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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Corey Scogin on July 22, 2011, 04:10:45 AM
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This is a bit of a rant but I thought someone may have an answer for me.
Background: I own an EV QRx system consisting of 4x 115's and 2x 218's. I have always used a set of the original Mackie SRM450's for monitors. These SRM450's have been used as mains for smaller events for the past few years. Recently, I noticed the good price point and attractive appearance of many of the new powered 12's so I became interested in swapping my SRM450's for something prettier (yes, it matters a little) and maybe something better. In my short list was the QSC K12, JBL PRX612M, Yamaha DSR112, and the EV ELX112P.
When looking at the specs of these speakers, I was impressed, though doubtful, of their output claims (131, 134, 134, 132 respectively). The EV speakers come in a passive version as well so I thought I'd manually calculate the SPL of the passive box just to see how the numbers work out. Here's what I got:
EV ELX112
Sensitivity: 94db
Peak power handling: 1000W
Peak output: 10*log(1000)+94 = 124
Someone please tell me how they claim 132db output from this enclosure?
Are they really using the peak sensitivity value, not the averaged? Thanks EV for letting me know that my speaker will produce 132db at some random frequency, that's useful. These specs begin to mean less and less as time goes on.
If you run this same calculation on the QRx specs, you get the right answer (ex QRx115: 10*log(1600)+98=130 just like the spec sheet says)
Maybe I answered my own question above. Too bad anechoic chambers are expensive, else I'd start a business testing these speakers for the good of us consumers.
To be fair, the manufacturers referenced other than EV note how the peak db value was obtained:
QSC: "theoretical calculations based upon transducer sensitivity and peak available amplifier power"
JBL: "Maximum Peak output measured with IEC pink noise at 1 meter in front of speaker baffle under free space conditions. Measurement instrument set to peak hold. Speaker muted and released at full power, recording maximum peak level."
Yamaha: "Measured maximum SPL (peak) IEC noise @ 1m"
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Thanks XYZ for letting me know that my speaker will produce 132db at some random frequency, that's useful. These specs begin to mean less and less as time goes on.
There in lies one of the problems when all you have is an SPL spec number. There are quite a few cabinets that can get pretty loud over a very limited freq range.
The rest of the response can't keep up with that very sensitive area. In reality you would have to pull down that "hotspot" in order to get the cabinet to sound correct/good. And when you do, the max output level will drop-because the rest of the cabinet can't keep up with it.
A single number very often fails to tell the whole story and give a false impression on the cabinets real capabilities.
Of course if all you are interested in is some random peak value that occurs for a very limited time and not reflective of long term actual SPL- then you can get all sorts of "odd" numbers that don't really mean anything-except for a "peak SPL" type of number.
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Sounds like the common situation of being presented a number but not what it represents. Are the sensitivity and maximum output values the overall level with some noise source? The maximum, average or minimum over the stated nominal frequency response? The peak at any frequency even if outside that response? If there is a frequency response chart, especially one showing the 1W/1m response, then you may get some idea of what the single number ratings actually represent but otherwise that could range widely. Similar with patterns, I've seen nominal pattern specs that when you look at the polars or directivity information you find that those nominal numbers are of negligible relevance.
Back to the original point, the DSP, especially aspects such as limiting, in some powered boxes is much more complex than many people think and powered speakers are able to use such advanced internal processing to maximize the performance possible.
Also remember that some values involved are calculated and/or based on specific test conditions, for example the peak power handling in your example is likely calculated based upon the rated continuous power handling measured with a standard noise source and the crest factor of that standard noise source. It may be quite possible to momentarily get a more limited bandwidth output of much greater peak level from that speaker.
FWIW, consider that it is Ron Sauro (NWAA) and Pat Brown (ETC) that perform at least some of the testing for many speaker manufacturers. And while they can certainly go beyond the existing Standards, they also must work with the existing accepted Standards for both the test procedures and reporting of the data. Adding to that, in the end they cannot control what is or is not published by the manufacturer, only what they will stand behind.
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It seems that manufacturers don't even use consistent standards when testing their own products. For example:
JBL PRX618S-XLF 133 dB SPL 1000 watts
JBL VRX918SP 126 dB SPL 1500 watts
Both cabs use the same driver, but somehow the PRX produces 7 more dB with less power? The PRX does use a larger cab, but really?
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This is one of those classic it depends.. Peak SPL just like peak power needs qualification. SPL also needs much qualification wrt how it is measured (on axis, across polar patterns, etc).
While there is a lot of room for variation in how it is specified, I am encouraged by SPL being used as a metric instead of the old and silly watts rating. I've long complained about vacuum cleaner current draw type ratings.
It will take a while to educate consumer about how to read and understand SPL readings, but its about time we got started.
One step forward...
JR
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It seems that manufacturers don't even use consistent standards when testing their own products. For example:
JBL PRX618S-XLF 133 dB SPL 1000 watts
JBL VRX918SP 126 dB SPL 1500 watts
Both cabs use the same driver, but somehow the PRX produces 7 more dB with less power? The PRX does use a larger cab, but really?
Well, perhaps the VRX918sp is considerably less efficient than the PRX 618s? E.g., the driver in the 618s might have 99 dB SPL @ 1w/1m while the VRX 918sp has 90 dB SPL @ 1w/1m. I couldn't find the sensitivity values, so your guess is as good as mine (and I'd hope the 918 is more efficient than that). It is quite possible that the VRX 918sp cabinet is EQ'd considerably differently from the 618 (to flatten it out) and that might be responsible for the drop in efficiency.
Cheers,
Randy Hyde
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Well, perhaps the VRX918sp is considerably less efficient than the PRX 618s? E.g., the driver in the 618s might have 99 dB SPL @ 1w/1m while the VRX 918sp has 90 dB SPL @ 1w/1m. I couldn't find the sensitivity values, so your guess is as good as mine (and I'd hope the 918 is more efficient than that). It is quite possible that the VRX 918sp cabinet is EQ'd considerably differently from the 618 (to flatten it out) and that might be responsible for the drop in efficiency.
Cheers,
Randy Hyde
Well, perhaps the VRX918sp is considerably less efficient than the PRX 618s? E.g., the driver in the 618s might have 99 dB SPL @ 1w/1m while the VRX 918sp has 90 dB SPL @ 1w/1m. I couldn't find the sensitivity values, so your guess is as good as mine (and I'd hope the 918 is more efficient than that). It is quite possible that the VRX 918sp cabinet is EQ'd considerably differently from the 618 (to flatten it out) and that might be responsible for the drop in efficiency.
Cheers,
Randy Hyde
I have a feeling EV is just playing the same game as other manufactures. If there gonna put out specs brought out by those calcs... then why not play there game. Old EV speakers seem to be very true to there specs.
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The difference in the spec's for the JBL enclosure could also be a result in the differences of useable frequency response in the two enclosures along with issues of amplification, application, and sensistivity. Most of the big company's try to play it pretty straight IMO. I think the spec game was brought to the forefront in small format PA's by company's like Mackie, PV and Carvin. This was done to make buyers believe their products were more competitive than they really are. My favorite being the Mackie 32 channel mixer which is actually a 24 channel mixer W/ 4-stereo channels.
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Well, perhaps the VRX918sp is considerably less efficient than the PRX 618s? E.g., the driver in the 618s might have 99 dB SPL @ 1w/1m while the VRX 918sp has 90 dB SPL @ 1w/1m. I couldn't find the sensitivity values, so your guess is as good as mine (and I'd hope the 918 is more efficient than that). It is quite possible that the VRX 918sp cabinet is EQ'd considerably differently from the 618 (to flatten it out) and that might be responsible for the drop in efficiency.
Cheers,
Randy Hyde
One of those speakers was designed to be used in the air and the other on the ground. Full space and half-space measurements were, I ASSume, used respectively.
*EDIT*
http://www.jblpro.com/catalog/support/getfile.aspx?docid=581&doctype=3
From the above link - footnote for the maximum peak output of the VRX sub: "Measured with IEC shaped noise in free field conditions."
Sometimes you just need to RTFM more carefully!
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Most of the big company's try to play it pretty straight IMO. I think the spec game was brought to the forefront in small format PA's by company's like Mackie, PV and Carvin. This was done to make buyers believe their products were more competitive than they really are. My favorite being the Mackie 32 channel mixer which is actually a 24 channel mixer W/ 4-stereo channels.
I used to call that "Mackie math", but I wouldn't conflate channel numbering inflation with loudspeaker spec imprecision.
As much fun as it is to blame this on the brands competing in the value segment, IMO the customers are complicit by rewarding over simplified merchandising with sales.
Perhaps this would be a good thread for some smoking gun examples of specs abuse from Mackie, Peavey, Carvin, or any other scumbag company (or are those the only three?).
The JBL example is a classic case of the customer assuming box performance will mirror driver performance simply. This is just more evidence why SPL specs, that are the actual output, are worth pursuing.
