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Biamping with a double eq'd power amp

Discussion in 'Amps and Cabs [BG]' started by Eilif, Sep 15, 2005.

  1. Eilif

    Eilif Supporting Member

    Oct 1, 2001
    I just stumbled accross this idea. With a preamp could a 2 channel (each with 15 band EQ) power amp work to power a biamped bass setup (probably a 4x10 and a 1x15) The amp I found is this one:


    I am curious to hear what you all thought about the feasability of this.


    Also, if I only use one channel (not bridged) will it be putting out half the watts? Amps don't automatically bridge if only one channel is used, do they?
  2. Eilif

    Eilif Supporting Member

    Oct 1, 2001
    Come on now, someone must have some advice, can somebody help me out with this question?
  3. If a person wants to biamp I think it would be better to get a preamp with a real crossover in it and do it right. You have to have buy preamp to make that thing work anyway...right?
  4. I'm assuming you have a crossover, right? So sure you can use them for biamping. The high freq sliders on the 15 band won't do anything for the low channel, and the low freq sliders won't have any effect on the high channel.

    It would make more sense to have 1 graphic before the crossover, easier to see what you're really doing with the freq response. But the 2 work fine from a functional standpoint. You just have to remember where the crossover freq is in regards to the graphics bands so you can remember which sliders on the dual 15 band graphics actually have an effect on the signal.

    If you just use 1 channel of the power amp without bridging, you will indeed get 1/2 the watts. Unless you connect both cabs to the one channel, then you get around 50% more power due to the lower impedance load from 2 cabs instead of just 1 connected.

    For my money, I'd prefer to run full range, both speakers. Bridge the amp if both speakers are 8 ohms and the amp will support 4 ohm bridged operation, meaning the amp will drive a 2 ohm load per channel in stereo.

  5. I suppose you could use the dual 15 band graphics to act like a crossover, killing the lows from one cab and killing the highs from the other. A little unorthodox, but it would be close enough.

  6. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    You can also just use each EQ to kill problem interactions between the two cabs, so they're both close to full range, but each does what it does best. I've run rigs like that plenty of times, works great IMHO.

    Also, if I only use one channel (not bridged) will it be putting out half the watts? Amps don't automatically bridge if only one channel is used, do they?

    You need to look at the per-channel ratings at various impedances, you might easily end up at ~1/4-1/3 power given the same impedance. Check it out : http://www.carvin.com/products/dcmseries.php

    So if you run a 4 ohm load bridged with that amp, you get 1000 watts, and running one channel at 4 ohms you get 350.
  7. SteveC

    SteveC Moderator Staff Member Supporting Member

    Nov 12, 2004
    North Dakota
    If you want to biamp - get a real crossover and do it right.

    I don't think much is gained by biamping any more. Cabs and heads are way better than they used to be.
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Not really. The maximum cut you'd get outside the passband is 15dB. Even a third order/18dB octave slope crossover will cut power by 18dB at one octave, 36dB at two octaves, 54dB at three octaves and so forth. If you were biamping a fifteen and a ten that wouldn't be such a big deal, as the ten wouldn't be particularly stressed. Try it with a woofer and a compresson horn driver though and the horn driver would be toast.
  9. Right, but his "high" driver is a 4x10, if it has a tweeter, it's already crossed over in the cab, no harm in this case. You'll cut the highs mostly off the 15, which just preserves power for the freqs it can handle, not for speaker protection, and cut lows off of the 4x10, again, not freqs that would tend to damage the cab anyway.

    I'm not arguing its a good idea or anything... just that it'll give you some sort of an approximation of biamping.

  10. Eilif

    Eilif Supporting Member

    Oct 1, 2001
    I should clarify:

    I don't have a crossover, my intention was to run my ampeg portabass into this amp and trim the eq's so I can push both cabinets and take out the frequencies that might blow the 10 inch speakers. I'm not too worried about the 15" but I don't want to put too much low b into a high powered setup and blow the 10"s.
  11. brothernewt

    brothernewt Some people call me the stormtrooper of love...

    Apr 13, 2004
    Happyrock, OR
    I do think that would work... if you're running both full range, you could use each eq to tweak frequencies individually for each cabinet. Smooth out the 10, tighten up the 15... It sounds overly complicated to me though, it would be too much work for what I play.
  12. You have 4 10's which gives you about as much cone area as a 15. So the 10's are in no more danger of being blown by the low B than the 15, its more dependent on cabinet tuning than individual driver size. If you had a single 10 cab, you'd be justified in worrying.

    For instance, I run a pair of 2x10 cabs full range, and my low B is solid as can be. Better than when I used to run an 18 with a 4x10 on top. Cab tuning is the key.

    So my theory is if you want to avoid blowing drivers with your low B, use the 4x10 to supplement the 15, running them all full range. The more cone area you have reproducing the low B, the less cone excursion you need to do it. The 2 cabs can help each other, reducing the risk of blowing either one trying to handle the low end all by itself.

  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Like I said before.
  14. I understand where you're coming from.. It's still considered "biamping", but most biamp setups involve crossovers and running different frequencies to different cabs.

    If I were to run those two cabs, I'd do pretty much what you are considering. With the EQs on the individual amp channels, you could boost/cut frequencies that would help each cab sound best. Take deeper lows out of the 10s, maybe run more highs/mids through them. But most importantly, you would have control over each amp's output, so you could turn a louder cab down a bit, or vice-versa. Trying to run two different cabs from one single amp is usually hit or miss. If one is too loud, or if they just don't sound well together, there isn't much one can do about it.
    Running the amp your way would also leave you with more options for connecting cabs with different ohm loads too. You could run an 8 ohm off one channel, a 4 ohm off the other, and not have to worry about total ohm load on a single amp.

  15. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Seems to me that a pair of 10s has about the same cone area as a 15. Personally, I haven't calculated it, but I do recall seeing a table in loudspeaker design book that I have from way back...