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what's the concensus on 300-400 watt heads?

Discussion in 'Amps and Cabs [BG]' started by bino, Feb 26, 2004.

  1. bino


    Jun 27, 2002
    Orange County
    It seems like amps in the sub 500 watt range at 4ohms are real common and popular. I am only now beginning to look at a small rig and don't have a lot of experience with high volumes. Assuming I won't be playing extremely loud music, what kind of venues can a 300, 350, 400 watt head fill? I was recently at a show in a 1000 sqft room with 30 people and the bass player was using 2 ampeg 8x10's and 2 svt's. I enjoyed have the wind knocked out of me, but it didn't seem to practical or necessary. Also, can you realistically drive 2 8ohm cabs (say 2 112's or a 210 and 115) with that much power? Thanks for the advice.
  2. i drive 2 1x15s with my swr sm400 and its mad loud when i crank it up and boost mids, it can punch you right in the gut if your not carefull. 2 810s for 30 people is a little rediculous, my sm400 out of one 1x15 is enough to compete with drummer and guitarist
  3. I personally would not want to go beneath 300w per cab, just for headroom issues. A 3-400w head would be nice for one cab.
  4. I use a Peavey Pro 500, 350 watts @ 4ohms into either a Swr Goliath Jr. and Sob, or a 4 ohm Aguilar GS212. This is plenty of power for my gigs, mostly small clubs and usually with pa support. For outdoor gigs, I'll add a power amp.

    So to answer you question, yes 350 watts can drive (2) 8 ohms cabs. Whether it'll work for you or not depends on your situation...type of music, size of clubs, loud drummer, guitarist, etc.
  5. Justyn


    Jun 24, 2002
    Richmond, VA
    In some cases, it will depend on the speakers. I've used my Eden WT-300 head with Eden and Epifani speakers and never had a problem volume wise, but the Eden's have a pretty high sensitivity rating (103db SPL @ 1w/1m if memory serves) and the Epifani's are right up there around 100db, so 300w goes a decent way towards providing decent volume for me. It sounds like you're in a similar spot to where I was when I decided that my old Peavey TKO 80 wasn't cutting it anymore (though it still pumps out all the honky midrange and tubby bass you could ever want and it's going on 12 years old). I ended up buying the Eden head for both reasons of tone and value as it had just been discontinued and the sale price brought it into the same range as an SWR 350 or Workingman's 4004 and I preferred the Eden. I bought a 4ohm 212XLT to go with it and take advantage of all 300w and I've been very pleased. I later acquired some Epifani 8ohm cabinets and they've worked out very well for me.

    Now, I will say that at one point I was finding myself in a lot of situations where there was no PA support for the bass so I needed to cover a decent sized venue with just my rig and at that point I bought a power amp and slaved it off my Eden head to run multiple cabinets with more wattage and more headroom. I generally prefer to take as little gear to a show amp-wise as possible, so I'm a big fan of having modular pieces that I can mix and match as necessary and that I can buy or rent as I find a need for them.

    Some of it will also depend on what style your're playing and the kind of venue in which you'll be playing. I know a number of guys who bring a Workingman's 1x12 or a GK MB150 to a gig and just run a DI to the house, but that's if you've got PA support

    I feel like I may be talking a lot here and not offering much in the way of help, but overall I do feel that 300w is a good number for a great many situations, but there have been times when I've wanted a bit more as well.

    Hope that helps,
  6. Petebass


    Dec 22, 2002
    QLD Australia
    My rig is a 400w head through 2 reasonably efficient 8ohm cabs. I've played every type of room imaginable, from small bars to concert arenas, and it's never let me down. My rig can drown out drum kits and overpower all but concert sized PA systems .

    This rig cam about at a time when I was playing in an incredibly loud band and could never hear myself. I was using an older 400w head at the time. So I did an experiment where I borrowed a whole bunch of power amps, a couple of different preamps, and some bass heads, and auditioned each of them at a loud rehearsal. Apart from the band members, we had some of our sound crew members, some record company people, and band management present and they all heard what I heard - None of the power amps could match my old 400w head for volume even with the clip light flicking away, not even the 600w per side amp bridged into 1200w. We were going backwards.

    I then moved on to newer 400w heads (I tried Ampeg, Eden, very nearly bought a GK 1001b at 540w, but settled on an Australian made amp, the Ebony Quake 400) and found them to be the best option, probably because it is voiced for bass.

    There will be those that disagree. This all happened before I knew the mathematics of it all. Apparently doubling your watts results in an extra 3dB. To double your volume, you need to multiply your watts by 10. So based on this, a 800w amp isn't much louder than a 400w amp anyway.

    Of course SPL is a relationship between watts, speaker efficiency, voicing, and speaker positioning. You probably won't get your sound by focusing on watts alone.
  7. bino


    Jun 27, 2002
    Orange County
    This is great advice. How does running 1 4ohm cab differ from running 2 8ohm cabs? In other words, does the simple fact of having 2 cabs, despite the equal ohms, amount to a more inefficient setup or tax an amp more than a single cab?
  8. Petebass


    Dec 22, 2002
    QLD Australia
    That's right.

    Wether you're using one 4 ohm cab or 2x8ohm cabs, the amp still sees a 4 ohm load. The amp doesn't know or care wether it's one speaker or 2.

    The difference is in the efficiency (sensitivity) of the speakers. Doubling your speakers increases sensitivity by 3dB. Go back and look at the other way to get 3dB - doubling your watts.