I am not optimistic that the learning curve will be any easier than for power specs, which haven't been completely mastered yet.
JR
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I used to call that "Mackie math", but I wouldn't conflate channel numbering inflation with loudspeaker spec imprecision.
As much fun as it is to blame this on the brands competing in the value segment, IMO the customers are complicit by rewarding over simplified merchandising with sales.
Perhaps this would be a good thread for some smoking gun examples of specs abuse from Mackie, Peavey, Carvin, or any other scumbag company (or are those the only three?).
The JBL example is a classic case of the customer assuming box performance will mirror driver performance simply. This is just more evidence why SPL specs, that are the actual output, are worth pursuing.
I am not optimistic that the learning curve will be any easier than for power specs, which haven't been completely mastered yet.
JR
I was just looking at the TH Mini specs on the Danley website, and although Danley provides "Architect/Engineers Specs" that are more modest and realistic than the more prominently displayed numbers used to encourage sales, you've gotta make an effort to unearth the "real" numbers. One could argue that the "architect/Engineers Specs" are akin to disclosure. But, I didn't see anything saying, "this is how we made these calulations." The blue sky numbers are the ones that are featured prominently.
Puffing the numbers by using peak values when making sales claims doesn't seem to be limited to MI gear makers.
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I was just looking at the TH Mini specs on the Danley website, and although Danley provides "Architect/Engineers Specs" that are more modest and realistic than the more prominently displayed numbers used to encourage sales, you've gotta make an effort to unearth the "real" numbers. One could argue that the "architect/Engineers Specs" are akin to disclosure. But, I didn't see anything saying, "this is how we made these calulations." The blue sky numbers are the ones that are featured prominently.
Puffing the numbers by using peak values when making sales claims doesn't seem to be limited to MI gear makers.
I'm trying to follow your point as the A&E specs for the TH-Mini are the same as the summary specs while if you look on the product data page from which you cut the summary specs, http://www.danleysoundlabs.com/pdf/TH%20MINI%20Spec%20Sheet.PDF (http://www.danleysoundlabs.com/pdf/TH%20MINI%20Spec%20Sheet.PDF), there is additional information provided including a 2.83V (1W into 8 Ohms) frequency and phase response graph that supports the frequency response and sensitivity values in the summary and an impedance chart that reflects the nominal impedance. They don't identify all the test conditions but I don't see anything in the specs that disagrees with the supporting information, so I'm not clear what you feel is inaccurately presented.
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The JBL example is a classic case of the customer assuming box performance will mirror driver performance simply. This is just more evidence why SPL specs, that are the actual output, are worth pursuing.
Would you please explain that statement? I think it's obvious that a driver's performance will depend on the cabinet, but do you think that is the reason for the stated 7dB difference between the two JBL examples? I try not to assume anything when it comes to stated specs and I am interested in your opinion.
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The JBL example is a classic case of the customer assuming box performance will mirror driver performance simply. This is just more evidence why SPL specs, that are the actual output, are worth pursuing.
Would you please explain that statement? I think it's obvious that a driver's performance will depend on the cabinet, but do you think that is the reason for the stated 7dB difference between the two JBL examples? I try not to assume anything when it comes to stated specs and I am interested in your opinion.
I am not a speaker expert but since you asked for my opinion, looking at the diver's specs is like trying to predict how fast a car will go around a track based on which motor it has in it. Yes the motor will define how well it can work, but only as a starting point, then you must account for the weight of the car, the tires, gear ratio (horn?), etc.
A driver used in a sub or bandpass box will be less conflicted than in a full range design with some additional losses associated with passive crossovers, but there will still be a range of output performance issues imposed by the general box design approach and internal volume.
I have no idea why the two JBL numbers are so far off and whether either one is correct, so I won't speculate on that.
I believe real SPL numbers are one level closer to reality than driver numbers because there are less variables left that could alter the result.
Use whatever tools work for you, I jumped on this as a convenient example, my apologies if it wasn't perfect fit.
JR
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Well, perhaps the VRX918sp is considerably less efficient than the PRX 618s? E.g., the driver in the 618s might have 99 dB SPL @ 1w/1m while the VRX 918sp has 90 dB SPL @ 1w/1m. I couldn't find the sensitivity values, so your guess is as good as mine (and I'd hope the 918 is more efficient than that). It is quite possible that the VRX 918sp cabinet is EQ'd considerably differently from the 618 (to flatten it out) and that might be responsible for the drop in efficiency.
