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rewiring speaker cabinets

Discussion in 'Amps and Cabs [BG]' started by townsley, Dec 13, 2003.


  1. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    I wasn't paying attention when I made my purchase. I bought a 300 Watt/4 Ohm amplifier and a 400 Watt/4 Ohm speaker cabinet. The problem is that I intended to add another cabinet to round out the sound. I've read that there are ways to rewire a 4 Ohm cabinet to increase the impedance to 8 Ohms and thereby permit me to get a 2nd, 8 Ohm cabinet. Is this just a bad idea or is it practical? Are there any devices that sit between an amp and a cabinet and allow for impedance "balancing" for lack of a better word?

    Also. Though my amp says 4 Ohms, the User Manual states that the "minimum impedance is 2 Ohms." I don't want to damage my amp, but if the 2 Ohms is the minimum, could I just add a 2nd 4 Ohm cabinet to the setup without causing any damage/problems?
     
  2. You cannot rewire a 4 ohm cab to make it 8 ohms. I don't know where people keep hearing this.

    Do a search, every few months this question keeps popping up in this forum.

    If you have a cabinet with more than one driver, if you disconenct or bypass one or more of the drivers, you WILL change the impedance of the cab. But...you will then have one or more of the drivers not running, just flopping around, which is not good.
     
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    If you're referring to the Carvin 210 cabinet in your profile, it has two 8 ohm speakers wired in parallel, giving you a 4 ohm cabinet.

    If you connected the speakers in series, you'd have a 16 ohm cabinet.

    Can the Behringer go down to 2 ohms...I seem to recall that the markings near the jacks say 4 ohm minimum.
     
  4. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    It *is* the Carvin 210 in my profile. Thanks very much for your input on this. It seems that rewiring the RL210T is really not a smart optiion. So, given the situation I'm in - a 4 Ohm amp and a 4 Ohm cabinet and a desire to have 2 X 8 Ohm cabinets...what can I do. I'm not asking if it will be easy, just if it's possible and/or whether it's been done before...Can I create some sort of Radio Shack weirdness that increases the impedance of a 4 Ohm cabinet to 8 Ohms? I just want to increase the impedance so that I can attach 2 X 8 Ohm cabinets to this 300 Watt/4 Ohm cabinet and not cause any harm.

    Thanks in advance for any help any of you Big Brains can offer - you all Da Men, or Da Women, or Da People - whatever works for your own personal situation.
     
  5. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    There is a solution that involves keeping the Carvin, but it would be heavy, expensive, etc. You'd need an impedance matching autotransformer that has taps at 4 ohms and 8 ohms, has excellent frequency response, high power handling, low distortion, etc. Seems to me that Peavey sold such a thing in the past.

    How long have you had the Carvin? Can you still return it?

    You might be better off selling the Carvin and picking up an 8 ohm 2x10 from someone like Avatar www.avatarspeakers.com. It is a popular cabinet here, received a good review from Bass Player and can be had in either 4 ohm or 8 ohm impedances for between $218 - $229 plus $29 shipping (the price range comes from Dave's starting price on eBay and the regular price shown on the web site).

    You could do some additional research on the Carvin's cabinet design (volume, tuning freq., etc)and see if the Eminence Delta 10s would work well if you swapped speakers. The best price for these (you'd want two 16 ohm speakers for an 8 ohm cabinet) that I've found are also from Avatar. The Carvins (also made by Eminence IIRC) could be sold off.

    Lastly, you could have your speakers reconed with 16 ohm kits, but this would probably cost more (check out www.webervst.com) than buying new Deltas from Dave (at Avatar) and selling off the Carvin speakers.

    Have fun!!!!
     
  6. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    OK - maybe I don't have a problem here, other than not understanding impedance very well... What about this - my amp has 2 parallel outputs running 300 Watts at 4 Ohms. So, I CANNOT connect 2 x 4 Ohm cabinets in parallel, one to each amp out. However, maybe I CAN connect 2 x 4 Ohm speaker cabinets in series? That is, my cabinet has an input and an output port for daisy chaining. Couldn't I connect 2 x 4 Ohm in series for a total impedance of 8 Ohms?

