Newb question about bi amping.

[tysonh]

Sorry about such a simple question but hey.

If one has a 1200 watt amp that is bi amp able must you use both channels (bridged) or can you use one channel at say 8ohm to be able to use a big amp like a 1200 with like a 210 cab successfully ? So the other amp channel would just be static I guess ? does this harm an amp.

I am trying to get a gauge on what kind of cabs I need for a 1200 to1500 watt amp. I want to have a 210 probably at 8 ohm (for small situations and practice) and either a single 115, 118 or maybe a 410 as a second cab.

and is there any long term durability issues running an amp at 2 ohm ?

[JimmyM]

you can use only one side of an amp no problem. but i highly question the logic of using such a powerful amp to power a 210. most 210's you'll be lucky to get 200w worth of power into before it starts rebelling. big power amps are meant to power big cabs like 410's and 810's. if you are very careful with volume you can do it, but if not, it's a recipe to blow speakers.

and whether or not you will mess up the amp depends on the amp. you have to check each individual amp for its specs.

[lbwdog]

Originally Posted by JimmyM

you can use only one side of an amp no problem. but i highly question the logic of using such a powerful amp to power a 210. most 210's you'll be lucky to get 200w worth of power into before it starts rebelling. big power amps are meant to power big cabs like 410's and 810's. if you are very careful with volume you can do it, but if not, it's a recipe to blow speakers.

and whether or not you will mess up the amp depends on the amp. you have to check each individual amp for its specs.

+1
But.....It sounds like you aren't talking actual bi-amping, which is when you use two amp channels to divide and reproduce low and high frequencies.

As for bridging, very seldom is it necessary for the average player (including pros) to bridge for extreme power. I've always been a proponent of the simple solution. Forty years of playing professionally with name artists, and in the largest of venues, and I've never required that kind of power.

[mcrracer]

If you get good EFFICIENT speaker cabs you will never need that kind of power.

[Mr. Foxen]

Originally Posted by lbwdog

Forty years of playing professionally with name artists, and in the largest of venues, and I've never required that kind of power.

I that sort of situation you have a PA to give you the power. People who aren't pro playing venues not big enough to have an adequate PA are the ones that need the power.

[RickenBoogie]

Plus, imo, you seem to building a rig backwards. You've picked a rather high powered amp without really considering your needs. Define that first, then shop for a rig that will easily cover those needs. I think alot of younger players gravitate towards big, high wattage amps, thinking that they;'ll get their volume simply by wattage alone, when in fact, 300-500 watts is usually more than enough power when paired with a good, effecient speaker cab. Volume is produced with speakers, and plenty of 'em. I don't know your needs, but I would guess that 300 watts through a good 6x10 would be more than enough. Or,a pair of 2x12's, or maybe even a pair of 2x10's. I think you get the idea. and biamping is another thing altogether.

[Zooberwerx]

Yes, one side of your amp should be more than adequate to fire-up a 2 X 10 bass enclosure. That being said, a bridged power amp is more efficient in several applications. A lot depends on the components on hand. Case in point: I'm using Acme B-4 cabs (notoriously inefficient!), Carvin 1503 PA enclosures, and a handful of QSC RMX 1450 power amps which only push ~280 watts @ 8 ohm. Rule-of-thumb says a cab should see 1.5 - 2 times the RMS rating so we're falling well short in standard stereo configuration. In bridged mode, however, the amp produces 800-900 watts @ 8 ohm which is more than reasonable for both Acme and Carvin enclosures.

Riis

[lbwdog]

Originally Posted by Mr. Foxen

I that sort of situation you have a PA to give you the power. People who aren't pro playing venues not big enough to have an adequate PA are the ones that need the power.

PA power for FOH, but still have to use your rig for stage volume, and those can be some very large stages.

I can see the need for a sizable rig for playing loud, hardcore music in say, a large club, but even then, a well powered head combined with enough quality speakers will get that job done.

Like I said, the more complicated we make it, the more likely we are to have equipment issues. This is all IMHO!

[JimmyM]

Originally Posted by Zooberwerx

Rule-of-thumb says a cab should see 1.5 - 2 times the RMS rating so we're falling well short in standard stereo configuration.

that is rule of thumb for pro soundmen who know what they're doing. as we've seen in so many blown speaker threads on here, many bass players have no clue what they're doing. if you're going to do that, you have to be honest with yourself and assess your abilities to control yourself from cranking it as loud as you possibly can until your speakers blow. you also have to take into consideration that most pro level sound cabs have honest real world power handling specs while very little in the bass cab market does.

therefore i would have to say this is not a good idea for our op.

[tysonh]

Originally Posted by JimmyM

you can use only one side of an amp no problem. but i highly question the logic of using such a powerful amp to power a 210. most 210's you'll be lucky to get 200w worth of power into before it starts rebelling. big power amps are meant to power big cabs like 410's and 810's. if you are very careful with volume you can do it, but if not, it's a recipe to blow speakers.

and whether or not you will mess up the amp depends on the amp. you have to check each individual amp for its specs.

Hence, the dilemma, only more powerful amps have the bi amping option and who wouldnt want to send the mid/high to a 210 and then lows to either a 115 or 118. whats a guy to do ? I dont want to have to lug around a 410 just to use the amp.

