Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Corey Scogin]

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"

[Ivan Beaver]

  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.

[Brad Weber]

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.

[Chuck Simon]

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?

[John Roberts {JR}]

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

[Randall Hyde]

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

[Ian Appleby]

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.

[Steve Edwards]

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.

[Marlow Wilson]

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!

[John Roberts {JR}]

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

 

[ProSoundWeb Community]