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Impedance question

Discussion in 'Amps and Cabs [BG]' started by Geezer Brown, Dec 12, 2013.

  1. Hi,

    I may be getting an SWR Bass 350 soon, and supposedly the amp can handle 2 Ohm loads. I was wondering, can you run an amp at 2 ohms into a single ampeg 8x10?

  2. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    2Ω is the minimum load the amp will safely operate at, as long as the cab is rated higher, it's fine.
    edit: Higher, or equal to, that is.
    Amps don't have ohms, speakers do, you just need to know where bad things will happen, so they tell you in the amp specs.
  3. Don't believe so.........

    As far as I remember, they run 4 ohms mono, or two 4X10 sections @ 8 ohms each.

    Question though - why would you want to run it at 2 ohms ?

    The "increase" in power output is almost undetectable in volume increase.
  4. Awesome. I wanted to run the amp at the full 450w, instead of the 350 you get at 4 ohms, so this is great!
  5. Fat Steve

    Fat Steve The poodle bites, the poodle chews it.

    To run at 2 ohm, you'd have to run two 8X10 fridges at 4 ohms a piece.
  6. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Yes you can run the SWR 350 with the 810. The Ampeg 810 is 4 ohms mono or 2X 8 ohms split in 2 410 chambers. With the 4 Ω cab, the SWR will put out 350 Watts. SWR recommends that this amp be run with a 4 Ω load for optimal performance. But you can run it a 2 ohms with 2 810 cabs (or any other combination the will give you 2 ohms) as has been mentioned to give you the 450 Watts.
  7. I'm talking about a single 8x10 cab
  8. Fat Steve

    Fat Steve The poodle bites, the poodle chews it.

    A single 8 x 10 will EITHER run 4 ohms to all 8 speakers, or 8 ohms to either the top or bottom sets of 4 speakers.
  9. Jeff Scott

    Jeff Scott Rickenbacker guru.......... Supporting Member

    As mentioned, the difference in what you will hear is pretty negligible regarding output power, however, you will be stressing the amp a lot more than necessary. Yes, the amp is "rated" to work into 2Ω but that doesn't mean it will be happy down there. When I see a very small increase in power output while halving the impedance load I start thinking specsmanship (this does not apply to most tube amps or those micros with a "2Ω switch" like the Carvin). Using speakers with greater sensitivity will go a lot further that that extra 100 watts you will get from the Bass 350 at 2Ω.

    Although, you will be able to cook your fried chicken embryos and dead fried pig much quicker!
  10. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    Are you going to build your Class-D amp so it's safe at 2ohms?
  11. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    I think I misunderstood the initial question, but you get the point. Generally speaking, connections go in parallel, meaning that two of the same impedance cabs will show your amp HALF of the Ω that each cab is rated for (2x8Ω=4Ω and 2x4Ω=2Ω). More speakers (or higher sensitivity speakers) are the better way to get louder. 350 watts through an 8x10 is pretty loud! I would imagine you wouldn't run out of headroom at 4Ω for 90% of situations, and even running at 8Ω through the top half of the cab would cover lots of your needs. YMMV.
  12. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com

  13. BawanaRik


    Mar 6, 2012
    New Jersey
    It's been my experience that running a more efficient cab can have a great impact that the little bit of extra wattage you get by going to 2 ohms

    Enjoy the head through the 8 10. I'll bet it will sound great.
  14. Fat Steve

    Fat Steve The poodle bites, the poodle chews it.

    No kidding! Last night I played my PF 350 through a 2011 Heritage Series 8 X10, and I was blown away by how loud the cab got. I usually play through an Eden 4X10 that will kind of fart out if I push it too hard.

    Definitely gonna be looking for 2- 8 ohm Ampeg 4x10 once I get some scratch!
  15. Troph


    Apr 14, 2011
    Kirkland, WA
    No, because there is no single Ampeg 8x10 that has an impedance of 2 ohms. But if you could magically find one, then the answer would be yes.

    2 ohm cabinets are extremely rare. Here's an example of the Acoustic 408, one of the few that were commercially available:
  16. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    Yup! They can get well loud, here is mine that grew some JBL stuff for some more mid and top out of it. All Hail The Mighty Acoustic 408:hyper:
    I run it with a JBL 260 DSC and a Crown Ma3600VZ for the bass and 2206 mid bass and a Carver PM 600 for the 2445 2" horn drivers.
    It's a bit mighty for bass duties in the drum room so it mainly does triggered kick monitoring for metal bands these days never blow it up
    Yet, still on the original drivers.:D:bassist:
  17. BawanaRik


    Mar 6, 2012
    New Jersey
    Which Eden? I have the 410xlt and it doesn't engage in such behavior.

    And I think the 8 10 cab is gonna sound better that the 410 Ampeg.

    I use a single 10" when I play with people because it's light. But when it comes to all out sound it's my most humble opinion that size matters.
  18. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    The Heritage 810e will, but the regular 810e and 410he use the same speakers and are about the same volume per speaker, so there's not much of a difference that I can hear.
  19. Troph


    Apr 14, 2011
    Kirkland, WA
    Sweet. I've never seen one of those in person before, but they look massive!
  20. Camera angle helps ;).