Speaker impedance question

Discussion in 'Audio Hardware' started by Rocky's Owner, Sep 11, 2019.

  1. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    I have an amp rated at 8 ohms or above. I'm thinking of purchasing tower speakers which are rated at 8 ohms. But when they say 8 ohms, do they mean 8 ohms when running the pair of speakers? Or is each tower speaker rated at 8 ohms? Because if that's the case shouldn't the manufacturer make sure to state what the total ohms will be when running the pair? Who looks at a tower speaker purchase and sees 8 ohm impedance and thinks, ok, since I'm buying two, that means the total 0hm impedance will actually be 4 ohms? Argh! Now I'm confused.

    Just worried because the amp I have is known for frying itself if you try and use 4 ohms.
     
  2. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    It’s the left seeing 8 Ohm and the right seeing 8 Ohm.
     
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  3. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    Maybe I'll just follow Andrew Jones from Elac's advice. Impedance doesn't matter.
     
  4. The FRiNgE

    The FRiNgE Forum Resident

    You're good to go, connect the speakers and enjoy the music!
     
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  5. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    Thanks, I got confused because someone in a review of the speakers said they are 4 ohms, but the Mfg Specs said 8 ohms. Each speaker sold separately. So I thought hooking up two 8 ohm speakers on an amp which is rated for 8 ohms would reduce the ohms to 4. Then I was looking at wiring speakers in parallel or in series, but didn't realize they were referring to wiring them to each side of the amp.
     
  6. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    Andrew Jones doesn’t appear to mean impedance doesn’t matter. He probably means don’t sweat all the deviations, such as from 5 to 28 in this chart of the Pioneer SP-BS22.

    [​IMG]
     
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  7. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    Heh heh, sorry, actually it was Steve Guttenberg who said "whether your amp is rated for 4 ohms or 6 ohms or 8 ohms it doesn't really matter except in extreme circumstances."



    I've seen Guttenberg recommending speaker and amp combos that didn't have the same Ohm ratings too.
     
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  8. Saint Johnny

    Saint Johnny Forum Resident

    Location:
    Asbury Park
    I have never heard anyone say impedance doesn't matter, seriously. Maybe he was making a different point.
    8 ohm speakers are pretty common these days so in that regard it might not matter.
    Because 98% of most amps made today can handle any two 8 ohm loads simultaneously.
    But if you have two 4 ohm speakers, or four 8 ohm speakers, hooked up to any amp simultaneously, and that amplifier is only really rated to handle only 8 ohm or above loads, it CAN matter really, really quickly to your amp.
     
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  9. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    It does matter, quite a bit in fact.
     
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  10. The speakers are a nominal 8 ohm impedance.
    Because a speaker is a reactive load that impedance will vary with frequency, but yours average out as being around about 8 ohms.

    If you switch to something with a nominal 4 ohm impedance your amplifier will need to deliver double the current to achieve the same output level.
    It looks like your amplifier has problems with big load swings.
    That in itself is not a problem, just avoid speakers that need big current delivery.

    What's the amp, and what are the speakers?
     
  11. timind

    timind phorum rezident

    Location:
    Westfield, IN USA
    You WAY are over thinking this.
     
  12. chili555

    chili555 Forum Resident

    Your amplifier, to which you will attach these speakers, is actually two amplifiers that share a chassis, case and power supply. Hook the speaker that will be on the left side of your room as you face the speakers to the amplifier L+ and - terminals. Hook the speaker that will be on the right side of your room as you face the speakers to the amplifier R+ and - terminals. Hook each connector red-to-red and black-to-black. Each of the two internal amplifiers is rated to accept 8 ohm speakers. Your proposed new speakers are rated at 8 ohms. You are all set!

    Enjoy your new speakers!
     
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  13. jeffmackwood

    jeffmackwood Forum Resident

    Location:
    Ottawa
    I'd never buy an amp that isn't rated to handle 4 ohm loads. (A number of mine handle 2 ohm loads.)

    Then you are safe to handle just about any commercially-available speaker out there, since it would be a rare case where a manufacturer designed a speaker that could only be driven by but a very small number of amps.

    Sure there are exceptions, but why go there?

    Jeff
     
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  14. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Just remember that your stereo amp has really two separate amplifications sections, one for the left channel and one for the right channel.

    So you have one 8-Ohm connection on the left channel and one for the separate right channel.

    You would only have a 4-Ohm nominal impedance load if you were to connect two 8-Ohm speakers is parallel to one single amplifier channel.
     
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  15. Boltman92124

    Boltman92124 Gratefully Listening

    Location:
    San Diego
    If you added a second pair of 8 ohm speakers then you would be a 4 ohm load on the amp.
     
  16. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    Thanks everybody, I stupidly didn't realize it would be 8 ohms on each separate amp section in the receiver.
     
