Cab/amp matching

Discussion in 'Amps, Mics & Pickups [DB]' started by Champagne, Jan 26, 2013.


  1. Champagne

    Champagne

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    Hello Everyone,

    I have always lived by the notion of matching amp/cab capacities. I don't know why, but that is how I have been.

    The cabinets I am getting are 350 watt. A 3-way cab 12/6.5/horn and a 1x12. The 12s re PRV 12W700s

    I am considering a GK MB200 to drive them.

    Do you think this will be all right? Are there others that I should consider?

    There is an article here on micro heads on a budget and I am leaning to the gk due to budget reasons. Here is the article:
    http://www.premierguitar.com/Magazi...cro_Bass_Amp_Heads_for_Any_Budget.aspx?Page=2

    I will be playing mainly DB on this rig, but the rig will also be used in the studio for artists with crappy bass amps, so I need a little capacity for doubling as a slab amp too. I do have a couple of 2ru power amps sitting around, but I am really looking to be compact on it. The one I have is 300 watts, so I could just get a preamp but I think I will be losing the capacity for doubling.

    So, what do you think? The mb200 driving a 350W set of cabs rated for 350W? Any other suggestions would be greatly appreciated.

    Thanks a lot.
     
  2. Matt Ides

    Matt Ides

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    I might be mistaken but the mb200 only has 1 speaker out and is rate at 250 watts at 4 ohms. It is underpowered for you cabs, but would work if you only want to use a single cab.
     
  3. Champagne

    Champagne

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    Yeah, it does have only one output jack, but I can jump cab to cab to drop to 4Ω to hit 200W output.
     
  4. Greg Clinkingbeard

    Greg Clinkingbeard

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    It's rated at 200W at 4 and it sounds like less. Although it's a nice sounding amp I don't like it when driven hard at 4 ohms.
     
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  6. Champagne

    Champagne

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    Thanks Greg. That's what I wanted to hear. I guess I have to look for other options. I was wishing the mb200 would fit the bill. Suggestions?
     
  7. Greg Clinkingbeard

    Greg Clinkingbeard

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    There are quite a few options and I suppose they all have their place. For me, I bought a used Clarus and love it. My series II may be under powered for your application but a series III or IV would probably work well. However, the series II sounds much bigger than the MB200 and drives 2 ohms if you ever need it. It's also heavy by today's standards at 5lbs but sounds great and the AI service is legendary. Rick takes care of his customers better than anybody in the business.
     
  8. Champagne

    Champagne

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    Allright, it looks like back to the drawing board for me. Hmmmm....

    When you folks search for bass heads in the forum, what quires do you use? I come up with so many darn hits. I do confine the search region to the DB amp section.
     
  9. Freddels

    Freddels Musical Anarchist Supporting Member

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    If you like the tone of the MB200, then maybe look at the 500.
     
  10. Champagne

    Champagne

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    I haven't tried the mb200. I just picked up a used Genz Benz Shuttle 6.0. I will give that a whirl and see how it works out.
     
  11. GrowlerBox

    GrowlerBox

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    That was short work! Well-regarded DB amp.

    Returning to your opening post, I agree with "matching" amplifiers and cabinets with respect to their tonal characteristics and intended use, but trying to match them in terms of their power output and thermal limits respectively is futile at best and provides a false sense of security and potential for speaker damage at worst. Pretty much the only generally available numbers worth taking seriously are the total nominal impedance of your cabinetry and the minimum allowable for the safe operation of your amplifier.

    Someone earlier alluded to the myth of cabinet "underpowering"; suffice it to say that overpowering is how speakers are damaged, and that sufficient power can be delivered by heavy attacks on low notes by even quite low-powered amps to damage even high-specced speakers (this has nothing to do with amplifier clipping and square waves or DC current or whatever the latest story entails).

    That said, many of the current crop of 3-way cabinets are designed to soak up gobs of power and spit it out clean -- this may apply to your speakers. Others (like my BFM horn-loaded cabinet) are designed, in part, for efficient use of power and can squeeze the last drops out of small amps like the MB200.