Cheers,
Randy Hyde
One of those speakers was designed to be used in the air and the other on the ground. Full space and half-space measurements were, I ASSume, used respectively.
*EDIT*
http://www.jblpro.com/catalog/support/getfile.aspx?docid=581&doctype=3
From the above link - footnote for the maximum peak output of the VRX sub: "Measured with IEC shaped noise in free field conditions."
Sometimes you just need to RTFM more carefully!
This is the correct answer. The PRX is measured in half-space, the VRX in whole space. That now leaves us with 1dB, which might be accounted for in the box tuning or DSP.
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I was just looking at the TH Mini specs on the Danley website, and although Danley provides "Architect/Engineers Specs" that are more modest and realistic than the more prominently displayed numbers used to encourage sales, you've gotta make an effort to unearth the "real" numbers. One could argue that the "architect/Engineers Specs" are akin to disclosure. But, I didn't see anything saying, "this is how we made these calulations." The blue sky numbers are the ones that are featured prominently.
Puffing the numbers by using peak values when making sales claims doesn't seem to be limited to MI gear makers.
There is only so much room on a spec sheet for data. So we try to keep it down to the important numbers-that the user could use to determine if a product is suited for a particular job or not.
But anyway-here is the way the numbers for the SUB products are determined. Full range products are different. We try very hard to make sure the product numbers will actually stand up when you measure the product in your back yard-assuming you have calibrated measurement gear.
We measure at a distance of 10M outdoors. If we measured at 1M, the spec numbers would be higher-but would not reflect how the product would perform when distances are calculated in. That is a loss of 20 over distance.
We also measure with the cabinet and the mic in ground plane positions. This reduces any possible ground bounce. 1/2 space (ground plane) is the position that subs are most often used in-so it makes sense to measure them that way.
We send a slow swept sine wave (TEF-typically with a resolution of 2Hz-the finest you can get on it) at a level of 28.28V. This is a 20 dB rise over 2.83V.
The -20dB distance and +20 voltage will cancel each other out-so you end up with a 2.93V @1M equivilent.
The response shown is the actual measurement graph-not doctored up or redrawn by the "marketing dept".
The numbers on the spec sheets come directly from me.
We also have other parameters independtly measured (such as EASE-CLF etc). I am not 100% sure how those measurements are done-but the person doing it (Pat Brown) is very well respected in the industry and he tries very hard to provide real-useful-meaningful data.
So any questions in that regard should be directed to him.
I hope that helps clear that up. If not-let me know.
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The JBL example is a classic case of the customer assuming box performance will mirror driver performance simply. This is just more evidence why SPL specs, that are the actual output, are worth pursuing.
Would you please explain that statement? I think it's obvious that a driver's performance will depend on the cabinet, but do you think that is the reason for the stated 7dB difference between the two JBL examples? I try not to assume anything when it comes to stated specs and I am interested in your opinion.
I am not a speaker expert but since you asked for my opinion, looking at the diver's specs is like trying to predict how fast a car will go around a track based on which motor it has in it. Yes the motor will define how well it can work, but only as a starting point, then you must account for the weight of the car, the tires, gear ratio (horn?), etc.
A driver used in a sub or bandpass box will be less conflicted than in a full range design with some additional losses associated with passive crossovers, but there will still be a range of output performance issues imposed by the general box design approach and internal volume.
I have no idea why the two JBL numbers are so far off and whether either one is correct, so I won't speculate on that.
I believe real SPL numbers are one level closer to reality than driver numbers because there are less variables left that could alter the result.
Use whatever tools work for you, I jumped on this as a convenient example, my apologies if it wasn't perfect fit.
JR
Certainly no apologies needed, I'm just trying to understand this stuff and I appreciate your willingness to share your knowledge.
The "half-space full-space" info as explained by Randall and Tim makes sense to me and if true, kudos to JBL for making an effort to show specs that are based on the reality of how the product will be used.
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Certainly no apologies needed, I'm just trying to understand this stuff and I appreciate your willingness to share your knowledge.
The "half-space full-space" info as explained by Randall and Tim makes sense to me and if true, kudos to JBL for making an effort to show specs that are based on the reality of how the product will be used.
Like I said I am not the speaker expert in this community, but I was irritated by the cheap easy shot, at one company I worked at for 15 years who to the best of my knowledge did not knowingly obfuscate specifications.
I recall the frustration from the transducer product manager trying to communicate real benefits (like efficiency) to a consumer fixated on power handling. Trying to get consumers to compare SPL, was a waste of energy, and generally irritated them.
