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Amplifiers and Cabinets: What is going on here?

Discussion in 'Amps and Cabs [BG]' started by Soreinsun, Oct 22, 2010.

  1. Soreinsun


    Oct 22, 2010
    Okay, I'll be brief. I've been playing for... 8 years and I'm still learning about what works and doesn't work concerning amplification. I would really appreciate all thoughts concerning this new issue I'm having.

    Recently I purchased a Markbass New York 121 cabnet as a light weight alternative to accompany my Carvin BX500. (The combination sounds amazing, by the way! Dumb Luck.)

    Here's the ONLY issue. The Amp produces 300 Watts at 8 ohms. The Cab TAKES 400 watts at 8 ohms. Perfect combo right? Maybe not... I've noticed that with level eq, no drive or contour, and the compressor at 10 o'clock the combination sounds amazing and produces a hefty amount of volume (very clean). As I dial the volume to around "6" or beyond, the tweeter distorts occasionally (sounds like a chirp or a rattle; like a metal tool box in the back of a pick-up). Well the good news is I can turn off the tweeter, but I also notice that slightly higher volume levels than that and the 12 inch speaker begins to ever so slightly distort on attack (I'm assuming due to peaks).

    Here is what I know:
    1) Peaks are causing the problems from playing too hard... of course this isn't the problem as the volume reaches "10"... it's just standard.
    2) The compressor helps limit the peak volume... of course I don't want to squash my beautiful tone too much if I don't have to.
    3) Tweeters are easily distorted if the amp is clipping... and the amp might very well be clipping.
    4) Amp clipping is pretty serious if prolonged, and something I want to avoid all together.

    Here are a few questions:

    1) Is it possible that my amp is clipping with a flat eq and a bit of compression at the level of "6"? This would bum me out as the "purest" side of me would like to believe that I could turn the knob to "10" and have everything be okay (provided I'm switched to passive pick ups and no eq boost).

    2) Is there any way to measure (perhaps with an electronic gauge) how much power is being sent to the speakers? I ask this so that I might be able to measure out the tollerances and know how high I can set my levels.

    3) As power increases beyond what I consider typical (300 Watts and beyond) is distortion a normal part of pushing a speaker hard? I also have a full stack I play BX 500 through and even then the 18' speaker seems to take on a slightly distorted sound at "higher" volume. (18' speaker is rated to 600 watts)

    4) What are some things I can do to maximize my power (without adding additional speakers)? I ask this because this markbass cab was purchased to be lightweight and portable and I'd like to keep it that way.

    5) Do similarly powered amplifiers have different clipping tolerances?

    All thoughts regarding any or all of my concerns would be really appreciated. Any one who has experience with Markbass equipment is also welcome to comment if I have a bad speaker or not. I still have 20 days to return it.

    Thank in advance!
  2. The power rating of a cab means very little (just a rough guide regarding maximum power, but an amp rarely puts out its maximum power anyway, so really means nothing). It also gives you NO indication on when the drivers meet their maximum excursion and start to distort and fart.

    Unfortunately, the tweeters on some of the smaller Markbass cabs are cheap piezo models, and they tend to crap out and burn out.

    It is unfortunately that simple. LOVE the Markbass heads, the cabs with the compression tweeters are 'OK', those little piezo's are nasty business IMO.
  3. Soreinsun


    Oct 22, 2010
    Excellent feedback, thank you.

    Would you recommend a replacement tweeter that would be much more effective in the markbass cab? I love to tinker.

    Any remarks on amp clipping?
  4. I have no idea on a replacement tweeter. That's over my head. I don't think piezo's even use a crossover (my little bit of knowledge can be a dangerous thing) so that might be a major ordeal... crossover, tweeter, drilling, etc.

    Amp clipping with these solid state amps is almost a thing of the past. They all have pretty sophisticated power amp limiting. Most of the time, when people think their amp is clipping, it is either a preamp gain setting issue (simple to test... turn the gain down a bit and the master up to reach the same volume and see if it goes away), or a speaker (even at wattage lower than its 'safe maximum wattage rating) exceeding its xmax and clipping in the upper mids or just plain farting out down low.

