Are amps rated in RMS or Peak power (Genz Benz specifically)?

Discussion in 'Amps and Cabs [BG]' started by johndough247, May 19, 2012.

  1. Maybe this is common sense and I'm lacking some at this moment, but I've always done the combo amp thing so the separate amp/cab setup is new to me. I've read several of the amp stickies that discuss over and underpowering, watts and impedance, never saw this specific question discussed before (again, maybe I'm a little slow and it's obvious).

    Question: When an Amp (not the cab) is rated at 900W, does that mean RMS or peak power?

    Reason being, I'm interested in getting a Genz Benz ShuttleMax 9.2 coupled with 2 x Aguilar SL112 Cabs:

    ShuttleMax 9.2 = 500W @ 8 Ohms, 900W @ 4 Ohms
    Aguilar SL112 = 250W RMS/500W Peak

    I'm gonna start with just one SL112 for now, so that means 500W (again, don't know if that means RMS or Peak) into a 250W RMS/500W Peak Cab.

    Of course, I won't push an amp to full immediately with reckless abandon...but in my mind, it seems if an amp's power rating is peak (which makes sense from a marketing perspective...higher numbers) then this setup should be fine, right? I technically would hit the limit of the cab only if I'm pushing the amp to maximum and clipping constantly?

    If it's the other way and amps are rated and marketed as RMS (like most cabs are), then I'd be asking for trouble with this setup I'm guessing...just trying to figure out if this is safe. Thanks for any help you guys could provide.
  2. usually amp power is RMS rating. I am hoping that Agedhorse from GB chimes in to confirm. Perhaps edit your post title (advanced edit) and put GB in the title.
    "Genz Benz Newb Question"?
  3. Nobody else?
  4. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    You could a 1,000 watt amp and a 100 watt cabinet.
    So long as the volume control was not turned up beyond the speakers capability you will be fine. I was using a 1500 watt amp last night with a single 15 cab; using your ears to be on the look out for speaker farts or cone distortion is the key.

    There are a few exceptions to this rule when using a hron or tweeter loaded cab in that you could take out the high end driver before the woofer and not hear it.
    I don't believe this to be a problem with the Aguilar cabinets you mentioned.
  5. Oh ok cool, I figured as much with the volume thing, but still...are amps rated in RMS or peak? (maybe I should change the title to get more people to weigh in on the answer)
  6. gillento


    Oct 15, 2005
    Luxembourg, Europe
    Nordstrand pickups
    I briefly played the SM9.2/SL112 combination.
    That will sound extremely articulate...... I prefer the sound and thump of the Streamliner or an Ashdown ABM with these cabs.
  7. The specs will say RMS if it is. If they don't say RMS then it can be anything the manufacturer says. Some power amp makers have lowered themselves to quoting "peak burst" power in the advertising.

    Genz should be more reliable but look up the spec sheet to be sure.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    The amps are rated at "RMS power", which is technically the RMS voltage squared divided by the nominal load impedance. I believe this is covered in the owner's manuals under the specifications and/or 3DPM description.

    Incidentally, this is why I sometimes caution folks about using some of our amps with smaller speakers, it's easy to assume that there is less power available than there actually is and I would hate so see a speaker damaged from delivering too much power.

    Hope this helps and clarifies.
  9. StraightSix


    Nov 23, 2011
  10. Thanks for all the responses so far, and if you have any other lightweight amp suggestions to pair with this cab let me know (to get a sense of the max amount of power you think you could get away with this rig).

    I did try the shuttle max 12 a few months ago with GB speakers not sure which...I do remember the lows being tight, not really warm but very present. Some say the 9.2 sounds warmer than the former shuttle models which is what im hoping for...but yes, I do remember it being very articulate. Do you remember if you used the tube channel?

    As much as I love warm sounding rigs, I prefer versatility in EQ options, plus my main bass is plenty warm as well.

    Couldnt find that earlier today either...
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Looks like the proper reference is missing. Rest assured we use RMS measurements, otherwise if we used peak measurements it might be called a ShuttleMax 18.2 as the amp delivers ~1800 watts peak as it sits right now.

