Reality check on my little system for club use

[Shovelhead]

Thanks so much for all the info.

I designed and built the subs by using Eminence Designer software, and the wattage I put into the formulas was about 500 watts. There won't be any mechanical damage at 500 watts from overexcursion, and they should be pretty flat from about 45hz up to about 700hz or so. I plan on engaging the HP filter on the RMX to cut off below 50hz. Better safe than sorry, and I'm looking for more punch rather than big sub 50hz frequencies. After all, these are fairly compact subs and my expectations of them are not too unreasonable.

For the tops, I chose the 2450 because if necessary in the future, I could add another pair and still power them from the same power amp. At 750 watts for a 4-ohm load, it'd work out to about 375 per cab when using 4 cabs. At that point, I'd add another amp and another pair of 18" subs. I really don't anticipate needing that much, because the clubs we play usually seat maybe 150 people.

A more granular EQ for the monitors would be nice, but I already have a pair of 15-band EQs. Hopefully, they'll get me by until I can upgrade.

I also installed a 1/4" patchbay in the back of the rack to make setup easier, and an XLR patchbay too. They were leftovers from my studio, and will make a PITA job a bit faster.

I have experience using lots of sound systems, and don't anticipate too many problems. However, I'm nowhere near the expert as some of you guys! But I tend to err on the side of caution when it comes to volume and frequency issues in a given room.

A quick question - what frequency would you cross the subs at? 125hz or so?

Thanks again!

[guitarharv52]

I run my club 15s with a RMX1450 at 260 per side.Playing classic rock I have plenty of power to spare.

By the way Happy Thanksgiving !!

[Craig Vecchione]

 

Thanks so much for all the info. I designed and built the subs by using Eminence Designer software, and the wattage I put into the formulas was about 500 watts. There won't be any mechanical damage at 500 watts from overexcursion, and they should be pretty flat from about 45hz up to about 700hz or so. I plan on engaging the HP filter on the RMX to cut off below 50hz. Better safe than sorry, and I'm looking for more punch rather than big sub 50hz frequencies. After all, these are fairly compact subs and my expectations of them are not too unreasonable. For the tops, I chose the 2450 because if necessary in the future, I could add another pair and still power them from the same power amp. At 750 watts for a 4-ohm load, it'd work out to about 375 per cab when using 4 cabs. At that point, I'd add another amp and another pair of 18" subs. I really don't anticipate needing that much, because the clubs we play usually seat maybe 150 people. A more granular EQ for the monitors would be nice, but I already have a pair of 15-band EQs. Hopefully, they'll get me by until I can upgrade. I also installed a 1/4" patchbay in the back of the rack to make setup easier, and an XLR patchbay too. They were leftovers from my studio, and will make a PITA job a bit faster. I have experience using lots of sound systems, and don't anticipate too many problems. However, I'm nowhere near the expert as some of you guys! But I tend to err on the side of caution when it comes to volume and frequency issues in a given room. A quick question - what frequency would you cross the subs at? 125hz or so? Thanks again!

 

 

This all sounds very reasonable, and should give you a good system that'll stand up to frequent use.

 

I'd start crossing at 100 Hz with a fairly steep slope, and listen for any weirdness at the crossover point, adjusting overlap and frequency as needed.

[agedhorse]

Seems reasonable to me also.

[dravenzouk]

I run a system that is pretty similiar to the OP's. I run my mains - 2 Yami Club 115's - off of an RMX2450, one per channel. I run my subs - 2 Yami Club 118's - the same way. Understand I'm NOT posting this as "advice from an expert", just a bit of extra info from an another guy out there in the trenches.

I checked, second-checked, and rechecked with folks at Yamaha and QSC before committing to this setup and they both recommended doing it this way. I also poked around a fair bit amongst the forums (like this one) and other "soundguy's" rigs and found this to be reasonable. Yes, it's more amp than I need, but I'm careful with it and I wanted to be able to add speakers to the system in the future.

I absolutely engage the clip limiters and the 50Hz input filters on the amps. I crossover at 100hz, LR12. I watch (and listen) for clipping all the time and make sure I keep it under control. So far (cross my fingers), my system sounds pretty decent and I've had no failures or trouble.

To Shovelhead: You might be interested in checking a more detailed accounting of my rig. See page five of the "what I run, why.., and what I think...." thread for a somewhat lengthy analysis of my setup. Again, I'm NOT a PROSOUNDGUY, it's just a bit of real-world info from a similiar viewpoint as your own.

BTW, as a general rule, the advice & guidance I've gleaned from Agedhorse, Al Poulin, & CraigV on this forum has always been good and has never steered me wrong. If I ever see a semi-argument, or sharp difference of opinions such as what has popped up on this thread, I will usually accept their viewpoint as being closer to "the truth".

[tlbonehead]

Are you saying I don't need a Macrotech 3600 for my Yamaha Club monitors?

No, you'd be better off with a 5000.

[jrlaudio]

Wow,

First of all, the rating all of us are quoting as an RMS value is not. It is a value based on a test standard from IEC (IEC RS-426) - filtered noise is used with a Crest Factor of 6dB (i.e. the peaks are 4 times higher than the average level) over long test periods. An RMS test is conducted at just one frequency at a time. The AES standard for loudspeaker rating is similar to the IEC tests, but does not use the crest factor. If an RMS test was conducted the value derived would probably be closer to the so-called program power rating.

So called Program Power ratings generally is 3dB above or twice the AES rating. It tends to reflect the capacity of a speaker with music as the source.

Now let me pose this question. You have an amplifier capable of delivering a 100 watts sine wave output. Now the same amplifier has a music signal, a sine wave signal, and a square wave output. What are the difference in total power. The music would have less total power than the sine wave and the square wave would have nearly double the total power. So ... a clipping amplifier delivers more total power causing voice coils to heat more quickly. More power with therefore less clipping is always more desirable, than lower power with more clipping.

Since the loudspeaker in question is using a "noise" rating based in the IEC RS-426 standard we know the test was conducted using a Crest Factor of 6db which is how the "peak" rating of 1000w was derived. The loudspeaker rating includes the whole loudspeaker as a system including any passive crossover, it's not exclusive to the drivers. That is not to say all speakers use crossovers up to the task, of course.

I am not recommending power "4 times the RMS value" as CraigV is suggesting. On the contrary the RMS value technically is unknown simply by looking at the loudspeaker specifications shown by Yamaha. The power suggestion I made is based on the choice to have a system that will not have clipping as a regular occurance and will be safer if the system is operated reasonably (i.e. proper gain structure, limiters set properly, common sense, etc.).

I never said anything about the system being louder. I never suggested he bridge the amplifier for his subs, in fact I said the opposite. It is a common incorrect suggestion made by some that taking an amplifier connected to two loudspeakers and bridging it yields more power for the same load, which is not always the case. I also never said that more power is gonna give him more volume level. What I was saying is that clipping is the issue and running more power decreases the chance of clipping.

Also, I made it very clear that most of what I was saying was over-simplification, but you guys choose to not understand that all the math and calculations, standards or ratings, and other technical jargon we banter back and forth, may not be the best way to help a person where this info may only sound like "blah-blah-blah".

I'm a little surprised you (CraigV) say that clipping is not square waves or that an amplifier in clipping cannot be producing square-waves. You say only a synth can produce square waves. The term clipping implies in its name the peaks being "clipped" or squared-off. I suggest you take an amplifier drive it with a sine wave to clipping, with its limiters off, and sample the output on an oscilloscope. Does it still look sinusoidal? I think not. Does it look more like a square wave ... yes. Now if what you're implying is that a clipped signal isn't a perfect idealized square wave I can agree there. But to think the total power of a clipped signal or a (pure) square wave are very much different, as far as the context of this discussion, would be wrong. For this purpose they are the same and interchangeable, while not technically identical in the shape of the waveform. Maybe I should have said "nearly like" or "similar to" square waves. But for the intended reader it's really one in the same.

You make a statement, "But the average power is the issue, not the shape of the signal". Well CraigV the waveform when related to the linearity of the amplifier is directly associated to the total overall power, according to the three sentences you wrote preceding. Waveforms that are not linear analogs of the input to the amplifier are precisely the issue, especially when those waveforms are a result of non-linearity from an amplifier driven into clipping which in turn produce RMS values that are in effect the same or even higher than an unclipped higher-power amplifier running with the same input levels.

Another thing you seem to discount are the effects of power compression over time. Clipped signals from an amplifier will heat up voice coils faster than "clean" signals of the same wattage due to its higher RMS values. This is because the overall total power is higher at the same wattage output. The amplifier is not as efficient at delivering power to a hot coil and will therefore start to compensate by pushing more current around the coil. The coil heats up more and the circle of power compression begins. This translates to a drop in sound output when the speaker is operated at higher total power input, which is the case with clipped amplifier signals.

You state, "A clipped signal with X-watts peak has more average power than a sine with X-watts peak". Loudspeaker RMS ratings are derived from measurements with sine waves, so following what you say 50 watts of clipped signal has more average power than an un-clipped signal. So then you say, "A 50 watt square wave will run a 100watt speaker forever". That may be true but it will have higher distortions, have nearly as much total power as the clean hundred watt signal, and cause more power compression, therefore reducing fidelity and long-term reliability.

My point here was the first responder to the thread suggested to use smaller amplifiers then what was being used (switching from the 2450 to an 1850HD). I was saying this was bad advice and in fact I would use more, with the caveat the system be operated within reason. I drive SM15V's regularly with Crown Macro 2402 for stage monitors. This is similar power to the RMX2450. The 2402 does "clip" from time to time without limiting and an HP filter set for 95hz. With limiters no clipping, but limiting does have an effect on dynamics. I recently switched to a Macro 3600 and have not had any problems, better dynamics and clarity and I am sure less power compression. Limiters also create higher RMS values while limiting amplifier input levels.

I was gonna get into the fact that there is no RMS rating for this loudspeaker from the manufacturer, and getting into the differences between AES, IEC, Program and Peak, but I felt this type of detail might be outside the scope of the original posters needs. I was avoiding :blah:

Boy ... you guys are quick to jump on someone with a different opinion.

[Al Poulin]

It is probably fair to say we are quick at responding when we see dangerous advice given by someone. 750 watts on a Club 15 may work for someone with years of experience who knows exactly what they are doing, but for someone not so experienced, it is a disaster waiting to happen. Would you not agree that a distorted 750 watt amp will damage this speaker eve quicker than a 400 watt distorted amp? Al

[Al Poulin]

Another problem is that without some type of high pass filter - filtering out lower frequencies, the power handling capabilities of a speaker can be quickly reduced. Now throw 750 watts of 20hz-20khz response at that speaker and it probably won't take too long for that speaker to be stressed beyond its capabilities... especially in the hands of someone new to sound reinforcement. This is what we try to prevent. Al

[jrlaudio]

I agree any distorted amp is not good. The point is distorting amplifiers may not happen with a higher ....

 

Oh god ... never mind ... I tried be helpful. Sorry you guys disagree and think Shovelhead is an idiot who can't use good sense and his hearing to tell if he's driving his loudspeakers to hard, if and when he should decide to use a bigger amplifier or more boxes. Or that he is incapable of learning how to set limiting or HP filters, so instead you suggest something idiot proof.

 

I'm sorry Shovelhead, I was just trying to give you an opinion and some of the folks here took some exception to it. Which lead to a flame war over an opinion, instead of attention given where needed ... to your original post. There are many published works covering the topic of powering a system, archived here (as well as other forums on the subject of live sound) and printed works. But always remember to take the "RMS" of any advice given on a forum like this. There is never one opinion or one right way to do something.

 

I'll just close by saying, since you seem to have some experience in sound systems, the system you have should work well in most small clubs. My suggestion to you is to keep an eye on your amplifier clip lights during performances and make a decision once you observe the long term behavior of your particular power needs. It will depend of course on how you need to use your system, based on your music and its dynamics. What you have may be plenty or not. You may need to add more power/boxes or you may not.

 

For the rest of you, I'll default to the lowest common denominator and sit on the sideline like you want me to.

 

later

 

JRL

[Al Poulin]

 

I agree any distorted amp is not good. The point is distorting amplifiers may not happen with a higher .... later JRL

 

 

We certainly have different opinions, and there is nothing wrong with that. I understand the benefits of having a little extra headroom when powering speakers with bigger amplifiers, and that a bigger amplifier may not clip as easily. But if the OP does not obtain sufficient SPLs with 450 watts applied to these cabs (RMX2450), adding more power is IMO not the solution as the increase in sound will be barely noticeable and the possibility of damage will be greatly increased... More speaker AND power are required. Al

[twostone]

I agree a big amps can work just fine in the hands of a good sound tech but one stray FB and a puff of expensive smoke might appear. That's why most here tell ya to run conservative with amps and speakers. I can't tell ya how many times I run across FB issues at different rooms and a singer with terrible mic techquie, all it takes is one stray FB to fry a system. I considered a bigger amp for my NX35's programed rated at 350 watts@8ohms, I figured a 450 watt amp should leave plenty of headroom but then again there's our clumsy singer that has no mic techquie at all. He likes to put the mic down by his knees when not singing and that always causes instant FB maybe the OP has experiences but what about the rest of the band. Another problem is our guitarist like to jump around on stage which has caused the the mini boom mic stand and mic to fall over, again a bigger amp could have fried the cabs. Just from my experience I rather play it safe and be conservative you never know what can happen. Who knows some drunk might come up on stage and trip over things and mics and stands start to fall I've had it happen to me, again thank goodness I run conservative could have been a disaster which in this case it did smash the metal grill windscreen on the mic and broke the mic clip but hey that's another story gotta go.

[InACanProductions]

I agree any distorted amp is not good. The point is distorting amplifiers may not happen with a higher .... Oh god ... never mind ... I tried be helpful. Sorry you guys disagree and think Shovelhead is an idiot who can't use good sense and his hearing to tell if he's driving his loudspeakers to hard, if and when he should decide to use a bigger amplifier or more boxes. Or that he is incapable of learning how to set limiting or HP filters, so instead you suggest something idiot proof. I'm sorry Shovelhead, I was just trying to give you an opinion and some of the folks here took some exception to it. Which lead to a flame war over an opinion, instead of attention given where needed ... to your original post. There are many published works covering the topic of powering a system, archived here (as well as other forums on the subject of live sound) and printed works. But always remember to take the "RMS" of any advice given on a forum like this. There is never one opinion or one right way to do something. I'll just close by saying, since you seem to have some experience in sound systems, the system you have should work well in most small clubs. My suggestion to you is to keep an eye on your amplifier clip lights during performances and make a decision once you observe the long term behavior of your particular power needs. It will depend of course on how you need to use your system, based on your music and its dynamics. What you have may be plenty or not. You may need to add more power/boxes or you may not. For the rest of you, I'll default to the lowest common denominator and sit on the sideline like you want me to. later JRL

Isn't it you who is assuming he's an idiot? You claim it's more likely that someone would push a smaller amp to clip, and by having more available power he's less likely to clip the amp and only deliver "clean" power to the speakers. So you must be assuming that he's an idiot and would push a smaller amp to cliping rather than stay within the limits of the system or put the proper limiting and gain structure in place to be able to use a more resonably matched amp to those speakers.

You said it's less likely someone will drive an amp into clipping with more power available, but I've found most people will drive their system all the way to it's limits. Find someone who's tickling the clip lights with a smaller amp, and switch their amp out for a larger one and see if they keep the same volume or if they push that amp until they're tickling the clip lights. Think of it this way, when you're driving on the highway and the speed limit goes up do you drive faster to match that speed limit, or do you continue on at the same rate of speed because it's safer?

My suggestion of getting smaller amps was before he mentioned he already had the amps in question, if he was making a new purchase the smaller amp for his tops would be both more cost effective and what I concider a safer amount of power to those yamaha boxes. Had he been buying new, the difference in the cost of a smaller amp may have been enough to get a larger amp for the subs. Once he mentioned he already owned the amps I admitted they'd be fine with care to watch for clipping the amp.

Let's look at the SPL we're talking about, at 99dB 1w@1m the difference in SPL from 330watts with an 1850HD (just under 124dB) and 450watts (roughly 125.3dB) from a 2450 is what 1.4dB? Is that additional 120 watts gonna make that big a difference to his over all volume or available power, and is he really in any less danger of clipping the amp because of this additional available power? Let's be real. Now with a 750watt amp his max SPL is gonna be only another 3.5dB higher for a max of 127.5dB over the 1850HD, and only 2.2dB over the amp he already owns. Seems to me like splitting hairs for a minimal performance increases in a small club system for the potential damage to the speakers in case of an accident like a knocked over mic stand, or run away feedback or something.

Maybe a better suggestion would have been more effecient speakers with better power handling, but usually when I see someone putting together a system with those boxes budget is a major factor in the decision making process.

I'm all for different opinions, I'm not for seeing gear damaged. I agree those boxes could possibly be fine with the amount of power you suggested with the proper limiting, gain structure, high pass filters, and expierence of opperator. I don't discredit the OP's expierence or knowledge, but IME small bar gigs are not the environment where you can always take the time to really tweak the system for max performance, where accidents are more likely to happen, and where less than adiquate AC power might be present. Also mixing from stage does not lend well to actually hear when something's not right with the FOH system, and generally it harder to watch clip lights while performing.

[6Imzadi]

JRL,

Don't be discouraged by some of the posts you've seen here.

Welcome to the forum. Keep bringing new and innovative information. Some of the regulars here are very conservative in their advice. There is nothing wrong with being conservative as it is sometimes cheaper, but one won't learn as much.

I'm with you in your thinking. I also can understand trying to get the newbie to start out conservatively thereby keeping their equipment in good health to be able to learn more later.

my .02

[dravenzouk]

Well, I've got a little story/situation to add to this discussion that you guys are gonna love (in that roll-your-eyes, "oh, christ" sort of way). -

As I said earlier, I'm NOT a pro-sound-guy (just a regular joe working in the trenches), I DO run 2450's powering Clubs by sending one channel to each of the 115 mains and the same to the 118 subs, I AM careful to not overdo it, and it has worked fine for a while now. Also, I run this way based on direct recommendations from both Yamaha and QSC. I understand, and respect, Agedhorse's, CraigV's, and Al Poulin's views though.

Anyway, I just got back from an early put-in and soundcheck for tonight's gig. Just as I started soundcheck, guess who came back to visit? - yes, it's the return of the infamous "ribbon cable problem" on my 1604VLZ!! The entire left side of the signal is just gone - oh, boy! What to do? No problem, I just repatch cables so that I run just the left signal (I run in mono so this works just fine), with the two mains running off of one side of an amp, and the two subs the same way (basically, InaCan's suggested setup). I'm sure glad I've got amps that have plenty of juice to do this.

So you see, having amps that are perhaps just a bit too big for the job is a good thing. It covers your ass when some other rinky-dink part of your rig (like the Mackie console) {censored}s the bed. (feel free to imagine some sort of smiley icon here that indicates sarcasm and/or tongue-in-cheekness)

You know, I've been meaning to change over to MixWiz "one of these days" - perhaps I should look more seriously into actually doing this. hmmm.

[agedhorse]

First of all, the "RMS" power rating can be accomplished with a sine wave source or a pink noise source or "anything in between". The "RMS" power rating is [generally accepted] to be the thermal rating of the speaker. This must also be looked at with respect to the mechanical limitations of the speaker which varies with frequency. There are different methods that each manufacturer uses to arrive at these numbers and they are by no means an exact number.

The program rating was an attempt by the industry to develop a reasonable, or rule of thumb method of sizing an amp to a speaker and with manufacturers who were reasonable with their thermal ratings (most head to be due to the materials available back then) a speaker worked quite well powered at twice the "RMS" (or continuous) rating. Not all manufacturers used the 2x factor though, this was a function of each manufacturer's comfort level.

Things have changed with regards to thermal versus mechanical performance though, the thermal ratings have climbed a lot due to Dupont's Kapton structural insulation system, high temp polyimide insulation, coil adhesives, epoxy adhesives, and now fiberglass/epoxy bobbins. So where a speaker like the JBL D140 was good for roughly 100-150 watts RMS with a fairly short paper bobbin (or in a few models anodized aluminum was used), now with the similar geometry but using the epoxy-glass bobbin and polyimide the continuous rating is up in the 600 watt range. Mechanical ratings haven't seen the same level of improvements (though they have improved a lot) and where the original would have a 150 watt RMS, 300 watt program rating the new rating may be closer to 600/1000 AND if not high passed could be 600/600.

The manufacturers have for the most part kept the program rating as 2x the continuous rating but have in general seen a higher failure rate when powered that high (I'm talking about the LF sections here).

Then, the marketing folks got involved and with the bigger is better sales philosophy, the peak rating got a following. The problem is that in many cases the manufacturers saw the the peak power rating of a sine wave was exactly 2x the RMS value, so a 100 watt "RMS" signal is identical to a 200 watt "PEAK" signal. It's true and honest but in a misleading sort of way. So if they now say you can power with the program rating of 100 watts, that means exactly the same thing as 200 watts PEAK which is what a 100 watt RMS amplifier will deliver.

I went into a pretty detailed discussion on a previous thread about doing as the manufacturers do when powering their speakers themselves in the powered versions. In general, they stick around 1x and 1.5x the "RMS" or continuous ratings of their passive offerings. This can be modified when time sensitive limiting and time integrating thermal tracking of the load/program profile is used (the more expensive models) but it's a good look into where the manufacturers are doing as I suggest as well in spite of their advertising. They pretty much all do it this way, including the products I designed.

