Close

Results 1 to 11 of 11
  1. #1
    DF VIP Member
    pete252's Avatar
    Join Date
    Feb 2001
    Location
    Macclesfield
    Posts
    1,073
    Thanks
    78
    Thanked:        11
    Karma Level
    339

    Help 4 ohm to 8 ohm speakers?

    I have some speakers that are 4 ohm but I am looking to buy a surround sound amp that only accepts 8 ohm speakers. Can I use a resistor or impedance coil or something that will allow me to use 4 ohm speakers?

    Karma will be given in your life, should you accept this task.

    x
    What if the Hokey Cokey "IS" what it's all about?

  2. #2
    DF VIP Member
    braymond's Avatar
    Join Date
    Jan 2001
    Location
    Stone Junction
    Posts
    2,498
    Thanks
    224
    Thanked:        114
    Karma Level
    410

    Default

    Not really - the impedance of a speaker varies with frequency - known as an impedance curve - 4 being the nominal value of the speaker- it's not a simple resistive load you can modify- most amps can drive 4 ohms for short periods - ie passages of music. Unless you are constantly hammering it you may be ok - what's the amp & speakers ?

    Thanks to braymond

    pete252 (14th November 2011)  


  3. #3
    DF VIP Member
    cosmicma's Avatar
    Join Date
    Dec 2000
    Location
    united kingdom
    Posts
    2,480
    Thanks
    74
    Thanked:        199
    Karma Level
    469

    Default Re: 4 ohm to 8 ohm speakers?

    there's no reason why you can't use 4 ohm speakers although the amp might recommend 8 ohms it just means it will drive the amp a bit harder but the chances are with it being a surround system the speakers won't be demanding too much current from the amp anyway
    the size of the speakers would give you an indication of how much demand the might put on an amp if there bookshelf size i wouldn't be too worried but if there large floorstanders i would be a little more concerned
    putting a 4 ohm resistor in series isn't really a good idea all it will do is soak half of the amps power up and dissipate it as heat
    i'm sure there would be a impedance matching coil of sorts out there but personally i wouldn't bother

    if you have a chance to try the amp with the speakers before you buy or can buy with an understanding that if the amp struggles with your current speakers you can take it back that is what i would do your own ears will tell you hive the amp is having a hard time driving the speakers

    a lot of higher end amps will give you it's speck at 8 ohms and 4 ohms a perfect amp would double it power output into 4 ohm with the same distortion figures but not many do
    the trouble with cheaper amps is the spec they give at 8 ohms will be right on the limit so when you put 4 ohm speakers on them they struggle but if the amp is anything half decent it shouldn't be a problem

    Thanks to cosmicma

    pete252 (14th November 2011)  


  4. #4
    DF VIP Member Over Carl's Avatar
    Join Date
    Apr 2006
    Location
    London
    Posts
    13,125
    Thanks
    3,975
    Thanked:        1,690
    Karma Level
    1251

    Default Re: 4 ohm to 8 ohm speakers?

    From my understanding, too low impedance (ohms), and whack the power up and you risk damaging your amp. (No set level for when it may cause damage). However from experience I've never popped an amp by doing so, and I've even put some stupidly low impedences by putting speakers in parallel and stuff. My experience matches cosmicma on this that the better amps seemed to handle this better while the crappy ones would sound crap.

    One idea could be to put two speakers in series to double up the impedance although it obviously won't be in stereo anymore unless you have another pair (that probably sound slightly different as your other channel).

    Thanks to Over Carl

    pete252 (14th November 2011)  


  5. #5
    DF VIP Member
    braymond's Avatar
    Join Date
    Jan 2001
    Location
    Stone Junction
    Posts
    2,498
    Thanks
    224
    Thanked:        114
    Karma Level
    410

    Default Re: 4 ohm to 8 ohm speakers?

    you will probably be fine. as others say above only driving a 4 ohm load at constant high level would cause issues with a badly designed amp, if its a surround sound amp of reasonable quality it will be fitted with a current over limit detector anyway which willl switch the output relay off. you may find it just trips out at high level. if it does this regularly then its either a bit of crappy amp or the speakers are a particularly nasty load - both unlikely.
    virtually no amps have the same distortion performance at 4r as 8r - and very few can genuinely achieve double the output power into a 4r load, it requires a very beefy supply. for example most surround sound amps quote 7 x 100w. This is a rather meaningless stat anyway as it doesnt quote the distortion - but NONE of them could continually drive 100w into 4r at say 0.1% thd. your surround amp would be the size of a dishwasher :-)
    ive just built an amp that can do this, but its only stereo and cost £700 in parts alone

    2 Thanks given to braymond

    Over Carl (10th November 2011),  pete252 (14th November 2011)  


  6. #6
    DF VIP Member Over Carl's Avatar
    Join Date
    Apr 2006
    Location
    London
    Posts
    13,125
    Thanks
    3,975
    Thanked:        1,690
    Karma Level
    1251

    Default Re: 4 ohm to 8 ohm speakers?