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  17. Ontheone

    Ontheone Forum Resident

    Location:
    Indianapolis
    What speakers are you considering? It would easy to check out the minimum impedance over the frequency range if you're really worried.
     
  18. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    Should be fine. They are 8 ohm speakers and my amp is rated for 8 ohms. The speakers are JBL Arena 180. The amp is a Sherwood. Yeah, not the greatest equipment but it's what I can afford now. I was considering the Wharfedale Diamond 225, and the Klipsch RP600-M (but they seem kind of overhyped to me), but I bought the JBLs because they were dirt cheap on Fry's website as a clearance item, $49 each! Regular price $349 each. Seems like Fry's is losing money on that deal, considering I got free shipping too.

    Didn't see many "pro" reviews of them online, but the reviews on Amazon and Crutchfield are good. Maybe they were discontinued because there are so many similar tower speakers out there and not all of them are going to take off? Even though they are being discontinued they still have the white ones on the JBL website for $349 each.

    I was wondering if Fry's made a mistake with that $49 pricing. Anyway, whatever the quality, they should be an upgrade from my Bose 301 series IV I've had for 20 years.
     
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  19. jeffmackwood

    jeffmackwood Forum Resident

    Location:
    Ottawa
    I've got a Sherwood RV-4050R "Pro Logic Receiver" that I bought new in 1996, that I currently use in stereo mode to power a pair of much older Koss CM/530 speakers, which have a nominal impedance rating of 4.9 ohms. The Sherwood has absolutely no problem driving them to quite high and clean sound levels. A 1995 Julian Hirsch test report of the Sherwood says that its continuous output is 90 watts into 4 ohms, and dynamic output of 128 watts into 4 ohms. My point: don't knock yourself because you use a Sherwood. Some of them were quite good, for a very reasonable price.

    Jeff
     
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  20. Ontheone

    Ontheone Forum Resident

    Location:
    Indianapolis
    You should be totally fine. Minimum measured impedance is 4.6 ohms.
     
  21. Rocky's Owner

    Rocky's Owner Forum Resident Thread Starter

    Location:
    Los Angeles
    Well I knew that was too good to be true, Fry's tried contacting me by email and said the only ones available are "display models" and that if I don't contact them by 12:00 noon they will cancel the order. And they emailed me at 10:50. Nice. Didn't even see the email until after 12:00. Think I'd pass on the dinged-up "display models" anyway.

    Well at least I'm more clear on speaker impedance now.
     
  22. Saint Johnny

    Saint Johnny Forum Resident

    Location:
    Asbury Park
    PS: A thing I learned long ago from die hard stereophiles.
    As a quick rule of thumb.

    If the amplifier manufacturer gives impedance ratings for both 8 AND 4 ohms, (not too common, these days).
    A quick gauge to the relative quality of the amp design is that the RMS rating for a 4 ohm load output, should be at least double or as close as possible, to double that of the 8 ohm rating.
    IE: If an amplifier is rated at 50 watts RMS output into 8 ohms, in a perfect world, ideally the 4 ohm rating should approach 100 watts RMS output into 4 ohms, for a real high quality amplifier.
    If there is no rating at all listed for 4 ohms be very careful driving less than 8 ohm loads.
     
  23. jeffmackwood

    jeffmackwood Forum Resident

    Location:
    Ottawa
    Timely coincidence: someone has offered to sell me a new-in-box NAD 216THX power amp. (Yes, you read that right. It was apparently acquired many years ago when a local retailer went under, and was never used since.) I found the amp's brochure online and here's what it says about its low impedance capabilities: "The NAD 216 THX is designed with the capability to drive all types of musical signals effortlessly into even the most unreasonable of loudspeakers loads, down to below 1 ohms."

    That's impressive!

    Unless I can buy it at a quick-flip price, I don't think I'll do the deal as I'm chock-a-block full of power amps, including two sitting in my storage shelves.

    Jeff
     
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  24. Ontheone

    Ontheone Forum Resident

    Location:
    Indianapolis
    For the money that NAD line is a pretty decent value and definitely can drive just about anything. I've heard others repeatedly though complain that bass is overcooked and the treble is very weak.
     
  25. jeffmackwood

    jeffmackwood Forum Resident

    Location:
    Ottawa
    So here's what I don't get.

    NAD specs the 216THX as having the following frequency response: 20Hz-20kHz +/-0.2dB; -3dB at 2Hz/100kHz. I have no doubt that any reputable test bench would confirm that.

    So what freak of nature has hearing so good that, within the audible spectrum (for 99.999% of the earth's "normal" population) for human beings, he/she can hear a 0.2dB variation somewhere in that spectrum AND call the bass overcooked and the treble very weak - and attribute it to the amp and not some other factor (like tilting their freakish ears a few degrees off axis.)

    If I had "golden ears" like that I'd jump off a bridge with 100lb slab of concrete chained to my neck! Cripes, I wouldn't be satisfied listening to anything. Life wouldn't be worth living.

    Jeff
     
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