While people like to accuse the marketers of driving the hyperbole, it is really the consumer who drives the direction by what they buy, and smart merchandisers just try to give them "more" of what they demonstrate that they want. When consumers don't buy efficiency, but instead buy power handling, you better respond with more power handling (efficiency be damned) or give up that market. Perhaps Peavey was more whip sawed by uninformed consumer perceptions, since they never advertised enough to change any minds with educational campaigns. As most will tell you, if you have to try to change a customer's mind, you have already lost the sale. The customer is always right, and it's easier to sell him what he is asking for.
I find it somewhat ironic that Danley, was singled out as an offender in response to my query. ASSuming this wasn't a joke (I don't recall seeing any emoticons). Danley is not only an exemplary citizen wrt specification, they are pretty much above reproach (holier than the proverbial Ceasar's wife) using 3rd party test agencies for unimpeachable data.
From my experience, I believe there is less cheating and intentional misinformation than people like to suggest and more of an issue with the general inability of most consumers to grasp the significance of the details and qualifications associated with specifications. The knee-JERK reaction is to fixate on the box with the bigger top line number without bothering to inspect the fine print.
This isn't even anybody's fault... it is a complex subject and sometimes even the experts disagree on the fine points. I just wish there was a little less ASSuming that all the companies are cheating or trying to, and more effort spent on trying to understand the specs.
JR
PS: All that said, it is not in the best interest of companies selling inferior product to make comparison easy, but I expect most will be honest when asked direct questions.
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The "half-space full-space" info as explained by Randall and Tim makes sense to me and if true, kudos to JBL for making an effort to show specs that are based on the reality of how the product will be used.
I haven't pulled up the datasheets for the two speakers in question, but JBL is usually pretty good at explicitly identifying "half space" or "full space" on thier datasheets, even for their MI gear.
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I agree with the other posters that stated that SPL is a better measure than watts.
There are still a few ways to fudge the SPL number; however, at least it is a better indication of performance than the power rating of the amps inside the box ::)
That being said, there is more to a speaker than SPL..... like the obvious ..... how does it sound ;) .... and the not so obvious .... how does it sound at different output levels.
When I was auditioning 12" powered tops, I made sure to push them, listen for harshness and clipping, and clarity. All the speakers mentioned by the OP are capable of getting very loud; loud enough to play a club of ~500 when used over subs IMHO. Not all of them sound as good when pushed as they do at more moderate levels.
The JBL runs pretty hot, which bothers me as an engineer, but I haven't heard of any shutdown problems with the 12's (I did hear some noise about the subs and 2x15's though). The QSC K12 doesn't like being pushed too hard (gets a bit harsh). The JBL and Yamaha go clear to limit and sound good doing it. The Yamaha DSR112 stays relatively cool, but is heavier than the JBL.
They all sounded pretty good .... not JBL SRX good, but pretty good.
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That being said, there is more to a speaker than SPL..... like the obvious ..... how does it sound ;) .... and the not so obvious .... how does it sound at different output levels.
Sound quality is subjective and thus not a practical basis for a standardized test, however it has been suggested by several people to base maximum power, or actually maximum voltage, ratings for passive speakers and maximum output for powered speakers on a speaker exhibiting any readily audible variation, say maybe a 3dB variation, in response at any frequency. Run a speaker at a level for a period of time while continually looking at the response, then step up the level do that again, repeat until you see any significant variation in response. The highest level obtained without exceeding the allowed frequency response deviation or any failure is then reported as the maximum rating.
A practical challenge in getting such an approach adopted is that the numbers obtained this way may be considerably lower for many speakers and thus they could appear to compare poorly to speakers tested using other approaches. Similarly, it would be difficult to compare ratings from this test approach to that of others.
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I agree that it is difficult to determine what a "good" sounding box sounds like. It has been my experience that the current batch of MI powered speakers from the various OEM's are in the "good enough" league..... that is to say that if you play for small to medium venues, the audience would not be able to tell the difference between the QSC KW122's over subs and Meyer UPA1's over subs...... even if most of us here could.
The MI speakers I am speaking of all fall in the range of 1K to 2K for a pair (of tops).
In contrast, placing a pair of Behringer EUROLIVE's on top would almost guarantee that the audience would think that the band didn't really sound that good .... even if they were very talented.
IMHO, there is diminishing returns in FOH speakers beyond the JBL PRX class of tops. Most bands would be better off getting better vocal equipment (or a better singer ;) ) than doubling their budget on FOH speakers. An investment in IEM's for instance would make a huge improvement.