@Rickenboogie I think I maybe have defined my needs in the original posting. 210 for a very small weekly thing and maybe practice and either 115, 118, 410 to add for gigs or a more exciting practice

[Zooberwerx]

Originally Posted by JimmyM

that is rule of thumb for pro soundmen who know what they're doing. as we've seen in so many blown speaker threads on here, many bass players have no clue what they're doing. if you're going to do that, you have to be honest with yourself and assess your abilities to control yourself from cranking it as loud as you possibly can until your speakers blow. you also have to take into consideration that most pro level sound cabs have honest real world power handling specs while very little in the bass cab market does.

therefore i would have to say this is not a good idea for our op.

+1 on all counts. Stuff like this is not for the faint-of-heart or those unwilling to do the necessary reading / research. I certainly would not recommend a bridged mono config for his given application. However, I'm hoping the OP recognizes his options should he choose to upgrade / add enclosures in the future.

Riis

[JimmyM]

Originally Posted by tysonh

Hence, the dilemma, only more powerful amps have the bi amping option and who wouldnt want to send the mid/high to a 210 and then lows to either a 115 or 118. whats a guy to do ? I dont want to have to lug around a 410 just to use the amp.

i personally wouldn't want to biamp. i don't see the need for it, especially now that manufacturers are coming out with 2 and 3 way cabs built for bass using speakers that are way more suited to bass playing than your basic pa tops. besides, if you do it, you will need two separate amps with separate eq controls, and most twin-amp bass amps don't have that. you could use a power amp with two separate preamps but you'll need an electronic crossover to separate the frequency bands or you'll end up with a hole in your mids right where most of us need them.

i would do a lot more reading up on biamping if i were you if you want to do it right.

[Jaco who?]

Originally Posted by tysonh

Hence, the dilemma, only more powerful amps have the bi amping option and who wouldnt want to send the mid/high to a 210 and then lows to either a 115 or 118. whats a guy to do ? I dont want to have to lug around a 410 just to use the amp.

@Rickenboogie I think I maybe have defined my needs in the original posting. 210 for a very small weekly thing and maybe practice and either 115, 118, 410 to add for gigs or a more exciting practice

Most if not all modern 2x10 cabs are intended to be used full range, and many, like the Acmes, will produce low frequencys as well or better than a 115 or 118. Bi - amping to a cab intended to be used full range is pointless.

Also, most 1200-1600 watt PA power amps are rated that way at 2Ωs or 4Ωs. An 8Ω load from each side (NOT bridged) would probably be perfectly safe for a pair of 2x10s, or any other easier to schlep combination you may be thinking about.

[Zooberwerx]

I kinda figured this would transition into a full-range vs. bi-amp discussion but that's okay. If you like the tone of your full-range 2 X 10 cab, consider adding a second when increased volume levels are required.

BTW, what amp and enclosures are we talking about?

Riis

[billfitzmaurice]

Originally Posted by Zooberwerx

Rule-of-thumb says a cab should see 1.5 - 2 times the RMS rating

That rule came from the old days of hi-fi and early PA when it was crucial to keep the signal clean lest tweeters be toasted. It never had any validity with musical instrument amps and cabs.

i would do a lot more reading up on biamping if i were you if you want to do it right.

+100. And it's very much something you want to do either right or not at all.

[Zooberwerx]

Originally Posted by billfitzmaurice

That rule came from the old days of hi-fi and early PA when it was crucial to keep the signal clean lest tweeters be toasted. It never had any validity with musical instrument amps and cabs.

I still see it being touted as a "standard" with regards with today's PA gear but, if is this indeed misleading, what guidelines do apply? For an example, let's use a mid-grade full range 3-way PA enclosure rated @ 400 watts RMS / 8 ohm. Conventional wisdom holds that 600-800 watts is optimal in this situation which, as you have pointed out, may not be a valid claim.

Riis

[billfitzmaurice]

Originally Posted by Zooberwerx

I still see it being touted as a "standard" with regards with today's PA gear but, if is this indeed misleading, what guidelines do apply?

Most operators will run 2:1 on the high frequency amps, because the power requirements for the high end is so low that it doesn't take a lot of power to do so. But clipping of power amps simply doesn't exist in the pro-touring genre as they brick wall limit so that can't happen, and with the price of full function DSP so low now that ability is well within the reach of all but the most rudimentary systems.

[Zooberwerx]

Originally Posted by billfitzmaurice

Most operators will run 2:1 on the high frequency amps, because the power requirements for the high end is so low that it doesn't take a lot of power to do so. But clipping of power amps simply doesn't exist in the pro-touring genre as they brick wall limit so that can't happen, and with the price of full function DSP so low now that ability is well within the reach of all but the most rudimentary systems.

Thank you...I almost understand.

*What do you mean by "2:1"?

*By "high freq amps", are we talking covering the 100 hz - 20 khz range?

This is helpful as I may be able to re-allocate wasted power.

Riis

[billfitzmaurice]

Originally Posted by Zooberwerx

Thank you...I almost understand.

*What do you mean by "2:1"?

Amp power to driver rating.

*By "high freq amps", are we talking covering the 100 hz - 20 khz range?

In PA usually 1.5kHz and up. Less than 20% of the total system power lies in that range.

[tysonh]

I was looking at either the Carvin BX1200 or the new 1500. and a 210 that is 4ohm @400w and LATER a 115, 118, or 410.