Members deepblue Posted February 17, 2008 Members Share Posted February 17, 2008 Here is a quote from a company selling gear on Ebay. My friend passed on a package deal because it would have meant bridging the two amps offered for each dual 18 enclosure (JBL MRX 528s/pair and 2 crown xti 2000) "Bridging amps allows you to extract the maximum performance out of your amps with the least amount of cost. The XTi series are capable of bridging with no ill effects on performance or long term reliability and it is a very simple process that is no more complicated than connecting a standard amp in stereo. The instructions in the manual are straight forward and there is a picture diagram on the back of the amp on how to connect the cables." I know it's advised to discourage bridging of amps for those who are new to running sound, so I was wondering what you guys thought of this reply from the salesman. I'll link my friend to this post so he can see responses. Thanks! Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 17, 2008 Members Share Posted February 17, 2008 It's a little more power than I would recommend for a beginner on an amp with confusing DSP, I would suggest that a (pair of) QSC RMX1450 in bridge mode with the limiters set on, and the HPF's set to 30Hz. This would be pretty bulletproof. The 1850 would be another option, though boarderline possibly too much. The other option is to get a single stereo amp of the proper size, something like the PLX-3602 which IMO is ideal in terms of power, size, weight, simplicity and reliability. It would also cost less than 2 of the Crown units and carries a 6 year warranty. I also have a few almost new amps that would be suitable for stereo operation of those subs, but they are pretty big and heavy. They would be way cheaper than either of the options I mentioned. PM me if interested. Link to comment Share on other sites More sharing options...
Members kevinnem Posted February 17, 2008 Members Share Posted February 17, 2008 Here is a quote from a company selling gear on Ebay. My friend passed on a package deal because it would have meant bridging the two amps offered for each dual 18 enclosure (JBL MRX 528s/pair and 2 crown xti 2000)"Bridging amps allows you to extract the maximum performance out of your amps with the least amount of cost. The XTi series are capable of bridging with no ill effects on performance or long term reliability and it is a very simple process that is no more complicated than connecting a standard amp in stereo. The instructions in the manual are straight forward and there is a picture diagram on the back of the amp on how to connect the cables."I know it's advised to discourage bridging of amps for those who are new to running sound, so I was wondering what you guys thought of this reply from the salesman. I'll link my friend to this post so he can see responses. Thanks! Although it is true that a bridged amp is more suseptable to problems. It is my opinion that other problems withing the system are far more like to cost money then this. I think one of the biggest concerns is that bridged amps provide too much power and blow up speakers. Anther concern is that the failure mode of the amp is more costly when it is bridged then in stereo modes. Having said that, I believe the statements made are correct. Notwithstanding the details, you do get the most out put from an amp in bridged mode (say at 4 ohms). HOWEVER you also get the same "most output" at stereo 2ohm. I don't believe I am exposing my system to undue risk running in bridge modes. (about 1/3 of my amps are run this way...) in this case mabe a XTi4000 in stereo is better choise then 2 XTi 2000? ... I think it would be cheaper too? Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 17, 2008 Members Share Posted February 17, 2008 Here is a quote from a company selling gear on Ebay."Bridging amps allows you to extract the maximum performance out of your amps with the least amount of cost. The XTi series are capable of bridging with no ill effects on performance or long term reliability and it is a very simple process that is no more complicated than connecting a standard amp in stereo. The instructions in the manual are straight forward and there is a picture diagram on the back of the amp on how to connect the cables."I know it's advised to discourage bridging of amps for those who are new to running sound, so I was wondering what you guys thought of this reply from the salesman. Here's a problem with an unqualified statement like the above: Based on that statement I could see how a typical user could interpret that information in the following manner: 1) Running amps (all amps) in bridge/mono is the best bang for the buck.2) There is no down side to it.3) The process is simple, just flip the switch4) If the system isn't loud enough running in stereo (which most portable systems at some point or another will not be loud enough), just flip the switch and run it in bridge/mono5) Actually, why wait until the time when the system isn't loud enough... much like the "turbo" button on the old IBM XT clones... why wait until it's noticeable that the computer is running slower than you'd like? Just leave that turbo button engaged all the time.6) In-fact, why do "they" even make stereo amps? If running an amp in bridge/mono is the most bang for the buck, why not just run all amps in bridge/mono all the time? Well... that's all well and fine, except: A common scenario is: 2ea. 4 ohm subs on an arguably under powered amp running stereo... all is fine except it's not loud enough. Ok, "I'm smarter than the average bear, I'll just hook-er up bridge/mono and wow the crowd with my prowess. Ok... hook one of the speakers to the bridge/mono output on the amp, flip the switch, hook the other speaker to the "parallel" connection on the first speaker... simple enough. Wow! That's lots louder with the CD playing." So, you play the next set and at the end of the set you then notice the "PROTECT" light is illuminated on the faceplate of the sub amp... and somebody in the crowd sez "dude, what happened to that kick-assed thump you had going??? It just went away on that double pedal speed kick-drum solo you had going." You change the fuse in the amp to a bigger fuse thinking the burnt fuse was just a little too weak... and that seems to work for... oh... about a millisecond... and then the amp lets out some smoke... which smells the same as the smoke you thought you were smelling a little earlier on in the set... during your blazing kick-drum solo... and