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cab problem

Discussion in 'Amps and Cabs [BG]' started by wotnwhy, Jun 24, 2003.

  1. i've recently bought a peavey combo115 amp and the 210 TVX ext. cab

    the combo has a 1x15" speaker and is 200w@4ohms and 300w@2ohms, the cab is a 2x10 and is 175w@4ohm.

    i absolutely loves the thing, it has great tone, plenty of punch, loads of bottom, and plenty of volume, HOWEVER my band does a couple of reggae/dub songs, and for this there needs to be LOADS of bass, which the 1x15 can handle fine, but the 2x10 tends to stuggle with it, especially on the low B. the output for the ext. cab it just a 1/4" jack, with no controll over it. is there any way to limit the lower frequencies being sent to the 2x10, as it sounds quite naff, and i'm sure it's not good for the speakers ;)

    a friend suggested putting an EQ pedal between the amp output and the cab input and cut the low frequencies on that, would that work?

    thanks for your help

  2. jondog


    Mar 14, 2002
    NYC metro area
    No, don't put an eq there. You'll fry it.

    With that setup, I'm not sure how to keep your 10s from seeing the lows.
  3. Can't you get a crossover and divide the frequencies or something like that.
  4. the amp has crossover with high and low outputs and a frequency pot (.2 to 2k), i don't know that much about amps, and i looked in the manual about it and it was talking about bi-amping with a seperate power amp.

    is it possible to use this at all?

  5. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    Sure you can bi-amp. You go from the high frequency output of the crossover built into the amp into a seperate power amp and then to your 210.

  6. trouble is i don't have to money to buy a power amp

  7. If you're willing to experiment, get a speaker crossover capacitor (they are specially made non-polarized electrolytic capacitors) of about 220 microfarad, 50 volts AC. That's for a 4 ohms cabinet. If your cab is 8 ohms, get a 100 microfarad one. I'd expect it to cost no more than US$10.

    Put the capacitor in series with the speaker cable to the 2x10. That means interrupting the positive lead and placing the cap in between the two ends. Make sure the 2x10 is the only cab on the end of that cable.

    If you like the result, you could put the capacitor inside the cabinet with a bypass switch, which shorts the capacitor.

  8. Petebass


    Dec 22, 2002
    QLD Australia
    Question - to me this looks like a high pass filter with a 6dB per octave roll-off. Is 6dB going to be enough? What frequency have you used to get these capacitor values (it would have to be highish if it's only a 6dB roll-off)?

    I'm not second-guessing, just trying to learn a bit.......
  9. as i said, i don't know much about amp (i know a little about electronics, i did a bit at college)

    when you say "Put the capacitor in series with the speaker cable to the 2x10" i'm not quite sure what you mean

    each speaker is 8ohms, but the cab is rated at 4ohms, if thats helps or makes any difference

  10. Petebass


    Dec 22, 2002
    QLD Australia
    it's pretty simple. Have a look at the attached diagram. YOu need the one on the right.

    All he's saying is that the signal going through the positive part of your speaker wire should also go through the capacitor. The capacitor will filter out the low frequencies that are causing the farting.
  11. ah yes, i get it now, i was thinking he meant the speaker cable going from the amp to the cab.

    i've got a gig tonight with the rig and i think i'm gonna try just unpluging the 2x10 and let the combo do all the work, if it can stand it i'll just do that for the heavy bass songs. if it can't handle it i think i'll have to try out the capacitor idea

    and would i be right in thinking this will completely void any warranty? ;)


    P.S. thanks again for all your help :D
  12. Petebass


    Dec 22, 2002
    QLD Australia
    Actually that is what he meant. He was suggesting you put the cap on the speaker cable at first to try it out. Then if you liked it, you could move the capacitor inside the cab permamently. You'll have to make up a speaker cable especially for it though.

    the cap will work as long as it's on the positive wire, regardless of wether it's inside or outside the cab.
  13. Yes, I meant to say to put in the cable, as to not void your warranty. The ideal solution would be to build an adaptor cable with the capacitor in it.

    And, you'd have to take the rating of the cab, not the individual speakers. It's 4 ohms, so get a 220 microfarad capacitor. Get a larger one (or put an extra smaller one besides the one you got) if you tried the 220 and you feel you need more midbass.

    Pete (and wotnwhy), the crossover point is roughly 200 Hz with the given value, this will attenuate the lowest frequencies by at least 12 dB. IMO enough to not let the cab fart out. Building a 12 dB/oct crossover is considerably more expensive because low freq. coils are large and heavy (=expensive, think $20).
  14. Petebass


    Dec 22, 2002
    QLD Australia
    Thanks Joris. I understand now.

    The other problem with inductor coils is that they're hard to find in Australia with an Air core. I tried using ferrite cores and they work OK for low power applications, but distort a little at high power.

    I've been toying with a 12dB/oct high pass filter that's set the tuning frequency of a cab I built (75Hz).I hadn't even considered using Caps only and raising the frequency. I might try this.......
  15. i did the gig last night and it was really good* there weren't any problems at all with the cab at all. which is quite wierd...

    i've got another gig on saterday and it's a much larger hall gig, so i'll see how that one goes.


    *it was good, except for the fact that someone threw-up all over my pedalboard :mad:
  16. Piezoman


    Nov 29, 2002
    Bronx, New York
    Is a 10" speaker that inadequite for handling a low B cuz I use the B string alot in my band.
  17. it's not the size of the speaker thats important, a lot of 15" speakers can't handle a low B, it depends on the build quality and what the speakers were designed for.

    and unfortunatly in my case the speakers simply weren't designed to take a very loud and bass heavy low B. but there are loads out there that can.

    hey, thats a thought. if the fart becomes more of a problem i could always upgrade the speakers :rolleyes:

  18. Petebass


    Dec 22, 2002
    QLD Australia
    Yeah I worked for free last night too. Some drunk a-hole smashed a window on my car just for the hell of it.... not happy......