2 power amp choices for tonight.. which way to go?

NickfromSOS · #1 05-27-2011, 10:56 AM

I have a BBE Bmax pre and a Markbass Traveler 15 cab (400 watts at 8ohms). I've seen lots of posts here about having headroom in your amp -vs- trying to match power output with the cab. For tonight's gig, I could use either a QSC GX3 (350 watts at 8ohms - i'm only running one side) or an AB Precedent 600A running 700 watts at 8ohms bridged. Which way would you go? If i get to the gig and the GX3 is not enough power, you can't bridge them so I'm stuck.

By the way, I'm playing a big club with PA and sound engineer. The amp is just for stage monitoring.

Plstrns · #2 05-27-2011, 11:05 AM

The GX3 will have some headroom with that single 15.

RickenBoogie · #3 05-27-2011, 11:39 AM

+1 your limitation will be the single 15, NOT the wattage.

Dragonback07 · #4 05-27-2011, 12:58 PM

I would go with the better sounding preamp and use what you need to get you by on stage with your band. The FOH will give you the massive wattage you want but I image my sound for on stage and send it to the mixer. If there isn't a FOH then go with the bigger wattage amp but save that cash and get another cabinet to move more air as RickenBoogie mentioned. A single 15 will only get you so far in a small venue, but you obviously know that when you get in the bigger clubs or such that more speakers equal more air movement and volume/wattage.
I always go by this motto: don't sacrifice sound quality for volume. A crappy sound will get you nowhere. A tight great sounding bass will get you rave reviews from the crowd....that is if you play the bass well

NickfromSOS · #5 05-27-2011, 01:34 PM

The Bmax sounds great... i love my preamp. I will eventually pick up a 2nd cab to add on... thanks for the info

chucko58 · #6 05-27-2011, 03:17 PM

700 W is only 3 dB more than 350 W. As others have already said, the single 15" will be the limiting factor more than the power.

BassmanPaul · #7 05-27-2011, 04:57 PM

Not only that but with the AB amps 700W you'll have double the power available that the cabinet can take. Remember that the rating of a cab is the point where the voice coils start to melt.

lo-freq · #8 05-27-2011, 05:56 PM

Quote:

Originally Posted by BassmanPaul

... Remember that the rating of a cab is the point where the voice cails start to melt.

Depends on a lot of things...not a given as stated, IMO.

BassmanPaul · #9 05-28-2011, 10:31 AM

Quote:

Originally Posted by lo-freq

Depends on a lot of things...not a given as stated, IMO.

Fine - whatever!

Zooberwerx · #10 05-28-2011, 10:49 AM

700 watts would make more sense if you were powering a big ol' mambo 4 X 10 (or larger) enclosure but, in the meantime, the GX3 will be more than sufficient. Enjoy the gig!

Riis

BassmanPaul · #11 05-28-2011, 11:17 AM

Quote:

Originally Posted by lo-freq

Depends on a lot of things...not a given as stated, IMO.

Power ratings listed on cabinets are almost always the thermal limits. That's the point where the voice coils start to melt as I posted. A typical driver will start to exceed its mechanical limits at around half its thermal rating. So for a thermal 350W, usable power will be in the range of 175W. Inputting more power will not make the cone move any more than that and will damage the driver. When it comes to our instrument more drivers have a greater effect on volume than more power.

RickenBoogie · #12 05-28-2011, 03:05 PM

Quote:

Originally Posted by lo-freq

Depends on a lot of things...not a given as stated, IMO.

No, it's true. Most ALL bass cabs have an RMS wattage rating that is measured to the point the voice coil will melt. And it's also true, most bass cabs are absolutely limited to about HALF their rating for useable volume. There ARE many "other" factors, but this point is well established.

lo-freq · #13 05-28-2011, 03:43 PM

Quote:

Originally Posted by BassmanPaul

Power ratings listed on cabinets are almost always the thermal limits. That's the point where the voice coils start to melt as I posted. A typical driver will start to exceed its mechanical limits at around half its thermal rating. So for a thermal 350W, usable power will be in the range of 175W. Inputting more power will not make the cone move any more than that and will damage the driver. When it comes to our instrument more drivers have a greater effect on volume than more power.

Quote:

Originally Posted by RickenBoogie

No, it's true. Most ALL bass cabs have an RMS wattage rating that is measured to the point the voice coil will melt. And it's also true, most bass cabs are absolutely limited to about HALF their rating for useable volume. There ARE many "other" factors, but this point is well established.

So what frequency (or frequencies) are we talking here?
If this is a standard rating industry-wide there should be specifics as to frequencies and time till meltdown, right?

An RMS rating for amplifiers is based on how it operates safely within given parameters (distortion levels, not going into thermal-shutdown, etc.) -- I would think driver manufacturers would rate them for a certain 'safe' level not a 'meltdown' level -- true or not true, that just makes no sense to me.

NickfromSOS · #14 05-29-2011, 08:25 AM

Just a follow up on this I played the gig, which was on a fairly big stage with two guitarists, with the qsc gx3 and through the pa. I never turned the amp past 12 o'clock the whole night and it was punchy and crisp. Sounded great. Think I'll stay with the gx3 in e rack for now

steveksux · #15 05-29-2011, 08:30 AM

The RMS rating is generally the thermal limit, but its for long term avg continuous power. Playing music, there's rests between notes, between songs. Some loud, some soft.

People routinely run power amps twice the RMS rating of the cab for years without incident. That's typically the recommended power rating to use, somewhere between 1.5 and 2x the RMS rating of the cabinet.

The 700 watt amp will give you maximum flexibility and headroom. You can always turn it down and use less power.

Randy