    I will look into adding RMS to the documentation. Thanks for pointing this out.
  12. gillento


    Oct 15, 2005
    Luxembourg, Europe
    Nordstrand pickups
    Yep, the sound I liked most (fattest) was a blend of both channels.
    I don't want to discourage you at all. But me too, I like having a more articulate amp besides my more tube sounding SA200 and STL600. But for my taste, it was too "articulate". I like MB heads better for this purpose (even back when I played mostly Sadowskys, like you do)
  13. Tuned


    Dec 6, 2007
    Amps are rated RMS. Solid state amps can peak a little bit higher, but speakers can peak twice as high. Class D amps can do square wave output at their rated RMS output, so if you're an idiot and blast distorted noise trying to be louder, a 250W class D amp will fry a 500W RMS speaker. Use your ears. To be safe I like at least 30% more speaker handling than solid state amps, but I like at least twice the RMS speaker handling of tube amps, because they don't let you know they're punishing your speakers as obviously, and they sound best when cranked. This is why SVT tube heads are 300W and the 8x10 cabs are 800W.
  14. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Square wave?


    First I ever heard that.
  15. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    You don't have to have an exact match of the rated power of the amp and the speaker cabinet. I like to have a little more available from the amp than the cabinet rating. EAW recommends 1.5 to 2 times the cabinet rating for amp power. My last small gig I used my GK MB800 with an AE210 cab. The MB800 is rated at 500 watts into 8 ohms, and the cab is rated at 400 watts. Perfect. Interestingly, for you underpowering phobiacs, I used my MB200 (140 watts at 8 ohms) into the same cab at my previous gig (coffee shop) and it sounded great. The key is just don't drive the cab into distortion regardless of the power you have available.
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Whoa here... lots of mixed up and conflicting information.

    For factual sake, here's a little bit of information that's accurate AND what it really means:

    1. Amps CAN be rated in a variety of ways, but "RMS power" is probably the most common in the pro market and is based on the RMS voltage into the rated load. In actuality, there is no such thing as RMS power, it should be referred to as power based on RMS voltage and RMS current.

    2. Peak power of an amp is more commonly seen in the non-professional, entry level or beginner inexpensive equipment and is like the power in #1 above except that the voltage is based on peak (not RMS) voltage. Peak voltage is always 1.414x the RMS voltage for a sine wave, so squaring 1.414 gives you peak power = 2x the RMS rated power. This is true for all RMS to peak power conversions and it's just 2 ways to measure the same waveform.

    3. The above measurements are exactly the same for tube amps, class AB amps, and class D amps.

    4. Any amp that is delivering a true square wave is capable of delivering 2x the rated RMS power (less power supply inefficiency) because in a square wave, peak and RMS voltage are identical.

    5. It's possible to damage a speaker due to overpowering because you have either exceeded the thermal capabilities or the mechanical capabilities. As the frequency of the signal approaches the lower cutoff of the speaker, mechanical power handling of all speakers decreases... this is something to be aware of if you slap low stuff. You will want to build some headroom into your system by insuring that your DERATED power handling is adequate for the job.
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    This is fine as long at you are aware that the power handling decreases as you approach the low frequency cutoff of your cabinet. At the -10dB point, your speaker may only have 1/2 the mechanical power handling compared with it's rated power. The pro audio processing (in EAW's processors) accounts for this in their protection algorithems. This is not the case in most bass amps.
  18. Hmm what are you playing mostly these days? MB as in Mesa Boogie? Just checked out their line...looks good on paper but a little more pricey power-wise (although I'm sure the tone might justify it, who knows)

    Thanks! Glad I finally got that answer sorted out.

    Thanks Munji for the numbers...based on this I'm wondering if the 12.2 might be a better way to go...since it's essentially a 2 x 600W amp, I'm guessing it leaves room for bigger cab upgrades later on if needed for large venues:

    Buy now: 2 x Aguilar SL 112 8 ohm cabs (300W going to each 250W cab)
    Future purchase for big gigs: 1 x Aguilar GS 212 (600W @ 4 Ohms)
  19. Wow, thanks for all that info from someone actually in the field of designing these amps.

    Hmmm taking that into account, maybe an Aguilar DB 115 (400W / 8 ohms) would be a better fit as a future extension cab than the 212 (600W / 4 ohms)? It has a lower frequency range than the 212 and if my math is right, the GB Head will deliver 375W to it, but the cab can only safely handle approx. 200W in the extreme low range if I understand what you're saying correctly (and I do play 5 string basses primarily), which would mean it's within the 1.5:1 to 2:1 "safe" zone for the lower range (1.87:1) and nearly evenly matched for all other frequencies (0.94:1)?
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