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4ohm vs 8ohm

Discussion in 'Amps and Cabs [BG]' started by Syxz_ML, Apr 10, 2012.

  1. Apr 10, 2012 #1
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    First time I post a thread on this site. Not sure if I have it on the right section so I apologize in advance if I don't. I own a Crate BT220 combo amp. 220 watts at 4ohm into a single 15" speaker. It has a external out put jack to add an external cab and it clearly states it connects it in SERIES and it recommends a 4ohm cab. I am currently building a custom 12" cabinet and am planning on putting in a 12" 4ohm speaker. From my research I know in the end it will make the output to both the internal speaker and the external cab lesser wattage and 8ohm to each. My initial problem is it just doesn't seem loud enough as is so wanted to expand into adding more speakers. My question is would it even be worth it to continue this project knowing my end results is more volume overall? A high end 12" speaker would be bought so assume quality of speaker doesn't matter here.

    I was told overall having the 2 speakers (1x15 and 1x12) at 8ohm wouldn't be louder and in fact might be at a lesser volume then running the single built in 15" at 4ohm like manufactured. I rather ask fellow bass players who have probably mixed and matched and have experience running these different setups.
     
  2. Apr 10, 2012 #2
    bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    It's an unusual arrangement, but yes the info you've been given is more or less correct. 4 ohms in series with 4 ohms is 8 ohms, and the amplifier will put out about 1/2 to 2/3 the wattage when given an 8 ohm load instead of 4. So you gain roughly 3 dB by adding the extra speaker, but then lose roughly the same amount by cutting the wattage. It's a wash.

    However, there is a potential benefit: odds are that cranking the full wattage into just the one speaker will have a higher risk of blowing out, or just wearing out, that speaker--while sending a smaller amount of wattage into TWO speakers dramatically decreases any such risk. So you would be much "safer" cranking that amp plus extension cab up to a high volume.
     
  3. Apr 10, 2012 #3
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    That is a interesting and beneficial point I hadn't thought off. But say again my main concern is not enough volume, and I go this route to just take a lesser strain on my individual speakers. I can see how cranking it up louder now that it's 8ohm in a pair of series connected speakers will be safer. But if I am already cranking up to about 3/4 on the master with the single 15" 4ohm setup and don't find it loud enough, do you think I will be able to crank it up loud enough to match the same db output I currently have with the pair connected in series at 8ohm? Or do you think I'll end up turning the knob to 11 (haha) and have a lesser wattage strain on the pair of speakers but wouldn't match the same db volume I currently have and am not satisfied with?
     
  4. Apr 10, 2012 #4
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    Also I should add part of the problem might just be that I am a pretty tall dude (around 6'1") and by not loud enough might be just not loud enough for me to hear since, depending on the size of venue, I'm so close to my amp that it just hits my knees. So again stacking up higher with lesser strain on my speakers and if anything similar volume might help enough. And as for the reason I'm making a custom 12" cab for this setup is just because I happen to have a empty 12" cab lying around but originally would of bought a 2x10 cab to try this out.
     
  5. Apr 10, 2012 #5
    walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    someone will be along shortly to point out that a more closely matched 15 cab will likely give better results than some other configuration, but...

    what about putting an 8Ω 15 in the amp, and re-wiring the extension jack for a more normal parallel out?

    then, you could wrangle another 8Ω cab (ideally, another 15 of close to the same specs), at which point you'd have a 220W, 2x15 rig, with the top cab closer to your ear.

    that might actually rock a little bit.
     
  6. Apr 10, 2012 #6
    walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    the series thing is just dumb, my guess is that this was the [DEL]designer's[/DEL] marketing dept's attempt to have their cake and eat it too, by selling a combo that put "full power" into its internal speaker but still had an option for an extension cab.

    you'd likely be better off just putting it on top of the extension cab and leaving that cab unplugged.
     
  7. Apr 10, 2012 #7
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    Coincidentally earlier today I called the guitar/amp tech I took this combo amp to when it was still in warranty and asked about getting that done. I am fairly new to the whole DIY rewiring aspect of things when it comes to speakers/cabs/amps etc so me personally rewiring my external jack would be to advance for me. He mentioned some BS about "well the amp is specifically made for a 1 speaker 4ohm setup so trying to rearrange that would be risking the amps original setup blah blah blah"....... I could tell it was just someone not trying to be helpful with their knowledge (reason why I finally joined this forum). I knew installing a 8ohm 15" into the combo and making the external jack PARALLEL with another 8ohm speaker would be fine with my 4ohm amp.
     