    Any chance of a new thread for your amp - would love to see it

  7. #7
    DF VIP Member
    braymond's Avatar
    Join Date
    Jan 2001
    Location
    Stone Junction
    Posts
    2,498
    Thanks
    224
    Thanked:        114
    Karma Level
    410

    Default Re: 4 ohm to 8 ohm speakers?

    its with a client being tested - but i will post some pics when it comes back to me to be finished (no on off switch yet!)

    Thanks to braymond

    Over Carl (10th November 2011)  


  8. #8
    DF VIP Member
    cosmicma's Avatar
    Join Date
    Dec 2000
    Location
    united kingdom
    Posts
    2,480
    Thanks
    74
    Thanked:        199
    Karma Level
    469

    Default Re: 4 ohm to 8 ohm speakers?

    krell amps double up

    funnily enough i was going to buy the krell ksa 50 back in the 80's to go with the AR 9LS speakers but i found the perreaux pmf 1150b to be a better power amp
    now i have the kef reference model 4's the amps that make em sing are you guessed it KRELL
    not got the perreaux now the meridians that replaced it sound good but i always wonder about the krell
    maybe if i win the lottery

    bit off topic there......

  9. #9
    DF VIP Member
    braymond's Avatar
    Join Date
    Jan 2001
    Location
    Stone Junction
    Posts
    2,498
    Thanks
    224
    Thanked:        114
    Karma Level
    410

    Default

    Quote Originally Posted by cosmicma View Post
    krell amps double up

    funnily enough i was going to buy the krell ksa 50 back in the 80's to go with the AR 9LS speakers but i found the perreaux pmf 1150b to be a better power amp
    now i have the kef reference model 4's the amps that make em sing are you guessed it KRELL
    not got the perreaux now the meridians that replaced it sound good but i always wonder about the krell
    maybe if i win the lottery

    bit off topic there......
    Krells double up in power but Im willing to bet if you sweep the thd across 20k it's worse at 4 . There are honestly virtually no amps with the same thd at 4r.

    But yes we are going off topic lol

  10. #10
    DF VIP Member
    pete252's Avatar
    Join Date
    Feb 2001
    Location
    Macclesfield
    Posts
    1,073
    Thanks
    78
    Thanked:        11
    Karma Level
    339

    Default Re: 4 ohm to 8 ohm speakers?

    Thanks to all concerned, good advice as usual. I did try the 4ohm speakers but they sounded utter shite. Also didn't realise that the amp needed an active Sub - that has got to be a con!! Ended up getting a new set of speakers with active sub, quite nice now.
    What if the Hokey Cokey "IS" what it's all about?

  11. #11
    DF VIP Member Over Carl's Avatar
    Join Date
    Apr 2006
    Location
    London
    Posts
    13,125
    Thanks
    3,975
    Thanked:        1,690
    Karma Level
    1251

    Default Re: 4 ohm to 8 ohm speakers?

    Active subs are pretty standard tbh.

Similar Threads

  1. Replies: 0
    Last Post: 7th October 2002, 02:23 PM
  2. Philips 15" TFT monitors with Built in Speakers
    By Mr Mod-it in forum Buy, Sell and Trade
    Replies: 4
    Last Post: 25th September 2002, 02:05 PM
  3. 5.1 DTS speakers £99
    By Gavin M in forum Cheapskates Corner
    Replies: 1
    Last Post: 18th September 2002, 10:52 PM
  4. louder speakers!
    By Billy_Wiz in forum PC Problems
    Replies: 8
    Last Post: 16th September 2002, 02:37 PM
  5. Can u rewire speakers? Help plz!!
    By t-rex in forum The Dog and Duck
    Replies: 7
    Last Post: 31st August 2002, 03:43 PM

Social Networking Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •