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Acoustic 220 Head, What speaker do i need?

Discussion in 'Amps and Cabs [BG]' started by Lemming16, Nov 27, 2010.

  1. Lemming16


    Oct 13, 2010
    Hi everyone, i just started playing bass (after years of playing guitar), and i got on a Pawn shop an Acoustic 220 head working perfectly for $100. So all i need now is a cab. Since all cabs here in Mexico (just as all new music instruments) are a total rip-off, i decided to buy a speaker and make a custom cab.

    My question is, how many watts, and ohms should the speaker be? And what size do you recommend?

    Most of the shops here in mi city have only Eminence Delta, at fairly good price, (i noticed most of them were 8 ohms) i just need to know if i could use those with 8 ohms or if i should look for 4 ohms speakers, and how many watts do you recommend.

    The specs of this amp are: (You can see the full specs here http://acoustic.homeunix.net/twiki/bin/view/Acoustic/BassHead220)

    160 Watts RMS @ 5 % THD into 2 ohms
    125 Watts RMS @ 5 % THD into 4 ohms

    then on the other add it says (even though its the same model)

    210 Watts RMS @ 5 % THD into 2 ohms
    170 Watts RMS @ 5 % THD into 4 ohms

    What do you recommend?
    Thanks in advance.
  2. WOW! Look at the size of that electrolytic in that thing!

    I hope this head is working - as those caps can get funky after a few years.

    Since this is obviously a Solid State amp, there are a lot of areas that aren't as finicky as a tube head.

    The Ohms rating is the lowest level, not a limit that you HAVE to hit, nor do you have any troubles if the drivers (speakers) are higher, say at 4 Ohms.

    As Ohms go DOWN - Watts go UP. To a point!

    At 8 Ohms for a driver load, the amp won't be putting out the highest Wattage, although this is not a problem.

    For a decent guess, the 8 Ohm driver will get you about 66% of the Wattage from the amp that the 4 Ohm load would theoretically be.

    There are sonic losses and although the true arithmetic says you'll get 50% less Watts for 50% more numerical values for Ohms, the drivers aren't as efficient at lower power - but that's a trade off too.

    It's kinda complicated. - but a 4 or 8 Ohm cab won't hurt your amp, in fact the amp can coast a little with the lower demand on it.

    Hang on for more input though - there might be an irrational problem with that amp of which I am not familiar.

    Most of the techs and guys who gig are working tonight and they can answer your questions when they get back or when they get up in the afternoon tomorrow.
  3. Lemming16


    Oct 13, 2010
    Whoa, thanks for your answer, so, do you think i should get a speaker with 200 Watts? (8 ohms) or one with 300 watts? (8 ohms too).

    Since is not clear if the watts on my amp are 120 or 170, lets suppose my amp is 150 watts (at 4 ohms) . What speaker would you recommend? 200 watts or 300 watts (both at 8 ohms).
  4. CrimsonGhost


    Nov 14, 2000
    Those heads are HIGHLY underrated for power i used to run a 2x15" with mine and shake the walls in my house. I forget what ohm rating it was though..
  5. OK - you amp is CAPABLE of sending Wattage at that Ohm rating - it doesn't HAVE to be at that Ohm rating - since that is the lowest limit for the amp. Just don't go below it.

    I'd go for the most Wattage in the drivers (speakers) and that 8Ω load allows you to add more cabs/drivers later.

    An 8Ω cab added to another 8Ω cab equals 4Ω.

    You would still have 2Ω to play with and that's giving you a safety - or fudge zone for the amp.
  6. Lemming16


    Oct 13, 2010
    Hi everyone, thanks to all of you, you all were big help, tomorrow i'll be getting the Eminence Delta 15A of 300 watts. Because of budget and space, i can't add another.
    I just hope the speaker works fine. Or what do you think? Should i get another speaker?
  7. Ultimately - yes. Get another driver.

    You're going to find that you might be able to fart the 15" driver in that cab if you push it too hard or with too much BASS bias.

    Just listen to it and make sure you don't hear it 'death-rattling' - which might be the floating coil and what is called 'the linear motor' of the speaker, hitting bottom of it's travel.

    You can only get away with that a few easy times before you break something. Just listen to it!

    It's only paper and maybe some silk or tape and some glue and very fine wires.

    There are formulas and theories which also abound and you'll prolly hear or read about SPL and cone-travel and other dynamics. - but your ears will tell you when it's in distress.

    Then you back off the VOLUME and cut the BASS or LOWs.

    Ya know for later on, twin 15's are great and give you a lot of air-motion and that's what a bass needs - to move air!

  8. I guess I'll be the first to address the issue...........

    If you don't know about watts, ohms, etc....... then you probably have no business trying to build a cab.

    Throwing a speaker into a box is a crapshoot at best without knowledge and planning.

    You need to know all the speakers T/S specs, and be able to use those specs to make the proper size box with the proper porting/tuning.

    My suggestion is to find a used cab.
  9. Ya know what? I missed the 'make a cab' part.

    Gack! Where wuz I?

    Buy a cab with a 115 in it. Really, Seriously.

    I thought he was agonizing over two different spec'd cabs. Jumpin' Jehosaphat!
  10. Lemming16


    Oct 13, 2010
    Oh no, my english is bad, what i meant, was that i was going to buy the Eminence 15-A 300W, and take it to a technician, so he could make the cab with the speaker and the tuning.