    That would essentially hamstring my amp, though, right? 8 Ohms of impedance would turn my 300 Watt amp into a 150?
     
  7. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    Daisy chaining those cabs won't put them in series, but parallel instead. The inputs/outputs on your cabs are very likely wired in parallel. If you were to daisy chain the two cabinets, it would be no different than if you were to connect them each to one of the parallel outputs on your head.
     
  8. aladdin

    aladdin

    Mar 7, 2003
    Chiba, Japan
    This link might interest you. It interested me!

    Speakermate

    It is the only commercial "magical box" that I have seen so far... any others? Anyone?

    -Aladdin
     
  9. miccheck1516

    miccheck1516 Guest

    Feb 15, 2003
    Ireland
    yeh the manual says the behringer's minimum impendence is 2 ohms, well it used to, i think theyve fixed it now.

    How does the behringer sound? im thinking of getting one.
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I've done this before but it requires a specially made set of cables and it proved a bit cumbersome. My situation was different to yours in that I wanted to run 4 speakers, so I went and bought a speakermate.

    I had some lengthy conversationes with the inventor, Gilles, vie email. He said he was developing a new product called "speakermatch" that will solve all sorts of impedance problems. I think it was designed for those who have mismatched cabs, eg one 4 ohm and one 8 ohm, but it might help in this situation as well. Might be worth a look.........

    MOre like 200w actually. As a rough guide, halving the impedance gives 70% of the power or thereabouts.
     
  11. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    I *just* started reading about the SpeakerMate. There seem to be a LOT of opposing opinions, but most of those on the negative side haven't actually bought a SpeakerMate. Those who have state that it actually does what it says it will. I think I'll go with that option. I'd really like to get 300W at 4 Ohms out of 2 cabinets, rather than increase impedance.

    As far as the Behringer goes...I just got it and, so far, it sounds really really good. I am TOTALLY satisfied. I don't know how it will be in the long term, but for $200, I'm very pleased - it sounds great!
     
  12. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    So I emailed Sherlock Audio and asked them whether SpeakerMate would solve my problem. Interestingly enough, the creator of SpeakerMate said no. Here's his reply verbatim:

    "Hi bill,gilles here.You're right-that combination isn't on the site because
    SpeakerMate can't do that. SpeakerMate was designed to operate multiple matched pairs and mismatched
    three-cab setups.
    However,there IS point you might want to consider.Even if you were to run
    both your cabs in series, for a load of 8ohms(speakermate can do that also)at 150watts,many times,you "gain back" any power
    loss thru the fact that there's an increase in SPL level from the second cab
    as well as increased coverage(radiation pattern)from that second cab as well.
    Honestly,pretty much every hookup for each SpeakerMate model is on the
    website.These are all the ones that have consistently worked for everyone that has bought them for many, many years,here in Canada and abroad.
    Your particular request isn't that uncommon though, which is why we've
    developed a new,
    more elaborate unit that WILL DO that,as well as about another 2dozen
    impedance matching tricks. This unit,to be marketed as SpeakerMATCH will be available the first quarter of 2004.We have a number of protypes that have been "on tour & in-studio" ,being used & abused
    till they're ready to be finalized for production.Any updates for SpeakerMatch will be appearing on our website first.I was hoping to have this unit ready before that,but frankly have been overwhelmed by the response and orders(!) for SpeakerMate
    units,so that'll get priority first as I get caught up.
    Let me know if you need more info.
    Thanks again for your interest in our products.
    Gilles Grignon
    Sherlock Audio Canada"

    Now I'm even more confused than before. Can anybody decypher what he's talking about with that "gain back" stuff?
     