you thought it was just something going on in one of the bathrooms, but you realize now that it was your amp making that smell. So, you parallel your subs to one side of your mid-high amp, and parallel your mid-highs to the other side of your mid-high amp to get through the night. The subs seem to be making a little noise, but there's just no real thump... but you plow through to get through the night. Shortly there-after your vocals seem to be weak, but you figure you're running 4 speakers on one amp so you bump up the output on the mixer some more... and then the vocals just go away... and there's that funny smoke smell again. Investigation shows the problem with the missing vocals is that the mid-high amp now also has it's "protect" light illuminated too! You turn your monitors around to the crowd and finish the show. A little post-show investigation shows that both amps are fried, and both subs are fried... but that's ok (you're thinking)... all this stuff is still on warranty... which escalates into another learning opportunity when Monday morning it's explained to you what the warranty covers, and what it doesn't... and burnt voicecoils in the speakers and melted-down final output stages of the amp are not covered under the warranty. $1,500 and 3 weeks later, you're back to where you were before you put your sub amp in bridge/mono mode... except for the hole you punched in the surround of one of your replacement sub speakers with a phillips screwdriver when you were installing it... and except for the egg that's still stuck to your face when you fell down on the job at that last gig and you're thinking it's gonna be a long time till you have another performance opportunity in that venue. So what went wrong? Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 17, 2008 Members Share Posted February 17, 2008 Notwithstanding the details, WHAT DETAILS??? I didn't see much in the way of details with the salesman blanket statement. In-fact, based on the salesman recommendation it all seems so simple... just run the amp (all amps) in bridge/mono and be done with it (other than possibly "the instructions"). Instructions? We don't need no stinking instructions. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted February 17, 2008 CMS Author Share Posted February 17, 2008 WHAT DETAILS??? I didn't see much in the way of details with the salesman blanket statement. In-fact, based on the salesman recommendation it all seems so simple... just run the amp (all amps) in bridge/mono and be done with it (other than possibly "the instructions"). Instructions? We don't need no stinking instructions. Simple misunderstanding. "Notwithstanding the details" sets the condition in *that* sentence, not any other statements in the post. In this case it just relates to the limitations of bridging....impedance minimums, possible reduced protection, etc. I'm not making that any clearer.... Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 17, 2008 Members Share Posted February 17, 2008 I'm not making that any clearer.... 4 plus 4 is 8 right? No? It's 2? But 2 is less than 4, right so that should be less, not more, right? And running in bridge/mono means it's like only one speaker output, so 2 ohms out of one output is easier on the amp than two 4 ohm outputs... right? And besides, the knobs on the front aren't past 3 so that should be ok, right? Or will having the knobs only on 3 starve the speakers for power and blow them up? Link to comment Share on other sites More sharing options...
Members lifeloverwg Posted February 17, 2008 Members Share Posted February 17, 2008 4 plus 4 is 8 right? No? It's 2? But 2 is less than 4, right so that should be less, not more, right? And running in bridge/mono means it's like only one speaker output, so 2 ohms out of one output is easier on the amp than two 4 ohm outputs... right? And besides, the knobs on the front aren't past 3 so that should be ok, right? Or will having the knobs only on 3 starve the speakers for power and blow them up? The best cure for stupid behavior is to have it cost people money. If you can't bridge an amp you shouldn't have a drivers liscense, operate a PA or be allowed to procreate...... I don't have to deal with warranty service though. Winston Link to comment Share on other sites More sharing options...
Members kevinnem Posted February 18, 2008 Members Share Posted February 18, 2008 WHAT DETAILS??? I didn't see much in the way of details with the salesman blanket statement. In-fact, based on the salesman recommendation it all seems so simple... just run the amp (all amps) in bridge/mono and be done with it (other than possibly "the instructions"). Instructions? We don't need no stinking instructions. What I was trying to communicate is that the statment " you do get the most out put from an amp in bridged mode (say at 4 ohms)." Is for the most part a correct concept, however there may be situations where this is untrue. Surely if I said "you always get the most power in bridge mode", the next post would be a one case where you don't. I have already explained how, with consideration of impedance, we can get just as much power in stereo as bridged. KEv. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 18, 2008 Members Share Posted February 18, 2008 What I was trying to communicate is that the statment " you do get the most out put from an amp in bridged mode (say at 4 ohms)." Is for the most part a correct concept, however there may be situations where this is untrue. Surely if I said "you always get the most power in bridge mode", the next post would be a one case where you don't. I have already explained how, with consideration of impedance, we can get just as much power in stereo as bridged. KEv. It's ok... I believe we all understood what you were communicating. I was just egging along the topic of discussion... with a smile. (didn't mean to get your underwear all bunched up). But you've brought up another good point/detail concerning the salesman's bridge/mono advice, being: "the one case that's the exception to the rule". Not that there's anything specific I can think of that relates, but it's the exceptions to the rules which cause the most spectacular and most expensive failures in systems at a time when the operator is most relying on it to function... aka: Murphy. The salesman's blanket statement concerning bridge/mono operation blows off Mr. Murphy way too much for my comfort level. Link to comment Share on other sites More sharing options...
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