    Sorry for the long interjection -- enjoy your new amp! :D
     
  12. Champagne

    Champagne

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    I cant believe you have a Jack! I was looking so close at those kits and even priced one up. What I couldn't wrap my head around was the piezos for the thing. The thing that pushed me to the cabs I got were price. The 2 cabs I bought ran the same as what I would have built a Jack for and for me being a studio owner, I know artists could use them because the amount of poor bass rigs that come in are shocking. I am jealous you have a Jack. I really wanted one! :)
     
  13. GrowlerBox

    GrowlerBox

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    Thanks, I do like my Jack. The piezos are great if you plan to use the cab for anything but bass, but I leave mine switched out 95% of the time. It's a fantastic guitar cab or mini-PA with them switched in. There are mixed feelings about them for DB use, and I haven't had the opportunity to try a greenboy or Arnopol design, but it's streets ahead of any "standard" direct radiator cab I've tried. :)
     
  14. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC Supporting Member

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    If we're talking about multi-way systems, i.e., those with tweeters (including horn-loaded compression drivers), then many, many more drivers are damaged by underpowering as compared to overpowering. Clipping an amp by overdriving it will fry a high-frequency driver quickly, whereas overpowering a woofer usually is preceded by some "complaining" from the driver.

    Overpowering can be avoided by use of in-line breakers or fuses but, admittedly, you really have to do the calculations carefully to avoid premature interruption while maintaining protection. For that reason, it's not that common a practice.
     
  15. GrowlerBox

    GrowlerBox

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    I know what you mean, but would that not still represent overpowering the tweeter? By my way of understanding it, that's not too little power for the speakers, it's too little power for the job if you're having to clip the preamp to get enough out of a maxed-out amplifier. And I also think that you're not going to be protected from that by buying speakers with a published thermal rating to match your amp's supposed RMS output.

    You gotta remember it's harsh out there, people. Need to keep up your guard :D.

    Edit: By the way, what time is it over there, Les? It's a school night, isn't it? :)
     
  16. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC Supporting Member

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    Well, yes, but the problem is produced by using an amplifier that is underpowered for the job. So, when talking about mating an amp to a cab, the problem is caused by too little, rather than by too much power.

    Exactly. There's really no such thing, in terms of danger, as too little power for the speakers. For decades, the frying of tweeters as a result of clipping has, appropriately, been referred to as damage resulting from the choice of an underpowered amp (for the job).

    Thermal rating? I'd never choose a system based on that so, as usual, it seems we agree there as well. Likewise, you can get in trouble by choosing a cab based on its power-handling rating. (Maybe that's what you called its thermal rating.) Those ratings are fine for determining the power that can be dissipated over some narrow band of mid-band or, perhaps, even broadband frequencies. Left out of that is the excursion limits of the driver. So, everything can seem to line up properly and then you hit a low E and the cone goes "splatttt." For constant power, the excursion of a driver is inversely proportional to the square of frequency (IIRC).

    Well, Shane, we agree again. :)

    It was 8:55 PM when I posted. I'm allowed to stay up even later. :)
     
  17. Greg Clinkingbeard

    Greg Clinkingbeard

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  18. GrowlerBox

    GrowlerBox

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    Well that's a relief! ;) I'd always defer to you on this stuff, Les; I argue merely in an attempt to increase my understanding. On that note, it would seem possible in principle to protect tweeters from these large voltage swings (assuming that's what these spikes represent), by incorporatoing some sort of gate into the crossover. It's what those lightbulbs in older cabinets were for, right?

    Ah, so. My mistake. A miscalculation regarding the time difference. Way, way ahead of you here :).
     
  19. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC Supporting Member

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    Right you are! I don't recall the light bulbs but neon bulbs could be used for that as they are "non-ohmic" devices. That is, they have a very high resistance until you trigger the gas. Klipsch used to put back-to-back zener diodes across the tweeter drivers. Same deal. Zeners basically don't conduct until you hit the "knee" voltage, after which they look like dead shorts. So, in an AC circuit, when they're back-to-back, both don't conduct until you hit a high voltage. In the following, replace "LED" with "tweeter." :)

    [​IMG]
     
  20. Greg Clinkingbeard

    Greg Clinkingbeard

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  21. GrowlerBox

    GrowlerBox

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    Thank you! You da man. :)

    That's an LED, right? So replace LED with tweeter, and Zener with LED ... Ouch.
     

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