PK Sound CX800: 95% efficient??
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 19th March 2012, 09:00 AM #11 CRESCENDO   diyAudio Member   Join Date: Dec 2009 Location: California "An amplifier may have 90% efficiency, but a speaker may not." Ah, that makes more sense "What about power compression?" I know this needs to be factored in for real world numbers. I assumed they posted "calculated" numbers, but still felt them to be a little....'fluffed'....or too good to be true. "Did you know that a degree in marketing allows you to change the laws of physics by a factor of 10:1 to your advantage?" Lol, I don't know wether to laugh or to go get a degree in physics! "The x-max is at best a P-P value." Also makes much more sense! Thanks for your investigation tactics. Is there a formula(s) to figure out the maximum efficiency at 30hz being on the order of 96dB/W/1M from a net vol of ~14cu ft?
 19th March 2012, 11:05 AM #12 djk diyAudio Member     Join Date: Feb 2001 Location: USA "Is there a formula(s) to figure out the maximum efficiency at 30hz being on the order of 96dB/W/1M from a net vol of ~14cu ft?" Simple. Use the base figures in post #2 (after DB Keele) for 2nd, 4th, or 6th order. Find the ratio of the cabinet sizes. Take the log of that, and the x10, the answer is in dB difference. 14/2=7 7log=0.845 x10=8.45dB ************************************************** ********* Double/half the box size = 3dB. 2log=0.301 x10=3dB ************************************************** ********** One octave, dropping from 40hz to 20hz = 8x volume (for the same efficiency)!!! 87.56dB + 8.45dB = 96.01dB __________________ Candidates for the Darwin Award should not read this author. Last edited by djk; 19th March 2012 at 11:18 AM.
 19th March 2012, 11:58 AM #13 CRESCENDO   diyAudio Member   Join Date: Dec 2009 Location: California Simple is nice. Awesome. Thank you. Another question for the book o' basics (since it seems too many manufacturers have different approaches): what's the proper way to calculate/determine the spec: +/- 3dB? Using hornresp, bassbox, or any freq resp plot.
epa
diyAudio Member

Join Date: Apr 2010
Location: amsterdam
Quote:
 Originally Posted by djk http://www.eighteensound.it/renderPdf.aspx?pid=288 You run the numbers and see if I am correct.
sorry missed that.

btw the 9000 models easyer in a th too.+ a tad "cheaper"
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 19th March 2012, 10:18 PM #15 CRESCENDO   diyAudio Member   Join Date: Dec 2009 Location: California Has it been determined whether the low corner drops with BR and/or BP designs, or not? Last I read, most said, "no" regarding tapped horns, but there were still discrepancies.
 20th March 2012, 08:35 AM #16 epa   diyAudio Member   Join Date: Apr 2010 Location: amsterdam the low corner doesnt drop,just the directivety changes(depending on how you place the subs) only in flh the low corner drops becuase of the extended horn buble in front of the horn. in th the lenght of the driver to mouth section grows a bit with the mouths coupling,resulting in a minor change in the th system. __________________ one good thing about music ,when it hit you feel no pain. so hit me with music. hr driver db
 27th March 2012, 12:22 AM #17 Jeremy Bridge   diyAudio Member   Join Date: Mar 2012 Hey everyone, glad to hear some chit chat about our new subwoofers they have been working out really great for us =] Thought I would drop by and try to answer some questions. #1 Obviously the enclosure is not 95% efficient (I wish) but the amplifier is Class D and capable of that efficiency. That efficiency does drop as output and heat increase, such is life. #2 No where does it say the SPL measurement was taken at 30hz or free field, it does say that is how the frequency repsonse was measured. The cabinet was measured ground plane as is typical with most subwoofer measurements in our industry. If you look around you will see this figure is well within what many manufacturers are showing. Meyer HP700 = 139db. http://www.meyersound.com/pdf/products/concert_series/700-hp_ds.pdf It's funny because I had a long chat with some people from Meyer at the Pro Light & Sound in Frankfurt last week about spec sheets and how they are interpreted by our industry. In fact with thier new 1100-LFC they say they will not be releasing specs and posts like this are the prime reason. They full believe, as do I, that to evaluate a product you need to hear it and use it. Then you can make up your mind for yourself. If you love our product, great, if you like something else that's cool too there are many great companies in our industry =] Jeremy Bridge P.Eng. PK Sound
 27th March 2012, 10:55 AM #18 djk diyAudio Member     Join Date: Feb 2001 Location: USA The bovine excrement is getting hip deep. From the data sheet: the response was FREE FIELD RESPONSE Publish 100W/10M 2Pi data with no processing. __________________ Candidates for the Darwin Award should not read this author.
 27th March 2012, 03:34 PM #19 tb46   diyAudio Member   Join Date: Jan 2006 Location: Texas Hi Jeremy Bridge, Post #17: "...95% efficient (I wish) but the amplifier is Class D and capable of that efficiency. That efficiency does drop as output and heat increase..." I realize the difficulties coming from advertising your products in the real world, but it would be nice if you could post a few graphs, e.g.: efficiency v. power out, or, efficiency at different power levels v. frequency, and the usual: THD+N V. power out, power out v. frequency. As to SPL measurements, I like the Danley Sound Labs method of 100W/10m/2Pi too. That should be the industry standard for PA purposes, additionally an actual maximum long term SPL would be nice. :-) Regards, __________________ Oliver
NEO Dan
diyAudio Member

Join Date: Jun 2008
Location: N.E. Ohio
Quote:
 Originally Posted by tb46 As to SPL measurements, I like the Danley Sound Labs method of 100W/10m/2Pi too. That should be the industry standard for PA purposes, additionally an actual maximum long term SPL would be nice. :-) Regards,
DSL actually publishes 28.3v/10m/GP, regardless of the nominal impedance of the system.
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Dan

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