As far as being conservative, hell yes I'm conservative. I make my money with products that last and last and do not fail. With the sound company, we have thousands of shows ove many years without failures and I like it that way, so do the clients. When designing products for my "day job", I am also conservative since few customers look kindly upon gear that fails either. When designing installations as a consultant, I am conservative here as well. Neither myself or my client needs to deal with failures which always seem to happen at the worst possible time.

The IEC and AES speaker ratings are valid as well, but note the bandwidth limitations and power bandwidth ratios that may not reflect the real world all that well. Note also that the lifetime of the test (unless there was a revision)does not call for the speaker to meet the factory TS parameters, it must continue to make noise. IIRC, there was a suggestion that the test duration be 200 hours, but most manufacturers truncate this greatly.

A lab test is not terribly reflective on the real world. My suggestions take this into account and may be seen as conservative by some. Here's a few voice coils that have failed real world testing conditions.

[agedhorse]

So you see, having amps that are perhaps just a bit too big for the job is a good thing.

 

OR, you could just use a signal splitter into your crossover sending the single signal to both crossover inputs. Do you carry such adapters and workaround materials for such interface problems? Another solution would be to use one amp for the subs and the other for the tops and use the amp's built in parallel mono function.

 

While I think the 2450 is borderline too big for those boxes, being careful can go a long way towards preventing failures.

 

Mackie really belw it with their ribbon cable source IMO.

[dravenzouk]

OR, you could just use a signal splitter into your crossover sending the single signal to both crossover inputs. Do you carry such adapters and workaround materials for such interface problems? Another solution would be to use one amp for the subs and the other for the tops and use the amp's built in parallel mono function. While I think the 2450 is borderline too big for those boxes, being careful can go a long way towards preventing failures. Mackie really belw it with their ribbon cable source IMO.

 

 

Yeah, there are a few other workarounds as well (could have just gone from my mono output and used a different program on the DRPA, could have punched my console real hard and made it work, etc.), and yes I do carry a few types of adapters and such to rework things on the fly. It's just that this solution was the first thing to pop into my head, and being the Star Trek fan that I am, I always go with the very first idea I can think of whenever posed with a problem or threat (it works for them in the case of imminent warp failure or Borg attack, so that's good enough for me). As it happened, it worked out really well, sounds great (maybe even better than the way I had it before!), and all told it cost me less than 10 minutes to think about it, rewire it, test it, and tweak it.

 

There are, I'm sure, better ways (having better equipment is of course one of them), and I always want to hear about them and learn from the pro's who do it right. The perspective I want to put forth is that of the average working guy who's just trying to make things work as good as he can, within his (limited) means and experience - which is exactly where I'm coming from. Seems to me there are a lot of folks in similiar shoes as mine. I don't put forth my gear and methods as "the RIGHT way"; it's more of a "well, this worked ok for me" thing.

 

And yes, Mackie did blow it BIG time.

[twostone]

to be the thermal rating of the speaker. This must also be looked at with respect to the mechanical limitations of the speaker which varies with frequency. There are different methods that each manufacturer uses to arrive at these numbers and they are by no means an exact number. The program rating was an attempt by the industry to develop a reasonable, or rule of thumb method of sizing an amp to a speaker and with manufacturers who were reasonable with their thermal ratings (most head to be due to the materials available back then) a speaker worked quite well powered at twice the "RMS" (or continuous) rating. Not all manufacturers used the 2x factor though, this was a function of each manufacturer's comfort level. Things have changed with regards to thermal versus mechanical performance though, the thermal ratings have climbed a lot due to Dupont's Kapton structural insulation system, high temp polyimide insulation, coil adhesives, epoxy adhesives, and now fiberglass/epoxy bobbins. So where a speaker like the JBL D140 was good for roughly 100-150 watts RMS with a fairly short paper bobbin (or in a few models anodized aluminum was used), now with the similar geometry but using the epoxy-glass bobbin and polyimide the continuous rating is up in the 600 watt range. Mechanical ratings haven't seen the same level of improvements (though they have improved a lot) and where the original would have a 150 watt RMS, 300 watt program rating the new rating may be closer to 600/1000 AND if not high passed could be 600/600. The manufacturers have for the most part kept the program rating as 2x the continuous rating but have in general seen a higher failure rate when powered that high (I'm talking about the LF sections here). Then, the marketing folks got involved and with the bigger is better sales philosophy, the peak rating got a following. The problem is that in many cases the manufacturers saw the the peak power rating of a sine wave was exactly 2x the RMS value, so a 100 watt "RMS" signal is identical to a 200 watt "PEAK" signal. It's true and honest but in a misleading sort of way. So if they now say you can power with the program rating of 100 watts, that means exactly the same thing as 200 watts PEAK which is what a 100 watt RMS amplifier will deliver. I went into a pretty detailed discussion on a previous thread about doing as the manufacturers do when powering their speakers themselves in the powered versions. In general, they stick around 1x and 1.5x the "RMS" or continuous ratings of their passive offerings. This can be modified when time sensitive limiting and time integrating thermal tracking of the load/program profile is used (the more expensive models) but it's a good look into where the manufacturers are doing as I suggest as well in spite of their advertising. They pretty much all do it this way, including the products I designed. As far as being conservative, hell yes I'm conservative. I make my money with products that last and last and do not fail. With the sound company, we have thousands of shows ove many years without failures and I like it that way, so do the clients. When designing products for my "day job", I am also conservative since few customers look kindly upon gear that fails either. When designing installations as a consultant, I am conservative here as well. Neither myself or my client needs to deal with failures which always seem to happen at the worst possible time. The IEC and AES speaker ratings are valid as well, but note the bandwidth limitations and power bandwidth ratios that may not reflect the real world all that well. Note also that the lifetime of the test (unless there was a revision)does not call for the speaker to meet the factory TS parameters, it must continue to make noise. IIRC, there was a suggestion that the test duration be 200 hours, but most manufacturers truncate this greatly. A lab test is not terribly reflective on the real world. My suggestions take this into account and may be seen as conservative by some. Here's a few voice coils that have failed real world testing conditions.

 

 

So Andy all those drivers on your bench were they over powered by to much amp or under powered by not enough amp the Enquiring forum minds wanna know:lol:

[agedhorse]

So Andy all those drivers on your bench were they over powered by to much amp or under powered by not enough amp the Enquiring forum minds wanna know:lol:

 

 

Each and every one suffered at the hands of too much power. Most were from amps too large for the speaker, a few from amps that were too small and was driven hard into clipping.

 

These are just a few of the more interesting examples out of the hundreds of speakers I have reconed. Some from intentional product destructive testing, most from users having an accident or lapse in good judgement.

[Craig Vecchione]

My point here was the first responder to the thread suggested to use smaller amplifiers then what was being used (switching from the 2450 to an 1850HD). I was saying this was bad advice and in fact I would use more, with the caveat the system be operated within reason. I drive SM15V's regularly with Crown Macro 2402 for stage monitors. This is similar power to the RMX2450. The 2402 does "clip" from time to time without limiting and an HP filter set for 95hz. With limiters no clipping, but limiting does have an effect on dynamics. I recently switched to a Macro 3600 and have not had any problems, better dynamics and clarity and I am sure less power compression. Limiters also create higher RMS values while limiting amplifier input levels. I was gonna get into the fact that there is no RMS rating for this loudspeaker from the manufacturer, and getting into the differences between AES, IEC, Program and Peak, but I felt this type of detail might be outside the scope of the original posters needs. I was avoiding :blah: Boy ... you guys are quick to jump on someone with a different opinion.

 

We're quick to jump on the underpowering issue.

 

We agree on a lot of the issues, but your wording was easily misconstrued. If I wasn't getting your drift, it's a fair bet that others won't either. Making sure our posts are clear and to the point is an important issue, since we're all bascially just trying to help folks.

[t_guns]

Rhis might be the dumb question of the day, but what's wrong with running the power amps off of the Furman?

Sorry, I am still new to this,

[agedhorse]

Most models are breakered at 15 amps, and the power switch can't handle the inrush current switching on all amps at once. The other problkem if it's one of the AR series is that the voltage regulating tap changer can hunt and cause issues with the amplifier than can be damaging since the amp is a heavily dynamic load.

[t_guns]

I am running 2 QSC RMX2450 amps at 4ohms. Any suggestions on how to protect them? I did some searches here, but nothing is coming up.

[agedhorse]

They are well protected by themselves, the Furman does absolutely nothing for them. Forget the whole concept of protection... it's marketing bull{censored} for that type of power amp. Their's more money being made selling power strips than powwer amps.