  13. 44me

    44me

    Jun 17, 2002
    Bedford, NH USA
    There are no impedance matching miracles performed by speakermatch. It just appears to be a cleverly designed switch to connect speakers together in the appropriate series/parallel combination to get an impedance close to the desired value. Study the Speakermatch diagrams carefully – they do not imply that you can get a 4 ohm load from two 4 ohm speakers. Your only options are either 2 ohms, by connecting in parallel, or 8 ohms by connecting in series. If the two cabinets are similar in design (preferably the same), than other than the impedance difference, the series connected cabinets will perform the same as the parallel connected cabinets. However, if the cabinets have grossly different tuning, the series connection may have noticeable poorer performance. It all depends on how each cabinet’s impedance changes with frequency. Ported bass cabinets usually experience very large impedance changes near their lower cutoff frequency, which can effectively limit the low frequency power delivered to the lower tuned cabinet in a series connection.

    I recommend that you simply try connecting the two cabinets in series and see how it sounds. This connection is much easier on your amp than the 2 ohm parallel connection. As Petebass mentioned, you’ll loose more like 30% of the max power, but you’ll pick up more than that due to the efficiency improvement of adding more drivers.
     
  14. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    44me - how do I serially connect the cabs? My amp has 2 parallel outputs, and each cabinet has in input and an output. From what I understand, speaker cab outputs are almost always wired in parallel. How do I get a series setup?
     
  15. Petebass has the answer. You will need to make/purchase custom cables. Basically, you will need one cable from the ampthat splits off into two, one conductor to each cab. you plug them both into the + side of the speaker (the tip of a 1/4" plug and then take two more 1/4" plugs and connect the sleeve conductors (ground) to gether. This cord would plug into the "output" jacks on your speaker. Either one actually, since the input and output jacks on a speaker are wired in parallel.

    And as for your amp outputs, those are wired in parallel too, so in normal operation, connecting a cable from each speaker to the two outputs is the same as connecting one speaker to one output and the other speaker to the "output" of the first cab.

    Confused? PM me and I'll try to do better. In the mean time, here's some humor about how ohms work.

    How ohms really work

    Stay low,

    BT
     
  16. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    As Petebass mentioned, it requires a specially made set of cables to connect the cabinets in series.

    The plug that goes to the amp is wired normally, the + lead goes to the tip of the plug for cabinet number 1, the sleeve of plug number 1 is connected by a single wire to the tip of the plug for cabinet number 2, the sleeve of plug number 2 is connected to the sleeve of the plug that goes to the amp.
     
  17. Let's try this again.

    If you have two jacks on your speakers, you will need two cables. One from the amp that splits and goes to both cabinets, and one that plugs into both cabinets. The amp end is normally connected. the opposite end of that cable splits into two single conductors and each is wired to the tip of a 1/4" jack.

    The other cable is a single conductor wired from sleeve to sleeve and goes from one cabinet to the other.

    If your cabs only have one connector each, you'll only have one cable but it will have three wires connecting the the plugs. One will be normally connected and go to the amp. the two leads of this cable will go to the tips of the two other jacks, and the two sleeves of these cables will be connected together. Now is that more clear?

    Billy B I think you meant that the sleeve of plug #2 connects to the sleeve of plug #1. Otherwise you have an open circuit.

    BT
     
  18. townsley

    townsley

    Nov 10, 2003
    Portland, OR
    Allright folks - I think I've got it now. SpeakerMate can actually do that as well, but to the tune of $105 including shipping. I think it'll be fun to try to wire up my own harness, so I'll give that a go. Thanks VERY much everybody. I really appreciate all the help!
     
  19. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Don't be confusing the speakerMATE with the speakerMATCH. They're different products.

    The "gain back" Gilles is talking refers to the way that speakers interact with each other. Generally speaking every time you double your speakers, you get an extra 3dB senstivity (loudness). A 3dB increase is pretty hefty when you consider that the other way to get an extra 3dB, provided your single speaker can handle it, is to double your watts.
     
  20. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Another, perhaps simpler, solution to the original situation would be to sell the current 4 ohm cab and buy a different 4 ohm cab that would not require another cab to be added to "round out" the sound.

    Sorry, just felt like taking a whack at the Gordian knot there....;) :bassist: