More tech questions? Joris?

Discussion in 'Amps and Cabs [BG]' started by rockindoc, Mar 31, 2002.

  1. rockindoc

    rockindoc Daily Lama

    Jan 26, 2002
    Bonham, Tx
    I tried a post search, 4 ohm vs. 8 ohm, and there were 1071 results, so I'm bringing it up again. Seems like most high-end cab makers lean toward the 8 ohm side. For example, EAs are all 8 ohm; Wayne Jones, 8 ohm; Hevos, almost all 8 ohm; Bag End, about 3 to 1 are 8 ohm, Epi's & Berg's, though, are about split. Accugroove's bigger dollar cabs, 8 ohm. In other words, I see a trend here. I have an Eden WT800, 400W per side into 4 ohms, and I'm shopping for a pair of cabs. I assumed, wrongly perhaps, that I should be looking at 4 ohm cabs. My choices seemed limited. Then Joris opened my eyes (previous tech question post) by saying if you load a 4 ohm capable amp with only 8 ohms, it will sound BETTER! I'd appreciate some more comments about this before I blow big bucks on 4 ohm cabs, and end up wishing I'd got 8 ohmers. I don't know how many watts my WT800 will push into 8 ohms (no manual), but I guess it's enough for most purposes. It WILL bridge into 8 ohm only. Sorry for the lengthy post. rd
  2. bassist286


    Nov 22, 2001
    rhode island
    whats the question?
  3. rockindoc

    rockindoc Daily Lama

    Jan 26, 2002
    Bonham, Tx
    Well, Joris thinks 8 ohm cabs sound better. What's your preference?
  4. Sorry for the delay, haven't been around much lately.

    Connecting a 4 ohms capable amp to an 8 ohms cab will sound tighter than a 4 ohms cab on the same amp. However, this is theory, I haven't had much experience in telling the difference. Besides, the WT800 isn't quite your average cheap-ish/lowpower-ish amp, so I hardly doubt you'll be able to tell the difference.

    But consider this: generally, a 4 ohms cabinet will get 30-60% more power out of a solid state amp than an 8 ohm.

    What's also important to consider is: will you ever buy more cabinets and will the amp be able to drive their combined load?

    I hope this answers your question.

  5. Matthias


    May 30, 2000
    Vienna, Austria
    I admit that I don't understand too much of the details.

    But my (probably wrong) thought is: if I use an 8Ohm cab I will have to push the amp harder to achieve the same volume as with a 4 Ohm cab. This should result in less headroom = worse sound with the 8Ohm cab.
    However, if I compare the two cabs with the amp running at power levels so that total harmonic distortion is the same in both cases, the 8Ohm cab may sound tighter, but it will be quieter.
    Or am I on a wrong path here?

    I always thought the only reason for different Ohm ratings is making it possible to mix and match cabs and heads.
    E.g. if I have a mono amp capable of a 4Ohm load, I will buy a 4Ohm cab if I want to use one single cab (e.g. 810) or two 8Ohm cabs if I want to use two cabs, e.g. 115 & 410.

  6. Hey Matthias & all,

    The tightness issue comes from the fact that all amps have an output impedance. This is the amount of control an amp has over its load. Look at it as a resistor in series with the amp output. The cab, being a complex impedance, affects the sound, especially in the low range, where its impedance changes dramatically.

    So when load impedance goes down, the relative output impedance of the amp goes up (in fact it's almost constant, at least, way more constant than the cab's impedance response). This results in less control over the load and a tightness slightly decreases.

    This is the same reason why you should use as thick a speaker cable as possible: to rule out any series resistance in the amp-to-speaker path