    I'm only gonna buy the speaker, he'll do everything else.

    I'm not sure what do you meant with "porting/tuning", i guess the tech would know. Thanks for your help man. Any other suggestions would be greatly appreciated. I'm also thinking bout buying this cab http://gamamusic.com/producto/12593, even tough its much more expensive, what do you guys think?
    (Keep in mind im on a really tight budget, and im not sure if its gonna be a big difference between a custom and a brand one)
  11. I bet you'll love that GK a LOT!

    Later on find a 115 in the same brand to stack on it and you're good as gold.

    I find the GKs a little too modern for me, but they punch pretty well with the right head.
  12. Lemming,

    I need to let you know that I think you have a great amplifier head in your possession, however you aren't going to get the most out of it unless you are running a 2 Ohm load. I understand money is tight for you and therefore I think you will save money by getting a local tech to build you cabs instead of buying an 8 Ohm G-K 2X10. Not only does the impedance matter in regards to how much volume you will get, but so does the amount of speakers. There were a lot of people who used this amp back in the day with 2 2X15 folded horn cabs, and totally pounded, that is 4 8 Ohm speakers in two cabinets. I wish someone like BFM or GreenBoy would come on this thread and tell you what driver you should choose, but in my opinion and experience you aren't going to get what you want out of this head without sending as many available watts as you can into the cabs and having as much cone displacement as possible. If you honestly think that you will never realistically have the money (or need to be that loud) for 2 2X15 cabs, save up your money until you get 2 15 inch drivers and settle with one cabinet that houses 2 4 Ohm speakers. I hope this helps, Cheers.
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    A cabinet builder who knows what he's doing will choose and supply the appropriate driver. If he's told you to go out and choose your own driver he doesn't know what he's doing.
  14. Bill - that's the same thing I told him in a PM, and now he's decided to try the GK 210 and perhaps add a 115 on top of it later.

    He conceded the point that a cab is much more technical than a wooden box, which I think he might have had commissioned by possibly a cabinet maker without audio cabinet experience.

    Sorry to all who noticed that I never noted he was talking about BUILDING a cabinet, when I thought he was just trying to decide on two different loaded cabs.
  15. Thank you for showing up Bill, I completely agree with you. Joe, I don't know you from a hole in the ground, but respect you as a person. In this particular case I think you are totally wrong. I know he is not going to be happy with a 8 Ohm 2x10 even with adding another 8 Ohm 1X15 cab later.

    What he needs to do is get a hold of a former TB'er named vetchking (This is the original designed of the pre-GC Acoustic line) and ask him for specs on a folded horn 2X15 cab. Then buy the correct (not necessarily vintage) drivers and put them in a correctly specified cabinet. And in regards to what is actually necessary in regards to total cone surface, if he doesn't think he is ever going to need to play large shows without PA support, he should get each 15 inch driver @ 4 Ohm impedance for a total load of 2 Ohm in one 2X15 cab.

    Once the specs are given it doesn't matter if it is a cabinet maker who has only ever made cupboards and dressers in the past. He is trying to get the biggest bang for his peso and I think paying a local builder is A LOT more cost effective than paying G-K to ship him an overpriced low quality MIC 8 Ohm 2X10 cabinet, even if he adds another 8 Ohm 1X15 later. Cheers.
  16. Well - you haven't been privy to the PM - and I'll not divulge any of the really odd particulars here

    ----- but he was thinking of a box.

    Yes - a box with a speaker in it.

    A box made from some boards with a speaker in it.

    That's a far cry from getting plans, a pair of 15-inch drivers ($$) and having a 'box' built to those specs.

    If I understand your chagrin with me, it's that I didn't tell him to spend a small fortune on a pair of 4Ω X15 inch drivers, and try to get the plans from someone else to make him a better box, when there are so many real boxes already out there to be had for a lot less trouble and money.

    We aren't even talking networks and HI/LO band-pass, female 1/4" jacks, tuning, porting, stuffing, wiring, type of glue and size of nails to hold it all together.

    He wanted to stick A speaker in A box made from SOME wood.

    I told him to get a commercially available cab and then he can add to it later, and I'm gonna stand on that as it's a pretty sound idea.

    I know about the 2Ω preferences for the amp - but he's gotta start somewhere, and the shortage of 2 or 4Ω drivers would make getting something done before he retires a little tough.

    I even bet that given the possibility that he gets a 210, it'll have two 8Ω-ers in it - and HEY! Ya know what? I bet we can move a wire or two and get him to (son-of-a-gun!) 4Ωs.

  17. Lemming16


    Oct 13, 2010
    Hi guys, guess what, im about to get this bass 4x10 cab... for $200 bucks.


    What do you think? Do i pull the trigger? I think i'll never find something like this again.
  18. I've never seen that product line - but the specs sound good.

    Any time I see Speakon in the specs, it suggests to me that there's some professionalism in it somewhere.
  19. Lemming16


    Oct 13, 2010
    Apparently, its a company from Taiwan, i guess its better than China, i've seen here in Mexico those amps are quite popular, but never tried them myself.

    Since they are a registered company, have a website and they say its a bass cab, i guess it would be good. I hope.
  20. When/if you get it, there can be some 'magic' rewiring to get your drivers closer to that 2Ω limit too.


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