    I can show you the maths if you feel like some bedtime reading to help you sleep.
  9. I think it's more than this, but can't calculate it. The addition of cone area does something too...
  10. No, Pete's right. For impedance purposes, the amp doesn't care if it's two 8 oms or one 4 ohm.

    And as for an earlier question, no, two cabs don't "tax" an amp more. That's a misconception, based on the mistaken view that speakers are somehow demanding power from the amp or trying to pull it out of the amp. Doesn't happen. Speakers are passive (albeit reactive). Amps pitch, speakers catch.

    Actually, you're likely to be louder with the two cabs, and thus to have *more* headroom (because you're getting more output for each watt, you won't need to turn up as high to get the volume you want--assuming your amp is capable of that volume to begin with).
  11. Petebass


    Dec 22, 2002
    QLD Australia
    1x4 ohm cab = 4 ohms
    2x8 ohm cabs = 4 ohms
    2x4 ohm cabs = 2 ohms
    1x4 ohm plus 1x8 ohm = 2.6667

    The formula for parallel resistance is :-

    1/Z = 1/R + 1/R

    So for 2 x 8 ohm cabs
    1/Z = 1/8 + 1/8

    1/Z = 2/8

    Z = 8/2

    Z= 4 Ohms.
  12. I'm not talking impedance or Watts (capitalize out of respect! ;) ) ... but assuming same sensitivities, etc: Will 2 cabinets each hit with 250 watts will sound louder than 1 cabinet hit with 500 watts?
  13. Petebass


    Dec 22, 2002
    QLD Australia
    Assuming all speaker cabs are identical, yes.

    More maths:-

    SPL = Sensitivity(dB) +10((log (watts))

    Lets assume they're identical cabs so they all have a sensitivity rating of 100dB on their own.

    1 Cab with 500w = 100+ (10*2.699) = 127dB.

    2 cabs with 250w each = 103 + (10*2.699) = 130dB
  14. Does this account for having twice as many drivers in the two cab setup, or are you comparing (for example) A single 4x10 at 500w with 2 2x10s at 250 each? I hope that's clear.
  15. Petebass


    Dec 22, 2002
    QLD Australia
    Doubling the speakers is the key. Remember that we have to assume that all the speakers are the same for the moment. That's important.

    Lets say you've got an 8 ohm Eden 2x10xlt. The sensitivity is 104dB. Adding a second 210xlt makes a total 4 ohm load, and it increases the overall sensitivity by 3dB to 107dB.

    Now have a look at the specs of the Eden 410xlt. It's no coincidence that the sensivity is 107dB, same as with a couple of 2x10's. So mathematically, it's exactly the same thing (provided all other things are equal which they often arent. Most 2x10 cabs have a different tuning of the porting than their 4x10 cousins, but that's a different thread).

    Just for another perspective, lets pretend out 4x10 is a different speaker all together and the manufacturer has made the cab less efficient in order to make it go deeper. Lets say it's sensitivity is 96dB.

    In this case the Eden 2x10 will be louder than the 4x10 when fed an equal number of watts, even though it's got less speakers.

    4x10 at 96dB = 96+(10*2.699) = 123dB
    2x10 at 104dB = 104+(10*2.699) = 131dB
  16. I use a yorkville xs400h with a yorkville xc410, and am adding an xc115 soon. It will be all I will need for playing clubs to medium sized gigs. It is a little muddier than I would like, but I can't afford an eden right now, and I am very happy with it. I would suggest it to anyone, lots of tonal variety and suitable for all styles.
  17. bino


    Jun 27, 2002
    Orange County
    thanks PeteBass. this is exactly the kind of math-geek talk i was hoping for. all i've ever heard about sensitivity is that the higher it is, the more efficient the cabs. but i read where you said lower sensitivity means more low-end. why exactly is that? and i've noticed that the larger, multi-driver cabs have higher sesitivities. is the box size simply playing a role in the sensitivity at that point?
  18. He didn't say exactly that--i.e., that lower sensitivity, in and of itself, guarantees more low end. I think Pete may have been referring to a common practical issue in speakers, which is that it is very difficult get a speaker that goes low, is loud, and is a manageable size. If you get two out of three, you lose something on the third. Thus, you can get a speaker that goes low and is loud, but it's likely to be very big and heavy. Or you can get a speaker that goes low and is a manageable size, but it's likely to be inefficient (e.g., Acme). This second trade-off is one a number of companies make, and I think it's what Pete was alluding to.
  19. Petebass


    Dec 22, 2002
    QLD Australia
    That's the laws of physics at work. With existing technology, it's a case of "loud, small, deep - pick any 2".

    Pro audio applications such as bass and PA enclosures have to be loud, so one of the criteria is more or less picked for us. That usually means that if we want to go deep, we have to sacrifice small. That's why a lot of PA's have 18" subs but cars can get away with a 10" sub that cover the same frequencies. In the car, the enclosed space means loudness isn't important. So by sacrificing sensitivity, the speaker can be small and low.

    There are of course a million combinations in between. A comon one is to offset the low sensitivity by using multiple drivers. That's how 8x10 and later 4x10 cabs were born.

    Not at all. Box size has nothing to do with sensitivity. Box size is determined by the speakers T/S parameters and is a function of the VAS and QTS figures.

    Sensitivity is measured with the speaker hanging in free air (ie no cab at all). They run a 1k sine wave through it at 1 watt and measure the output in dB at 1 meter distance.
  20. McHack


    Jul 29, 2003
    Central Ohio!
    There's some REALLY god stuff in here, thx Pete!

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