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[Paul Dershem]

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.

[Brad Weber]

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, 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.

[Chuck Simon]

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.

[John Roberts {JR}]

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

[Tim McCulloch]

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.

[Ivan Beaver]

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.

[Chuck Simon]

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.

[John Roberts {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.

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.     

[Brian Ehlers]

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.

[Scott Bolt]

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.

[ProSoundWeb Community]