Anyone heard of/seen PK Sound's CX800 high powered subwoofer? Some popular dubstep/edm artists (Caspa, Bassnectar, etc) choose this sound to tour with for low end reinforcement. PK claims 139 dB peak output (133 dB continuous) and +/- 3dB from 28Hz - 150Hz. 2500W and up to 95% efficiency. Dual 18" neo drivers w/28mm xmax.
CX800
Thoughts?
CX800
Thoughts?
An amplifier may have 90% efficiency, but a speaker may not.
The most efficient woofer that I know of is the JBL 2220 at 8.7%, and it has NO BASS.
In general, the less efficient a driver is, the more maximum output it will have in the bass.
Their claims look like total BS, and I know an independent lab could not duplicate them.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
The net cabinet volume here is less than 14 cu ft, so the maximum efficiency at 30hz will be on the order of 96dB/W/1M. 96dB + 34dBW (2.5KW) is 130dB.
Where did the other 9dB go?
What about power compression?
If it is a 6th order vented design the mid-band output could be 4dB higher, but the bottom 1/3 octave will be 2dB less (assuming the power output is limited by power rather than excursion.
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?
That seems to be in effect here.
PS
The x-max is at best a P-P value.
The most efficient woofer that I know of is the JBL 2220 at 8.7%, and it has NO BASS.
In general, the less efficient a driver is, the more maximum output it will have in the bass.
Their claims look like total BS, and I know an independent lab could not duplicate them.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
The net cabinet volume here is less than 14 cu ft, so the maximum efficiency at 30hz will be on the order of 96dB/W/1M. 96dB + 34dBW (2.5KW) is 130dB.
Where did the other 9dB go?
What about power compression?
If it is a 6th order vented design the mid-band output could be 4dB higher, but the bottom 1/3 octave will be 2dB less (assuming the power output is limited by power rather than excursion.
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?
That seems to be in effect here.
PS
The x-max is at best a P-P value.
"they didn't say how the box was loaded to get that peak SPL figure"
Well they did state that the response was FREE FIELD RESPONSE, which I would assume to mean 4Pi (flown), but they should state that they actually meant on the floor, in the corner (0.5Pi), if that is what they meant.
Calculating the No=4.12% from T/S parameters comes up with 98dB/W for the pair of drivers, but the box size is a little on the small side.
"whats wrong with the 9600? "
Nothing , other that the Qts is a bit low for a vented box.
Max efficiency, minimum size, and max bass extension comes with a Qts=0.312
Well they did state that the response was FREE FIELD RESPONSE, which I would assume to mean 4Pi (flown), but they should state that they actually meant on the floor, in the corner (0.5Pi), if that is what they meant.
Calculating the No=4.12% from T/S parameters comes up with 98dB/W for the pair of drivers, but the box size is a little on the small side.
"whats wrong with the 9600? "
Nothing , other that the Qts is a bit low for a vented box.
Max efficiency, minimum size, and max bass extension comes with a Qts=0.312
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"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?
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?
"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
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
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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.
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.
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
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
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,
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,
DSL actually publishes 28.3v/10m/GP, regardless of the nominal impedance of the system.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,
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