  8. Apr 10, 2012 #8
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    One possible incentive of maybe leaving it as it though would be that not all shows I play are big venues. The combo, as is, weighs a ridiculous 87 lbs already so for those shows where I don't need that much I can just take the combo by itself knowing I'm still playing off one 15" speaker at its full power. Less stuff to carry around for every show when it's not necessary.
     
  9. Apr 10, 2012 #9
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles

    haha consider that taken into VERY MUCH consideration

    but yeah I definitely agree CRATE were just being jerks when it came to making this combo amp. Might be reason why they fell under or better yet just attached themselves to the AMPEG name to get rid of that bad reputation.
     
  10. Apr 10, 2012 #10
    Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    There is NO winning that debate.......

    A) Combo amp will drive 4 ohms , has an 8 plus parallel extension speaker jack...

    "You mean those creeps make me buy and haul ANOTHER speaker JUST to get the power I paid for? Who thought THAT was a bright idea?"


    B) Combo amp will drive 4 ohms, takes NO extension speaker

    "You mean I CAN'T EVER connect another speaker to that POS? I wanted to drive a 410 with it..... but I can't .....Who thought THAT was a bright idea?"


    C) Combo amp will drive 4, has a 4 ohm, has series extension.

    "You mean I can't get full power if I hook up a second cabinet? "yeah I definitely agree CRATE were just being jerks when it came to making this combo amp."

    There is absolutely NO WAY to satisfy everyone on this point.

    At least you can get the advertised power as a combo....... the way you seem to prefer you would fall under "idiot idea 'A' as per above" instead of "idiot idea 'C' that you seem to prefer.

    ALL solutions will have somebody complaining.
     
  11. Apr 10, 2012 #11
    jefkritz

    jefkritz

    Oct 20, 2007
    Madison WI
    not really about the other cab, but might help you anyways.

    i used to always have trouble hearing myself (i'm also pretty tall). now, i slightly angle my amp up when i play a gig. this helps tremendously.

    you don't need a ton of angle - i never really lift the front more than 4". i generally just hunt out something at the venue for this purpose. the packaging for 50-cd packs work really well.
     
  12. Apr 10, 2012 #12
    walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    "ALL solutions will have somebody complaining."

    ha!

    jerrold's point about compromises is well-taken, but typically, the volume difference from the power developed between 4Ω vs. 8Ω on one speaker is not as obvious as the improvement gained by adding a cab.

    if you're cranking the amp, my understanding of this stuff is that you're probably hitting the ceiling of power compression from the speaker before you get anywhere near 220 watts anyway; therefore, the power loss from swapping in an 8Ω speaker is actually not that big a deal.

    adding a cab and getting more amp power in the bargain (like you would in parallel) will make a big difference.

    that's why "real" bass amps don't fool with series cab connections.
     
  13. Apr 10, 2012 #13
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    Alright I'm starting to get an idea of what the end results might be. I am the type that likes trial and error and visually seeing for myself the results. So I think I'll continue this little project and see the results. If anything I might ditch the 12" cab and just buy a empty 2x10 cab and set those speakers of 8ohm in parallel only for the reason that it's a BITCH to find 4ohm 12" speakers. 8ohm speakers seem to be everywhere. In the end if all fails I can just stack my combo on the 2x10 and not even connect it rather then angle it ha ha
     
  14. Apr 10, 2012 #14
    JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Best to appreciate budget combos for what they are and not try to make them something they're not. You can always use a cheap inexpensive combo for when you're knocking around or when you're doing small gigs where an 810 is inappropriate.
     
  15. Apr 11, 2012 #15
    Syxz_ML

    Syxz_ML

    Apr 10, 2012
    Los Angeles
    Yeah very true. Guess my needs have exceeded my expectations for this combo amp and it's time to upgrade. But having this around as a secondary/back-up/small gig amp will be very handy. Appreciate all the feedback and knowledge in this forum.