've located a Denon for £1050. It's ex-dem so I get full warranty. havn't decided wether to go for it yet:rolleyes:
     
  18. Buckland

    Buckland
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    This is all interesting to me.

    I also have a new ax5i with demanding 4 ohm dynaudios all round (72 l/r, 122c, 42 rear, rel sub). It seems to work pretty well without breaking up, even at higher volumes (if the missus is out!)

    However, i do pre-out into my hifi integrated amp for the l/r to get better quality audio (i'm afraid the ax5i & 868 dvd are not good enough for cd). This might take off some of the strain.

    I've got the amp set at the lower ohm measure.

    I've heard about bi-amping. Can somebody explain what it means? Should i be doing it? Which speaker/speakers should i be doing it to?

    Also, as a matter of interest, what sort of settings/crossovers are you all using for these demanding speaker systems?

    Thanks
     
  19. Dimmy

    Dimmy
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    Buckland - i haven't tried it with the AX5i. But as I understand it, the two channels used to amplify the centre-rear channels are fully assignable. And - in the OSD I'd assume - you can instruct the amp to 'assign' them to the front channels (aswell as the amps you're already using for the front channels), which thus provides the potential for biamping.

    Of course, this requires compatible speakers than have twin sets of speaker terminals.
     
  20. witters

    witters
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    I don't think you need bi-wireable speakers Dimmy. The way it's done allows normal speaker cable to be used, as far as I understand it. It tells you how in the manual, surely?
     
  21. Andywilliams

    Andywilliams
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    Hi witters
    Your speakers do need to be bi-wireable ie high and low connections for twin runs of speaker cable.
    Cheers Gonzo.:)
     
  22. Buckland

    Buckland
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    but dyns don't have 2 sets of speaker inputs......
     
  23. Chrissywis

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    If you've only got one pair of terminals on your speakers you can't bi-wire or bi-amp.
     
  24. Buckland

    Buckland
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    well that's that then!

    what about crossovers etc?
     
  25. witters

    witters
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    Bummer!
     
  26. russraff

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    Dynaudio don't believe in bi-amping or bi-wiring their speakers. They think it doesn't make any difference, hence the single pair of speaker terminals.

    80Hz x-over is the standard, certainly it is for THX. Personaly I use 60Hz as this provided a much tighter bass from my previous sub. 80Hz seemd to boom too much and could be one-notey (if you see what I mean?), though this might have been my setup. Having said that, the sub I have now has a max x-over of 67Hz, so perhaps there is something in having the sub set lower than THX spec 80Hz?

    As to the 4ohm thing, even Yamaha's new AZ9 monster amp from hell is only rated to drive 6ohm. The Pioneer AX5i is a powerful amp and will be able to drive KEF THX speakers fine.

    Russell
     
  27. antz

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    Hi

    I've just lowered the cross-over setting to 50Hz and the whole system seemed to come to life; nice controlled bass, the scenes in Aliens with space craft panning across the screen provides excellent demo material.

    I'm not sure if this is logical or not, but the AX5i seems to send more bass to my front 3 - KEF 103/4's & 200c (perhaps I am imagining this as they are all set to Large anycase).

    I know the issue of bi-wiring and bi-amping will always bring out conflicting opinions....but the 103/4's really do seem to benefit from being bi-amped....especially on ht ehi-frequency side which seems much crisper, clearer and controlled.

    Antz
     
  28. Buckland

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    also, i find that i "lose" the rear speakers at lower volumes (say -25). I need to listen at this level in evening cos of kids asleep.

    Just watched a bit of LOTR:TTT with much louder volume at -13 and the surround really comes alive.

    Is this because they are the demanding 4 ohm dynaudios 42s? Should i change the balance for lower volumes?
     

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