    So, every bone in my body says your amp is fine, and even though the driver in the MB cab is a good one (B&C I think), it is just a little 112. Add another and you should be good to go for much louder volume.
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Most cabs won't take more than half their rated power before reaching mechanical limits, and few 1x12s have adequate sensitivity to run alone and give high output levels before the amp clips. Adding a second identical cab will fix both of those problems.
  6. Soreinsun


    Oct 22, 2010
    Bill, please refer to Kjung's thoughts on solid state amplifiers. The BX500 has a tube bypass for the pre-amp tube, which I believe makes it qualify for the solid state status. Do most solid states truly not clip? I've been reading about excursion as a result of amp clipping. Does this mean I have nothing to worry about concerning excursion?

    Since I don't use the preamp functions much at all, I'm going to tinker with relieving some of the low end frequencies to prevent the "farting" as Kjung so eliquently and accurately refers to it.

    I feel I should also qualify the "distortion" as a some-what ballsy, punchy, growl.

    Bill, can you speak any more on the mechanical limitations of the speaker? I'm aware of certain speakers built to have greater "throws" or whatever the actual word is. Essentially being able to push and pull a greater distance. Is there a limitation to all of these speakers?

    Thanks for your help, gentlemen
  7. pbasswil


    Feb 17, 2008
    Yeah, power specs for both amps and speakers are so subject to umpteen variables. They're usually measured at one single frequency, with all eq flat -- with a selected input signal level. When you actually play bass, the power level varies all over the map.

    For instance, merely crank the Low EQ knob one notch, and you've _hugely_ altered the amount of power you're subjecting your system to.

    IME, matching specs is never a guarantee that your speaker is safe; the ultimate final defence in matching power output to speaker is to keep your ears open -- at the first sign of farting or other unwanted distortion, backoff -- either level or low eq.

    If you're having problems getting the level you need out of your gear, what about a limiter or compressor with fast attack? If you can set one up so that it doesn't screw up your sound, you may be able to achieve a higher average volume.

    And as someone just educated me about in another thread: a lot of speaker strain can come from sub frequencies that you don't even need or want in your sound. A high pass filter set at 30 or 40hz can get rid of that garbage that yanks your woofers around unnecessarily.
  8. Soreinsun


    Oct 22, 2010
    Excellent idea about the low end. as you will observe this was a theory I was going to try, but now I am certain I can give up a little woofyness for better mids.
  9. Overexcursion doesn't necessarily have anything to do with clipping at all. It's about the speaker reaching its mechanical limits as opposed to its thermal limits.
  10. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    oh, they'll clip alright. but it's a nasty "omigodwhatsthat?" kind of clipping.

    if it's too much volume for the cab to handle, the speaker will see it basically the same, it'll just sound better.

    absolutely there is. the power handling rating is usually the wattage at which the speaker's voice coil will burn up. but the limitation of the movement of the cone tops out at a much lower wattage, as bill said, usually half the quoted power handling rating. this can also stress out the speaker, and although failure usually isn't immediate, it's forthcoming at some point.

    having owned one of those little mini cmd121p combos (same cab basically except your cab is slightly more deluxe), they do take a lot of power for a 112, but i was never able to get full clean volume out of the 300w little mark ii head without it sounding like it was about to blow up. i would put bill's estimate of taking half its rated power as about dead on.
  11. FYI, that's why solid state power amps, at least most modern day ones, have the limiting built in... the designers don't really allow them to reach that ugly clipping.

    In my experience, the vast majority of bassists who feel they've run out of power, or hear 'amp clipping' are either running the preamps too hot or pushing their speakers to the point where they are exceeding their xmax, etc.

    True power amp clipping is rarely, if ever a problem these days.
  12. FYI, I'm talking about the power section. A preamp tube is a different thing. Tube amps (large amps with those big power tubes actually generating the wattage) tend to distort in a relatively pleasing way. As JimmyM states, solid state amps, not so much, so they are electronically limited to keep them from doing that.
  13. CapnSev


    Aug 19, 2006
    Coeur d'Alene
    From what I've messed with, it seems to me that the BX500 has a ton of gain in the first 2/3 of the volume taper, meaning that the the volume on that amp increases way more dramatically from 1 to 6 than it does from 6 to 10. It's a really loud amp to begin with to.

    I would say that by cranking the amp to 6, you are giving that little cab a lot of juice, regardless of the wattage specs of either.

    It would be interesting to see how that head works with the NY121, because the 121p combo can push out 300 watts, and it needs to be at 7 or past before it starts to fart out (IME).

    (I really like that little MB combo, and the NY121 combination BTW)
  14. Lonnybass


    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    Just to throw another monkey wrench into the discussion...high pass filters designed to roll off 30 Hz to prevent over-excursion on cabinets like Acmes, which are tuned to go down to that very frequency without rolloff.

    What's the happy medium? It seems like it's a give and take.

  15. The good news is, most cabs are tuned higher than that, and most all in one bass heads have hi passing set appropriately for amplifying bass guitar through bass cabs. However, some don't. As I review and test all this stuff, it is just amazing to 'see' the different hi passing on different heads. Most heads (Markbass, Genz, Carvin, etc.) have very well thought out hi pass filters that work great with the typical cab... plenty of real bass, but not much down low to flub up the sound and trash drivers. However, then you get a few like my TecAmp Puma, some of the new little GK micros, the original EA iAmps, the old SWR heads, etc. that seem to miss the boat a little on that, and even in the higher register of the bass played softly, it looks like the drivers are about ready to jump through the grill.

    Of course, that deep bass can sound amazing if you have the perfect cab (huge excursion, big box, etc.), but mostly it just eats power and is lost in the mix.

    +1 thought... if you have an Acme and a preamp not designed for bass and a power amp without a hi pass filter control, that is what I loosely describe as a mess!
  16. Soreinsun


    Oct 22, 2010
    You guys are great. I'm already feeling much better about my most recent purchass. It seems like I bought just what I wanted and these issues that I'm having are common for every amp and cabinet out there. Thanks so much for all the advise. I'll still be checking back to see what new things come up... like this discussion on filters.
  17. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    so they can prevent the amps from going into their peak power? and that nasty clipping we've all heard on the lmii isn't dipping into the peak power but it's the pre clipping? interesting...ya learn something new every day!
  18. IMO and IME yes... user error on setting the pre gain. That will sound nasty, but that's why there is a clip light on the preamp:smug:. There is no clip light on the power amps because, well, it is limited to not reach the point where it sounds nasty. It will eventually compress. I'm not sure if you could eventually push through the limiting and make it sound nasty, but that would be extremely, extremely loud, and it is pretty obvious when the limiting really kicks in... it sounds like... well, a limiter, starting to quash to peaks when you dig in at extremely high volume.

    Not sure about 'we all'.... not many posts about clipping on the LMII that I'm aware of, although some complaints on the action of the limiter. However, that's just their design goal... keep it within their acceptable distortion spec's, and if it hits the limiter regularly, you need a bigger amp or more speakers!

    Also, remember, if you were pushing the LMII at 8ohms into only that little combo cab, speakers being pushed beyond their limits can also sound a bit like 'clipping'. Also, high quality speakers reaching their limits can also sound like power amp limiting... so IMO many people diagnosing what they hear immediately jump to power amp issues. Could be a lot of other things.
  19. Lonnybass


    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    Great answer Ken. I had a pair of Acmes that I used with an Alembic F-1x and power amp that didn't have a high pass filter. I ditched the cabinets after blowing up the drivers time and time again. My next move was to a pair of Schroeder 1210s, which I like, but sometimes find the mid-focus to be a bit overwhelming. So, I'm starting to think about the next "perfect" cabinet setup!!!

  20. With the Acme's and the Scrhoeder 1210's, you've now experienced each end of the voicing continuum:D You are like the Goldilocks thing..

    You've finished ... this cab is too wide and deep!

    You've finished... this cab is too attuenuated and mid peaky

    Now, all you have to do is find a 'just right'.. which shouldn't be that hard:)

    Edit: I like your signature!

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